JP3231295B2 - Metal base circuit board - Google Patents

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 for mounting a semiconductor used in various electric devices such as a communication device, in particular, a mobile device such as an automobile or mobile communication.

[0002]

2. Description of the Related Art A circuit board on which electronic components such as semiconductor elements are mounted is used in various electric equipment applications, and since it is inexpensive and has excellent heat dissipation properties, a resin containing an inorganic substance is formed on a metal plate. A metal-based circuit board has been used in which circuits formed of metal foil are stacked via an insulating layer.

[0003] Since the metal-based circuit board has the above structure, it is limited in many aspects such as the heat conduction property of the insulating layer, the withstand voltage property, and the adhesiveness to the metal plate or the conductive foil. This is an important factor in improving the characteristics of the base circuit board.

For example, Japanese Patent Application Laid-Open No. Hei 6-44824 discloses that
By using a high-purity bisphenol A type epoxy resin, an insulating adhesive composition for a circuit board that has high thermal conductivity, a high glass transition point, excellent heat dissipation, and high electrical reliability under high temperature is disclosed. .

Further, Japanese Patent Application Laid-Open No. 5-29490 discloses that
It is disclosed that by defining a foil foot of an aluminum-copper clat foil known as a conductive foil, a high withstand voltage and a high peel strength can be obtained.

[0006]

In recent years, in circuit boards for mounting semiconductors used in automobiles and the like, demands for higher density and higher mounting of semiconductor parts, electric parts, and circuit parts have been increasing. . Modules with components such as diodes, transistors, and ICs mounted on these circuit boards dissipate the heat generated by the components or the circuit itself. There is a demand for a circuit board having the same.

In a conventional metal-based circuit board, as described above, the foil foot on the side in contact with the insulating layer of the conductive foil has a specific length in order to secure the adhesive strength between the conductive foil and the insulating layer. The insulating layer made of a resin containing an inorganic substance is formed thicker than 100 μm in order to secure electrical characteristics such as insulation resistance. If the thickness of the insulating layer is reduced in order to increase the heat dissipation, there is a problem that the electric characteristics such as the withstand voltage are deteriorated. That is, the insulating layer is 100 μm
It was not possible to obtain a metal-based circuit board which was excellent in heat dissipation and less than the conventional one and had the same electrical reliability as the conventional one.

In view of the above circumstances, the present inventors have conducted various experimental studies, and have found that when the structure of the insulating layer and the surface condition of the conductive foil take a specific relationship, they have the conventional electrical characteristics. On the other hand, the present inventors have found that the thickness of the insulating layer can be made thinner than before so as to improve the heat radiation characteristics, and have reached the present invention.

[0009]

According to the present invention, there is provided a metal-based circuit comprising a metal plate, a conductive foil laminated on an insulating layer made of an epoxy resin containing an inorganic substance, and a circuit formed by etching the conductive foil. A substrate, wherein the inorganic substance has an average particle size.
60-80 vol% of particles having a diameter of 5-50 μm and average particles
Particles having a diameter of 0.2 to 1.5 μm and 40 to 20 vol%
The insulating layer has a multilayer structure and has a total thickness of 50 to
90 μm, and the thickness of the surface layer of the insulating layer that is in contact with the conductive layer is thicker than the length of the foil layer of the conductive layer that is in contact with the insulating layer; Is a metal base circuit board having a length of 0.5 to 40 μm.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing an example of a metal-based circuit board according to the present invention. A conductive foil 3 on which a circuit is formed is stacked on a metal plate 1 via an insulating layer 2 having a multilayer structure. The insulating layer 2 is composed of a first insulating layer 21 and a second insulating layer 22 from the side in contact with the metal plate 1,
The uppermost second insulating layer 22 is in contact with the conductive foil 3. Then, the second insulating layer 2 serving as a surface layer on the side in contact with the conductive foil 3
2 is configured to be thicker than the length of the foil foot of the conductive foil 3 on the side in contact with the insulating layer 2. Although FIG. 1 illustrates the case where the insulating layer 2 has a two-layer structure, it is needless to say that the insulating layer 2 may have a multilayer structure of three or more layers if the surface layer satisfies the above configuration.

Since the above configuration is adopted, the insulating layer 2
Even if the overall thickness of the is less than 100 μm thinner than before,
The electric characteristics such as the withstand voltage do not decrease. In particular, when the conductive foil 3 is laminated on the insulating layer 2, it is caused by a phenomenon such as entrapment of a void which is likely to be generated under the influence of the length of the foil foot of the conductive foil 3. This is to prevent the withstand voltage characteristics from being lowered.

Further, in the metal base circuit board of the present invention, the length of the foil leg side of the surface contacting the insulating layer 2 of the conductive foil 3 is Ru 0.5~40μm der. The length of the foil foot is 0.5 μm
If less than, the adhesive strength between the insulating layer and the conductive foil, that is, the peel strength is reduced, and the insulating layer and the conductive foil may be peeled off. Due to the electric field concentration, there may be a problem in long-term electrical reliability of the metal-based circuit board under actual use conditions.

In the present invention, with respect to the insulating layer 2 having a multilayer structure, the individual insulating layers may have the same composition or may be different. Regarding the composition of the insulating layer 2, a resin containing an inorganic substance is used to obtain high thermal conductivity. Examples of the inorganic substance include alumina, silica, boron nitride, aluminum nitride, and silicon nitride. Examples of the resin include an epoxy resin and an imide resin.

As a preferable resin composition for forming the insulating layer, for example, 10 to 40 vol% of a bisphenol A type epoxy resin having a purity of 90% or more and 90 to 60 vol% of an inorganic filler disclosed in JP-A-6-44824.
And the thermal conductivity of the cured product is 2.1 to 7.5 J / ° C.
· M · sec and glass transition temperature of 164 to 240 ° C
An insulating material having the following characteristics:

In addition, regarding the inorganic substance, 60 to 80 vol% of particles having an average particle diameter of 5 to 50 μm and 40 to 20 vol% of particles having an average particle diameter of 0.2 to 1.5 μm (total 1%)
00vol%) Tona is, furthermore, an average particle diameter of 12 to 2
0-μm particles 60-80 vol% and average particle diameter 0.6-
Inorganic substances composed of 40 to 20% by volume of 0.8 μm particles are good.

In addition, a silane-based coupling agent, a titanate-based coupling agent, a stabilizer, a curing accelerator, and the like can be used as necessary for the insulating material.

As the metal plate 1 used in the present invention, aluminum and aluminum alloy, copper and copper alloy, iron, stainless steel, etc. having good thermal conductivity can be used.
The thickness of the metal plate 1 is not particularly limited, but is not limited to 0.1.
5-3.0 mm is commonly used.

According to the method for obtaining a metal-based circuit board of the present invention, an insulating layer is repeatedly applied and dried on a metal plate, and a metal foil such as copper, aluminum or a copper-aluminum composite foil is joined. Thereafter, the metal foil can be easily obtained by etching the metal foil into a circuit. Alternatively, it can be obtained by a method in which a large number of insulating layers are joined to a metal plate, and then a metal foil formed in advance with a circuit is bonded. Among these methods, the former method is preferable because it can be freely designed and manufactured by simply changing the process conditions of the insulating layer having a multilayer structure, and therefore, is excellent in multi-product productivity.

[0020]

Examples [Examples 1 to 5] Bisphenol A type epoxy resin having a purity of 90% or more (Dainippon Ink Chemical Co., Ltd., EP
CLON EXA-850CRP) 25 vol% alumina (Showa Denko KK, AS-30-1 and Sumitomo Chemical Co., Ltd., AKP-1
5) Prepare an insulating material mixed with 75 vol%, and set the thickness to 2.0.
mm on an aluminum plate, apply the insulating material to a desired thickness, dry it to a B-stage state, apply the insulating material to a desired thickness, and dry
Stage, then 85μm thick copper and 40mm thick
A copper-aluminum composite foil made of μm aluminum was joined so that copper was in contact with the insulating layer, and heated under pressure to cure the insulating material, thereby obtaining a metal base substrate. In addition, the length of the copper foil foot of the composite foil was 16 μm on average, and the maximum value was 27 μm.

An etching resist is printed at a desired position on each of the various metal base substrates. First, aluminum is etched at a desired portion of the metal foil using an aqueous solution of sodium hydroxide as an etching solution, and then the etching resist is removed. Then, the desired position is masked with an etching resist, the copper is etched using a mixed solution of sulfuric acid and hydrogen peroxide as an etching solution, then the etching resist is removed, and the substrate is washed and dried, thereby forming circuits and forming various metal-based circuit boards. Obtained.

With respect to the metal base substrate or the metal base circuit board obtained by the above operation, the dielectric breakdown strength and the thermal resistance were measured. The measurement of dielectric breakdown strength is based on JIS C2110
Based on TOS-8700 (Kikusui Electronics Corporation)
Manufactured by Toshiba Corporation. For the measurement of the thermal resistance, the metal base substrate was cut into 3.0 × 4.0 cm, and a copper pattern of 1.0 × 1.0 mm was formed by etching. A TO-220 type transistor was soldered on the copper foil, and fixed on a water-cooled heat radiation fin via heat radiation grease.
The transistor was energized to generate heat, and the thermal resistance was measured.

[0023]

[Table 1]

[Comparative Example] As a comparative example, the operation was carried out except that the length of the surface layer on the side of the insulating layer in contact with the conductive foil was set to 20 μm, which was smaller than the length of the foil foot of the conductive foil. A metal base substrate and a metal base circuit board obtained by the same operation as in Example 1 were prepared, and the same evaluation as in the example was performed. The results are shown in Table 1.

[0025]

The metal-based circuit board of the present invention is a metal-based circuit board which has not been obtained conventionally and has excellent heat dissipation with an insulating layer of less than 100 μm and has the same electrical reliability as the conventional one. Therefore, it is extremely important in industry since the limitation of the application which has been conventionally received is eliminated.

[Brief description of the drawings]

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

[Explanation of symbols]

 Reference Signs List 1 metal plate 2 insulating layer 21 first insulating layer 22 second insulating layer 3 conductive foil

Claims (1)

(57) [Claims] 1. A metal base circuit board formed by laminating a conductive foil on a metal plate via an insulating layer made of an epoxy resin containing an inorganic substance and etching the conductive foil to form a circuit, wherein the inorganic substance is Particles 60 having an average particle diameter of 5 to 50 μm
Particles having a mean particle size of 0.2 to 1.5 µm
The insulating layer has a multilayer structure, the total thickness is 50 to 90 μm, and the thickness of the surface layer of the insulating layer on the side in contact with the conductive foil is in contact with the insulating layer of the conductive foil. A metal base circuit board characterized in that it is thicker than the length of the foil foot on the side, and the length of the foil foot on the side in contact with the insulating layer of the conductive foil is 0.5 to 40 μm.