JPS5819155B2 - Method for manufacturing a substrate for printed wiring board using metal material as a base and having through holes - Google Patents

Description

[Detailed description of the invention] The present invention is for a printed wiring board having a metal material as a base.

The present invention relates to a method of manufacturing a substrate, and more particularly, to a method of coating and forming a resin layer on a flat surface of a metal material substrate having through holes without causing clogging of the through holes.

Physical requirements for wiring boards are increasing as electronic devices become more densely packed.
For example, since conventional wiring boards based on organic materials cannot fully satisfy the requirements for heat diffusion and heat dissipation ability or the ability to mount a large number of heavy components, there is a trend toward wiring boards based on metal materials.

However, forming an insulating layer is an important issue in these metal-core wiring boards, and when forming an insulating layer on the flat surface of a metal material substrate that has through holes, it is necessary to prevent the through holes from clogging. be.

Conventionally, for this purpose, a method has been tried in which a resin coating is prepared on a removable film in advance, holes are drilled in the same manner as through-holes in the substrate, and then the film is bonded to a substrate wiring board.

However, there are unavoidable drawbacks such as a decrease in the reliability of the circuit due to the difficulty in aligning the through-holes, and resin inflow into the through-holes during hot-pressure bonding.

The present invention has been made in view of these drawbacks, and provides a method for coating and forming a resin layer such as an insulating layer on a flat surface of a metal material substrate having through holes without clogging the through holes. While supplying a resin solution having a viscosity of 400 centivoise or more in the form of a film to the flat part of a metal material substrate for printed wiring boards having The glaze is characterized by including an upper glaze that is moved at a faster speed to coat and form a resin solution film on the flat surface of the substrate.

□ Suitable methods for this method include the curtain flow method (hereinafter abbreviated as C, F method), top reverse roll coater method (abbreviated as CT and R), etc., which will be specifically explained below.

The eF method is a coating method in which a resin solution film is dropped vertically through slits at regular intervals, and the object to be coated is moved horizontally and perpendicularly past the falling film. By increasing the moving speed of the object to be coated, the coated film is stretched and a corresponding shrinkage force is generated.

If the object to be coated is a smooth plate-like object with no through holes on the lip surface, even this shrinkage force will not destroy the originally coated area due to surface chemical wetting of the coating film to the object, and the edges will However, when there is a through hole, the solution film coated on the through hole is interrupted by shrinkage force at the same time as it is applied because there is no support, and the surface tension of the coating film also acts at the same time, causing it to move away from the position of the through hole. Move toward the surrounding flat surface.

In this case, the viscosity of the resin solution is 4-; in order to prevent the interrupted solution film from flowing into the through hole and causing clogging;
A minimum of 400 centimeters is required.

The TR method, which is widely used as a method for coating other films, is also realized by adjusting the feed speed ratio of the object to be coated, which is determined by the speed of the coating roll and the speed of the backup roll.

With the current electroless copper plating technology, a technology capable of directly forming an insulating layer printed circuit as described above is not yet common.

That is, since the insulating layer alone is not sufficient to impart high adhesive strength and heat resistance, it is necessary to further provide an adhesive layer on the insulating layer.

Such a case can be solved by forming an adhesive layer on the insulating layer using the method of the present invention to further increase the adhesive strength with the electroless steel plating layer.

A resin layer having insulation properties and acting as an adhesive to the electroless copper plating layer can also be formed by coating directly on the flat surface of the metal substrate by the method of the present invention.

Although the steps of insulating the inner wall of the through hole, adhesion + (tJ coating, etc.) are carried out as appropriate, the step of forming a resin layer such as an insulating layer, an adhesive layer, etc. on the flat surface of the metal material substrate having the through hole according to the present invention It may be done before or after steps such as insulation and adhesive application.

The drawing is a cross-sectional view showing a state in which a resin according to the present invention is applied and formed on a flat surface of a metal material substrate having through holes, and FIG. Figure 2 shows that a resin layer 4'' with similar insulating properties and adhesive properties is formed on the flat surface of a metal substrate on which a resin layer 4'', which has both insulation and adhesive properties, has been previously formed on the inner wall of the through-hole. A resin layer 5 that acts as an adhesive is formed by coating.

The metal material base and binding used in the present invention include iron, aluminum, and alloys mainly composed of these materials, and the plate thickness is 0.5 to 5 m.The inner diameter of the IL1 through hole is Q, 8. m~5
It's mine.

As the insulating layer, epoxy resin, phenol resin, polyester resin, polyacid resin, polyamide oxide resin, polyacid resin, urea resin, melamine resin, vinyl chloride, fluororesin, polyacrylic acid ester resin,
For the adhesive layer, one type or mixture of polymethacrylic acid ester resins, etc. may be NBR, SBR, chloroprene,
A type of synthetic rubber such as chlorosulfonated polyethylene, natural rubber, rubber/phenolic resin, rubber/epoxy resin, polyacetylene phenol resin, epoxy resin, etc.
As the resin layer, the mixture of which has an insulating property and at the same time functions as an adhesive, epoxy resins, rubber/phenolic resins, and mixtures of epoxy resins/rubbers are used.

Incidentally, fillers such as calcium carbonate, silica, zinc white, titanium oxide, zirconium silicate, and Kurji may be mixed into the above-mentioned insulating layer, adhesive layer, and resin layer having the characteristics of both.

As a solvent, methyl ethyl ketone, acetone, 1 methyl isobutyl ketone, toluene, xylene, methanol, ethanol, inpropatol, methyl cellosolve,
One or several mixed solvents such as ethyl cellosolve, ethyl acetate, and dimethylformamide are used.

Example 1 A 60% methyl enal ketone solution of an epoxy resin (Epicoat 1001 manufactured by Shell Chemical Co., Ltd. and a curing agent) was added with
Equivalent weights of the 0-factor methyl ethyl ketone solution were mixed, and the mixture was further adjusted to about 650 centivoise using cellosolve acetate.

Next, using a Fronicoater manufactured by West German Vinyl 21,
Set the slit width of the discharge die to 0.9 mwt,
The solution was passed through a membrane.

The falling speed of the solution at this time was approximately 70 M/min.

1.0φ, 1.5φ, and 2.0φ in this fluid coating film.
1.2mmt with 4 types of through holes each with 100 holes
The iron substrate is passed through at a conveyor speed of 125M/min.
A resin coating film was formed on the surface of the substrate.

In this case, there was no clogging in each through hole due to inflow of resin, and the coating film thickness on the flat surface after drying was about 35 μm.

A resin coating film was also formed on the back surface of the substrate in the same manner.

In addition, to form a coating film inside the through hole, the pre-crystalline membrane was further diluted with methyl ethyl ketone and immersed in a solution adjusted to 6 centimeter voids, then pulled up at a speed of 200 mm/min in the direction perpendicular to the through hole wall, and air-dried. A coating film was formed.

When these resin insulating layers were heated and cured, the dielectric breakdown voltage was measured to be 2 KV or more.

Note that when a printed circuit is created using an electroless copper plating method on a board with only these insulating resin layers, sufficient adhesion of the circuit cannot be obtained, so a printed circuit with atarylonitrile book diene rubber and phenolic resin as the main components is used. Adhesive 8
% methyl ethyl ketone solution (viscosity 8 centivoise) and 2
Using a 5% methyl ethyl ketone solution (viscosity: 800 centivoise), an adhesive layer was provided in the through holes and on the insulating layer on the flat surface in the same manner as described above.

The thickness of the adhesive on the through-hole and inner wall was approximately 25 μm, and on the flat surface, curtain flow coating was applied twice to obtain a coating thickness of approximately 50 μm.

Next, a printed wiring circuit was created based on the known electroless steel plating method, and the adhesive strength of the circuit maintained a peel strength of 1.8 kg/cIfL or higher in all parts, and the through-hole pull-out strength was 5 kg or more, 2
No abnormal changes were observed even after being left on a 60°C solder bath for 30 seconds or more.

Example 2 After forming an epoxy resin electrodeposition coating film on iron substrates 1 and 2 with holes of 1.0φ to 3.0φ processed by electrophoresis, (film thickness 100 to 180μ) Example The adhesive solution used in Example 1 was immersed in a diluted solution of 6.5 centimeter voids, pulled up, air-dried, and heated to dry. This process was repeated twice to form an adhesive layer on the inner wall of the through hole. 1,,i,4. , the adhesive solution used was mixed with cellosolve acetate/toluene 1. The solution was adjusted to 800 centivoid with a mixed solvent of 1000 ml, and the solution was heated using a flow coater with a slit width Q of g mm t.

The solution falling speed at this time was approximately 50 M/min.

Conveyor speed 10, O, M/
The substrate surface 1 (dry coating thickness 3
．． A 5'μ adhesive layer was formed.

This 1. In this case, the dielectric breakdown voltage was within the range of Oe IKV, but the adhesion properties of the electroless copper plating printed circuit had a peel strength of 1.8 kg/crrL and 260℃ soldering heat resistance of 30.
It was possible to maintain more than a second.

As explained above, according to the present invention, a resin layer such as an insulating layer or an adhesive layer is coated on a flat surface of a metal material substrate for a printed wiring board having a large number of through holes without clogging the through holes. Can be formed.

[Brief explanation of drawings]

The drawings are cross-sectional views showing the state in which a resin layer is formed on the flat surface of a metal substrate according to the present invention. A case is shown in which a similar resin layer is further formed on the flat surface portion of the metal material substrate on which the resin layer having the properties is formed. Explanation of symbols, 1...Metal material substrate, 2...
...Through hole, Total...Insulating layer, 4...
A resin layer having both insulation and adhesive properties formed on the inner wall of the through hole, 5... A resin layer having both insulation and adhesive properties formed on the flat surface.

Claims (1)

[Claims] 1. While supplying a resin solution with a viscosity of 400 centivoise or higher in the form of a film to the flat part of a metal material substrate for printed wiring boards having through holes, apply the resin solution film to the flat part of the substrate. A method for manufacturing a substrate for a printed wiring board having through holes, the substrate being made of a metal material, comprising the step of applying and forming a resin solution film on a flat surface of the substrate by moving the film at a speed higher than the film supply speed.