Patent Publication Number: US-2021183730-A1

Title: Igbt module with heat dissipation structure having copper layers of different thicknesses

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates to an IGBT (Insulated Gate Bipolar Transistor) module, and more particularly to an IGBT module with a heat dissipation structure having copper layers of different thicknesses. 
     BACKGROUND OF THE DISCLOSURE 
     Most high-power inverters currently used in electric vehicles/hybrid vehicles adopt 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 to  FIG. 1  and  FIG. 2 , the conventional IGBT module with the heat dissipation structure mainly includes a layer  11 A of IGBT chips, an upper solder layer  12 A, a DBC substrate  13 A, a lower solder layer  14 A, and a heat dissipation layer  15 A. Among them, the DBC substrate  13 A includes, from top to bottom, an upper metal layer  131 A, a ceramic layer  132 A, and a lower metal layer  133 A. However, the DBC substrate is of a multilayer structure which has a limited ability of spreading heat. When heat is generated by the layer of IGBT chips, it cannot be transferred to the heat dissipation metal layer through the DBC substrate in time. Moreover, the connection between the DBC substrate and the heat dissipation metal layer can only be made through the solder layer. In practice, the entire solder layer 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 a heat dissipation structure having copper layers of different thicknesses that can overcome the aforementioned issues. 
     In one aspect, the present disclosure provides an IGBT module with a heat dissipation structure, including a first layer of chips, a second layer of chips, a first bonding layer, a second bonding layer, a first copper layer, a second copper layer, a thermally-conductive and electrically-insulating layer, and a heat dissipation layer. The thermally-conductive and electrically-insulating is disposed on the heat dissipation layer, the first copper layer and the second copper layer are disposed on the thermally-conductive and electrically-insulating layer at intervals. The first bonding layer and the second bonding layer are disposed on the first copper layer and the second copper layer, respectively. The first layer of chips and the second layer of chips are disposed on the first bonding layer and the second bonding layer, respectively. The number of chips of the first layer of chips is larger than that of the second layer of chips such that the first copper layer has a greater thickness than the second copper layer. 
     Preferably, the first copper layer has a thickness greater than 1000 μm. 
     Preferably, the second copper layer has a thickness of 200-1000 μm. 
     Preferably, the thermally-conductive and electrically-insulating layer is an epoxy-based composite, a polyimide-based composite or a PP-based composite. 
     Preferably, the thermally-conductive and electrically-insulating layer includes at least one of the following fillers: alumina, aluminum nitride, silicon nitride, silicon carbide, or boron nitride. 
     Preferably, the IGBT module with the heat dissipation structure further includes a third layer of chips, a third bonding layer and a third copper layer. The third copper layer, the first copper layer and the second copper layer are disposed on the thermally-conductive and electrically-insulating layer at intervals. The third bonding layer is disposed on the third copper layer, and the third layer of chips is disposed on the third bonding layer. The number of chips of the third layer of chips is larger than that of the first layer of chips such that the third copper layer is formed to have a greater thickness than the first copper layer. 
     These and other aspects of the present disclosure will become apparent from the following description of the embodiment taken in conjunction with the following drawings and their captions, although variations and modifications therein may be affected without departing from the spirit and scope of the novel concepts of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the following detailed description and accompanying drawings. 
         FIG. 1  is an exploded side schematic view illustrating a conventional IGBT heat dissipation structure. 
         FIG. 2  is a side schematic view illustrating a conventional IGBT heat dissipation structure. 
         FIG. 3  is an exploded side schematic view illustrating an IGBT heat dissipation structure of the present disclosure. 
         FIG. 4  is a side schematic view illustrating the IGBT heat dissipation structure of the present disclosure. 
         FIG. 5  is a side schematic view illustrating another IGBT heat dissipation structure of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     The present disclosure is more particularly described in the following examples that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. Like numbers in the drawings indicate like components throughout the views. As used in the description herein and throughout the claims that follow, unless the context clearly dictates otherwise, the meaning of “a”, “an”, and “the” includes plural reference, and the meaning of “in” includes “in” and “on”. Titles or subtitles can be used herein for the convenience of a reader, which shall have no influence on the scope of the present disclosure. 
     The terms used herein generally have their ordinary meanings in the art. In the case of conflict, the present document, including any definitions given herein, will prevail. The same thing can be expressed in more than one way. Alternative language and synonyms can be used for any term(s) discussed herein, and no special significance is to be placed upon whether a term is elaborated or discussed herein. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any terms is illustrative only, and in no way limits the scope and meaning of the present disclosure or of any exemplified term. Likewise, the present disclosure is not limited to various embodiments given herein. Numbering terms such as “first”, “second” or “third” can be used to describe various components, signals or the like, which are for distinguishing one component/signal from another one only, and are not intended to, nor should be construed to impose any substantive limitations on the components, signals or the like. 
     Referring to  FIG. 3  to  FIG. 5 , the present disclosure provides an IGBT module with a heat dissipation structure having copper layers of different thicknesses. As shown in  FIG. 3  to  FIG. 5 , the IGBT module with a heat dissipation structure having copper layers of different thicknesses in accordance with the present disclosure includes a first layer  11   a  of chips, a second layer  11   b  of chips, a first bonding layer  12   a , a second bonding layer  12   b , a first copper layer  13   a , a second copper layer  13   b , a thermally-conductive and electrically-insulating layer  14 , and a heat dissipation layer  15 . 
     The thermally-conductive and electrically-insulating layer  14  is disposed on the heat dissipation layer  15 . The heat dissipation layer  15  can be a heat sink or a heat dissipation metal plate, but is not limited thereto. The thermally-conductive and electrically-insulating layer  14  is composed of polymer composite material and can achieve the effects of insulation, 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 structure in accordance with the present disclosure does not need a solder layer but instead directly forms the thermally-conductive and electrically-insulating layer  14  on the surface of the heat dissipation layer  15 . In this way, the heat conduction performance will not be affected by the problems of empty soldering and the interface impedance of the solder layer, and an insulation failure caused by the sputtering phenomenon of the soldering will not occur. 
     In detail, the thermally-conductive and electrically-insulating layer  14  may be an epoxy-based composite. Furthermore, the thermally-conductive and electrically-insulating layer  14  may include at least one of the following fillers: alumina, aluminum nitride, silicon nitride, silicon carbide, or boron nitride. In other embodiments, the thermally-conductive and electrically-insulating layer  14  may be composed of a polyimide-based composite or a PP-based composite. Moreover, the thermally-conductive and electrically-insulating layer  14  may be bonded onto the heat dissipation layer  15  by screen-printing or hot-pressing. 
     In the present embodiment, the thermally-conductive and electrically-insulating layer  14  has a thickness of about 20-200 μm, but preferably 100 μm, to achieve better insulation and heat conduction. 
     The first copper layer  13   a  and the second copper layer  13   b  are disposed on the thermally-conductive and electrically-insulating layer  14  at intervals. The thermal-conductive and electrically-insulating layer  14  can be disposed between the first and second copper layers  13   a ,  13   b  and the heat dissipation layer  15  to create insulation there-between, and the first and second copper layers  13   a ,  13   b  can conduct heat to the heat dissipation layer  15  through the thermal-conductive and electrically-insulating layer  14 . 
     The first copper layer  13   a  and the second copper layer  13   b  may each be a thick copper block, and are formed on the thermally-conductive and electrically-insulating layer  14  by hot-pressing. 
     The first bonding layer  12   a  and the second bonding layer  12   b  are disposed on the first copper layer  13   a  and the second copper layer  13   b , respectively. Furthermore, the first layer  11   a  of chips and the second layer  11   b  of chips are disposed on the first bonding layer  12   a  and the second bonding layer  12   b , respectively. The first bonding layer  12   a  and the second bonding layer  12   b  may each be, but not limited to, a tin bonding layer, a sintered silver layer, or the like. 
     In the present embodiment, the first layer  11   a  of chips may include two IGBT chips  11   a , and the second layer  11   b  of chips may include an IGBT chip  111   b . That is, the number of chips of the first layer  11   a  of chips can be larger than that of the second layer  11   b  of chips, so that the amount of heat generated by the first layer  11   a  of chips is greater than that generated by the second layer  11   b  of chips. Therefore, the thickness of the first copper layer  13   a  is arranged to be greater than that of the second copper layer  13   b . Furthermore, the thickness of the first copper layer  13   a  may be greater than 1000 μm to significantly improve uniformity of heat dissipation and overall efficiency of heat conduction, and the thickness of the second copper layer  13   b  may be between 200 μm and 1000 μm. In this way, in addition to improving the uniformity of heat dissipation, the cost of copper materials can also be greatly reduced. 
     To meet different design requirements, the IGBT chip  111   b  of the second layer  11   b  of chips can be replaced with a diode chip with smaller heat generation. In addition, one of the IGBT chips  111   a  of the first layer  11   a  of chips may also be replaced with a diode chip with smaller heat generation. 
     The width of the first copper layer  13   a  is greater than that of the second copper layer  13   b , and the width of the first copper layer  13   a  and the second copper layer  13   b  may increase as the number of chips increases. 
     Referring to  FIG. 5 , the present disclosure provides another IGBT module with a heat dissipation structure having copper layers of different thicknesses. As shown in  FIG. 5 , the IGBT module with a heat dissipation structure having copper layers of different thicknesses in accordance with the present disclosure further includes a third layer  11   c  of chips, a third bonding layer  12   c , and a third copper layer  13   c.    
     The third copper layer  13   c , the first copper layer  13   a  and the second copper layer  13   b  are disposed on the thermally-conductive and electrically-insulating layer  14  at intervals. The third bonding layer  12   c  is disposed on the third copper layer  13   c . The third layer  11   c  of chips is disposed on the third bonding layer  12   c.    
     In the present embodiment, the number of chips of the third layer  11   c  of chips can be larger than that of the first layer  11   a  of chips, and the number of chips of the first layer  11   a  of chips can be larger than that of the second layer  11   b  of chips, so that the amount of heat generated by the third layer  11   c  of chips is greater than that generated by the first layer  11   a  of chips, and the amount of heat generated by the first layer  11   a  of chips is greater than that generated by the second layer  11   b  of chips. Therefore, the thickness of the third copper layer  13   c  is arranged to be greater than that of the first copper layer  13   a , and the thickness of the first copper layer  13   a  is arranged to be greater than that of the second copper layer  13   b.    
     In summary, the present disclosure provides an IGBT module with a heat dissipation structure having copper layers of different thicknesses. the thermally-conductive and electrically-insulating layer  14  is disposed between the copper layers and the heat dissipation layer  15 , so that the heat generated by the IGBT chips can be rapidly and uniformly transferred to the heat dissipation fins of the entire heat dissipation layer  15  via the copper layers  13  and the thermally-conductive and electrically-insulating layer  14 . Compared with the DBC substrate of the conventional IGBT heat dissipation structure, the IGBT heat dissipation structure in accordance with the present disclosure can simultaneously achieve the advantages of the uniformity of heat dissipation of the copper layer and the insulation and thermal conductivity of the thermally-conductive and electrically-insulating layer. The thermally-conductive and electrically-insulating layer  14  is formed directly on the surface of the heat dissipation layer  15  without having to go through a solder layer, so that the heat conduction performance will not be affected by the problems of empty soldering and the interface impedance of the solder layer, and the insulation failure caused by the sputtering phenomenon of the soldering will not occur. As such, the heat dissipation layer  15  can exert the maximum heat absorption and heat dissipation performance. Furthermore, through the arrangement of different copper thicknesses, the chip layer having a larger number of chips and generating a larger amount of heat can be disposed on the copper layer having a greater copper thickness. As such, the uniformity of heat dissipation and the overall efficiency of heat conduction can be significantly improved, and the chip layer having a smaller number of chips and smaller heat generation can be disposed on the copper layer having a thin copper thickness, so that the cost of copper materials can be greatly reduced. 
     The foregoing description of the exemplary embodiments of the disclosure has been presented only for the purposes of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Many modifications and variations are possible in light of the above teaching. 
     The embodiments were chosen and described in order to explain the principles of the disclosure and their practical application so as to enable others skilled in the art to utilize the disclosure and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure pertains without departing from its spirit and scope.