JPS5815952B2 - Manufacturing method for adhesive coated laminates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing adhesive coated laminates required in the production of printed wiring circuit boards using chemical copper plating.

Conventionally, laminates with a thin metal film on the surface, ie copper-clad laminates for printed circuits, have been used as base materials for circuit boards, and are mainly made by bonding a predetermined amount of paper or cloth impregnated with epoxy resin, phenolic resin, etc. It is manufactured by hot-pressing lamination of copper foil coated with a chemical agent, and a circuit is printed on the copper foil surface.
Thereafter, the copper foil other than the circuit portion is chemically etched away to form a wiring circuit on the insulating substrate (laminated board).

However, this method using copper-clad laminates is wasteful because most of the copper foil on the board is etched and discarded, and the holes (through-holes) formed by the hole etching process are naturally coated with metal. Therefore, another metallizing treatment was required.

On the other hand, in contrast to the printed circuit method, emphasis has been placed on a method in which circuits are formed by performing electroless plating directly on the laminate and on the walls of through holes.

This process involves coating the laminate with an adhesive that can firmly adhere to metal, heating and curing it, and then applying a meth-resist to the adhesive surface other than the circuit area, while chemically oxidizing and roughening the circuit area. , a circuit is formed by depositing metal on an adhesive film in an autocatalytic plating bath, and it is possible to simultaneously deposit metal into through holes.

However, the circuit board is manufactured using the method using the copper-clad laminate,
In either case of electroless plating, after the circuit is formed, the installation requires a process of inserting the terminal of the component and solidifying it, and the process of soldering is necessary. In addition to the requirement for excellent adhesive properties, a high degree of heat resistance is also required, and generally a thermosetting adhesive or thermosetting component is essential, and a sufficient heat curing process is required.

However, the process of sufficiently heating and curing the adhesive applied to the laminate is a process that causes several drawbacks for laminates that have already undergone a heat-pressure lamination process.

That is, (1) since the heating process is repeated more than necessary, it is inevitable that the laminate itself will undergo thermal deterioration, resulting in a decrease in mechanical and electrical performance, and a significant decrease in workability.

To explain in more detail, laminates that could be punched at room temperature often become difficult to properly punch, hole, etc. after the adhesive heat curing process due to thermal deterioration of the laminate. It is something.

In addition, warping and twisting occur in the laminated board, which poses a problem when producing printed circuits in a subsequent process.

■ Punching of circuit boards, drilling of holes, etc. are generally performed before circuits are formed, but contamination or any mechanical damage to the adhesive surface, which is susceptible during these processing steps, may inhibit the deposition of plating. In addition, it may cause fatal defects in the final wiring circuit.

■ Methods for applying adhesive onto laminates generally include methods such as a roll coater, a flow coater, a spray method, or a method in which a laminate is immersed in an adhesive bath to form a coating film. However, it is not always easy to apply the coating to a uniform thickness, and it is difficult to obtain a smooth surface condition after heat curing, which often results in a deterioration of the surface condition of the plated metal.

■ The method of applying adhesive onto the laminate is limited by the laminate itself; in other words, it is completely impossible to continuously apply adhesive to both sides of the laminate, which is manufactured in a fixed shape. Related to (■), depending on the above method, it is extremely difficult to obtain a surface defect-free coating surface, and bubbles are likely to occur, and residual bubbles in the coating film can be fatal to the plating circuit. In addition, defects generated during such a coating process render even a defect-free high-value laminate worthless, resulting in extremely large losses.

■ Since it requires two steps: manufacturing the laminate, and then applying adhesive to the laminate and curing it by heating, the manufacturing process is diverse and workability is poor.

■ In the method of laminating laminates under heat and pressure in advance and then forming an adhesive coating, dust adheres during the process and adversely affects the plating, resulting in restrictions on the work process.

In order to eliminate these many drawbacks in electroless plated printed circuit laminates, it has been proposed to simultaneously manufacture the laminate and form an adhesive film on the surface of the laminate.

That is, it is manufactured by laminating a predetermined number of laminate base materials (hereinafter referred to as impregnated base materials) made of paper, glass fiber, natural fiber, or synthetic fiber impregnated with a thermosetting resin and laminating them under heat and pressure. In the laminated board, one side of the adhesive film is protected with a releasable heat-resistant film, or an adhesive film is formed on the release film, and then heat-pressure lamination is performed to create a uniform and smooth metal plating. An adhesive-coated laminate whose surface is protected by a release film is obtained.

Pressing condition: 170℃, 90 minutes heating, 70kg/
There was no release film that could withstand pressures of crn2 or higher, so we investigated and found that a methylpentene polymer film was suitable (Japanese Patent Application No. 107611/1983), but this film had too good release properties and was cut to the specified size after pressing. When punching, it peels off very easily from the edges, and the above-mentioned problem (2) cannot be improved.

The present invention is a method for producing an adhesive-coated laminate using a release film that does not peel off naturally when cutting, but peels off smoothly when entering the plating process after going through various steps.

The present invention involves laminating a predetermined number of synthetic resin-impregnated substrates such as synthetic resin-impregnated paper or impregnated cloth with an adhesive film on one or both sides, and heating and pressing them to produce an adhesive-coated laminate. A methylpentene polymer film treated to have a wettability index of 33 to 42 dynes at 20° C. is used as a release film on the outside of the mold.

Methylpentene polymer is a polyolefin polymer based on 4-methylpentene-1, but the wetting index of the film surface obtained from it is about 30 dynes, and it easily peels off after pressing, making it difficult to use during the plating process of adhesive-coated laminates. It does not play the role of protecting the surface until it enters the room.

If the wetting index is less than 33 dynes, the improvement will be proportional to the wetting index, but peeling from the edges cannot be prevented.
When it exceeds 45 dynes, the adhesive force with the adhesive surface becomes strong, and it is preferable in terms of labor and workability when peeling off by hand.

When peeling off a release type film on 47 dyne, the film shows a broken state and cannot be peeled off cleanly at room temperature.

Note that conventional methods such as corona discharge treatment, ultraviolet irradiation, and electron beam irradiation are used to improve the wettability of the methylpentene polymer film.

Comparative Example 1 Palladium catalyst-containing nitrile rubber adhesive HA-04 (
Adhesive coated laminate adhesive made by Hitachi Chemical Co., Ltd.) 50μ
Methylpentene polymer film (Mitsui Petrochemical Industries ■
An adhesive film having a thickness of approximately 50 μm was prepared by coating and drying the adhesive film.

Resin impregnation rate 45 impregnated with epoxy resin solution VE-627N (for laminates containing palladium catalyst manufactured by Hitachi Chemical Co., Ltd.)
% by weight prepreg sheets and the two adhesive films with the methylpentene polymer film are stacked between the mirror plates with the adhesive portions on both outside sides,
Heating plate temperature 170℃, holding time 90 minutes, pressure cuff 0kg/C
Lamination was performed under heating conditions of rrL2.

When I tried to peel it off from the mirror plate with the release methylpentene polymer film attached, it peeled off from the edge between the adhesive and the film.

Further, when this was cut into a predetermined size using a shear, the film peeled off, and it was no longer useful for protecting the surface until the plating process.

The wetting index of this film was 30 dynes at 20°C.

Comparative Example 2 The film of Comparative Example 1 was subjected to a corona discharge treatment device for 25k.
When a laminated product using a wetting index of 32 was cut with a shear under a voltage of V, some peeling occurred and it was practically opaque.

In addition, the peelability of the film from the adhesive surface after work is very light, and the peeling strength in the 90° direction is 90 g/2
There were 5 friends.

Comparative Example 3 In Comparative Example 2, the voltage was set to 5.5 kV and the wetting index was 4.
7 was used.

Although the laminated product was cut to specified dimensions with a shear and holes were drilled with a drill, no peeling occurred at all, and the surface protection performance up to the plating process was very good.

However, the film was very difficult to peel after work, and the film was partially damaged, resulting in very poor workability.

The peel adhesive strength at this time was 170.9/25.

Example 1 In Comparative Example 2, when the voltage was set to 3.5 kV and the wetting index was set to 40, there was no peeling during cutting and drilling, and the film peelability after the work was also good.

The adhesive strength was 13M/25.

Example 2 In Comparative Example 2, when the voltage was set to 4.5 kV and the wetting index was set to 37, there was no peeling during cutting and drilling, and the film peelability after the work was good.The adhesive strength was 1509/
It was 25 mm.

The adhesive-coated laminate for electroless plated printed circuits obtained by the present invention has the following advantages.

■ During hot-pressure lamination of laminates, the curing reaction of the adhesive and the curing reaction of the impregnated paper resin are performed simultaneously to produce adhesive-coated laminates, so this method involves applying adhesive to the thermoset laminate and curing it by heating. Compared to conventional methods, there is no heating process for the laminate, and therefore there is no thermal deterioration of the laminate itself, making punching and hole machining easier, and the manufacturing process can be shortened.Also, the adhesive film can be formed continuously. Moreover, the bond between the laminate base material and the adhesive is strong.

- Since the adhesive coating surface of the laminate is protected by a releasable film, the coating surface can be sufficiently protected until immediately before processing such as circuit printing or resist coating.

Therefore, the coating film is not contaminated during the punching process, and a defect-free plating circuit can be obtained.

In addition, the laminate will not suffer mechanical damage during long-term oral use or transportation after manufacturing.

■ Since the adhesive coating is pressed with a mirror plate, the coating surface is completely uniform and smooth without bubbles or unevenness, resulting in an excellent plating finish.

Claims (1)

[Claims] 1. A predetermined number of synthetic resin-impregnated base materials are stacked, and an adhesive film is further stacked on one or both sides of the base material before addition. A method for producing an adhesive-coated laminate by hot pressing, characterized in that a methylpentene polymer film treated to have a wettability index of 33 to 42 dynes at 20°C is used as a release film on the outside of the adhesive film. A method for producing an adhesive-coated laminate.