JPH0248154B2 - INSATSUHAISENBANNOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a printed wiring board using 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 CC-4 method, an adhesive layer containing a plating catalyst is applied on the surface of an insulating substrate in advance. has been established. 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, in order to improve the adhesion between the adhesive layer and the plating circuit formed by electroless plating, after the plating catalyst is attached to the holes, the adhesive is The 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 an electroless plating treatment is performed later, it takes time for the plating to precipitate at the holes, and the deposited plating film is thin and has a low peel strength. Therefore, when soldering the hole with solder dip or connecting electronic components, etc., the dipping film provided on the inner circumferential surface of the hole is partially thin, and the gas inside the insulating substrate can leak onto the hole wall. The solder film is peeled off and the hole is filled with solder, and the solder is pushed out from inside the hole and covers only the surface of the entrance (hereinafter referred to as a blowhole). 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. In addition, in the electroless plating method, a plating resist is provided on the adhesive layer, but conventionally, if the activity of the plating solution becomes abnormally high or if the adhesive is not washed sufficiently, the plating resist surface It has the disadvantage that it can cause a short circuit due to the precipitation of glare. In order to prevent such defects, after the electroless plating process, the adhered plating can be dissolved with an etching solution, roughened with a roughening solution, and then the electroless plating process can be performed again.
However, since the roughening process is repeated, the plating catalyst in the pores is further washed away, which is not preferable. (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides a method for applying a predetermined method by electroless plating to an insulating substrate having holes for through holes and coated with a plating catalyst-containing adhesive. A method for manufacturing a printed wiring board on which a circuit can be formed includes a step of immersing an insulating substrate in a thermosetting resin, plating the hole wall surface, and applying a catalyst-containing thermosetting resin; Printed wiring that is subjected to a step of heating the thermosetting resin attached to the hole wall surface with hot air at a wind speed, and a step of immersing the insulating substrate in a roughening liquid after forming a plating resist layer to roughen the adhesive layer. A method for manufacturing a board is provided. (Function) That is, according to the present invention, a thermosetting resin layer containing a plating catalyst is previously provided on the wall surface of a through hole provided in an insulating substrate, and in order to semi-cure or harden the layer, Since hot air is used at a speed that does not remove the resin, the thermosetting resin is evenly adhered to the hole walls. Then, with the thermosetting resin attached to the hole walls in this manner, a plating catalyst is attached. Therefore, even if the insulating substrate is subsequently immersed in a roughening solution, the plating catalyst can remain sufficiently adhered to the pore walls, and the electroless plating process allows the pore walls to have a sufficient thickness. Plating precipitates in a short period of time, forming a plating layer. Moreover, since the thermosetting 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. Further, even if the roughening treatment and electroless plating treatment are repeated, there is no effect on the plating deposited on the hole walls, so it is possible to prevent short circuit failures caused by plating adhering to the plating resist. According to the present invention, compared to the case where a plating catalyst is attached to a thermosetting resin layer that does not contain a plating catalyst or the case where a plating catalyst is not attached only to a thermosetting resin layer containing a plating catalyst, The plating is deposited quickly, and the reliability and blowhole occurrence rate are also improved. (Examples) Hereinafter, the present invention will be described based on Examples. 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, holes 3 for predetermined through holes 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.
The insulating substrate 1 after washing with water is immersed in an emulsion of thermosetting resin containing a plating catalyst, and as shown in FIG. will be established. Epoxy resin, urethane resin, polyester resin, etc. are used as the thermosetting resin, but when the insulating substrate 1 is made of phenol resin or epoxy resin, epoxy resin is preferable because of its good adhesion to the substrate. As the curing agent, an amine-based curing agent is preferable because a stable emulsion can be obtained, and the solid content concentration in the emulsion is particularly preferably in the range of 0.3 to 5 wt%, that is, 0.3 wt%.
If the concentration is less than 5% by weight, the effect as a curing agent will be reduced and the resin will be difficult to cure, and if the concentration is more than 5wt%, the resin may be coated so as to close the pores, making removal work necessary, which is undesirable for 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 in an amount of 0.005 to 0.5 parts by weight per 100 parts by weight of the resin.If it is less than 0.005 parts by weight, the catalyst efficiency is low; 0.5
If the amount exceeds parts by weight, the price and manufacturing costs will increase. After the insulating substrate 1 is immersed in the emulsion, the emulsion on the surface is removed using a squeezing roller or a buff. After removing the surface emulsion,
Air that is forcibly heated by an electric fan, etc. is
The thermosetting resin adhering to the hole wall is heated and dried by hot air of less than sec to a semi-cured or hardened state. After semi-curing the thermosetting resin layer 4, the insulating substrate 1 is immersed in a palladium-based plating catalyst solution to adhere the plating catalyst 5 to the surface of the thermosetting resin layer 4, as shown in FIG. . After adhering the plating catalyst 5 to the surface of the thermosetting resin layer 4, plating resist ink is applied in a predetermined pattern and dried to form a plating resist layer 6 as shown in FIG. The resin layer 4 is cured. After forming the plating resist layer 6, 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 layer 2, as shown in FIG. . Adhesive layer 2
After roughening, the insulating substrate 1 is immersed in an electroless copper plating solution to deposit plating in a predetermined pattern.
As shown in FIG. 7, a circuit 7 is formed. 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 and the conventional example, and the results shown in the table were obtained.

[Table] The adhesion of plating inside the hole for through holes is the time until plating is deposited on the entire inner wall of the hole, and the through hole reliability is MIL-107D (-65℃, 30 minutes to 125℃,
The number of cycles at which the resistance value increases by 10% (thermal shock test with a 30-minute cycle) and the blowhole occurrence rate are determined by soldering conditions of 240°C and 5 seconds. The manufacturing conditions of Example 1) were as follows: a) Insulating substrate: An epoxy resin laminate plate was coated with a plating catalyst-containing adhesive (HA-04 manufactured by Hitachi Chemical Co., Ltd.) and cured. 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
After immersing PEC-8 (a plating catalyst manufactured by Hitachi Chemical Co., Ltd.) in a 1% solution containing palladium at a concentration of 0.03 parts by weight per 100 parts by weight of resin, the emulsion on the adhesive surface was removed by buffing. is removed, and further heated with hot air heated to about 100°C at a wind speed of 3 m/sec. c) Plating catalyst deposition step: Apply a plating catalyst (HS-101B manufactured by Hitachi Chemical Co., Ltd.) and heat at a temperature of 150°C for 30 minutes. d) Plating resist process: Screen printing the plating resist ink (HGM-02BK-1 manufactured by Hitachi Chemical Co., Ltd.) and curing it 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, washed and dried. f) Electroless plating process: A copper layer is formed by a normal electroless copper plating process, and after the formation, the copper layer is removed using a ferric chloride aqueous solution. A copper layer with a thickness of 30μ is formed by roughening with a chemical solution and then electroless plating again. In Example 2), 10 parts by weight of nitrile butadiene rubber (Higher 1522 manufactured by Nippon Zeon Co., Ltd.) was added to 100 parts by weight of the thermosetting resin in Example 1), and in Example 3), In Example 1), the roughening liquid was a sodium fluoride/chromium sulfate system, and in Example 4), hot air heated to about 100°C at a wind speed of 4.5 m/sec was used after removing the emulsion in step b) in Example 1). Example 5) was heated with hot air at a wind speed of 5 m/sec heated to about 100°C after the emulsion was removed in step b) in Example 1), and Example 6) was heated with Example 1). In step b), after removing the emulsion, heating was performed using hot air heated to about 100° C. at a wind speed of 5.5 m/sec, and the conventional example was obtained by omitting step b) in Example 1). As is clear from the table, according to the present invention, the plating adhesion of the through-hole wall surface is about 1/12 or less compared to the conventional example, and the plating precipitation rate is increased.
In addition, the reliability of through-holes is approximately three times higher.
Furthermore, the blowhole occurrence rate is reduced to less than 1/50. In addition, according to the present invention, the wind speed of the hot air is 5
It is clear that when the speed exceeds m/sec, the plating adhesion increases rapidly, and therefore 5 m/sec or less is preferable. (Effects of the Invention) As described above, according to the present invention, a thermosetting resin layer containing a plating catalyst is evenly provided on the hole wall surface of a through hole, and a plating catalyst is further attached to the hole wall surface. A method for manufacturing a printed wiring board which can accelerate plating deposition, shorten manufacturing time, and have a low blowhole occurrence rate and high reliability can be obtained.

[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. In a method for manufacturing a printed wiring board in which a predetermined circuit and through holes are formed by an electroless plating method on an insulating substrate having holes for through holes and coated with a plating catalyst-containing adhesive, an insulating substrate is plated. A step of applying the thermosetting resin containing a catalyst to the hole wall surface by immersing it in an emulsion of a catalyst-containing thermosetting resin, and after this step, the heat attached to the hole wall surface by hot air at a wind speed of 5 m/sec or less. A method for manufacturing a printed wiring board, comprising: heating a curable resin; and after forming a plating resist layer, immersing an insulating substrate in a roughening liquid to roughen an adhesive layer.