JPH0831546B2 - High power circuit board and hybrid integrated circuit thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention has a circuit having an aluminum foil on the uppermost layer of a circuit board, is stable in withstand voltage, and is excellent in the bondability of an aluminum wire. The present invention relates to a high-power circuit board of a power module represented by an inverter having a current circuit and a hybrid integrated circuit thereof.

(Prior Art) As a hybrid integrated circuit board for a power module, a large current circuit has recently been developed by forming a thick copper foil on an insulating layer of a metal board, particularly an aluminum board. . As a method of forming a circuit made of this thick copper foil,
There are two methods: a method of forming a circuit by etching using a copper foil having a thickness of 35 μm or more, and a method of forming a thick portion by making a plating on a portion of a thin copper foil having a large current circuit of 10 μm to be a large current circuit.

However, in any of these methods, the completed circuit board has a structure in which a thick copper foil is formed on a metal plate, for example, an aluminum plate via an insulating layer, 1). Due to the difference in the expansion coefficient between the metal substrate and the copper foil, heat insulation causes cracks in the insulating layer 2). Thick copper foil is generally an electrolytic copper foil, which has a long electrolytic plating time,
That is, there are protrusions of several tens of μm on the surface that adheres to the insulating layer,
These protrusions locally reduce the thickness of the insulating layer, causing defective withstand voltage 3). When a thick rolled copper foil is used, it has a drawback that a step of roughening the foil surface is required in order to improve the adhesiveness with the insulating layer.

(Problems to be Solved by the Invention) The present invention is to solve such a drawback, and forms a layer in which an aluminum foil, a thick copper foil and an aluminum foil are laminated in this order on an insulating layer on a metal substrate. As a result, the adhesive strength with the insulating layer increases and becomes stable, and the heat shock caused by the difference in the expansion coefficient between the metal substrate and the copper foil is mitigated, preventing the insulating layer from being damaged and lowering the withstand voltage of the insulating layer. Furthermore, since the uppermost layer of the circuit board is aluminum foil, a high-power circuit board and a hybrid integrated circuit thereof which can easily perform wire bonding with an aluminum wire have been completed.

(Means for Solving Problems) That is, the present invention is as follows: 1. An aluminum foil, a copper foil having a thickness of more than 35 μm, and an aluminum foil layer are laminated in this order on a metal substrate through a good heat conductive insulating layer. Circuit board for high power with each circuit formed 2. Aluminum foil, copper foil with a thickness of more than 35 μm, and aluminum foil layer are laminated in this order on the metal substrate through a good heat conductive insulating layer to form the circuit respectively. A high-power hybrid integrated circuit in which a semiconductor is arranged on a formed circuit board and the semiconductor and an aluminum circuit are connected by an aluminum wire, and 3. An aluminum foil, 35 μm, through a good heat conductive insulating layer on a metal substrate. A semiconductor is placed on a circuit board formed by laminating layers of copper foil and aluminum foil in the order above to form a circuit, and the semiconductor and the aluminum circuit are connected to each other by an aluminum wire. A high-power hybrid integrated circuit in which terminals are connected and the circuit is sealed with a gel silicon resin and an epoxy resin composition.

 The present invention will be described in detail below.

1 (a) and 1 (b) are a plan view and a sectional view of an embodiment showing a circuit board of the present invention. First, on the metal substrate 6, the aluminum circuit part 2 for stabilizing the withstand voltage is formed as the lowermost layer through the insulating layer 5, the thick copper circuit part 1 for the large current circuit is formed as the intermediate layer, and the aluminum bonding is formed of the aluminum foil as the uppermost layer. The posts 3 are stacked. Further, as shown in the plan view of (a), an external lead terminal soldering portion 4 for mounting the external lead terminal locally is provided on the thick copper circuit. As a method of forming a circuit in the three-layer foil laminated body portion using a different metal composite foil, 1) aluminum, thick copper, and a clad foil in the order of aluminum, and 2) copper plating on the aluminum foil. To form a thick foil and further lay an aluminum foil on the thick foil. 3) Copper is sequentially plated on the aluminum foil via zinc or nickel to form a foil, and aluminum is laid on the foil. A circuit can be formed by etching a substrate in which any one of composite foils is laminated on an insulator.

As the metal substrate 6 used in the present invention, aluminum, copper, iron and their alloys having good thermal conductivity are used. Further, the insulating layer 5 having good thermal conductivity is made of, for example, 60% good thermal conductive inorganic filler such as alumina, beryllia, boron nitride, magnesia, silica and aluminum nitride.
It is a thermosetting resin or the like containing at least wt%, and the thickness thereof is preferably as thin as the withstand voltage allows, and usually 20 μm or more is required.

Further, the thickness of the thick copper foil portion 1 of the dissimilar metal composite foil used in the present invention is more than 35 μm, preferably 45 μm to 1500 μm, and more preferably 50 μm to 300 μm. If the wall thickness is 35 μm or less, a satisfactory high-current carrying capacity cannot be obtained, and there is no upper limit, but it is 1500 μ as a normal hybrid integrated circuit.
The limit is about m.

Next, FIGS. 2A and 2B are a plan view and a sectional view of an embodiment showing a high power hybrid integrated circuit of the present invention. The circuit board used as the high power hybrid integrated circuit is This is shown in FIG. First, FIGS. 2 (a) and 2 (b) show that a metal foil 6 is laminated with a composite foil composed of a dissimilar metal foil mainly composed of an aluminum foil and a copper foil with an insulating layer 5 interposed therebetween. A stabilizing aluminum circuit portion 2, a heavy current circuit thick copper circuit portion 1 and an aluminum bonding post 3 are formed respectively.

Further, a eutectic solder 10 is provided locally in the thick copper circuit portion 1, and the solder 10 allows semiconductors such as power transistors 7 and other heating elements such as transistors, FETs and ICs.
Specifically, the diode 8 is mounted. Further, these power transistors 7 and diodes 8 are connected to the aluminum bonding posts 3 by aluminum wires 9 to form a circuit. Next, in FIG. 3, after connecting the external lead terminals 11 with the external lead terminal soldering portions 4 of the circuit shown in FIG. 2, the periphery of the circuit is covered with the package 12, and the upper layer from the insulating layer 5 to the upper end of the package 12. FIG. 3 is a cross-sectional view of a circuit sealed with a gel-type silicone resin 13 and an epoxy resin composition 14.

Next, the gel-like silicone resin 13 that seals the circuit may be, for example, a silicone resin alone or a filler-containing silicone resin having good thermal conductivity. Further, the epoxy resin composition 14 is not limited as long as it is a composition having moisture resistance and low stress.

That is, the substrate used for the hybrid integrated circuit of the present invention is basically a three-layer structure of an aluminum foil, a thick copper foil, and an aluminum foil, and both metals are exposed. Since there is a circuit made of thick copper foil, the current capacity is sufficient and a large current can flow. Further, since the portion to which the heating element is fixed is also made of thick copper foil, soldering the heating element also serves as a heat spreader.

(Example) Hereinafter, a detailed description will be given with reference to an example.

Example 1 As a circuit board shown in FIGS. 1 (a) and 1 (b), an insulating layer of an epoxy resin composition containing 65% by weight of silica was applied to a thickness of 150 μm on a metal substrate made of 3 mm of aluminum.

Next, a different metal composite foil was laminated on the insulating layer in the order of 40 μm aluminum foil, 85 μm copper foil, and 40 μm aluminum foil layer to form a circuit board. The withstand voltage of this circuit board was AC5KV for 1 minute or more for all the samples (n = 50). Furthermore, the withstand voltage after 100 times of repeated heat shock at -40 ° C for 30 minutes and 120 ° C for 30 minutes was AC5KV for 1 minute or more for all the samples.

Example 2 A circuit board was obtained by performing the same operation as in Example 1 except that the insulating layer was 100 μm and the copper foil was 105 μm. The withstand voltage of this circuit board was AC3KV for 1 minute or more for all the samples (n = 50). Furthermore, the withstand voltage after 100 times of repeated heat shock at -40 ° C for 30 minutes and 120 ° C for 30 minutes was AC3KV for 1 minute or more for all the samples.

Example 3 Using the same circuit board as in Example 1, first, a solder paste was printed by screen printing on the portions (terminal mounting portions, power transistor and diode mounting portions) where soldering was required on this circuit board. Next, six 8 × 8 × 0.2 mm power transistors and six 1.5 × 1.5 × 0.2 mm diodes were placed at the locations shown in FIG. 2 and soldered through a solder reflow oven.

Next, using a thick aluminum wire having a diameter of 400 μm, wire bonding was performed from this power point wanister to an aluminum bonding post by an ultrasonic vibration method. Similarly, wire bonding was done from the power transistor to the diode.

Next, after soldering the 14 external lead terminals, the package was covered with a circuit, and silicon resin was injected until the aluminum wire and the power transistor could be covered as shown in FIG. 3 and cured to form a gel.

Then, the epoxy resin composition was injected from above and cured.

Through the above steps, a high power power module (inverter) for controlling a motor having the electric circuit shown in FIG. 4 was completed. Since this inverter is a collector-insulated type, installation was easy and the allowable current could be set to 30A.

Comparative Example An aluminum substrate and an insulating layer were formed with the same thickness as in Example 1, and the copper foil was first placed on the insulating layer.
The same thick copper foil and aluminum foil were overlaid. However, the copper foil surface of this composite foil is subjected to surface treatment by electrolytic copper plating in order to improve the adhesiveness. Regarding the withstand voltage of this circuit board, 3 of the samples (n = 50) were defective at AC2KV for 1 minute. Further, the same heat shock test as in Example 1 was conducted on the remaining non-defective products (n = 47). As a result, four more products became defective in the test for 2 minutes AC2VV.

(Effects of the Invention) As described above, according to the present invention, a thick copper foil as a circuit board is laminated on the insulating layer on both sides to form an insulating layer and a dissimilar metal composite foil. The adhesiveness is stable and the withstand voltage is also stable, and it is possible to prevent cracking of the circuit board insulating layer caused by the difference in expansion coefficient between the thick copper foil and the metal substrate. Further, since the uppermost layer of the circuit board is formed of aluminum foil, it has an advantage that the wire bonding property of the aluminum wire can be easily performed.

[Brief description of drawings]

1A and 1B are a plan view and a cross-sectional view showing a circuit board before mounting. Next, FIGS. 2 (a) and 2 (b) are a plan view and a cross-sectional view of a high-power hybrid integrated circuit of the present invention, and FIG. 3 is a cross-section of an integrated circuit in which the integrated circuit of FIG. 2 is resin-sealed. The figure is shown. FIG. 4 is an electric circuit diagram. Reference numeral 1 ... thick-walled copper circuit part, 2 ... aluminum circuit part,
3 ... Aluminum bonding post, 4 ... External lead terminal soldering part, 5 ... Insulating layer, 6 ... Metal board, 7
…… Power transistor, 8 …… Diode, 9 ……
Aluminum wire, 10 …… eutectic solder, 11 …… External lead terminal, 12 …… Package, 13 …… Gel-like silicone resin, 14 …… Epoxy resin composition

Claims (3)

[Claims] 1. A high-power circuit board in which a circuit is formed by laminating an aluminum foil, a copper foil having a thickness of more than 35 μm, and an aluminum foil layer in this order on a metal substrate via a good heat conductive insulating layer. . 2. A semiconductor is placed on a circuit board formed by laminating an aluminum foil, a copper foil having a thickness of more than 35 μm, and an aluminum foil layer in this order through a good heat conductive insulating layer on a metal substrate to form a circuit. A hybrid integrated circuit for high power, which is arranged, and the semiconductor and an aluminum circuit are connected by an aluminum wire. 3. A semiconductor is formed on a circuit board formed by laminating an aluminum foil, a copper foil having a thickness of more than 35 μm, and an aluminum foil layer in this order on a metal substrate via a good heat conductive insulating layer to form a circuit. A hybrid integrated circuit for high power, which is arranged, an external terminal is connected to a circuit in which the semiconductor and an aluminum circuit are connected by an aluminum wire, and the circuit is sealed with a gel silicon resin and an epoxy resin composition.