JPH11150345A - Metal base circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance adhesion between a metal plate or a conductive circuit and an insulation layer by mounting the conductive circuit on a metal base circuit board through the insulation layer formed by laminating a rubber composition layer and a resin composition layer. SOLUTION: A metal base circuit board has an insulation layer 2 formed on a metal plate 1 wherein the insulation layer 2 comprises a rubber composition layer 4 of butadien rubber, isoprene rubber, buthy rubber, silicone rubber, natural rubber, chloroprene rubber or styrene-butadiene rubber having modulus of elasticity of 1×10<9> Pa of below, and a resin composition layer 5. A circuit 6 is then formed in desired shape on the insulation layer 2 using any one of copper, aluminum, nickel, iron, tin, silver and titanium or an alloy containing more than one of these metals. According to the arrangement, adhesion of the insulation layer 2 to the metal plate 1 or a conductive circuit 6 can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-based circuit board having excellent stress relaxation and heat dissipation.

[0002]

2. Description of the Related Art Conventionally, a metal base circuit board in which an insulating layer made of an epoxy resin or the like filled with an inorganic filler is provided on a metal plate, and a conductive circuit is provided thereon has a high heat dissipation property. It is used as a circuit board on which heat-generating electronic components are mounted.

[0003] On the other hand, there is a demand for electronic equipment to be mounted in an engine room as well as to reduce the size and space of the electronic equipment for vehicles. The engine room is in a harsh environment with high temperatures and large temperature changes.
Further, a substrate having a large heat dissipation area is required. For such applications, attention has been paid to the metal-based circuit boards having excellent heat dissipation.

A conventional metal-based circuit board often uses an aluminum plate for heat dissipation and economic reasons. However, when heating / cooling is repeated in actual use, the aluminum plate and electronic components, especially chips, are used. There is a problem that a large thermal stress is generated due to a difference in the coefficient of thermal expansion from the component, and cracks are generated in a solder portion fixing the component or in the vicinity thereof, thereby lowering electrical reliability.

[0005] By using a material having a low elastic modulus for the insulating layer, stress generated between the metal plate and the electronic component can be reduced. However, as the size of the chip component increases, the modulus of elasticity of the material needs to be greatly reduced.However, a material having a low modulus of elasticity generally has low adhesion to aluminum or copper of a circuit conductor. There is a problem that a metal base circuit board having excellent adhesion between the metal base plate and the metal plate cannot be obtained. In particular, since the adhesion between the conductive foil and the metal plate is significantly reduced at high temperatures, it is difficult to obtain a metal-based circuit board having excellent heat resistance.

[0006] Regarding the above problem, the present inventors have filed Japanese Patent Application No.
No. 158513 has proposed a metal-based circuit board in which at least one layer of the resin composition has a specific modulus of elasticity using an insulating adhesive layer composed of multiple resin composition layers. As a result, the above problem was solved for a wide range of chip components, but a large chip (6332) was used.
Size) is not sufficient in the case of mounting, and there is a problem that the adhesion of the insulating layer to a metal plate such as aluminum or a circuit conductor such as copper becomes weak.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an excellent adhesiveness of an insulating layer to a metal plate or a conductive circuit, an excellent stress relaxation, and a large chip ( 6332 size) It is an object of the present invention to provide a metal-based circuit board excellent in heat dissipation, which does not cause abnormalities such as cracks or the like in the solder or its vicinity due to rapid heating / cooling even when mounted. It is.

[0008]

SUMMARY OF THE INVENTION The present invention is a metal-based circuit board having a circuit mounted on a metal plate via an insulating layer, wherein the insulating layer comprises a rubber composition layer and a resin composition layer. A metal-based circuit board formed by laminating, preferably, at least one or more resin composition layers are interposed between a rubber composition layer and a circuit. It is.

[0009] The present invention has an elastic modulus of at least one layer of the rubber composition layer is -40 ℃ is less 1 × 10 ⁹ Pa, preferably, the elastic modulus at -40 ℃ 1 × 10 ⁹ Pa
The metal-based circuit board described above, wherein the following rubber composition layer is a cured silicone rubber.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 and 2 are schematic diagrams each showing a cross section of an example of the metal-based circuit board of the present invention. An insulating layer 2 is provided on a metal plate 1, and a circuit 6 is provided on the insulating layer 2.
In the present invention, the insulating layer 2 has a multilayer structure. FIG.
, The insulating layer 2 is composed of the rubber composition layer 4 and the resin composition layer 5
FIG. 2 illustrates a multilayer structure composed of the rubber composition layer 4 and the two resin composition layers 3 and 5. However, in the present invention, it suffices if it is composed of the resin composition layer and the rubber composition layer, and is not limited to the above examples.

The resin composition layers 3 and 5 and the rubber composition layer 4 of the present invention preferably contain various inorganic fillers in order to maintain high heat dissipation of the metal-based circuit board. The insulating layer 2 is composed of a rubber composition layer and a resin composition layer in which the kind of resin and rubber, the kind of inorganic filler or additive to be filled therein, or the quantitative ratio thereof is changed. For example, in FIG. 2, the resin composition layers 3, 5
May have different compositions or the same composition. Although not shown, when there are a plurality of rubber composition layers, the compositions of the plurality of rubber composition layers may be the same or different. The thickness of the rubber composition layer may be about 10 to 100 μm,
In particular, when the thickness is 20 to 80 μm, it is preferable because a metal-based circuit board can be manufactured with high productivity.

In the present invention, it is preferable that at least one or more resin composition layers are interposed between the rubber composition layer and the circuit. With such a configuration,
This is because the adhesive strength between the circuit and the insulating layer is increased, and the circuit is not peeled off from the insulating layer even at a high temperature exposed in actual use, so that a highly reliable metal-based circuit board can be obtained. Further, in the present invention, the adhesiveness between the circuit 6 and the insulating layer 2 is improved by blending a silane coupling agent such as epoxysilane or aminosilane in advance in the resin forming the resin composition layer in contact with the circuit 6 at least. It is desirable.

Further, in the present invention, at least one of the rubber composition layers preferably has a Young's modulus at -40 ° C. (hereinafter referred to as an elastic modulus) of 1 × 10 ⁹ Pa or less. The elastic modulus of a resin composition used for a conventionally known insulating layer is, for example, about 3 × 10 ¹⁰ Pa at −40 ° C. when an epoxy resin is highly filled with an inorganic filler. The present inventors have studied the rubber composition and found that the rubber composition has an elastic modulus of 1 × 10 ⁹ Pa or less at −40 ° C. Further, when such a rubber composition layer having a low elastic modulus is present in the insulating layer, In addition, the inventors have found that it is possible to obtain a metal-based circuit board excellent in stress relaxation without deteriorating the characteristics of having high withstand voltage characteristics and having high thermal conductivity, and have reached the present invention.

That is, according to the results of studies by the present inventors, the presence of at least one rubber composition layer in the insulating layer allows the metal-based circuit board to be heated / removed under practical conditions.
It has been found that the thermal stress generated due to the cooling history is reduced, and that the position of the rubber composition layer in the insulating layer does not need to be specified. And the rubber composition layer is -40
When the elastic modulus at ℃ is 1 × 10 ⁹ Pa or less,
The above effects are preferably achieved, and the chip size 6332
It has been found that even when a large chip is mounted, it is excellent in stress relaxation and that there is no peeling of the circuit and no reduction in reliability, leading to the present invention.

The rubber constituting the rubber composition layer of the present invention includes butadiene rubber, isoprene rubber, butyl rubber,
Silicone rubber, natural rubber, chloroprene rubber, styrene-butadiene rubber, and the like can be used.In particular, silicone rubber has a low glass transition point, and a composition having a lower elastic modulus can be obtained. Excellent in stress relaxation, for example, a large chip (633)
(2 chip size) can ensure long-term electrical reliability.

As the inorganic filler used in the rubber composition layer of the present invention, those having good electric insulation and high thermal conductivity are used, such as aluminum oxide, silica (silicon oxide), and the like. Examples thereof include aluminum nitride, silicon nitride, and boron nitride, which can be used alone or in a mixed system. Among these, aluminum oxide and silica are preferable because those having a spherical particle shape and capable of being highly filled are inexpensive and easily available.

The resin constituting the resin composition layer of the present invention may be any resin as long as it is excellent in heat resistance and electrical insulation. In addition, the inorganic filler used in the resin composition also has good electric insulation and high thermal conductivity. For example, silicon oxide, aluminum oxide, aluminum nitride, silicon nitride, boron nitride, or the like may be used alone or It can be used in combination. The thickness of the resin composition layer may be about 10 to 100 μm, and particularly preferably 20 to 80 μm because a metal-based circuit board can be manufactured with high productivity.

When the rubber composition layers or the resin composition layers are in contact with each other, and when the rubber or the resin and the inorganic filler filled therein are the same, the amount of the inorganic filler added By giving the difference of about 3%, the respective rubber composition layers or resin composition layers can be clearly distinguished when observing their cross sections using, for example, a scanning electron microscope.

As the circuit 6, any one of copper, aluminum, nickel, iron, tin, silver, and titanium, an alloy containing two or more of these metals, or a clad foil using the above metal or alloy is used. It can be obtained by processing into a desired shape. The foil may be produced by an electrolytic method or a rolling method. Ni plating, Ni-A
Although metal plating such as u plating or solder plating may be applied, the surface of the circuit 6 on the side in contact with the insulating layer is roughened in advance by etching, plating, or the like from the viewpoint of adhesion to the insulating layer 2. Is more preferable.

The metal plate 1 used in the present invention is made of aluminum, iron, copper and their alloys, or a clad material obtained by combining them, and the thickness thereof is not particularly limited. Aluminum with a thickness of 0.5 to 5.0 mm is generally selected because it is rich and economical.

In the method of manufacturing a metal-based circuit board according to the present invention, a plurality of insulating materials are prepared by adding an additive such as a curing agent to a rubber containing an inorganic filler and a resin containing an inorganic filler. A method of applying a multilayer coating on a metal plate and / or a foil, performing a heat treatment or the like as necessary, bonding and curing the metal plate and the foil via an insulating material, and then forming a circuit from the foil, or Prepare a sheet made of insulating material in advance, paste a metal plate or foil through the sheet,
Thereafter, it can be obtained by a conventionally known method such as a method of forming a circuit, or a method of directly using a previously formed circuit instead of a foil in the above method.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[0023]

[Example 1] First, a liquid silicone rubber S containing an inorganic filler was placed on a 2.0 mm thick aluminum plate.
E4450 (Toray Dow Corning Silicone Co., Ltd.)
Manufactured) (referred to as rubber composition A).
The first layer was formed so as to have a thickness of 0 μm, and heated at 150 ° C. for 30 minutes. Then, the surface was polished, and after polishing, the surface was treated with a coupling agent. On top of that, the resin composition B (Table 1)
2), a second layer having a thickness of 50 μm after curing was formed, and heated at 150 ° C. for 10 minutes. Furthermore, after press-stacking a copper foil having a thickness of 35 μm thereon, SE4450 and the resin composition B were cured at 150 ° C. for 5 hours to prepare a metal base substrate, and further, the copper foil was etched. Thus, a desired circuit having a pad portion was formed to obtain a metal-based circuit board. In addition, the thickness is about 1 mm, the width is about 2 mm, and the length is about 50
Specimens of each cured product of the rubber composition A and the resin composition B having a thickness of 2 mm were separately prepared and subjected to measurement of elastic modulus.

For each of the above cured products, a dynamic viscoelasticity meter (manufactured by Toyo Baldwin Co., Ltd .; RHEOVI)
BRON DDV-III-EP type) and frequency 1
Under the conditions of 1 Hz and a heating rate of 2 ° C./min, −100 ° C. to +
The elastic modulus was measured over a temperature range of 150 ° C. Table 1 shows the measurement results of the elastic modulus at −40 ° C. The results of measuring the copper foil peel strength of the metal-based substrate and the heat cycle test of the metal-based circuit board were measured under the following conditions. Table 2 shows the measurement results.

<Method of Measuring Copper Peel Strength> Tensilon (manufactured by Orientec; model UCT-1T) was used to
The strength when peeled at a speed of 50 mm / min in a 90-degree direction at a width of cm was determined. The measurement was performed at 20 ° C and 125 ° C.

<Heat cycle test method> A chip size of 2.1 mm × 2.5 mm, 3.2 mm × 2.
5mm, 5.0mm x 2.5mm, 6.3 x 3.2mm
Solder each of the four types of chip resistors, 10 each.
0 ° C. for 7 minutes to + 125 ° C. for 7 minutes as 1000
After performing the heat cycle test twice, the presence or absence of cracks in the solder portion was observed with a microscope.

[0027]

[Table 1]

[0028]

[Table 2]

Example 2 A liquid silicone rubber SE4410 (Toray Co., Ltd.) was first placed on a 2.0 mm thick aluminum plate.
A rubber composition C (see Table 1) obtained by further adding aluminum oxide to Dow Corning Silicone Co., Ltd. (containing an inorganic filler) was formed into a first layer so that the thickness after curing became 50 μm. And 150 ° C. for 30 minutes. Then, the surface was polished, and after polishing, the surface was treated with a coupling agent. On top of that, by the resin composition B (see Table 1),
A second layer having a thickness of 50 μm after curing was formed and heated at 150 ° C. for 10 minutes. Further, after a copper foil having a thickness of 35 μm is press-laminated thereon, each composition is cured at 150 ° C. for 5 hours to produce a metal base substrate, and further, the copper foil is etched to form a pad. A desired circuit having a portion was formed to obtain a metal-based circuit board. In addition, a test piece having a thickness of about 1 mm, a width of about 2 mm, and a length of about 50 mm was separately prepared and used for measurement of elastic modulus. The results are shown in Table 2.

Comparative Example 1 First, a first layer was formed on a 2.0 mm-thick aluminum plate with a resin composition D (see Table 1) so that the thickness after curing became 50 μm.
Heated at C for 15 minutes. A second layer having a thickness of 50 μm after curing was formed thereon with the resin composition B (see Table 1), and heated at 150 ° C. for 10 minutes. Furthermore, after press-stacking a copper foil having a thickness of 35 μm thereon, the resin composition was cured at 150 ° C. for 5 hours to form a metal base substrate.
Further, a metal base circuit board was prepared from the metal base board in the same manner as in Example 1, and the physical properties were measured. Table 2 shows the results.

[0031]

According to the metal-based circuit board of the present invention, the insulating layer is multilayered with a rubber composition layer and a resin composition layer.
It is very excellent in stress relaxation even at a low temperature of × 10 ⁹ Pa or less, so that it does not crack even in a solder portion fixing a large chip (6332 size) even under a severe temperature change received under actual use conditions. A reliable hybrid integrated circuit can be provided.

In addition, the metal-based circuit board of the present invention
By adding an inorganic filler to the rubber composition layer and / or the resin composition layer, the conventional point of excellent heat dissipation, excellent point of electric insulation such as withstand voltage, etc. are maintained as good. Since the stress relaxation property is improved, it can be used even in a harsh environment such as an engine room of an automobile, and is industrially very useful.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a metal-based circuit board of the present invention.

FIG. 2 is a sectional view showing another example of the metal-based circuit board of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal plate 2 Insulating layer 3 Resin composition layer 4 Rubber composition layer 5 Resin composition layer 6 Circuit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Ryuichi Terasaki Inventor 3-5-1 Asahicho, Machida-shi, Tokyo Denki Kagaku Kogyo Co., Ltd.

Claims (4)

[Claims] 1. A metal base circuit board comprising a metal plate and a circuit mounted thereon via an insulating layer having a multilayer structure,
A metal-based circuit board, wherein the insulating layer comprises a rubber composition layer and a resin composition layer. 2. The metal-based circuit board according to claim 1, wherein at least one or more resin composition layers are interposed between the rubber composition layer and the circuit. 3. The method according to claim 1, wherein at least one of the rubber composition layers has a temperature of -40.degree.
3. The metal base circuit board according to claim 1, wherein an elastic modulus of the metal base circuit board is 1 × 10 ⁹ Pa or less. 4. The method according to claim 1, wherein the rubber composition layer having an elastic modulus at −40 ° C. of 1 × 10 ⁹ Pa or less is a cured silicone rubber. Metal-based circuit board.