JP2001196739A - Metal base circuit board and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a metal base circuit board mounting a circuit of metal foil on a metal plate through an insulation layer in which a conduction circuit can be fabricated efficiently with high quality. SOLUTION: A circuit is formed of a conductive foil by press and a half push-back conductive foil, having a partially refilled part is bonded onto a metal plate via an insulation layer at a part of the circuit other than the circuit of the conductive foil which is subsequently removed. In such a method for manufacturing a metal base circuit board, the edge of the circuit abutting on the insulation layer has a radius of curvature of 0.1 mm or large.

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 electric equipment, communication equipment, automobiles and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Circuit boards on which semiconductor elements and various electric components are mounted are known in a wide range of fields such as electric equipment, communication equipment, and automobiles. However, metal bases are inexpensive and have excellent heat dissipation. Circuit boards have attracted attention and are being used.

A metal-based circuit board has a structure in which a circuit is provided on one main surface of a metal plate excellent in heat dissipation through an insulating layer, and iron and aluminum are often used for the metal plate. The insulating layer is made of a resin such as an epoxy resin containing an inorganic filler such as aluminum oxide, and the circuit is formed of various metal foils, usually made of copper, aluminum, or a composite material of copper and aluminum. It is heavily used.

[0004] As a method of forming a conductive circuit on the metal-based circuit board, there is a method of forming a pattern by etching after bonding a conductive foil (hereinafter referred to as an etching method). There has been known a method of forming a lead frame by forming a pattern with a press die and joining the lead frame to a metal plate via an insulating layer (hereinafter, referred to as a lead frame method).

FIG. 2 is a view for explaining a metal-based circuit board manufactured by an etching method and its steps. FIG.
2A and 2B are a plan view and a cross-sectional view of a metal base substrate in which a metal foil is adhered to a metal plate via an insulating layer, and FIGS. 2C and 2D are etchings, respectively. FIG. 2 (e) and FIG. 2 (f) are a plan view and a sectional view, respectively, in which a conductive circuit is formed by etching, and FIG. 2 (g) and FIG. 2 (h) shows a plan view and a cross-sectional view of the metal base circuit board obtained after stripping the etching resist.

[0006] The etching method has a step of forming a conductive circuit by etching from a metal foil during the process. At this time, when a foil having a large metal foil is used, the upper surface of the obtained conductive circuit is formed on the conductive circuit. There is a problem that the current that can flow in the conductive circuit is limited because it is thinner than the bottom surface and the effective area of the circuit is reduced. In addition, a commonly used etching resist ink has a problem that it is partially peeled off or a pinhole is generated by being immersed in an etching solution for a long time.

FIG. 3 is a view showing a metal base circuit board manufactured by a lead frame method and steps for obtaining the same. 3A and 3B are a plan view and a cross-sectional view of a lead frame in which a circuit is formed in advance, respectively.
(C) and FIG. 3 (d) are a plan view and a sectional view, respectively, in which an insulating layer is applied to a metal plate, and FIGS. 3 (e) and 3 (f) respectively show a lead frame attached to the metal plate via the insulating layer. It is the top view and sectional drawing of the metal base circuit board obtained by attaching.

In this method, a conductor circuit formed in advance on a lead frame can be punched out by a pressing method. In this case, the side surface of the obtained circuit is substantially vertical and the effective area of the conductor circuit is increased. However, it is not possible to directly form a remote island-shaped circuit portion without a lead portion, and there is a limitation in circuit design.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a metal base circuit board in which a circuit made of a metal foil is mounted on a metal plate via an insulating layer. Wherein the conductive circuit is manufactured efficiently and with high quality.

[0010]

That is, the present invention provides a half-push-back conductive circuit in which a circuit is formed from a conductive foil by a press method, and the circuit is at least partially backfilled in a non-circuit portion of the conductive foil. A method of manufacturing a metal-based circuit board, comprising bonding a foil onto a metal plate via an insulating layer, and then removing the non-circuit portion. The method for producing a metal-based circuit board according to claim 1, wherein the conductive foil has a thickness of 0.2 to 2.0 mm. This is a method for manufacturing a circuit board. Further, the present invention is a metal-based circuit board provided with a circuit made of a conductive foil on at least one main surface of a metal plate via an insulating layer made of a resin containing an inorganic filler, A metal-based circuit board, wherein an edge of a portion in contact with the insulating layer has a radius of curvature of 0.1 mm or more.

[0011]

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

FIG. 1 is a diagram showing an example of a method for manufacturing a metal-based circuit board according to the present invention. FIG. 1 (a), FIG. 1 (b)
Are a plan view and a cross-sectional view of a half push-back conductive foil in which a circuit 3 is formed from a conductive foil by a pressing method, and the circuit is at least partially backfilled in a non-circuit portion 4 of the conductive foil. FIGS. 1C and 1D show metal base substrates each having an insulating layer 2 provided on a metal plate 1. FIGS. 1E and 1F are a plan view and a cross-sectional view, respectively, showing a state where the half push-back conductive foil is mounted on the insulating layer 2 of the metal base substrate. FIG. 1 (g),
FIG. 1H shows the present invention obtained by mechanically and physically removing the non-circuit portion 4 of the half pushback conductive foil after the states of FIGS. 1E and 1F, respectively. 1 is a plan view and a cross-sectional view of a metal base circuit board of FIG.

In the present invention, as described above, the conductive circuit 3
Is stamped out of a metal foil by press working, and then half-pushed back and adhered in a state of being embedded in the metal foil, and thereafter, portions other than the conductive circuit portion are removed. For this reason, there is a feature that the effective area of the circuit is large, and a circuit having a separated small island-shaped circuit portion, which cannot be obtained by a single operation in the conventional method, can be directly obtained.

When a half-push-back conductive foil is bonded to a metal base substrate, the metal foil is generally pressed by using a mold or pressed by using a roll. Since there is no direct contact with the substrate, it is possible to obtain a metal-based circuit board having no scratch on the circuit surface. Since there is no scratch on the circuit surface, it is possible to prevent a defective connection of an ultrasonic wire-bonding when an electronic component module is formed using the metal-based circuit board of the present invention. It is expected that a module will be obtained.

Further, in the present method, when controlling the half pushback condition in the present method, the edge of the obtained metal base circuit board on the side in contact with the insulating layer of the conductor circuit has a radius of curvature in a specific range. The present invention has been found that the insulation resistance of the above-mentioned specific range is significantly improved.

That is, the metal-based circuit board of the present invention is characterized in that the edge of the portion in contact with the insulating layer of the circuit has a radius of curvature of 0.1 mm or more. Since it has a radius of curvature of 0.1 mm or more, high and stable withstand voltage characteristics are achieved. There is no particular reason for the upper limit of the above numerical range, but it is difficult to obtain a conductive foil having a thickness exceeding 2/3 of the thickness of the conductive foil in a half pushback operation. That is,
It is preferable that the radius of curvature is not less than 0.1 mm and not more than 2/3 of the thickness of the conductive foil. The metal-based circuit board of the present invention has the above-described structure, so that electric field concentration hardly occurs on the insulating layer, and the insulating layer is hardly damaged by thermal expansion and contraction. have.

In the present invention, the metal plate 1 may be made of aluminum, iron, copper or the like, or any of alloys and composite materials thereof. Alloys are preferably used. Normal plate thickness is in the range of 1.0 to 5.0 mm.

The insulating layer 2 can be made of any material having an insulating property, for example, epoxy resin,
A resin such as a phenol resin, an unsaturated polyester resin, and a polyimide resin is used. Among them, the epoxy resin is preferably selected because of its excellent adhesion to the metal plate 1 and the conductive circuit 3. In addition to using the resin alone,
It can be used in the form of a glass cloth, one filled with various inorganic fillers in the form of powder or fiber, or a combination thereof.

Regarding the method of forming the insulating layer 2, the insulating layer 2 may be applied on the metal plate 1 or may be provided by sticking it once as a film. The inorganic filler is preferably one having high electric insulation and high thermal conductivity, such as aluminum oxide, silicon oxide, aluminum nitride, silicon nitride, and boron nitride.

The metal foil to be the conductive circuit 3 may be any one of copper foil, copper foil plated with Ni or Au, aluminum foil, or aluminum foil joined with copper foil.

In the present invention, the thickness of the metal foil is set to 0.1.
It is preferably from 2 to 2.0 mm. However, 0.2
The half-pushback conductive foil having a thickness of not more than mm is not industrially easy to obtain, and even if obtained, it is expensive. If the thickness exceeds 2.0 mm, a half-push-backed one can be obtained, but the thickness of the obtained circuit also exceeds 2.0 mm, so that it is difficult to find a practical application.

[0022]

Example 1 A copper foil having a thickness of 0.3 mm was punched out by a press method using a mold having a blade having a desired circuit shape, and a frame portion (a circuit was not punched out by the above-described operation, and a circuit was not formed) A half-push-back conductive foil was prepared by back-filling to a depth of 0.1 mm with respect to (part).

Next, an epoxy resin containing 76% by mass of aluminum oxide was applied on an aluminum plate (thickness: 3.0 mm) so as to have a thickness of 150 μm after heating and curing to prepare a metal base substrate. After sticking a half push-back conductive foil and curing by heating, a frame portion of the half push-back conductive foil was removed to prepare a metal-based circuit board. The above operation was repeated to obtain ten metal-based circuit boards, and withstand voltage characteristics, observation of the circuit surface, and dimensional difference between the upper surface and the lower surface of the circuit were evaluated. The results are shown in Table 1.

[0024]

[Table 1]

Comparative Example 1 A metal-based circuit board was manufactured by the etching method, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 2 A metal-based circuit board was manufactured by a lead frame method, and the same evaluations as in Example 1 were performed. The results are shown in Table 1.

[0027]

According to the present invention, it is possible to obtain a circuit including a remote island-shaped circuit portion, which has not been obtained conventionally, by a single operation, and has a large effective area without a dimensional difference between the upper surface and the lower surface. It is possible to stably obtain a metal-based circuit board having a circuit with a small number of scratches on the surface, and further have a specific radius of curvature at the lower edge of the circuit by adjusting manufacturing conditions, Since a metal-based circuit board having excellent withstand voltage characteristics can be obtained, it is industrially very useful.

[Brief description of the drawings]

FIG. 1 shows a metal-based circuit board according to an embodiment of the present invention;
The figure which shows the process for obtaining it. (A) and (b) are a plan view and a sectional view of a conductive foil that has been half-pushed back, respectively, and (c) and (d) are a plan view and a sectional view of a metal base substrate, respectively. (f) is a plan view and a cross-sectional view showing a state in which a half push-back conductive foil is adhered to a metal base substrate via an insulating layer, and (g) and (h) are plan views of the metal base circuit board of the present invention, respectively. It is a figure and sectional drawing.

FIG. 2 is a view showing a metal-based circuit board according to Comparative Example 1 of the etching method and steps for obtaining the same. (A),
(B) is a plan view and a cross-sectional view of the metal base substrate, respectively.
(C) and (d) are a plan view and a cross-sectional view of a metal base substrate on which an etching resist ink is printed, respectively.
(F) is a plan view and a cross-sectional view of a state where a conductive circuit is formed by etching, respectively, and (g) and (h) are a plan view and a cross-sectional view of a metal-based circuit board, respectively.

FIG. 3 is a view showing a metal-based circuit board according to a comparative example 2 formed by a lead frame method and steps for obtaining the same.
(A) and (b) are a plan view and a sectional view of a lead frame, respectively, (c) and (d) are a plan view and a sectional view of a metal base substrate, respectively, and (e) and (f) are metal base circuit boards, respectively. FIG.

[Explanation of symbols]

 1: metal plate 2: insulating layer 3: circuit portion 4: frame portion 7: etching resist 8: lead frame

Claims (4)

[Claims] 1. A half-push-back conductive foil in which a circuit is formed from a conductive foil by a press method, and the circuit is at least partially backfilled in a non-circuit portion of the conductive foil. And then removing the non-circuit portion. 2. The method according to claim 1, wherein the insulating layer is made of a resin containing an inorganic filler. 3. The method for manufacturing a metal-based circuit board according to claim 1, wherein the thickness of the conductive foil is 0.2 to 2.0 mm. 4. A metal base circuit board comprising a circuit made of a conductive foil provided on at least one main surface of a metal plate via an insulating layer made of a resin containing an inorganic filler,
A metal-based circuit board, wherein an edge of a portion of the circuit in contact with the insulating layer has a radius of curvature of 0.1 mm or more.