JPH0216696B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a metal foil-covered metal substrate with excellent heat dissipation properties.

Traditionally, resin-based copper-clad laminates such as phenolic resin/paper-based copper-clad laminates and epoxy resin/glass cloth-based copper-clad laminates have been manufactured by laminating a large number of semi-cured prepregs and copper foils up to the B stage. This was inserted into a multi-stage press and heated and pressurized to harden the resin. The advantage of this method is that a large number of laminated substrates can be manufactured at one time, but the disadvantages are that it takes a long time for preliminary operations, temperature raising, etc.; Process control such as cooling was difficult, and equipment investment was large.

By the way, in recent years, aluminum-based copper-clad substrates with thermal conductivity and electrical insulation properties have appeared as substrates for hybrid ICs on which semiconductor elements that generate a lot of heat, such as power transistors and power ICs, are mounted. It has come to be used exclusively. These aluminum substrates can be made by thermo-compression bonding a copper foil coated with an adhesive to an aluminum substrate using a multi-stage press, or by placing a semi-cured prepreg in a B-stage shape on an aluminum substrate, and then attaching a copper foil to the aluminum substrate. It is manufactured using a method in which the parts are placed and then heat-compressed using a multi-stage press. However, the thickness of the insulating adhesive layer that exists between the aluminum substrate and the copper foil is 1/10 that of the resin-based copper-clad laminate described above.
Because the copper foil is as thin as ~1/50, it is very difficult to completely degas it during pressing, and bubbles may remain, which poses problems in the reliability of the adhesive strength and withstand voltage of the copper foil.

The inventors of the present invention have conducted intensive studies on a method for producing metal foil-covered metal substrates that does not use a multi-stage press, which is extremely difficult to operate and requires a large amount of equipment investment. We have invented a method for manufacturing metal foil-clad metal substrates with reliable adhesive strength.

That is, in the present invention, an insulating layer of an epoxy resin composition is formed on at least one main surface of a metal plate, and the insulating layer and metal foil are pressed between heating rolls and the metal is melted while the insulating layer is melted. A method for producing a metal foil-covered metal substrate in which a foil is temporarily bonded to the insulating layer to form a metal foil-covered metal substrate, and then the metal foil-covered metal substrate is heat-treated again to post-cure the insulating layer, the method comprising: The insulating layer of the epoxy resin composition formed on the metal plate is at least two layers, and the epoxy resin composition is applied to the metal plate and then heated and cured to form the first insulating layer, and then the second insulating layer is formed. When forming the second insulating layer, the heating time for curing the second insulating layer is shorter than the time for curing the first insulating layer, and the degree of curing is varied. This is a method for manufacturing metal foil-covered metal substrates.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a schematic sectional view of a heating roll portion of the present invention, and FIG. 2 is a schematic sectional view of a heated roll portion in which a metal foil-covered metal substrate is inserted. FIG. 1 shows a heating roll part that can be used in the present invention, and reference numerals 1 and 6 are stands (support stands) that support the materials to be laminated during transfer. 2, 3, 4, and 5 are rolls, and the rolls 2, 3, 4, and 5 are constructed to be pressurized by hydraulic pressure or the like. Among the rolls, at least roll 2 is equipped with a heater, and its surface is made of heat-resistant rubber such as silicone rubber to facilitate degassing during lamination. Rolls 3, 4 and 5 are roll 2
The specifications may be exactly the same, but metal rolls are also possible.

When manufacturing a metal foil-covered metal substrate (hereinafter referred to as a substrate), an insulating layer 8 is first formed on a metal substrate 9, a metal foil 7 is placed on top of the insulating layer 8, and the layer is passed through a heating roll as shown in FIG. As a result, as shown in FIG. 2, the surface layer of the insulating layer 8 is melted by the heat generated by the heater of the roll 2, and the metal foil 7 is melted by the pressure of the rolls 2 and 3.
They are crimped one after another in the direction of the arrow with degassing. The substrates are further heated or cooled under pressure again with rolls 4 and 5 to be temporarily bonded. This temporarily bonded substrate is further heated and post-cured. For this post-curing, a normal blow dryer, far-infrared dryer, etc. are used, but a method of hot pressing is also possible.

As the metal substrate of the present invention, aluminum and its alloys, iron, iron-nickel alloy, stainless steel, etc. are used, but an aluminum plate treated with alumite may be used without any problem.

Next, as metal foil, copper foil, aluminum foil,
Foils made by cladding aluminum foil and copper foil, foils made by plating copper foil with different metals, etc. can be used. The appropriate thickness of the metal foil is 5μ to 200μ.

The metal foil used for manufacturing the substrate according to the present invention may be either sheet-shaped or rolled, and in particular, in the latter case, continuous production is possible.

Next, the insulating layer on the metal substrate used in the present invention is
Epoxy resin compositions such as B-stage prepregs and filler-containing epoxy resins that melt when heated are preferable, and it is preferable to apply them at least twice in terms of withstand voltage. Furthermore, it is preferable that the insulating layers have different degrees of hardening from the viewpoint of withstand voltage.

In addition, the laminating conditions of the present invention vary depending on the melting of the insulating layer and the state of temporary adhesion, but the roll temperature is 50 to 200°C, and the roll speed is 0.5 to 10 m/min.
The roll pressure force is preferably in the range of 1 to 10 Kg/cm ² . Outside this range, the state of temporary adhesion of the metal foil to the metal substrate and productivity will deteriorate. In addition, for the subsequent post-curing of the metal foil-covered metal substrate, the curing time is generally 24 hours to 10 minutes depending on the temperature at 20°C to 200°C in a dryer, depending on the condition of the insulating layer curing agent. You need to choose.

The present invention will be further explained below with reference to Examples.

Example 1 A filler-containing epoxy resin containing a hardening agent was applied onto a 1.5 mm aluminum plate using a spray gun.
It was painted to a thickness of 40μ. This was then cured on an aluminum plate at 80° C. for 90 minutes, and then an additional 40 μm insulating layer was applied in the same manner. This aluminum plate with an insulating layer was cured at 80° C. for 30 minutes, and a sheet of 35 μm copper foil was laminated with a heating roll having a roll diameter of 15 cm having the structure shown in FIG. Rolls 2 and 3 are heated to 150℃, and roll 4
and 5 are conditions without heating. The aluminum plate feeding speed is 1.0m/min, and rolls 2 and 4
A pressure of 2Kg/cm ² is applied to the

Next, the copper foil-covered aluminum substrate produced by this operation was cured at 140° C. for 3 hours in a blower dryer. The peel strength of the resulting copper foil-covered aluminum substrate was 2.0 Kg/cm ² , and no blistering of the copper foil was observed even in a 30-minute immersion test at 300° C. in a solder bath. After this heat treatment, the withstand voltage of the copper foil-clad aluminum substrate was measured to be 2 KV or more.

Example 2 Similar to Example 1, filler-containing epoxy resin insulating layers having two different degrees of hardening were formed on an aluminum plate, and a 30 μm insulating layer was further formed thereon, and after curing at 80°C for 20 minutes, the 2, 3, 4, 5 in Figure 1
A sheet of 35 μm copper foil was laminated at a board feeding speed of 1.5 m/min with all rolls heated to 100°C. However, the substrates to which rolls 4 and 5 were applied were cooled by cold air and reached room temperature within 10 minutes.

The copper foil-clad aluminum substrate produced by this operation was post-cured under the same conditions as in Example 1. The peel strength of the copper foil-covered aluminum substrate obtained was 2.2Kg/
cm ² , and as in Example 1, no blistering of the copper foil occurred even in the solder bath immersion test at 300° C. for 30 minutes. After this heat treatment, the copper foil-covered aluminum substrate had a withstand voltage of 3 KV or more when measured.

Example 3 Same as example 2, but with different degree of hardening 3
A 30 cm square aluminum plate coated with an insulating layer consisting of layers was laminated using rolled 35μ copper foil under the same heated roll conditions as in Example 2. The cooling is
After cutting the copper foil in the same manner as in Example 2, Example 1
It was post-cured under the same conditions. The peel strength of the copper foil-clad aluminum substrate obtained was 1.9 Kg/cm.
Even in a solder bath immersion test at 300°C for 30 minutes, no blistering occurred in the copper foil. After this heat treatment, the withstand voltage of the copper foil-clad aluminum substrate was measured and was 3 KV or more.

Comparative example 1 On the same aluminum plate with insulating layer as in Example 1
The 35μ copper foil was left standing, placed in a press heated to 100°, left under pressure for 30 minutes, and then raised to 150°C and heated for 2 hours to produce a copper-clad board. When we measured the peel strength of a copper foil-clad aluminum substrate, we found that
In most cases, the temperature was 2.0Kg/cm, but in some areas it was 1.4Kg/cm, indicating that there was a possibility that air bubbles were mixed in between the copper foil and the insulating layer. When this copper foil-covered aluminum board was subjected to a solder bath immersion test at 300°C for 30 minutes, partial blistering of the copper foil was observed within a few minutes, and ultimately a 5cm diameter copper foil blister was observed. Furthermore, when the withstand voltage of the copper foil-clad aluminum substrate without heat treatment was measured, it was 0.5 KV or less.

Comparative Example 2 An 80 μ insulating layer was formed by 1.5 μm by the same operation as in Example 1.
Painted on an aluminum plate with a thickness of mm. This aluminum substrate with an insulating layer was cured at 80° C. for 30 minutes, and operations were performed under the same laminating and curing conditions as in Example 1 to produce a 35μ copper foil-clad aluminum substrate. The peel strength of the copper foil-covered aluminum board obtained was 1.9 Kg/cm, and the peel strength was 1.9 kg/cm.
Partial blistering occurred after soaking for a minute. After this heat treatment, the withstand voltage of the copper foil-clad aluminum substrate was measured and was 1.0 KV or less. When the substrate before heat treatment was etched and the copper foil was removed, defects were found in some parts of the insulating layer.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a heating roll portion of the present invention, and FIG. 2 is a schematic sectional view of a heated roll portion in which a metal foil-covered metal substrate is inserted. Symbols 1, 6...Support stand, 2, 3, 4, 5...Roll, 7...Metal foil, 8...Insulating layer, 9...Metal substrate.

Claims (1)

[Scope of Claims] 1. An insulating layer of an epoxy resin composition is formed on at least one principal surface of a metal plate, and the insulating layer and metal foil are pressed between heating rolls while melting the insulating layer. A method for producing a metal foil-covered metal substrate, wherein the metal foil is temporarily bonded to the insulating layer to form a metal foil-covered metal substrate, and then the metal foil-covered metal substrate is heat-treated again to post-cure the insulating layer. , the insulating layer of the epoxy resin composition formed on the metal plate is at least two layers, and the epoxy resin composition is applied to the metal plate and cured by heating to form the first insulating layer; When forming the second insulating layer, the heating time for curing the second insulating layer is shorter than the heating time for curing the first insulating layer, and the degree of curing is varied. A method for manufacturing a metal foil-covered metal substrate characterized by: