JPS60235495A - Method of producing printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method of manufacturing a printed wiring board by an additive method.

<Conventional technology> Conventionally, when manufacturing a printed wiring board by forming a circuit by electroless plating using an additive method such as the CC-4 method,
An adhesive layer containing a plating catalyst is provided in advance on the surface of the insulating substrate. In this case, if the insulating substrate is provided with holes for through-holes, after the holes are formed and before electroless plating, a plating catalyst is attached to the holes.

(Problems to be Solved by the Invention) By the way, normally, in order to improve the adhesive strength between the adhesive layer and the plating circuit formed by electroless plating, the adhesive layer is The adhesive layer is roughened by immersing the insulating substrate in a roughening solution such as a borofluoric acid solution or an anhydrous chromic acid/sulfuric acid solution. Most of the plating catalyst that adheres to the wall is washed away. Therefore, even if electroless plating is performed later, it takes time for the plating to precipitate in the holes, and the precipitated plating film is thin and has poor mechanical strength. Furthermore, when solder plating is applied to lands, etc., the plating layer provided on the hole wall surface is conventionally thin, and the gas in the insulating substrate is released from the inner peripheral surface of the hole, causing this gas to enter the hole. This has the disadvantage that the surface of the hole is covered with solder (hereinafter referred to as a blowhole) because the hole is filled with solder.

(Objective) The present invention improves the above-mentioned drawbacks, facilitates plating deposition on the hole wall surface for through holes, shortens manufacturing time, and prevents solder plating defects to provide a highly reliable printed wiring board. The purpose of this invention is to provide a method for manufacturing.

(Means for Solving the Problem) In order to achieve the above object, the present invention forms a plating resist layer on an insulating plate having through holes and coated with an adhesive containing a plating catalyst. In the method for manufacturing a printed wiring board, the method includes a step of roughening the surface of the adhesive layer, and a step of forming a circuit by electroless plating, wherein a thermosetting resin layer containing a plating catalyst is formed on the wall surface of the hole. The present invention provides a method for manufacturing a printed wiring board, characterized in that after the process of forming a plating resist layer, a process of forming a plating resist layer is performed. The plating catalyst is stronger than when the plating catalyst is applied directly to the wall surface, and the thermosetting resin layer does not peel off easily even if the insulating substrate is subsequently immersed in a roughening solution. . Therefore, by performing the electroless plating process, a sufficient thickness of plating is deposited on the inner wall of the hole in a short time to form a plated layer. Moreover, since the thermosetting resin layer can prevent the gas in the insulating substrate from being released through the hole walls, blowholes can be prevented during subsequent solder plating processing. In addition, since the plating resist layer is provided after forming the thermosetting resin layer containing the plating catalyst, the plating catalyst does not adhere to the surface of the plating resist layer and the plating precipitates on the surface of the plating resist layer. It is possible to prevent defects such as short circuits between the two.

(Example) Hereinafter, the present invention will be explained based on examples.

First, an adhesive containing a plating catalyst such as palladium is applied to an insulating substrate made of a paper-phenol resin base material or a paper-epoxy resin base material to form an adhesive layer. Next, the insulating substrate with the adhesive layer formed thereon is removed by punching to remove substrate debris. A thermosetting resin layer having a washability μ level is provided. As a plating catalyst, a palladium-based catalyst is preferred, and one in which palladium is adhered to the surface of an aluminosilicate carrier is usually used, but a type formed with an epoxy resin chelate is also used. As the thermosetting resin, epoxy resin, urethane resin, polyester resin, etc. are used, but when the insulating substrate is made of phenol resin or epoxy resin, epoxy resin is preferred because of its good adhesion to the substrate. Further, as the curing agent, an amine type curing agent is preferable since a stable emulsion can be obtained, and a curing agent in the range of 0.3 to 5 wt% is particularly preferable. In other words, if the amount is less than 0.3 wt%, the effect as a curing agent will be low, making it difficult for the resin to harden, and if it is more than 5 wt%, the resin may be coated to block the pores, making it difficult to remove. This requires additional work, which is undesirable from a work standpoint.In addition, in order to improve the adhesion to the precipitated plating, this thermosetting resin may contain a filler that dissolves in the roughening liquid. As the agent, calcium carbonate or silica powder or butadiene rubber such as nitrile butadiene rubber or styrene butadiene rubber is used.After forming a thermosetting resin layer in the holes of the insulating substrate,
After the insulating substrate is immersed in the emulsion, it is taken out, the emulsion on the surface of the insulating substrate is removed using a squeezing roller, and the insulating substrate is dried by passing it through a high-temperature atmosphere to harden the resin layer provided on the wall of the hole. . After the resin layer is cured, a mesh resist ink is applied in a predetermined pattern and dried to form a mesh resist layer, which is then cured. After forming the plating resist layer, the insulating substrate is coated with a borofluoric acid solution or anhydrous chromium I! The adhesive layer is roughened by immersing it in a roughening solution consisting of an acid solution. After roughening the adhesive layer, the insulating substrate is immersed in an electroless copper plating solution to deposit plating in a predetermined pattern to form a circuit. After forming the circuit, the insulating substrate is processed using conventional methods to produce a printed wiring board.

Next, we measured the plating adhesion inside the through-hole, the through-hole reliability, the blowhole occurrence rate, and the plating precipitation state on the surface of the plating resist layer for the present invention and the conventional example, and the results are shown in the table. Obtained.

The adhesion of plating inside the surface through hole is the time required for the plating to deposit on the entire inner wall of the hole, and the reliability of the through hole is the MIL.
-107D (thermal shock test with cycles of -65℃, 30 minutes to 125℃, 30 minutes) The number of cycles at which the resistance value increases by 10%, the blowhole occurrence rate is the soldering condition: 240℃, 5 seconds, plating The state of plating precipitation on the surface of the resist layer was visually measured.

The manufacturing conditions of Example 1) were as follows: a) Insulating substrate: An adhesive containing a plating catalyst (HA-04 manufactured by Hitachi Chemical Co., Ltd.) was applied and cured on an epoxy resin laminate.

b) Thermosetting resin layer forming step: Resin content 100ffi in epoxy resin emulsion (80 weight parts of curing agent EB-1 added to 100 ml solid content of Epolsion EA-1 manufactured by Lanebou N80)! 20 parts by weight of calcium carbonate and a plating catalyst (manufactured by Hitachi Chemical Co., Ltd.)
t-10) 5 parts by weight was added and dispersed in an 8°C 1% solution, the emulsion on the surface of the adhesive was removed with a puff, and the adhesive was heated to 100°C. ' - Dry for 10 seconds and then dry at 160℃ for 3
Heat and cure for 0 minutes.

C) Plating resist ■Culm: Screen-printing the plating resist ink (Hitachi Chemical Co., Ltd.! NHG M-028K-1) and drying and curing at 160° C. for 30 minutes.

d) Roughening step: Immerse and wash in a roughening solution based on chromic anhydride, sulfuric acid, and sodium fluoride.

e) Electroless plating process 2 Normal electroless copper plating treatment (C
G-4 plating treatment) to form a 30μ thick copper layer.

In Example 3), calcium carbonate was removed from the thermosetting resin in Example 2), and in Example 4), Example 1) was added. In Conventional Example 1), the step of forming a thermosetting resin layer was omitted in Example 1, and in Conventional Example 2), the thermosetting resin was used in Example 1). Seeder treatment (seeder: H8-101B manufactured by Hitachi Chemical Co., Ltd.) was performed instead of the layer forming step, and in the comparative example, the thermosetting resin forming step was performed after the plating resist step in Example 1>, and the surface of the plating resist layer was The emulsion is removed with a puff.

As is clear from the table, according to the present invention, compared to the conventional example, the plating adhesion on the hole wall surface for through-holes is reduced by about 67% or more, the plating deposition rate is more than three times faster, and the reliability of through-holes is improved. is approximately 1.6 times or more, and the blowhole occurrence rate has been reduced to less than 1/10. Further, according to the present invention, compared to a comparative example in which the thermosetting resin forming step was performed after the plating resist step, there is no plating precipitation on the surface of the plating resist layer, and short circuit defects can be prevented.

(Effects) As described above, according to the present invention, by performing the step of providing a thermosetting resin layer containing a plating catalyst on the hole wall surface of a through hole before the plating resist step, the metallization on the hole wall surface can be improved. It is possible to obtain a method for manufacturing a highly reliable printed wiring board, which can reduce the production time by reducing the occurrence of black deposits, have a low occurrence rate of b[1-holes, and prevent short-circuit defects.

Patent applicant: Hitachi Condenser Co., Ltd.

Claims (1)

[Claims] (1) A process of forming a plating resist layer on an insulating plate having holes for through holes and coated with an adhesive containing a plating catalyst, a process of roughening the surface of the adhesive layer, and an electroless plating process. The method for manufacturing a printed wiring board is characterized in that after the step of forming a thermosetting resin layer containing a plating catalyst on the wall surface of the hole, a step of forming a plating resist layer is performed. A method for manufacturing printed wiring boards.