JP5505215B2 - Photosensitive polyimide resin composition, flexible printed wiring board and method for producing the same - Google Patents

Description

  The present invention relates to a photosensitive polyimide resin composition having excellent adhesion and plating resistance and capable of providing a coverlay layer useful for a flexible printed wiring board.

  When manufacturing a flexible printed wiring board, a photosensitive polyimide resin composition comprising a polyimide resin mixed with a naphthoquinone diazide-based photosensitive agent and an epoxy-based crosslinking agent is applied to the side of the polyimide-based copper pattern on which the copper pattern is formed. Then, the obtained photosensitive resin composition film is subjected to exposure / development treatment so that the terminal portion of the copper pattern is opened, and further subjected to heat crosslinking treatment, thereby forming a coverlay 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 adhesion evaluation by a cross-cut test especially for a copper pattern is sufficient. Even in such a case, when the area of the cover lay layer corresponding to the terminal portion of the copper pattern is opened by photolithography technology, and metal is deposited directly on the exposed copper pattern by electrolytic plating, the copper is formed from the bottom corner of the opening portion. There is a problem that the plating solution is inserted into the boundary between the pattern and the coverlay layer, and metal plating is deposited on an unintended portion.

  The present invention is intended to solve the above-described problems of the prior art, and by applying a coverlay layer excellent in adhesion and electrolytic direct plating resistance from a photosensitive polyimide resin composition using a siloxane polyimide resin. It aims to be able to form.

  Under the assumption that the object of the present invention can be achieved by blending various heterocyclic thiol compounds with a photosensitive polyimide 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 resistance to electrolytic direct plating but also adhesion before plating. Bismuthiol (2,5-dimercapto-1,3,4-thiadiazole) is The inventors have found that the above object can be achieved and have completed the present invention.

  That is, the present invention provides a photosensitive polyimide resin composition containing a siloxane polyimide resin, a photosensitive agent, and a crosslinking agent, wherein the photosensitive polyimide resin composition contains bismuth thiol.

  The present invention also relates to a flexible printed wiring comprising a substrate on which a conductor pattern having a terminal portion coated with a plating film is formed on a base material, and a coverlay layer formed on the substrate excluding the terminal portion. Provided is a flexible printed wiring board, wherein the coverlay layer is obtained by crosslinking the layer of the above-described photosensitive polyimide resin composition of the present invention.

Furthermore, the present invention relates to a flexible printed wiring comprising a substrate on which a conductor pattern having a terminal portion coated with a plating film is formed on a base material, and a coverlay layer formed on the substrate excluding the terminal portion. In the method for producing a plate, 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) forming a photosensitive resin layer comprising the above-described photosensitive polyimide resin composition of the present invention on the surface of the substrate on which the conductor pattern is formed;
(C) a step of exposing the terminal portion by subjecting the photosensitive resin layer to a photolithography process;
(D) cross-linking the photosensitive resin layer to cross-link the cross-linking agent, thereby forming the photosensitive resin layer as a coverlay layer; and (e) covering the exposed terminal portion with a plating film. A manufacturing method is provided.

  The photosensitive siloxane polyimide composition of the present invention contains bismuth thiol. For this reason, when a coverlay layer is formed by coating on a flexible printed wiring board comprising a polyimide base and a conductor pattern formed thereon, good adhesion to the polyimide base and the conductor pattern with respect to the coverlay layer In addition, even if the area of the cover lay layer corresponding to the terminal portion of the conductor pattern is opened by photolithography, and metal is deposited directly on the exposed conductor pattern by electrolytic plating, the inner bottom corner of the opening portion can be obtained. Therefore, it is possible to prevent the plating solution from being inserted into the boundary between the conductor pattern and the cover lay layer, and to prevent the metal plating from being deposited on unintended portions.

FIG. 1 is a cross-sectional view of the 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 photosensitive polyimide resin composition of the present invention contains a siloxane polyimide resin, a photosensitive agent, and a crosslinking agent, and further contains bismuth thiol. For this reason, good adhesion and electrolytic direct plating resistance can be imparted to the coverlay layer formed by applying this photosensitive polyimide resin composition.

  If the content of the bismuthiol in the photosensitive polyimide resin composition is too small, the resistance to electrolytic direct plating becomes insufficient. If the content is too large, blackening of the copper pattern due to the formation of copper sulfide occurs when the conductor pattern is a copper pattern. Since there is concern, it is preferably 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the siloxane polyimide resin.

  The siloxane polyimide resin constituting the photosensitive polyimide resin composition of the present invention uses various siloxane diamines as the diamine component constituting the polyimide. For example, the siloxane polyimide described in Patent Documents 1 to 3 above. Resins 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 conductor patterns, such as a copper pattern.

  Such a siloxane polyimide resin includes a diamine component containing an amide group-containing siloxane diamine compound represented by the following formula (1), pyromellitic tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetra Carboxylic dianhydride, 3,3 ′, 4,4′-diphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic 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) fluoric acid dianhydride, 9,9-bis [4- (3,4-dicarboxyphenoxy) phenyl] fluoric acid dianhydride And an acid dianhydride component containing at least one aromatic acid dianhydride selected from the group consisting of 1,2,3,4-cyclobutanoic acid dianhydride.

  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, and a pentamethylene group. And 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. R ¹ and R ² may be the same or different from each other, but if they are different, it is difficult to obtain raw materials, and it is desirable 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 diamine group of the formula (4) and the nitrobenzoyl halide of the formula (3) are subjected to a nucleophilic substitution reaction to obtain an amide group of the formula (4). A 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 used in the present invention is too small, the electroless plating resistance is deteriorated, 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, alkali solubility cannot be obtained, and if it is too large, 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 one described above (see Japanese Patent No. 3363600, paragraph 0008) can be used in combination.

  Examples of the acid dianhydride component constituting the siloxane polyimide resin include pyromellitic tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4 ′. -Diphenyl ether tetracarboxylic dianhydride, 3,3 ', 4,4' diphenylsulfone tetracarboxylic 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] fluorenoic dianhydride, and 1,2,3,4-cyclobutanoic dianhydride Mention may be made of acid dianhydride components comprising at least one aromatic dianhydride selected. 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.

  The siloxane polyimide resin used in the present invention can be produced by imidizing a diamine component containing the amide group-containing siloxane diamine compound of formula (1) described above 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, ester compounds with 4,4′-hydroxypropane, and the like. Is not to be done. 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 of the present invention is too small, pattern formation may be difficult, and if it is too large, film properties may be reduced. On the other hand, it is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by 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 possibility that photosensitivity may fall when there is too much, Preferably it is 0.1-30 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.

  If necessary, the photosensitive polyimide resin composition of the present invention may be toluene, γ-butyrolactone, triglyme, diglyme, methyl benzoate, ethyl benzoate, N-methylpyrrolidone, N, N-dimethylacetamide, N, N- An organic solvent such as 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 is normally 10-1000 mass parts with respect to 100 mass parts of siloxane polyimide resins, More preferably, it is 20-500 mass parts.

  The photosensitive polyimide resin composition of the present invention comprises a siloxane polyimide resin, a photosensitizer, a crosslinking agent, a bismuthiol, an organic solvent, and other additives such as a rust preventive agent as required. Can be prepared by mixing more uniformly.

  The photosensitive polyimide resin composition of the present invention described above can be preferably applied to a coverlay layer of a flexible printed wiring board described below (see FIG. 1).

  The flexible printed wiring board 10 is formed on a substrate 5 on which a conductor pattern 4 having a terminal portion 3 covered with a plating film 2 is formed on a base material 1 and a substrate 5 excluding the terminal portion 3. And a coverlay layer 6. This coverlay layer 6 is obtained by crosslinking a coating layer of the photosensitive polyimide resin composition of the present invention.

  As the base material 1 constituting the substrate 5, a resin film that has been 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 12.5 to 25 μm.

  The conductive pattern 4 constituting the substrate 5 is formed by forming a 9 to 35 μm thick copper foil or the like laminated on the base material 1 by a known patterning technique such as a photolithographic technique.

  As the plating film 2, an electroless plating film (for example, an electroless nickel plating film or an electroless gold plating film) formed by performing electroless plating on the terminal portion 3 of the conductor pattern 4, such an electroless plating film is used. Further, a laminated plating film in which an electrolytic plating film is laminated (for example, an electrolytic gold plating film laminated on an electroless plating film), and an electrolytic direct plating film formed by directly performing electrolytic plating on the terminal portion 3 of the conductor pattern 4 (For example, electrolytic direct gold plating film). Among these, an electrolytic direct plating film can be preferably applied from the viewpoint of the effect of the present invention that is resistance to electrolytic direct plating. In addition, the terminal part 3 means the area | region designated as a terminal in the conductor pattern 4 according to the intended purpose etc. of the flexible printed wiring board 10. FIG.

  The coverlay layer 6 is obtained by crosslinking the already described coating layer of the photosensitive polyimide resin composition of the present invention by the action of a crosslinking agent contained in the resin composition. Formation of a coating layer can be performed using a well-known coating technique. Further, the crosslinking can be performed by heat treatment, light irradiation, or the like depending on the type of the crosslinking agent.

  Such a flexible printed wiring board can be manufactured by performing the following steps (a) to (e). It demonstrates for every process.

Step (a)
A conductor pattern 4 having terminal portions 3 is formed on a base material 1 according to a conventional method to obtain a substrate 5 (FIG. 2). In this case, it is preferable to use the copper clad laminated board by which the copper foil was laminated | stacked on the polyimide film base material as an original fabric.

Step (b)
The photosensitive polyimide resin composition of the present invention is applied to the surface of the substrate 5 on the side where the conductor pattern 4 is formed by a known coating method to form a photosensitive resin layer 6 '(FIG. 3).

Step (c)
The terminal part 3 is exposed by performing a photolithography process with respect to the obtained photosensitive resin layer 6 '(FIG. 4). Specifically, a resist mask having an opening corresponding to the terminal portion 3 is formed on the photosensitive resin layer 6 ′, exposed, and developed with an alkaline solution to expose the terminal portion 3 of the conductor pattern 4. Let

Step (d)
Next, the photosensitive resin layer 6 ′ is subjected to a crosslinking treatment to crosslink the crosslinking agent, whereby the photosensitive resin layer is used as the coverlay layer 6 (FIG. 5). Examples of the cross-linking treatment include heat treatment and light irradiation treatment depending on the type of the cross-linking agent, and it is preferable to perform heat treatment at a temperature not exceeding the decomposition point of bismuththiol (156 ° C.).

Step (e)
Next, the exposed terminal portion is covered with the plating film 2 by electroless plating and / or electrolytic plating. Preferably, the plating film 2 is coated by electrolytic direct plating. Thereby, the flexible printed wiring board shown in FIG. 1 is obtained.

  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) (R ¹ , R ² = 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. 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 under reduced pressure, concentrated, and dried under reduced pressure at 60 ° C. for 1 day. The obtained α- (p-nitrobenzoyliminopropyldimethylsiloxy) -ω (p-nitrobenzoyliminopropyldimethylsilyl) oligo (dimethylsiloxane-co-diphenylsiloxane) (hereinafter, dinitro form) 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. The catalyst was removed by filtration from the reaction mixture, and the reaction mixture was concentrated under reduced pressure and then dried at 60 ° C. under reduced pressure for 2 days. Α- (p-aminobenzoyliminopropyldimethylsiloxy) was obtained as a pale yellow oil. A yield of 102 g (yield: 95%) of -ω- (aminobenzoyliminopropyldimethylsilyl) 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 Co., Ltd.). 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 ), 1260 cm ⁻¹ (νCH ₃ ), 1000 to 1100 cm ⁻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 obtained 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 solid content was 50% by mass to obtain a siloxane polyimide varnish.

Examples 1-3, Comparative Examples 1-5
To the siloxane polyimide varnish of Reference Example 1, an aromatic thiol compound, naphthoquinonediazide (4-NT-300, Toyo Gosei Kogyo Co., Ltd.), rust preventive (CDA-10, ADEKA Co., Ltd.) according to the recipe in Table ), A benzoxazine crosslinking agent (BF-BXZ, Konishi Chemical Co., Ltd.) and a resol resin crosslinking agent (BRL274, Showa High Polymer Co., Ltd.) were mixed to prepare a photosensitive siloxane polyimide resin composition.

The obtained photosensitive siloxane polyimide resin composition is applied to a copper foil surface of a polyimide film-based copper-clad laminate (Espanex, Nippon Steel Chemical Co., Ltd.) so as to have a dry thickness of 10 μm. A composition layer was formed. With respect to this photosensitive resin composition layer, an integrated light amount of 1500 mJ / cm at a light amount of 100 mW / cm ² from a high-pressure mercury lamp so that an opening (0.3 mm square) reaching the copper foil is formed by photolithography technology. ² and developing by a dipping method using an aqueous sodium hydroxide solution at 40 ° C., and further post-baking at 200 ° C. for 60 minutes to crosslink the photosensitive resin composition layer to coverlay layer A sample before electrolytic plating having the structure of FIG. 5 was obtained.

<Adhesion evaluation>
The coverlay layer of the sample before electrolytic plating is cut on a grid of 10 squares × 10 squares at 1 mm intervals. When an 18 mm wide adhesive tape (Nichiban Co., Ltd.) is applied and peeled off so as to cover this grid, the number of remaining squares out of all 100 squares is 80 or more. ", The case of less than 80 was determined as" NG ". The obtained results are shown in Table 1.

<Electrolytic plating resistance>
(A) A gold cyanide plating solution (Tempe Resist FX, Nippon High Purity Chemical Co., Ltd.) is used for the exposed copper foil of the sample before electrolytic plating, and 0 at a current density of 0.2 to 0.4 A / dm ² . An electrolytic direct gold plating film having a thickness of 3 μm was formed. It was visually observed whether or not plating insertion occurred at the boundary between the copper foil and the coverlay layer. The case where it did not occur was evaluated as “G”, and the case where it occurred was evaluated as “NG”. The obtained results are shown in Table 1.

(B) When an 18 mm wide adhesive tape (Nichiban Co., Ltd.) was applied to the cover lay layer at the periphery of the opening and peeled off, it was visually observed whether or not the cover lay layer was peeled off. The case where it did not occur was evaluated as “G”, and the case where it occurred was evaluated as “NG”. The obtained results are shown in Table 1.

  As can be seen from Table 1, in the case of the photosensitive siloxane polyimide resin compositions of Examples 1 to 3, in which bismuthiol was contained at a ratio of 0.25 to 1.0 part by mass with respect to 100 parts by mass of the siloxane polyimide resin, Excellent adhesion before direct plating, and excellent resistance to electrolytic direct plating.

  On the other hand, in the case of Comparative Example 1 in which an aromatic thiol compound such as bismuthiol was not blended, the adhesion before electrolytic direct plating was good, but there was a problem in electrolytic direct plating resistance. In Comparative Example 2 in which monomethylbismuthiol similar to bismuthiol was blended, the adhesion before electrolytic direct plating was good, but there was a problem with electrolytic direct plating resistance.

  Moreover, in the case of Comparative Examples 3-5 which mix | blended the other aromatic thiol compound different from bismuthiol, there existed a problem not only in the electrolytic direct plating tolerance but in the adhesiveness before electrolytic direct plating.

  The photosensitive siloxane polyimide resin composition of the present invention contains bismuth thiol. For this reason, the cover lay layer is given good adhesion to the polyimide base and the conductor pattern, and the area of the cover lay layer corresponding to the terminal portion of the conductor pattern is opened and exposed by photolithography technology. Even if the metal is deposited directly on the conductor pattern by electrolytic plating, the plating solution is prevented from being inserted from the inner bottom corner of the opening to the boundary between the conductor pattern and the coverlay layer, and the metal plating is deposited on an unintended portion. This can be prevented. Therefore, the photosensitive siloxane polyimide resin composition of the present invention is useful for flexible printed wiring boards.

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

Claims (7)

  A photosensitive polyimide resin composition comprising a siloxane polyimide resin, a photosensitive agent, and a crosslinking agent, wherein the photosensitive polyimide resin composition contains bismuth thiol.   The photosensitive polyimide resin composition of Claim 1 which contains 0.1-10 mass parts of bismuthiol with respect to 100 mass parts of siloxane polyimide resins. A siloxane polyimide resin is a diamine component containing an amide group-containing siloxane diamine compound represented by the formula (1), pyromellitic tetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride 3,3 ′, 4,4′-diphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic 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) fluoric dianhydride, 9,9-bis [4- (3,4-dicarboxyphenoxy) phenyl] fluoric dianhydride, and 1,2 The acid dianhydride component containing at least one aromatic acid dianhydride selected from the group consisting of 1,3,4-cyclobutanoic acid dianhydride is formed by imidization. Photosensitive polyimide resin composition.

(In formula (1), R ¹ and R ² are each an alkylene group that may be independently substituted, m is an integer of 1-30, and n is an integer of 0-20.) The photosensitive polyimide resin composition according to claim 1, wherein the photosensitive agent is at least one of naphthoquinonediazide derivatives represented by the following chemical structural formula.

  The photosensitive polyimide resin composition according to claim 1, wherein the crosslinking agent is a benzoxazine or a resole.   A flexible printed wiring board having a substrate on which a conductor pattern having a terminal portion coated with a plating film is formed on a substrate, and a coverlay layer formed on the substrate excluding the terminal portion, A flexible printed wiring board, wherein the cover lay layer is obtained by crosslinking a layer of the photosensitive polyimide resin composition according to any one of claims 1 to 5. In a method of manufacturing a flexible printed wiring board having a substrate formed with a conductor pattern having a terminal portion coated with a plating film on a substrate, and a coverlay layer formed on the substrate excluding the terminal portion, 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) The process of forming the photosensitive resin layer which consists of the photosensitive polyimide resin composition in any one of Claims 1-5 on the surface by which the conductor pattern was formed of the board | substrate;
(C) a step of exposing the terminal portion by subjecting the photosensitive resin layer to a photolithography process;
(D) cross-linking the photosensitive resin layer to cross-link the cross-linking agent, thereby forming the photosensitive resin layer as a coverlay layer; and (e) covering the exposed terminal portion with a plating film. The manufacturing method characterized by this.

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