JP2011124543A - Method of manufacturing flexible printed wiring board and method of forming terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove red discoloration of the surface of a conductor pattern when forming a flexible printed wiring board using a photosensitive polyimide resin composition to which bismuthiol is added. <P>SOLUTION: The method of manufacturing a flexible printed wiring board includes (a) a step of forming a conductor pattern 2 on a base material and acquiring a substrate, (b) a step of forming a photosensitive resin layer 5 formed of a photosensitive polyimide resin composition containing polyimide resin, a photosensitizing agent, a cross-linker, and bismuthiol on the surface of the substrate at a side on which the conductor pattern is formed, (c) a step of removing the photosensitive resin layer of a corresponding region in such a manner that the conductor pattern of a desired region (a terminal part 4) is exposed by allowing the photosensitive resin layer to be subjected to photolithography processing, (d) a step of performing soft etching of the exposed conductor pattern (the terminal 4) using chemical polishing solution, and (e) a step of crosslinking the photosensitive resin layer to crosslink the cross-linker, and thereby allowing the photosensitive resin layer to be a coverlay layer 5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a flexible printed wiring board having a coverlay layer to which bismuththiol is added to improve electrolytic plating resistance.

  When manufacturing a flexible printed wiring board, a photosensitive polyimide resin composition comprising a polyimide resin mixed with a naphthoquinonediazide-based photosensitive agent and an epoxy-based crosslinking agent on a polyimide-based copper pattern side surface on which a copper pattern is formed. The cover layer is formed by performing exposure and development processing so that the terminal portion of the copper pattern is opened, and further performing heat crosslinking processing on the obtained photosensitive resin layer.

  By the way, the flexible printed wiring board has a laminated structure of organic matter and inorganic matter. At this time, there is a concern that the substrate may be warped depending on the material constituting the laminate. Therefore, it is conceivable to reduce the elastic modulus of the coverlay layer itself as one of the important approaches for preventing the warpage of these wiring boards. From this viewpoint, it has been proposed to use siloxane diamine as one of a plurality of diamine components constituting the polyimide resin (Patent Documents 1 to 3).

JP 2003-131371 A JP 2008-216984 A JP 2009-68002 A

  However, in the case of a coverlay layer formed by applying a conventional photosensitive polyimide resin composition using a siloxane polyimide resin, although the elastic modulus is low, the area of the coverlay layer corresponding to the terminal portion of the copper pattern is photolithography When metal is deposited on the exposed copper pattern by electrolytic plating, the plating solution enters the boundary between the copper pattern and the coverlay layer from the inner bottom corner of the opening, and metal plating is deposited on unintended parts. However, there was a problem that it caused discoloration of the coverlay layer. This problem was remarkable when the electrolytic gold plating was deposited directly without performing electroless Ni or Au plating.

  Under the assumption that the above-mentioned problems can be solved by blending various heterocyclic thiol compounds with a photosensitive polyimide resin composition containing a siloxane polyimide resin, the present inventor has various heterocyclic thiols. As a result of screening compounds, there is a heterocyclic thiol compound that can not only improve the electroplating resistance but also the adhesion before plating, and bismuthiol (2,5-dimercapto-1,3,4-thiadiazole) is the above-mentioned. It was found that the problem can be solved. The effect of improving the electroplating resistance of this bismuthiol can also be expected for a photosensitive polyimide resin composition containing a general polyimide resin other than a siloxane polyimide resin.

  Then, when the flexible printed wiring board was created using the photosensitive polyimide resin composition which added bismuthiol, the problem that the surface of the exposed copper pattern turned red this time occurred. Such discoloration may cause uneven plating.

  The present invention is intended to solve the above-described problems of the prior art, and when forming a flexible printed wiring board using a photosensitive polyimide resin composition to which bismuththiol is added, the surface of the exposed conductor pattern is formed. The purpose is to be able to remove discoloration.

  The present inventors provided an opening in the photosensitive resin layer by photolithographic processing of the photosensitive resin layer, and then followed by photolithographic processing prior to post-baking processing for crosslinking and curing the photosensitive resin layer. The inventors have found that the surface of the exposed conductor pattern can be removed by performing a soft etching treatment with a chemical polishing liquid, and have completed the present invention.

That is, the present invention provides the following steps (a) to (e) in a method for producing a flexible printed wiring board having a substrate having a conductor pattern formed on a base material and a coverlay layer formed on the substrate. ):
(A) obtaining a substrate by forming a conductor pattern on a substrate;
(B) A photosensitive resin layer made of a photosensitive polyimide resin composition containing a polyimide resin, a photosensitive agent, a crosslinking agent, and bismuthiol is formed on the surface of the substrate on which the conductor pattern is formed. Process;
(C) removing the photosensitive resin layer in a corresponding region so that a conductive pattern in a desired region (terminal portion) is exposed by performing a photolithography process on the photosensitive resin layer;
(D) a step of soft-etching the exposed conductor pattern (terminal portion) with a chemical polishing liquid; and (e) a crosslinking treatment of the photosensitive resin layer to crosslink the crosslinking agent, thereby covering the photosensitive resin layer. A step of forming a lay layer;
A manufacturing method characterized by comprising:

In addition, the present invention provides the terminal part formation of a flexible printed wiring board having a substrate in which a conductor pattern having a terminal part is formed on a base material and a coverlay layer formed on the substrate excluding the terminal part. A method comprising the following steps (a) to (e):
(A ′) a step of obtaining a substrate by forming a conductor pattern having a terminal portion on a substrate;
(B ′) A photosensitive resin layer made of a photosensitive polyimide resin composition containing a polyimide resin, a photosensitive agent, a crosslinking agent, and bismuthiol is formed on the surface of the substrate on which the conductor pattern is formed. The step of:
(C ′) removing the photosensitive resin layer in the corresponding region so that the terminal portion is exposed by subjecting the photosensitive resin layer to a photolithography process;
(D ′) a step of soft-etching the exposed terminal portion with a chemical polishing liquid; and (e ′) a crosslinking treatment of the photosensitive resin layer by crosslinking the photosensitive resin layer, thereby forming the photosensitive resin layer as a coverlay layer. The step of:
The terminal part formation method characterized by having.

  In the method for manufacturing a flexible printed wiring board or the terminal portion forming method of the present invention, a post for crosslinking and curing the photosensitive resin layer after providing an opening in the photosensitive resin layer by photolithography of the photosensitive resin layer. Prior to the baking process, a soft etching process is performed with a chemical polishing liquid following the photolithography process. For this reason, discoloration of the surface of the exposed conductor pattern can be removed.

FIG. 1 is a process explanatory diagram of the method for producing a flexible printed wiring board of the present invention. FIG. 2 is a process explanatory diagram of the method for producing a flexible printed wiring board of the present invention. FIG. 3 is a process explanatory diagram of the method for producing a flexible printed wiring board of the present invention. FIG. 4 is a process explanatory diagram of the method for producing a flexible printed wiring board of the present invention. FIG. 5 is a process explanatory diagram of the method for producing a flexible printed wiring board of the present invention.

  The method for producing a flexible printed wiring board of the present invention is a method for producing a flexible printed wiring board having a substrate in which a conductor pattern is formed on a base material and a coverlay layer formed on the substrate. Steps (a) to (e), and if necessary, further include step (f). Below, it demonstrates in detail for every process, referring drawings.

<< Step (a) >>
As shown in FIG. 1, a conductor pattern 2 is formed on a base material 1 to obtain a substrate 3. The conductor pattern 2 can have a region to be the terminal portion 4.

  As the base material 1 constituting the substrate 3, a resin film conventionally used as a base material for flexible printed wiring boards can be used. For example, a polyimide film having a linear thermal expansion coefficient approximate to that of a copper foil is preferable. Can be used. The thickness of such a resin film is usually 12 to 25 μm.

  The conductor pattern 2 constituting the substrate 3 is obtained by forming a conductor layer such as a copper foil having a thickness of 9 to 35 μm laminated on the base material 1 by a known patterning technique such as a photolithography technique. Therefore, it is preferable to use a copper-clad laminate in which a copper foil is laminated on a polyimide film base material as an original fabric for forming the substrate 3. A desired region of the conductor pattern 2 is designated as the terminal portion 4.

<< Step (b) >>
As shown in FIG. 2, a photosensitive resin comprising a photosensitive polyimide resin composition containing a polyimide resin, a photosensitive agent, a crosslinking agent, and a bismuth thiol on the surface of the substrate 3 on which the conductor pattern 2 is formed. The conductive resin layer 5 ′ is formed. The thickness of the photosensitive resin layer 5 ′ is preferably 5 to 30 μm, and more preferably 10 to 25 μm, because if the thickness is too thin, the insulating property is lowered.

  As a method of forming the photosensitive resin layer 5 ′ composed of the photosensitive polyimide resin composition, a coating technique using a known coating apparatus such as a spin coater or a bar coater can be applied. You may perform a drying process after coating as needed. In that case, it is preferable to carry out so that the crosslinking reaction by the crosslinking agent does not proceed.

  The photosensitive polyimide resin composition used in the present invention contains a polyimide resin, a photosensitive agent, a cross-linking agent, and further a bismuth thiol. For this reason, favorable adhesiveness and electroplating tolerance can be provided to the coverlay layer formed by application | coating of this photosensitive polyimide resin composition.

  When the content of the bismuthiol in the photosensitive polyimide resin composition is too small, the electroplating resistance becomes insufficient, and when the content is too large, blackening of the copper pattern occurs due to the formation of copper copper sulfide when the conductor pattern is a copper pattern. Since there is concern, it is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 1 part by mass with respect to 100 parts by mass of the polyimide resin.

  The polyimide resin which comprises the photosensitive polyimide resin composition can use the well-known thing applied to the coverlay layer of a flexible printed circuit board. For example, an acid dianhydride component containing an aromatic acid dianhydride and an diamine containing an aromatic diamine are imidized.

  As aromatic acid dianhydride, pyromellitic tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenyl ether tetracarboxylic acid Dianhydride, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propanoic dianhydride, 1,4,5, 8-naphthalenetetracarboxylic dianhydride, 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride, 9,9-bis (3,4-dicarboxyphenyl) fluorenic dianhydride, 9,9 -Bis [4- (3,4-dicarboxyphenoxy) phenyl] fluorenic acid dianhydride, 1,2,3,4-cyclobutanoic acid dianhydride and the like can be mentioned. Two or more of these can be used in combination. Of these, 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride is preferably used from the viewpoint of enhancing alkali solubility, which is the basis for imparting positive photosensitivity.

  As an acid dianhydride component, in addition to the above-mentioned compounds, an acid dianhydride similar to that used as an acid dianhydride component of a general polyimide resin as long as the effects of the present invention are not impaired (patent No. 3363600, paragraph 0009) can be used in combination.

  As aromatic diamines, m-xylidinediamine, p-phenylenediamine, m-phenylenediamine, toluylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,4'-diamino Diphenyl ether, 4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl, 4,4′-diaminodiphenyl sulfide, 2,6-diaminonaphthalene, 4,4′-bis (p- Aminophenoxy) diphenylsulfone, 4,4′-bis (m-aminophenoxy) diphenylsulfone, 4,4′-bis (p-aminophenoxy) benzophenophene, 4,4′-bis (m-aminophenoxy) benzo Phenophene, 4,4'-bis (p-aminophenylmercapto) benzo Enon, 4,4'-bis (p- aminophenyl mercapto) can be mentioned diphenyl sulfone. Two or more of these can be used in combination.

  Moreover, the siloxane polyimide resin obtained by using various siloxane diamine as at least one of a diamine component can be used as a polyimide resin. When a siloxane polyimide resin is used, the elastic modulus of the coverlay layer can be reduced and the warp of the flexible printed wiring board can be reduced.

  As such a siloxane polyimide resin, for example, the siloxane polyimide resins described in the aforementioned Patent Documents 1 to 3 can be preferably used. Especially, the siloxane polyimide resin of patent document 3 which has an amide bond in the principal chain demonstrated below can be preferably used at the point which can improve the adhesiveness to a conductor pattern.

  Such a siloxane polyimide resin comprises a diamine component containing an amide group-containing siloxane diamine compound represented by the following formula (1), and an acid dianhydride component containing at least one kind of aromatic acid dianhydride described above. , Imidized.

  Here, the amide group-containing siloxane diamine compound which is an essential diamine component of the siloxane polyimide resin has a chemical structure of the formula (1).

In formula (1), R ¹ and R ² are each an alkylene group that may be independently substituted. Specific examples thereof include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, Mention may be made of a hexamethylene group. Examples of the substituent include a lower alkyl group such as a methyl group and an ethyl group, and an aryl group such as a phenyl group. Among these, a trimethylene group is desirable because of the availability of raw materials. In addition, R ¹ and R ² are the same and may be different from each other, but if they are different, it is difficult to obtain raw materials, and it is preferable that they are the same.

  Moreover, although m is an integer of 1-30, Preferably it is 1-20, More preferably, it is an integer of 2-20. This is because when m is 0, it is difficult to obtain raw materials, and when m exceeds 30, it is separated without being mixed with the reaction solvent. On the other hand, n is an integer of 0 to 20, preferably 1 to 20, more preferably an integer of 1 to 10. This is because when n is 1 or more, a diphenylsiloxane unit excellent in flame retardancy is introduced, the flame retardancy is improved as compared with the case where it is not introduced, and when it exceeds 20, the elasticity is lowered. This is because the contribution becomes small.

  The number average molecular weight of the amide group-containing siloxane diamine compound of the formula (1) varies depending on the number of m and n, but is preferably 500 to 3000, more preferably 1000 to 2000.

  Since the amide group-containing siloxane diamine compound of the formula (1) has amide bonds at both ends of the molecule, the amide bonds are also succeeded to the siloxane polyimide resin prepared therefrom. For this reason, the adhesiveness of the polyimide resin derived from an amide group containing siloxane diamine compound with respect to conductor parts, such as copper of a wiring board, improves.

The amide group-containing siloxane diamine compound of the formula (1) can be produced according to the following reaction scheme.

In formulas (1) to (4), R ¹ , R ² , m and n are as already described in formula (1), and X is a halogen atom such as chlorine or bromine.

  In the method for producing the amide group-containing siloxane diamine compound of the formula (1), first, the siloxane diamine compound of the formula (2) and the nitrobenzoyl halide of the formula (3) are subjected to a nucleophilic substitution reaction to obtain an amide of the formula (4). A group-containing dinitro compound is formed. In this case, for example, the dinitro compound of formula (4) is formed by heating and mixing the compound of formula (2) and the compound of formula (3) in a solvent such as toluene in the presence of a base such as triethylamine. (See Organic Chemistry, 5th edition, page 283 (Ed. Stanley H. Pine)).

  Next, the nitro group of the dinitro compound of formula (4) is reduced to an amino group. Thereby, the novel amide group containing siloxane diamine compound of Formula (1) is obtained. The reduction method is not limited as long as the compound of formula (1) is obtained by converting the nitro group to an amino group. For example, in the mixed solvent of ethyl benzoate and ethanol, but in the presence of a palladium carbon catalyst, the formula (4) (See Organic Chemistry, 5th edition, page 642 (Ed. Stanley H. Pine)).

  If the content of the amide group-containing siloxane diamine compound represented by the formula (1) in the diamine component constituting the siloxane polyimide resin that can be used in the present invention is too small, the electroless plating resistance deteriorates, and if it is too large, warping occurs. Since it becomes large, Preferably it is 0.1-20 mol%, More preferably, it is 0.1-15 mol%.

  In addition to the amide group-containing siloxane diamine compound of formula (1), which is an essential component, the diamine component can contain a siloxane diamine compound of formula (2) in order to reduce warpage. If the content of the siloxane diamine compound of the formula (2) is too small, the effect of preventing warpage is not sufficient, and if it is too large, the flame retardancy decreases, so it is preferably 40 to 90 mol%, more preferably 50 to 80%. Mol%. Further, in addition to the diamine compounds of the formulas (1) and (2), the diamine component is 3,3′-diamino-4, in order to achieve alkali solubility as a basis for imparting positive photosensitivity. 4'-dihydroxydiphenyl sulfone can be contained. If the content of 3,3′-diamino-4,4′-dihydroxydiphenylsulfone in the diamine component is too small, the alkali solubility cannot be obtained, and if it is too large, the alkali solubility becomes too high. It is -50 mol%, More preferably, it is 25-45 mol%.

In formula (2), R ¹ , R ² , m, and n are as described in formula (1).

  As a diamine component, in addition to the formula (2) and 3,3′-diamino-4,4′-dihydroxydiphenyl sulfone, it is used as a diamine component of a general polyimide resin as long as the effects of the present invention are not impaired. A diamine compound similar to the above can be used in combination (see Japanese Patent No. 3363600, paragraph 0008).

  The siloxane polyimide resin that can be used in the present invention can be produced by imidizing a diamine component containing the amide group-containing siloxane diamine compound of the above formula (1) and an acid dianhydride component. Here, the molar ratio of the acid dianhydride component to 1 mol of the diamine component is usually 0.8 to 1.2, preferably 0.9 to 1.1. Moreover, in order to seal the molecular terminal of a polyimide resin, if necessary, a dicarboxylic acid anhydride or a monoamine compound can be allowed to coexist during imidization (see Japanese Patent No. 3363600, paragraph 0011).

  As conditions for imidization, any of known imidization conditions can be appropriately employed. In this case, conditions for forming an intermediate such as polyamic acid and then imidizing are also included. For example, it can be carried out under known solution imidization conditions, heat imidization conditions, and chemical imidization conditions (development of new polyimides for next-generation electronics and electronic materials and technology for imparting high functionality, Technical Information Association, 2003, p42).

  The preferable aspect of the siloxane polyimide resin demonstrated above contains the polyimide resin represented by the following structural formula (a) as an essential component. Moreover, it is preferable to further contain the polyimide resin of the following structural formula (b) and structural formula (c).

As the photosensitizer used in the present invention, quinonediazide photosensitizers conventionally used as photosensitizers for positive resist compositions can be preferably used. For example, diazonaphthoquinone (DNQ), 1,2-naphthoquinone. Esters of 2-diazide-5-sulfonic acid or 1,2-naphthoquinone-2-diazide-4-sulfonic acid and low-molecular aromatic hydroxy compounds, such as 2,3,4-trihydroxybenzophenone, 1 , 3,5-trihydroxybenzene, 2,3,4,4′-tetrahydroxybenzophenone, 2- and 4-methylphenol, esters with 4,4′-hydroxypropane, and the like. It is not something. Particularly preferred examples of the quinonediazide photosensitizer include naphthoquinonediazide derivatives. Here, specific examples of the naphthoquinone diazide derivative include naphthoquinone diazide derivatives represented by the following chemical structural formulas (F), (G), and (H). Two or more of these can be used in combination. Among these, the naphthoquinone diazide derivative of the chemical structural formula (G) can be preferably used from the viewpoint of high sensitivity.

  In each of these chemical structural formulas (F), (G), and (H), it is preferable that all of the plurality of substituents R are naphthoquinonediazidosulfonyl groups. On the other hand, not all R are H.

  If the content of the photosensitive agent in the photosensitive polyimide resin composition used in the present invention is too small, development becomes difficult, and if it is too large, film properties tend to decrease. 5-50 mass parts, More preferably, it is 10-30 mass%.

  As the crosslinking agent, those basically used as a crosslinking agent for polyimide resins can be used. For example, epoxy resins, polyisocyanates, benzoxazines, resol resins and the like can be mentioned. Moreover, since there exists a possibility that film | membrane physical property may fall when there are too few compounding quantities of a crosslinking agent and there exists a tendency for image development to become too large, Preferably it is 0.5-20 with respect to 100 mass parts of siloxane polyimide resins. It is 1 part by mass, more preferably 1-10 parts by mass.

  In the case of epoxy resins and polyisocyanates that are widely used as crosslinking agents, it is preferable to avoid using them mainly because they react with bismuthiol and cause the resin composition to gel.

  The photosensitive polyimide resin composition used in the present invention is, as necessary, toluene, γ-butyrolactone, triglyme, diglyme, methyl benzoate, ethyl benzoate, N-methylpyrrolidone, N, N-dimethylacetamide, N, An organic solvent such as N-dimethylformamide can be contained. Among these, γ-butyrolactone and triglyme having good printability can be preferably used. In addition, the usage-amount of an organic solvent becomes like this. Preferably it is 10-1000 mass parts with respect to 100 mass parts of polyimide resin solid content, More preferably, it is 20-500 mass parts.

  The photosensitive polyimide resin composition used in the present invention usually contains a polyimide resin, a photosensitive agent, a crosslinking agent, a bismuth thiol, an organic solvent, and other additives such as a rust inhibitor, as necessary. It can be prepared by mixing uniformly by the method.

<< Step (c) >>
Next, as shown in FIG. 3, the photosensitive resin layer 5 ′ is subjected to a photolithography process so that the conductor pattern 2 in a desired area (preferably the terminal portion 4) is exposed, so that the photosensitive area 5 ′ is exposed. The functional resin layer is removed. Specifically, a resist mask having an opening corresponding to the terminal portion 4 is formed on the photosensitive resin layer 5 ′, exposed, and developed with an alkaline developer such as a 1 to 5 mass% sodium hydroxide aqueous solution. By doing so, the terminal portion 4 of the conductor pattern 2 may be exposed. After alkali development, spray water washing can be performed.

  In addition, when the exposed conductor pattern 2 (terminal part 4) is a copper pattern, its surface changes to red, and the red color change part is observed by transmission microscope observation (TEM) and energy dispersive X-ray fluorescence analysis (EDX). As a result, it can be confirmed that the constituent element is composed of S · Cu. Therefore, it is considered that the red discoloration part is a red film composed of a complex of bismuthiol and copper.

<< Step (d) >>
Next, the exposed conductor pattern 2 is soft-etched with a chemical polishing solution. Here, the soft etching process is a process of removing the reddish portion and the surface oxide on the surface of the exposed conductor pattern 2 (terminal portion 4). Generally, the etch rate for copper at 30 ° C. is 0. It means an etching treatment of 1 to 1.0 μm / min. Examples of the soft etching treatment include immersing the etching target in a chemical polishing liquid and spraying the chemical polishing liquid on the etching target.

  As the chemical polishing liquid, a liquid that can soft-etch the conductor surface can be widely used. A treatment liquid that generates active oxygen, such as an aqueous sodium persulfate solution, may be mentioned. Among these, a hydrogen peroxide-sulfuric acid aqueous solution can be preferably mentioned from the viewpoint of etch rate stability. If the hydrogen peroxide concentration is too low or too high, the etch rate becomes unstable. Therefore, the hydrogen peroxide concentration is preferably 0.1 to 30% by weight, more preferably 0.5 to 5% by weight. Moreover, since the etch rate becomes unstable if the sulfuric acid concentration is too low or too high, it is preferably 0.1 to 30% by mass, more preferably 0.5 to 5% by mass.

  After the soft etching treatment, washing with spray water, washing with dilute sulfuric acid solution, and washing with spray water can be appropriately performed.

<< Step (e) >>
Next, the photosensitive resin layer 5 ′ is crosslinked to crosslink the crosslinking agent, thereby forming the photosensitive resin layer 5 ′ as the coverlay layer 5 (FIG. 4). Thereby, the flexible printed wiring board 10 by which the conductor patterns 2 other than the terminal part 4 were coat | covered with the coverlay layer 5 is obtained.

  Examples of the crosslinking treatment include heat treatment and light irradiation treatment depending on the type of the crosslinking agent to be used, but it is preferable to perform a heat treatment called post-baking at a temperature of 120 to 250 ° C. Further, this heat treatment can be performed in an inert atmosphere (such as a nitrogen atmosphere). In particular, the heat treatment is preferably performed at a temperature not exceeding the decomposition point (156 ° C.) of bismuththiol. Moreover, it is preferable that a bismuth thiol and a crosslinking agent do not react by a crosslinking process.

<< Step (f) >>
If necessary, the exposed terminal portion 4 of the conductor pattern 2 can be covered with a plating film 6 by plating. Thereby, the flexible printed wiring board shown in FIG. 5 is obtained. Examples of the plating treatment include electroless plating and / or electrolytic plating treatment. In consideration of the effect of improving the electroplating resistance of bismuthiol, it is preferable to directly coat with the plating film 6 by electrolytic plating treatment. Examples of the electroless plating include electroless Ni or Au plating, and examples of the electrolytic plating include electrolytic Ni or Au plating.

  The manufacturing method of the flexible printed wiring board of this invention demonstrated above has the side surface of the terminal part formation method of a flexible printed circuit board as shown below. The invention of the terminal portion forming method is also included in the present invention.

  That is, a method for forming a terminal portion of a flexible printed circuit board is a flexible printed wiring having a substrate in which a conductor pattern having a terminal portion is formed on a base material and a coverlay layer formed on the substrate excluding the terminal portion. It is the said terminal part formation method of a board, Comprising: It has the following processes (a ')-(e').

(A ′) a step of obtaining a substrate by forming a conductor pattern having a terminal portion on a substrate;
(B ′) A photosensitive resin layer made of a photosensitive polyimide resin composition containing a polyimide resin, a photosensitive agent, a crosslinking agent, and bismuthiol is formed on the surface of the substrate on which the conductor pattern is formed. The step of:
(C ′) removing the photosensitive resin layer in the corresponding region so that the terminal portion is exposed by subjecting the photosensitive resin layer to a photolithography process;
(D ′) a step of soft-etching the exposed terminal portion with a chemical polishing liquid; and (e ′) a crosslinking treatment of the photosensitive resin layer by crosslinking the photosensitive resin layer, thereby forming the photosensitive resin layer as a coverlay layer. Process.

  These steps (a ′) to (e ′) are respectively as described in the steps (a) to (e) of the method for producing a flexible printed wiring board of the present invention described above.

  Hereinafter, the present invention will be specifically described with reference to examples.

Reference Example 1 (Preparation of siloxane polyimide resin)
(1) Preparation of siloxane diamine To a 2 liter reactor equipped with a cooler, thermometer, dropping funnel and stirrer, 500 g of toluene, siloxane diamine of formula (2) (R1, R2 = trimethylene; trade name X-22 -9409, Shin-Etsu Chemical Co., Ltd.) 200 g (0.148 mmol) and triethylamine 30 g (0.297 mol) were added. Subsequently, a solution in which 54.7 g (0.295 mol) of p-nitrobenzoyl chloride was dissolved in 300 g of toluene was charged into the dropping funnel. The temperature in the reactor was increased to 50 ° C. while stirring, and then the solution in the dropping funnel was added dropwise over 1 hour. After completion of the dropwise addition, the temperature was raised and the mixture was stirred for 6 hours and reacted under reflux. After completion of the reaction, the mixture was cooled to 30 ° C., 800 g of water was added, and the mixture was vigorously stirred, then transferred to a separatory funnel and allowed to stand for liquid separation. Washing with 300 g of 5% aqueous sodium hydroxide was performed 3 times, and washing with 300 g of saturated aqueous sodium chloride was performed twice. The organic layer was dried over magnesium sulfate, the toluene solvent was distilled off by heating under reduced pressure, concentrated and then dried under reduced pressure at 60 ° C. for 1 day. Α- (p-nitrobenzoyliminopropyldimethylsiloxy) -ω- (p-nitrobenzoyliminopropyldimethylsilyl) oligo (dimethylsiloxane-co-diphenylsiloxane) (hereinafter,
Dinitro compound) was obtained in a yield of 235 g (yield 96%). The dinitro product was a pale yellow oil.

  112 g (0.068 mol) of the obtained dinitro compound was placed in a 1 liter reactor equipped with a stirrer, a hydrogen introduction tube and a hydrogen bulb, 180 g of ethyl acetate, 320 g of ethanol, and 20 g of 2% palladium-carbon (water content 50). %). After replacing the inside of the reactor with a hydrogen gas atmosphere, stirring was continued for 2 days at room temperature under hydrogen bulb pressure. After removing the catalyst from the reaction mixture by filtration and concentrating the reaction solution under reduced pressure, drying was performed at 60 ° C. under reduced pressure for 2 days to obtain α- (p-aminobenzoyliminopropyldimethylsiloxy) as a pale yellow oil. 102 g (yield 95%) of -ω- (aminobenzoyliminobromodimethylsilyl) oligo (dimethylsiloxane-co-diphenylsiloxane) (amide group-containing siloxane diamine compound used in the present invention) was obtained. The amine value of the obtained amide group-containing siloxane diamine compound was 69.96 KOHmg / g, and the amino group equivalent was 802 g / mol. The amine value was measured using an automatic potentiometric titrator (AT-500, manufactured by Kyoto Electronics Industry). The amino group equivalent was calculated by 56.106 / (amine value) × 1000.

  Moreover, as a result of measuring an infrared absorption spectrum and 1H-NMR spectrum about the obtained amide group containing siloxane diamine compound, it has confirmed that the target object was obtained. The infrared absorption spectrum was measured by a transmission method using a Fourier transform infrared spectrophotometer (FT-IR420, manufactured by JASCO Corporation). The 1H-NMR spectrum was measured in deuterated chloroform using an NMR spectrophotometer (MERCURY VX-300, Varian Technologies Japan Limited). These results are shown below.

IR spectrum:
3450 cm ⁻¹ (ν _N—H ), 3370 cm ⁻¹ (ν _N—H ), 3340 cm ⁻¹ (ν _N—H ), 3222 cm ⁻¹ (ν _N—H ), 1623 cm ⁻¹ (ν _C═O ), _{^{1260cm -1 (ν CH3), 1000~1100cm}} -1 (ν Si-o)
1H-NMR (CDCl ₃ , δ):
-0.2 to 0.2 (m, methyl), 0.4 to 0.6 (m, 4H, methylene), 1.4 to 1.8 (m, 4H, methylene), 3.2 to 3. 5 (m, 4H, methylene), 3.9 (bs, 4H, amino group hydrogen), 5.8 to 6.3 (m, 2H, amide group hydrogen), 6.4 (m, 4H, amino group adjacent) Aromatic ring hydrogen), 7.1-7.7 (m, aromatic ring hydrogen)

(2) Preparation of siloxane polyimide resin (example in which 1 mol% of amide group-containing siloxane diamine compound of formula (1) is contained in all diamine components)
In a 20 liter reaction vessel equipped with a nitrogen inlet tube, a stirrer, and a Dean-Stark trap, 4460.6 g (3.30 mol) of a siloxane diamine compound (X-22-9409, Shin-Etsu Chemical Co., Ltd.) and 3, 1912.7 g (5.34 mol) of 3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride (DSDA, Shin Nippon Rika Co., Ltd., purity 99.70%), 287 g of γ-butyrolactone, Reference Example 1 A mixed solution with 89.0 g (54.3 mmol, purity 97.10%) of the amide group-containing siloxane diamine compound obtained in 1 above and 2870 g of triglyme were added, and the mixed solution was stirred. Further, 1100 g of toluene was added, and then the mixture was heated to reflux at 185 ° C. for 2 hours, followed by dehydration under reduced pressure and toluene removal to obtain an acid anhydride-terminated oligoimide solution.

  The resulting acid anhydride-terminated oligoimide solution was cooled to 80 ° C., and 3431 g of triglyme, 413 g of γ-butyrolactone, 3,3′-diamino-4,4′-dihydroxydiphenyl sulfone (BSDA, Konishi Chemical Industries, Ltd., purity) 99.70%) and a dispersion consisting of 537.80 g (1.92 mol) were added and stirred at 80 ° C. for 2 hours. 524 g of triglyme was added thereto for adjusting the amount of solvent, and the mixture was heated to reflux at 185 ° C. for 2 hours. After cooling the obtained reaction mixture to room temperature, toluene and water accumulated in the trap were removed. Through the above operation, a siloxane polyimide resin having an amide group was synthesized. The measured solid content of the obtained siloxane polyimide resin was 47.5%. Moreover, the polystyrene conversion molecular weight by GPC (gel permeation chromatography) was 63000 as a weight average molecular weight.

  The obtained siloxane polyimide resin was diluted with a mixed solvent of triglyme and γ-butyrolactone (mass ratio 9: 1) so that the resin content was 45% by mass to obtain a siloxane polyimide varnish.

Reference example 2
To 100 parts by mass of the polyimide resin contained in the siloxane polyimide varnish of Reference Example 1, 10 parts by mass of naphthoquinone diazide (4-NT-300, Toyo Gosei Kogyo Co., Ltd.), rust inhibitor (CDA-10, ( ADEKA) 0.3 parts by mass, benzoxazine crosslinking agent (BF-BXZ, Konishi Chemical Co., Ltd.) 5 parts by mass, and resole resin crosslinking agent (BRL274, Showa Polymer Co., Ltd.) 2 parts by mass were mixed. A photosensitive siloxane polyimide resin composition containing no bismuthiol was prepared.

Reference example 3
In 100 parts by mass of the polyimide resin contained in the siloxane polyimide varnish of Reference Example 1, 0.5 parts by mass of bismuthiol, 10 parts by mass of naphthoquinonediazide (4-NT-300, Toyo Gosei Co., Ltd.), rust prevention Agent (CDA-10, ADEKA Co., Ltd.) 0.3 parts by mass, benzoxazine crosslinking agent (BF-BXZ, Konishi Chemical Co., Ltd.) 5 parts by mass, and resole resin crosslinking agent (BRL274, Showa Polymer Co., Ltd.) ) 2 parts by mass were mixed to prepare a photosensitive siloxane polyimide resin composition containing bismuthiol.

Examples 1 to 3, Comparative Examples 1 to 6, Control Example 1
For Examples 1 to 3 and Comparative Examples 2 to 6, the photosensitive siloxane polyimide resin composition containing the bismuthiol of Reference Example 3 was used. For Control Example 1, the photosensitive siloxane polyimide resin composition containing no Bismuthiol of Reference Example 2 was used. Was coated on a copper foil surface of a polyimide film-based copper-clad laminate (Espanex, Nippon Steel Chemical Co., Ltd.) to a dry thickness of 10 μm to form a photosensitive resin layer. As shown in Table 1, the photosensitive resin layer was subjected to necessary treatments in the following series of treatments, an opening reaching the copper foil was formed and baked to obtain a flexible printed wiring board test piece.

a) Exposure: Exposure was performed with an integrated light amount shown in Table 1 at a light amount of 100 mW / cm ² from a high-pressure mercury lamp so that an opening of 0.3 mm square was formed.
b) 3% NaOH immersion: Development was performed by a dipping method using a 3% aqueous sodium hydroxide solution at 40 ° C.
c) Spray water washing: Spray water washing was performed with ion exchange water at room temperature (usually 10 to 35 ° C.).
d) 10% chemical solution immersion: chemical polishing liquid (aqueous solution containing 1% by weight of hydrogen peroxide and 1.5% by weight of sulfuric acid (10% chemical polishing liquid manufactured by Mitsubishi Gas Chemical Co., Ltd.)) Soaked at 30 ° C.
e) Spray water washing: Spray water washing was performed again with ion exchange water at room temperature.
f) 10% sulfuric acid immersion; dipping in a 10% aqueous sulfuric acid solution at room temperature.
g) 200 ° C. inert bake: heat-treated at 200 ° C. in a nitrogen atmosphere.
h) Pre-plating chemical solution immersion: chemical polishing solution (aqueous solution containing 1% by weight of hydrogen peroxide and 1.5% by weight of sulfuric acid (10% chemical polishing solution manufactured by Mitsubishi Gas Chemical Co., Ltd.)) Soaked at 30 ° C.
i) Spray water washing: Spray water washing was performed again with ion exchange water at room temperature.

<< Evaluation >>
(1) Presence or absence of red film g) After 200 ° C. inert bake, whether or not a red film was formed on the exposed copper surface of the opening was visually observed. Regarding the observed color, the degree of red spread on the copper surface in the case of Control Example 1 using the photosensitive polyimide resin composition not containing bismuthiol is set to 0 (that is, when no red film is present), and bismuthiol is contained. Using the photosensitive polyimide resin composition and 10% chemical polishing solution immersion was not performed, the degree of red spread on the copper surface in Comparative Example 1 was set to 10, and was evaluated in 11 stages. The obtained results are shown in Table 1. The evaluation is most preferably “0”, but if it is 3 or less, it is a practically acceptable level.

(2) Surface damage of coverlay layer The surface damage of the coverlay layer under development conditions, 10% chemical solution immersion conditions, and 10% sulfuric acid immersion conditions was visually observed. When damage occurs, the surface becomes a crater-like surface and appears white. Therefore, the observed color was evaluated in six stages, with the degree of whiteness in Comparative Example 6 set to 5 and the case of Control Example 1 set to 0. The obtained results are shown in Table 1. The evaluation is most preferably “0”, but if it is 2 or less, it is a practically acceptable level.

  As can be seen from Table 1, after exposure / development and before post-baking (200 ° C. inert baking), 10% chemical solution immersion was performed, and the red film on the exposed copper surface could be removed. Note that if the 10% chemical solution immersion time becomes longer, the risk of damage to the coverlay layer surface increases, so attention must be paid. Moreover, it turns out that the processing time of about 30 seconds is preferable.

  In addition, in the case of the control example 1 which does not use bismuthiol, a red film is not generated and the surface damage of the coverlay layer is not observed, but in the case of comparative examples 1 to 4 in which 10% chemical solution immersion is not performed, A film was generated. Moreover, when attention is paid to Comparative Example 2, it can be seen that the red film cannot be removed even if the alkali development time is 1.5 times that of Comparative Example 1. Further, when attention is paid to Comparative Example 3, it can be seen that the red film cannot be removed even if the exposure integrated light amount and the spray water washing time of Comparative Example 1 are each doubled. Focusing on Comparative Example 4, it can be seen that the red film cannot be removed even if the 10% sulfuric acid immersion time is 6 times that of Comparative Example 1.

  Further, when attention is paid to Comparative Examples 5 and 6, it can be seen that when the 10% chemical solution immersion treatment is performed after post-baking and before plating, the red film cannot be removed.

<Analysis of red film>
Results of TEM (transmission electron microscope) observation and EDX (energy dispersive X-ray fluorescence) analysis>
The exposed copper surface of the flexible printed wiring board prepared in each of Control Example 1 and Comparative Example 1 was subjected to TEM (transmission electron microscope) observation and EDX (energy dispersive fluorescent X-ray) analysis.

  First, an observation test piece was prepared by applying a normal TEM observation test piece preparation method using platinum to a flexible printed wiring board. When the test piece was observed with a TEM, in the case of Comparative Example 1, a very thin layer having a maximum thickness of about 7.5 nm different from copper was observed on the copper surface. This is considered to be a red film. In contrast, in the case of Control Example 1, such a thin layer was not observed.

  When this thin layer was subjected to EDX mapping using an energy dispersive X-ray fluorescence spectrometer (EM-002B, TOPCON Co., Ltd.), it was found that the elemental configuration was not “Si” but “S · Cu”. . Here, the Si source is considered to be derived from the main chain of the siloxane polyimide resin, S is considered to be derived from the main chain of the siloxane polyimide resin and bismuthiol, and Cu is derived from the copper pattern. It is thought to be a thing. Since the abundance of Si and S in the main chain of the siloxane polyimide resin is Si> S, S in “S · Cu” can be reasonably inferred to be derived from bismuthiol, while the main chain of the siloxane polyimide resin. It turns out that it is not derived from.

<Confirmation test of electroplating resistance by adding Bismuthiol>
For reference, the results of a confirmation test of electrolytic plating resistance by adding bismuthiol will be briefly described below.

A gold cyanide plating solution (Tempe Resist FX, Japan High-Purity Chemical Co., Ltd.) was used on the exposed copper surface of the flexible printed wiring board test piece prepared in each of Comparative Example 1 and Comparative Example 1, and current density 1 A gold film having a thickness of 0.3 μm at 0.0 A / dm ² was directly formed by electrolytic plating. It was visually observed whether or not plating insertion occurred at the boundary between the copper and the coverlay layer. As a result, in the case of Control Example 1, insertion occurred and discoloration occurred in the coverlay layer around the opening.

  In the case of Comparative Example 1, no insertion occurred, and no discoloration occurred in the coverlay layer around the opening. However, uneven plating was observed in the electrolytic gold plating film on the exposed copper surface.

  Therefore, it was found that it is preferable to add bismuthiol to improve the electroplating resistance of the photosensitive polyimide resin composition.

  In the manufacturing method of the flexible printed wiring board or the terminal portion forming method of the present invention, after the opening is provided in the photosensitive resin layer by the photolithography process of the photosensitive resin layer, the post-baking process in which the photosensitive resin layer is crosslinked and cured. In the meantime, following the photolithography process, a soft etching process is performed with a chemical polishing liquid. For this reason, discoloration of the surface of the exposed conductor pattern can be removed. As a result, plating unevenness can be prevented, which is suitable for manufacturing a flexible printed wiring board.

DESCRIPTION OF SYMBOLS 1 Base material 2 Conductive pattern 3 Board | substrate 4 Terminal part 5 Coverlay layer 5 'Photosensitive resin layer 6 Plating film 10 Flexible printed wiring board

Claims (8)

In a method for producing a flexible printed wiring board having a substrate having a conductor pattern formed on a substrate and a coverlay layer formed on the substrate, the following steps (a) to (e):
(A) obtaining a substrate by forming a conductor pattern on a substrate;
(B) A photosensitive resin layer made of a photosensitive polyimide resin composition containing a polyimide resin, a photosensitive agent, a crosslinking agent, and bismuthiol is formed on the surface of the substrate on which the conductor pattern is formed. Process;
(C) removing the photosensitive resin layer in the corresponding region so that the conductive pattern in the desired region is exposed by performing a photolithography process on the photosensitive resin layer;
(D) a step of soft-etching the exposed conductor pattern with a chemical polishing solution; and (e) crosslinking the photosensitive resin layer to crosslink the crosslinking agent, thereby forming the photosensitive resin layer as a coverlay layer. Process;
The manufacturing method characterized by having.   The manufacturing method according to claim 1, wherein the chemical polishing liquid used in the soft etching treatment in the step (d) is a hydrogen peroxide-sulfuric acid aqueous solution.   The method according to claim 1 or 2, wherein the hydrogen peroxide concentration in the hydrogen peroxide-sulfuric acid aqueous solution is 0.1 to 30 wt%, and the sulfuric acid concentration is 0.1 to 30 wt%.   The method according to claim 1 or 2, wherein the hydrogen peroxide concentration in the hydrogen peroxide-sulfuric acid aqueous solution is 0.5 to 5 wt%, and the sulfuric acid concentration is 0.5 to 5 wt%.   The manufacturing method according to claim 1, wherein the conductor pattern is a copper pattern.   The production method according to any one of claims 1 to 5, wherein the content of bismuththiol in the photosensitive polyimide resin composition is 0.01 to 10 parts by mass with respect to 100 parts by mass of the siloxane polyimide resin. Further, the following step (f)
(F) The manufacturing method in any one of Claims 1-6 which has the process of coat | covering the exposed conductor pattern with a plating film by a plating process. A method for forming a terminal part of a flexible printed wiring board having a substrate on which a conductor pattern having a terminal part is formed on a substrate and a coverlay layer formed on the substrate excluding the terminal part, and Steps (a) to (e) of:
(A ′) a step of obtaining a substrate by forming a conductor pattern having a terminal portion on a substrate;
(B ') A photosensitive resin layer made of a photosensitive polyimide resin composition containing a polyimide resin, a photosensitive agent, a crosslinking agent, and bismuth thiol is formed on the surface of the substrate on which the conductor pattern is formed. The step of:
(C ′) removing the photosensitive resin layer in the corresponding region so that the terminal portion is exposed by subjecting the photosensitive resin layer to a photolithography process;
(D ′) a step of performing a soft etching treatment on the exposed terminal portion with a chemical polishing liquid; and (e ′) a crosslinking treatment of the photosensitive resin layer by crosslinking the photosensitive resin layer, thereby forming the photosensitive resin layer as a coverlay layer. The step of:
The terminal part formation method characterized by having.

Images