JP4672902B2 - Power semiconductor module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power semiconductor module formed by soldering chip components such as a power semiconductor chip and a chip resistor in one module.
[0002]
[Prior art]
FIG. 4 shows a cross-sectional view of a conventional power semiconductor module, and the conventional structure will be described with reference to FIG. One surface of the metal substrate 1 is covered with the electrical insulating layer 2 having the copper circuit 3 formed on the surface, the chip component 4 is fixed to the land 5 of the copper circuit 3 with the solder 8, and the circuit board 11 is completed. A power semiconductor module which is enclosed by a resin case 21 and filled with a sealing material 22 such as an epoxy resin from above is used for power control and the like. A gap 6 sandwiched between the lower part of the chip component 4 and the electrical insulating layer on the metal substrate is filled with air having poor heat conductivity. The path through which the heat generated by the chip component 4 is mainly released by heat conduction is the heat conduction to the solder 8, the land 5, the electrical insulating layer 2, and the metal substrate 1 below the fine cross section, and from the metal substrate to the outside. It was released. When the electric power supplied to the power semiconductor module increases, the heat generated inside increases, the temperature of the solder 8 at the connection part of the chip component increases, and the temperature difference between energized and stopped increases, causing solder cracks. As a result, the connection was poor and the reliability was reduced.
[0003]
[Problems to be solved by the invention]
In a power semiconductor module that conducts a large amount of power, solder cracks are likely to occur and the life is shortened. Therefore, it is an object of the present invention to provide a power semiconductor module in which the generated heat is effectively released.
[0004]
[Means for Solving the Problems]
We focused on minimizing the thickness of the air layer with poor thermal conductivity in order to effectively release the heat generated from the chip components. A power semiconductor module in which chip parts are soldered to copper circuit lands provided on an electric insulating layer on a metal substrate, surrounded by a resin case, and a sealing material is injected and cured inside the resin case In this case, at a middle position between a pair of opposing lands, a high thermal conductivity electrical insulating member is pressed into a gap sandwiched between the electrical insulating layer below the copper circuit and the chip component from the surface of the chip component. A heat conduction path was formed directly on the metal substrate, and heat was released in addition to the conventional heat conduction path.
[0005]
With respect to claim 2, the high thermal conductivity electrical insulating member is formed of a rubbery organic compound having elasticity or a rubbery organic compound kneaded with an inorganic substance so as to be in close contact with the chip component and the component mounting substrate. It was set as the member made. Organic compounds that are solid electrical insulators have a higher thermal conductivity than air. Inorganic materials such as silicon carbide have high thermal conductivity, and knead them with silicon rubber to obtain an elastic, high thermal conductivity electrical insulating member that is sandwiched between the chip component and the component mounting substrate. And an effective heat transfer path is formed.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
One embodiment of the present invention will be described with reference to FIG. 1 and FIG. A copper circuit 3 is formed on the metal substrate 1 via an electrical insulating layer 2, and lands 5 to which chip components 4 are soldered are provided in the copper circuit. When cream solder is printed and applied to the land, the part of the chip component is locally heated by irradiating the light beam to the part placed on the cream solder, the solder is melted, and the irradiation is stopped and cooled. When the solder 8 is hardened and then bonded to the necessary portion with the bonding wire 7, the circuit is connected and the circuit board 11 is completed. This circuit board is fixed by being surrounded by a resin case 21 so as to be the bottom, and a sealing material 22 such as epoxy resin is injected from above to be cured by heating. The power semiconductor module formed in this way increases the amount of internal heat generated as the power used increases. Therefore, in order to dissipate this heat effectively, the following steps are required before the chip component is fixed to the copper circuit. Do. Between the pair of lands 5 and lands 51 to which the chip component 4 is fixed, a rubber-like organic compound and a high thermal conductivity inorganic material such as silicon carbide or beryllia ceramics are kneaded into a sheet shape. The chip component is placed so as to sandwich the insulating member 9 (hereinafter referred to as the heat transfer member 9), the land solder solder is irradiated with a light beam and heated, and the soldering is completed. An elastic heat transfer member 9 is sandwiched in the gap 6 between the lower part of the fixed chip component 4 and the circuit board, and the temperature rise of the chip is lower than that in the case where the conventional heat transfer member 9 is not provided. This contributed to improving the life and reliability of semiconductor modules.
[0008]
In another embodiment, as shown in FIG. 3, the electrical insulating layer 2 fixed on the metal substrate 1 is beryllia ceramics, has a thermal conductivity of 0.58, and the thermal conductivity of alumina is 0. 8 times higher than 0.070. (The unit of thermal conductivity is kilocalories / square centimeters · seconds · ° C) Focusing on mounting chip components in contact with such electrical insulators, electrical insulation of beryllia ceramics on metal substrate 1 A copper circuit 3 is formed via the layer 2, and a component mounting table 10 having a height corresponding to the thickness of the copper circuit is formed on the electrical insulating layer 2. The chip component 4 is placed on the component mounting table and soldered to the land 5. Cream solder may be printed on the lands, and the entire substrate on which the chip component terminals are placed on the cream solder may be heated. Since the insulator is only inorganic and can withstand high temperatures, Irradiation does not require local heating. After that, when bonding is performed to a necessary portion with the bonding wire 7, the circuit is connected and the circuit board 11 is completed. The circuit board 11 is surrounded and fixed by a resin case 21 so as to be the bottom, and a sealing material 22 such as an epoxy resin is injected from above to be cured by heating.
In order to reduce the dimensional accuracy and reduce the cost in the embodiment shown in FIG. 3, since a gap is formed on the component mounting table 11 with which the chip component 4 is in direct contact, a capillary phenomenon such as silicon oil is formed in the gap. It is also effective to fill a heat-resistant liquid that is sucked up and held in
[0010]
【The invention's effect】
Conventionally, the thermal conductivity was improved for the part where air was thermally insulated in the gap between the chip component and the circuit board, so the module circuit board size with the same power capacity as before could be reduced. As a result, costs were reduced and resources were saved. Since the temperature of the chip components can be kept low, it contributes to the improvement of the lifetime and reliability of the entire semiconductor module.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of the present invention.
FIG. 2 is an enlarged view of a main part showing an embodiment of the present invention.
FIG. 3 is a cross-sectional view showing another embodiment of the present invention.
FIG. 4 is a cross-sectional view showing the structure of a conventional circuit device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal substrate 2 Electrical insulation layer 3 Copper circuit 4 Chip component 5 Land 6 Gap 7 Bonding wire 8 Solder 9 High thermal conductivity electrical insulation member (heat transfer member)
DESCRIPTION OF SYMBOLS 10 Component mounting base 11 Circuit board 21 Resin case 22 Sealing material 51 Land

Claims (2)

 A power semiconductor module in which chip parts are soldered to copper circuit lands provided on an electric insulating layer on a metal substrate, surrounded by a resin case, and a sealing material is injected and cured inside the resin case In the above, a high thermal conductive electrical insulation member is press-fitted into a gap sandwiched between the electrical insulation layer below the copper circuit and the chip component at an intermediate position between a pair of opposed lands. Power semiconductor module.  2. The power semiconductor module according to claim 1, wherein the high thermal conductivity electrically insulating member is a member formed of a rubbery organic compound having elasticity or a rubbery organic compound kneaded with an inorganic substance.

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