JP2000183474A - Metal insulating substrate for power semiconductor device and method of manufacturing the same - Google Patents

Abstract

[PROBLEMS] To improve a metal insulating substrate for a power semiconductor device so that high heat dissipation can be ensured even when a thick conductor is used for a power circuit. In a metal insulating substrate for a power semiconductor device in which an insulating layer and a power circuit conductor are laminated on a metal base, the power circuit conductor is embedded in the insulating layer with its upper surface exposed. As a manufacturing method, an insulating layer 2 is laminated in a prepreg state over the entire surface of the metal base 1, and a power circuit conductor is stacked on the insulating layer, and then a vacuum pressure press or the like is used. The circuit conductor 3 is embedded in the insulating layer 3 by applying a pressing force, and the insulating layer 2 is cured and assembled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a metal insulating substrate applied to a power semiconductor device such as an inverter device for controlling an electric motor, and a method of manufacturing the same.

[0002]

2. Description of the Related Art The power semiconductor device described above has a configuration in which a power semiconductor element and other electronic components (not shown) are mounted on a conductor pattern formed on a circuit board. There is a metal insulating substrate. As shown in FIG. 3, this metal insulating substrate is provided with an insulating layer 2 such as a filler epoxy resin (a mixture of an epoxy resin and a powder such as alumina) having enhanced thermal conductivity on a metal base (copper plate) 1 as shown in FIG. The circuit conductor 3 is formed by laminating and patterning the circuit conductor 3 thereon. In a conventional metal insulating substrate, the circuit conductor 3 is formed by electroless copper plating by a photo process or a copper foil etching method.

In this case, in a power semiconductor device having a large energizing current, it is necessary to increase the conductor cross-sectional area of the circuit conductor in order to keep the energizing resistance low. However, a circuit is formed with a limited circuit board area. In the conventional metal insulating substrate, the circuit conductor is etched using a thick copper foil in advance for the copper foil covering the substrate, or because the conductor width cannot be unnecessarily large, or about 100 to 140 μm. Another copper plate is soldered on a conductor pattern formed by etching a thin copper foil of 300 to 1000 μm corresponding to the current carrying capacity of the device.
A power circuit conductor having a thickness of about m is formed.

[0004]

By the way, in the conventional metal insulating substrate (see FIG. 3) in which a thick circuit conductor is patterned on the insulating layer as described above, a power semiconductor element mounted on the substrate is used. In addition, the heat dissipation of the circuit conductor itself is reduced.

[0005] That is, most of the heat generated by the power semiconductor element due to energization is generated by the circuit conductor 3 on which the element is mounted.
To the insulating layer 2 and the metal base 1 to radiate heat to a heat sink (not shown). The circuit conductor 3
Is transferred to the metal base 1 via the insulating layer 2.
In this case, the thick circuit conductor 3 has its lower surface in contact with the insulating layer 2 such as a filler epoxy resin having relatively high heat conductivity, but the left and right side surfaces of the circuit conductor are exposed without being in contact with the insulating layer 2. As it is, it does not function effectively as a heat dissipation surface. In a power device, after a semiconductor element or the like is mounted on a circuit board, the package is filled with a silicone gel, epoxy resin, or the like, and the electronic component is sealed with a resin. The rate is low and contributes little to heat dissipation.

It is conceivable to improve the heat dissipation of the semiconductor element by using a material having a high thermal conductivity such as a filler resin for the sealing resin. However, if a material having a high thermal conductivity is used for the sealing resin, the cost increases. Becomes

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to solve the above-mentioned problems and to improve the power semiconductor device so as to ensure high heat dissipation even when a thick circuit conductor is employed. It is an object of the present invention to provide a metal insulated substrate for use and a method for manufacturing the same.

[0008]

According to the present invention, there is provided a metal insulating substrate for a power semiconductor device in which an insulating layer and a power circuit conductor are laminated on a metal base. Are buried in an insulating layer with its upper surface exposed and laminated.

According to the above configuration, since the side surface of the thick power circuit conductor is in contact with the insulating layer having high thermal conductivity (such as filler epoxy resin), this side surface portion is also effective as a heat transfer surface. As compared with the conventional structure in which only the lower surface is in contact with the insulating layer, the heat transfer between the circuit conductor and the insulating layer is increased, and the heat dissipation of the metal insulating substrate is improved. Further, in the above configuration, the insulating layer is divided into upper and lower layers, and the power circuit conductor is buried and laminated in the upper insulating layer.
There is a configuration.

With this configuration, after the lower insulating layer is cured, the power circuit conductor is buried and laminated in the upper insulating layer laminated thereon, so that the circuit conductor embedded in the insulating layer directly contacts the metal base. There is no danger of occurrence, and a predetermined dielectric strength can be ensured by the lower insulating layer.

Here, by forming the upper layer and the lower layer of the insulating layer from the same kind of insulating material (claim 3), the adhesiveness between the upper insulating layer and the lower insulating layer is good and the thermal expansion difference is improved. An insulating layer which does not easily peel off is obtained. Further, if the upper layer and the lower layer of the insulating layer are formed of different insulating materials (claim 4),
The material of the lower and upper insulating layers is made of a metal base, a semiconductor element, an adhesive property with a sealing resin, a dielectric constant of the insulating layer,
Materials can be selected and combined in consideration of the dielectric loss tangent and the like.

The thick power circuit conductor is formed by pressing a metal plate such as a copper plate or forming a pattern by wire cutting. Circuit conductors can be manufactured in a shorter time and more easily as compared with other methods.

On the other hand, the metal insulating substrate having the above structure is manufactured by the following method according to the present invention. That is,
In the configuration in which the insulating layer is a single layer, the insulating layer is laminated on the entire surface of the metal base in an uncured state, and then the circuit conductor is turned into an insulating layer by pressing the power circuit conductor on the insulating layer. The insulating layer is buried and cured (claim 6). Further, in the configuration in which the insulating layer is divided into upper and lower layers, first, a lower insulating layer is laminated on the entire surface of the metal base, and the upper insulating layer is not formed on the entire upper surface in a state where the lower insulating layer is cured. After laminating in a cured state, the circuit conductor is embedded in the upper insulating layer by applying pressure while the power circuit conductor is superimposed on the upper insulating layer, and the upper insulating layer is cured (claim 7).

By adopting such a manufacturing method, the metal insulating substrate of the present invention in which the power circuit conductor is embedded and laminated in one or two insulating layers without relying on a complicated insert molding method or the like can be manufactured with high quality. , And can be manufactured efficiently.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.
The description will be made based on the embodiment shown in FIGS. In the drawings of the respective embodiments, the same members corresponding to FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted.

[Embodiment 1] FIG. 1 is a structural view of an embodiment according to claim 1 of the present invention. In a metal insulating substrate comprising a laminate of a metal base 1, an insulating layer 2, and a power circuit conductor 3, FIG. The power circuit conductor 3 is buried and laminated such that its upper surface is exposed and its lower surface and left and right side surfaces are buried in the insulating layer 2. Here, the insulating layer 2 is preferably made of a filler epoxy resin or the like in which a powder such as alumina is mixed into an epoxy resin to increase the thermal conductivity. The power circuit conductor 3 is formed by pressing a copper plate having a thickness of, for example, 300 μm.
Alternatively, it is formed in a predetermined pattern by a wire cutting method.

According to the above configuration, the power circuit conductor 3 has not only the lower surface but also the left and right side surfaces of the resin layer 2 having high thermal conductivity.
As a result, the heat transfer area between the circuit conductor / insulating layer is increased as compared with the conventional structure shown in FIG. 3 so that the power semiconductor element mounted on the circuit conductor 3 and the heat generated by the circuit conductor itself are reduced. Heat dissipation is improved. In the above configuration, the thickness A of the insulating layer 2 is set to be larger than the thickness B of the circuit conductor 3, and the thickness of the insulating layer corresponding to a predetermined dielectric strength between the lower surface of the circuit conductor 3 and the metal base 1. C is secured.

Next, a method of manufacturing the metal insulating substrate having the structure shown in FIG. 1 will be described with reference to FIGS. First, in the step of FIG. 4A, an insulating layer (sheet-like resin) 2 in a prepreg state, which has been cured to the B stage where the tackiness is eliminated, is applied to the entire upper surface of the metal base 1 and temporarily fixed. Next, the power circuit conductor 3 is positioned and superimposed on the insulating layer 2 temporarily fixed to the metal base 1 in the step of FIG. 4B, and is vertically moved by the vacuum press 4 in the step of FIG. Then, the circuit conductor 3 is pressed into the insulating layer 2 in a prepreg state by embedding and laminating the circuit conductor 3, and the resin of the insulating layer 2 is cured by applying heat in this state. By using the vacuum press 4 in this pressurizing and curing step, the resin of the insulating layer 2 can be cured without generating voids that cause a decrease in dielectric strength.

[Embodiment 2] FIG. 2 is a structural view of an embodiment according to a second aspect of the present invention. In this embodiment, an insulating layer 2 is formed in two upper and lower layers. The power circuit conductor 3 is buried and laminated in the insulating layer 2a, and the insulating layer 2a is laminated on the lower insulating layer 2b which is laminated on the metal base 1 and cured. In addition,
The lower insulating layer 2b is set to have a layer thickness D that ensures a predetermined dielectric strength by itself.

Here, the upper insulating layer 2a and the lower insulating layer 2b are both filler resins having a high thermal conductivity, and the insulating layers 2a and 2b are made of the same material or different materials. Can be implemented. In this case, if the same material is used for the insulating layers 2a and 2b, high adhesiveness can be obtained between the insulating layers, and there is no problem such as peeling of the bonding surface due to a difference in thermal expansion coefficient. On the other hand, if the insulating layers 2a and 2b are not limited to the same material, it is suitable for a power device in consideration of the compatibility of the metal base 1, adhesiveness with a semiconductor element, and electrical characteristics such as dielectric constant and dielectric loss tangent. The insulating material can be freely selected.

Next, a method of manufacturing the metal insulating substrate having the structure shown in FIG. 2 will be described with reference to FIGS. 5 (a) to 5 (d). First, a lower insulating layer (sheet-like resin) 2b in a prepreg state cured to the B stage is applied to the entire upper surface of the metal base 1 in the step of FIG. The layer 2b is cured. Alternatively, it is also possible to bond the sheet-shaped insulating layer 2b which has been cured in advance to the metal base 1 with an adhesive. Next, the upper insulating layer 2a in the prepreg state, which has been cured to the B stage, is applied over the entire upper surface of the insulating layer 2b in the cured state in the step of FIG. In step (c) of FIG. 5, the power circuit conductor 3 is positioned and superimposed on the insulating layer 2a. In step (d) of FIG. The insulating layer 2a in the prepreg state is pressed and buried and laminated, and in this state, heat is applied to cure the resin of the insulating layer 2a, and the upper insulating layer 2a and the lower insulating layer 2b are integrally joined. .

According to this embodiment, in the step of embedding the power circuit conductor 3 in the upper insulating layer 2a, the lower insulating layer 2a
Since b is already in a hardened state, even if the cut surface of the circuit conductor 3 is burred or turned back by press punching or the like, there is no danger that this will directly contact the metal base 1 in the buried laminated state, and the lower layer A predetermined dielectric strength can be secured by the layer thickness D of the insulating layer 2b.

[0023]

As described above, according to the present invention, in a metal insulating substrate in which an insulating layer and a power circuit conductor are laminated on a metal base, the power circuit conductor is exposed to the insulating layer by exposing its upper surface. By embedding and laminating, the heat transfer area between the circuit conductor / insulating layer increases compared to the conventional structure,
A metal insulating substrate having excellent heat dissipation for a power semiconductor device can be provided.

In addition, the insulating layer is divided into upper and lower layers, and a power circuit conductor is buried and laminated in the upper insulating layer. As a result, a stable dielectric strength can be ensured as a metal insulating substrate. The selection and combination of appropriate materials can be performed in consideration of the characteristics of the layer such as a metal base, adhesion to circuit components, and electrical properties such as dielectric constant and dielectric loss tangent.

Further, by adopting the manufacturing method of the present invention, high quality and high quality can be obtained without relying on the embedding and joining of the power circuit conductor into the insulating layer and the hardening step of the insulating layer by a complicated insert molding method. It can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a configuration sectional view of a metal insulating substrate corresponding to a first embodiment of the present invention.

FIG. 2 is a configuration sectional view of a metal insulating substrate corresponding to a second embodiment of the present invention.

FIG. 3 is a sectional view of a configuration of a conventional example of a metal insulating substrate.

4A to 4C are explanatory diagrams of a method of manufacturing the metal insulating substrate shown in FIG. 1, wherein FIGS.

5 (a) to 5 (d) are views illustrating a method of manufacturing the metal insulating substrate shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal base 2 Insulating layer 2a Upper insulating layer 2b Lower insulating layer 3 Power circuit conductor 4 Vacuum press

Claims (7)

[Claims] In a metal insulating substrate for a power semiconductor device in which an insulating layer and a power circuit conductor are laminated on a metal base, the power circuit conductor is embedded and laminated in an insulating layer with its upper surface exposed. Features Metal-insulated substrates for power semiconductor devices. 2. The metal insulating substrate for a power semiconductor device according to claim 1, wherein the insulating layer is divided into upper and lower layers, and a power circuit conductor is embedded and laminated in the upper insulating layer. 3. The metal insulating substrate for a power semiconductor device according to claim 2, wherein the upper layer and the lower layer of the insulating layer are formed of the same kind of insulating material. 4. The metal insulating substrate for a power semiconductor device according to claim 2, wherein the upper layer and the lower layer of the insulating layer are formed of different insulating materials. 5. The metal insulating substrate according to claim 1, wherein the power circuit conductor is formed by pressing and punching a metal plate.
A metal insulating substrate for a power semiconductor device, which is formed by patterning by wire cutting. 6. A step of laminating an insulating layer in an uncured state over the entire surface of the metal base, and a step of embedding a circuit conductor in the insulating layer by applying pressure while the power circuit conductor is superimposed on the insulating layer. 2. The method according to claim 1, further comprising a step of curing the insulating layer. 7. A step of laminating a lower insulating layer over the entire surface of the metal base, a step of laminating an upper insulating layer in an uncured state over the entire upper surface thereof in a state where the insulating layer is cured, and 3. The metal insulation for a power semiconductor device according to claim 2, further comprising: a step of embedding the circuit conductor in the upper insulating layer by pressing the power circuit conductor in a state where the power circuit conductor is superimposed on the power circuit conductor; and a step of curing the upper insulating layer. Substrate manufacturing method.