Abstract:
In a power semiconductor module, a semiconductor device including electrode surfaces for connection on its front side and back side is connected on its back side to a first extraction electrode through soldering; a metal surface of one side of a laminated conductor having a laminated structure in which at least two types of metals are laminated is directly, intermetallically connected to the front side of the semiconductor device; a second extraction electrode is connected to a metal surface of another side of the laminated conductor through soldering; and the laminated conductor includes a plurality of arch-like protrusions and a straight section connecting the arch-like protrusions, the straight section is connected with the front side of the semiconductor device, and the protrusions are connected with the second extraction electrode.

Description:
INCORPORATION BY REFERENCE 
       [0001]    The disclosure of the following priority application is herein incorporated by reference: Japanese Patent Application No. 2010-086094 filed Apr. 2, 2010 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a power semiconductor module, in particular a power semiconductor module preferred for a power conversion unit that converts DC power into AC power or AC power into DC power. 
         [0004]    2. Description of Related Art 
         [0005]    A power conversion unit includes a function to convert DC power supplied from a DC power supply into AC power so as to supply AC power to an AC load such as a rotating electrical machine or a function to convert AC power generated by a rotating electrical machine into DC power so as to supply DC power to a DC power supply. 
         [0006]    To serve such conversion function, the power conversion unit includes an inverter having a semiconductor device with a switching function, and, by repeating conduction and interruption of the semiconductor device, power conversion is performed from DC power to AC power or AC power to DC power. 
         [0007]    The switching semiconductor device generates heat upon switching or upon energization. Due to this, the semiconductor device is mounted on a high thermal conductivity member to form a heat dissipation structure. 
         [0008]    In particular for reducing the power conversion unit in size and cost, it is desirable to adopt a high heat dissipation structure and to reduce the area of the semiconductor device. 
         [0009]    Japanese Laid Open Patent Publication No. 2008-259267 discloses a structure in which both sides of a semiconductor device are soldered to a high thermal conductivity member so that heat is dissipated through the both sides of the semiconductor device. 
         [0010]    In addition, EP1467607 discloses a structure in which cylindrical metal is soldered on a chip and a metal plate is soldered on a top surface of the metal soldering so that heat is dissipated through both sides of a semiconductor device. 
         [0011]    In addition, Japanese Laid Open Patent Publication No. 2000-349207 discloses a structure in which a Si chip is sandwiched by a jointing member and a heat sink so as to suppress thermal stress based upon a difference in coefficient of thermal expansion. 
         [0012]    However, the stress was not sufficiently reduced inside the power semiconductor module and thus reliability was not sufficiently ensured. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention is to provide a power semiconductor module with improved reliability. 
         [0014]    A power semiconductor module according to a first aspect of the present invention, wherein: a semiconductor device including electrode surfaces for connection on its front side and back side is connected on its back side to a first extraction electrode through soldering; a metal surface of one side of a laminated conductor having a laminated structure in which at least two types of metals are laminated is directly, intermetallically connected to the front side of the semiconductor device; a second extraction electrode is connected to a metal surface of another side of the laminated conductor through soldering; and the laminated conductor includes a plurality of arch-like protrusions and a straight section connecting the arch-like protrusions, the straight section is connected with the front side of the semiconductor device, and the protrusions are connected with the second extraction electrode. 
         [0015]    According to a second aspect of the present invention, in the power semiconductor module according to the first aspect, the laminated conductor may be a conductor on which copper and aluminium are laminated, an aluminium side of the laminated conductor may be directly metal joined to the front side of the semiconductor device, and a copper side may be joined to the second extraction electrode through soldering. 
         [0016]    According to a third aspect of the present invention, in the power semiconductor module according to the first aspect, it is preferable that the front side of the semiconductor device and the metal surface of the one side of the laminated conductor are ultrasonically connected. 
         [0017]    According to a fourth aspect of the present invention, in the power semiconductor module according to the first aspect, an end of the first extraction electrode may constitute a first terminal for external connection, and an end of the second extraction electrode may constitute a second terminal for external connection. 
         [0018]    According to a fifth aspect of the present invention, in the power semiconductor module according to the first aspect, it is preferable to comprise a first cooling device that cools the power semiconductor module, wherein: the first extraction electrode and the laminated conductor are arranged on a heat receiving surface of the first cooling device through a flat plate-like insulating plate, and the second extraction electrode includes a second cooling device. 
         [0019]    According to a sixth aspect of the present invention, in the power semiconductor module according to the fifth aspect, it is preferable that the first and second cooling devices are metal conductors in which cooling fins are formed. 
         [0020]    In a power semiconductor module according to a seventh aspect, a semiconductor device including electrode surfaces for connection on its front side and back side is connected on its back side to a first extraction electrode through soldering; a metal surface of one side of a laminated conductor having a laminated structure in which at least two types of metals are laminated is directly, intermetallically connected to the front side of the semiconductor device; a second extraction electrode is connected to a metal surface of another side of the laminated conductor through soldering; the laminated conductor includes a plurality of arch-like protrusions and a straight section connecting the arch-like protrusions, the straight section is connected with the front side of the semiconductor device, and the protrusions are connected with the second extraction electrode; the first extraction electrode and the laminated conductor are arranged on a surface of one side of a flat plate-like first cooling device through a flat plate-like insulating plate, and the second extraction electrode is arranged on a surface of one side of a flat plate-like second cooling device; and a capacitor to suppress voltage variations when switching is arranged on a surface of another side of the first cooling device, and a driver board that drives switching of the semiconductor device is arranged on a top surface of the capacitor. 
         [0021]    A power conversion unit according to a eighth aspect of the present invention comprises: a power semiconductor module wherein: a semiconductor device including electrode surfaces for connection on its front side and back side is connected on its back side to a first extraction electrode through soldering; a metal surface of one side of a laminated conductor having a laminated structure in which at least two types of metals are laminated is directly, intermetallically connected to the front side of the semiconductor device; and a second extraction electrode is connected to a metal surface of another side of the laminated conductor through soldering, wherein: the laminated conductor includes a plurality of arch-like protrusions and a straight section connecting the arch-like protrusions, the straight section is connected with the front side of the semiconductor device, and the protrusions are connected with the second extraction electrode; the first extraction electrode and the laminated wiring conductor are arranged on a surface of one side of a flat plate-like first cooling device, inside of which a cooling passage is formed, through a flat plate-like insulating plate, and the second extraction electrode is arranged on a surface of one side of a flat plate-like second cooling device, inside of which a cooling passage is formed; and a capacitor to suppress voltage variations when switching is arranged on a surface of another side of the first cooling device, and a driver board that drives switching of the semiconductor device is arranged on a top surface of the capacitor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is an illustration of a semiconductor module according to an embodiment of the present invention. 
           [0023]      FIG. 2  is a connection exploded view of the semiconductor module. 
           [0024]      FIG. 3  is an illustration of the first embodiment of a double-sided cooling module. 
           [0025]      FIG. 4  is an illustration of the second embodiment of the double-sided cooling module. 
           [0026]      FIG. 5  is an illustration of the third embodiment of the double-sided cooling module. 
           [0027]      FIG. 6  is an illustration of the fourth embodiment of the double-sided cooling module. 
           [0028]      FIG. 7  is an exploded view of the semiconductor module according to the fourth embodiment. 
           [0029]      FIG. 8  is an illustration of the fifth embodiment of the double-sided cooling module. 
           [0030]      FIG. 9  is an illustration of an implementation example of an inverter using the double-sided cooling module. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0031]    The principle of the present embodiment will now be explained before an embodiment of the present invention is explained. 
         [0032]    In a double-sided cooling structure of a conventional semiconductor device, a high thermal conductivity metal is soldered onto the both sides of the semiconductor device. This causes stress concentration on a soldered section due to a difference in linear expansion coefficient between the semiconductor device and the soldered high thermal conductivity metal with increasing temperature in the semiconductor device, thereby causing a crack or the like to occur with long-term use. Because of this, the periphery of the metal is bonded with a resin so as to prevent the metal section from expanding, and the metal is brazed with ceramic to reduce an apparent coefficient of thermal expansion so as to reduce stress to the solder, thereby preventing life degradation. 
         [0033]    However, since the double-sided cooling structure is a structure in which the semiconductor device is sandwiched by metal from the both sides, stress is directly applied to the semiconductor device and the solder when assembling or implementing an inverter, and those may be cracked. 
         [0034]    In addition, production of the semiconductor device requires plating to solder the both sides, thereby making the processing more complicated than a conventional single-sided process. 
         [0035]    On the surface of the semiconductor device, there are regions of an electrode pad for switching control, an electrode pad for a current sensor or a temperature sensor, and the like. In addition to those regions, on the outer circumference of the semiconductor device, there is a region in which device voltage-resistance is ensured, and it is necessary to prevent those regions from shorting out or being contaminated. As a result, plating for soldering both sides not only increases plating cost but also reduces reliability and yield, thereby increasing cost. In addition, it has a heavy environmental load such as plating rinse water treatment. 
         [0036]    In view of those problems, the present invention is to provide a power semiconductor module having a heat dissipation structure in which the both sides of the semiconductor device are cooled by using a semiconductor device having undergone a single-sided plating process and reducing internal stress. 
         [0037]    Since the present embodiment includes the following structure, a heat dissipation structure can be achieved in which the semiconductor device constituting a power semiconductor module can be cooled on the both sides and internal stress can be reduced, using a semiconductor device having undergone a single-sided plating process. 
         [0038]    The embodiment will now be explained with reference to the attached drawings. 
         [0039]      FIG. 1  is an illustration of a semiconductor module according to the present embodiment. In addition,  FIG. 2  is a connection exploded view of the semiconductor module. 
         [0040]    A semiconductor device  40  is connected to an external extraction electrode  60  through a solder  20  on its bottom electrode, and the top control electrode of the semiconductor device  40  is connected to an external extraction electrode (control terminal)  70  through a control wire  75 . 
         [0041]    A cladding material  30  including two types of metal layers is ultrasonically connected to the top electrode of the semiconductor device. The top electrode of the high-current semiconductor device  40  is made of aluminium. The cladding material  30  is constituted with the two layers of an aluminium  33  and a copper  32 , the aluminium  33  side of which faces the top surface of the semiconductor device so as to enable ultrasonic welding. After this ultrasonic welding, an external extraction electrode  10  and the copper  32  side of the cladding material  30  are joined with a solder  21 . In addition, their exterior is solidified with a mold resin  80 . Thus, a double-sided cooling module  100  is configured in which the semiconductor device  40  can be cooled on the top side and the bottom side. The cladding material  30  is a thin flat plate whose thickness is configured to be equal to or less than 0.2 mm so as to facilitate transmission of a ultrasonic frequency to a joint interface, as in a conventional ultrasonic connection, thereby ensuring connection with the top surface of the semiconductor device  40 . 
         [0042]    Here, the cladding material  30  is constituted with an arch section  35  and a straight section  36  so that the upper side of the semiconductor device  40  can be divided into the straight section  36  to be ultrasonically connected and the arch section  35  to be connected with the solder  21 . This arch section  35  can relieve stress applied from the upper side of the semiconductor device  40 . 
         [0043]    A section of the cladding material  30  to be connected to the external extraction electrode  10  is arched so that even if, when connecting with the electrode  10 , a variation in thickness of the solder  20  causes the semiconductor device  40  to lean and thus causes a variation in height, the arch section  35  is deformed so as to accommodate the variations. This can provide a secure soldering connection between the cladding material  30  and the electrode  10 . 
         [0044]    Thus, the surface of the semiconductor device  40  and the straight section  36  of the cladding material  30  are once ultrasonically connected so as to provide a connection to reliably cool the both sides of the semiconductor device  40  compared to a conventional double-sided cooling structure, in which a surface of a semiconductor device is directly soldered. In addition, the semiconductor device  40  may undergo a conventional process. 
         [0045]    More specifically, the surface may not be provided with plating for soldering, thereby preventing an increase in cost and reduction in yield. 
         [0046]    The control terminal  70  is a terminal at which voltage for switching on or off the semiconductor device  40  is applied from the outside, and is connected with the semiconductor device  40  through the control terminal wire  75  such as an aluminium wire. While in this figure the terminal  70  is illustrated between the extraction electrodes  10  and  60  in the interests of brevity, the terminal  70  is provided on the same plane as the electrode  60  and the wiring is provided when the top surface of the semiconductor device  40  is seen, i.e., before the electrode  10  is connected with the solder  21 , as shown in  FIG. 2 . 
       First Embodiment 
       [0047]      FIG. 3  is an illustration of the first embodiment of the double-sided cooling module  100 . The top and bottom surfaces of the double-sided cooling module  100  are sandwiched by cooling fins  95  through insulating plates  90  and fixed with a fixing bracket  97 . Here, a plurality of the fixing brackets  97  are disposed so as to uniformly pressurize the double-sided cooling module  100 . 
         [0048]    The insulating plates  90  are made of ceramic such as aluminium nitride, silicon nitride, and alumina or high thermal conductivity resin. When made of ceramic, the insulating plates  90  may be brazed to the cooling fins  95 . The insulating plates  90  brazed to both the cooling fins  95  and the external extraction electrode may be used. When made of resin, the insulating plates  90  adhered to the cooling fins  95  in advance may be used. 
       Second Embodiment 
       [0049]      FIG. 4  is an illustration of the second embodiment of the double-sided cooling module  100 . As shown in the figure, the semiconductor device  40  is connected through the solder  20  to the top surface of an insulation metal board  98  in which the extraction electrodes  10  and  60  are formed on the top surface of the insulating plate  90  and a cooling metal plate  96  is brazed onto the bottom surface of the insulating plate  90 . The aluminium  33  side of the cladding material  30  is ultrasonically connected to the electrode  10  of the semiconductor device  40 . In addition, a cooling metal plate  15  is connected through the solder  21  to the copper  32  side of the cladding material  30 . This allows a current path and a cooling path of the top surface of the semiconductor device to be separated. This allows heat generation due to current flowing through the cooling path itself of the top surface of the semiconductor device  40  to be reduced. In addition, the top surface cooling structure can be achieved in a structure similar to a conventional semiconductor module. It is to be noted that the control terminal  70  is curtailed in this figure. In addition, the cooling metal plate  15  of the top surface can be replaced with an insulation metal board  98 . 
       Third Embodiment 
       [0050]      FIG. 5  is an illustration of the third embodiment of the double-sided cooling module  100 . An insulation board  98 F with fins is utilized, which is configured by brazing the electrodes  10  and  60  onto the top surface of the insulating board  90  and brazing a cooling metal plate  96 F with fins onto the bottom surface of the insulating board  90 , and the semiconductor device  40  is connected through the solder  20  to an electrode  2 . The aluminium  33  side of the cladding material  30  is ultrasonically connected to the semiconductor device  40  and the electrode  10 . In addition, the cooling metal plate  15  is connected through the solder  21  to the copper  32  side of the cladding material  30 . It is to be noted that the cooling metal plate  15  of the top surface can be replaced with an insulation metal board  98 F with fins. 
       Fourth Embodiment 
       [0051]      FIG. 6  is an illustration of the fourth embodiment of the double-sided cooling module  100 . This is an example in which the insulation board  98 F with fins are used on both sides and two switching circuits are mounted. There are external terminals of a terminal  60 P connected to a higher potential side, a terminal  60 N connected to a lower potential side, and a terminal  60 U that outputs higher potential or lower potential depending upon switching. In addition, a control terminal  10 U of the higher potential side and an output terminal  10 D of the lower potential side are provided to drive switching circuits of the higher potential side and the lower potential side. 
         [0052]      FIG. 7  is an exploded view of the semiconductor module according to the fourth embodiment. An IGBT chip  401  and a diode chip  40 D are connected with the solder  20  onto an insulation board with fins constituted by brazing the fins  96 F, the insulating board  90 , the electrodes  60 P,  60 N, and  60 U, and the control wirings  10 U and  10 D. This allows the chip back sides to be connected to the electrodes. The chip top surfaces are connected with the extraction electrodes through the cladding material  30  and connected with the insulation board  98 F with fins through the solder  21 . Thus the double-sided cooling module is configured. It is to be noted that a molding material is not shown in the figure. 
       Fifth Embodiment 
       [0053]      FIG. 8  is an illustration of the fifth embodiment of the double-sided cooling module  100 . This is an example in which the cooling metal plates  96  on which the semiconductor device  40  is brazed are used on both sides so as to cool the semiconductor device from the both sides of the chips and in which two switching circuits are mounted. There are external terminals of the terminal  60 P connected to the higher potential side, the terminal  60 N connected to the lower potential side, and the terminal  60 U that outputs higher potential or lower potential depending upon switching. In addition, there are the control terminal  10 U of the higher potential side and the output terminal  10 D of the lower potential side for switching the higher potential and lower potential sides. 
         [0054]      FIG. 9  is an illustration of an implementation example of an inverter (power conversion unit) using the double-sided cooling module  100 . A plate-like pipe unit  95  with built-in cooling fins is placed on a smoothing capacitor  110  for supplying current when switching. The extraction electrodes of the double-sided cooling module  100  are connected and fixed to a connection terminal  112 . 
         [0055]    The plate-like pipe unit  95  is fixed with the fixing bracket  97  so as to sandwich the double-sided cooling module  100 . At this time, grease with high adhesion and high heat transfer rate may be provided between the pipe unit and the module. In addition, a control terminal connector  124  connects between a control board  120  and the double-sided cooling module  100 . A switching control IC 122  is mounted on the control board  120  so as to drive a gate of the semiconductor device  40  in the double-sided cooling module. 
         [0056]    The double-sided cooling module  100  includes a circuit in which two switching semiconductor devices are connected in series and has a structure in which voltage is output from a section connected in series so that any one of the both end voltages of the series circuit can be output. For this reason, there is a wiring unit  65  to extract potential from the connected section. This wiring unit  65  is connected to a cable connected to a motor. The control board  120  is mounted with a current sensor  126  that monitors current to the motor, and transmits a monitoring result to an external microcomputer board (not shown in the figures) through a connector  128 . 
         [0057]    The smoothing capacitor module  110  includes a terminal  114  that connects a cable from a battery, which is a power supply. The smoothing capacitor module is provided with a built-in filtering reactor and a built-in discharge resistor in addition to the smoothing capacitor device. 
         [0058]    As explained above, according to the semiconductor module of the present embodiments, a conventionally processed semiconductor device (semiconductor device having undergone a single-sided plating process) is used to provide a power semiconductor module which has a heat dissipation structure to cool the both sides of the semiconductor device and can reduce internal stress. This allows a power conversion unit using a small-sized, low-cost semiconductor device to be provided. In addition, inductance of the power semiconductor module can be reduced, and an increase in volume can be suppressed. 
         [0059]    According to the above embodiments, the power semiconductor module can be improved in reliability. 
         [0060]    The above described embodiments are examples, and various modifications can be made without departing from the scope of the invention.