JPS61102092A - Manufacture of printed wiring 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 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 using an additive method such as the CG-4 method,
An adhesive layer containing a plating catalyst is previously provided on the surface of the insulating substrate. Additionally, insulating substrates usually contain catalysts for electroless plating, such as palladium-based catalysts, but when holes are provided for through-holes, it becomes difficult for plating to deposit in the holes. After forming the pores and before electroless plating, a plating catalyst is attached to the pores.

(Problems to be Solved by the Invention) By the way, usually, after the plating catalyst is attached to the holes, an adhesive layer is added to improve the adhesion between the adhesive layer and the plating circuit formed by electroless plating. is becoming coarser. The adhesive layer is roughened by immersing the insulating substrate in a roughening solution such as a borofluoric acid solution or an chromic anhydride RA acid solution. Most of it is washed away. Therefore, even if electroless plating is performed later, it takes time for the glitter to precipitate at the holes, and the precipitated plating film is thin and has a low peel strength. Therefore, when applying solder plating to the hole using solder dip, etc., or when connecting electronic components, the dipping film provided on the inner circumferential surface of the hole is partially thin, and the gas in the insulating substrate may cause the plating on the hole wall. There is a drawback that the film is peeled off and released into the holes, causing defects (hereinafter referred to as blowholes) in the solder that fills the holes. 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.

The present invention improves the above-mentioned drawbacks, and provides a method for manufacturing printed wiring boards that facilitates plating deposition on the hole wall surface for through holes, shortens manufacturing time, prevents blowholes, and has high reliability. This is the purpose.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a method of forming a predetermined shape by electroless plating on an insulating plate having holes for through holes and coated with an adhesive containing a plating catalyst. In a method for manufacturing a printed wiring board that forms a circuit, an insulating plate is immersed in a thermosetting resin solution containing a plating catalyst, and ultrasonic vibrations are applied to the thermosetting resin solution to form holes containing the plating catalyst. Provided is a method for manufacturing a printed wiring board, which comprises a step of applying a thermosetting resin, and a step of drying the thermosetting resin containing the plating catalyst adhering to the holes after the step. .

(Function) In other words, if the insulating substrate after hole formation is simply immersed in a thermosetting resin solution containing a plating catalyst, it is difficult for the thermosetting resin to adhere to the hole wall surface, and almost no resin adheres to the inside. Some holes do not. However, according to the present invention, since ultrasonic vibrations are applied to the thermosetting resin liquid, the thermosetting resin can enter even the narrowest holes and adhere to the wall surface. Therefore, even if the insulating substrate is subsequently immersed in a roughening solution, the thermosetting resin containing the plating catalyst can remain sufficiently attached to the pore walls. A thick plating is deposited in a short time to form a plating layer.

Moreover, since the resin layer can prevent gas in the insulating substrate from being released through the hole walls, blowholes can be prevented when solder plating or the like is performed.

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

First, as shown in FIG. 1, an adhesive containing a plating catalyst such as palladium is applied to an insulating substrate 1 made of a paper-phenol resin base material or a paper-epoxy resin base material to form an adhesive ff12. Next, as shown in Figure 2, this adhesive JII
A hole 3 for a predetermined through hole is formed by punching the insulating substrate 1 on which the hole 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.

After washing with water, the insulating substrate 1 is immersed in an emulsion of a thermosetting resin containing a plating catalyst, and immersed in this emulsion at 50K.
By applying ultrasonic vibration of Hz to 1 MH2, 2 to
Attach a thermosetting resin of about 10 μm. As the thermosetting resin, epoxy resin, urethane resin, polyester resin, etc. are used, but when the insulating substrate 1 is made of phenol resin or epoxy resin, epoxy resin is preferred because of its good adhesion to the substrate. Furthermore, as the curing agent, amine-based curing agents are preferable because they provide stable emulsions. The solid content 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 curing agent becomes low and the resin becomes difficult to cure;
If the amount is more than that, the resin may be coated so as to close the holes, which requires removal work, which is not preferable in terms of work. The plating catalyst is preferably a palladium-based catalyst used in combination with a palladium compound or a tin compound, and is preferably added and dispersed in an amount of 0.005 to 0.5 ffi (1 part) per 100 parts of the resin (o, oos weight). If the thermosetting resin solution is less than 0.51 parts, the catalytic effect will be low, and if it is more than 0.51 parts, the price will be high (the manufacturing cost will be high, and the effect will be close to saturation).Furthermore, as the thermosetting resin solution, a normal solvent solution may be used. However, emulsions and aqueous solutions are preferable because they do not cause skin formation during the subsequent drying process.After the insulating substrate 1 is immersed in the emulsion, the emulsion on the surface is removed using a squeezing roller or a puff. After removal, use hot air or a fan with natural convection of heated air!l1
The thermosetting resin adhered to the hole wall is heated and dried by hot air in a state where air is forcibly heated by, for example, being circulated to a semi-cured state, and as shown in FIG. 3, the thermosetting resin layer 4
form. After semi-curing the thermosetting resin w14, the insulating substrate 1 is immersed in a solution of a palladium-based plating catalyst, and as shown in FIG. 4, a plating catalyst 5 is applied to the surface of the thermosetting resin layer 4.
The thermosetting resin 114 is attached and taken out, and the thermosetting resin 114 is heated and cured. After curing the thermosetting resin H4, the insulating substrate 1 is immersed in a roughening solution consisting of a borofluoric acid solution or an anhydrous chromic acid/sulfuric acid solution to roughen the adhesive Fm2 as shown in FIG.

After roughening the adhesive layer 2, a plating resist ink is applied in a predetermined pattern and dried to form a plating resist 116 as shown in FIG. After forming the plating resist 1116, the insulating substrate 1 is immersed in an electroless copper plating solution to deposit plating in a predetermined pattern to form the circuit 7 as shown in FIG. After forming the circuit 7, the insulating substrate 1 is processed in a conventional manner to produce a printed wiring board.

Next, the plating adhesion inside the through-hole, the through-hole reliability, and the blowhole occurrence rate were measured for the present invention, comparative example, and conventional example, and the results shown in the table were obtained.

■The adhesion of plating inside the hole for through-holes is the time it takes for the plating to deposit on the entire inner wall of the hole and become copper-colored.■The ratio of holes where no plating adheres is the value measured 30 minutes after the start of the plating process. ■Through hole reliability is MIL-107D (-6
Thermal shock test by cycles of 5°C, 30 minutes to 125°C, 30 minutes) The number of cycles at which the resistance value increases by 10%,
(2) The blowhole generation rate is measured using a board immediately after 2 days of soldering in an atmosphere of 40°C and 95% relative humidity under soldering conditions of 240°C for 5 seconds.

The manufacturing conditions were as follows in Example 1): a) M edge substrate: An adhesive containing a plating catalyst was applied and cured on an epoxy resin aWj board (ACL-manufactured by Hitachi Chemical Co., Ltd.).
E-144K).

b) Thermosetting resin layer forming process! ! : Palladium liquid PEC-8 (Plating manufactured by Hitachi Chemical Co., Ltd.) was added to an epoxy resin emulsion (1 part by weight of curing agent EB-1 was added to 1 part by weight of 80 parts by weight of solid content of Epolsion EA-1 manufactured by Kanebo NSC). *,> was immersed in a solution with a concentration of 5% palladium added so that the palladium concentration was 0.03 folds per 100 parts by weight of resin, and the solution was heated at 500 KHz.
After treatment by applying ultrasonic vibrations, the emulsion on the surface of the adhesive is removed using a puff, and the adhesive is further heated by natural convection of air heated to about 100''C.

C) Plating catalyst adhesion step: A plating catalyst (H8-101B manufactured by Hitachi Chemical Co., Ltd.) is applied into the holes and dried.

d> Plating resist step: Plating resist ink (HGM-028-1 manufactured by Hitachi Chemical Co., Ltd.) is screen printed and cured by heating at a temperature of 160° C. for 30 minutes.

e) Roughening step: The surface of the adhesive layer is roughened using a borofluoric acid-based roughening liquid and then washed.

f) Electroless plating process 8: Form a copper layer with a thickness of 25 μm by electroless copper plating process.

In Example 2), the intensity of the ultrasonic vibration was 100 KHz in Example 1), and in the comparative example, in Example 1),
In the conventional example, in Example 1), ultrasonic imaging is omitted.
The thermosetting resin layer forming step b) is omitted.

As is clear from the table, according to the present invention, the plating adhesion is about 86% or less compared to the conventional example, and the ratio of pores to which no glare adheres is 0% in the present invention, compared to the comparative example. The ratio was 10% for the example and 100% for the conventional example, indicating that the present invention facilitates plating on the inner wall surface of the hole.

Furthermore, according to the present invention, the reliability is 25% higher than that of the comparative example.
This is an improvement of approximately 108% over the conventional example. The blowhole occurrence rate was also reduced to 1/17 compared to the comparative example and to 1/35 compared to the conventional example.

(Effects) As described above, according to the present invention, an insulating substrate after hole formation is immersed in a thermosetting resin liquid containing a plating catalyst, and
Because ultrasonic vibration is applied to this solution, the resin adheres effectively to the inner wall surface of the hole, which accelerates plating deposition during electroless plating, shortens manufacturing time, and reduces the incidence of blowholes. A method for manufacturing a printed wiring board with low cost and high reliability can be obtained.

[Brief explanation of the drawing]

Figures 1 to 7 show the manufacturing process of the embodiment of the present invention.
The figure is a cross-sectional view of an insulating substrate provided with an adhesive layer, Figure 2 is a cross-sectional view of an insulating substrate with holes formed, and Figure 3 is a cross-sectional view of an insulating substrate with a thermosetting resin layer containing a plating catalyst provided on the hole wall. 4 is a cross-sectional view of an insulating substrate with a plating catalyst attached to a thermosetting resin layer, and FIG. 5 is a cross-sectional view of an insulating substrate with a roughened adhesive layer.
FIG. 6 is a cross-sectional view of an insulating substrate provided with a plating resist layer,
FIG. 7 shows 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) In a method for manufacturing a printed wiring board in which a predetermined circuit is formed by electroless plating on an insulating plate having holes for through holes and coated with a plating catalyst-containing adhesive, the insulating plate is plated and a catalyst-containing adhesive is applied. A step of attaching the thermosetting resin containing the plating catalyst to the hole by immersing it in a thermosetting resin solution containing the plating catalyst and applying ultrasonic vibration to the thermosetting resin solution, and a step of attaching the thermosetting resin containing the plating catalyst to the hole after this step. A method for manufacturing a printed wiring board, comprising the step of drying the thermosetting resin containing the plating catalyst.