IGBT module with improved heat dissipation structure

An IGBT module with an improved heat dissipation structure includes a layer of IGBT chips, a bonding layer, a thick copper layer, a polymer composite layer, a thermal spray layer, and a heat dissipation layer. The thermal spray layer is disposed on the heat dissipation layer. The polymer composite layer is disposed on the thermal spray layer. The thick copper layer is disposed on the polymer composite layer. The bonding layer is disposed on the thick copper layer. The layer of IGBT chips is disposed on the bonding layer.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims the benefit of priority to Taiwan Patent Application No. 107143684, filed on Dec. 5, 2018. The entire content of the above identified application is incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to an IGBT (Insulated Gate Bipolar Transistor) module, and more particularly to an IGBT module with an improved heat dissipation structure.

BACKGROUND OF THE DISCLOSURE

Most high-power inverters currently used in electric vehicles/hybrid vehicles use IGBT (Insulated Gate Bipolar Transistor) chips. Therefore, the heat generated by the high-power inverters during operation will cause the IGBT chip temperature to rise. If no proper heat dissipation measures are incorporated, the temperature of the IGBT chip may exceed the allowable temperature, resulting in deterioration of performance and damage. Therefore, the IGBT heat dissipating efficiency has become a major problem in the industry.

At present, the direct bonded copper (DBC) substrate has become the material of choice for IGBT heat dissipation structures. Referring toFIG. 1andFIG. 2, the conventional IGBT module with the heat dissipation structure mainly includes a layer11A of IGBT chips, an upper solder layer12A, a DBC substrate13A, a lower solder layer14A, and a heat dissipation layer15A. Among them, the DBC substrate13A includes, from top to bottom, an upper metal layer131A, a ceramic layer132A, and a lower metal layer133A.

However, the DBC substrate13A has a limited ability of spreading heat. When heat is generated by the layer11A of IGBT chips, it cannot be transferred to the heat dissipation layer15A through the DBC substrate13A in time. Moreover, the connection between the DBC substrate13A and the heat dissipation layer15A can only be made through the lower solder layer14A. In practice, the entire lower solder layer14A is highly prone to experience an empty soldering phenomenon and causes an increase in interface impedance, thereby affecting the effectiveness of thermal conductivity.

SUMMARY OF THE DISCLOSURE

One objective of the present disclosure is to provide an IGBT module with an improved heat dissipation structure that can overcome the aforementioned drawbacks.

In one aspect, the present disclosure provides an IGBT module with an improved heat dissipation structure, including a layer of IGBT chips, a bonding layer, a thick copper layer, a polymer composite layer, a thermal spray layer, and a heat dissipation layer. The thermal spray layer is disposed on the heat dissipation layer. The polymer composite layer is disposed on the thermal spray layer. The thick copper layer is disposed on the polymer composite layer. The bonding layer is disposed on the thick copper layer. The layer of IGBT chips is disposed on the bonding layer.

Preferably, the thermal spray layer is composed of a ceramic material.

Preferably, the ceramic material is selected from aluminum oxide, aluminum nitride or silicon nitride.

Preferably, the thermal spray layer has a thickness of about 20-500 μm.

Preferably, the polymer composite layer is bonded onto the thermal spray layer by screen printing or hot pressing, and the thick copper layer is bonded onto the polymer composite layer by hot pressing.

Preferably, the polymer composite layer is an epoxy-based composite, a polyimide-based composite or a PP-based composite.

Preferably, the polymer composite layer includes at least one of the following fillers: alumina, aluminum nitride, silicon nitride, silicon carbide, or boron nitride.

Preferably, the polymer composite layer has a thickness of about 20-200 μm.

Preferably, the thick copper layer has a thickness equal to or greater than 1000 μm.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Referring toFIG. 3toFIG. 4, the present disclosure provides an IGBT module with an improved heat dissipation structure. As shown inFIG. 3andFIG. 4, the IGBT module with the improved heat dissipation structure in accordance with the present disclosure includes, from top to bottom, a layer11of IGBT chips111, a bonding layer12, a thick copper layer13, a polymer composite layer14, a thermal spray layer15, and a heat dissipation layer16.

The thermal spray layer15is disposed on the heat dissipation layer16. The heat dissipation layer16can be a heat sink or a heat dissipation metal plate. The thermal spray layer15is composed of a ceramic material.

In detail, the thermal spray layer15is formed by utilizing the plasma spraying process, which raises the ceramic powder from a normal temperature to a high temperature of 2500 degrees Celsius or higher by the high heat generated by a plasma torch, thereby causing the ceramic powder to be converted from a solid state to a molten liquid state. The molten ceramic is then blown by a high-velocity plasma gas, atomized, and sprayed on the surface of the heat dissipation layer16to form a thermal spray layer having a predetermined thickness. The plasma gas used in the present embodiment is argon; however, nitrogen, hydrogen, and other gases may also be used.

Furthermore, the ceramic material of the thermal spray layer15can be selected from aluminum oxide, but it can also be selected from aluminum nitride or silicon nitride. In addition, the thickness of the thermal spray layer15may be set in advance according to the spraying time of the spray coating on the surface of the heat dissipation layer16. In the present embodiment, the thermal spray layer15has a thickness of about 20-300 μm.

The polymer composite layer14, to be disposed on the thermal spray layer15, is composed of polymer composite material and can achieve the effects of heat conduction and bonding. Therefore, compared to a conventional IGBT module with a heat dissipation structure that requires a solder layer to form a connection between the DBC substrate and the heat dissipation layer, the IGBT module with the improved heat dissipation structure in accordance with the present disclosure does not need a solder layer but instead directly forms a thermal spray layer15on the surface of the heat dissipation layer16for insulation, as well as forming a polymer composite layer14on the surface of the thermal spray layer15for heat conduction and bonding. As a result, the heat conduction performance will neither be affected by the problems of empty soldering and the interface impedance of the solder layer, nor will it be affected by the multilayer structure of the DBC substrate.

In detail, the polymer composite layer14of the present embodiment may be an epoxy-based composite. The polymer composite layer14may be bonded onto the thermal spray layer15by screen printing or hot pressing. Furthermore, the polymer composite layer14may include at least one of the following fillers: alumina, aluminum nitride, silicon nitride, silicon carbide, or boron nitride.

In other embodiments, the polymer composite layer14may be composed of a polyimide-based composite or a PP-based composite.

In the present embodiment, the polymer composite layer14has a thickness of about 10-200 μm (preferably 100 μm) to achieve better heat conduction and bonding.

The thick copper layer13is disposed on the polymer composite layer14to achieve a good bond between the thick copper layer13and the thermal spray layer15through the polymer composite layer14.

In detail, the thick copper layer13is preferably bonded onto the polymer composite layer14by hot pressing, so that the thick copper layer13can have a greater thickness.

In the present embodiment, the thickness of the thick copper layer13shall be at least greater than 1000 μm. Therefore, compared to the thickness of about 300 μm for the thin copper layer of the DBC substrate for the heat dissipation structure of the conventional IGBT module, the improved heat dissipation structure of IGBT module of the present disclosure can increase the uniformity of the heat dissipation structure and the overall heat conduction efficiency through the thick copper layer13.

In addition, the thick copper layer13of the present embodiment may be composed of a thick copper plate or a thick copper block, which is bonded onto the polymer composite layer14by hot-pressing.

The bonding layer12is disposed on thick copper layer13, and a layer of IGBT chips11is disposed on the bonding layer12. The bonding layer12can be a tin bonding layer, but it can also be a sintered silver layer.

The layer11of IGBT chips111may include one or more IGBT chips111. In addition, the one or more IGBT chips111are bonded onto the thick copper layer13through the bonding layer12. The heat generated by the one or more IGBT chips111can be conducted to the heat dissipation layer16by the thick copper layer13, the polymer composite layer14and the thermal spray layer15to be dissipated outward.

In summary, the IGBT module with the improved heat dissipation structure in accordance with the present disclosure forms the thick copper layer13, the polymer composite layer14and the thermal spray layer15to rapidly and uniformly conduct the heat of the IGBT chips to the heat dissipation fins of the heat dissipation layer16. Compared with the DBC substrate for the heat dissipation structure of the conventional IGBT module, the IGBT module with the improved heat dissipation structure in accordance with the present disclosure can simultaneously achieve the advantages of the heat dissipation uniformity of the thick copper layer13and the insulation and thermal conductivity of the thermal spray layer15. Moreover, there is no need to have a solder layer, but instead the thermal spray layer15and the polymer composite layer14that has good bonding properties are directly formed on the surface of the heat dissipation layer16. As such, the heat conduction performance will neither be affected by the problems of empty soldering and the interface impedance of the solder layer, nor will it be affected by the multilayer structure of the DBC substrate, thereby making the heat dissipation layer16capable of having maximum heat absorption and heat dissipation performances.