JPS58165392A - Substrate for printed circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printed circuit board having excellent heat dissipation properties, electrical insulation properties, heat resistance, etc.

BACKGROUND OF THE INVENTION As electronic devices become smaller and thinner, there is a growing trend toward higher density mounting of components on printed wiring boards.

For this reason, there are stricter requirements than ever before regarding properties such as heat dissipation and dimensional stability, and heat dissipation becomes a problem especially when high-density packaging is performed.

Conventionally, a heat dissipating substrate based on a metal plate is known, in which a synthetic resin layer is provided on the surface of an A/plate, etc., and an inorganic filler with good thermal conductivity is dispersed in the layer. However, this structure has the disadvantage that when the resin layer is thin, the withstand voltage is insufficient, and when the resin layer is thick, heat dissipation and dimensional stability deteriorate.

There are also cases in which a glass cloth is bonded onto the A/plate etc. using a thermosetting resin, in which case inorganic filler powder may be used in combination with the glass cloth.

These have better dimensional stability than the above-mentioned ones, but since glass cloth is woven from long fiber bundles, air and solvent may be trapped in the fiber bundles when the thermosetting resin is applied to it. However, it is not possible to remove all the air and solvent during the process of adhering to the AJ board, resulting in incomplete electrical insulation, which increases the frequency of defective products. Therefore, there are methods that try to solve the insulation problem by combining two adhesive layers or by increasing the amount of thermosetting resin attached.
This is not desirable from the standpoint of thermal conductivity.

If the electrical insulation is to be completely maintained, it is also possible to fabricate the insulating layer by using a thermoplastic resin film and bonding it under heat and pressure. However, although this has good insulation properties, it has poor heat resistance, and the adhesive layer deteriorates and breaks during the component mounting process (soldering process, bonding process, etc.) and high-temperature processing process after printed circuit board processing. In this case, if a heat-resistant thermosetting film is used instead of the thermoplastic resin film, the problem of deterioration of the adhesive layer will be eliminated, but since it is only possible to bond with heat and pressure, the base metal plate and the printed circuit are attached to both sides of the film. It is necessary to provide a thermosetting resin layer for adhering the metal foil. In actual industrial production, in order to increase productivity, it is necessary to manufacture something quite large.
The resin layer must be bonded so that there is no non-adhesive layer in all of them.

A certain level of thickness is required. The result is poor thermal conductivity.

The present invention has been made in view of these circumstances, and its purpose is to provide a printed circuit board with excellent heat dissipation, electrical insulation, and heat resistance.

For these purposes, in the present invention, an inorganic filler with good thermal conductivity is included in the synthetic resin layer provided on the metal plate, and a heat-resistant resin film is interposed to provide complete electrical insulation. .

Hereinafter, the present invention will be described in detail with reference to the drawings, which are examples of the present invention.

1 and 2 are cross-sectional views of a substrate according to the present invention.

In the figure, 1 is a metal plate, 2.3 is a synthetic resin layer containing an inorganic filler 21.31. 4 is a heat-resistant resin film, and 5 is a metal foil.

Metal plate 1 is AI! , Cu, Fe, etc. and alloys containing these can be used.
1 Al is most suitable for practical use. The thickness of the metal plate is determined by Kawaguchi's specifications, but it is generally between 0.5 and 25 mm. The surface of the metal plate is preferably roughened to improve adhesion to the resin layer, but depending on the type of metal plate G, the surface may not be roughened. Surface roughening is maximum surface roughness Rm
ax ) is suitably in the range of 5μ to 40μ. The surface roughening method may be a mechanical method or a chemical method.

As the resin for the synthetic resin layer 2, thermosetting resins such as epoxy, phenol, polyimide, unsaturated polyester, and BT resin are preferred, but thermoplastic and heat-resistant modified polyethylene, polysulfonic acid, polyphenylene sulfide, etc. can also be used. be.

This resin layer 2 contains an inorganic filler 21. Inorganic fillers include kl, OB, 5i02,
ZrO2.

Metal oxides such as TiO, , BeO, BN, Si3N4
゜1? In addition to inorganic fibers such as nitrides such as N, carbides such as Si, C, Tic, and ZrC, nonwoven short glass fibers, and mineral fibers, the purpose of the inorganic fillers used here is to increase thermal conductivity. The electrical insulation properties are provided by the heat-resistant resin film described below, so Fe, A/+Ni, Cu
It is also possible to use powders of metals or alloys such as , Ag, carbon powders, nonwoven short metal fibers, carbon fibers, etc., and the inorganic filler shown in FIG. 21 in the present invention includes these.

In addition, in order to improve the adhesion of inorganic fillers to resins and improve the moisture resistance of printed circuit boards, surface treatment can be performed and mixed into resins. You can also get it by putting .

When the inorganic filler is a granular powder, it is preferably 30 μm or less. Since powder usually has a particle size distribution, 30μ or less in this case usually means that 90% or more of the entire particles are 30μ or less. If the thickness exceeds 30μ, the resin layer becomes thick, the heat dissipation effect is reduced, and the bonding work becomes difficult. However, aluminum powder may form flakes, and flakes overlap in layers in the resin, so
Large ones exceeding 30μ can also be used.

The mixing ratio of the resin and the inorganic filler is determined by the effect of heat dissipation and the workability of bonding, but the appropriate volume ratio is in the range of 10 to 300 parts of the inorganic filler to 100 parts of the resin.

If the amount of the inorganic filler is less than this range, the heat dissipation property will not be significantly improved, and if it exceeds this range, the bonding operation will be poor and sufficient adhesive strength will not be obtained.

The thickness of the synthetic resin layer 2 containing an inorganic filler is suitably in the range of 10 to 60 μm, taking into account bonding strength, heat dissipation, workability, etc.

A heat-resistant resin film is adhered onto the synthetic resin layer 2. When mounting components on a board, a soldering process is usually involved, so this film needs to be able to withstand that temperature. Printed circuits also become quite hot during use, depending on their purpose. For these reasons, the resin film is preferably a heat-resistant film made of polyimide, polyparabanic acid, or the like. However, low-temperature soldering has been developed, and printed circuits may not reach very high temperatures depending on the purpose of use, so in such cases, polyester:・□,
.

Films such as thermoplastic films can be used.

The thickness of the film is preferably as thin as possible without generating voids and maintaining a withstand voltage; however, since there are manufacturing problems, a range of 10 to 30 μm is generally suitable.

Further on the film is a resin layer 3 containing an inorganic filler 31.
Glue. Since a printed circuit is provided in this layer, insulation between the wirings, that is, insulation of the surface layer of the resin layer 3 in FIG. 1 is required. For this reason, electrically conductive materials such as metals, carbon, carbides, etc. cannot be used as the inorganic fillers used here.

The other inorganic fillers, their blending amounts, the thickness of the resin layer, etc. may be almost the same as in case 2 above. As for the type of resin, it is preferable to select one that easily roughens the surface. Since printed circuits are generally assembled on the board shown in Figure 1 by electroless plating, etc., it is necessary to roughen the resin surface by chemical methods to improve the adhesion between the plated metal and the resin. Because there is. :1';・-, :,.

What is shown in Figure 2 is 1. , a metal foil 5 is adhered to the vocal fat layer 3, and can be used as is for □″1]-foot wiring processing.The metal foil can be made of commonly used copper, aluminum,
Made of nickel or the like, the thickness is in the order of 0.005 to 0.3.

A substrate with the structure shown in Figure 2 can be created by, for example, applying a resin solution containing an inorganic filler to both sides of a film, bonding a metal plate and metal foil to this, thermo-compression bonding, and curing the resin. can be produced.

In the case of the film shown in FIG. 1, a metal plate may be adhered to one side of the film in the same manner as described above, and a resin liquid may be applied to the other side and cured.

Finally, the surface is roughened by treatment with a chemical solution or the like.

Although the illustrated example shows an insulating layer provided on one side of the metal plate, it is also possible to provide the insulating layer on both sides in the same way.

The printed circuit board according to the present invention sandwiches a film with good electrical insulation properties and contains an inorganic filler with good thermal conductivity on both sides, so it not only has excellent withstand voltage but also has high heat dissipation. It is particularly suitable for applications where this characteristic is important.

In addition, the use of a film as an adhesive layer according to the present invention makes it possible to easily create an external shape by drawing the printed circuit board itself as calculators and the like become thinner, and when glass cloth is used as an adhesive layer. Compared to this, it is possible to create a part of the corner with an acute angle. Also, no electrical leakage occurs in that part.

This also means that the printed circuit board can be used not only as a flat board but also as a curved board or bent.

Next, in order to clarify aspects of the present invention, examples and comparative examples will be shown and explained. The embodiment shown here is just one example, and does not limit the scope of the present invention.

Example 1 The following epoxy resin varnish (formulation example 1) had an average particle size of 4μ.
, 1 α-alumina (A1203) with a total size of 25μ or less
Add 00% by weight and stir well to add methyl ethyl ketone (ME
K) was mixed in to adjust the viscosity to a specified level, and coated on both sides of a 25μ thick polyimide film to a thickness of 40μ.
A semi-cured double-sided adhesive sheet was prepared by heating and drying at 0°C. On the other hand, one surface of a 211+1L thick aluminum plate is treated with hydrochloric acid to activate it, the above-mentioned sheet is placed on that surface, and then a 35μ thick copper foil is further layered for approximately 160mm.
A copper-clad aluminum-based board was produced by heat-pressure bonding at about 40 kg and 10 n2.

Resin varnish formulation (formulation example 1) (1) Epoxy resin (AER-661L, tIJM Kankoku Ichisei) 100 parts\mi/ (2) Dicyandiadad 4 parts (3)
Dimethylformamide 20 parts (4) Benzyldimethylamine 03 parts (5) Methyl ethyl ketone 100 parts Example 2 α-Alumina (AI
! 203) with a silane coupling agent, and added 100 wt.
In addition, stir well and mix methyl ethyl ketone (MEK) to adjust the viscosity to a predetermined value, and form a polyparabanic acid film with a thickness of 25 μm and a thickness of 50 μm on both sides.

It was coated and dried under heat for 16 o's (t) to produce a semi-cured double-sided adhesive cutting material sheet.

On the other hand, one surface of the 2-thickness aluminum plate was activated by blasting, and the above-mentioned sheet was applied to that surface for about 40k at 60℃.
An aluminum base aluminum clad plate was produced by thermocompression bonding at g/cm2.

Example 3 Add 100% by weight of BN (boron nitride) with an average particle size of 4μ and a total of 30μ or less to the following solvent-free epoxy varnish (Blend Example 2), stir well, and keep the temperature of the resin constant during coating. Adjust viscosity.

A polyimide film with a thickness of 25μ is passed through this to a thickness of 40μ.
An adhesive layer was prepared on both sides, and the surface was activated with hydrochloric acid2.
A copper foil with a thickness of 35 μm was placed on an aluminum plate with a thickness of W011 and heated and pressed with a heated roll to produce an aluminum-based copper-clad plate.

Resin varnish (formulation example 2) (1) Epoxy toe (Ehikron 850, manufactured by Dainippon Ink ■) /:): □:,, 100 parts (2) Hardening agent (HN-2200, manufactured by Hitachi Chemical ■) 79 Part (2 parts 4
Example 4 The following unsaturated polyester resin varnish (formulation example 3) was coated with α-alumina (AJ2os
) and 50% by weight of silica (SiO□) whose average particle size is 10μ or less overall is added and stirred well to form a polyimide film with a thickness of 25μ and -40μ on both sides.
Create an adhesive layer. A7 whose surface was activated with hydrochloric acid and an alumite layer of 9μ was added? The above-mentioned sheet was placed on the plate, and a 40 μm Nitsutsu foil was further layered and bonded under heat and pressure at about 160° C. and io kg/cm 2 to produce an aluminum-based nickel-clad plate.

Resin varnish (formulation example 3) (2) Tertiary butyl perbenzoate
1 Part Example 5 30 parts of acrylonitrile rubber (trade name Hiker 1072) is added to the epoxy resin varnish of Formulation Example 1 to prepare a varnish for electroless plating.

To this, 100 parts by weight of α-alumina (AI! 203) with an average particle size of 4μ was added and stirred, and then MEK (Methi!#=2 ethyl ketone) was added and a 30μ thick polyimide film was coated on one side of the 25μ thick polyimide film as a predetermined quarantine. The film was coated in a uniform pattern, dried by heating at 130°C, and a release film was applied to temporarily attach a polypropylene film.

In addition, an average of 40μ of A in the epoxy resin varnish of Formulation Example 1
I! Add 80% by weight of powder, stir well, coat on the opposite side of the polyimide film to a thickness of 50μ, and heat at 160°C.
to create a semi-cured adhesive layer.

On the other hand, one surface of a 2cm thick aluminum plate was treated with hydrochloric acid to activate it, and the above-mentioned sheet was placed on top of it and heat-pressed to create an insulating layer on the aluminum plate. An aluminum base substrate for the process was fabricated.

Comparative Example 1 The epoxy resin varnish of Formulation Example 1 was adjusted to an appropriate viscosity with methyl ethyl ketone, and glass cloth (WE-1 manufactured by Nittobo 1) was prepared.
0GBZ-2) and heat-dried at about 160° C. to produce a semi-cured sheet with a thickness of 110 μm. On the other hand, one surface of an aluminum plate with a thickness of 2 fins was treated with hydrochloric acid to activate it, and the above-mentioned sheet was layered on top of it, and the thickness was further increased to 35 mm.
An aluminum-based copper clad board was produced by stacking copper foils of .mu. and bonding them under heat and pressure at about 160.degree. C. and about 40 kg/cm.sup.2.

Comparative Example 2 The epoxy resin varnish of Formulation Example 1 was applied to both sides of a polyimide film with a thickness of 25 μm to a thickness of 40 μm, and the film was heated and dried at 160° C. to produce a sheet having an adhesive layer in a semi-cured state. On the other hand, one surface of an aluminum plate with a thickness of 15 mm was treated with hydrochloric acid to activate it, and the above-mentioned sheet was layered on top of it, and a copper foil with a thickness of 70 μ was layered at about 160°C, about 40 ky/lv'.
A copper clad plate with an aluminum base was made by bonding with heat and pressure.

Comparative Example 3 Polyethylene film 50μ activated with hydrochloric acid 1,
Place it on a 5 m thick aluminum plate and place it on top of the 17 m thick aluminum plate.
Copper foils with a thickness of 35 μm were stacked and melted and bonded using a hot pressure roll to produce an aluminum-based copper-clad board.

Comparative Example 4 100% by weight of α-alumina (AI!20s) with an average particle size of 4μ was added to the epoxy resin varnish of Formulation Example 1, stirred well, and coated on a 35μ thick copper foil surface to a thickness of 80μ. An adhesive layer was prepared, placed on an aluminum plate with a thickness of 1.5 times and activated with hydrochloric acid, and bonded under heat with a heating roll to produce an aluminum-based copper-clad plate.

Test Results Table 1 shows the results of testing each characteristic of the above Examples and Comparative Examples.

:1:□ １□□ Chapter 1 Table The test method was based on JIS C-6481.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of the printed circuit board of the present invention. 1...metal plate, 2. :(...Resin layer containing inorganic filler, 21.31...Inorganic filler, 4...Heat-resistant resin-Noia [)1.5...Metal foil. Special 7i' [Applicant Showa Denko Co., Ltd. r1 Nitzkan Kogyo Co., Ltd. r1 = Agent Sei Kikuchi, patent attorney

Claims (2)

[Claims] (1) A printed circuit board in which a synthetic resin layer containing an inorganic filler is provided on at least one surface of a metal plate, in which a heat-resistant resin film is interposed in the middle of the synthetic resin layer. (2) In a printed circuit board in which metal foil is attached to at least one surface of a metal plate via a synthetic resin layer containing an inorganic filler, a heat-resistant resin film is interposed in the middle of the synthetic resin layer. Printed circuit board