JP2000208882A - Metal base circuit board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a circuit board for high-density by providing, on a metal plate, a circuit which, comprising a composite layer of aluminum and copper, comprises an upper layer part whose cross-section is triangular through an insulating layer. SOLUTION: A circuit 3 comprising a composite layer of aluminum 4 and copper 5 is formed on a metal plate 1 of aluminum, copper, stainless, etc., having thickness, for example, about 0.5-4.0 mm through an insulating layer 2 of a resin comprising an inorganic filler, with the copper surface of the circuit 3 comprising the composite layer of aluminum and copper contacting the insulating layer 2. Here, at least, a part of the circuit comprising the composite layer of aluminum and copper comprises an upper layer part whose cross-section is triangular. Since the current value flowing a circuit is relatively low and a cross-section area is large if the current value is equal, a narrower conductor width and conductor interval are achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high heat-generating electronic component or a hybrid integrated circuit in which a high heat-generating electronic component and a control circuit electronic component are mounted at high density. The present invention relates to a metal-based circuit board for a hybrid integrated circuit capable of obtaining a high-density hybrid integrated circuit that is excellent in reliability and therefore excellent in reliability, and a method of manufacturing the same.

[0002]

2. Description of the Related Art As a circuit board for mounting a high heat-generating electronic component, a metal having good heat conductivity, for example, aluminum,
Using a metal plate such as copper as a base material, an insulating layer made of an inorganic filler-containing resin having a thickness of about several tens of μm is provided on the metal plate,
Further, a metal base circuit board in which a circuit made of a conductive foil is laminated on the insulating layer is used. BACKGROUND ART A metal-based circuit board has high thermal conductivity and can be used by mounting electronic components that generate a large amount of heat, and is therefore preferably used for applications in the field of high power.

However, with respect to the metal-based circuit board for the application field, the number of elements and the number of inputs and outputs mounted on the board have increased with the advancement of functions, and accordingly, the number of inputs and outputs and the number of wirings between the elements have increased. Is increasing. For this reason, the area required for wiring is increasing with the increase in the number of wirings in the circuit board, and increasing the size and cost of the circuit board has become an industrial problem to be solved.

As a method for forming a circuit on a metal-based circuit board, a method of forming a circuit by etching a conductive foil provided on an insulating layer on a metal plate is known. In the method, an etching resist ink is printed on the surface of the conductive foil in a portion to be a desired circuit by a screen printing method, and after the ink is cured, etching is performed by immersing the conductive foil in a soluble etching solution. In addition, the adjustment of the amount of ink in screen printing was not easy, and a narrow circuit interval could not be easily obtained (see JP-A-7-44087). That is, if the ink amount is reduced, there is a problem that a disconnection or a conductor defect occurs, and a satisfactory product cannot be obtained. Conventionally, a minimum circuit interval of only about 250 μm has been obtained.

Also, due to the above technical problem, a design corresponding to the function of the circuit on the circuit board is not performed, and a circuit in which only a small signal flows has the same shape as a circuit in which a relatively large current flows (generally, In practice, the cross section of the circuit must be trapezoidal or rectangular, and the pitch of the circuit cannot be reduced. As a result, this is an obstacle to reducing the size and density of the circuit board.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to reduce the size of a circuit board and increase the density of the circuit board by reducing the distance between conductors. is there. Another object of the present invention is to further reduce the conductor width of the minute signal circuit and achieve further downsizing and higher density of the circuit board.

[0007]

That is, the present invention is a metal-based circuit board comprising a metal plate and a circuit comprising a composite layer of aluminum and copper provided on a metal plate with an insulating layer interposed therebetween. A metal-based circuit board having a portion having an upper layer of a cross-sectional shape, preferably the metal-based circuit, wherein copper is provided on an insulating layer side of the circuit. It is a substrate.

Further, the present invention is the above metal-based circuit board, wherein the minimum value of the distance between adjacent circuits is 50 to 240 μm, and more preferably, the circuit has a circuit width of 50 to 240 μm. The metal-based circuit board described above, comprising:

Further, the present invention provides a method for applying an insulating layer on a metal plate, further comprising attaching a composite foil composed of a copper layer and an aluminum layer on the insulating layer and curing by heating. A method for producing a metal base substrate, in which an etching resist ink is applied by a screen printing method, the etching resist ink is cured, and a circuit is formed by etching the composite foil that is not covered with the etching resist, A method of manufacturing a metal-based circuit board, characterized in that a circuit is formed by etching until the surface of the composite foil disappears, and preferably, when the etching resist ink is screen-printed, the etching resist ink is printed by a copper method. The method for manufacturing a metal-based circuit board according to claim 1, wherein the metal-based circuit board is returned to a previous position.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is an enlarged sectional view of a circuit showing an example of the metal-based circuit board of the present invention. The metal base circuit board of the present invention has a thickness of 0.5, such as aluminum, copper, and stainless steel.
A circuit 3 made of a composite layer of aluminum 4 and copper 5 is formed on a metal plate 1 having a thickness of about 4.0 mm via an insulating layer 2 made of a resin containing an inorganic filler. In FIG. 1, a copper surface of a circuit 3 composed of a composite layer of aluminum and copper is provided in contact with an insulating layer 2. In the present invention, although the aluminum surface may be provided in contact with the insulating layer 2, the bonding strength between the insulating layer 2 and the circuit 3 can be easily increased by providing the copper layer in contact with the insulating layer 2. Is preferred. This is because a known technique of providing a layer made of acicular or granular copper particles on the copper layer by electroless or electrolytic plating or roughening the surface by treatment with a chemical agent can be easily applied.

The metal-based circuit board according to the present invention is characterized in that at least a part of the circuit composed of the composite layer made of aluminum and copper has an upper layer having a triangular cross section. In a conventional hybrid integrated circuit, a circuit generally has a trapezoidal shape (see FIG. 2) or a rectangular cross section. On the other hand, the metal base circuit board of the present invention employs the above-described configuration, so that a current value flowing through the circuit is reduced. Is relatively small,
In addition, when the current value is the same, the cross-sectional area can be increased, so that the conductor width and the conductor interval can be reduced. As a result, the metal-based circuit board of the present invention has a feature that the circuit can have a high density and a high heat-generating electronic component can be mounted.

The metal-based circuit board of the present invention is characterized in that the minimum value of the distance between adjacent circuits is 50 to 240 μm, and preferably, the circuit has a portion having a circuit width of 50 to 240 μm. The minimum value of the distance between circuits is 50
If the thickness is less than μm, there are occasions where the electrical insulation between the adjacent circuits cannot be satisfied when actually used,
If it exceeds μm, there is no reason to apply the present invention, and conventionally known ones are sufficient. For the same reason, in the present invention, the circuit is 50 to 24.
It is preferable to have a portion having a circuit width of 0 μm.

In the metal-based circuit board of the present invention, the resin used for the insulating layer 2 is epoxy resin, silicone resin, polyimide resin, BT resin or the like, but has a high bonding strength to the metal plate 1 or the circuit 3. For this reason, epoxy resins are preferred. As the inorganic filler contained in the insulating layer 2, an electrically insulating and thermally conductive material is used, such as silica, alumina, aluminum nitride, or the like.
Ceramic powder such as silicon nitride and boron nitride is used. The thickness of the insulating layer 2 is generally 40 to 300 μm.

The composite layer composed of aluminum and copper used in the present invention may be any of those obtained by a conventionally known method such as a rolling method and a plating method. As for its thickness, the total thickness is preferably from 20 to 85 μm, of which the aluminum thickness is preferably from 10 to 50 μm. If the total thickness is less than 20 μm, a sufficient current value cannot be passed through the circuit.
This is because it is difficult to manufacture a circuit width of m or a circuit interval.
If the aluminum thickness is less than 10 μm, stable wire bonding may not be ensured,
If the thickness exceeds 50 μm, peeling of the etching resist occurs at the time of etching of aluminum, and it is difficult to manufacture a circuit.

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

[0016]

EXAMPLES Example 1 Bisphenol A type epoxy resin containing 55% by volume of aluminum oxide (manufactured by Showa Denko; SRW) on an aluminum plate having a thickness of 1.5 mm (manufactured by Yuka Shell Co .; EP828) When the thickness of the insulating layer is 50
μm, and a metal foil composed of a composite layer of an aluminum layer and a copper layer is further arranged so that the copper layer is in contact with the insulating layer, and the insulating layer is cured by heating under pressure. A metal base substrate was manufactured. At this time, the thickness of the aluminum layer was 40 μm, and the thickness of the copper layer was 10 μm.

After attaching a protective sheet made of polypropylene to the back surface of the aluminum plate of the metal base substrate, an etching resist is formed at a desired position on a metal foil made of a composite layer of aluminum and copper by using a screen printing method. Then, aluminum was etched using an aqueous solution of caustic soda.

In the above-mentioned screen printing method, a resist ink is used in a copper method (scooping up the ink remaining on the screen when the previous printing is completed,
(The method of returning to the position before printing by passing through the air without touching the screen, and then performing the next printing)
, The amount of ink from the screen was limited and controlled.

Next, after removing the resist, a resist is applied again to a desired portion of the copper layer, and an etching resist is formed by using the above-mentioned aluminum.
The copper layer was etched with a mixed solution of 1 and 45 g / l of hydrogen peroxide. Then, a metal base circuit board was obtained by removing an etching resist and a protection sheet.

This metal base circuit board had a minimum circuit width of 100 μm and a minimum conductor interval of 100 μm in the signal circuit portion. Further, the area of the signal circuit portion can be reduced to one-half of the area required for the conventional metal base circuit board, and as a result, the entire area of the metal base circuit board can be reduced. The density was reduced to about 50% of the conventional one, and a high density was achieved.

[0021]

According to the metal-based circuit board of the present invention, at least a part of the upper layer of the circuit has a triangular cross-sectional shape, so that a circuit can be formed at a high density and a circuit through which a relatively small current flows can be efficiently formed. Since it has a feature that it can be mounted, it is suitable as a substrate for a hybrid integrated circuit requiring a signal circuit.

Further, according to the method of the present invention, the circuit has the cross-sectional shape, and the minimum value of the distance between the circuits is 50 to 240 μm.
m, and furthermore, a metal-based circuit board having a circuit having a portion with a circuit width of 50 to 240 μm can be stably obtained, which is industrially very useful.

[Brief description of the drawings]

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

FIG. 2 is an enlarged cross-sectional view of a circuit of a conventionally known metal-based circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal plate 2 Insulating layer 3 Circuit 4 Aluminum 5 Copper

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 4E351 AA03 AA14 BB01 BB23 BB24 BB30 BB35 DD04 DD10 DD54 FF04 FF07 FF08 FF10 GG20 5E315 AA03 BB01 BB03 BB15 BB18 CC01 DD13 DD16 DD17 GG05 GG22 5E338 BB01A18A01A AD01 BC02 BC03 BD03 BD06 BE13 CE19

Claims (6)

[Claims] 1. A metal base circuit board comprising a metal plate provided with a circuit comprising a composite layer of aluminum and copper via an insulating layer, wherein the circuit has a portion having an upper layer portion having a triangular cross section. A metal-based circuit board, comprising: 2. The metal-based circuit board according to claim 1, wherein copper is provided on the insulating layer side of the circuit. 3. The minimum value of the distance between adjacent circuits is 50 to 50.
The metal-based circuit board according to claim 1, wherein the thickness of the metal-based circuit board is 240 μm. 4. The metal-based circuit board according to claim 1, wherein the circuit has a portion having a circuit width of 50 to 240 μm. 5. An insulating layer is coated on a metal plate, and a composite foil composed of a copper layer and an aluminum layer is pasted on the insulating layer and cured by heating, and then a screen printing method is performed on the composite foil. A method of manufacturing a metal base substrate, comprising applying an etching resist ink, curing the etching resist ink, and etching the composite foil not covered with the etching resist to form a circuit, wherein the surface of the composite foil is And forming a circuit by etching until disappearance of the metal base circuit board. 6. The method of manufacturing a metal-based circuit board according to claim 5, wherein, when screen-printing the etching resist ink, the etching resist ink is returned to a position before printing by a scooper method.