JPS58165391A - 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.In addition to heat dissipation being an issue especially in high-density packaging, depending on the purpose of use, there are particular demands on the moisture resistance and smoothness of the board surface. Excellence is required. This is because if the moisture resistance is poor, moisture adsorbed on the surface of the insulating layer between the parts mounted on the board lowers the insulation resistance between the parts.

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.

Further, in the surface portion of the resin layer, the interface between the inorganic filler and the resin is easily affected by moisture, which causes a decrease in electrical resistance. For this reason, fillers are also treated to make them waterproof, but even this is not sufficient.

AI again! There are also cases in which glass cloth is adhered to a plate or the like using a thermosetting resin, and in this case, inorganic filler powder is also used in combination with the glass cloth.

These have better dimensional stability than the above-mentioned ones, but since glass cloth is made by weaving long fiber bundles, air and solvent may get trapped inside the fiber bundles when the thermosetting resin is applied to it. A: All the air and solvent cannot be removed during the bonding process to the 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.) after printed circuit board processing (soldering process, bonding process, etc.) and high temperature processing process. do. In this case, if a heat-resistant thermosetting resin film is used instead of the thermoplastic resin film, the problem of deterioration of the adhesive layer will be eliminated, but since thermo-pressure bonding is not possible, both sides of the film It is necessary to provide a thermosetting resin layer for adhering the pace metal plate and the printed circuit metal foil. In actual industrial production, it is necessary to fabricate a fairly large product in order to increase productivity, and the resin layer needs to be thicker than a certain level in order to adhere to it so that there is no non-adhesive layer on all surfaces. Become. The result is poor thermal conductivity.

The present invention was made in view of the above circumstances, and its purpose is to provide a printed circuit board that not only has good heat dissipation and heat resistance, but also has particularly high moisture resistance and excellent electrical insulation. There is a particular thing.

For this purpose, the substrate of the present invention has a structure in which a synthetic resin layer containing an inorganic filler, a heat-resistant resin film layer, and a synthetic resin layer are sequentially laminated on at least one surface of a metal plate.

death The following is an example of the present invention with reference to the drawings. The present invention will now be described in detail.

Figure 1 and Figure 2 are cross-sectional views of the substrate according to the present invention. It is a resin film, on which a synthetic resin layer 3 is provided. 5 is a metal foil.

The metal plate 1 can be made of KL, Cu, Fe, etc., or alloys containing these, but AJ? is most suitable in practice. The thickness of the metal plate is determined depending on the purpose of use, but is generally between 05 and 25 mm.

The surface of the metal plate is preferably roughened in order to improve adhesion with the resin layer, but depending on the type of metal plate, the surface may not be roughened. Surface roughening is maximum surface roughness Rm
a x ) is suitably in the range of 5 μ to 40 μ. 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 preferable, but thermoplastic and heat-resistant modified polyethylene, polysulfonic acid, polyenylene sulfide, etc. can be used. It is possible.

This resin layer 2 contains an inorganic filler 21. Use it as an inorganic filler AI! 203.5i02, ZrO2
゜Metal oxides such as TiC2, BeO, BN, Si3N4
゜In addition to inorganic fibers such as nitrides such as AJN, carbides such as SiC, TiC, and ZrC, nonwoven short glass fibers, and mineral fibers, the purpose of the inorganic fillers used here is to increase thermal conductivity. Since electrical insulation is provided by the heat-resistant resin film described below, Fe is used.

Powder of metals or alloys such as AJ, Ni, Cu, Ag, etc.
Carbon powder, nonwoven short metal fibers, carbon fibers, etc. can also be used, 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 the powder usually has a particle size distribution, 30μ or less in this case usually means that 90% or more of the entire frame consists of 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 inorganic filler is less than this range, adhesive strength cannot 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 consideration bonding strength, heat dissipation, workability, etc. A good resin film...
;1. Glued. The film needs to be able to withstand the heat, as printed circuit boards usually involve a soldering process when mounting components.Printed circuits also become quite hot during use, depending on their purpose. Therefore, it is desirable to use a heat-resistant resin film made of polyimide, poly/cyanocitric acid, etc.However, low-temperature soldering has been developed for soldering, and printed circuits may not reach very high temperatures depending on the purpose of use, so such In such cases, thermoplastic films such as polyester films can also 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.

A resin layer 3 is provided on the film.

This layer needs to be thick to a certain extent in order not to reduce the adhesive strength with the metal foil or metal plating that is bonded on top of it, but it contains materials with good thermal conductivity such as inorganic fillers. Because it is too thick, it inhibits thermal conductivity. resin layer from these points.

The appropriate thickness is 7 to 40 μm. Moreover, since the resin layer does not contain a filler, its moisture resistance is extremely good.

The type of resin for the resin layer 3 is not particularly limited as long as it is heat resistant when the substrate is configured with a metal foil 5 bonded in advance as shown in FIG. For example, epoxy, phenol, polyimide, unsaturated polyester, BT
Resin such as resin can be used. When the circuit board is constructed as shown in FIG. 1 and a circuit is constructed by plating or the like on the resin layer 3, it is necessary that the plating metal and the resin have good adhesion. A roughening treatment is usually performed on the surface of this resin layer. It is preferable to select a type of resin that can be easily subjected to surface roughening treatment.

The one shown in FIG. 2 has a metal foil 5 bonded to a resin layer 3, and can be used as is for printed wiring processing.

The metal foil is made of commonly used copper, aluminum, nickel, tin, etc. and has a thickness of 0.005 to 0.3 mm.

A substrate with such a structure is made by, for example, applying a resin liquid containing an inorganic filler to one side of a film, bonding it to a metal plate, then applying a resin liquid to the film surface, and bonding a metal foil. It can be manufactured by thermocompression bonding and curing the resin.

In the case shown in FIG. 1, a metal plate is adhered to one side of the film in the same manner as described above, a resin liquid is applied to the other side, and these are cured and integrated. Finally, the surface of the resin layer is treated with a chemical solution or the like to roughen the surface and produce a product.

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 uses a film with good electrical insulation properties, so it has a high withstand voltage, and since there is a filler with good thermal conductivity between the film and the metal plate,
The substrate of the present invention has improved heat dissipation properties, and since the resin layer on the top surface of the film does not contain a filler, it has high moisture resistance, and the substrate of the present invention is particularly suitable for applications where moisture resistance is required. be.

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 embossing the printed circuit board itself as calculators and the like become thinner, and when glass cloth is used as an adhesive layer. Compared to the above, a part of the structure can be made at an acute angle, and electrical leakage does not occur at 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) was coated on one side of a 25μ thick polyimide film to a thickness of 25μ, heated and dried at 160°C, and laminated to a thickness of 3μ by a laminating machine.
Attach 5μ copper foil. Further, 100% by weight of α-alumina (A/203) having an average particle size of 4μ or less than 15μ is added to the epoxy resin varnish of Formulation Example 1 and stirred well, so that a thickness of 4'0μ is formed on the opposite side of the polyimide film. For transfer 1:・ Coat and dry by heating at 160℃ to semi-cure■11
1. An adhesive layer in a state of 1 is prepared. One surface of a 2-inch thick aluminum plate was activated by treatment with hydrochloric acid, and the above-mentioned sheet was bonded to that surface using a heating bonding machine to produce an aluminum-based copper-clad plate.

Resin varnish formulation (formulation example 1) (1) Epoxy resin (AER-661L, made by chemical-free ■)
100 parts (2) dicyandiamide
Part 4 (3) Dimethylformamide
20 parts (4) benzyldimethylamine
03 parts (5) Methyl ethyl ketone
100 copies Example 2゜The following unsaturated polyester resin varnish (formulation example 2) was coated on one side of a 25μ thick polyimide film to a thickness of 2゛0μ, heated and dried at 160℃, and laminated using a laminating machine. Copper foil with a thickness of 70μ is pasted together. In winter, the overall average particle size of 8 μ in the unsaturated polyester resin varnish of Formulation Example 2 is 25 μ or less 1111 0′□>+ and 2. Buto (BN) t-30 weight 11 silica (SiO□) whose average particle size is 6μ or less is 1
00% by weight was added, stirred well, and coated on the reverse side of the aforementioned polyimide film by transfer to a thickness of 40μ at 160°C.
Heat and dry to create a semi-cured adhesive layer.

On the other hand, one surface of a 1.5-inch thick aluminum plate was sandblasted to create an uneven surface with a depth of 15 μm, and the above-mentioned sheet was placed on that surface and bonded under heat and pressure at about 160°C and about 40 kg/cm2. An aluminum-based copper clad plate was fabricated.

Resin varnish formulation (formulation example 2) (1) Unsaturated polyester resin (Polymer, 1
oog Add 100% by weight of α-alumina (A12%) with an average particle size of 8μ or less and 25μ or less into a solvent-free epoxy varnish, stir well, and apply an adhesive layer with a thickness of 40μ on the opposite side of the polyparabanic acid film. was activated with hydrochloric acid, and then an alumite layer of 9 μm was attached onto an Af plate plate, which was drawn out and hot-pressed using a heated roll, to produce an aluminum-based plate.

Resin varnish formulation (formulation example 3) (1) Epoxy resin (Evicron 850.
100 parts (manufactured by Dainippon Ink ■) (2) Hardening agent (HN-2200 manufactured by Yutatsuka Niku Co., Ltd.) 7
9 parts (3) Hardening accelerator (2E4 [manufactured by Shikoku Kakei Co., Ltd.] 0.
5 Parts Example 4 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.

MEK (methyl ethyl ketone) was further added to this to give a predetermined viscosity, and the film was coated to a thickness of 15μ on one side of a 25μ thick polyimide film, dried by heating at 130°C, and a polypropylene film was temporarily attached as a release film. match.

Further, 80% by weight of A/powder having an average thickness of 10μ was added to the epoxy resin varnish of Formulation Example 1, stirred well, and coated on the opposite side of the polyimide film to a thickness of 50μ.
Heating at ℃ produces a semi-cured adhesive layer.

On the other hand, one surface of an aluminum plate with a thickness of 2f + tlll was treated with hydrochloric acid to activate it, the above-mentioned sheet was placed on top of it, and hot pressing was performed 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-10 manufactured by Nittobo Co., Ltd.) was prepared.
0BZ-2) and heated and dried at about 160 DEG C. to produce a semi-curic acid historical sheet having a thickness of 110 .mu.m. On the other hand, one surface of a 2cm thick aluminum plate was treated with hydrochloric acid to activate it, the above-mentioned sheet was placed on top of it, and a 35mm thick copper foil was placed on top of it. An aluminum base copper clad plate was produced by adhering it.

Comparative Example 2 The epoxy resin varnish of Formulation Example 1 was coated on both sides of a 25μ thick polyimide film to a thickness of 40μ, and heated at 160°C.
A sheet with an adhesive layer in a semi-cured state was produced by heating and drying the adhesive layer.

On the other hand, one surface of a 1.5-thick aluminum plate was treated with hydrochloric acid to activate it, and then the above-mentioned sheet was layered on top of it, followed by a copper foil with a thickness of 70/j and heated at about 160℃ and heated at about 40 kg/cm2. This was adhered to produce an aluminum-based copper clad board.

Comparative Example 3 Polyethylene film 50μ activated with hydrochloric acid 1,
This was placed on an aluminum plate having a thickness of 511111 mm, and a copper foil having a thickness of 35 μm was layered thereon and melted and bonded using a hot pressure roll to produce an aluminum base copper clad plate.

Comparative Example 4 100% by weight of α-alumina (AJtOs) with an average particle size of 4 μm was added to the epoxy resin varnish of Formulation Example 1, stirred well, and applied to the surface of a 35-thick rolled copper foil to a thickness of 80 μm and bonded. A layer was prepared, placed on a 1.5-inch thick aluminum plate activated with hydrochloric acid, and bonded under heat with a heated roll to produce an aluminum-based copper-clad plate.

Test Results The results of testing each characteristic of the above Examples and Comparative Examples are shown in the 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. Discharge...Resin layer, 21...Inorganic filler, 4...Heat-resistant resin film, 5...
metal foil. Patent applicant Showa Denko Co., Ltd. Nitskan Kogyo Co., Ltd. Agent Patent attorney Sei Kikuchi

Claims (2)

[Claims] (1) A printed circuit board comprising a heat-resistant resin film attached to at least one surface of a metal plate via a synthetic resin layer containing an inorganic filler, and a synthetic resin layer provided on the film surface. (2) Printing made by pasting a heat-resistant resin film on at least one surface of a metal plate through a synthetic resin layer containing an inorganic filler, and pasting a metal foil onto the film surface through a synthetic resin layer. Circuit board.