JPH0370396B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a printed wiring board by an additive method. (Prior Art) Conventionally, when manufacturing a printed wiring board by forming a circuit by electroless plating such as the CC-4 method, an adhesive layer containing a catalyst is provided in advance on the surface of an insulating substrate. In this case, if the insulating substrate has holes for through holes, after the holes are formed and before electroless plating, a plating catalyst is applied to the holes. ing. (Problem to be Solved by the Invention) By the way, usually after the plating catalyst is attached to the holes, an adhesive layer is applied to improve the adhesion between the adhesive layer and the plating circuit formed by electroless plating. The agent layer is roughened. The adhesive layer is roughened by dipping the insulating substrate in a roughening solution such as a borofluoric acid solution or an anhydrous chromic acid/sulfuric acid solution. Most of the catalyst will be washed away. Therefore, even if electroless plating is performed later, it takes time for the plating to precipitate at the hole locations, and the deposited plating film is thin and has low peel strength. Therefore, when soldering a land using a solder dip or connecting an electronic component, the gas inside the insulating substrate is released through the plating film on the hole wall, and the solder filled in the hole has defects (hereinafter referred to as "defects"). It had the disadvantage of causing blowholes (called blowholes). In such a state, there are disadvantages in that connection failures of electronic components are likely to occur and adhesive strength is also likely to decrease. (Objective) The present invention improves the above-mentioned drawbacks, facilitates plating deposition on the hole wall surface for through-holes, shortens manufacturing time, prevents blowholes, and manufactures highly reliable printed wiring boards. The purpose is to provide a method. (Means for Solving the Problems) In order to achieve the above object, the present invention roughens an insulating substrate having holes for through holes and coated with a plating catalyst-containing adhesive. In a method for manufacturing a printed wiring board, the method comprises roughening the adhesive and forming a predetermined circuit by electroless plating,
forming a semi-cured thermosetting resin layer containing the plating catalyst on the hole wall surface by repeating the process of immersing the insulating substrate in a thermosetting resin solution containing the plating catalyst and drying it two or more times; , provides a method for producing a printed wiring board, which comprises performing a step of attaching a plating catalyst to the thermosetting resin layer after the step, and a step of thermosetting the thermosetting resin layer after the step. It is something to do. (Function) That is, according to the present invention, a semi-cured thermosetting resin layer containing a plating catalyst is provided in advance on the wall surface of a through hole provided in an insulating substrate, and this resin layer is further coated with a plating catalyst. Since a plating catalyst is attached, a sufficient thickness of plating is deposited within the hole in a short time by electroless plating to form a plating layer. Moreover, since the thermosetting resin layer can prevent the gas in the insulating substrate from being released through the hole walls,
Defects such as blowholes caused by soldering are prevented. In addition, because the process of dipping the insulating substrate into a thermosetting resin solution containing a plating catalyst and drying it is repeated two or more times, the thermosetting process is smoother and more accurate on the hole wall surface than when the process is performed only once. A resin layer can be formed. (Example) Hereinafter, an example of the present invention will be described based on the drawings. First, as shown in FIG. 1, an insulating substrate 1 made of a paper-phenol resin base material or a paper-epoxy resin base material is prepared.
An adhesive containing a plating catalyst such as palladium is applied to the adhesive layer 2 to form an adhesive layer 2. Next, as shown in FIG. 2, predetermined holes 3 are formed by punching the insulating substrate 1 on which the adhesive layer 2 is formed. After forming the holes 3, the surface of the insulating substrate 1 is leveled and washed with high-pressure water to remove substrate debris caused by punching. Next, the insulating substrate 1 of the water washer is immersed in an emulsion of a thermosetting resin such as an epoxy resin containing a plating catalyst of palladium chloride and tin chloride. After the insulating substrate 1 is immersed in the emulsion, it is taken out and the emulsion on the surface is removed using a squeezing roller or a buff. After removing the emulsion, the thermosetting resin adhered to the hole wall is heated by hot air that causes natural convection of heated air or hot air that circulates forcibly heated air using an electric fan, etc. Dry to a semi-hardened state. After heating and drying the thermosetting resin,
The process of dipping the insulating substrate 1 into the emulsion again, taking it out, and heating and drying it is repeated. Through this process, as shown in FIG.
A semi-cured thermosetting resin layer 4 of about 30 μm is formed. As the thermosetting resin, in addition to epoxy resin, urethane resin, polyester resin, etc. are used, but especially in the case of a phenol resin-based or epoxy resin-based insulating substrate, epoxy resin is preferable because it has good adhesion to the substrate. In addition, as a hardening agent,
Amine-based emulsions are preferred because they yield stable emulsions, and solids concentration in the emulsion is particularly preferably in the range of 0.3 to 10 wt%.
That is, if the concentration is less than 0.3 wt%, the effect as a film will be low, and if it is more than 10 wt%, the resin may be coated so as to close the pores, making removal work necessary, which is not favorable for work. The resin solution may be a normal solvent solution, but an emulsion or an aqueous solution is easier to work with since it does not cause skin formation due to resin when drying. The amount of plating catalyst added in the emulsion is based on 100 parts by weight of resin.
The range of 0.005 to 0.5 parts by weight is good; if it is less than 0.005 parts by weight, the effect is low, and if it is more than 0.5 parts by weight, it becomes expensive and the catalytic effect becomes saturated. After forming a semi-cured thermosetting resin layer 4 on the hole wall surface, the insulating substrate is immersed in a plating catalyst solution to adhere a plating catalyst 5 as shown in FIG. The resin layer 4 is heated and hardened. After curing the thermosetting resin layer 4, as shown in FIG. 5, a plating resist ink is applied to the surface of the adhesive layer 2 in a predetermined pattern and dried to form a plating resist layer 6. After forming the plating resist layer 6, the insulating substrate 1 is immersed in a roughening solution consisting of a borohydrofluoric acid solution or an anhydrous chromic acid/sulfuric acid solution to form the adhesive layer 2, as shown in FIG.
The portions exposed from the plating resist layer 6 are roughened. After roughening the adhesive layer 2, the insulating substrate 1 is immersed in an electroless copper plating solution to deposit plating in a predetermined pattern to form a circuit 7 as shown in FIG. After forming the circuit 7, the insulating substrate 1 is
to produce printed wiring boards. Next, for the present invention and the conventional example, we measured the adhesion of plating inside the through-hole, the ratio of non-plated holes, the reliability, and the blowhole occurrence rate, and the results shown in the table were obtained. Ta. The adhesion of plating inside the hole for through holes is the time taken until plating is deposited on the entire surface of the inner wall of the hole, the ratio of holes without plating is the value 30 minutes after the start of electroless plating processing, and the reliability is MIL. -107D (-65℃, 30 minutes ~
The number of cycles at which the resistance value increases by 10% (thermal shock test at 125°C, 30 minutes cycle), the blowhole occurrence rate, is the number of cycles for soldering using an insulated substrate after being left in an atmosphere at a temperature of 40°C and relative humidity of 95% for 2 days. Conditions for raising
240℃ for 5 seconds. The manufacturing conditions were as follows in Example 1): a) Insulating substrate: An epoxy resin laminate (LE-44, manufactured by Hitachi Chemical Co., Ltd.) was coated with a plating catalyst-containing adhesive (HA-04, manufactured by Hitachi Chemical Co., Ltd.) and cured. thing. b) Thermosetting resin layer forming step: Epoxy resin emulsion (Epolsion manufactured by Kanebo NSC)
Hardening agent EB- for 100 parts by weight of solid content of EA-1
1) to which 80 parts by weight of 1) was added, palladium liquid
PEC-8 (Plating catalyst manufactured by Hitachi Chemical Co., Ltd.) with a palladium concentration of 0.03 per 100 parts by weight of resin
After immersing in a solution with a concentration of 5% by weight, the emulsion on the surface of the adhesive is removed using a puff, and the process of heating and drying using natural convection of air heated to about 100°C is repeated twice. . c) Plating catalyst adhesion step: A plating catalyst (HS-101B manufactured by Hitachi Chemical Co., Ltd.) is applied only to the hole wall surface. d) Thermosetting step: The thermosetting resin layer is thermally cured by heating and drying at a temperature of 150°C for 30 minutes. e) Plating resist step: Plating resist ink (HGM-02BK-1 manufactured by Hitachi Chemical Co., Ltd.) is screen printed and cured by heating at a temperature of 160° C. for 30 minutes. f) Roughening step: The surface of the adhesive layer is roughened with a borofluoric acid-based roughening liquid, washed and dried. g) Electroless plating process: A 25 μm thick copper layer is formed by electroless copper plating. In Example 2), the immersion and heating drying process of b) in Example 1) was repeated three times. Example 3) uses an epoxy resin laminate containing a plating catalyst (LE-144 manufactured by Hitachi Chemical Co., Ltd.) as the insulating substrate of a) in Example 1), and a comparative example uses Example 1). ,b) immersed in
The heat drying process is performed once, and the conventional example is the same as Example 1), but the thermosetting resin layer forming step b) is omitted.

[Table] As is clear from the table, according to the present invention, the plating adhesion is 7 times faster than that of the conventional example, the ratio of holes with no plating is 0 [%], and after 30 minutes all the holes are While plating is formed on the thermosetting resin layer on the wall surface, plating is formed on 10% of the holes in the comparative example and 100% in the conventional example, and the reliability is lower than that of the comparative example. 25%, about 108% better than the conventional example, and the blowhole occurrence rate is about 25% better than the conventional example.
This is a reduction of 88%, which is approximately 97% less than the conventional example. (Effects) As described above, according to the present invention, by repeating the process of plating an insulating substrate by immersing it in a thermosetting resin solution containing a catalyst, taking it out, and drying it two or more times, a semi-hardened resin is formed on the hole wall surface. At the same time as forming a layer, a plating catalyst is attached to this resin layer, and then the resin layer is thermally cured, so plating precipitation is accelerated.
A method for manufacturing a printed wiring board can be obtained that can shorten manufacturing time, improve reliability, and significantly reduce the incidence of blowholes.

[Brief explanation of drawings]

1 to 7 show the manufacturing process of an embodiment of the present invention, FIG. 1 is a cross-sectional view of an insulating substrate provided with an adhesive layer, FIG. 2 is a cross-sectional view of an insulating substrate with holes formed, and FIG. The figure is a sectional view of an insulating substrate in which a thermosetting resin layer containing a plating catalyst is provided on the hole wall, FIG. 4 is a sectional view of an insulating substrate in which a plating catalyst is attached to a thermosetting resin layer, and FIG.
The figures are a cross-sectional view of an insulating substrate provided with a plating resist layer, FIG. 6 is a cross-sectional view of an insulating substrate with a roughened adhesive layer, and FIG. 7 is a cross-sectional view of an insulating substrate provided with a circuit. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Adhesive layer, 3... Hole, 4... Thermosetting resin layer, 5... Plating catalyst, 6... Plating resist layer, 7... Circuit.

Claims (1)

[Claims] 1. An insulating substrate having holes for through holes and coated with a plating catalyst-containing adhesive is subjected to a roughening treatment to roughen the adhesive, and then a predetermined circuit is formed by electroless plating. In a method for manufacturing a printed wiring board, a process of immersing an insulating substrate in a thermosetting resin solution containing a plating catalyst and drying is repeated two or more times to form a semi-cured thermosetting state containing the plating catalyst on the hole wall surface. a step of forming a thermosetting resin layer; a step of attaching a plating catalyst to the thermosetting resin layer after the step;
A method for manufacturing a printed wiring board, which comprises performing a step of thermosetting the thermosetting resin layer after the step.