JPH0317393B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a printed wiring board produced by an additive method. Conventional technology Conventionally, when manufacturing wiring boards by the additive method, an insulating substrate contains a plating catalyst such as palladium or a palladium compound, and an adhesive containing a plating catalyst is applied to the surface of the substrate. . Thereafter, holes for through holes were formed in the insulating substrate, and a seeder treatment was performed to improve the plating deposition rate in the holes. After the seeder treatment, remove the seeder on the substrate surface by buffing, then form a plating resist layer, roughen the surface of the adhesive layer, and immerse the substrate in electroless copper plating solution to form a conductive layer. The company manufactures wiring boards. Problems to be Solved by the Invention In the conventional manufacturing method of wiring boards, the surface roughening treatment of the adhesive layer is performed using acid. This has the disadvantage that it melts and removes the metal, slowing down the rate of plating precipitation inside the holes. If the plating precipitation inside the hole is delayed, the copper plating inside the hole will not be uniformly applied, causing plating voids (defects), which will cause blowholes during soldering in the post-process, resulting in solder defects. It is. In order to increase the rate of plating deposition in the holes, it is necessary to increase the amount of remaining seeder. However, increasing the concentration of the seeder or increasing the time for taping the substrate only increases the cost and does not provide any improvement. Furthermore, if the acid treatment time is shortened, the roughening of the adhesive surface becomes smaller, and the adhesive strength of the copper foil to the substrate decreases. Means for Solving the Problems The present invention aims to improve the above-mentioned drawbacks and provide a printed wiring board which has a fast plating deposition rate and does not cause defects in solder processing. The present invention uses an insulating substrate coated with an adhesive containing a plating catalyst as a base material, drills holes for through holes in this base material, performs a seeder treatment, and forms the inner wall of the through hole by hydrolyzing metal alkoxide. A printed wiring board is produced by providing a metal oxide film, forming a plating resist layer on the base material surface, chemically roughening the adhesive surface, cleaning with an alkaline solvent, and forming a copper circuit with an electroless plating solution. This is the manufacturing method. Metal alkoxides are generally designated M(OR)n.
M is a metal such as Si, Ti, Al, Zr, Fe, etc., R is an alkyl group such as methyl, ethyl, butyl, and n is 1
It is an integer of ~4. Mainly used is Si
( _OC2H5 ) ₄ , _{Al ( OC4H9} ) _{3 ,} Ti( _OC3H11 ) ₄ , Ba
(OC ₃ H ₇ ) ₂ , etc., and is used after being diluted with water to a specified concentration. These alkoxides generate alcohol and the like through hydrolysis or thermal decomposition and crosslink, forming a metal oxide film. Usually, an acid is added just before use to speed up hydrolysis. These metal oxides are relatively resistant to acids, but not strong alkalis. When roughening the adhesive surface, the usual roughening liquid is
H ₂ SO ₄ , NaF, Cr ₂ O ₅ or HBF ₄ ,
Na ₂ Cr ₂ O ₇ system is used, but depending on these acids,
The film provided on the inner wall of the hole remains undissolved and protects the cedar layer. After this, when washed with an alkaline solution, the metal oxide film is dissolved and the cedar is exposed.
The thickness of the film may be several μm. The metal oxide film can be adjusted by adjusting the metal alkoxide concentration and the addition of fillers. As a filler,
SiO ₂ , Al ₂ O ₃ , BaO, TiO ₂ , etc. are used, and their fine powders are uniformly dispersed. The drilled substrate is immersed in a metal alkoxide solution, coated on the inner walls of the holes, and then heated to about 150°C, dried and simultaneously hydrolyzed to form an oxide film. At this time, the film formed on the surface of the adhesive is removed with a buff or the like, and an oxide film layer is formed only within the holes. The alkaline cleaning solution varies depending on the thickness of the oxide film and the metal components, but an aqueous solution of NaOH or KOH is used at a concentration of 40 to 70%.
Warm to ℃ before use. The plating solution is usually used at a pH of around 12 and a temperature of 70 to 75°C. The above treatment increases the amount of seeder remaining in the pores, so even if the plating catalyst in the base material is omitted,
It is possible to produce a wiring board that exhibits sufficient plating and precipitation characteristics and that does not cause defects during soldering. Examples Example 1 Paper epoxy resin laminate containing a plating catalyst with a thickness of 1.5 mm (model HA-21, manufactured by Hitachi Chemical Co., Ltd.) coated with a plating catalyst-containing adhesive (model HA-21, manufactured by Hitachi Chemical Co., Ltd.) on the surface. ACL-E-144 type manufactured by Co., Ltd.) is used as the base material. After drilling holes for through holes in this base material and cleaning the inside of the hole, a cedar treatment (HS-201B manufactured by Hitachi Chemical Co., Ltd.) is performed to adhere the cedar to the inner wall of the hole. After this, it was treated with 10% sulfuric acid and immersed in a 10% by weight solution of an alkoxysilicate solution with TiO ₂ as a filler (Glasca G1100A manufactured by Nikken Institute).
Dry at ℃ for 30 minutes. Next, the adhesive surface is buffed to remove the cedar and oxide film adhering to the adhesive surface. Next, a plating resist ink (HNR-01BK manufactured by Hitachi Chemical Co., Ltd.) was screen printed to a thickness of 20 μm on a predetermined location on the base material, and left in an atmosphere at a temperature of 160°C for 30 minutes to harden and form a pattern opposite to the circuit. Form a plating resist layer. After this, the base material was treated with NaF (20 g/), H ₂ SO ₄ (400
ml/), Cr ₂ O ₅ (40 g/) at 40°C for 7 minutes to chemically roughen the surface of the adhesive.
After cleaning, 10% in caustic soda (10% by weight) solution at 70°C.
Process for 1 minute to remove the oxide film layer and expose the cedar. Next, the base material is immersed in an electroless plating solution to determine the thickness.
A 25 μm conductive circuit is formed, and a solder resist layer and character printing are then applied to produce a printed wiring board. Example 2 Based on Example 1, a printed wiring board was manufactured by using a TiO ₂ filler-free solution (Glaska G90 type manufactured by Nikken Research Institute) (solid content: 18%) and using the same process except for the same process. . Example 3 Based on Example 3, a printed wiring board is manufactured using the same process using a substrate that does not contain a plating catalyst (LE-47 manufactured by Hitachi Chemical Co., Ltd.). Comparative Example 1 A printed wiring board is manufactured using the method of Example 1, but omitting the alkoxide treatment. The characteristics of the wiring board produced by the above method are shown in the table.

【table】

[Table] Effects of the Invention The structure of the present invention is as explained above, and the through-hole plating performance is greatly improved, blowholes during soldering are significantly reduced, and correction work after soldering can be reduced. , the reliability of through holes has been improved. In addition, since the oxide film is removed in the alkaline cleaning tank before entering the plating solution tank, the introduction of impurities into the plating solution is greatly reduced, and this invention also contributes to improving the properties of the plated copper. be.

Claims (1)

[Claims] 1 A substrate coated with a plating catalyst-containing adhesive is used as a base material, and holes for through-holes are drilled in this base material.
A cedar treatment is performed to form a metal oxide film on the inner wall of the through-hole by hydrolysis of metal alkoxide, a plating resist layer is formed on the base material surface, the adhesive surface is chemically roughened, and then washed with an alkaline solvent. A method for manufacturing a printed wiring board, comprising: forming a conductive circuit by immersing a base material in an electroless plating solution.