JP2003156844A - Photosensitive resin composition, porous resin, circuit board and suspension substrate with circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous resin having high heat resistance, dimensional stability, and insulating property, and having uniform micropores, a photosensitive resin composition for obtaining the porous resin, and a circuit board and a suspension substrate with a circuit each having such a porous resin as an insulating layer. SOLUTION: The photosensitive resin composition 2 comprises a polybenzoxazole precursor 4 having a repeating unit structure of formula (1), a photosensitive agent, a dispersible compound 3 and a solvent. The porous resin is obtained as follows; the solvent is removed from the photosensitive resin composition 2 to form a state in which the dispersible compound 3 is dispersed in the polybenzoxazole precursor 4, the compound 3 is then removed to make the precursor 4 porous, and the precursor 4 is hardened. Since the porous resin has a low dielectric constant, when it is used as an insulating layer 6 in a circuit board, the high-frequency characteristics of the circuit board can be improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a photosensitive resin composition,
The present invention relates to a porous resin, a circuit board and a suspension board with a circuit, and more specifically, a photosensitive resin composition and a porous resin which are preferably used for forming an insulating layer of the circuit board and the suspension board with a circuit, and such a material. The present invention relates to a circuit board and a suspension board with a circuit having a porous resin as an insulating layer.

[0002]

2. Description of the Related Art Polybenzoxazole resins are disclosed, for example, in JP-A-7-300558 and JP-A-2000-1.
As described in Japanese Patent No. 69582 and the like, it is being studied to use it for an interlayer insulating film of a multilayer circuit or a cover coat of a circuit board because it has high heat resistance, dimensional stability and insulation. However, recently, as electronic and electric devices have become higher in performance and higher in function, it has been required to store a large amount of information, process it at high speed, and transmit it at high speed. The benzoxazole resin is also required to have a low dielectric constant as an electrical characteristic corresponding to high frequencies.

However, since the dielectric constant of a plastic material is generally determined by its molecular skeleton, there is a limit to lowering the dielectric constant even if the molecular skeleton is modified. Therefore, various methods have been proposed, focusing on the low permittivity of air (ε = 1.0), by making the plastic material porous and controlling the permittivity by the porosity.

As a method for obtaining such a porous resin, there are a dry method and a wet method. In the dry method, generally, a physical method and a chemical method are known. The physical method is to disperse a low boiling point liquid (foaming agent) such as chlorofluorocarbons in a resin, and then heat it to volatilize the foaming agent to generate bubbles,
This obtains a foam. Further, the chemical method is to add a foaming agent to a resin and thermally decompose the resin to form a cell, thereby forming a foam. As a physical method, for example, in US Pat. No. 4,532,263, it has been proposed to obtain a foamed polyetherimide by using methylene chloride, chloroform, trichloroethane or the like as a foaming agent.

Further, in recent years, as a foam having a small cell diameter and a high cell density, a gas such as nitrogen or carbon dioxide is dissolved in a resin at a high pressure, and then the pressure is released to a glass transition point of the resin. Or by heating to near the softening point,
Methods for producing bubbles have been proposed. With such a method, a microporous foam can be obtained. For example, in JP-A-6-322168, this method can be applied to a polyetherimide resin to obtain a foam having heat resistance. Proposed. Further, for example, Japanese Patent Laid-Open No. 10-4
In 5936, this method is applied to a styrene-based resin having a syndiotactic structure to obtain a porous foam having a cell size of 0.1 to 20 μm, which can be used as an electric circuit member. Proposed. Further, for example, in Japanese Unexamined Patent Application Publication No. 9-100363, the porosity of foaming using carbon dioxide as a foaming agent is 10 vo.
Containing 1% or more of porous plastic, heat resistant temperature is 1
A low dielectric constant plastic insulating film having a dielectric constant of 2.5 or less at a temperature of 00 ° C. or higher has been proposed.

Further, in JP-A-2000-44719, a hydrophilic polymer is dispersed in a polyimide resin,
It has been proposed to obtain a porous polyimide resin by removing the hydrophilic polymer with a solvent that does not dissolve the polyimide resin such as water or alcohol but dissolves the hydrophilic polymer.

[0007]

However, in the method for obtaining such a porous resin, for example, in a physical method, chlorofluorocarbons used as a foaming agent are used for the purpose of safety and hygiene and environmental damage such as ozone layer destruction. It is not preferable from the above, and it is difficult to form a fine and uniform cell diameter.

Further, in the chemical method, after foaming, the residue of the foaming agent that has generated gas may remain in the foam, so that low pollution is strongly required for electronic / electrical devices and electronic parts. It is not suitable for the intended use.

Further, in a method of generating bubbles by dissolving a gas in a resin at a high pressure and then releasing the pressure, the gas is heated to near the glass transition point or the softening point of the resin. In the method described in Japanese Patent No. 322168, when high pressure gas is impregnated in a pressure vessel,
Since the pressure vessel is heated to or near the Vicat softening point of the resin, when the pressure is reduced, the resin is in a molten state while the high-pressure gas easily expands, so the bubble size of the obtained foam does not become too small. For example, when it is used as a circuit board or the like, its thickness becomes thicker, or miniaturization is limited in its patterning. Further, for example, in the method described in Japanese Patent Application Laid-Open No. 10-45936, the glass transition point of the styrene resin is around 100 ° C., so that it cannot be used at a temperature higher than that, and further, Japanese Patent Application Laid-Open No. 9-100363. In the method described in the publication, the bubble size is not so small, and there is a limit to miniaturization in patterning.

Further, in the method described in Japanese Patent Laid-Open No. 2000-44719, since the solvent dispersed in the polyimide resin is a hydrophilic polymer having a large molecular weight, the hydrophilic polymer is completely removed from the polyimide resin. Is difficult.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a porous material having high heat resistance, dimensional stability, and insulation, and having uniform and fine bubbles. (EN) A resin, a photosensitive resin composition for obtaining the porous resin, and a circuit board and a suspension board with a circuit having such a porous resin as an insulating layer.

[0012]

In order to achieve the above object, the photosensitive resin composition of the present invention comprises a polybenzoxazole precursor having a repeating unit structure represented by the following general formula (1) and a photosensitizer. And a dispersible compound dispersible in the polybenzoxazole precursor, and a solvent.

[0013]

[Chemical 3] (In the formula, R1 represents any of an ether bond, a carbon-carbon bond, and methylene which may be substituted, and R2
Is

[0014]

[Chemical 4] (A is the same or different and represents a hydrogen atom or a halogen atom). In this photosensitive resin composition, the dispersible compound is preferably at least one selected from the group consisting of polyacrylate oligomer, polyether oligomer, polyester oligomer and polyurethane oligomer.

Further, according to the present invention, the solvent is removed from the photosensitive resin composition to form a state in which the dispersible compound is dispersed in the polybenzoxazole precursor, and the dispersible compound is removed. It also includes a porous resin obtained by a step including a step of making porous, and a step of curing the photosensitive resin composition.
The step of obtaining the porous resin preferably includes a step of patterning the photosensitive resin composition by exposing and developing it.

Then, such a porous resin is suitably used as an insulating layer of a circuit board, particularly as an insulating layer of a suspension board with circuit.

The present invention also includes a circuit board and a suspension board with circuit, which have such a porous resin as an insulating layer.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The photosensitive resin composition of the present invention contains a polybenzoxazole precursor, a photosensitizer, a dispersible compound dispersible in the polybenzoxazole precursor, and a solvent. There is.

The polybenzoxazole precursor used in the present invention is a precursor of a polybenzoxazole resin having a repeating unit structure represented by the following general formula (1), and comprises bisaminophenol and a bifunctional aldehyde. Can be obtained by reacting.

[0020]

[Chemical 5] (In the formula, R1 represents any of an ether bond, a carbon-carbon bond, and methylene which may be substituted, and R2
Is

[0021]

[Chemical 6] (A is the same or different and represents a hydrogen atom or a halogen atom). ) In addition, as the optionally substituted methylene represented by R 1, for example, methylene and propylidene (—C (CH
₃ ) _2- ), hexafluoropropylidene (-C (CF
₃ ) _2- ) and the like.

The halogen atom represented by a includes, for example, fluorine, chlorine, bromine and iodine, preferably fluorine.

As a mode of R2, among four a, 4
All three are hydrogen atoms, any three are hydrogen atoms, the remaining one is a halogen atom, any two are hydrogen atoms and the other two are halogen atoms, one is a hydrogen atom and the remaining three are halogen atoms, or Embodiments in which all four are halogen atoms are mentioned. Preferred are an embodiment in which all four are hydrogen atoms, and an embodiment in which all four are halogen atoms.

The corresponding bisaminophenol includes
For example, 3,3′-diamino-4,4′-dihydroxyphenyl ether, 4,4′-diamino-3,3′-dihydroxyphenyl ether, 3,4′-diamino-3,4 ′
-Dihydroxyphenyl ether, 3,3'-dihydroxybenzidine, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane and the like. Further, they may be used alone or in combination of two or more kinds.

Examples of the corresponding bifunctional aldehydes include m- or p-phthalaldehyde and its halides, more specifically, isophthalaldehyde, terephthalaldehyde, tetrafluoroisophthalaldehyde, tetrafluoroterephthalate. Examples thereof include aldehyde. Further, they may be used alone or in combination of two or more kinds.

Incidentally, such a bifunctional aldehyde is
It can be prepared from the corresponding difunctional nitrile by known methods.

The polybenzoxazole precursor can be prepared, for example, by mixing these bisaminophenol and the bifunctional aldehyde in a substantially equimolar ratio.
In a suitable reaction solvent, for example, a polar solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, γ-butyrolactone, preferably under an inert gas atmosphere, By reacting at 0 to 90 ° C. for 1 to 36 hours, a solution of the polybenzoxazole precursor can be obtained.

The polybenzoxazole precursor thus obtained has, for example, a weight average molecular weight of 50.
About 00 to 200,000, preferably 10,000 to 1
It is about 00000. The polybenzoxazole precursor thus obtained may be used as it is, or may be subjected to an appropriate post-treatment such as collection and use after filtration after precipitation.

Since the polybenzoxazole precursor thus obtained can be obtained by a simple method of mixing bisaminophenol and a bifunctional aldehyde, the production efficiency is improved and the cost is reduced. Can be realized. In addition, in such a reaction, it is not necessary to use an ionic substance such as an acid chloride as in the case of obtaining a polybenzoxazole precursor by a reaction of bisaminophenol and a bifunctional carboxylic acid. Corrosion is improved, and when it is used as an insulating layer of a circuit board as described later, reliability can be improved.

As the photosensitizer used in the present invention, any photosensitizer can be used as long as it can obtain a solubility contrast between an exposed portion and an unexposed portion when the polybenzoxazole precursor is exposed. Examples of such a photosensitizer include a dihydropyridine derivative, a diazonaphthoquinonesulfonic acid ester derivative, and an aromatic diazide compound.

Among these sensitizers, a diazonaphthoquinone sulfonic acid ester derivative which can be developed with an alkaline aqueous solution and can form a positive image is preferably used.

The diazonaphthoquinone sulfonate derivative is 1,2-benzoquinone diazide, or
It is a compound having a 1,2-naphthoquinonediazide structure and is not particularly limited, and examples thereof include compounds represented by the following structural formulas. In addition, such a diazonaphthoquinone sulfonic acid ester derivative may be used alone or in combination of two or more kinds.

[0033]

[Chemical 7] The blending amount of the photosensitizing agent is the polybenzoxazole precursor 10
It is usually used in the range of 1 to 100 parts by weight with respect to 0 parts by weight. If it is less than 1 part by weight, the patterning property may be poor, and if it exceeds 100 parts by weight, the mechanical strength of the coating may be significantly reduced.

The dispersible compound used in the present invention is a compound dispersible in the polybenzoxazole precursor, and more specifically, it is microphase-separated as fine particles in the polybenzoxazole precursor. Then, it is a compound capable of forming a sea-island structure. The dispersible compound used in the present invention is not particularly limited as long as it is such a compound, but a compound that is not completely compatible with the polybenzoxazole precursor is preferable, or it is volatilized by heating, or, Decomposes and carbonizes, or
Those that can be extracted with a specific solvent are preferably used. Examples of such a compound include oligomers having a relatively low degree of polymerization in which two or more of the same or different monomers are polymerized, and more specifically, for example, polyacrylate oligomer, polyether oligomer, Examples thereof include polyester oligomers and polyurethane oligomers.

Examples of the polyacrylate oligomer include hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, epoxy (meth). Acrylate, oligoester (meth) acrylate, etc. are mentioned.

As the polyether oligomer, for example, polyethylene glycol, polypropylene glycol, polybutylene glycol, and one end or both ends of which are blocked with a blocking agent such as methyl, phenyl or (meth) acrylate. The thing etc. are mentioned.

Examples of the polyester oligomer include ε-caprolactone and a blocked product in which one end or both ends thereof are blocked with a blocking agent such as methyl, phenyl or (meth) acrylate.

Examples of the polyurethane oligomer include urethane polyols such as reaction products of macropolyols such as polyether polyols, polyester polyols, polycarbonate polyols and polybutadiene polyols, and polyisocyanate monomers such as hydroxyethyl (meth) acrylate. Reaction products of hydroxy (meth) acrylate monomers such as phenylglycidyl ether acrylate, pentaerythritol triacrylate and glycerin dimethacrylate with polyisocyanate monomers such as methylene diisocyanate, tolylene diisocyanate and isophorone diisocyanate, or the above urethane polyols The urethane acrylate of

Such dispersible compounds may be used alone or in combination of two or more kinds. The weight average molecular weight thereof is 150 to 10,000, and further 300
It is preferably in the range of to 5000. If it is less than 150, it may be satisfactorily compatible with the polybenzoxazole precursor, while if it exceeds 10,000, fine dispersion may not be possible in some cases. Further, such a dispersible compound is usually 200 parts by weight or less based on 100 parts by weight of the polybenzoxazole precursor, and the size of the bubbles of the porous resin is fine (less than 10 μm).
In order to achieve the above, it is preferably used in the range of 10 to 200 parts by weight, and more preferably in the range of 30 to 100 parts by weight in order to reduce the dielectric constant to 3 or less.

As the solvent used in the present invention, the reaction solvent used for synthesizing the polybenzoxazole precursor may be used as it is, and further, together with such a reaction solvent or in place of the reaction solvent, for example, Organic solvents such as 1,3-dimethyl-2-imidazolidinone, diglyme, triglyme, tetrahydrofuran, dioxane, cyclohexane, toluene and xylene may be used alone or in combination of two or more. The amount of the solvent used is not particularly limited, but the viscosity of the photosensitive resin composition is usually adjusted according to the purpose and use by adjusting the amount used. Usually, it is used in a range of from 1 to 100 times by weight, preferably from 2 to 50 times by weight, based on the total amount of the polybenzoxazole precursor, the photosensitizer and the dispersible compound.

In the photosensitive resin composition of the present invention, the polybenzoxazole precursor, the photosensitizer, the dispersible compound and the solvent may be blended in the above-mentioned proportions by a known method. The thus-obtained photosensitive resin composition of the present invention has high heat resistance, dimensional stability, and insulating properties, and further, has uniform and fine bubbles, and has a low dielectric constant and a fine pattern. It is preferably used as a raw material of a porous resin that is easy to form, especially a porous resin for forming an insulating layer of a circuit board.

Next, a method for producing a porous resin using the photosensitive resin composition of the present invention will be described by taking as an example a method for forming an insulating layer of a circuit board made of the porous resin.

In this method, as shown in FIG.
First, a predetermined base material 1 is prepared, and as shown in FIG. 1 (b), the photosensitive resin composition 2 is applied onto the base material 1 and then dried by hot air drying or the like to form a photosensitive material. The solvent is removed from the resin composition 2 to form a film.

Examples of the substrate include metal or alloy foils or plates such as copper, aluminum, stainless steel, copper-beryllium, phosphor bronze, iron-nickel, etc., such as silicon wafers, ceramic foils or plates such as glass,
Examples thereof include plastic films such as polybenzoxazole resin and polyester resin.

The coating of the photosensitive resin composition may be carried out by a known coating method such as spin coater or bar coater, and may be appropriately selected depending on the shape of the substrate and the thickness of the coating. Just apply it. Further, it is preferable to apply the coating so that the thickness after drying is 0.1 to 50 μm, preferably 1 to 25 μm. In addition, before coating,
Adhesion can be improved by pre-coating the surface of the substrate with a silane coupling agent or a titanate coupling agent in advance.

The drying is usually 40 ° C to 120 ° C.
To do. When it is lower than 40 ° C, the removal rate of the solvent is slow, and when it is higher than 120 ° C, the photosensitizer may be thermally decomposed. It is preferably carried out at 60 to 100 ° C.
By the solvent being removed by such drying, the dispersible compound 3 becomes insoluble in the polybenzoxazole precursor 4 as shown in a model in FIG. 1B, and fine particles are obtained. As a result, a micro-phase separation occurs, and a sea-island structure of the dispersible compound 3 is formed in the polybenzoxazole precursor 4.

Next, as shown in FIG. 1 (c), the dried photosensitive resin composition 2 is exposed by irradiating it with an actinic ray through a photomask 5, and then heating it if necessary. To form a positive or negative latent image, and by developing the latent image, a positive or negative image, that is, a required pattern is formed. More specifically, although the polybenzoxazole precursor is somewhat different depending on the type of the photosensitizer used, in the case of a diazonaphthoquinone sulfonate derivative, for example, the exposed part is dissolved in a developer to form a positive image. To do.

The development may be carried out by a known method such as a dipping method or a spray method, and the developing temperature is usually 25 to 5
A range of 0 ° C is suitable. The developing solution used is, for example, a good solvent (N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-).
Pyrrolidone, etc.) and poor solvent (lower alcohol, ketone,
Examples thereof include a mixed solvent with water and aromatic hydrocarbon), a basic solvent (tetramethylammonium hydroxide aqueous solution, triethanolamine aqueous solution, water-soluble organic amine compound, etc.), and the like.

In this method, it is preferable to develop with a positive type image, and FIG. 1 (d) shows a mode in which the image is patterned with a positive type image.

Then, as shown in FIG. 1D, the polybenzoxazole precursor 4 is made porous by removing the dispersible compound 3 from the photosensitive resin composition 2.

As a method of removing the dispersible compound from the photosensitive resin composition, a known method such as volatilization by heating, decomposition and carbonization, or extraction with a specific solvent is used. Of these methods, the method of extracting with a specific solvent is preferable. By extracting with a solvent, the residue of the dispersible compound that cannot be completely removed by heating can be removed, and the dielectric constant can be further reduced.

The extraction solvent may be a commonly used organic solvent, and may be appropriately selected depending on the composition of the polybenzoxazole precursor and the kind of the dispersible compound. Examples of such an organic solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, diglyme, and triglyme. Such as a polar solvent, for example, tetrahydrofuran, an ether solvent such as dioxane, for example, cyclohexanone, methyl ethyl ketone, a ketone solvent such as acetone, for example, an aromatic hydrocarbon solvent such as toluene, xylene, for example, methanol, ethanol, isopropanol Examples thereof include alcohol solvents. They may be used alone or in combination of two or more.

In the extraction method, it is particularly preferable to use liquefied carbon dioxide or carbon dioxide in a high temperature and high pressure state or a supercritical state. If extraction is performed using such carbon dioxide, the extraction efficiency can be markedly improved and good porosity can be achieved. When using such carbon dioxide, for example,
0 to 150 ° C in the pressure vessel, and further 20 to 120
3.5 to 100 MPa, further 6 to 50 MP at ℃
It is preferable to carry out the extraction with a.

The step of removing the dispersible compound from the photosensitive resin composition may be performed at any step in the step of obtaining the porous resin from the photosensitive resin composition of the present invention. It may be done independently or throughout the entire process. That is, in this description, this step is described as a step after patterning the photosensitive resin composition and before curing the photosensitive resin composition described below, but a solvent is removed from the photosensitive resin composition. It may be carried out in any step as long as it is removed to form a state in which the dispersible compound is dispersed in the polybenzoxazole precursor. Before exposure of the photosensitive resin composition, after exposure, before heating, and after heating. It may be performed before development, after development, before and after the curing described below, or plural times in each of these steps.

Then, as shown in FIG. 1E, by curing the photosensitive resin composition 2 thus formed, the insulating layer 6 made of the porous resin of the present invention can be obtained. The curing may be performed by a known method, and for example, it is preferable to heat at a temperature of about 350 ° C. to 400 ° C. for several hours in a vacuum, an inert gas atmosphere or an air atmosphere. As a result, the polybenzoxazole precursor is cyclized to form an insulating layer of a porous resin made of polybenzoxazole resin.

For use as a circuit board, for example, as shown in FIG. 2A, the insulating layer 6 is used as the base layer 6 and the conductor layer 7 is formed on the base layer 6.
Are formed into a predetermined circuit pattern by a known patterning method such as a subtractive method, an additive method, a semi-additive method, and then, as shown in FIG.
As shown in (b), if necessary, the conductor layer 7 may be covered with a cover layer 8 made of an insulating layer. In addition,
As the conductor for forming the conductor layer, for example, copper, nickel, gold, solder, or an alloy thereof is used, and the thickness thereof is usually 1 to 15 μm. Further, as the cover layer, the porous resin of the present invention may be used,
Moreover, you may use the other well-known resin normally used as a cover layer. The thickness of the cover layer is usually 2 to 2
It is 5 μm.

Since the insulating layer thus obtained is made of polybenzoxazole resin, it has high heat resistance, dimensional stability, and insulating performance, and is uniform and fine with a size of less than 10 μm, further less than 5 μm. Since it has bubbles, it is possible to form a circuit pattern with a fine line and space, and a dielectric constant of 3 or less.
Since it has a low dielectric constant of 2.5 or less, high frequency characteristics can be improved. Therefore, a circuit board, preferably,
It can be suitably used as a base layer, a cover layer or an intermediate insulating layer of a flexible wiring board, and a circuit board having such an insulating layer is effectively used as a circuit board capable of transmitting high frequency electric signals at high speed. be able to.

In particular, when the insulating layer made of the porous resin of the present invention is used as the insulating layer of the suspension board with circuit for mounting the magnetic head of the hard disk drive,
The suspension board with circuit having such an insulating layer can transmit a large amount of information read and written by the magnetic head at high speed.

Next, the specific mode of using the porous resin of the present invention as such a suspension board with circuit will be described in detail.

FIG. 3 is a perspective view of an embodiment of a suspension board with circuit in which the porous resin of the present invention is used as an insulating layer.

In FIG. 3, the suspension board with circuit 11 is mounted with a magnetic head (not shown) of a hard disk drive, and the magnetic head is used for air flow when the magnetic head and the magnetic disk travel relatively. It is to support the magnetic disk while maintaining a minute gap between the magnetic disk and the magnetic disk, and the wiring for connecting the magnetic head and the read / write substrate as an external circuit has a predetermined circuit. It is integrally formed as a pattern.

Such a suspension board with circuit 11
On the supporting substrate 12 extending in the longitudinal direction, the base layer 1
3 is formed, and the conductor layer 14 formed as a predetermined circuit pattern is formed on the base layer 13. The circuit pattern includes a plurality of wirings 14a, 14b, which are arranged in parallel with each other at a predetermined distance.
It is composed of 14c and 14d. Support substrate 12
A gimbal 15 for mounting a magnetic head is formed at the tip of the substrate by cutting the support substrate 12. Further, a magnetic head side connection terminal 16 for connecting the magnetic head to each of the wirings 14a, 14b, 14c, 14d is formed at the tip of the support substrate 12, and at the rear end of the support substrate 12. Is formed with external connection terminals 17 for connecting the read / write substrate and the respective wirings 14a, 14b, 14c, 14d. In addition,
Although not shown in FIG. 3, the conductor layer 14 is actually covered with a cover layer 18 made of an insulator.

Next, one embodiment of a method of manufacturing such a suspension board with circuit 11 will be described in detail with reference to FIGS. In addition, in FIG. 4 to FIG.
The middle of the suspension board with circuit 11 in the longitudinal direction is shown as a cross section along a direction orthogonal to the longitudinal direction of the suspension board with circuit 11.

First, as shown in FIG. 4, the support substrate 12 is prepared, and the base layer 13 is formed on the support substrate 12 in a predetermined pattern. As the support substrate 12, it is preferable to use a metal foil or a metal thin plate, and for example, stainless steel, 42 alloy or the like is preferably used. The thickness is 10 to 60 μm, and further 15 to 3
0 μm, the width is 50 to 500 mm, and further 12
Those having a diameter of 5 to 300 mm are preferably used.

First, as shown in FIG.
As shown in FIG. 4B, a photosensitive resin composition is applied to the surface of the supporting substrate 12 prepared in advance and then dried at 40 ° C. to 120 ° C., as shown in FIG. 4B.
The solvent is removed to disperse the dispersible compound 3 in the polybenzoxazole precursor 4, and the film 13a of the photosensitive resin composition is formed.

Next, as shown in FIG. 4C, the film 13a is exposed through a photomask 24 and then developed with a positive image or a negative image to form the film 13a into a predetermined pattern. Use as a pattern. Note that the photomask 2
The exposure wavelength of the irradiation ray radiated via 4 is 300
To 450 nm, more preferably 350 to 420 nm, and the integrated light quantity of exposure is 100 to 5000.
mJ / cm ^2, and further, 200~3000mJ / cm ²
Is preferred. Note that FIG. 4 shows a mode in which a positive image is patterned.

Then, as shown in FIG. 4D, the film 1
The polybenzoxazole precursor 4 is made porous by removing the dispersible compound 3 from 3a. The dispersible compound 3 may be removed by any of heating, decomposition and extraction, but extraction is preferably used.

Next, as shown in FIG. 4 (e), the coating film 13a of the polybenzoxazole precursor 4 is formed at 350 ° C.
By heating at about 400 ° C. for several hours, the polybenzoxazole precursor 4 is cyclized to form the porous base layer 13 made of a polybenzoxazole resin. The thickness of the base layer 13 thus formed is usually 2 to 20 μm, preferably 5 to 10 μm.
Is.

Then, as shown in FIG.
The conductor layer 14 is formed thereon with a predetermined circuit pattern.
As the conductor for forming the conductor layer 14, any conductor can be used as a conductor of the suspension board with circuit.
It can be used without particular limitation. As such a conductor, for example, copper, nickel, gold, solder, or an alloy thereof is used, and preferably,
Copper is used. In addition, the conductor layer 1 has a predetermined circuit pattern.
4 may be formed by any known patterning method such as a subtractive method, an additive method, a semi-additive method, etc., but a semi-additive method is preferably used. That is, first, as shown in FIG. 5A, a thin film of a conductor serving as the base 20 is formed on the entire surfaces of the support substrate 12 and the base layer 13. For forming the base 20, a vacuum vapor deposition method, particularly a sputter vapor deposition method is preferably used. In addition, chromium, copper, or the like is preferably used for the conductor that becomes the base 20. More specifically, for example, it is preferable to sequentially form a chromium thin film and a copper thin film on the entire surface of the support substrate 12 and the base layer 13 by a sputter deposition method. The thickness of the chromium thin film is 10
The thickness of the copper thin film is preferably 0 to 600Å and the thickness of the copper thin film is preferably 500 to 2000Å.

Next, as shown in FIG. 5B, a plating resist 21 having a pattern opposite to the predetermined circuit pattern is formed on the underlayer 20. The plating resist 21 may be formed into a predetermined resist pattern by a known method using, for example, a dry film resist. Next, as shown in FIG. 5C, a portion of the base layer 13 where the plating resist 21 is not formed is
The conductor layer 14 having a predetermined circuit pattern is formed by plating. Plating may be either electrolytic plating or electroless plating, but electrolytic plating is preferably used, among which,
Electrolytic copper plating is preferably used. Note that this circuit pattern includes, for example, as shown in FIG. 1, a plurality of wirings 14 arranged in parallel with each other at a predetermined interval.
It is formed as a, 14b, 14c and 14d patterns.
The conductor layer 14 has a thickness of usually 2 to 50 μm, preferably 5 to 30 μm, and each of the wirings 14 a, 14 b, 14
The widths of c and 14d are usually 5 to 500 μm, preferably 10 to 200 μm, and the respective wirings 14a, 14b,
The distance between 14c and 14d is usually 5 to 500 μm, preferably 10 to 200 μm.

Then, as shown in FIG. 5 (d), the plating resist 21 is removed by a known etching method such as chemical etching (wet etching) or peeling, and then as shown in FIG. 5 (e). Similarly, the base 20 on which the plating resist 21 has been formed is removed by a known etching method such as chemical etching (wet etching). Thereby, on the base layer 13,
The conductor layer 14 is formed as a predetermined circuit pattern.

Next, as shown in FIG. 6, after the surface of the conductor layer 14 is protected by the metal film 22, the conductor layer 14 is protected.
Are covered with a cover layer 18 made of an insulator. That is, first, as shown in FIG. 6A, the metal film 22 is formed on the surface of the conductor layer 14 and the surface of the support substrate 12. The metal film 22 is preferably formed as a hard nickel thin film by electroless nickel plating, and its thickness may be such that the surface of the conductor layer 14 is not exposed, and is, for example, 0.05 to 0.2 μm. It only has to be about.

Next, the cover layer 18 for covering the conductor layer 14 is formed. The cover layer 18 includes the base layer 13
Similarly to the above, a photosensitive resin composition is used, and as shown in FIG. 6B, a porous cover layer 18 made of polybenzoxazole resin is produced by the same method as the base layer 13.
To form. Although the thickness of the cover layer 18 thus formed depends on the thickness of the conductor layer 14, it is usually 2
-25 μm, preferably 5-20 μm.

Then, as shown in FIG. 6C, the metal film 22 formed on the support substrate 12 is peeled off.
Although not shown in the drawing, the magnetic head side connection terminal 16 and the external side connection terminal 17 are formed so that the respective terminal portions are not covered by the cover layer 18 in the formation of the cover layer 18, and the support substrate 12 of the support substrate 12 is formed. At the same time when the metal film 22 formed on the upper side is peeled off, the surface of the exposed conductor layer 14 is sequentially subjected to electrolytic nickel plating and electrolytic gold plating after peeling off the metal film 22 of each terminal portion. Form. The thickness of each of the nickel plating layer and the gold plating layer is preferably about 0.2 to 5 μm.

Then, the plating leads used for electrolytic nickel plating and electrolytic gold plating are removed by chemical etching or the like, and the support substrate 12 is cut out into a predetermined shape such as the gimbal 15 by a known method such as chemical etching and washed. Then, by drying, the suspension board with circuit 11 as shown in FIG. 3 is obtained.

Since the suspension board with circuit 11 thus obtained has a low dielectric constant and good high frequency characteristics, it can transfer a large amount of information read and written by the magnetic head at high speed. You can

[0077]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the Examples and Comparative Examples.

Synthesis Example 1 (Synthesis of Polybenzoxazole Precursor A) In a flask having a dry nitrogen introducing tube, 3,3′-
Diamino-4,4'-dihydroxyphenyl ether 4
6.4 parts by weight (0.2 mol) was dissolved in 110 parts by weight of dried N, N-dimethylacetamide, and 26.82 parts by weight (0.2 mol) of isophthalaldehyde was added thereto. Then, the mixture was stirred at room temperature for 48 hours in a dry nitrogen atmosphere to prepare a solution of polybenzoxazole precursor A.

Synthesis Example 2 (Synthesis of Polybenzoxazole Precursor B) 73.25 parts by weight of 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane (in a flask having a dry nitrogen introducing tube) 0.2 mol) was dissolved in 150 parts by weight of dried N, N-dimethylacetamide, and 26.82 parts by weight (0.2 mol) of isophthalaldehyde was added thereto. Then, the mixture was stirred at room temperature for 48 hours in a dry nitrogen atmosphere to prepare a solution of polybenzoxazole precursor B.

Example 1 A solution of the polybenzoxazole precursor A obtained in Synthesis Example 1 was added with a sensitizer (2,3,4-tris (1-oxo-2).
-Diazonaphthoquinone-4-sulfonyloxy) benzophenone as its polybenzoxazole precursor A10
While adding 20 parts by weight to 0 parts by weight, 40 parts by weight of a urethane acrylate oligomer having a weight average molecular weight of 750 was added to 100 parts by weight of the polybenzoxazole precursor A, and stirring the mixture to obtain a transparent and uniform photosensitive material. A resin composition was obtained. This photosensitive resin composition has a thickness of 2
A 5 μm stainless steel foil (SUS304) was applied using a spin coater so that the thickness of the dried film was 7 μm, and dried by heating at 100 ° C. for 10 minutes to obtain N, N.
-By removing dimethylacetamide, a film was formed in the polybenzoxazole precursor A such that a sea-island structure of urethane acrylate oligomer was formed.

Next, an exposure amount of 20 is applied through a photomask.
Ultraviolet rays (λ = 350 to 435 nm) at 0 mJ / cm ² .
Was exposed to light and developed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution to form a pattern with a positive image.

The pattern of this coating was cut into a sheet of 80 mmφ, placed in a 500 mL pressure-resistant container, pressurized to 25 MPa / cm ² in an atmosphere of 40 ° C., and the amount of gas was maintained at about 3 L while maintaining the pressure. The operation of injecting carbon dioxide at a flow rate of / min and exhausting it to extract the urethane acrylate oligomer was carried out for 2 hours. Then, it was heated at 300 ° C. for 1 hour and further heated at 360 ° C. under a reduced pressure of 1.33 Pa to prepare a film made of a porous polybenzoxazole resin.

The size of the bubbles determined by image-processing the SEM observation image of the cross section of the obtained porous film was 1.8 μm, and the dielectric constant was 2.4 (1 MHz).

The measurement conditions are as follows (the same applies to the following Examples and Comparative Examples).

SEM observation: The produced porous sheet was frozen in liquid nitrogen and cut, and its cross section was observed using a scanning electron microscope (SEM) (Hitachi S-570 type).
It was observed at an acceleration voltage of 10 kv.

Dielectric constant: Measured by HP4284A precision LCR meter manufactured by Yokogawa Hewlett-Packard Company.

Example 2 A solution of the polybenzoxazole precursor A obtained in Synthesis Example 1 was added with a photosensitizer (2,3,4-tris (1-oxo-2).
-Diazonaphthoquinone-4-sulfonyloxy) benzophenone as its polybenzoxazole precursor A10
While adding 30 parts by weight to 0 parts by weight, 40 parts by weight of a polyethylene glycol dimethyl ether oligomer having a weight average molecular weight of 1200 was added to 100 parts by weight of the polybenzoxazole precursor A, and the mixture was stirred to give a transparent and uniform mixture. A photosensitive resin composition was obtained. This photosensitive resin composition was applied to a stainless foil (SUS30) having a thickness of 25 μm.
4) was coated on the above using a spin coater so that the thickness of the dried film would be 8 μm, and dried by heating at 100 ° C. for 10 minutes to remove N, N-dimethylacetamide. A film was formed in the benzoxazole precursor A so that a sea-island structure of polyethylene glycol dimethyl ether oligomer was formed.

Next, an exposure amount of 20 is applied through a photomask.
Ultraviolet rays (λ = 350 to 435 nm) at 0 mJ / cm ² .
Was exposed to light and developed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution to form a pattern with a positive image.

The pattern of this film was cut into a sheet of 80 mmφ, placed in a 500 mL pressure-resistant container, pressurized to 25 MPa / cm ² in an atmosphere of 40 ° C., and the amount of gas was maintained at about 3 L while maintaining the pressure. The operation of injecting carbon dioxide at a flow rate of / min and exhausting it to extract polyethylene glycol dimethyl ether oligomer was carried out for 2 hours. afterwards,
The film was heated at 300 ° C. for 1 hour and further heated at 360 ° C. under a reduced pressure of 1.33 Pa under vacuum to form a film made of a porous polybenzoxazole resin.

The size of the bubbles obtained by image-processing the SEM observation image of the cross section of the obtained porous film was 1.6 μm, and the dielectric constant was 2.5 (1 MHz).

Example 3 A solution of the polybenzoxazole precursor B obtained in Synthesis Example 2 was added with a photosensitizer (2,3,4-tris (1-oxo-2).
-Diazonaphthoquinone-4-sulfonyloxy) benzophenone as its polybenzoxazole precursor B10
While adding 30 parts by weight to 0 parts by weight, 40 parts by weight of a polyethylene glycol diacrylate oligomer having a weight average molecular weight of 600 is added to 70 parts by weight of the polybenzoxazole precursor B, and the mixture is stirred to give a transparent and uniform mixture. To obtain a photosensitive resin composition. This photosensitive resin composition was applied onto a stainless steel foil (SUS304) having a thickness of 25 μm by using a spin coater so that the film thickness after drying was 8 μm.
m and then heat-dried at 100 ° C. for 10 minutes to remove N, N-dimethylacetamide to form a sea-island structure of polyethylene glycol diacrylate oligomer in the polybenzoxazole precursor B. Formed a film like that.

Then, an exposure amount of 20 is applied through a photomask.
Ultraviolet rays (λ = 350 to 435 nm) at 0 mJ / cm ² .
Was exposed to light and developed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution to form a pattern with a positive image.

The pattern of this coating was cut into a sheet of 80 mmφ, placed in a 500 mL pressure-resistant container and pressurized to 25 MPa / cm ² in an atmosphere of 40 ° C., and then the pressure was maintained to a gas volume of about 3 L. The operation of injecting carbon dioxide at a flow rate of / min and exhausting it to extract the polyethylene glycol diacrylate oligomer was carried out for 2 hours. Then 3
The film was heated at 00 ° C. for 1 hour and further heated at 360 ° C. under a reduced pressure of 1.33 Pa to prepare a film made of a porous polybenzoxazole resin.

The size of the bubbles obtained by image-processing the SEM observation image of the cross section of the obtained porous film was 0.8 μm, and the dielectric constant was 2.2 (1 MHz).

Comparative Example 1 A solution of the polybenzoxazole precursor A obtained in Synthesis Example 1 was added with a photosensitizer (2,3,4-tris (1-oxo-2).
-Diazonaphthoquinone-4-sulfonyloxy) benzophenone as its polybenzoxazole precursor A10
30 parts by weight was added to 0 parts by weight and stirred to obtain a transparent and uniform photosensitive resin composition. This photosensitive resin composition was applied onto a stainless steel foil (SUS304) having a thickness of 25 μm using a spin coater so that the film thickness after drying was 15
The coating was applied so as to have a thickness of 10 μm, and the coating was heated and dried at 100 ° C. for 10 minutes to remove N, N-dimethylacetamide, thereby forming a film of polybenzoxazole precursor A. It was confirmed by SEM observation that this was a uniform film having no sea-island structure.

Then, an exposure amount of 20 is applied through a photomask.
Ultraviolet rays (λ = 350 to 435 nm) at 0 mJ / cm ² .
Was exposed to light and developed with a 2.38 wt% tetramethylammonium hydroxide aqueous solution to form a pattern with a positive image.

After cutting the pattern of this film into a sheet of 80 mmφ, it was heated at 300 ° C. for 1 hour, and further,
A film made of polybenzoxazole resin was produced by heating at 360 ° C. under a reduced pressure of 1.33 Pa.

SEM observation of the cross section of the obtained film was performed, but no bubbles were observed. The dielectric constant is 3.0
(1 MHz).

[0099]

As described above, the photosensitive resin composition of the present invention has high heat resistance, dimensional stability and insulation performance,
Moreover, it is possible to obtain a porous resin which has uniform and fine bubbles and has a low dielectric constant and which can easily form a fine pattern.
Therefore, the obtained porous resin can form a fine circuit pattern and has a low dielectric constant. Therefore, if it is used as an insulating layer of a circuit board, the high frequency characteristics of the circuit board can be improved. it can. Therefore, the circuit board having such an insulating layer can be effectively used as a circuit board capable of transmitting high-frequency electric signals at high speed.

In particular, when used as an insulating layer of a suspension board with circuit, high frequency characteristics are excellent. Therefore, a suspension board with circuit having such an insulating layer is
A large amount of information read and written by the magnetic head can be transmitted at high speed.

[Brief description of drawings]

FIG. 1 is a process chart of an embodiment showing a method for forming an insulating layer of a circuit board made of a porous resin using the photosensitive resin composition of the present invention, in which (a) shows a base material. The step of preparing, (b) is a step of forming a film of the photosensitive resin composition on the substrate, and (c) is the step of exposing the film through a photomask and developing the film. , A step of forming a predetermined pattern, (d) a step of making the polybenzoxazole precursor porous by removing the dispersible compound from the photosensitive resin composition, (e) curing the porous film Then, the step of forming the base layer will be described.

FIG. 2 is a cross-sectional view showing a step of forming a conductor layer and a cover layer on a base layer, wherein (a) is a step of forming a conductor layer on a base layer, and (b) is a conductor. The process of forming a cover layer on a layer is shown.

FIG. 3 is a perspective view of an embodiment of a suspension board with circuit in which the porous resin of the present invention is used as an insulating layer.

FIG. 4 is a cross-sectional view showing a step of preparing a support substrate and forming a base layer on the support substrate in a predetermined pattern, FIG. )
Is a step of forming a film of the photosensitive resin composition on the supporting substrate, and (c) is a step of exposing the film through a photomask and developing the film to form a predetermined pattern. , (D) is a step of making the polybenzoxazole precursor porous by removing the dispersible compound from the photosensitive resin composition, and (e) curing the porous film to form a base layer. The process of doing is shown.

FIG. 5 is a cross-sectional view showing a step of forming a conductor layer with a predetermined circuit pattern on a base layer, FIG. 5A is a step of forming a base on a support substrate and a base layer, and FIG.
Is a step of forming a plating resist having a pattern opposite to the predetermined circuit pattern on the underlayer. The step of forming
(D) is a step of removing the plating resist, (e) is
A step of removing the base is shown.

FIG. 6 is a cross-sectional view showing a step of covering the surface of the conductor layer with a metal film and then covering with a cover layer,
(A) is a step of forming a metal film on the surface of the conductor layer,
(B) shows a step of forming a cover layer on the base layer and the metal coating, and (c) shows a step of peeling the metal coating formed on the supporting substrate.

[Explanation of symbols]

1 base material 2 Photosensitive resin composition 3 Dispersible compounds 4 Polybenzoxazole precursor 6 insulating layers

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03F 7/022 G03F 7/022 H05K 1/03 610 H05K 1/03 610H 1/05 1/05 A 3 / 46 3/46 T // C08L 79:08 C08L 79:08 A (72) Inventor Naotaka Kaneshiro 1-2-1 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (72) Inventor Takashi Kondo Ibaraki, Osaka Prefecture Hozumi Ichishita 1-2, Nitto Denko Co., Ltd. (reference) 2H025 AA00 AA10 AA20 AB15 AC01 AD01 AD03 BE01 BH00 CC05 CC20 FA12 4F074 AA75 CB01 CB03 CB16 CB17 CC22 DA47 DA54 4J043 PA01 QB44 RA01 RA11 SA02 SA06 UA13 UB05 UB06 UB12 XA11 XA13 XA16 XA19 YA05 ZB22 5E315 AA02 AA03 BB01 BB14 CC01 DD29 GG22 5E346 AA02 AA03 AA12 AA15 BB01 CC08 CC31 DD03 DD31 GG01 GG02 HH06

Claims (8)

[Claims] 1. A polybenzoxazole precursor having a repeating unit structure represented by the following general formula (1), a photosensitizer, a dispersible compound dispersible in the polybenzoxazole precursor, and a solvent. A photosensitive resin composition comprising: [Chemical 1] (In the formula, R1 represents any of an ether bond, a carbon-carbon bond, and methylene which may be substituted, and R2
Is (A is the same or different and represents a hydrogen atom or a halogen atom). ) 2. The photosensitive resin composition according to claim 1, wherein the dispersible compound is at least one selected from the group consisting of polyacrylate oligomers, polyether oligomers, polyester oligomers and polyurethane oligomers. object. 3. A step of forming a state in which a dispersible compound is dispersed in the polybenzoxazole precursor by removing the solvent from the photosensitive resin composition according to claim 1 or 2, and the dispersible compound is removed. The step of making porous,
And a porous resin obtained by a step including a step of curing a photosensitive resin composition. 4. The porous resin according to claim 3, further comprising a step of patterning the photosensitive resin composition by exposing and developing the photosensitive resin composition. 5. The porous resin according to claim 3, which is used as an insulating layer of a circuit board. 6. The porous resin according to claim 3, which is used as an insulating layer of a suspension board with circuit. 7. A circuit board comprising the porous resin according to claim 3 as an insulating layer. 8. A suspension board with circuit, comprising the porous resin according to claim 3 or 4 as an insulating layer.