JP2008310946A - Substrate for suspension, method for producing the same, magnetic head suspension, and hard disk drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for a suspension nearly free from warpage even when its rigidity is lowered. <P>SOLUTION: The substrate 10 for the suspension comprises a metal substrate 1, an insulating layer 2 formed on the metal substrate 1, a wiring layer 3 formed on the insulating layer 2, and a cover layer 4 covering the wiring layer 3. The material of the insulating layer 2 is different from the material of the cover layer 4, and their coefficients of moisture-absorption expansion are within the range from 0×10<SP>-6</SP>/%RH to 30×10<SP>-6</SP>/%RH. The difference between the coefficients of moisture-absorption expansion of these materials is not more than 5×10<SP>-6</SP>/%RH. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

Reference to related applications

  This patent application enjoys the benefits of Japanese Patent Application No. 2007-109279, which was filed on April 18, 2007, and Japanese Patent Application No. 2007-126588, which was filed on May 11, 2007. The entire disclosure of these earlier applications is hereby incorporated by reference.

  The present invention relates to a suspension substrate used in a hard disk drive (HDD) or the like, and more particularly, to a suspension substrate with less warping even when the rigidity is reduced.

  In recent years, due to the spread of the Internet and the like, there has been a demand for an increase in the amount of information processing of personal computers and an increase in information processing speed. Accordingly, hard disk drives incorporated in personal computers (hereinafter simply referred to as HDDs) There is also a need to increase the capacity and speed of information transmission. In addition, a component called a magnetic head suspension that supports the magnetic head used in the HDD also has a signal line such as a copper wiring directly formed on a stainless steel spring from a conventional type in which a signal line such as a gold wire is connected. The so-called wireless suspension is now integrated into a wiring integrated type (flexure).

  Recently, the demand for HDDs installed in various small devices such as portable applications has increased, and along with this, disks for recording information have become smaller in size and higher in recording density. . In order to read and write data to tracks on this disk with a reduced diameter, it is necessary to rotate the disk slowly, and the relative speed (circumferential speed) of the disk to the magnetic head is low, so that Since the substrate needs to approach the disk with a weak force, it is necessary to reduce the rigidity of the suspension substrate.

As the suspension substrate, generally, a metal substrate, an insulating layer, a wiring layer, a cover layer, and the like formed in a pattern are laminated in this order. As a method for reducing the rigidity of such a suspension substrate, a method of reducing the remaining ratio of the metal substrate, which is a relatively rigid material, has been studied.
However, if the remaining ratio of the highly rigid metal substrate is reduced, there is a problem that the suspension substrate is warped.
Conventionally, the cause of warping is considered to be a difference in thermal expansion coefficient between the metal substrate and the insulating layer, and Patent Document 1 uses an insulating layer resin equivalent to the thermal expansion coefficient of the metal substrate. Thus, a method for reducing the warpage of the suspension substrate is disclosed.
However, in the suspension substrate that has been reduced in rigidity by reducing the residual ratio of the metal substrate as described above, the warp is sufficient only by reducing the difference in the thermal expansion coefficient between the metal substrate and the insulating layer resin. However, there is a problem that it is difficult to suppress.

JP 2006-248142 A

The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a suspension substrate with less warping even when the rigidity is reduced.
Another object of the present invention is to obtain a low-rigidity suspension base material with good yield.

  As a result of repeated research to solve the above problems, the present inventors have reduced the hygroscopic expansion coefficient of the insulating layer and the cover layer laminated on the metal substrate, and further have absorbed the moisture absorption of the insulating layer and the cover layer. By reducing the difference between the expansion coefficients, it was found that even when the rigidity is reduced, the warpage can be reduced, and the present invention has been completed.

That is, the present invention includes a metal substrate, an insulating layer formed on the metal substrate and made of an insulating layer forming material, a wiring layer formed on the insulating layer, and formed on the insulating layer, A cover layer made of a cover layer forming material that covers a part of the wiring layer, and the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material is 0 /% RH to 30 × 10 ⁻⁶ /% RH The suspension substrate is characterized in that it is within the range and the difference between the hygroscopic expansion coefficients of the two is within the range of 0 to 5 × 10 ⁻⁶ /% RH.
The present invention also provides a metal substrate, an insulating layer formed on the metal substrate and made of an insulating layer forming material, a wiring layer formed on the insulating layer, formed on the insulating layer, and at least the wiring A cover layer made of a cover layer forming material that covers a part of the layer, wherein the insulating layer forming material and the cover layer forming material are made of different materials, and their hygroscopic expansion coefficient is 0 /% RH to 30 in the range of ^RH × 10 -6 ^/%, still the difference in the coefficient of hygroscopic expansion of both is a suspension substrate, characterized in that in the range below 5 × 10 -6 ^{/% RH.}

According to the present invention, since the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material and the difference between the hygroscopic expansion coefficients of both are in the above range, the suspension substrate of the present invention has low rigidity. Even in this case, warpage due to moisture absorption can be reduced.
In addition, since the insulating layer forming material and the cover layer forming material are different materials, for example, when the cover layer is formed, it is easy to make the material in which the insulating layer does not dissolve. be able to.

In the present invention, the thermal expansion coefficients of the insulating layer forming material and the cover layer forming material are in the range of 15 × 10 ⁻⁶ / ° C. to 30 × 10 ⁻⁶ / ° C., and the insulating layer forming material and the cover layer The suspension substrate is characterized in that the difference in coefficient of thermal expansion between the forming materials is in the range of 10 × 10 ⁻⁶ / ° C. or less.
The thermal expansion coefficient of the insulating layer forming material and the cover layer forming material and the difference between the thermal expansion coefficients of both are within the above range, so that even when the rigidity is reduced, the warpage due to temperature change is small. It can be.

The present invention is the suspension substrate, wherein the insulating layer forming material and the cover layer forming material are both or one of non-photosensitive materials.
Since the insulating layer forming material and the cover layer forming material are non-photosensitive materials, it is not necessary to add a photosensitizing component, so that the adjustment of physical properties such as the hygroscopic expansion coefficient and the thermal expansion coefficient described above is easy. Can be.
In this case, the non-photosensitive material refers to a material that cannot be patterned by the action of light alone, and the liquid, gas, or plasma passes through an opening provided by a mask formed of metal or resist. It is a material that needs to form a pattern by a method such as removing unnecessary portions by a method, or applying a pattern shape in advance by a method such as ink jet or screen printing.
More generally, it refers to a material that forms a pattern without containing a photosensitive component.
The use of non-photosensitive materials complicates the pattern formation process, but there is a merit that a wider range of materials can be selected by applying a purer material that does not contain a photosensitive component, which is necessary for the present invention. Thus, it is possible to apply a material having the characteristics of low hygroscopic expansion and low linear thermal expansion.

The present invention provides a metal substrate, an insulating layer formed on the metal substrate and made of an insulating layer forming material, a wiring layer formed on the insulating layer, and formed on the insulating layer, at least the wiring layer A cover layer made of a cover layer forming material, and the insulating layer forming material and the cover layer forming material are made of the same non-photosensitive material, and their hygroscopic expansion coefficient is 0 /% RH. It is a substrate for suspension characterized by being in a range of ˜30 × 10 ⁻⁶ /% RH.

  According to the present invention, since the insulating layer forming material and the cover layer forming material are the same non-photosensitive material, and the hygroscopic expansion coefficient of both is in the above range, the hygroscopic expansion coefficient and the thermal expansion coefficient described above. Such physical property values can be easily adjusted, and even when the suspension substrate of the present invention has a low rigidity, warpage due to moisture absorption can be reduced.

The present invention is the suspension substrate, wherein the insulating layer forming material and the cover layer forming material have a thermal expansion coefficient in a range of 15 × 10 ⁻⁶ / ° C. to 30 × 10 ⁻⁶ / ° C. .

  Since the thermal expansion coefficients of the insulating layer forming material and the cover layer forming material are in the above range, even when the suspension substrate of the present invention has a low rigidity, the warpage due to temperature change may be small. it can.

（Ｒ１は４価の有機基、Ｒ２は２価の有機基、Ｒ１及びＲ２は、単一構造でもよく２種以上の組み合わせでもよい。ｎは１以上の自然数） In the present invention, the insulating layer forming material and the cover layer forming material preferably contain a repeating unit of the following general formula from the viewpoint of preventing suspension warpage.

(R1 is a tetravalent organic group, R2 is a divalent organic group, R1 and R2 may be a single structure or a combination of two or more types, n is a natural number of 1 or more)

  In the present invention, since the insulating layer forming material and the cover layer forming material are required to have low hygroscopic expansion and low linear thermal expansion, it is preferably a polyimide represented by the above formula. Polyimide exhibits linear thermal expansion equivalent to that of metal, together with high heat resistance and insulating properties derived from its rigid skeleton. Furthermore, the hygroscopic expansion can be reduced.

  In the present invention, the insulating layer forming material and the cover layer forming material are preferably made of polyimide containing an aromatic skeleton from the viewpoint of preventing suspension warpage. Among polyimides, polyimides containing an aromatic skeleton are preferably used for this application because they are derived from their rigid and highly planar skeletons, have excellent heat resistance and insulation properties in thin films, and have a low coefficient of linear expansion. I can do it.

上記式の構造を含むと、これら剛直な骨格に由来し、低線熱膨張及び、低吸湿膨張を示す。さらには、市販で入手が容易であり、低コストであると言うメリットもある。 In the present invention, the insulating layer forming material and the cover layer forming material are preferably represented by the following formula in which 33 mol% or more of R1 represented by the above formula is represented from the viewpoint of preventing suspension warpage.

When the structure of the above formula is included, it is derived from these rigid skeletons and exhibits low linear thermal expansion and low hygroscopic expansion. Furthermore, there is an advantage that it is easily available on the market and is low cost.

（Ｒ^３は２価の有機基、酸素原子、硫黄原子、又はスルホン基であり、Ｒ^４及びＲ^５は１価の有機基、又はハロゲン原子である。）
上記式の構造を含むと、これら剛直な骨格に由来し、低線熱膨張及び、低吸湿膨張を示す。さらには、市販で入手が容易であり、低コストであると言うメリットもある。 In the present invention, the insulating layer forming material and the cover layer forming material are preferably represented by the following formula in which 33 mol% or more of R2 represented by the above formula is expressed from the viewpoint of preventing suspension warpage.

(R ³ is a divalent organic group, an oxygen atom, a sulfur atom, or a sulfone group, and R ⁴ and R ⁵ are a monovalent organic group or a halogen atom.)
When the structure of the above formula is included, it is derived from these rigid skeletons and exhibits low linear thermal expansion and low hygroscopic expansion. Furthermore, there is an advantage that it is easily available on the market and is low cost.

In the present invention, it is ensured that one of or both of the insulating layer forming material and the cover layer forming material can be developed with a basic aqueous solution, ensuring safety in the working environment and reducing process costs. From the viewpoint of
Since the basic aqueous solution can be obtained at a low cost and the waste liquid treatment cost and the equipment cost for ensuring work safety are low, production at a lower cost is possible.

The present invention includes a metal substrate, an insulating layer formed on the metal substrate, a wiring layer formed on the insulating layer, and a cover formed on the insulating layer and covering at least a part of the wiring layer. A method for manufacturing a suspension substrate, comprising: an insulating layer forming step of forming an insulating layer made of an insulating layer forming material on the metal substrate in a pattern; and a cover layer forming material on the insulating layer. A cover layer forming step of forming a cover layer made of a pattern into a pattern, wherein the insulating layer forming material and the cover layer forming material are made of different materials, and the hygroscopic expansion coefficient of both is 0 × 10 ⁻⁶ /% RH The suspension substrate is characterized in that it is in a range of -30 × 10 ^-6 /% RH, and the difference between the hygroscopic expansion coefficients of the two is in the range of 5 × 10 ^-6 /% RH or less. Is the method.

  According to the present invention, the insulating layer and the cover layer are formed using a material in which the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material and the difference between the hygroscopic expansion coefficients of both are within the above range. By forming the suspension substrate, even if the suspension substrate manufactured by the manufacturing method of the present invention has low rigidity, warpage due to moisture absorption can be reduced.

In the present invention, the cover layer forming step is formed on the insulating layer on the non-photosensitive cover layer forming layer made of a non-photosensitive cover layer forming material and on the non-photosensitive cover layer forming layer. A step of arranging a laminate including a photoresist layer made of a photosensitive resin, and exposing the photoresist layer of the laminate to a pattern, and simultaneously developing the exposed photoresist layer, the non-photosensitive layer And a step of forming the cover layer in a pattern by developing the conductive cover layer forming layer.
In the cover layer forming step, the photoresist layer is exposed in a pattern, and simultaneously with the development of the exposed photoresist layer, the non-photosensitive cover layer forming layer is developed. By forming it in a pattern, the number of operations required for forming the cover layer can be reduced.

The present invention is the method for manufacturing a suspension substrate, wherein the cover layer forming step includes a step of applying a liquid cover layer forming material containing the cover layer forming material on the insulating layer.
By forming the cover layer by applying a liquid cover layer forming material containing the cover layer forming material, the cover layer can be easily thinned.

  The present invention provides a laminate preparation step of preparing a laminate in which a metal substrate, an insulating layer, and a metal plating layer are arranged in this order, and a patterned resist on the surface of the metal substrate and the surface of the metal plating layer. A suspension substrate comprising: a first metal etching step of forming a jig hole in the metal substrate by forming and etching, and forming a wiring pattern layer in the metal plating layer. It is a manufacturing method.

  According to the present invention, a suspension substrate having a low rigidity can be obtained by using the above laminate. Further, in the first metal etching step, jig holes and punch holes are formed in the metal substrate, but most of the metal substrate is not etched. Therefore, the insulating layer can be etched in a state where the rigidity of the laminated body is maintained high, and deformation of the laminated body during processing can be suppressed during conveyance between the processes.

The present invention provides a cover layer forming step of forming a cover layer having a wiring pattern layer exposed opening in which a part of the surface of the wiring pattern layer is exposed in the wiring pattern layer using a cover material; An insulating layer etching step for etching the insulating layer after forming, a protective plating portion forming step for forming a protective plating portion on the surface of the wiring pattern layer exposed by the wiring pattern layer exposed opening, and the insulating layer A method of manufacturing a suspension substrate, further comprising a second metal etching step of performing an outer shape processing of the metal substrate after the etching step and the protective plating portion forming step.
A suspension substrate having a lower rigidity can be obtained.

The present invention is the method for manufacturing a suspension substrate, wherein a difference between the maximum film thickness portion and the minimum film thickness portion of the metal plating layer is 2 μm or less.
By etching the metal plating layer, a wiring pattern layer having a uniform film thickness can be obtained. When the wiring pattern layer is formed by the additive method, the thickness of the wiring pattern layer varies greatly, and it becomes difficult to obtain a pattern forming body having a desired rigidity.
The present invention is the method for manufacturing a suspension board, wherein a difference in film thickness between the maximum film thickness portion and the minimum film thickness portion on the wiring pattern layer of the cover layer is 1 μm or less.
The present invention is a method for manufacturing a suspension board, wherein a cover layer is formed using a liquid cover material in the cover layer forming step.

The present invention provides a magnetic head suspension having a suspension substrate, wherein the suspension substrate is formed on a metal substrate, an insulating layer made of an insulating layer forming material, and a wiring formed on the insulating layer. And a cover layer made of a cover layer forming material, which is formed on the insulating layer and covers at least a part of the wiring layer, and the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material is 0 /% RH~30 in the range of RH × ¹⁰ -6 /%, magnetic further difference between the hygroscopic expansion coefficient therebetween, characterized in that it is in the range of RH 0~5 × ¹⁰ -6 /% It is a head suspension.

The present invention relates to a magnetic head suspension having a suspension substrate, wherein the suspension substrate is formed on the metal substrate, an insulating layer formed of an insulating layer forming material, and a wiring formed on the insulating layer. And a cover layer made of a cover layer forming material that is formed on the insulating layer and covers at least a part of the wiring layer, and the insulating layer forming material and the cover layer forming material are made of different materials, And the hygroscopic expansion coefficient of both is in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and the difference between the two hygroscopic expansion coefficients is in the range of 5 × 10 ⁻⁶ /% RH or less. This is a magnetic head suspension characterized by the above.

The present invention provides a magnetic head suspension having a suspension substrate, wherein the suspension substrate is formed on a metal substrate, an insulating layer made of an insulating layer forming material, and a wiring formed on the insulating layer. And a cover layer made of a cover layer forming material that is formed on the insulating layer and covers at least a part of the wiring layer, and the insulating layer forming material and the cover layer forming material are the same non-photosensitive The magnetic head suspension is made of a material and has a hygroscopic expansion coefficient of both in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH.

The present invention relates to a hard disk drive having a suspension substrate, wherein the suspension substrate is a metal substrate, an insulating layer formed on the metal substrate and made of an insulating layer forming material, and a wiring layer formed on the insulating layer. And a cover layer made of a cover layer forming material that is formed on the insulating layer and covers at least a part of the wiring layer, and the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material is 0 / % RH to 30 × 10 ⁻⁶ /% RH, and the difference in the hygroscopic expansion coefficient between the two is in the range of 0 to 5 × 10 ⁻⁶ /% RH It is.

The present invention relates to a hard disk drive having a suspension substrate, wherein the suspension substrate is a metal substrate, an insulating layer formed on the metal substrate and made of an insulating layer forming material, and a wiring layer formed on the insulating layer. And a cover layer made of a cover layer forming material that is formed on the insulating layer and covers at least a part of the wiring layer, and the insulating layer forming material and the cover layer forming material are made of different materials, and The hygroscopic expansion coefficient of both is in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and the difference between the hygroscopic expansion coefficients of both is in the range of 5 × 10 ⁻⁶ /% RH or less. It is a hard disk drive characterized by being.

The present invention relates to a hard disk drive having a suspension substrate, wherein the suspension substrate is a metal substrate, an insulating layer formed on the metal substrate and made of an insulating layer forming material, and a wiring layer formed on the insulating layer. And a cover layer made of a cover layer forming material that is formed on the insulating layer and covers at least a part of the wiring layer, and the insulating layer forming material and the cover layer forming material are the same non-photosensitive material The hard disk drive is characterized in that the hygroscopic expansion coefficient of both is in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH.

  In the present invention, there is an effect that it is possible to provide a suspension substrate with less warping even when the remaining ratio of the metal substrate is reduced to reduce the rigidity.

First Embodiment The present invention relates to a suspension substrate and a method for manufacturing the same.
Hereinafter, a suspension substrate and a method for manufacturing the suspension substrate according to the first embodiment of the present invention will be described in detail.

A. Suspension Substrate The suspension substrate of the present invention includes a metal substrate, an insulating layer formed on the metal substrate and made of an insulating layer forming material, a wiring layer formed on the insulating layer, and the insulating layer. And a cover layer made of a cover layer forming material and covering at least a part of the wiring layer. Such a suspension base material is made of a material having a different insulating layer forming material and cover layer forming material, and the hygroscopic expansion coefficient of the non-photosensitive material is 0 /% RH to 30 × 10 ⁻⁶ /% RH. And the difference in the hygroscopic expansion coefficient between the two is in the range of 5 × 10 ⁻⁶ /% RH or less (first aspect), and the insulating layer forming material and the cover layer forming material are It is composed of the same non-photosensitive material, and the non-sensitive material has a hygroscopic expansion coefficient in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH (second embodiment). Can be divided. Hereinafter, the suspension substrate of the present invention will be described separately for each embodiment.

1. First Aspect First, a first aspect of the suspension substrate of the present invention will be described. The suspension substrate of this aspect is the above-described suspension substrate, wherein the insulating layer forming material and the cover layer forming material are made of the same or different materials, and the hygroscopic expansion coefficient of both is 0 /% RH to 30 × 10 ^{− 6} /% RH, and the difference between the two hygroscopic expansion coefficients is 5 × 10 ⁻⁶ /% RH or less.

Such a suspension substrate of this embodiment will be described with reference to the drawings. FIG. 1A is a schematic cross-sectional view showing an example of the suspension substrate of this embodiment. As illustrated in FIG. 1A, the suspension substrate 10 of this aspect includes a metal substrate 1, an insulating layer 2 formed on the metal substrate 1, and a wiring layer formed on the insulating layer 2. 3 and a cover layer 4 formed on the insulating layer 2 and covering at least a part of the wiring layer 3. The wiring layer 3 is covered with a protective plating layer 5. In order to reduce the rigidity of the suspension substrate 10, a part of the metal substrate 1 is removed, and the insulating layer 2 has a low rigidity region 6 in which one surface of the insulating layer 2 is not covered with the metal substrate 1. Is formed.
Further, a hard disk drive 30 is constituted by the magnetic head suspension 31 made of such a suspension substrate 10 and the magnetic head 32 held at the tip of the magnetic head suspension 31 (see FIG. 10).

Here, the insulating layer and the cover layer are formed of an insulating layer forming material and a cover layer forming material, respectively, and the insulating layer forming material and the cover layer forming material are made of the same or different materials, and both absorb moisture. A material having an expansion coefficient in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and a difference between the two hygroscopic expansion coefficients in the range of 5 × 10 ⁻⁶ /% RH or less. is there.

Here, it describes below about the measuring method of a hygroscopic expansion coefficient.
S-TMA: The temperature was fixed at 25 ° C., and the humidity was changed to 15%, 20%, and 50%. The elongation per 1% humidity was calculated from the elongations of 20% and 50% humidity, and was defined as the humidity expansion coefficient.
The calculation formula is as follows.
Humidity expansion rate [ppm% RH] = Elongation per 1% humidity / Initial length × 1000000
= Elongation amount of humidity 20-50% / 30 / initial length × 1000000
1) Sample form Sample size Width 5mm x Length 15mm (Grip + 5mm)
Thickness About 7-8μm Initial state Fully dried state 2) Measurement conditions Equipment RIGAKU S-TMA (TMA with humidity generator)
Weight 5g
Temperature 25 ° C
3) Measuring method Hold for 0.5 h or longer after the sample environment is stable at a humidity of 15% Rh and the sample length remains constant and does not change. Next, after the sample environment stabilizes at a humidity of 20% Rh, the sample length remains constant and does not change, hold for 0.5 h or longer (measure the sample length)
3. Subsequently, the environment of the sample is stabilized at a humidity of 50% Rh, the sample length remains constant and no longer changes, and then holds for 0.5 h or longer (measures the sample length)
4). 4. Calculate the difference between the value at 20% humidity and 50% humidity and 1/30 to obtain the elongation per 1% humidity. Divide the amount of elongation per 1% humidity by the initial length (15 μm) to obtain the rate of change

  According to this aspect, since the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material and the difference between the two hygroscopic expansion coefficients are within the above range, the suspension substrate of the present aspect has a low rigidity. Even in this case, warpage due to moisture absorption can be reduced.

  Here, when the insulating layer forming material and the cover layer forming material are within the range of the above-described hygroscopic expansion coefficient, and the difference between the two hygroscopic expansion coefficients is within the above range, the ratio of the metal substrate is reduced. Even when the rigidity is reduced and the rigidity is lowered, the reason for being able to be a suspension base material with less warpage due to moisture absorption is as follows.

  That is, conventionally, the insulating layer has a large area covered on one surface of the metal substrate and is difficult to absorb moisture. For this reason, even when the hygroscopic expansion coefficient of the insulating layer is large, the hygroscopic expansion hardly occurs, so that the warp due to the hygroscopic expansion hardly occurred. For this reason, as long as the thermal expansion coefficients of the metal substrate and the insulating layer are matched, the warp of the suspension substrate can be suppressed to some extent.

  However, when the remaining ratio of the metal substrate is reduced due to low rigidity, a region not covered by the metal substrate spreads on the metal substrate side of the insulating layer, and the insulating layer can easily absorb moisture and expand. It became a situation. Conventionally, the metal substrate was able to sufficiently resist such expansion, but the insulation ratio and the cover layer having a large hygroscopic expansion coefficient due to the low residual ratio due to low rigidity. It has become difficult to resist the stress produced when hygroscopic expansion occurs. For this reason, when the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material is large, the hygroscopic expansion of both causes warping of the suspension substrate.

  On the other hand, in this embodiment, even if the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material forming the insulating layer and the cover layer is within the above-described range, The occurrence of warping caused by hygroscopic expansion of the insulating layer and the cover layer can be reduced.

In addition, conventionally, since the remaining ratio of the metal substrate which is a highly rigid material is large, even if the difference in the hygroscopic expansion coefficient between the insulating layer forming material and the cover layer forming material is large, the insulating layer and the cover layer Warpage could be suppressed to some extent by the difference in hygroscopic expansion. However, when the difference in the hygroscopic expansion coefficient between the insulating layer forming material and the cover layer forming material is large, the metal substrate whose rigidity is lowered due to the low rigidity can resist the stress caused by the difference between the hygroscopic expansion of the two. As a result, the suspension substrate was warped.
On the other hand, in this embodiment, the difference between the hygroscopic expansion coefficients of the insulating layer forming material and the cover layer forming material is within the above range, so that the cover layer forming material and the insulating material are insulated even when the rigidity is reduced. The occurrence of warpage due to the difference in hygroscopic expansion coefficient from the layer forming material can be reduced.

Further, since the insulating layer forming material and the cover layer forming material are different materials, there are the following advantages.

  That is, when the insulating layer forming material and the cover layer forming material are the same material, for example, a cover made of a cover layer forming material is formed on an insulating layer made of a metal substrate described later and made of an insulating layer forming material. When forming the cover layer in a pattern by laminating the layer formation layer and then dissolving the cover layer formation layer in a pattern, the insulating layer is formed with a solvent that dissolves the cover layer formation layer in the pattern. May be dissolved at the same time. For this reason, when forming the cover layer into a pattern, the insulating layer is strongly baked and hardened in advance so that the cover layer is not dissolved by a solvent that dissolves into the pattern, or the insulating layer is formed after the cover layer is formed. In the case of forming a pattern, it may be difficult to form the insulating layer in a pattern because the insulating layer (insulating layer forming layer) is strongly baked.

  Further, the suspension substrate is made of a laminate in which materials of a metal substrate, an insulating layer, a wiring layer, and a cover layer are laminated, and the above-described materials are required to be laminated with good adhesion. Therefore, for example, the insulating layer is required to have good adhesion to the metal substrate and the wiring layer, and the cover layer is required to have good adhesion to the insulating layer and the wiring layer. However, when the insulating layer forming material and the cover layer forming material for forming the insulating layer and the cover layer are the same material, it is difficult to satisfy the adhesiveness to such separate members at the same time, and the material selectivity The problem that becomes very narrow occurs.

  In this aspect, since the insulating layer forming material and the cover layer forming material are different materials, for example, a material that does not dissolve the insulating layer when forming the cover layer is used as the insulating layer forming material. The material suitable for the adhesiveness required for each can be easily selected. Therefore, since the insulating layer forming material and the cover layer forming material are different materials, for example, when the cover layer is formed, it is easy to make the material in which the insulating layer does not dissolve. be able to.

The suspension substrate of this aspect includes at least a metal substrate, an insulating layer, a wiring layer, and a cover layer.
Hereinafter, each configuration of the suspension substrate of this aspect will be described in detail.

(1) Insulating layer 2 and cover layer 4
The insulating layer used in this embodiment is formed on a metal substrate described later and is made of an insulating layer forming material.
Further, the cover layer used in this embodiment is formed of a cover layer forming material that is formed on the insulating layer and covers at least a part of the wiring layer described later.
The insulating layer and the cover layer may be made of a single material, or two or more different materials may be laminated. When the insulating layer or the cover layer is a laminate of different materials, the insulating layer and the cover layer respectively have characteristics such as hygroscopic expansion and linear thermal expansion as a whole of the laminate of two or more layers in the present invention. The characteristics of the insulating layer and the cover layer.
When a suspension is made from a laminate of stainless steel insulation layer-copper, when these three types are laminated and made, the insulation layer is made of adhesive material-low expansion material-adhesive material. In many cases, it has a layer structure, which is generally derived from poor adhesion of a low expansion material. Thus, the laminated body of the metal and insulating layer formed by lamination has the advantage that rolled copper and alloy copper can be used, and has the characteristics that the adhesiveness of an insulating layer and a metal layer is high. On the other hand, there is a limitation that the thickness of the copper foil used from the viewpoint of the stability of the laminate is limited, and it is difficult to make the copper layer thin.
On the other hand, as a method for producing the above laminate, there is also a method of forming a copper layer by sputtering or plating after an insulating layer is formed on stainless steel. In this case, the insulating layer can be formed of one kind of material, and the copper layer can be formed thin, but there is a drawback that only the electrolytic copper foil can be formed.

(A) Insulating layer forming material 2 'and cover layer forming material 4'
The insulating layer forming material 2 ′ and the cover layer 4 ′ forming material used in this embodiment are made of the same or different materials, and their hygroscopic expansion coefficients are in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH. Further, the difference between the two hygroscopic expansion coefficients is within the range of 5 × 10 ⁻⁶ /% RH or less.
The insulating layer forming material and the cover layer forming material are different materials, which means that the type and content of the main chain or substituent of the contained polymer are different. The photoinitiator and additive described later Not included if the type and content differ.

According to this aspect, since the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material and the difference between the two hygroscopic expansion coefficients are within the above range, the suspension substrate of the present aspect has low rigidity. Even in this case, warpage due to moisture absorption is reduced.
In addition, since the insulating layer forming material and the cover layer forming material are different materials, for example, it is easy to make the material in which the insulating layer does not dissolve when the cover layer is formed. Can do.

The hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material used in this embodiment may be in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and in particular, 0 /% RH to 20 It is preferably within the range of × 10 ⁻⁶ /% RH, and particularly preferably within the range of 0 /% RH to 12 × 10 ⁻⁶ /% RH.

In general, a material having a negative humidity expansion coefficient that contracts with moisture absorption applicable to this application is very rare, and in such a case, the range of material selection is narrow, which is not preferable. If it is larger than the above range, warpage due to moisture absorption becomes large, which is not preferable.
The hygroscopic expansion coefficient is a rate of change in the length of the material with respect to a change in relative humidity. Here, the length of the material is a length when each material has an equilibrium moisture content in each relative humidity environment by being placed in each relative humidity environment. The rate of change in material length is the change in length when the relative humidity changes (the length of the material after the change minus the length of the material before the change), and the total length of the material. The value divided by.

  Further, when the value of the hygroscopic expansion coefficient is positive, it indicates that the length of the material becomes longer when the relative humidity increases, and when the value of the hygroscopic expansion coefficient is negative, the relative humidity is Shows that the length of the material decreases as it rises.

The difference between the hygroscopic expansion coefficients of the insulating layer forming material and the cover layer forming material used in this embodiment may be 5 × 10 ⁻⁶ /% RH or less, and in particular, 4 × 10 ⁻⁶ /% RH or less. In particular, 3 × 10 ⁻⁶ /% RH or less is preferable. This is because, by being in the above range, even when the suspension substrate of this aspect is made to have a low rigidity, warpage due to moisture absorption can be reduced.
The difference in the hygroscopic expansion coefficient between the insulating layer forming material and the cover layer forming material is an absolute value of the difference in the hygroscopic expansion coefficient between the insulating layer forming material and the cover layer forming material.

The water absorption coefficient of the insulating layer forming material and cover layer forming material used in this embodiment is preferably in the range of 0.01% to 2.5%, and more preferably 0.1% to 1.5%. It is preferable to be within the range. It is because the moisture absorption of the said insulating layer and a cover layer can be decreased by being in the said range, and it can suppress that the said insulating layer and a cover layer do hygroscopic expansion. For this reason, even if it is a case where the residual ratio of the metal substrate mentioned later is reduced and the suspension substrate of this aspect is made low-rigidity, the warpage can be reduced. Further, if it is smaller than the above range, the adhesion between the cover layer and the insulating layer may be lowered, and if it is larger than the above range, warpage due to moisture absorption is large.
Here, the water absorption coefficient is a curl whose saturated water content is the water absorption rate when the insulating layer forming material and the cover layer forming material are left to stand for 1 hour in an environment of 85 ° C. and 85% RH. This is the rate of change in weight when the moisture content is used and when the moisture content is used, and when the moisture content is dried.

As the thermal expansion coefficients of the insulating layer forming material and the cover layer forming material used in this embodiment, the difference in thermal expansion coefficient between the suspension substrate, the metal substrate described later, and the insulating layer forming material and the cover layer forming material is used. However, it is preferably within a range of 15 × 10 ⁻⁶ / ° C. to 30 × 10 ⁻⁶ / ° C., and in particular, 15 × 10 ⁻⁶ / ° C. It is preferably within the range of ˜25 × 10 ⁻⁶ / ° C., and particularly preferably within the range of 15 × 10 ⁻⁶ / ° C. to 20 × 10 ⁻⁶ / ° C. This is because, within the above range, even when the suspension substrate of this aspect has a low rigidity, warpage due to a temperature change can be reduced.
The thermal expansion coefficient is a rate of change of the material length with respect to a change in temperature. Here, the length of the material is the length of the material when the material reaches each temperature. The rate of change in material length is the change in length (subtracting the length of the material before the change from the length of the material after the change) when the temperature of each material changes. The value divided by the total length of.
In addition, when the value of the thermal expansion coefficient is positive, it indicates that the length of the material is increased when the temperature of the material is increased, and when the value of the thermal expansion coefficient is negative, It shows that the length of the material decreases as the temperature increases.

The difference in thermal expansion coefficient between the insulating layer forming material and the cover layer forming material used in this embodiment is preferably within a range of 10 × 10 ⁻⁶ / ° C. or less, and particularly within a range of 5 × 10 ⁻⁶ / ° C. or less. It is preferable that This is because, by being in the above range, even when the suspension substrate of this embodiment has a low rigidity, warpage due to a temperature change can be reduced.
The difference in thermal expansion coefficient between the insulating layer forming material and the cover layer forming material is an absolute value of the difference in thermal expansion coefficient between the insulating layer forming material and the cover layer forming material.

The insulating layer forming material and the cover layer forming material used in this embodiment are not particularly limited as long as the hygroscopic expansion coefficient is in the above-described range and has an insulating property, and may be a photosensitive material. It may be a non-photosensitive material. In this embodiment, a non-photosensitive material is particularly preferable.
In this case, the non-photosensitive material refers to a material that cannot be patterned by the action of light alone, and the liquid, gas, or plasma passes through an opening provided by a mask formed of metal or resist. It is a material that needs to form a pattern by a method such as removing unnecessary portions by a method, or applying a pattern shape in advance by a method such as ink jet or screen printing.
More generally, it refers to a material that forms a pattern without containing a photosensitive component.
The use of non-photosensitive materials complicates the pattern formation process, but there is a merit that a wider range of materials can be selected by applying a purer material that does not contain a photosensitive component, which is necessary for the present invention. Thus, it is possible to apply a material having the characteristics of low hygroscopic expansion and low linear thermal expansion.

When the insulating layer forming material and the cover layer forming material are photosensitive materials, a photosensitive insulating material having a photosensitive group introduced into the molecular skeleton of the non-photosensitive insulating material described later is polymerized together with a photopolymerization initiator. In addition to the non-photosensitive insulating material or the photosensitive insulating material, a photosensitive monomer is added to the insulating layer forming material and the cover layer forming material and polymerized with a photopolymerization initiator, or the action of light. It is necessary to add a photosensitizer whose solubility varies depending on the condition. For this reason, even after passing through a post-process such as heating, the photosensitizing component and its decomposition residue remain in the material, the hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material is increased, and the adhesiveness is increased. This is because it may be very difficult to optimize.
A photosensitive polyimide resin (PI) generally used as a photosensitive insulating material requires the use of a high-boiling solvent such as γ-butyrolactone, N-methylpyrrolidone or dimethylacetamide as a developing solvent, and requires time for drying. Cost. Further, the developing solvent for the photosensitive polyimide resin described above is expensive per se, and equipment for development must be made explosion-proof, which is very disadvantageous in terms of cost. Further, the developing solvent for the photosensitive polyimide resin mentioned above has a problem that the photosensitive polyimide resin itself may be damaged.
On the other hand, when the insulating layer forming material and the cover layer forming material are non-photosensitive materials, the introduction of a photosensitive group into the non-photosensitive insulating material and other additives are not required, so that the hygroscopic expansion is performed. Adjustment of coefficients and the like can be facilitated. In developing, organic and inorganic alkalis can be used, and the above-described explosion-proof equipment is not required. Therefore, the insulating layer and the cover layer can be formed at low cost, and damage is reduced. be able to

When the insulating layer forming material and the cover layer forming material used in the present embodiment are non-photosensitive, the insulating layer forming material and the cover layer forming material usually have non-photosensitive insulating characteristics.
Examples of such non-photosensitive insulating materials include polyimide resins, acrylic resins, polyether nitrile resins, polyether sulfone resins, polyethylene terephthalate resins, polyethylene naphthalate resins, and polyvinyl chloride resins. A synthetic resin can be used, and among them, a polyimide resin can be preferably used. This is because the compound is excellent in insulation, heat resistance and chemical resistance.

  In addition, when the insulating layer forming material and the cover layer forming material used in this embodiment are photosensitive, the insulating layer forming material and the cover layer forming material usually introduce a photosensitive group into the above-described non-photosensitive insulating material. A polymer of the photosensitive insulating material or photosensitive monomer.

  Examples of the photosensitive insulating material include photosensitive polyimide resins, photosensitive acrylic resins, photosensitive polyether nitrile resins, photosensitive polyether sulfone resins, photosensitive polyethylene terephthalate resins, and photosensitive polyethylene naphthalate resins. A photosensitive synthetic resin such as a resin or a photosensitive polyvinyl chloride resin can be preferably used, and among them, a photosensitive polyimide resin can be preferably used. This photosensitive polyimide material resin is a compound having excellent insulating properties, and is a compound having excellent insulating properties, heat resistance and chemical resistance.

  As the photosensitive group, the photosensitive monomer, and the photopolymerization initiator used in the polymerization, those generally used when the insulating layer and the cover layer of the suspension substrate are formed by exposure and development can be used. it can.

（Ｒ１は４価の有機基、Ｒ２は２価の有機基、Ｒ１及びＲ２は、単一構造でもよく２種以上の組み合わせでもよい。ｎは１以上の自然数）

式（１）において、一般に、Ｒ^１は、テトラカルボン酸二無水物由来の構造であり、Ｒ^２はジアミン由来の構造である。
本発明に用いられるポリイミドに適用可能な酸二無水物としては、例えば、エチレンテトラカルボン酸二無水物、ブタンテトラカルボン酸二無水物、シクロブタンテトラカルボン酸二無水物、シクロペンタンテトラカルボン酸二無水物、ピロメリット酸二無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸二無水物、２，２’，３，３’−ベンゾフェノンテトラカルボン酸二無水物、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物、２，２’，３，３’−ビフェニルテトラカルボン酸二無水物、２，２’，６，６’−ビフェニルテトラカルボン酸二無水物、２，２−ビス（３，４−ジカルボキシフェニル）プロパン二無水物、２，２−ビス（２，３−ジカルボキシフェニル）プロパン二無水物、ビス（３，４−ジカルボキシフェニル）エーテル二無水物、ビス（３，４−ジカルボキシフェニル）スルホン二無水物、１，１−ビス（２，３−ジカルボキシフェニル）エタン二無水物、ビス（２，３−ジカルボキシフェニル）メタン二無水物、ビス（３，４−ジカルボキシフェニル）メタン二無水物、２，２−ビス（３，４−ジカルボキシフェニル）−１，１，１，３，３，３−ヘキサフルオロプロパン二無水物、２，２−ビス（２，３−ジカルボキシフェニル）−１，１，１，３，３，３−ヘキサフルオロプロパン二無水物、１，３−ビス〔（３，４−ジカルボキシ）ベンゾイル〕ベンゼン二無水物、１，４−ビス〔（３，４−ジカルボキシ）ベンゾイル〕ベンゼン二無水物、２，２−ビス｛４−〔４−（１，２−ジカルボキシ）フェノキシ〕フェニル｝プロパン二無水物、
２，２−ビス｛４−〔３−（１，２−ジカルボキシ）フェノキシ〕フェニル｝プロパン二無水物、ビス｛４−〔４−（１，２−ジカルボキシ）フェノキシ〕フェニル｝ケトン二無水物、ビス｛４−〔３−（１，２−ジカルボキシ）フェノキシ〕フェニル｝ケトン二無水物、４，４’−ビス〔４−（１，２−ジカルボキシ）フェノキシ〕ビフェニル二無水物、４，４’−ビス〔３−（１，２−ジカルボキシ）フェノキシ〕ビフェニル二無水物、ビス｛４−〔４−（１，２−ジカルボキシ）フェノキシ〕フェニル｝ケトン二無水物、ビス｛４−〔３−（１，２−ジカルボキシ）フェノキシ〕フェニル｝ケトン二無水物、ビス｛４−〔４−（１，２−ジカルボキシ）フェノキシ〕フェニル｝スルホン二無水物、ビス｛４−〔３−（１，２−ジカルボキシ）フェノキシ〕フェニル｝スルホン二無水物、ビス｛４−〔４−（１，２−ジカルボキシ）フェノキシ〕フェニル｝スルフィド二無水物、ビス｛４−〔３−（１，２−ジカルボキシ）フェノキシ〕フェニル｝スルフィド二無水物、２，２−ビス｛４−〔４−（１，２−ジカルボキシ）フェノキシ〕フェニル｝−１，１，１，３，３，３−ヘキサフルプロパン二無水物、２，２−ビス｛４−〔３−（１，２−ジカルボキシ）フェノキシ〕フェニル｝−１，１，１，３，３，３−プロパン二無水物、２，３，６，７−ナフタレンテトラカルボン酸二無水物、１，４，５，８−ナフタレンテトラカルボン酸二無水物、１，２，５，６−ナフタレンテトラカルボン酸二無水物、１，２，３，４−ベンゼンテトラカルボン酸二無水物、３，４，９，１０−ぺリレンテトラカルボン酸二無水物、２，３，６，７−アントラセンテトラカルボン酸二無水物、１，２，７，８−フェナントレンテトラカルボン酸二無水物等が挙げられる。
これらは単独あるいは２種以上混合して用いられる。
本発明に用いられるポリイミドの耐熱性、線熱膨張係数などの観点から好ましく用いられるテトラカルボン酸二無水物は、芳香族テトラカルボン酸二無水物であることが好ましく、特に好ましく用いられるテトラカルボン酸二無水物としてピロメリット酸二無水物、メロファン酸二無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸二無水物、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物、２，３，３’，４’−ビフェニルテトラカルボン酸二無水物、２，３，２’，３’−ビフェニルテトラカルボン酸二無水物、２，２’，６，６’−ビフェニルテトラカルボン酸二無水物、ビス（３，４−ジカルボキシフェニル）エーテル二無水物、２，２−ビス（３，４−ジカルボキシフェニル）−１，１，１，３，３，３−ヘキサフルオロプロパン二無水物、ビス（３，４−ジカルボキシフェニル）エーテル二無水物が挙げられる。
なかでも、吸湿膨張を低減させる観点から、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物、２，３，３’，４’−ビフェニルテトラカルボン酸二無水物、２，３，２’，３’−ビフェニルテトラカルボン酸二無水物、ビス（３，４−ジカルボキシフェニル）エーテル二無水物が特に好ましい。
併用する酸二無水物としてフッ素が導入された酸二無水物を用いると、ポリイミドの吸湿膨張率が低下する。しかし、フッ素を含んだ骨格を有するポリイミドの前駆体は、塩基性水溶液に溶解しにくく、アルコール等の有機溶媒と塩基性水溶液との混合溶液によって現像を行う必要がある。
また、ピロメリット酸二無水物、メロファン酸二無水物、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物、２，３，３’，４’−ビフェニルテトラカルボン酸二無水物、２，３，２’，３’−ビフェニルテトラカルボン酸二無水物、１，４，５，８−ナフタレンテトラカルボン酸二無水物などの剛直な酸二無水物を用いると、最終的に得られるポリイミドの線熱膨張係数が小さくなるので好ましい。なかでも、線膨張係数と湿度膨張係数とのバランスの観点から、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物、２，３，３’，４’−ビフェニルテトラカルボン酸二無水物、２，３，２’，３’−ビフェニルテトラカルボン酸二無水物、が特に好ましい。
酸二無水物として脂環骨格を有する場合、ポリイミド前駆体のが向上するため、高感度の感光性樹脂組成物となる。一方で、ポリイミドとした後の耐熱性や絶縁性が芳香族ポリイミドと比較して劣る傾向にある。。
芳香族のテトラカルボン酸二無水物を用いた場合、耐熱性に優れ、低線熱膨張係数を示すポリイミドとなるというメリットがある。従って、本発明の感光性樹脂組成物においては、前記ポリイミドにおいて、前記式（１）中のＲ^１のうち３３モル％以上が、下記式（３）で表わされる構造であることが好ましい。

上記のような構造を有するポリイミドは、高耐熱、低線熱膨張率を示すポリイミドである。その為、上記式（２）で表わされる構造の含有量は前記式（１）中のＲ^１のうち１００モル％に近ければ近いほど、本発明の目標を達成しやすくなるが、少なくとも前記式（１）中のＲ^１のうち３３％以上含有すれば目的を達成できる。中でも上記式（２）で表わされる構造の含有量は前記式（１）中のＲ^１のうち５０モル％以上であることが好ましく、更に、７０モル％以上であることが好ましい。
一方、本発明のポリイミドに適用可能なジアミン成分も、１種類のジアミン単独で、または２種類以上のジアミンを併用して用いることができる。用いられるジアミン成分は限定されるわけではないが、ｐ−フェニレンジアミン、ｍ−フェニレンジアミン、ｏ−フェニレンジアミン、３，３’−ジアミノジフェニルエーテル、３，４’−ジアミノジフェニルエーテル、４，４’−ジアミノジフェニルエーテル、３，３’−ジアミノジフェニルスルフィド、３，４’−ジアミノジフェニルスルフィド、４，４’−ジアミノジフェニルスルフィド、３，３’−ジアミノジフェニルスルホン、３，４’−ジアミノジフェニルスルホン、４，４’−ジアミノジフェニルスルホン、３，３’−ジアミノベンゾフェノン、４，４’−ジアミノベンゾフェノン、
３，４’−ジアミノベンゾフェノン、３，３’−ジアミノジフェニルメタン、４，４’−ジアミノジフェニルメタン、３，４’−ジアミノジフェニルメタン、２，２−ジ（３−アミノフェニル）プロパン、２，２−ジ（４−アミノフェニル）プロパン、２−（３−アミノフェニル）−２−（４−アミノフェニル）プロパン、２，２−ジ（３−アミノフェニル）−１，１，１，３，３，３−ヘキサフルオロプロパン、２，２−ジ（４−アミノフェニル）−１，１，１，３，３，３−ヘキサフルオロプロパン、２−（３−アミノフェニル）−２−（４−アミノフェニル）−１，１，１，３，３，３−ヘキサフルオロプロパン、１，１−ジ（３−アミノフェニル）−１−フェニルエタン、１，１−ジ（４−アミノフェニル）−１−フェニルエタン、１−（３−アミノフェニル）−１−（４−アミノフェニル）−１−フェニルエタン、１，３−ビス（３−アミノフェノキシ）ベンゼン、１，３−ビス（４−アミノフェノキシ）ベンゼン、１，４−ビス（３−アミノフェノキシ）ベンゼン、１，４−ビス（４−アミノフェノキシ）ベンゼン、１，３−ビス（３−アミノベンゾイル）ベンゼン、１，３−ビス（４−アミノベンゾイル）ベンゼン、１，４−ビス（３−アミノベンゾイル）ベンゼン、１，４−ビス（４−アミノベンゾイル）ベンゼン、１，３−ビス（３−アミノ−α，α−ジメチルベンジル）ベンゼン、１，３−ビス（４−アミノ−α，α−ジメチルベンジル）ベンゼン、１，４−ビス（３−アミノ−α，α−ジメチルベンジル）ベンゼン、１，４−ビス（４−アミノ−α，α−ジメチルベンジル）ベンゼン、１，３−ビス（３−アミノ−α，α−ジトリフルオロメチルベンジル）ベンゼン、１，３−ビス（４−アミノ−α，α−ジトリフルオロメチルベンジル）ベンゼン、１，４−ビス（３−アミノ−α，α−ジトリフルオロメチルベンジル）ベンゼン、１，４−ビス（４−アミノ−α，α−ジトリフルオロメチルベンジル）ベンゼン、２，６−ビス（３−アミノフェノキシ）ベンゾニトリル、２，６−ビス（３−アミノフェノキシ）ピリジン、４，４’−ビス（３−アミノフェノキシ）ビフェニル、４，４’−ビス（４−アミノフェノキシ）ビフェニル、ビス［４−（３−アミノフェノキシ）フェニル］ケトン、ビス［４−（４−アミノフェノキシ）フェニル］ケトン、ビス［４−（３−アミノフェノキシ）フェニル］スルフィド、ビス［４−（４−アミノフェノキシ）フェニル］スルフィド、
ビス［４−（３−アミノフェノキシ）フェニル］スルホン、ビス［４−（４−アミノフェノキシ）フェニル］スルホン、ビス［４−（３−アミノフェノキシ）フェニル］エーテル、ビス［４−（４−アミノフェノキシ）フェニル］エーテル、２，２−ビス［４−（３−アミノフェノキシ）フェニル］プロパン、２，２−ビス［４−（４−アミノフェノキシ）フェニル］プロパン、２，２−ビス［３−（３−アミノフェノキシ）フェニル］−１，１，１，３，３，３−ヘキサフルオロプロパン、２，２−ビス［４−（４−アミノフェノキシ）フェニル］−１，１，１，３，３，３−ヘキサフルオロプロパン、１，３−ビス［４−（３−アミノフェノキシ）ベンゾイル］ベンゼン、１，３−ビス［４−（４−アミノフェノキシ）ベンゾイル］ベンゼン、１，４−ビス［４−（３−アミノフェノキシ）ベンゾイル］ベンゼン、１，４−ビス［４−（４−アミノフェノキシ）ベンゾイル］ベンゼン、１，３−ビス［４−（３−アミノフェノキシ）−α，α−ジメチルベンジル］ベンゼン、１，３−ビス［４−（４−アミノフェノキシ）−α，α−ジメチルベンジル］ベンゼン、１，４−ビス［４−（３−アミノフェノキシ）−α，α−ジメチルベンジル］ベンゼン、１，４−ビス［４−（４−アミノフェノキシ）−α，α−ジメチルベンジル］ベンゼン、４，４’−ビス［４−（４−アミノフェノキシ）ベンゾイル］ジフェニルエーテル、４，４’−ビス［４−（４−アミノ−α，α−ジメチルベンジル）フェノキシ］ベンゾフェノン、４，４’−ビス［４−（４−アミノ−α，α−ジメチルベンジル）フェノキシ］ジフェニルスルホン、４，４’−ビス［４−（４−アミノフェノキシ）フェノキシ］ジフェニルスルホン、３，３’−ジアミノ−４，４’−ジフェノキシベンゾフェノン、３，３’−ジアミノ−４，４’−ジビフェノキシベンゾフェノン、３，３’−ジアミノ−４−フェノキシベンゾフェノン、３，３’−ジアミノ−４−ビフェノキシベンゾフェノン、６，６’−ビス（３−アミノフェノキシ）−３，３，３’，３’−テトラメチル−１，１’−スピロビインダン、６，６’−ビス（４−アミノフェノキシ）−３，３，３’，３’−テトラメチル−１，１’−スピロビインダン、１，３−ビス（３−アミノプロピル）テトラメチルジシロキサン、１，３−ビス（４−アミノブチル）テトラメチルジシロキサン、α，ω−ビス（３−アミノプロピル）ポリジメチルシロキサン、α，ω−ビス（３−アミノブチル）ポリジメチルシロキサン、ビス（アミノメチル）エーテル、ビス（２−アミノエチル）エーテル、ビス（３−アミノプロピル）エーテル、ビス（２−アミノメトキシ）エチル］エーテル、ビス［２−（２−アミノエトキシ）エチル］エーテル、ビス［２−（３−アミノプロトキシ）エチル］エーテル、
１，２−ビス（アミノメトキシ）エタン、１，２−ビス（２−アミノエトキシ）エタン、１，２−ビス［２−（アミノメトキシ）エトキシ］エタン、１，２−ビス［２−（２−アミノエトキシ）エトキシ］エタン、エチレングリコールビス（３−アミノプロピル）エーテル、ジエチレングリコールビス（３−アミノプロピル）エーテル、トリエチレングリコールビス（３−アミノプロピル）エーテル、エチレンジアミン、１，３−ジアミノプロパン、１，４−ジアミノブタン、１，５−ジアミノペンタン、１，６−ジアミノヘキサン、１，７−ジアミノヘプタン、１，８−ジアミノオクタン、１，９−ジアミノノナン、１，１０−ジアミノデカン、１，１１−ジアミノウンデカン、１，１２−ジアミノドデカン、１，２−ジアミノシクロヘキサン、１，３−ジアミノシクロヘキサン、１，４−ジアミノシクロヘキサン、１，２−ジ（２−アミノエチル）シクロヘキサン、１，３−ジ（２−アミノエチル）シクロヘキサン、１，４−ジ（２−アミノエチル）シクロヘキサン、ビス（４−アミノシクロへキシル）メタン、２，６−ビス（アミノメチル）ビシクロ［２．２．１］ヘプタン、２，５−ビス（アミノメチル）ビシクロ［２．２．１］ヘプタン、また、上記ジアミンの芳香環上水素原子の一部若しくは全てをフルオロ基、メチル基、メトキシ基、トリフルオロメチル基、又はトリフルオロメトキシ基から選ばれた置換基で置換したジアミンも使用することができる。
さらに目的に応じ、架橋点となるエチニル基、ベンゾシクロブテン−４’−イル基、ビニル基、アリル基、シアノ基、イソシアネート基、及びイソプロペニル基のいずれか１種又は２種以上を、上記ジアミンの芳香環上水素原子の一部若しくは全てに置換基として導入しても使用することができる。
ジアミンは、目的の物性によって選択することができ、ｐ−フェニレンジアミンなどの剛直なジアミンを用いれば、最終的に得られるポリイミドは低膨張率となる。剛直なジアミンとしては、同一の芳香環に２つアミノ基が結合しているジアミンとして、ｐ−フェニレンジアミン、ｍ−フェニレンジアミン、１，４−ジアミノナフタレン、１，５−ジアミノナフタレン、２、６−ジアミノナフタレン、２，７−ジアミノナフタレン、１，４−ジアミノアントラセンなどが挙げられる。
さらに、２つ以上の芳香族環が単結合により結合し、２つ以上のアミノ基がそれぞれ別々の芳香族環上に直接又は置換基の一部として結合しているジアミンが挙げられ、例えば、下記式（３）により表されるものがある。具体例としては、ベンジジン等が挙げられる。

（ａは０または１以上の自然数、アミノ基はベンゼン環同士の結合に対して、メタ位または、パラ位に結合する。）

さらに、上記式（５）において、他のベンゼン環との結合に関与せず、ベンゼン環上のアミノ基が置換していない位置に置換基を有するジアミンも用いることができる。これら置換基は、１価の有機基であるがそれらは互いに結合していてもよい。
具体例としては、２，２’−ジメチル−４，４’−ジアミノビフェニル、２，２’−ジトリフルオロメチル−４，４’−ジアミノビフェニル、３，３’−ジクロロ−４，４’−ジアミノビフェニル、３，３’−ジメトキシ−４，４’−ジアミノビフェニル、３，３’−ジメチル−４，４’−ジアミノビフェニル等が挙げられる。
また、芳香環の置換基としてフッ素を導入すると吸湿膨張率を低減させることができる。しかし、フッ素を含むポリイミド前駆体、特にポリアミック酸は、塩基性水溶液に溶解しにくく、アルコールなどの有機溶媒との混合溶液で現像する必要がある場合がある。 Further, the insulating layer forming material and cover layer forming material used in this embodiment may be added with a sensitizer, a polymerization terminator, a chain transfer agent, a leveling agent, a plasticizer, a surfactant, an antifoaming agent, etc., as necessary. An agent may be included.

(R1 is a tetravalent organic group, R2 is a divalent organic group, R1 and R2 may be a single structure or a combination of two or more types, n is a natural number of 1 or more)

In the formula (1), generally, R ¹ is a structure derived from tetracarboxylic dianhydride, and R ² is a structure derived from diamine.
Examples of the acid dianhydride applicable to the polyimide used in the present invention include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, cyclobutane tetracarboxylic dianhydride, and cyclopentane tetracarboxylic dianhydride. , Pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride, 2 , 2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxypheny ) Ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) ) Methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoro Propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4- Dicarboxy) benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) Phenoxy] phenyl} propane dianhydride
2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride Bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, 4,4′-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4,4′-bis [3- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis { 4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [3- (1,2-dicarbox ) Phenoxy] phenyl} sulfone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy ] Phenyl} sulfide dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-hexafulpropane dianhydride 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-propane dianhydride, 2,3,6,7- Naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetra Carboxylic dianhydride, 3,4,9,10 -Perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride and the like.
These may be used alone or in combination of two or more.
The tetracarboxylic dianhydride preferably used from the viewpoint of the heat resistance, linear thermal expansion coefficient, etc. of the polyimide used in the present invention is preferably an aromatic tetracarboxylic dianhydride, and particularly preferably used tetracarboxylic acid. Pyromellitic dianhydride, merophanic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride Anhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride, 2,2 ′, 6,6′-biphenyl Tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoro Examples include lopropane dianhydride and bis (3,4-dicarboxyphenyl) ether dianhydride.
Among these, from the viewpoint of reducing hygroscopic expansion, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,3 2,2 ′, 3′-biphenyltetracarboxylic dianhydride and bis (3,4-dicarboxyphenyl) ether dianhydride are particularly preferred.
When an acid dianhydride into which fluorine is introduced is used as the acid dianhydride used in combination, the hygroscopic expansion coefficient of the polyimide is lowered. However, a polyimide precursor having a fluorine-containing skeleton is difficult to dissolve in a basic aqueous solution and needs to be developed with a mixed solution of an organic solvent such as alcohol and a basic aqueous solution.
In addition, pyromellitic dianhydride, merophanic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride When rigid acid dianhydrides such as 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride are used, it is finally obtained. Since the linear thermal expansion coefficient of the polyimide obtained becomes small, it is preferable. Among these, from the viewpoint of the balance between the linear expansion coefficient and the humidity expansion coefficient, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic acid dihydrate. The anhydride, 2,3,2 ′, 3′-biphenyltetracarboxylic dianhydride, is particularly preferred.
When the acid dianhydride has an alicyclic skeleton, the polyimide precursor is improved, so that a highly sensitive photosensitive resin composition is obtained. On the other hand, the heat resistance and insulation after the polyimide is inferior compared to the aromatic polyimide. .
When an aromatic tetracarboxylic dianhydride is used, there is a merit that it becomes a polyimide having excellent heat resistance and a low linear thermal expansion coefficient. Therefore, in the photosensitive resin composition of the present invention, in the polyimide, 33 mol% or more of R ¹ in the formula (1) preferably has a structure represented by the following formula (3).

The polyimide having the above structure is a polyimide that exhibits high heat resistance and low linear thermal expansion coefficient. Therefore, the closer the content of the structure represented by the above formula (2) is to 100 mol% of R ^{1 in} the above formula (1), the easier it is to achieve the object of the present invention. The purpose can be achieved by containing 33% or more of R ^{1 in} (1). Of these the content of the structure represented by the above formula (2) is preferably the at formula (1) 50 mol% or more of R ¹ in, it is more preferably 70 mol% or more.
On the other hand, a diamine component applicable to the polyimide of the present invention can be used alone or in combination of two or more diamines. The diamine component used is not limited, but p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diamino. Diphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4 '-Diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone,
3,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2,2-di (3-aminophenyl) -1,1,1,3,3,3 -Hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane , 1- ( 3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4- Bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1, 4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4 -Amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-α, α-dimethylbenzyl) L) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4- Bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2,6-bis (3-aminophenoxy) benzo Nitrile, 2,6-bis (3-aminophenoxy) pyridine, 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (3- Aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [ - (4-aminophenoxy) phenyl] sulfide,
Bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-amino) Phenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3 3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] ben 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-amino Phenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -Α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4'-bis [4- (4-aminophenoxy) benzoyl ] Diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) Enoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4, 4′-dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 6,6′-bis (3-aminophenoxy) -3,3,3 ', 3'-tetramethyl-1,1'-spirobiindane, 6,6'-bis (4-aminophenoxy) -3,3,3', 3'-tetramethyl-1,1'-spirobiindane, 1, 3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis (3-aminopropyl) poly Methylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis (2-aminomethoxy) Ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether,
1,2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2 -Aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1, 11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohex 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2- Aminoethyl) cyclohexane, bis (4-aminocyclohexyl) methane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) bicyclo [2.2. 1] A diamine obtained by substituting some or all of the hydrogen atoms on the aromatic ring of the above diamine with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group. Can be used.
Furthermore, depending on the purpose, any one or two or more of the ethynyl group, benzocyclobuten-4′-yl group, vinyl group, allyl group, cyano group, isocyanate group, and isopropenyl group serving as a crosslinking point, Even if it introduce | transduces into some or all of the hydrogen atoms on the aromatic ring of diamine as a substituent, it can be used.
The diamine can be selected depending on the desired physical properties. If a rigid diamine such as p-phenylenediamine is used, the finally obtained polyimide has a low expansion coefficient. Rigid diamines include p-phenylenediamine, m-phenylenediamine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2, 6 as diamines in which two amino groups are bonded to the same aromatic ring. -Diaminonaphthalene, 2,7-diaminonaphthalene, 1,4-diaminoanthracene and the like can be mentioned.
In addition, diamines in which two or more aromatic rings are bonded by a single bond, and two or more amino groups are each bonded directly or as part of a substituent on a separate aromatic ring, for example, There exists what is represented by following formula (3). Specific examples include benzidine and the like.

(A is a natural number of 0 or 1 or more, and the amino group is bonded to the meta position or the para position with respect to the bond between the benzene rings.)

Furthermore, in the above formula (5), a diamine having a substituent at a position where the amino group on the benzene ring is not substituted and which does not participate in the bond with another benzene ring can also be used. These substituents are monovalent organic groups, but they may be bonded to each other.
Specific examples include 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diamino. Biphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl and the like can be mentioned.
Further, when fluorine is introduced as a substituent of the aromatic ring, the hygroscopic expansion coefficient can be reduced. However, a polyimide precursor containing fluorine, particularly polyamic acid, is difficult to dissolve in a basic aqueous solution and may need to be developed with a mixed solution with an organic solvent such as alcohol.

（Ｒ^３は２価の有機基、酸素原子、硫黄原子、又はスルホン基であり、Ｒ^４及びＲ^５は１価の有機基、又はハロゲン原子である。）
上記のような構造を有する場合、最終的に得られるポリイミドの耐熱性が向上し、線熱膨張係数が小さくなる。その為、前記式（１）中のＲ^２のうち１００モル％に近ければ近いほど、本発明の目標を達成しやすくなるが、前記式（１）中のＲ^２のうち少なくとも３３％以上含有すれば目的を達成できる。中でも上記式（４）で表わされる構造の含有量は前記式（１）中のＲ^２のうち５０モル％以上であることが好ましく、更に、７０モル％以上であることが好ましい。
上記のポリイミドに加えて必要に応じて適宜、接着性のポリイミドなどと組み合わせて、本発明における絶縁層、及びカバー層として用いてもよい。
また、上記のポリイミドを感光性ポリイミドとして利用する際には、公知の手法を用いることができる。たとえば、ポリアミック酸のカルボキシル基にエステル結合やイオン結合でエチレン性２重結合を導入し得られるポリイミド前駆体に、光ラジカル開始剤を混合し、溶剤現像ネガ型感光性ポリイミドとするもの。ポリアミック酸やその部分エステル化物にナフトキノンジアジド化合物を添加し、アルカリ現像ポジ型感光性ポリイミドとするもの、ポリアミック酸にニフェジピン系化合物を添加しアルカリ現像ネガ型感光性ポリイミドとするものなどが挙げられるが、これに限定されない。
これらの感光性ポリイミドはポリイミドの重量に対して１５％〜３５％の感光性付与成分が添加されている、その為、パターン形成後に３００℃〜４００℃で加熱したとしても、感光性付与成分由来の残差がポリイミド中に残存する。これらの残存物が線膨張係数や吸湿膨張係数を大きくする原因となることから、本発明において感光性ポリイミドを用いることは好ましくない。
なお絶縁層形成材料およびカバー層形成材料のいずれか、または両方の前駆体が塩基性水溶液によって現像可能となっている。ここで塩基性水溶液とは、ｐＨが８以上の水溶液で、有機溶媒の含有量が、塩基性水溶液の重量の２０重量％未満であることが好ましく、ｐＨが８以上の水溶液で、有機溶媒を含まないことがさらに好ましい。塩基性水溶液に含まれる塩基性物質は、何でも良く公知の有機・無機の塩基性物質であれば特に限定されないが、現像後のパターン中のイオン残渣や絶縁信頼性の観点から水酸化テトラメチルアンモニウムであることが好ましい。 On the other hand, when a diamine having a siloxane skeleton such as 1,3-bis (3-aminopropyl) tetramethyldisiloxane is used as the diamine, the adhesiveness with the substrate is improved or the finally obtained polyimide has an elastic modulus. The glass transition temperature can be lowered.
Here, the selected diamine is preferably an aromatic diamine from the viewpoint of heat resistance. However, depending on the desired physical properties, the diamine may be an aliphatic diamine or siloxane within a range not exceeding 60 mol%, preferably not exceeding 40 mol%. Non-aromatic diamines such as diamines may be used.
Moreover, in the said polyimide, it is preferable that 33 mol% or more is a structure represented by following formula (4) among R < ² > in said formula (1).

(R ³ is a divalent organic group, an oxygen atom, a sulfur atom, or a sulfone group, and R ⁴ and R ⁵ are a monovalent organic group or a halogen atom.)
When it has the above structure, the heat resistance of the polyimide finally obtained improves and a linear thermal expansion coefficient becomes small. Therefore, the closer to 100 mol% of R ² in the formula (1), the easier it is to achieve the target of the present invention, but at least 33% or more of R ² in the formula (1) is contained. You can achieve your goal. Of these the content of the structure represented by the above formula (4) is preferably the at formula (1) 50 mol% or more of R ² in, it is more preferably 70 mol% or more.
In addition to the above-described polyimide, it may be used as an insulating layer and a cover layer in the present invention by appropriately combining with an adhesive polyimide as required.
Moreover, when utilizing said polyimide as a photosensitive polyimide, a well-known method can be used. For example, a photo-radical initiator is mixed with a polyimide precursor obtained by introducing an ethylenic double bond through an ester bond or an ionic bond into a carboxyl group of a polyamic acid to obtain a solvent-developed negative photosensitive polyimide. Examples include those in which a naphthoquinone diazide compound is added to a polyamic acid or a partially esterified product thereof to obtain an alkali development positive photosensitive polyimide, and those in which a nifedipine compound is added to a polyamic acid to obtain an alkali development negative photosensitive polyimide. However, the present invention is not limited to this.
These photosensitive polyimides have 15% to 35% of a photosensitive component added to the weight of the polyimide. Therefore, even if heated at 300 ° C. to 400 ° C. after pattern formation, the photosensitive component is derived. This residual remains in the polyimide. Since these residues cause the linear expansion coefficient and the hygroscopic expansion coefficient to increase, it is not preferable to use photosensitive polyimide in the present invention.
Note that either or both of the insulating layer forming material and the cover layer forming material can be developed with a basic aqueous solution. Here, the basic aqueous solution is an aqueous solution having a pH of 8 or more, and the content of the organic solvent is preferably less than 20% by weight of the weight of the basic aqueous solution, and the organic solvent is an aqueous solution having a pH of 8 or more. More preferably it does not contain. The basic substance contained in the basic aqueous solution is not particularly limited as long as it is a known organic / inorganic basic substance, but tetramethylammonium hydroxide is used from the viewpoint of ion residue in the pattern after development and insulation reliability. It is preferable that

(B) Insulating layer 2
The film thickness of the insulating layer used in this embodiment is not particularly limited as long as the desired insulating property can be exhibited. For example, it is preferably in the range of 5 to 30 μm, However, it is preferably within the range of 5 μm to 18 μm, and particularly preferably within the range of 5 μm to 12 μm. If the thickness is smaller than the above range, sufficient insulation may not be exhibited. If the thickness is larger than the above range, it is difficult to reduce the rigidity of the suspension substrate.

The ratio of the lower surface of the insulating layer used in this embodiment to be covered with the metal substrate (ratio other than the low rigidity region) is that the suspension substrate according to this embodiment can be less warped. Specifically, it is preferably in the range of 30% to 70%, and more preferably in the range of 40% to 70%. By being in the above range, it is possible to reduce the rigidity of the suspension substrate of this aspect, and it is possible to further exhibit the effects of this aspect.
Note that the remaining ratio of the insulating layer refers to the ratio of the planar view area of the insulating layer to the planar view area of the suspension substrate of this aspect. The plan view area of the suspension substrate is an area surrounded by the outer diameter line of the suspension substrate. When a through hole is formed inside, the plan view area of the through hole is also included. .

(C) Cover layer 4
The film thickness of the cover layer used in this embodiment is not particularly limited as long as it is formed so as to cover at least a part of a wiring layer to be described later. In particular, it is preferably in the range of 3 μm to 15 μm, particularly preferably in the range of 3 μm to 10 μm. If the thickness is smaller than the above range, it is difficult to cover the wiring layer and protect the wiring layer from corrosion or the like. This is because it becomes difficult.

(2) Metal substrate 1
Since the metal substrate used in this embodiment has conductivity and is further used for suspension applications, it usually has an appropriate spring property.

  Examples of the material of the metal substrate include SUS.

  In this aspect, the metal substrate has a conductive layer on the surface side where the ground terminal is formed. In this case, by providing the conductive layer, conduction by the ground terminal becomes more efficient. Specific examples of the material for the conductive layer include copper (Cu). The conductive layer can be formed by, for example, a plating method.

  The thickness of the metal substrate is not particularly limited as long as the desired spring characteristics can be exhibited, and varies depending on the material of the metal substrate, but is usually in the range of 10 μm to 30 μm. Among these, it is preferable that it is in the range of 15 μm to 25 μm. If the metal substrate is too thin, the mechanical strength may be reduced, and if the metal substrate is too thick, it is difficult to reduce the rigidity of the suspension substrate of this aspect.

The remaining ratio of the metal substrate used in this embodiment is not particularly limited as long as the suspension substrate according to this embodiment can reduce warpage, and is specifically within a range of 30% to 100%. It is preferable that it is in the range of 30% to 60%. It is because the rigidity of the suspension substrate of this aspect can be sufficiently reduced and the effects of this aspect can be exhibited more by being in the above range.
The residual ratio of the metal substrate refers to the ratio of the planar view area of the metal substrate to the planar view area of the suspension substrate of this aspect. The plan view area of the suspension substrate is an area surrounded by the outer diameter line of the suspension substrate. When a through hole is formed inside, the plan view area of the through hole is also included. .

(3) Wiring layer 3
The wiring layer used in this aspect is formed on the above-described insulating layer. When the suspension substrate of this aspect is used in an HDD, data written to the disk via a slider or read from the disk is read. The output data is transmitted as an electrical signal.

  Examples of the material for the wiring layer used in this embodiment include copper (Cu: rolled copper, electrolytic copper).

  The thickness of the wiring layer used in this embodiment is not particularly limited as long as the desired conductivity can be exhibited, but it is usually preferably in the range of 6 μm to 18 μm, and more preferably 8 μm to It is preferably within the range of 12 μm. This is because the rigidity of the suspension substrate of this aspect can be reduced by being in the above range.

  The line width of the wiring layer used in this embodiment is not particularly limited as long as it can exhibit the desired conductivity, but is preferably in the range of 10 μm to 100 μm. It is preferably within the range of 15 μm to 50 μm. This is because the rigidity of the suspension substrate of this aspect can be reduced by being in the above range.

In general, the wiring layer used in this embodiment preferably has a protective plating layer formed of nickel (Ni) or gold (Au) on the surface thereof. This is because the wiring layer can be resistant to corrosion.
The film thickness of the protective plating layer is preferably 5 μm or less, and more preferably in the range of 1 μm to 2 μm.

(4) Suspension substrate 10
The manufacturing method of the suspension substrate of this aspect is particularly limited as long as the metal substrate, the insulating layer, the wiring layer, and the cover layer can be laminated with high accuracy and good adhesion. Instead, a general method for manufacturing a suspension substrate can be used. Specifically, a method similar to that described in “B. Method for manufacturing a suspension substrate” described later can be used. it can.

(5) Applications The use of the suspension substrate according to this aspect is used for a magnetic head suspension of a hard disk drive (HDD), and especially a hard disk that requires less warping even when the rigidity is reduced. It is preferably used for a magnetic head suspension of a drive (HDD).

2. Second Aspect A second aspect of the suspension substrate of the present invention will be described. In the suspension substrate of this aspect, in the suspension substrate described above, the insulating layer forming material and the cover layer forming material are the same non-photosensitive material, and both have a hygroscopic expansion coefficient of 0 /% RH to 30. It is the aspect which exists in the range of * 10 < ^-6 > /% RH.

Such a suspension substrate of this embodiment can be the same as that already shown in FIG.
Here, the insulating layer forming material and the cover layer forming material constituting the insulating layer 2 and the cover layer 4 are the same non-photosensitive material, and both have a hygroscopic expansion coefficient of 0 /% RH to 30 × 10. It is a material in the range of ⁻⁶ /% RH.

According to this aspect, when the hygroscopic expansion coefficient of the non-photosensitive raw material that forms the insulating layer forming material and the cover layer forming material is in the above range, the suspension substrate of this aspect has a low rigidity. However, warpage due to moisture absorption is reduced.
Further, since the insulating layer forming material and the cover layer forming material are made of the same non-photosensitive material, there is no difference in physical property values such as a hygroscopic expansion coefficient between the insulating layer forming material and the cover layer forming material. The warp due to the difference in expansion ratio due to moisture absorption between the insulating layer and the cover layer formed by the layer forming material and the cover layer forming material is eliminated. Further, since the insulating layer forming material and the cover layer forming material are made of the same non-photosensitive material, it is possible to easily adjust the physical properties such as the hygroscopic expansion coefficient, and an expensive solvent or the like. Since it is unnecessary, the cost can be reduced.

The suspension substrate of this aspect includes at least a metal substrate, an insulating layer, a wiring layer, and a cover layer.
Hereinafter, each configuration of the suspension substrate according to this aspect will be described. In addition, about the said metal substrate and a wiring layer, since the thing similar to what was described in the term of said "1. 1st aspect" can be used, description here is abbreviate | omitted.

(1) Insulating layer 2 and cover layer 4
The insulating layer used in this embodiment is formed on the metal substrate and is made of an insulating layer forming material.
The cover layer used in this embodiment is made of a cover layer forming material that is formed on the insulating layer and covers a part of the wiring layer.

The insulating layer forming material and the cover layer forming material used in this embodiment are made of the same non-photosensitive material, and both have a hygroscopic expansion coefficient in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH. Is.
The insulating layer forming material and the cover layer forming material are the same material as long as the type and content of the main chain or substituent of the included polymer are the same. It does not require even the same content.

The hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material used in this embodiment may be in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and in particular, 5 × 10 ⁻⁶ /%. preferably RH～20 × is in the range of ¹⁰ -6 /% RH, and particularly preferably in the range of ^{5 × 10 -6 /% RH~15 ×} 10 -6 /% RH. This is because, by being in the above range, even when the suspension substrate of this aspect is made to have a low rigidity, warpage due to moisture absorption can be reduced.

  The water absorption coefficient of the insulating layer forming material and cover layer forming material used in this embodiment is preferably in the range of 0.01% to 2.5%, and more preferably 0.7% to 1.5%. It is preferable to be within the range. It is because the moisture absorption of the said insulating layer and a cover layer can be decreased by being in the said range, and it can suppress that the said insulating layer and a cover layer do hygroscopic expansion. For this reason, even if it is a case where the residual ratio of the said metal substrate is reduced and the suspension board | substrate of this aspect is made low-rigidity, it can be set as a thing with few curvature. Further, if it is smaller than the above range, the adhesion between the cover layer and the insulating layer may be lowered, and if it is larger than the above range, warpage due to moisture absorption is large.

As the thermal expansion coefficients of the insulating layer forming material and the cover layer forming material used in the present aspect, the thermal expansion coefficient of the suspension substrate of the present aspect of the metal substrate and the insulating layer forming material and the cover layer forming material is The warpage due to the difference may be small, but is preferably in the range of 15 × 10 ⁻⁶ / ° C. to 30 × 10 ⁻⁶ / ° C., and in particular, 15 × 10 ⁻⁶ / ° C. to 25 ×. It is preferably within the range of 10 ⁻⁶ / ° C., and particularly preferably within the range of 15 × 10 ⁻⁶ / ° C. to 20 × 10 ⁻⁶ / ° C. This is because, within the above range, even when the suspension substrate of this embodiment has a low rigidity, warpage due to temperature change can be reduced.

The insulating layer forming material and the cover layer forming material used in this embodiment may have a hygroscopic expansion coefficient of both within the above-described range, and further have an insulating property. Contains materials.
Such an insulating material can be the same as the non-photosensitive insulating material described in the above section “1. First embodiment”, and thus description thereof is omitted here.

  Moreover, the insulating layer forming material and the cover layer forming material used in this embodiment may include additives such as a plasticizer, a surfactant, and an antifoaming agent, as necessary.

  As the insulating layer and the cover layer formed by the insulating layer forming material and the cover layer forming material described above, the same contents as those described in the section “1. First aspect” can be used. The description here is omitted.

(2) Suspension substrate 10
The manufacturing method of the suspension substrate of this aspect is particularly limited as long as the metal substrate, the insulating layer, the wiring layer, and the cover layer can be laminated with high accuracy and good adhesion. Instead, a general method for manufacturing a suspension substrate can be used. Specifically, a method similar to that described in “B. Method for manufacturing a suspension substrate” described later can be used. it can.

(3) Applications The use of the suspension substrate according to this aspect is used for a magnetic head suspension of a hard disk drive (HDD), and in particular, a hard disk that is required to have less warping even when the rigidity is reduced. It is preferably used for a magnetic head suspension of a drive (HDD).

B. Suspension Substrate Manufacturing Method The suspension substrate manufacturing method of the present invention includes a metal substrate, an insulating layer formed on the metal substrate, a wiring layer formed on the insulating layer, and an insulating layer. A method for manufacturing a suspension substrate having a cover layer formed and covering at least a part of the wiring layer, wherein the insulating layer made of an insulating layer forming material is formed in a pattern on the metal substrate A forming step and a cover layer forming step of forming the cover layer made of a cover layer forming material in a pattern on the insulating layer, wherein the insulating layer forming material and the cover layer forming material are different materials, And the hygroscopic expansion coefficient of both is in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and the difference between the two hygroscopic expansion coefficients is in the range of 5 × 10 ⁻⁶ /% RH or less. so And it is characterized in Rukoto.

The manufacturing method of the suspension substrate of the present invention will be described with reference to the drawings. FIG. 2 is a process diagram showing an example of a method for manufacturing a suspension substrate according to the present invention. As shown in FIG. 2 (a), the suspension substrate manufacturing method of the present invention includes a metal substrate layer 1 ', an insulating layer forming layer 2' made of the above insulating layer forming material, and a wiring layer forming layer. After preparing a laminate in which 3 ′ is laminated, a photoresist layer 11 such as a dry film is provided and patterned into a predetermined shape (FIG. 2B). Next, the metal substrate layer 1 ′ and the wiring layer forming layer 3 ′ are patterned by etching, and the photoresist layer 11 is peeled to form the metal substrate 1 and the wiring layer 3 in a pattern (FIG. 2 ( c)). Next, a photoresist layer 11 such as a dry film is provided and patterned into a predetermined shape (FIG. 2D), and after the insulating layer forming layer 2 ′ is patterned by etching (FIG. 2E), the photo layer By peeling off the resist layer 11, the insulating layer 2 is formed in a pattern (FIG. 2F).
Furthermore, the protective plating layer 5 is formed on the surface of the wiring layer 3 by electrolytic plating using the wiring layer 3 as a power feeding layer (FIG. 2G).

  Subsequently, as shown in FIG. 3A, a cover layer forming layer 4 ′ made of the cover layer forming material is formed on the insulating layer 2, and a dry film or the like is further formed on the cover layer forming layer 4 ′. The photoresist layer 11 is provided (FIG. 3B), and the photoresist layer 11 is patterned into a predetermined shape (FIG. 3C). Next, the cover layer forming layer 4 ′ is patterned by etching to form the cover layer 4 (FIG. 3D). Next, the photoresist layer 11 is peeled off to manufacture the suspension substrate 10 (FIG. 3E). In addition, the insulating layer 2 included in the formed suspension substrate 10 has a low rigidity in which the metal substrate 1 is removed to reduce the rigidity, and one surface of the insulating layer 2 is not covered with the metal substrate 1. The formation region 6 is formed.

Here, the insulating layer forming material and the cover layer forming material are different materials, and their hygroscopic expansion coefficients are in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, It is a material in which the difference between the above hygroscopic expansion coefficients is within a range of 5 × 10 ⁻⁶ /% RH or less.
2A to 2C are metal substrate and wiring layer forming steps, and FIGS. 2D to 2F are insulating layer forming steps. Moreover, FIG.2 (g) is a protective plating layer formation process, and Fig.3 (a)-(e) is a cover layer formation process.

  According to the present invention, the insulating layer and the cover layer are formed using a material in which the hygroscopic expansion coefficient of the cover layer forming material and the insulating layer forming material and the difference between the two hygroscopic expansion coefficients are in the above range. By doing so, even when the suspension substrate manufactured by the manufacturing method of the present invention has a low rigidity, warpage due to moisture absorption can be reduced.

  The method for manufacturing a suspension substrate according to the present invention includes at least an insulating layer forming step and a cover layer forming step. Hereafter, each process of the manufacturing method of the board | substrate for suspensions of this invention is demonstrated in detail.

1. Insulating layer forming step The insulating layer forming step in the present invention is a step of forming an insulating layer made of an insulating layer forming material in a pattern on the metal substrate.

The insulating layer forming material used in this step is a material different from the cover layer forming material used in the cover layer forming step described later, and has a hygroscopic expansion coefficient of 0 /% RH to 30 × 10 ⁻⁶ /% RH. And the difference in hygroscopic expansion coefficient from the cover layer forming material described later is in the range of 5 × 10 ⁻⁶ /% RH or less. As such an insulating layer forming material, the characteristics and the materials constituting it can be the same as those described in the above section “A. Suspension substrate”. Omitted.

  In this step, the method of forming the insulating layer in a pattern is not particularly limited as long as the insulating layer made of the above-described insulating layer forming material can be formed in a desired pattern. For example, after the insulating layer forming layer made of the insulating layer forming material is formed on the entire surface of the metal substrate, the insulating layer forming layer 2 ′ is not etched as shown in FIG. A patterned photoresist layer 11 is formed on the region, and the insulating layer forming layer 2 ′ is etched with a predetermined etching solution to form the insulating layer 2 (FIG. 2E), and then FIG. A method of removing the photoresist layer 11 can be given as shown in FIG.

The method for forming the insulating layer forming layer made of the insulating layer forming material is not particularly limited as long as the insulating layer forming layer can be formed with a uniform film thickness. A method of directly forming and forming a forming material may be used. A method of forming a material by dispersing or dissolving the insulating layer forming material in a solvent, applying a liquid insulating layer forming material, and drying the material. May be used.
The coating method is not particularly limited as long as the film thickness of the insulating layer forming layer can be made uniform, and a known method such as a die coating method can be used.

In addition, as a method for forming the patterned photoresist layer, a photoresist layer formed by coating and drying a liquid photosensitive resin, or a dry film resist that is a dry film-like photosensitive resin is photo-cured. A method in which a resist layer bonded to the entire surface of the insulating layer is exposed through a photomask or the like and developed.
In addition, as the photosensitive resin and the exposure / development method, a method generally used for manufacturing a suspension substrate can be used.

  The metal substrate and the formed insulating layer can have the same contents as those described in the above-mentioned section “A. Suspension substrate”, and thus description thereof is omitted here.

2. Cover layer forming step In the cover layer forming step of the present invention, a cover layer made of a cover layer forming material and covering at least a part of the wiring layer is formed in a pattern on the insulating layer formed by the insulating layer forming step. It is a process to do.

The cover layer forming material used in this step is a material different from the insulating layer forming material used in the insulating layer forming step, and has a hygroscopic expansion coefficient of 3 × 10 ⁻⁶ /% RH to 30 × 10 ^−6. The difference in hygroscopic expansion coefficient from the insulating layer forming material is in the range of 5 × 10 ⁻⁶ /% RH or less. As such a cover layer forming material, the characteristics and the material constituting the cover layer forming material can be the same as those described in the above section “A. Suspension substrate”. Omitted.

  In this step, the method for forming the cover layer in a pattern is not particularly limited as long as the cover layer made of the above-described cover layer forming material can be formed in a desired pattern. For example, as shown in FIG. 3 already described, a cover layer forming layer 4 ′ made of a cover layer forming material is formed on the entire surface of the insulating layer 2 formed by the insulating layer forming step (FIG. 3A). ). Next, after forming a patterned photoresist layer 11 in the region not to be etched of the cover layer forming layer 4 ′ (FIGS. 3B to 3C), the cover layer forming layer 4 ′ is formed with a predetermined etching solution. Development is performed by etching to form the cover layer 4 (FIG. 3D). Then, the method of removing the photoresist layer 11 can be mentioned. Here, the region not to be etched is selected so as to overlap at least a part of the wiring layer.

  In this step, in particular, when the cover layer forming material is non-photosensitive, the non-photosensitive cover layer forming layer 4 made of a non-photosensitive cover layer forming material is formed on the entire surface of the insulating layer 2. And a laminate 11A in which a photoresist layer made of a photosensitive resin on the non-photosensitive cover layer forming layer 4 'is formed. Next, the photoresist layer 11 of the laminate 11A is exposed in a pattern, and simultaneously with the development of the photoresist layer 11 exposed in the pattern, the non-photosensitive cover layer forming layer 4 'is developed. Thus, the cover layer 4 is preferably formed in a pattern.

  In the cover layer forming step, the photoresist layer 11 is exposed in a pattern, and simultaneously with the development of the exposed photoresist layer 11, the non-photosensitive cover layer forming layer 4 ′ is developed. By forming the cover layer 4 in a pattern, the number of operations required for forming the cover layer 4 can be reduced.

  The method for forming the cover layer forming layer made of the cover layer forming material is not particularly limited as long as the cover layer forming layer can be formed with a uniform film thickness. The cover layer forming material may be formed as a cover layer forming layer by laminating the entire surface of the insulating layer. The cover layer forming material may be dispersed or dissolved in a solvent to form a liquid cover layer. You may use the method of forming by apply | coating what was used as a material and making it dry.

In this step, it is preferable that the cover layer is formed by using a cover layer forming layer formed by applying a liquid cover layer forming material containing the cover layer forming material. By forming the cover layer using a liquid cover layer forming material containing the cover layer forming material, the cover layer can be easily thinned.
Here, when the cover layer forming material is a photosensitive material, the liquid cover layer forming material is a material containing the photosensitive insulating material or photosensitive monomer and a photopolymerization initiator. Also good.

In addition, as a method for forming the patterned photoresist layer, the same method as that described in the above section “1. Insulating layer forming step” can be used.
The wiring layer and the formed cover layer may have the same contents as those described in the section “A. Suspension substrate”.

3. Suspension Substrate Manufacturing Method The suspension substrate manufacturing method of the present invention only needs to have at least the insulating layer forming step and the cover layer forming step. Usually, the metal substrate is formed to form a metal substrate in a desired pattern. It has a wiring layer forming step of forming the step and the wiring layer in a desired pattern. Moreover, you may have a protective plating layer formation process which forms a protective plating layer in the surface of a wiring layer as needed.

In such a metal substrate forming step and a wiring layer forming step, as a method of forming the metal substrate and the wiring layer, any method can be used as long as the metal substrate and the wiring layer can be accurately formed at desired positions, respectively. Specifically, as in the insulating layer forming step and the cover layer forming step described above, a method of forming a patterned photoresist layer in an unetched region and then etching with a predetermined etching solution can be exemplified. .
Moreover, in the said protective plating layer formation process, as a method of forming a protective plating layer, a protective plating layer can be formed by carrying out electrolytic plating using the said wiring layer as a electric power feeding layer.

  In the present invention, the order of formation of the insulating layer forming step and the cover layer forming step may be any order, depending on the use of the suspension substrate manufactured by the manufacturing method of the present invention. It can be set appropriately.

  The suspension substrate manufactured by the method for manufacturing a suspension substrate according to the present invention is used for a magnetic head suspension of a hard disk drive (HDD), and has little warping even when the rigidity is reduced. It is preferably used for a magnetic head suspension of a hard disk drive (HDD) that is required.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

Hereinafter, the present invention will be described more specifically with reference to examples.
[Production Example 1]
4.0 g (20 mmol) of 4,4′-diaminodiphenyl ether (ODA) and 8.65 g (80 mmol) of paraphenylenediamine (PPD) were put into a 500 ml separable flask, and 200 g of dehydrated N-methyl-2- The mixture was dissolved in pyrrolidone (NMP), and the mixture was stirred while heating by monitoring with a thermocouple so that the liquid temperature was 50 ° C. with an oil bath in a nitrogen stream. After confirming that they were completely dissolved, 29.1 g (99 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) was added thereto gradually over 30 minutes. After completion of the addition, the mixture was stirred at 50 ° C. for 5 hours and then cooled to room temperature to obtain a polyimide precursor solution 1.

また、感光性ポリイミドとするために、ポリイミド前駆体溶液１にニフェジピン（東京化成）を溶液の固形分の３０重量％添加し、感光性ポリイミド前駆体溶液とした。 [Production Examples 2 to 12]
The polyimide precursor was prepared in the same manner as shown in Production Example 1 except that the amount of NMP was adjusted so that the reaction temperature and the solution concentration were 17% by weight to 19% by weight. Body solutions 2 to 12 and a comparative polyimide precursor solution were synthesized.
Pyromellitic dianhydride: PMDA
1,4-Bis (4-aminophenoxy) benzene: 4APB
2,2'-Dimethyl-4,4'-diaminobiphenyl: TBHG
2,2′-Bis (trifluoromethyl) -4,4′-diaminobiphenyl: TFMB

Moreover, in order to set it as the photosensitive polyimide, 30 weight% of the solid content of the solution was added to the polyimide precursor solution 1 to obtain a photosensitive polyimide precursor solution.

[Linear thermal expansion coefficient evaluation] [Hygroscopic expansion coefficient evaluation]
The polyimide precursor solutions 1 to 12 and the comparative polyimide precursor solution 1 were applied to a Upilex S 50S (trade name: Ube Industries) film affixed on glass, and dried on an 80 ° C. hot plate for 10 minutes. Then, it peeled and the film with a film thickness of 15-20 micrometers was obtained. Thereafter, the film was fixed to a metal frame and heat-treated at 350 ° C. for 1 hour in a nitrogen atmosphere (temperature increase rate: 10 ° C./min, natural cooling). Film thickness: 9-15 μm polyimide 1-12 and comparative polyimide 1 Film was obtained.

  The photosensitive polyimide precursor solution 1 was applied to an Upilex S 50S (trade name: Ube Industries) film affixed on glass, dried on a hot plate at 80 ° C. for 10 minutes, and then 365 nm by a high pressure mercury lamp. After exposure to 500 mJ / cm 2 in terms of wavelength illuminance, the film was heated on a hot plate at 180 ° C. for 3 minutes and then peeled off from the film to obtain a film having a thickness of 17 μm. Then, the film was fixed to a metal frame and heat-treated in a nitrogen atmosphere at 350 ° C. for 1 hour (temperature increase rate: 10 ° C./min, spontaneous cooling) to obtain a film of photosensitive polyimide 1 having a thickness of 12 μm.

<Linear thermal expansion coefficient>
The film produced by the above method was cut into a width of 5 mm and a length of 20 mm and used as an evaluation sample. The linear thermal expansion coefficient was measured with a thermomechanical analyzer Thermo Plus TMA8310 (manufactured by Rigaku Corporation). The measurement conditions are as follows: the observation length of the evaluation sample is 15 mm, the heating rate is 10 ° C./min, the tensile load is 1 g / 25000 μm ² so that the weight per cross-sectional area of the evaluation sample is the same, and the temperature is 100 ° C. to 200 ° C. The average linear thermal expansion coefficient between them was defined as the linear thermal expansion coefficient (C.T.E.).

<Humidity expansion coefficient>
The film produced by the above method was cut into a width of 5 mm and a length of 20 mm and used as an evaluation sample. The humidity expansion coefficient was measured by a humidity variable mechanical analyzer Thermo Plus TMA8310 (manufactured by Rigaku Corporation). The temperature is kept constant at 25 ° C., and the sample is first stabilized in a humidity of 15% RH. After maintaining this state for approximately 30 minutes to 2 hours, the humidity of the measurement site is set to 20% RH. Hold the state for 30 minutes to 2 hours until the sample becomes more stable. After that, the humidity is changed to 50% Rh, and the difference between the sample length when it becomes stable and the sample length when it becomes stable at 20% Rh is the change in humidity (in this case 50-20). 30), and the value divided by the sample length was taken as the coefficient of humidity expansion (CHE). The tensile load was 1 g / 25000 μm ² so that the weight per cross-sectional area of the evaluation sample was the same.

この結果より、本発明の湿度膨張係数が小さいほど高湿環境下での基板の反りが小さいことがわかる。 [Substrate warpage evaluation]
Using the above polyimide precursor solution and photosensitive polyimide precursor solution on a SUS304 (metal substrate) with a thickness of 20 μm, a sample was prepared for evaluation of the linear thermal expansion coefficient so that the film thickness after imidation would be 10 μm ± 1 μm. A polyimide film and a photosensitive polyimide film were formed under the same process conditions. Thereafter, the composite substrate has a polyimide film of 10 mm × 50 mm, two SUS patterns with a width of 2 mm on the polyimide, a space of 2 mm from both ends, and an interval of 2 mm, as shown in FIG. It was set as the sample for the board | substrate curvature processed into.
This sample was fixed to a SUS plate with only one of the short ends of the sample with Kapton tape, heated in an oven at 100 ° C. for 1 hour, and then the opposite end in an oven heated to 100 ° C. The distance from the SUS plate was measured. A sample with a distance of 0 to 0.5 mm at that time was evaluated as ◯, a sample with 0.5 mm to 1.0 mm as Δ, and a sample larger than 1.0 mm as ×.
Similarly, this sample is fixed to the SUS plate with only one of the short ends of the sample with Kapton tape, and the sample is placed on the constant temperature and humidity layer at 85 ° C. and 85% Rh for 1 hour. The distance of the part from the SUS plate was measured. A sample with a distance of 0 to 0.5 mm at that time was evaluated as ◯, a sample with 0.5 mm to 1.0 mm as Δ, and a sample larger than 1.0 mm as ×.
These evaluation results are shown in Table 2 below.

From this result, it can be seen that the smaller the humidity expansion coefficient of the present invention, the smaller the warpage of the substrate in a high humidity environment.

(Developability evaluation)
The polyimide precursor solution, the comparative polyimide precursor solution and the photosensitive polyimide precursor solution are applied onto SUS304 (metal substrate) having a thickness of 20 μm, dried on an 80 ° C. hot plate for 10 minutes, and a film thickness of 15 μm ± Films of 1 μm polyimide precursors 1 to 12, comparative polyimide precursor 1 and photosensitive polyimide precursor 1 were obtained.
The film of photosensitive polyimide 1 was then heated on a 180 ° C. hot plate for 3 minutes.
Using these membranes,
A) 1 wt% tetramethylammonium hydroxide (TMAH) aqueous solution,
B) 5 wt% TMAH aqueous solution,
C) 3% by weight TMAH aqueous solution and ethanol mixed at 9: 1,
D) The solubility at 23 ° C. in four types of solutions of 5% by weight TMAH aqueous solution and ethanol mixed at 1: 1 was examined.
The solubility is indicated as “◯” when completely dissolved, and “x” when swelling or undissolved residue is shown in Table 3.
From this result, it can be seen that polyamic acid containing fluorine has poor solubility in an aqueous solution, and development requires a solution containing a large amount of alcohol.

[Example 2]
A first non-photosensitive polyimide was used as an insulating layer forming material on SUS304 (metal substrate) having a thickness of 20 μm, and an insulating layer having a thickness of 10 μm was formed by a coating method. Further, Ni—Cr—Cu serving as a seed layer is coated on the insulating layer by a sputtering method to a thickness of about 300 nm, and this is used as a conductive layer to form a Cu plating layer (metal plating layer) having a thickness of 9 μm by Cu plating. A laminated body of layers was obtained (see FIG. 1A). Using this four-layered laminate, a suspension substrate having low rigidity and fine wiring was produced.

Here, the physical property value of the insulating layer forming material (first non-photosensitive polyimide) has a hygroscopic expansion coefficient of 10.7 × 10 ⁻⁶ /% RH and a thermal expansion coefficient of 21 × 10 ⁻⁶ / ° C.

  Next, a patterned resist was obtained by patterning simultaneously using a dry film so that a jig hole whose positional accuracy is important on the SUS side and a target wiring layer on the Cu plating layer side can be formed. Then, it etched using the ferric chloride liquid, and resist stripping was performed after the etching. Here, the positional accuracy of both surfaces of the SUS side and the wiring layer side can be improved by simultaneously patterning the dry film. The width of the wiring layer formed in a pattern was 20 μm, and the distance between the wiring layers was 20 μm. It is considered that the miniaturization of wiring greatly contributes to the fact that there is no anchor shape in the wiring layer and that a highly sensitive DFR resist is used.

  Next, a non-photosensitive polyimide-based liquid cover layer forming material is coated with a die coater, dried, resist-engraved, and the cover layer forming material is etched at the same time as development, and then cured to form a cover layer forming material (second A cover layer made of non-photosensitive polyimide) was obtained. The film thickness of the cover layer after curing was 5 μm on the wiring layer. By forming such a cover layer, it is possible to control warpage and reduce rigidity, and to protect the wiring pattern layer.

In addition, the physical property value of the cover layer forming material (second non-photosensitive polyimide) for forming the cover layer herein has a hygroscopic expansion coefficient of 8.0 × 10 ⁻⁶ /% RH, and a thermal expansion coefficient of It was 17 × 10 ⁻⁶ / ° C. Further, the physical property values of the insulating layer forming material (first non-photosensitive polyimide) are a hygroscopic expansion coefficient of 10.7 × 10 ⁻⁶ /% RH and a thermal expansion coefficient of 21 × 10 ⁻⁶ / ° C. A material having a small difference in physical property values between the insulating layer forming material and the cover layer forming material was used.

  Next, a 10 μm-thick polyimide (insulating layer) was resist-engraved and etched using an organic alkaline etching solution to obtain a patterned insulating layer. Thereafter, Au plating having a thickness of 2 μm was performed on the exposed wiring pattern layer to form a protective plating portion. In the present invention, the wiring cover is first implemented, and Au plating can be performed only on the portion not covered with the cover layer, and a great effect can be obtained in reducing the rigidity and reducing the amount of Au.

Next, in order to perform the outer shape processing of SUS, resist plate making was performed again, and only the SUS side was etched. Finally, solder bumps were formed by screen printing using a lead-free solder paste. The suspension substrate thus obtained has a warp of 0.5 mm at room temperature and is maintained for 1 hour in an environment of high temperature and high humidity (85 ° C., 85% RH). The warpage was 0.5 mm and the warpage could be suppressed.
The warpage is measured by cutting one piece of a suspension board having a length of 20 mm from a processed sheet and placing it on a surface plate with the copper wiring surface as an upper surface, and extending vertically from the surface of the surface plate to the tip of the suspension substrate. The distance was measured with a high precision ruler, and the value of the warp was obtained.

[Comparative example]
As the cover layer forming material, a third non-photosensitive polyimide having a physical property value of 23 × 10 ⁻⁶ / ° C. and a hygroscopic expansion coefficient of 31 × 10 ⁻⁶ /% RH is used as the insulating layer forming material. A suspension substrate was prepared in the same manner as in the example except that a photosensitive polyimide having a thermal expansion coefficient of 200 × 10 ⁻⁶ / ° C. and a hygroscopic expansion coefficient of 155 × 10 ⁻⁶ /% RH was used. did.
The resulting suspension substrate has a warp of 2.0 mm at room temperature and a warp of 2.0 mm after being held for 1 hour in an environment of high temperature and high humidity (85 ° C., 85% RH). The warpage could not be sufficiently suppressed.

Second Embodiment Hereinafter, a method for manufacturing a suspension substrate according to a second embodiment of the present invention will be described in detail.

  The method for manufacturing a suspension substrate according to the present invention includes a laminate preparation step of preparing a laminate in which a metal substrate, an insulating layer, a seed layer, and a metal plating layer are arranged in this order, and a surface of the metal substrate and the metal plating layer. Forming a pattern resist on the surface and performing etching, thereby forming a jig hole in the metal substrate, and forming a wiring pattern layer in the metal plating layer; and It is characterized by having.

  According to the present invention, a suspension substrate having a low rigidity can be obtained by using the above laminate. In the first metal etching step, jig holes and punch holes are formed in the metal substrate, but most of the metal substrate is not etched. Therefore, the insulating layer can be etched in a state where the rigidity of the laminated body is maintained high, and deformation of the laminated body during processing can be suppressed during conveyance between the processes. The suspension substrate obtained by the present invention can be used for a magnetic head suspension of a hard disk drive (HDD), for example.

  Next, a method for manufacturing a suspension substrate according to the present invention will be described with reference to the drawings. 4 and 5 are explanatory views for explaining an example of a method for manufacturing a suspension substrate according to the present invention. In the present invention, first, as shown in FIG. 4A, a laminate 30 in which a metal substrate 21, an insulating layer 22, a seed layer 23, and a metal plating layer 24 are arranged in this order is prepared (laminate preparation step). ). Here, a laminate 30 having SUS as the metal substrate 1, polyimide as the insulating layer 22, Ni—Cr—Cu sputtering layer as the seed layer 23, and Cu plating layer as the metal plating layer 24 is provided. prepare.

  Next, a metal etching resist is made on the laminate 30. Specifically, a resist layer for metal etching is provided on both surfaces of the laminate 30, and resists 31 and 32 patterned as shown in FIG. 4B are formed by a photolithography method. In this case, a resist 31 is formed on the wiring side with a pattern corresponding to the target wiring pattern layer, and a resist 32 is formed on the substrate side with a pattern excluding the jig hole portion. Further, the resist 32 is formed so as to exclude the flying lead portion in addition to the jig hole.

  Then, as shown in FIG. 4C, the metal substrate 21 and the metal plating layer 24 are etched using a chemical etching solution, and the resists 31 and 32 are peeled off. Thereby, the wiring pattern layer 24a is formed from the metal plating layer 24, and the jig hole 21a is formed in the metal substrate 21 (first metal etching step). In the figure, reference numeral 21b denotes a hole for forming the flying lead portion.

  Next, as shown in FIG. 4D, a cover layer 25 is formed from above the wiring pattern layer 24a using a liquid cover material (cover layer forming step). At this time, the cover layer 25 is formed so that a part 24b of the surface of the wiring pattern layer 24a is exposed, and a protective plating portion described later is formed on the exposed portion.

  Next, a resist for etching the insulating layer 22 is made. Specifically, a resist layer for polyimide etching is provided on both surfaces of the laminate 30, and resists 33 and 34 patterned as shown in FIG. 4E are formed by photolithography. In this case, a resist 33 is formed on the wiring side so as to cover the wiring pattern layer 24a and the cover layer 25, and a resist 34 is formed on the substrate side so as to exclude the corresponding portion of the hole 21b in the flying lead portion. .

  Then, as shown in FIG. 4F, the insulating layer 22 is etched using an organic alkaline solution as an etching solution, and the resists 33 and 34 are peeled off. Thereby, the wiring pattern layer 24a and the cover layer 25 are integrally formed on the metal substrate 21 via the insulating layer 22 (insulating layer etching step). Further, the metal substrate 21 is in a state in which the jig hole 21a and the flying hole 21b are formed. Note that the insulating layer 22 may be processed by plasma etching.

  Next, as shown in FIG. 5G, a protective plating portion 26 is formed by performing Au plating or Ni—Au plating on a portion where the wiring pattern layer 24a is exposed (protective plating portion forming step).

  Next, in order to perform the outer shape processing of the metal substrate 21, a metal etching resist is made on both surfaces of the laminate 30. In the present invention, “performing the outer shape of the metal substrate” means that the region of the metal substrate that has not been processed in the first metal etching step is processed according to the shape of the target suspension substrate. Specifically, a resist layer for metal etching is provided on both surfaces of the laminate 30, and resists 35 and 36 patterned as shown in FIG. 5H are formed by a photolithography method. In this case, a resist 35 is formed on the wiring side so as to cover the entire surface, and a resist 36 patterned in accordance with the target outer shape is formed on the substrate side.

  Then, as shown in FIG. 5I, the metal substrate 21 is etched using a chemical etching solution, and the resists 35 and 36 are peeled off. Thereby, a suspension substrate having a desired shape is obtained (second metal etching step). Thereafter, as shown in FIG. 5J, solder bump portions 27 are formed by printing on the terminal portions of the wiring pattern layer 24a as necessary. In the figure, A is a terminal part for forming a bump, B is a flying lead part, C is a wiring part, and may have a metal substrate 21 as necessary.

The manufacturing method of the suspension substrate of the present invention usually includes a laminate preparation step and a first metal etching step. Furthermore, it is preferable to have a cover layer forming step, an insulating layer etching step, a protective plating portion forming step, a second metal etching step, and a solder bump forming step, which will be described later.
Hereinafter, the manufacturing method of the suspension substrate according to the present invention will be described step by step.

1. Laminated body preparation process First, the laminated body preparation process in this invention is demonstrated. The laminate preparation step in the present invention is a step of preparing a laminate in which a metal substrate, an insulating layer, a seed layer, and a metal plating layer are arranged in this order.

  In the present invention, a suspension substrate having a low rigidity can be obtained by using a laminate having the above layer structure. In general, a five-layer laminate has been used as a raw material for obtaining a suspension substrate. Specifically, as shown in FIG. 6A, SUS as the metal substrate 41, thermoplastic polyimide (TPI) as the adhesive layer 42, polyimide as the insulating layer 43, and TPI as the adhesive layer 44. And a five-layer laminate having Cu as the wiring pattern forming layer 45 has been used.

  However, this laminated body is usually formed by bonding and laminating rolled copper or the like, which is spring copper, with a press. Since rolled copper is used, it has not been possible to reduce the thickness and reduce the rigidity. Furthermore, since the above five-layer laminate is formed by pressing each constituent member, the pattern of the roughened surface of the wiring pattern forming layer (for example, rolled copper) is transferred to the insulating layer (for example, polyimide). . As a result, there has been a problem that the surface of the insulating layer is roughened, and the roughened surface is a factor that hinders fine wiring processing.

  On the other hand, in the laminate used in the present invention, for example, as shown in FIG. 6B, the metal substrate 41, the insulating layer 22, the seed layer 23, and the metal plating layer 24 are usually arranged in this order. A stack 30 of layers. Since the metal plating layer of this four-layer laminate is formed by an electrolytic plating method or the like, it can be made thinner and less rigid than conventional rolled copper or the like. A fine wiring pattern layer can also be formed. Furthermore, since the metal plating layer of the four-layer laminate is formed by an electrolytic plating method or the like, the surface of the insulating layer is roughened as in the case of the five-layer laminate described above. There is nothing. Therefore, there is an advantage that the problem of remaining foreign matter does not occur.

Next, the structural member of the laminated body used for this invention is demonstrated. The laminated body used for this invention has a metal substrate, an insulating layer, a seed layer, and a metal plating layer normally.
The material for the metal substrate is not particularly limited as long as it has electrical conductivity and appropriate springiness, and examples thereof include SUS. The film thickness of the metal substrate is, for example, preferably in the range of 10 μm to 30 μm, and more preferably in the range of 15 μm to 25 μm. If the metal substrate is too thin, the mechanical strength may be reduced, and if the metal substrate is too thick, it is difficult to reduce the rigidity of the suspension substrate.

  The material of the insulating layer is not particularly limited as long as it has insulating properties, and examples thereof include polyimide (PI). The thickness of the insulating layer is, for example, preferably in the range of 5 μm to 30 μm, more preferably in the range of 5 μm to 20 μm, and particularly preferably in the range of 5 μm to 10 μm. This is because if the insulating layer is too thin, sufficient insulation may not be exhibited. If the insulating layer is too thick, it is difficult to reduce the rigidity of the suspension substrate.

  The material of the seed layer is not particularly limited as long as it can improve the adhesion between the insulating layer and the metal plating layer, and examples thereof include Ni, Cu, Cr, and alloys thereof. The seed layer is preferably a layer formed by a sputtering method. The film thickness of the seed layer is not particularly limited as long as desired adhesion can be obtained, but is usually in the range of 10 nm to 300 nm.

  The material for the metal plating layer is not particularly limited as long as it has good electrical conductivity, and examples thereof include copper (Cu). The film thickness of the metal plating layer is, for example, preferably in the range of 6 μm to 18 μm, and more preferably in the range of 8 μm to 12 μm. This is because if the metal plating layer is too thin, the mechanical strength may decrease, and if the metal plating layer is too thick, it is difficult to reduce the rigidity of the suspension substrate.

  The metal plating layer can be formed by a general plating method. In particular, in the present invention, the metal plating layer is preferably formed by an electrolytic plating method. This is because the metal plating layer can be formed with high accuracy. In the present invention, the difference between the maximum film thickness portion and the minimum film thickness portion of the metal plating layer is, for example, 2 μm or less, preferably 1.6 μm or less.

  In the present invention, the wiring pattern layer is formed by a method called a subtractive method in which the wiring pattern layer is formed by etching the metal plating layer. On the other hand, a method of forming a wiring pattern layer by an additive method is known. Specifically, a predetermined resist pattern is formed on the insulating layer, and the surface of the insulating layer on which the resist pattern is not formed is formed. In this method, a wiring pattern layer is formed by an electrolytic plating method or the like. By the way, when the wiring pattern layer is formed by the above-described additive method, there is a problem that the electric field becomes non-uniform due to the density of the resist pattern and the film thickness of the wiring pattern layer becomes large. On the other hand, when the wiring pattern layer is formed by the subtractive method as in the present invention, the film thickness of the wiring pattern layer is defined by the film thickness of the metal plating layer of the laminate that is the raw material. There is an advantage that the variation in film thickness is small.

  The method for forming the laminate used in the present invention is not particularly limited as long as it is a method capable of obtaining the above laminate. For example, a polyimide precursor is formed on the surface of SUS as a metal substrate. A method of forming an insulating layer made of polyimide by applying and heat-treating the containing coating solution, then forming a seed layer by a sputtering method, and finally forming a metal plating layer made of Cu plating by an electrolytic plating method Etc.

2. First Metal Etching Step Next, the first metal etching step in the present invention will be described. In the first metal etching step of the present invention, a patterned resist is formed on the surface of the metal substrate and the surface of the metal plating layer, and etching is performed to form a jig hole in the metal substrate. And it is the process of forming a wiring pattern layer in the said metal plating layer.

  Specifically, as shown in FIGS. 4B and 4C described above, patterned resists 31 and 32 are formed on the surface of the metal substrate 41 and the surface of the metal plating layer 24, and the metal substrate. In this step, a jig hole 21a is formed on the surface of 41 and the metal plating layer 24 is processed into a wiring pattern layer 24a. In the present invention, if necessary, the hole 21b for forming the flying lead portion may be formed simultaneously with the jig hole 21a. In addition, when double-sided connection like a flying lead part is not performed and single-sided connection is sufficient, it is not necessary to form the punching hole 21b.

  In the present invention, jig holes and punch holes are formed in the metal substrate in the first metal etching step, but most of the metal substrate is not etched. Therefore, the insulating layer can be etched in a state where the rigidity of the laminated body is maintained high, and deformation of the laminated body during processing can be suppressed during conveyance between the processes. In the present invention, the processing of the metal substrate other than the jig hole is usually performed in a second metal etching step described later.

  In the present invention, jig holes are formed in the metal substrate when the metal plating layer is processed into the wiring pattern layer. Thereby, first, the relative positional relationship between the jig hole and the wiring pattern layer can be determined. In the present invention, the “jig hole” refers to a hole for fixing the laminated body with a jig, and various alignments are performed based on the jig hole. In the present invention, the laminated body can be processed with high accuracy by unifying the alignment reference to the jig hole. The shape of the jig hole varies depending on the shape of the jig used, but is usually a circle or a long hole. Although the diameter of a jig hole is not specifically limited, For example, it exists in the range of 0.5 mm-3 mm.

  In the first metal etching step, at least a jig hole is formed in the metal substrate, and if necessary, a hole for the flying lead is simultaneously formed. On the other hand, if the metal substrate of the laminated body after completion of the first metal etching step maintains a certain degree of rigidity, it is possible to prevent the laminated body being processed from being deformed during conveyance. On the surface of the metal substrate, when the area of the region processed by the first metal etching step is SA and the total area is ST, SA / ST is, for example, 0.6 or less, especially 0.01-0. It is preferable to be within the range of 5.

  On the other hand, on the wiring side, a wiring pattern layer is formed by etching the metal plating layer. Since the metal plating layer used in the present invention is usually thinner than conventional rolled copper or the like, a fine wiring pattern layer can be formed. The width of the wiring pattern is, for example, preferably 10 μm or more, and more preferably in the range of 15 μm to 25 μm. On the other hand, the interval between adjacent wiring patterns is, for example, preferably 10 μm or more, and more preferably 15 μm to 25 μm.

  The resist used in the present invention may be a solid resist or a liquid resist. However, since the number of steps is increased, a solid resist is preferable. Specifically, it is preferable to use a dry film resist (DFR). This is because a fine wiring pattern layer can be obtained.

  The method for forming the patterned resist on the surface of the metal substrate and the surface of the metal plating layer is not particularly limited, and a general method can be used. Specifically, a method may be mentioned in which a resist is arranged on the surface of the metal substrate and the surface of the metal plating layer, developed in a desired pattern, and then developed.

  Examples of the method for etching the metal substrate and the metal plating layer include wet etching. Furthermore, it is preferable that the etching solution used for wet etching is appropriately selected according to the material of the metal substrate and the metal plating layer to be used. For example, when the metal substrate is SUS, a ferric chloride etching solution can be used. When the metal plating layer is a copper plating layer, a ferric chloride etching solution or a copper chloride etching solution can be used. In the present invention, after the patterned resist is formed, the metal substrate and the metal plating layer may be etched separately, but it is preferable to simultaneously etch the metal substrate and the metal plating layer. This is because the number of processes is reduced.

3. Cover Layer Formation Step Next, the cover layer formation step in the present invention will be described. The cover layer forming step in the present invention is a step of forming a cover layer having a wiring pattern layer exposed opening through which a part of the surface of the wiring pattern layer is exposed using a liquid cover material.

  Specifically, as shown in FIG. 4D described above, this is a step of forming a cover layer 25 having a wiring pattern layer exposed opening 25a through which a part 24b of the surface of the wiring pattern layer 24a is exposed. A protective plating portion to be described later is formed on the surface of the wiring pattern layer 24a exposed through the wiring pattern layer exposure opening.

In the present invention, by forming the cover layer before etching the insulating layer, the liquid cover material can be prevented from flowing into the jig hole or the like. Thereby, a cover layer having a uniform film thickness can be formed. FIG. 7 is an explanatory diagram for explaining a general cover layer forming step. For the sake of convenience, the description of the seed layer is omitted, and the description of some reference numerals overlapping with those in FIG. 4 is also omitted. Conventionally, as shown in FIG. 7A, before the cover layer is formed, the insulating layer 22 has already been etched, so that the jig hole 21b has penetrated. Therefore, when forming a cover layer using a liquid cover material, it is necessary to arrange the outflow prevention material 51 under the jig hole 21b (FIG. 7B), and the outflow prevention material 51 is arranged. Even in this case, the liquid cover material 25 ′ may flow into the jig hole 21 b (FIG. 7C). As a result, the thickness of the obtained cover layer 25 becomes non-uniform, and there is a problem that a region of the wiring pattern layer 24a not covered by the cover layer 25 is generated (FIG. 7D).
In addition, the film thickness of the cover layer formed in the wiring pattern layer in the place where many jig holes or punch holes are formed, and the cover layer formed in the place where the jig holes or punch holes are not formed. There is a problem that the difference in film thickness becomes large.
In the experimental example in which the liquid cover layer was formed by the above-described general method, when the film thickness of the cover layer after drying was measured, a difference in film thickness of 2.9 μm was observed on average and the sample was non-uniform (sample) (Equation 8).
In particular, when the film thickness is formed to be thin, for example, 2.8 to 3.5 μm, the cover layer formed on the wiring layer near the jig hole is further thinned to 0.6 to 1.5 μm, An area of the wiring pattern layer where the cover layer was not covered occurred.
In addition, when the cover layer is formed with a dry film instead of a liquid cover material, the insulating film was etched first, so the dry film fell into the jig hole and formed in the wiring part near the jig hole. The cover layer to be formed has a problem that the film thickness becomes thinner than other regions.
In the experimental example in which the cover layer was formed by the above-described general method using this dry film, the thickness of the film layer was thicker than that of the liquid cover material, so that the area of the wiring pattern layer not covered with the cover layer did not occur. However, the difference between the film thickness of the cover layer of the wiring pattern layer near the jig hole and the film thickness of the cover layer of the wiring part away from the jig hole was an average of 3.4 μm, which was uneven.

  On the other hand, in the present invention, the liquid cover material can be prevented from flowing in by forming the cover layer before the insulating layer is etched. Here, FIG. 8 is an explanatory view illustrating the cover layer forming step in the present invention. For the sake of convenience, the description of the seed layer is omitted, and the description of some reference numerals overlapping with those in FIG. 4 is also omitted. In the present invention, as shown in FIG. 8A, the cover layer is formed before the insulating layer 22 is etched. Unlike the general method, the jig hole 21b is not penetrating. Therefore, the liquid cover material 25 ′ does not flow into the jig hole 21 b (FIG. 8B), the cover layer 25 having a uniform film thickness can be obtained, and the wiring pattern layer not covered by the cover layer 25. It is possible to prevent the occurrence of the region 24a (FIG. 8C). Then, after forming the cover layer 25, the insulating layer 22 is etched (FIG. 8D).

  The liquid cover material used in the present invention contains at least a cover layer forming resin. Furthermore, you may contain the solvent which dissolves the resin for cover layer formation as needed. Examples of the cover layer forming resin include a polyimide resin and an epoxy resin. The resin for forming the cover layer may be a photosensitive resin or a non-photosensitive resin, but among them, the non-photosensitive resin is preferable. In this case, a thin cover layer can be formed.

The liquid cover material preferably has a low viscosity. In this case, a thin cover layer can be obtained. The viscosity of the liquid cover material is, for example, preferably in the range of 500 cP to 5000 cP at room temperature, and more preferably in the range of 500 cP to 1000 cP.
The thickness of the cover layer formed on the wiring pattern layer is not particularly limited, but is preferably in the range of 3 μm to 20 μm, and more preferably in the range of 5 μm to 10 μm.
In the experimental example in which the insulating layer was etched after the cover layer was formed using the liquid cover material of the present invention, when the cover layer provided on the wiring pattern layer after drying was formed thicker, An average of 6.4 μm at the wiring pattern portion near the jig hole and an average of 6.7 μm at the wiring pattern portion other than the vicinity of the jig hole. The difference in film thickness is 0.3 μm, and a uniform film thickness can be accurately formed. (8 samples).
When the cover layer is formed thin, the average is 3.6 μm in the wiring pattern near the jig hole 21b (see FIG. 8), and the average is 3.8 μm in the wiring pattern other than the vicinity of the jig hole. The film thickness difference was 0.2 μm, and a uniform film thickness could be formed with high precision (8 samples).
For this reason, in the present invention, the difference between the maximum film thickness portion and the minimum film thickness portion of the cover layer on the wiring is, for example, 1.3 μm or less, preferably 1.0 μm or less.
Here, the wiring pattern portion in the vicinity of the jig hole 21b is not necessarily limited to only the jig hole, and may be a portion in which an insulating layer in which a hole or a wiring pattern layer is formed is etched. Further, the wiring pattern portion other than the vicinity of the jig hole may be a portion where the insulating layer of the wiring pattern portion is not etched.
In the present invention, the film thickness of the cover layer can be formed accurately and uniformly over the entire area of the wiring pattern portion. In the conventional method, the film thickness of the cover layer to be formed has a large variation, so that it cannot be formed thin. However, in the present invention, a thin film thickness can be formed with high accuracy.
In the present invention, by reducing the film thickness, the material can be reduced and the manufacturing cost of the suspension base material can be suppressed. In addition, since the magnetic head suspension in which the slider is mounted on the suspension base of the present invention can be reduced in weight, the inertial force for driving the suspension is reduced, and a power-saving HDD device can be provided.

  The method for forming the cover layer is not particularly limited as long as it uses a liquid cover material. For example, when the liquid cover material contains a photosensitive resin, a method of applying the liquid cover material so as to cover the wiring pattern layer, drying, exposing and developing, and the like can be exemplified. On the other hand, when the liquid cover material contains a non-photosensitive resin, the following method can be employed. That is, first, a liquid cover material is applied so as to cover the wiring pattern layer, and dried to form a non-photosensitive resin layer. Next, a photosensitive resin layer is formed on the non-photosensitive resin layer, and the photosensitive resin layer is exposed in a pattern. Next, simultaneously with the development of the exposed photosensitive resin layer, the non-photosensitive resin layer is etched, and finally the photosensitive resin layer is peeled off. By this method, a thin cover layer can be obtained.

4). Insulating Layer Etching Step Next, the insulating layer etching step in the present invention will be described. The insulating layer etching step in the present invention is a step of etching the insulating layer after forming the cover layer.

  Specifically, as shown in FIG. 4E and FIG. 4F described above, patterned resists 33 and 34 for polyimide etching are formed on both surfaces of the laminate 30, and an etching solution is used. This is a step of etching the insulating layer 22. By this step, the jig hole 21a penetrates for the first time. Further, if necessary, the hole 21b of the flying lead portion may be formed at the same time.

  In the present invention, either the insulating layer etching step or the protective plating portion forming step to be described later may be performed first. For example, a suspension substrate having a flying lead portion that can be connected on both sides is used. When forming, usually, an insulating layer etching step is first performed, and then a protective plating portion forming step is performed. This is because it is necessary to form a hole in the flying lead portion. On the other hand, when the double-sided connection as in the flying lead portion is not performed and the single-sided connection is sufficient, either of the insulating layer etching step and the protective plating portion forming step may be performed first.

  In the present invention, the etching pattern of the insulating layer is preferably set as appropriate according to the shape of the target suspension substrate. As a method for etching the insulating layer, as described above, a method of forming a patterned resist in a region not to be etched, and then etching the insulating layer with a predetermined etching solution can be used. In the present invention, it is preferable to use a dry film resist. In addition, the insulating layer may be etched by plasma etching or the like.

5. Next, the protective plating part forming step in the present invention will be described. The protective plating portion forming step in the present invention is a step of forming a protective plating portion on the surface of the wiring pattern layer exposed through the wiring pattern layer exposure opening.

  Specifically, as shown in FIG. 5G described above, the protective plating portion is formed on the surface of the part 24b of the wiring pattern layer 24a exposed from the wiring pattern layer exposed opening 25a formed by the cover layer forming step. 26 is formed.

  In the present invention, first, a cover layer is formed, and a protective plating portion is formed only on the surface of the wiring pattern layer exposed from the wiring pattern layer exposed opening of the cover layer, thereby obtaining a low-rigidity suspension substrate. Can do. In general, the protective plating portion is formed before the cover layer is formed. For example, as shown in FIG. 9A, the protective plating portion 26 is formed on the surface and side surfaces of the wiring pattern layer 24a. For this reason, there has been a problem that the suspension substrate cannot be sufficiently reduced in rigidity.

  On the other hand, in the present invention, by forming a cover layer before forming the protective plating portion, for example, as shown in FIG. 9B, only a necessary portion of the surface of the wiring pattern layer 24a is protected. The plating part 26 can be formed, and the rigidity of the suspension substrate can be sufficiently reduced. In FIG. 9, the description of some of the reference numerals overlapping those in FIG. 4 is omitted.

  The material of the protective plating portion used in the present invention is not particularly limited as long as it can prevent corrosion of the wiring pattern layer and the like. For example, nickel (Ni), gold (Au), etc. Among them, gold (Au) is preferable. It is because it is excellent in corrosion resistance.

The film thickness of the protective plating portion is, for example, 5 μm or less, and preferably in the range of 1 μm to 2 μm. It is because corrosion of a wiring pattern layer etc. can be prevented effectively because it is the said range.
The protective plating portion can be formed by a general plating method. Especially in this invention, it is preferable that the said protective plating part is formed by the electroplating method. This is because the protective plating portion can be formed with high accuracy.

6). Second Metal Etching Step Next, the second metal etching step in the present invention will be described. The 2nd metal etching process in this invention is a process of performing the external shape process of the said metal substrate after the said insulating layer etching process and the said protective plating part formation process.

  Specifically, as shown in FIG. 5 (h) and FIG. 5 (i) described above, patterned resists 35 and 36 for metal etching are formed on both surfaces of the laminate 30, and metal is etched using an etching solution. This is a step of performing the external shape processing of the substrate 41.

  In the present invention, jig holes and punch holes are formed in the metal substrate in the first metal etching step, but most of the metal substrate is not etched. Therefore, the insulating layer can be etched in a state where the rigidity of the laminated body is maintained high, and deformation of the laminated body during processing can be suppressed during conveyance. Thereafter, after the etching of the insulating layer or the like is finished, the unprocessed metal substrate is etched according to a predetermined shape, whereby a low-rigidity suspension substrate can be manufactured with a high yield.

  The method for etching the metal substrate and the kind of the etching solution used are the same as the contents described in the above “1. First metal etching step”, and thus the description thereof is omitted here.

7). Solder bump part formation process In this invention, you may perform the solder bump part formation process which forms a solder bump part on the protective plating part of a terminal part after a 2nd metal etching process. The solder bump portion forming step is a step of forming the solder bump portion 27 on the surface of the protective plating portion 26 of the terminal portion A as shown in FIG.

  The solder used to form the solder bump portion can be roughly classified into lead-containing solder and lead-free solder. Among these, in the present invention, it is preferable to use lead-free solder. This is because the load on the environment can be reduced. Specific examples of the lead-free solder include Sn—Sb, Sn—Cu, Sn—Cu—Ni, Sn—Ag, Sn—Ag—Cu, Sn—Ag—Cu—Bi, Examples thereof include Sn—Zn, Sn—Ag—In—Bi, Sn—Zn, Sn—Bi, Sn—In, and Sn—Sb solders.

  The method for forming the solder bump portion is not particularly limited as long as it is a method capable of forming a desired solder bump portion, and examples thereof include a screen printing method, a dispensing method, an ink jet method, and the like. Screen printing is preferred.

8). Others As described in the above “3. Cover layer forming step”, in the present invention, the liquid cover material is prevented from flowing into the jig hole by forming the cover layer before etching the insulating layer. can do. From this point of view, in the present invention, the suspension has a laminate preparation step, a first metal etching step, a cover layer forming step, an insulating layer etching step, and a second metal etching step. The manufacturing method of the board | substrate can be provided. Since each process is the same as the above-mentioned content, description here is abbreviate | omitted.
In this invention, it may replace with the said cover layer formation process and may perform the dry cover layer formation process which forms a cover layer using the dry film for cover layer formation. By forming a cover layer before etching the insulating layer, when the cover layer forming dry film is laminated on the wiring pattern layer, the cover layer forming dry film flows into a jig hole or the like. It is because it can prevent. This is because a cover layer having a uniform film thickness can be formed. Furthermore, the film thickness of the cover layer in the suspension substrate can be made uniform.
In the dry cover layer forming step, the method for forming the cover layer may be a method using a dry film for forming a cover layer. Specifically, after the cover layer forming dry film is disposed so as to cover the surface of the wiring pattern layer, it is laminated by thermocompression bonding. Then, the method of exposing and developing the laminated dry film for cover layer formation can be mentioned.
Here, the exposure and development methods can be the same as those described in the above section “3. Cover layer forming step”. Moreover, as the dry film for forming the cover layer, those generally used for manufacturing a suspension substrate can be used.
Moreover, in this invention, it may replace with the said insulating layer etching process as needed, and may perform the insulating layer etching process before cover layer formation implemented before formation of the said cover layer.

  Further, as described in the above “5. Protection plating portion forming step”, in the present invention, a cover layer is first formed, and only on the surface of the wiring pattern layer exposed from the wiring pattern layer exposed opening of the cover layer. By forming the protective plating portion, a suspension substrate with low rigidity can be obtained. From this point of view, the present invention is characterized by having a laminate preparation step, a first metal etching step, a cover layer forming step, a protective plating portion forming step, and a second metal etching step. A method of manufacturing a suspension substrate can be provided. Since each process is the same as the above-mentioned content, description here is abbreviate | omitted.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the technical idea described in the claims of the present invention has substantially the same configuration and exhibits the same function and effect regardless of the case. It is included in the technical scope of the invention.

Hereinafter, the present invention will be described more specifically with reference to examples.
[Example 1]
A polyimide (insulating layer) with a thickness of 10 μm is formed on a SUS304 (metal substrate) with a thickness of 20 μm by a coating method, and Ni—Cr—Cu serving as a seed layer is further formed on the insulating layer by a sputtering method. Coating was performed with 300 nm, and this was used as a conductive layer to form a 9 μm thick Cu plating layer (metal plating layer) by Cu plating to obtain a four-layer laminate (see FIG. 4A). Using this four-layered laminate, a suspension substrate having low rigidity and fine wiring was produced.

  First, a patterned resist was obtained by patterning simultaneously using a dry film so that a jig hole whose positional accuracy was important on the SUS side and a desired wiring pattern layer on the Cu plating layer side could be formed. Then, it etched using the ferric chloride liquid, and resist stripping was performed after the etching (refer to the first metal etching step, FIGS. 4B and 4C). Here, by positioning the dry film at the same time, it is possible to improve the positional accuracy of both surfaces on the SUS side and the wiring pattern layer side. In addition, the width | variety of the copper wiring formed in the wiring pattern layer was 20 micrometers, and the space | interval of copper wiring was 20 micrometers. It is considered that the miniaturization of the wiring greatly contributes to the fact that there is no anchor shape in the wiring pattern layer and that a highly sensitive DFR resist is used.

  Next, a non-photosensitive polyimide-based liquid cover material was coated with a die coater, dried, resist-engraved, the liquid cover material was etched simultaneously with development, and then cured to obtain a cover layer (FIG. 4D). )reference). The film thickness of the cover layer after curing was 5 μm on the wiring. By forming such a cover layer, it is possible to control warpage and reduce rigidity, and to protect the wiring pattern layer.

  Next, a 10 μm-thick polyimide (insulating layer) was resist-engraved and etched using an organic alkaline etching solution to obtain a patterned insulating layer (see FIGS. 4E and 4F). Thereafter, the exposed wiring pattern layer was Au plated with a thickness of 2 μm to form a protective plating portion (see FIG. 5G). In the present invention, the wiring cover is first implemented, and Au plating can be performed only on the portion not covered with the cover layer, and a great effect can be obtained in reducing the rigidity and reducing the amount of Au.

  Next, in order to perform the outer shape processing of SUS, resist plate making was performed by the same method as the first metal etching step described above, and only the SUS side was etched (second metal etching step, FIG. 5 (h)). (See (i)). Finally, after the second metal etching step, solder bumps were formed by screen printing using a lead-free solder paste (FIG. 5 (j)). The suspension substrate thus obtained had a lower rigidity and finer wiring than conventional products.

It is a schematic sectional drawing which shows an example of the board | substrate for suspensions by the 1st Embodiment of this invention. It is process drawing explaining an example of the manufacturing method of the board | substrate for suspensions of this invention. It is process drawing explaining an example of the manufacturing method of the board | substrate for suspensions of this invention. It is explanatory drawing explaining an example of the manufacturing method of the board | substrate for suspensions by the 2nd Embodiment of this invention. It is explanatory drawing explaining an example of the manufacturing method of the board | substrate for suspensions of this invention. It is a schematic sectional drawing explaining the laminated constitution of a laminated body. It is explanatory drawing explaining a general cover layer formation process. It is explanatory drawing explaining the cover layer formation process in this invention. It is explanatory drawing explaining a protective plating part. It is a figure which shows a magnetic head suspension and a hard disk drive.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal substrate 2 Insulating layer 3 Wiring layer 4 Cover layer 5 Protective plating layer 6 Low rigidity region 11 Photoresist layer 11A Laminate 21 Metal substrate 22 Insulating layer 24 Metal plating layer 24a Wiring pattern layer 25 Cover layer 30 Laminate 33 Resist 34 resist 35 resist 36 resist

Claims (25)

A metal substrate;
An insulating layer formed on the metal substrate and made of an insulating layer forming material;
A wiring layer formed on the insulating layer;
A cover layer made of a cover layer forming material, formed on the insulating layer and covering at least a part of the wiring layer;
The hygroscopic expansion coefficients of the insulating layer forming material and the cover layer forming material are in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and the difference between the hygroscopic expansion coefficients of both is 0 to 5 ×. A suspension substrate characterized by being in the range of 10 ⁻⁶ /% RH. A metal substrate;
An insulating layer formed on the metal substrate and made of an insulating layer forming material;
A wiring layer formed on the insulating layer;
A cover layer made of a cover layer forming material, formed on the insulating layer and covering at least a part of the wiring layer;
The insulating layer forming material and the cover layer forming material are made of different materials, and their hygroscopic expansion coefficients are in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH. A suspension substrate, wherein a difference in coefficients is in a range of 5 × 10 ⁻⁶ /% RH or less. The thermal expansion coefficients of the insulating layer forming material and the cover layer forming material are in the range of 15 × 10 ⁻⁶ / ° C. to 30 × 10 ⁻⁶ / ° C., and the heat of the insulating layer forming material and the cover layer forming material. The suspension substrate according to claim 1 or 2, wherein a difference in expansion coefficient is within a range of 10 x ^10-6 / ° C or less.   3. The suspension substrate according to claim 1, wherein either or both of the insulating layer forming material and the cover layer forming material are made of a non-photosensitive material. 4. A metal substrate;
An insulating layer formed on the metal substrate and made of an insulating layer forming material;
A wiring layer formed on the insulating layer;
A cover layer made of a cover layer forming material, formed on the insulating layer and covering at least a part of the wiring layer;
The insulating layer forming material and the cover layer forming material are made of the same non-photosensitive material, and their hygroscopic expansion coefficients are in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH. Suspension substrate. 6. The suspension substrate according to claim 5, wherein the insulating layer forming material and the cover layer forming material have coefficients of thermal expansion in a range of 15 × 10 ⁻⁶ / ° C. to 30 × 10 ⁻⁶ / ° C. . The suspension substrate according to claim 1, wherein the insulating layer forming material and the cover layer forming material include a repeating unit represented by the following formula.

(R1 is a tetravalent organic group, R2 is a divalent organic group, R1 and R2 may be a single structure or a combination of two or more types, n is a natural number of 1 or more)   In the said Formula 1, the organic group represented by R1 or R2 contains an aromatic, The board | substrate for suspensions of Claim 7 characterized by the above-mentioned. The suspension substrate according to claim 7, wherein 33 mol% or more of R ¹ in the formula (1) has a structure represented by the following formula (2).

The suspension substrate according to claim 7, wherein 33 mol% or more of R ² in the formula (1) has a structure represented by the following formula (4).

(R ³ is a divalent organic group, an oxygen atom, a sulfur atom, or a sulfone group, and R ⁴ and R ⁵ are a monovalent organic group or a halogen atom.)   8. The suspension substrate according to claim 7, wherein the precursor of either or both of the insulating layer forming material and the cover layer forming material can be developed with a basic aqueous solution. A metal substrate; an insulating layer formed on the metal substrate; a wiring layer formed on the insulating layer; and a cover layer formed on the insulating layer and covering at least a part of the wiring layer. A method of manufacturing a suspension substrate,
An insulating layer forming step of forming an insulating layer made of an insulating layer forming material in a pattern on the metal substrate;
A cover layer forming step of forming a cover layer made of a cover layer forming material in a pattern on the insulating layer;
The insulating layer-forming material and the cover layer-forming material is made of a different material, hygroscopic expansion coefficient therebetween is in the range of ^{RH 0 × 10 -6 /% RH~30} × 10 -6 /%, still both The method for producing a suspension substrate, wherein the difference between the hygroscopic expansion coefficients is within a range of 5 × 10 ⁻⁶ /% RH or less. The cover layer forming step includes a non-photosensitive cover layer forming layer made of a non-photosensitive cover layer forming material on the insulating layer, and a photosensitive resin formed on the non-photosensitive cover layer forming layer. Placing a laminate comprising a photoresist layer comprising:
The photoresist layer of the laminate is exposed in a pattern, and simultaneously with the development of the exposed photoresist layer, the non-photosensitive cover layer forming layer is developed, whereby the cover layer is patterned. The method for manufacturing a suspension substrate according to claim 12, further comprising a step of forming the suspension substrate.   13. The method for manufacturing a suspension substrate according to claim 12, wherein the cover layer forming step includes a step of applying a liquid cover layer forming material containing the cover layer forming material on the insulating layer. A laminate preparation step of preparing a laminate in which a metal substrate, an insulating layer, and a metal plating layer are arranged in this order;
A patterned resist is formed on the surface of the metal substrate and the surface of the metal plating layer, and etching is performed to form jig holes in the metal substrate, and a wiring pattern layer is formed in the metal plating layer. A first metal etching step;
A method for manufacturing a suspension substrate, comprising: Using a cover material, a cover layer forming step of forming a cover layer having a wiring pattern layer exposed opening in which part of the surface of the wiring pattern layer is exposed in the wiring pattern layer;
An insulating layer etching step of etching the insulating layer after forming the cover layer;
A protective plating part forming step of forming a protective plating part on the surface of the wiring pattern layer exposed by the wiring pattern layer exposed opening;
After the insulating layer etching step and the protective plating portion forming step, a second metal etching step for performing outer shape processing of the metal substrate,
The method of manufacturing a suspension substrate according to claim 15, further comprising:   The method for manufacturing a suspension substrate according to claim 15, wherein a difference between the maximum film thickness portion and the minimum film thickness portion of the metal plating layer is 2 μm or less.   The method of manufacturing a suspension board according to claim 16, wherein a difference in film thickness between the maximum film thickness portion and the minimum film thickness portion on the wiring pattern layer of the cover layer is 1 µm or less.   The method for manufacturing a suspension board according to claim 16, wherein the cover layer is formed using a liquid cover material in the cover layer forming step. In a magnetic head suspension having a suspension substrate,
The suspension board is
A metal substrate;
An insulating layer formed on the metal substrate and made of an insulating layer forming material;
A wiring layer formed on the insulating layer;
A cover layer made of a cover layer forming material, formed on the insulating layer and covering at least a part of the wiring layer;
The hygroscopic expansion coefficient of the insulating layer forming material and the cover layer forming material is in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and the difference between the hygroscopic expansion coefficients of both is 0 to 5 ×. A magnetic head suspension characterized by being in the range of 10 ⁻⁶ /% RH. In a magnetic head suspension having a suspension substrate,
The suspension board is
A metal substrate;
An insulating layer formed on the metal substrate and made of an insulating layer forming material;
A wiring layer formed on the insulating layer;
A cover layer made of a cover layer forming material, formed on the insulating layer and covering at least a part of the wiring layer;
The insulating layer forming material and the cover layer forming material are made of different materials, and both have a hygroscopic expansion coefficient in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and further, both of the hygroscopic expansions. A magnetic head suspension having a coefficient difference in a range of 5 × 10 ⁻⁶ /% RH or less. In a magnetic head suspension having a suspension substrate,
The suspension board is
A metal substrate;
An insulating layer formed on the metal substrate and made of an insulating layer forming material;
A wiring layer formed on the insulating layer;
A cover layer made of a cover layer forming material, formed on the insulating layer and covering at least a part of the wiring layer;
The insulating layer forming material and the cover layer forming material are made of the same non-photosensitive material, and their hygroscopic expansion coefficients are in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH. Magnetic head suspension. In a hard disk drive having a suspension board,
The suspension board is
A metal substrate;
An insulating layer formed on the metal substrate and made of an insulating layer forming material;
A wiring layer formed on the insulating layer;
A cover layer made of a cover layer forming material, formed on the insulating layer and covering at least a part of the wiring layer;
The hygroscopic expansion coefficients of the insulating layer forming material and the cover layer forming material are in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH, and the difference between the hygroscopic expansion coefficients of both is 0 to 5 ×. A hard disk drive characterized by being in a range of 10 ⁻⁶ /% RH. In a hard disk drive having a suspension board,
The suspension board is
A metal substrate;
An insulating layer formed on the metal substrate and made of an insulating layer forming material;
A wiring layer formed on the insulating layer;
A cover layer made of a cover layer forming material, formed on the insulating layer and covering at least a part of the wiring layer;
The insulating layer forming material and the cover layer forming material are made of different materials, and their hygroscopic expansion coefficients are in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH. A hard disk drive having a coefficient difference in a range of 5 × 10 ⁻⁶ /% RH or less. In a hard disk drive having a suspension board,
The suspension board is
A metal substrate;
An insulating layer formed on the metal substrate and made of an insulating layer forming material;
A wiring layer formed on the insulating layer;
A cover layer made of a cover layer forming material, formed on the insulating layer and covering at least a part of the wiring layer;
The insulating layer forming material and the cover layer forming material are made of the same non-photosensitive material, and their hygroscopic expansion coefficients are in the range of 0 /% RH to 30 × 10 ⁻⁶ /% RH. Hard disk drive.

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