JPH0149036B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to an improvement in a method for manufacturing multilayer printed wiring boards.

Conventional technology A conventional multilayer printed wiring board is made by alternately polymerizing and laminating an inner layer wiring board with wiring circuits formed on both sides and a prepreg, pressing them into one piece, drilling holes, and applying chemical copper plating and electrical coating to the entire surface. It is manufactured by applying copper plating and removing unnecessary copper layers by etching.

Problems to be Solved by the Invention When manufacturing multilayer circuit boards using conventional manufacturing methods,
In this method, after a conductor layer is formed on the entire surface by electrolytic copper plating, areas other than those where the circuit will be formed are removed by etching, resulting in wasted use of copper.
Therefore, we tried a method of forming the outer conductor layer by electroless plating. At this time, the adhesive strength of the insulating layer on the surface of the inner layer circuit board and the adhesive layer thereon decreases during the subsequent plating process and heat treatment process to form the outer layer conductor, and the solder when installing the components decreases. A peeling phenomenon sometimes occurred during processing.

Means for Solving the Problems The present invention forms a plating resist layer on an insulating board coated with an adhesive, performs electroless plating to provide an inner conductive layer to form an inner circuit board, and forms an inner circuit board by forming an inner conductor layer on an insulating plate coated with an adhesive. A method for manufacturing a multilayer printed wiring board, in which an insulating layer and an adhesive layer are formed on a board, a plating resist layer is provided, and an outer conductor layer is formed by electroless plating, the insulating layer being formed. When applying, the thickness of each coating should be 50μ.
Repeat coating and curing within m to achieve a predetermined thickness.

Effect The thickness of one coating is 50 μm to form an insulating layer.
It has been found that if the coating temperature exceeds 100%, the warpage of the substrate becomes large and the subsequent coating becomes uneven. If the thickness of the insulating layer is not 100 μm or more for a multilayer printed wiring board, the applications for which it can be used will be limited, so the coating must be applied two or more times. Warpage can be reduced by applying the coating alternately to the front and back surfaces of the substrate.

As the insulating material, an epoxy resin-based thermosetting resin is usually used, but a urethane-based or polyester-based cured resin is also used. As a coating method, a screen printing method, a roll coater method, a bar coater method, etc. may be used.

Also, the curing temperature of the insulating material is preferably 120°C or lower. If the temperature is raised, the warpage of the substrate increases, resulting in uneven thickness during the next overcoat application.

Example Examples of the present invention will be described.

Example 1 A plating resist ink was screen printed on a 0.8 mm thick paper phenolic resin laminate 1 coated with a plating catalyst-containing adhesive 2 to form a 20 μm thick plating resist layer 3, and cured (at 160°C). 30 minutes), then
The surface of the adhesive 2 was chemically roughened with a roughening solution consisting of hydroboric acid and sodium dichromate, and after cleaning, the inner layer was immersed in an electroless plating solution to form an inner conductor layer 4 with a thickness of 20 μm. Obtain the wiring board 10.

10% of the surface of the conductor layer 4 of this inner layer wiring board 10
After washing with a hydrochloric acid solution for 10 seconds and washing with water, it is immersed in γ-mercaptopropyltrimethoxysilane (0.3% aqueous solution, adjusted to pH 3-4 with glacial acetic acid) for 5 seconds, and then dried at 90°C for 10 minutes.

Next, as the insulating layer 6, a 40 μ thick layer was formed using an epoxy resin ink (HCTM-02BU-1 manufactured by Hitachi Chemical Co., Ltd.) using a bar coater method, and
The step of drying and curing for minutes was repeated alternately on both the front and back surfaces of the substrate. The insulating layer 6 was coated three times on both the front and back surfaces to form a three-layer insulating layer 6 with a thickness of about 120 μm.

Further, the adhesive layer 12 was applied to the surface of the insulating layer 6 by a curtain coater method, and dried by heating at 160° C. for 90 minutes to form the adhesive layer 12 with a thickness of 30 μm.

After that, a through hole 7 is drilled through the wiring board, a seeder treatment is performed in the hole, a plating resist layer 13 for the outer layer circuit is formed, and an adhesive 12 is formed using a roughening liquid.
After the surface was roughened and washed, the wiring board was immersed in an electroless plating solution to form an outer conductor layer 14. Furthermore, solder resist printing was performed to produce a four-layer printed wiring board 20.

This mounting plate 20 has no blistering phenomenon between layers during soldering (260°C, 10 seconds), and has MIL-107D (-
It has a reliability of more than 100 cycles in cooling/heating cycles (65℃, 125℃, 30 minutes). Furthermore, since the plating solution did not penetrate between the layers, there was no occurrence of corrosion accidents or electrical short circuit phenomena.

Example 2 In Example 1, the thickness of the insulating layer 6 was changed to 200 μm by applying 5 times with each coating thickness of 40 μm.

The same reliability as in Example 1 was obtained, and when the circuit of the outer layer conductor 14 was made into a 0.2 mm wide line, the impedance was 80 Ω, which was created using a high-pressure and high-temperature press.
Characteristics equivalent to those of layer wiring boards were obtained.

Comparative Example 1 In Example 1, the thickness of one coating of the insulating layer 6 was
A thickness of 70 μm was formed. The size of this wiring board is 330 x 330
After coating the insulating layer 6 with a thickness of 1.5 mm and drying it by heating, we actually measured the degree of warpage and found that it was 21 mm, so we could not carry out the next work.

Comparative Example 2 In Example 1, the heat curing temperature of the insulating layer 6 was
The temperature was set at 130°C. There was a warpage of 15mm on a wiring board with dimensions of 330 x 330mm, so I was unable to do the next work.

Effects of the Invention If the manufacturing method of the present invention is used, work efficiency is improved since a pressurizing step is not included, and a product with satisfactory reliability can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the inner layer wiring board, and FIG. 2 is a sectional view of the present invention. In the drawings, 1...insulating plate, 2...adhesive,
3...Plated resist layer, 4...Inner conductor layer,
6...Insulating layer, 10...Inner layer wiring board, 12...Adhesive layer, 13...Plating resist layer, 14...Outer conductor layer, 20...Multilayer printed wiring board.

Claims (1)

[Claims] 1. An adhesive layer containing a plating catalyst is formed on both sides of an insulating substrate, a plating resist layer is formed at predetermined locations on the surface of this adhesive layer, and an inner conductive layer is formed at locations other than this plating resist layer. An insulating layer is repeatedly coated on the surface of this inner layer wiring board with a thickness of 50 μm or less each time, an adhesive layer is formed thereon, and a plating resist layer is applied. 1. A method for producing a multilayer printed wiring board, comprising forming an outer conductor layer after forming the outer conductor layer.