JPS60169187A - Metal base circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a metal-based circuit board that can be used as a circuit board.

Conventional structure and its problems In recent years, instead of so-called printed circuit boards made of phenolic resin laminated with copper foil, metal and copper foil have been used because of their good heat dissipation properties, dimensional accuracy, and mechanical strength. Wide-area base circuit boards, which are made by bonding two types of wires together with an insulating adhesive, are increasingly being used, for example, in audio frequency band power amplifier modules.

Hereinafter, a metal-based circuit board, which is increasingly being used in the conventional power amplifier module described above, will be explained with reference to the drawings.

FIG. 1 is a cross-sectional view showing the structure of the conventional metal-based circuit board, in which 1 is a metal plate made of aluminum, iron, copper, etc.;
2 is an insulation r made of an insulating adhesive mainly composed of epoxy or the like, and 3 is a copper foil pasted to the metal plate 1 with the above-mentioned insulating adhesive.

FIG. 2 is a cross-sectional view showing a circuit portion when a circuit is formed using the metal base circuit board, and 1.2.
3 is the same as in FIG. 1, but in order to form a circuit pattern, a part of the copper foil has been removed by etching.

4 is a chip component such as a resistor, capacitor, inductor, transistor, etc., 6 is an electrode thereof, 6 is a solder connecting the electrode 6 and the copper foil 3 forming a circuit pattern, and 7 is a chip component forming a circuit pattern. The parasitic capacitance formed by the insulating layer 3 interposed between the copper foil and the metal plate 10 is shown.

Comparing a circuit configured using a metal-based circuit board as described above and a circuit configured using a conventional printed circuit board using phenolic resin, it is found that the metal-based circuit board has the above-mentioned parasitic effects. There is a big difference in that a capacitance of 7 is generated.

This difference greatly affects the stability of circuit operation. In other words, in the case of a metal-based circuit board, signals are coupled to each other through parasitic capacitance in each part of the circuit, and circuit operation generally becomes unstable. This problem is particularly serious in the case of high-frequency circuits, and has been one of the obstacles in applying metal-based circuit boards to high-frequency circuits.

Generally, this problem can be solved by electrically connecting the metal plate used in the metal base circuit board and the ground part of the circuit pattern formed on the copper foil part at an appropriate position.

By the way, if this is to be achieved with a metal base circuit board having the structure shown in Figure 1A, there are two possible methods:
All of these require considerably troublesome work, are sometimes difficult to implement, and require a considerable amount of space.

(1) Remove the copper foil and insulating layer at the point where the metal plate and the ground part of the circuit pattern are to be connected using a drill, etc., fill this area with solder or conductive paste, and at the same time, fill the area with solder or conductive paste. Connect to the ground part of the surrounding circuit pattern.

(2) Drill a hole through the board in the part of the metal base circuit board where you want to connect the metal plate and the ground part of the circuit pattern using a drill, and pass a metal bolt through the hole.
By tightening the nut, the ground part of the circuit pattern and the metal plate are electrically connected.

OBJECTS OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a duck-based circuit board that can be expected to perform well even in high-frequency circuits.

Structure of the Invention The metal-based circuit board of the present invention has an insulating layer and a conductive layer selectively formed by selectively printing an insulating adhesive and a conductive adhesive on one side or both sides of a metal plate. A metal foil is laminated on top of the circuit board, and the conductive layer is used to make an electrical connection between the metal foil and the metal plate.With a simple structure, the metal plate of the metal base circuit board is formed by etching the metal foil. It can be easily electrically connected to the ground part of the circuit pattern, and even in high-frequency circuits, it can prevent instability of circuit operation due to unnecessary coupling of signals due to the parasitic capacitance between the metal foil pattern and the metal plate. We can expect great results.

A conductive layer formed from a twisted conductive adhesive generally has good thermal conductivity, so it can be expected to function as a good thermal conductive layer, for example when die-bonding the substrate part of a semiconductor IC chip. By using it as a die pad, it is possible to minimize the heat generation of the IC chip. Furthermore, the metal plate can also be used to connect a ground circuit, and in this case, the ground circuit is provided in the inner layer, resulting in a multilayer board, making it useful as a circuit board for high-density packaging.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a sectional view showing an example of the structure of a metal base circuit board according to the present invention as an embodiment of the present invention. In the figure, 8 is a metal plate, 9 is an insulating layer made of an insulating adhesive, 11 is a conductive layer made of a conductive adhesive, and 10 is a metal plate attached to the two of these insulating layers and conductive layers. It is a metal foil such as copper, and the metal plate-8 and the metal foil 10 are a conductive layer 11.
electrically connected. As a means of constructing the metal-based circuit board shown in FIG. 2, for example, a metal plate may be used.
Second, use a screen printer to print a conductive adhesive made of Button 1 powder, epoxy resin, etc., then dry it slightly, then print an insulating adhesive mainly made of epoxy resin, and then lightly A method is adopted in which the copper foil is temporarily cured by drying, the copper foil is overlaid on top of the protrusion, and the copper foil and the metal plate are pressed together using a hot press or the like. in this case,
When screen printing conductive adhesives and insulating adhesives, these adhesives must have an appropriate viscosity, but it is only necessary to adjust the amount of filler included in these adhesives, the particle size, etc. . If it is desired to impart high thermal conductivity to the insulating layer, for example, alumina powder can be used as the filler.

FIG. 4 shows a cross-sectional view of one circuit section formed using the metal base circuit board according to the present invention. In the figure, 8, 9, 10.11 are the same as those in Figure 2, but
The metal foil 1o is etched to form a circuit pattern. 12 is a chip component such as a resistor, capacitor, inductor, transistor, etc., 13 is an electrode thereof, and 14 is solder for electrically connecting the chip component and the metal i10.

As is clear from the figure, the conductive layer 11 plays the role of electrically connecting the ground portion of the circuit pattern and the metal plate.

FIG. 6 shows a semiconductor I using the metal base circuit board of the present invention.
3 is a cross-sectional view showing an example in which a C chip is mounted, and 8, 9, 10, and 11 are the same as those in FIG. 3. FIG. 1
5 is a semiconductor heavy C chip, and 16 is a wire for wire bonding. The metal foil under the semiconductor IC chip 16 is used as a die pad 7, and the metal foil wire-bonded in the vicinity is used as a wire-bonding pad, but these pads are actually plated with gold, etc. Needless to say, it is preferable to use it after proper treatment.

In this case, the conductive layer 11 under which the semiconductor IC chip is die-bonded is used not only to electrically connect the semiconductor IC chip's substray part to the ground of the metal plate, but also to prevent heat generated by the IC chip. It also plays the role of a good heat conductor, transmitting heat to the metal plate with low thermal resistance.

FIG. 6 is a sectional view showing another embodiment in which the aim of the present invention is utilized as a double-sided circuit board.

8, 9, 10.11 shown in the figure are respectively 3.4.
This is the same as that shown in FIG. 5, and by adopting such a double-sided configuration, higher density circuit packaging can be realized. Since the specific means for realizing this double-sided substrate is the same as that in the case of FIG. 2, further detailed description will be omitted.

Effects of the Invention As detailed above, according to the present invention, the simple structure allows the metal plate of the metal base circuit board to be easily and electrically connected to the ground portion of the circuit pattern formed by etching the metal foil. In addition, even in high-frequency circuits, it is possible to prevent circuit operation from becoming unstable due to unnecessary coupling of signals due to parasitic capacitance between the metal foil pattern and the metal plate. Generally, it has good heat conduction properties, so it can be used as a circuit board that has good heat dissipation properties in parts.Furthermore, by using the metal plate as a common ground part of the circuit, the metal foil can be used to ground the circuit part. Since the wiring can be omitted, the wiring pattern of the circuit section can be simplified and miniaturized, and high-density mounting of circuit components can be made possible.

The gist of the present invention also applies to double-sided circuit boards! , or can be applied to enable higher density packaging of components. Furthermore, in the case of a double-sided board configuration, the instability that occurs as a result of signal coupling based on parasitic capacitance between circuit patterns configured on both sides of the board can be eliminated by using the metal plate as a ground, resulting in a stable circuit block. can be configured.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the structure of a conventional metal-based circuit board, Fig. 2 is a cross-sectional view showing a circuit part using the same metal-based circuit board, and Fig. 3 is a metal-based circuit according to an embodiment of the present invention. A cross-sectional view of the board, FIG. 4 is a cross-sectional view of a circuit portion using the same metal base circuit board, and FIG. 6 is a cross-sectional view when a semiconductor IC chip is mounted using the same metal base circuit board.
FIG. 6 is a sectional view of a metal-based circuit board according to another embodiment of the present invention. 1...Metal plate, 2...Insulating layer, 3...
...Copper'715.4...Chip parts, 6...
Electrode of chip component, 6... Solder, 7... Parasitic capacitance, 8... Metal plate, 9... Insulating layer,
10... Metal foil, 11... Conductive layer, 1
2... Chip parts, 13... Electrodes of chip parts, 14゛°°°° panda, 16... Semiconductor IC chip, 16... Wire bond Wire for. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (1)

[Claims] An insulating layer and a conductive layer are selectively formed by selectively printing an insulating adhesive and a conductive adhesive on one or both main surfaces of a metal plate, and a metal foil is laminated thereon to form an insulating layer and a conductive layer. A metal-based circuit board characterized in that the metal foil and the metal plate are electrically connected by a layer.