JP5136311B2 - Suspension board - Google Patents

Description

  The present invention is a suspension for use in a hard disk drive (HDD), which can easily match differential impedance and reduce distortion and noise due to reflection of an electric signal, even when downsized and densified. It is related with the board | substrate.

  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). Further, as the information transmission speed increases, it is necessary to design the suspension substrate as a distributed constant circuit.

As the lead wiring and write wiring formed on such a suspension substrate, generally, as shown in Patent Document 1, a wiring composed of a pair of wirings on an insulating layer is used. An electrical signal is transmitted. As another example, a wiring in which the pair of wirings are arranged above and below with an insulating layer interposed therebetween is used.
Here, a differential impedance which is a characteristic impedance of a differential transmission line as a distributed constant circuit exists between such a pair of wires. Such differential impedances are adjusted to match the impedances of the read (reproducing) and writing (recording) heads and amplifiers to which the read wiring and the write wiring are connected, respectively.
Recently, the demand for HDDs installed in various small devices such as portable applications has increased, and as a result, the magnetic disk of HDDs has become higher in density, and the electrical signals through the magnetic head have been lowered. , Became susceptible to noise. In particular, the electrical signal for reading data is remarkably lowered, and there is a strong demand for lowering the differential impedance in the wiring of the suspension board.
In addition, there is a difference in the differential impedance required between the read wiring and the write wiring due to differences in the magnetic head, amplifier, and the like. Furthermore, as the suspension functions become higher, the suspension substrate is required to have a higher density.

In the suspension substrate having the above-described situation, a method for adjusting the differential impedance has been conventionally performed by adjusting the interval and the width of each pair of wires constituting the lead wire and the write wire. It was.
When the impedance is reduced by such a method, it is necessary to make the above-described wiring width wider than the conventional one. However, since the wiring density is increasing, the adjustment allowance such as the wiring width that can be used to adjust the above-described differential impedance is reduced. There has been a problem that it is difficult to adjust the impedance to have a difference.

JP 2005-11387 A

  The present invention has been made in view of the above problems, and even when miniaturized and densified, it is easy to match differential impedance, and distortion and noise due to reflection of an electric signal, etc. The main object of the present invention is to provide a suspension substrate with a small amount of suspension.

  In order to achieve the above object, the present invention is formed so as to cover the first insulating layer, the lower lead wiring and the lower write wiring formed on one surface of the first insulating layer, and the lower lead wiring. An insulating layer between the read wires, an insulating layer between the write wires formed to cover the lower write wire, an upper lead wire formed on the insulating layer between the lead wires, and an insulating layer between the write wires The upper write wiring formed, and the inter-read wiring inter-line capacitance that is the inter-line capacitance between the lower and upper lead wirings, and the inter-line capacitance between the lower and upper write wirings. There is provided a suspension substrate characterized in that the inter-light line capacitance is different.

According to the present invention, the upper and lower read wirings and the write wiring can be formed independently. Further, the insulating layer between the lead wires and the insulating layer between the write wires can be formed independently. For this reason, it is possible to easily adjust the interline capacitance of the read wiring and the write wiring. As a result, even when the space is limited, the differential impedance can be easily adjusted. Therefore, even when the wiring is miniaturized and the wiring density is increased, impedance matching can be easily performed, and a signal to be transmitted can be reduced in noise and distortion.
Also, the inter-read line capacitance between the lower lead wiring and the upper lead wiring is different from the inter-write wiring capacitance between the lower write wiring and the upper write wiring. Thus, even when the differential impedance required for the read wiring and the write wiring is different, the read wiring and the write wiring can be independently made to have the optimum differential impedance.

In the present invention, it is preferable that a lead wiring interval which is an interval between the lower lead wiring and the upper lead wiring is different from a write wiring interval which is an interval between the lower write wiring and the upper write wiring.
The lead wire interval and the write wire interval may be different from each other in that the thickness between the inter-lead wire insulating layer and the inter-write wire insulating layer may be different from that of the lower lead wire. The thickness of the lower write wiring may be different.
This is because the interline capacitance of the read wiring and the write wiring can be adjusted with high accuracy, and as a result, the differential impedance can be adjusted with high accuracy.

In the present invention, a metal substrate may be disposed on the other surface of the first insulating layer on which the lower lead wiring and the lower write wiring are formed.
This is because the metal substrate can be arranged to have high mechanical strength.

  In the present invention, it is possible to provide a suspension substrate that can easily match differential impedance and reduce distortion and noise due to reflection of an electric signal and the like even when downsized and densified. There is an effect.

Hereinafter, the suspension substrate of the present invention will be described in detail.
The suspension substrate of the present invention includes a first insulating layer, a lower lead wiring and a lower write wiring formed on one surface of the first insulating layer, and a lead wiring formed so as to cover the lower lead wiring. An inter-write wiring insulating layer formed so as to cover the intermediate insulating layer and the lower write wiring; an upper lead wiring formed on the inter-lead wiring insulating layer; and an upper part formed on the inter-write wiring insulating layer Write wiring, and inter-read wiring inter-line capacitance that is the inter-line capacitance between the lower lead wiring and the upper lead wiring, and the write inter-wiring line that is the inter-line capacitance between the lower write wiring and the upper write wiring It is characterized in that the inter-space capacity is different.

Such a suspension substrate of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of a suspension substrate of the present invention. As illustrated in FIG. 1, the suspension substrate 10 of the present invention includes a metal substrate 1, a first insulating layer 2 formed on the metal substrate 1, and one surface of the first insulating layer 2. The formed lower lead wiring 3a and lower write wiring 4a, the inter-read wiring insulating layer 5 formed so as to cover the lower lead wiring 3a, and the inter-write wiring insulation formed so as to cover the lower write wiring 4a It has a layer 6, an upper lead wire 3 b formed on the inter-lead wire insulating layer 5, and an upper write wire 4 b formed on the inter-write wire insulating layer 6.
Here, in the suspension substrate of this example, the thickness h3 of the lower lead wiring 3a is different from the thickness h4 of the lower write wiring 4a (h3> h4). As a result, the interval H1 between the lower lead wire 3a and the upper lead wire 3b is different from the interval H2 between the lower write wire 4a and the upper write wire 4b (H1 <H2).
In this example, the insulating layer between lead wires and the insulating layer between write wires are made of the same material. For this reason, the inter-read wiring line capacitance between the lower lead wiring and the upper lead wiring, and the inter-write wiring line capacitance between the lower write wiring and the upper write wiring. It will be different.

As shown in FIG. 10, the lead wiring and write wiring in the conventional suspension substrate are such that the suspension substrate 100 is on the metal substrate 101, the first insulating layer 102, and one surface of the first insulating layer 102. The lower lead wiring 103a and the lower write wiring 104a are formed, and the second insulating layer 105 is formed so as to cover the lower lead wiring 103a and the lower write wiring 104a. The thicknesses of the lower lead wiring and the lower write wiring are usually the same. Further, the second insulating layer is formed in a lump so as to cover the lower lead and the lower write wiring.
For this reason, in the conventional suspension board, the differential impedance is generally adjusted by adjusting the line widths of the upper and lower read wirings or write wirings.
However, when the size is reduced and the wiring density is increased, the change range of the line width allowed for adjusting the differential impedance becomes very small due to the space limitation, and the difference between the read wiring and the write wiring is reduced. It becomes difficult to increase the difference in dynamic impedance. Therefore, when the differential impedance required for the read wiring and the write wiring is greatly different, it is difficult to obtain a value according to the request, and due to reflection on the electric signal transmitted by the read wiring or the write wiring. Noise and distortion may be large.

On the other hand, according to the present invention, the upper and lower portion lead wirings and the write wiring can be formed independently. Further, the insulating layer between the lead wires and the insulating layer between the write wires can be formed independently. In this way, it is possible to easily adjust the capacitance between the read wiring and the write wiring. For this reason, even when the space is limited, the degree of freedom in adjusting the differential impedance can be increased. Therefore, even if the differential impedance required for the read wiring and the write wiring is large due to the miniaturization and the high density of the wiring, the read wiring and the write wiring are independently optimized. The differential impedance can be obtained, and the distortion and noise can be reduced.
Also, the inter-read line capacitance between the lower lead wiring and the upper lead wiring is different from the inter-write wiring capacitance between the lower write wiring and the upper write wiring. Thus, even when the differential impedance required for the read wiring and the write wiring is different, the read wiring and the write wiring can be independently made to have the optimum differential impedance.
As described above, when such a suspension board of the present invention is used in a hard disk drive, noise and distortion due to reflection on an electric signal can be reduced, and data reliability is excellent. It can be done.

  The suspension substrate of the present invention includes at least a first insulating layer, a read wiring and a write wiring, and an inter-wiring insulating layer. Hereinafter, each configuration of the suspension substrate of the present invention will be described in detail.

1. Read Wiring and Write Wiring The read wiring in the present invention is composed of a lower lead wiring formed on the first insulating layer and an upper lead wiring formed on the inter-lead wiring insulating layer.
The write wiring includes a lower write wiring formed on the first insulating layer and an upper write wiring formed on the inter-write wiring insulating layer.
Further, the inter-read wiring line capacity is different from the write wiring line capacity.

(1) Line capacity The line capacity in the present invention refers to an electric capacity generated by coupling of wirings of differential lines of read and write. Further, when the line capacitance is large, the differential impedance is small, and when the line capacitance is small, the differential impedance is large.
In addition, as a method for setting the inter-read wiring line capacitance and the write wiring line capacitance, it is only necessary that the read wiring and the write wiring have optimum differential impedance. As such a setting method, for each wiring, a method of calculating the line capacitance that provides the optimum differential impedance by simulation may be used. A plurality of wirings having different line capacitances are created, and the differential impedance is set. A method of finding the optimum line capacitance may be used.

The read wiring and the write wiring in the present invention have different line capacities. As described above, the suspension board having different line capacities of the read wiring and the write wiring may be any board having a line capacity adjusted accurately. For example, (1) the interval between the lower lead wiring and the upper lead wiring The lead wiring interval may be different from the write wiring interval which is the interval between the lower write wiring and the upper write wiring (by the wiring interval adjusting method), and (2) the lower lead wiring The lead wire overlap width, which is the overlap width of the upper lead wire, and the write wire overlap width, which is the overlap width of the lower write wire and the upper write wire, are different (according to the overlap width adjustment method). (3) the dielectric constant of the insulating layer between the lead wires formed between the lower lead wire and the upper lead wire, and the lower write That the line and upper write wiring dielectric constant of the write wiring insulating layer formed between the is different from may be (due to the dielectric constant adjustment method).
Moreover, what combined the said (1)-(3) method may be used. Furthermore, the conventional method for adjusting the differential impedance, which is a method for adjusting the widths of the lead wiring (lower lead wiring and upper lead wiring) and the write wiring (lower write wiring and upper write wiring), is also used. Also good.

  In the present invention, it is preferable that the interval between the read wires and the interval between the write wires are different from each other. This is because the interline capacitance of the read wiring and the write wiring can be adjusted with high accuracy. As a result, the differential impedance can be adjusted with high accuracy.

(A) Wiring spacing adjustment method In the present invention, the line capacitance is adjusted by the wiring spacing adjusting method as long as the lead wiring spacing is different from the write wiring spacing. And the thickness of the lower write wiring and the thickness of the insulating layer between the lead wires and the thickness of the insulating layer between the write wires are different. A combination of these may also be used.

Here, the thickness of the lower lead wiring and the thickness of the lower write wiring are different from those of the insulating layer 5 between the lead wires and the insulating layer 6 between the write wires as illustrated in FIG. The thickness may be the same, and the thickness h3 of the lower lead wire 3a is greater than the thickness h4 of the lower write wire 4a. In this case, the read wiring interval H1 <the write wiring interval H2.
As shown in FIG. 2, the thicknesses of the lower lead wiring 3a and the lower write wiring 4a are the same as the thickness of the insulating layer between the lead wires and the thickness of the insulating layer between the write wires. The thickness h5 of the insulating layer 5 between the lead wires is greater than the thickness h6 of the insulating layer 6 between the write wires. In this case, the read wiring interval H1> the write wiring interval H2.
Note that the reference numerals in FIG. 2 indicate the same members as those in FIG.

In the present invention, as the different thickness wiring forming method for forming the lower lead and the lower write wiring so that the thickness of the lower lead wiring is different from the thickness of the lower write wiring, both wirings have desired thicknesses. Any method can be used.
As such a different thickness wiring formation method, when the lower lead wiring and the lower write wiring are formed by plating, any method can be used as long as the plating thickness is different. The method of making it different and the method of making different plating conditions, such as plating time, can be mentioned.
In addition, when etching a conventional plated copper foil (a copper foil produced on an insulating layer by plating) or a rolled copper foil to be used for the lower lead wiring and the lower write wiring, the etching sequence, time, etching solution, etc. A method of forming the lower lead wiring and the lower write wiring having a desired thickness by making the etching conditions different may be used.

In the present invention, as a method of changing the number of times of electrolytic plating, as illustrated in FIG. 3, first, after forming the lower lead wiring 3a and the lower write wiring 4a having the same thickness, only the lower lead wiring 3a is formed. A method of forming a lower lead wiring 3a and a lower write wiring 4a having different thicknesses by arranging a resist 11 having a pattern of opening (FIG. 3A) and performing electrolytic plating on the lower lead wiring 3a again. (FIG. 3B).
Note that the reference numerals in FIG. 3 indicate the same members as those in FIG.

Further, as a method for making the plating conditions different, specifically, as illustrated in FIG. 4, electrolytic plating is performed in a state where a patterned resist having an opening is arranged in a region where the lower lead wiring is formed. After forming the lower lead wiring 3a by performing for a predetermined time, a patterned resist 11 having an opening is disposed in a region where the lower write wiring is formed (FIG. 4A), and plating at the time of forming the lower lead wiring is performed. The lower light wiring 4a is formed by performing electroplating for a period shorter than the time (FIG. 4B). Thus, a method of forming the lower lead wiring and the lower write wiring having different thicknesses can be mentioned.
In addition, about the code | symbol in FIG. 4, since it shows the member same as FIG. 1, description here is abbreviate | omitted.

In the present invention, between the different thickness wirings forming the insulating layer between the lead wires and the insulating layer between the write wires so that the thickness of the insulating layer between the lead wires and the thickness of the insulating layer between the write wires are different. As a method for forming the insulating layer, any method may be used as long as the insulating layer between the wirings has a desired thickness.
As such a method for forming an insulating layer between different thickness wirings, for example, a method of sequentially forming an insulating layer between read wirings and an insulating layer between write wirings, or a method of making the number of laminated layers for forming an insulating layer between wirings different Further, there can be mentioned a method in which the etching conditions for dry or wet etching of the inter-wiring insulating layer forming layer are different. In addition, when the material constituting the inter-wiring insulating layer has photosensitivity, a method of forming a lead inter-wiring insulating layer and a write inter-wiring insulating layer having different thicknesses at once using a halftone mask. Can be used.

In the present invention, as a method of sequentially forming the insulating layer between the lead wires and the insulating layer between the write wires, specifically, as shown in FIG. A patterned resist 11 is disposed in the region and etching is performed (FIG. 5A), thereby forming an insulating layer 5 between lead wires (FIG. 5B). Next, a resist 11a is disposed on the inter-lead-wire insulating layer 5, and then the inter-wiring insulating layer thicker than the inter-wiring insulating layer forming layer 15 formed when the inter-lead-wire insulating layer 5 is formed. A forming layer 15 is formed, and a patterned resist 11b is further disposed on the lower write wiring 4a, and etching is performed (FIG. 5C). Next, as shown in FIG. 5 (d), the resist 11 (11a and 11b) on the insulating layer 5 between the lead wires and the insulating layer 6 between the write wires is removed, and the insulating layers 5 between the lead wires having different thicknesses and A method for obtaining the inter-write wiring insulating layer 6 can be mentioned (FIG. 5E).
In addition, about the code | symbol in FIG. 5, since it shows the member same as FIG. 1, description here is abbreviate | omitted.

Further, as a method of forming the insulating layer between the lead wires and the insulating layer between the write wires having different thicknesses depending on the number of laminated layers for forming the insulating layer between the wirings, specifically, as illustrated in FIG. A first inter-wiring insulating layer forming layer 15a is formed in a pattern so as to cover the lead wiring and the lower write wiring (FIG. 6A). Next, after a resist 11a is disposed in a predetermined region on the first inter-wiring insulating layer forming layer 15a, a second inter-wiring insulating layer forming layer 15b is formed, and then the second inter-wiring insulating layer is formed. The resist 11b is disposed in a predetermined region on the use layer 15b (FIG. 6B), and etching is performed (FIG. 6C). Thereafter, as shown in FIG. 6 (d), by removing the resist, the inter-read wiring insulating layer 5, and between the write wirings composed of the first inter-write wiring insulating layer 6a and the second inter-write wiring insulating layer 6b. The method of obtaining the insulating layer 6 can be mentioned.
In addition, about the code | symbol in FIG. 6, since it shows the member same as FIG. 1, description here is abbreviate | omitted.

In the present invention, as a method for forming the insulating layer between the lead wires and the insulating layer between the write wires having different thicknesses by using the halftone mask, specifically, as shown in FIG. The lead 15 having a different thickness is exposed by exposing the inter-wiring insulating layer forming layer 15 through a halftone mask 20 having a plurality of regions having different transmittances of exposure light (FIG. 7A) and then developing. A method of forming the inter-wiring insulating layer 5 and the write inter-wiring insulating layer 6 at once (FIG. 7B).
Here, as the halftone mask 20, for example, a transparent substrate 21, a semi-transparent film 22 formed on the transparent substrate 21, and a light-shielding film 23 having a light-shielding property can be used. In this example, a negative photosensitive resin is used as the photosensitive resin, and an inter-light-wiring insulating layer is formed in a region having only the transparent substrate with the highest transmittance, and then transmitted. An insulating layer between lead wires having a thickness smaller than that of the above-mentioned inter-write wiring insulating layer is formed in a region composed of a transparent substrate and a semi-transparent film, and an inter-wiring insulating layer is not formed in a region including a light shielding film. It was supposed to be.
In addition, about the code | symbol in FIG. 7, since it shows the member same as FIG. 1, description here is abbreviate | omitted.

(B) Other methods In the present invention, the line capacitance is adjusted by another method, for example, the line width capacitance is adjusted by an overlap width adjustment method or a dielectric constant adjustment method.

In the present invention, the line capacitance is adjusted by the dielectric constant adjustment method as long as the dielectric constants of the insulating layer between the lead wires and the insulating layer between the write wires are different. An example in which the inter-wiring insulating layer is formed of materials having different dielectric constants can be given.
Specifically, the inter-lead wiring insulating layer may be formed of a material having a higher dielectric constant than the material constituting the write inter-wiring insulating layer.

  In the present invention, as a method of forming the insulating layer between the lead wires and the insulating layer between the write wires using different materials, the insulating layer between the lead wires and the insulating layer between the write wires as shown in FIG. It is possible to use a method in which layers are sequentially formed and formed using different materials.

In the present invention, the line capacitance is adjusted by the overlap width adjustment method as long as the read line overlap width and the write line overlap width are different, as illustrated in FIG. In addition, it is preferable to use ones having different upper and lower wiring formation positions. This is because even when there is a space limitation, the interline capacitance of the read wiring and the write wiring can be adjusted with high accuracy, so that the differential impedance can be adjusted with high accuracy.
The overlapping width refers to a width in which the wirings overlap when the lower lead wiring and the upper lead wiring (or the lower write wiring and the upper write wiring) are viewed in plan. Moreover, about the code | symbol in FIG. 8, since it shows the member same as FIG. 1, description here is abbreviate | omitted.
In the example of FIG. 8, the widths of the read wiring and the write wiring are the same. By shifting the formation positions of the lower lead wiring and the upper lead wiring, the lead wiring overlapping width w3ab <write wiring overlapping width w4ab. It is said.

(2) Read wiring and write wiring The lead wiring in the present invention comprises a lower lead wiring formed on the first insulating layer and an upper lead wiring formed on the inter-lead wiring insulating layer. .
The write wiring includes a lower write wiring formed on the first insulating layer and an upper write wiring formed on the inter-write wiring insulating layer.

  Examples of the material for the read wiring and the write wiring used in the present invention include copper (Cu).

The thicknesses of the read wiring and the write wiring used in the present invention are not particularly limited as long as desired conductivity can be exhibited, but it is usually preferably in the range of 6 μm to 18 μm. However, it is preferably in the range of 8 μm to 12 μm. This is because within the above range, the suspension substrate of the present invention can be reduced in rigidity.
The thicknesses of the read wiring and the write wiring refer to the respective thicknesses of the lower lead wiring, the upper lead wiring, the lower write wiring, and the upper write wiring that constitute the thickness of the read wiring and the write wiring.

The line widths of the read wiring and the write wiring used in the present invention are not particularly limited as long as they can exhibit desired conductivity, but are preferably in the range of 10 μm to 100 μm. . This is because within the above range, the suspension substrate of the present invention can be reduced in rigidity.
The line widths of the read wiring and the write wiring refer to the respective line widths of the lower lead wiring, the upper lead wiring, the lower write wiring, and the upper write wiring that constitute the thickness of the read wiring and the write wiring. .

  The formation positions of the read wiring and the write wiring are not particularly limited as long as they are formed so as to have the overlapping width of the read wiring and the overlapping width of the write wiring, and are appropriately set according to the use of the suspension substrate of the present invention. Is.

In general, the lead wiring and the write wiring used in the present invention preferably have a protective plating layer formed of nickel (Ni) or gold (Au) on the surface thereof. This is because the read wiring and the write wiring can be made resistant to corrosion.
The thickness of the protective plating layer can be the same as that of a general protective plating layer in a suspension substrate, but is preferably 5 μm or less.

  As a method for forming the read wiring and the write wiring used in the present invention, any method can be used as long as it can be formed at a desired position and with a desired thickness, and a method generally used for a suspension substrate can be used. it can. For example, a method of forming by plating such as electrolytic plating may be used, or a method of forming by etching a metal thin film or the like may be used.

2. Inter-wiring insulating layer The inter-wiring insulating layer used in the present invention includes an inter-lead wiring insulating layer formed so as to cover the lower lead wiring, and an inter-write wiring insulating layer formed so as to cover the lower write wiring. Is included. The insulating layer between the lead wires is disposed so that the lower lead wire and the upper lead wire do not contact each other, and the insulating layer between the write wires does not contact the lower write wire and the upper write wire. Is to be arranged.

Examples of the material for the inter-wiring insulating layer include polyimide (PI).
The material for the inter-wiring insulating layer may be a photosensitive material having photosensitivity or a non-photosensitive material having no photosensitivity.

The thickness of the inter-wiring insulating layer is not particularly limited as long as a desired insulating property can be exhibited, but is usually about 5 μm to 30 μm.
The thickness of the inter-wiring insulating layer refers to the thickness from the surface of the first insulating layer to the surface of the inter-wiring insulating layer.

  The formation location of the inter-wiring insulating layer used in the present invention may be any as long as the read wiring and the write wiring can have a desired inter-line capacitance. For example, as shown in FIG. The insulating layer between the lead wires and the insulating layer between the write wires may be continuously formed, or may be separated as shown in FIG.

As a method for forming the inter-wiring insulating layer used in the present invention, any method can be used as long as it can be formed to a desired thickness, and a method generally used for a suspension substrate can be used. For example, a coating solution containing the material for the inter-wiring insulating layer may be used, or a dry film made of the material for the inter-wiring insulating layer may be used.
In addition, when forming using the coating solution, the coating amount per coating of the coating solution, the number of coatings, etc. can be adjusted according to the shape of the lower read / write wiring. preferable. The reason why such adjustment is necessary is as follows.
That is, when the coating liquid is applied onto a base material having a convex portion, leveling occurs in which the coating liquid applied onto the convex portion flows down onto the base material. This is because the leveling amount varies depending on the shape of the convex portion (top area, height, etc.).

3. First Insulating Layer The first insulating layer used in the present invention may be any one that can form the above-described lead wiring, write wiring, and the like and is excellent in insulation.

  The material constituting the first insulating layer can be the same as the material constituting the inter-wiring insulating layer.

  The thickness of the first insulating layer used in the present invention is not particularly limited as long as a desired insulating property is exhibited, and is usually about 5 μm to 30 μm.

  The method for forming the first insulating layer used in the present invention is not particularly limited as long as the first insulating layer can be formed in a desired film thickness, and is the same as that described in the above section “2. Inter-wiring insulating layer”. be able to.

4). Suspension Substrate The suspension substrate of the present invention has at least a first insulating layer, a lead wiring and a write wiring, and an inter-wiring insulating layer, but usually has a metal substrate and a cover layer.

  The metal substrate used in the present invention has electrical conductivity and is used for suspension applications, and therefore usually has an appropriate spring property.

  Examples of the material for the metal substrate include stainless steel.

  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. This is because if the metal substrate is too thin, the mechanical strength may be reduced, and if the metal substrate is too thick, flexibility may be lost.

  The metal substrate used in the present invention may be formed as long as the suspension substrate of the present invention can have a desired mechanical strength, but is arranged as far as possible from the lead wiring and write wiring. It is desirable. This is to eliminate as much as possible the influence on the differential line from the metal substrate.

  The cover layer used in the present invention is formed so as to cover the read wiring and the write wiring. The thickness of the cover layer is not particularly limited, but is usually about 3 μm to 30 μm. The material of the cover layer is not particularly limited, and the same material as the cover layer used for a general flexible substrate or the like can be used. The cover layer is preferably formed at a location covering all of the read wiring and the write wiring. This is because the environment around the wiring can be made uniform.

  The suspension substrate according to the present invention may be manufactured by any method as long as the above components are formed with high accuracy. Specifically, as illustrated in FIG. 9, first, the metal substrate 1 and the metal substrate 1 are used. After preparing a laminate composed of the first insulating layer 2 formed thereon, the lower lead wiring 3a is formed by plating for a predetermined time by an electrolytic plating method, and then an opening is formed in a region where the lower write wiring is formed. A resist 11 is disposed (FIG. 9A). Next, as shown in FIG. 9B, electrolytic plating is performed in a shorter plating time than when forming the lower lead wiring to form the lower write wiring 4a having a thickness smaller than that of the lower lead wiring 3a, and then the resist is peeled off. (FIG. 9C). Next, as shown in FIG. 9 (d), a coating liquid containing a material for the inter-wiring insulating layer is applied, dried, and then etched in a state in which a patterned resist is disposed, whereby the inter-wiring insulating layer ( 5 and 6) are formed. Thereafter, as shown in FIG. 9E, the upper lead wiring 3b and the upper write wiring 4b are formed by electroplating in a state where the patterned resist is arranged. Further, as shown in FIG. 9 (f), a cover layer 7 is formed so as to cover the upper lead wiring 3b and the upper write wiring 4b, and the difference between the upper and lower wiring intervals (the upper lead wiring and the lower lead wiring). There can be mentioned a method of obtaining the suspension substrate 10 in which the wiring interval and the difference between the upper write wiring and the lower write wiring) are different.

  The suspension substrate of the present invention is used for a magnetic head suspension of a hard disk drive (HDD) and is required to have little distortion and noise even when the wiring density is increased. It is suitably used for a magnetic head suspension of a hard disk drive (HDD).

  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 lower lead wiring and a lower write wiring made of copper are formed on a first insulating layer made of polyimide having a relative dielectric constant of 3.3 and a thickness of 10 μm. The width of both wirings is 55 μm and the thickness is 5 μm.
Thereafter, the polyimide used for forming the first insulating layer is used to form an insulating layer between the lead wires so that the thickness on the lower lead wire becomes 10 μm.
Next, using the polyimide, an inter-write wiring insulating layer is formed so that the thickness on the lower write wiring is 5 μm.
Next, an upper lead wire is formed on the insulating layer between the lead wires, and an upper write wire is formed on the insulating layer between the write wires. Both wirings have a width of 55 μm and a thickness of 5 μm.
In this way, the thicknesses of the read wiring interval and the write wiring interval are 10 μm and 5 μm, respectively, and the suspension substrate is manufactured with different line capacities of both wirings.

  When the differential impedance of the suspension substrate designed as described above was analyzed by simulation, the differential impedance of the lead wiring was 30Ω and the differential impedance of the write wiring was 18Ω.

[Example 2]
A lower lead wiring and a lower write wiring made of copper are formed on a first insulating layer made of polyimide having a relative dielectric constant of 3.3 and a thickness of 10 μm. The width of both wires is 55 μm. The thickness of the lower lead wiring is 5 μm, and the thickness of the lower write wiring is 10 μm.
Thereafter, using the polyimide used for forming the first insulating layer, an insulating layer between the lead wires and an insulating layer between the write wires are formed. The thickness of the insulating layer between both wirings is 15 μm.
Next, an upper lead wire is formed on the insulating layer between the lead wires, and an upper write wire is formed on the insulating layer between the write wires. Both wirings have a width of 55 μm and a thickness of 5 μm.
In this way, a suspension substrate is produced in which the thicknesses of the read wiring interval and the write wiring interval are 10 μm and 5 μm, respectively, and the line capacities of both wirings are different.

  With respect to the suspension substrate designed as described above, the differential impedance was analyzed in the same manner as in Example 1. As a result, the differential impedance of the lead wiring was 30Ω and the differential impedance of the write wiring was 18Ω.

It is a schematic sectional drawing which shows an example of the board | substrate for suspensions of this invention. It is a schematic sectional drawing which shows the other example of the board | substrate for suspensions of this invention. It is process drawing which shows an example of the formation method of the read wiring and write wiring in this invention. It is process drawing which shows the other example of the formation method of the read wiring and write wiring in this invention. It is process drawing which shows an example of the formation method of the insulating layer between wiring in this invention. It is process drawing which shows the other example of the formation method of the insulating layer between wiring in this invention. It is process drawing which shows the other example of the formation method of the insulating layer between wiring in this invention. It is a schematic sectional drawing which shows the other example of the board | substrate for suspensions of this invention. It is process drawing which shows an example of the manufacturing method of the board | substrate for suspensions of this invention. It is a schematic sectional drawing which shows the conventional board | substrate for suspensions.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 101 ... Metal substrate 2, 102 ... 1st insulating layer 3, 103 ... Lead wiring 3a, 103a ... Lower lead wiring 3b, 103b ... Upper lead wiring 4, 104 ... Write wiring 4a, 104a ... Lower write wiring 4b, 104b ... Upper write wiring 5 ... Insulating layer between lead wirings 6 ... Insulating layer between write wirings 7 ... Cover layer 10, 100 ... Suspension substrate 105 ... Second insulating layer

Claims (5)

A first insulating layer;
A lower lead wiring and a lower write wiring formed on one surface of the first insulating layer;
An insulating layer between lead wires formed so as to cover the lower lead wire; an insulating layer between write wires formed so as to cover the lower write wire;
An upper lead wire formed on the insulating layer between the lead wires;
An upper light wiring formed on the insulating layer between the write wirings;
Have
The inter-read wiring inter-line capacitance that is the inter-line capacitance between the lower lead wiring and the upper lead wiring is different from the inter-write wiring inter-line capacitance that is the inter-line capacitance between the lower write wiring and the upper write wiring. A suspension substrate,
The suspension substrate , wherein the insulating layer between the lead wires and the insulating layer between the write wires are different in thickness, and the thickness of the first insulating layer is the same. The suspension substrate according to claim 1, wherein the lower lead wiring and the lower write wiring have the same thickness. The suspension substrate according to claim 2, wherein the thickness of the insulating layer between the lead wires is larger than the thickness of the insulating layer between the write wires. The suspension substrate according to claim 1 , wherein the lower lead wiring and the lower write wiring have different thicknesses.   5. The metal substrate according to claim 1, wherein a metal substrate is disposed on the other surface of the first insulating layer on which the lower lead wiring and the lower write wiring are formed. The suspension substrate according to item.

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