Abstract:
The present invention has an object to provide a more compact semiconductor device that can be assembled with reduced parts and tasks. The semiconductor device includes a housing having a top and bottom surfaces. Surrounded within the housing is an insulating substrate with metal layers formed on both sides thereof. Also a semiconductor chip is mounted on one of the metal layer of the insulating substrate. A terminal connector extends along the top surface of the housing and is bent towards the bottom surface thereof for supplying power to the semiconductor chip. The housing has a housing through-hole extending from the top surface to the bottom surface through the housing, and the terminal connector has a terminal through-hole which are aligned with and formed coaxially with the housing through-hole.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    A related patent application is a commonly assigned Japanese Patent Application No. 2002-36457 filed on Feb. 14, 2002, which is incorporated by reference into the present patent application.  
         BACKGROUND OF THE INVENTION  
         [0002]    1) Technical Field of the Invention  
           [0003]    The present invention relates to a power semiconductor device for controlling a substantial amount of current used for electrical systems such as a motor and a heater.  
           [0004]    2) Description of Related Arts  
           [0005]    Recent industrial systems incorporated in an electric car and an elevator, in particular, have been improved in smooth motion and comfort for ride. This improvement comes significantly from contribution of power semiconductor devices that control the power (current) of such systems. In the power semiconductor devices, a substantial amount of heat is generated, which should efficiently be radiated outside of the power semiconductor device, for example, by using a radiating fin.  
           [0006]    Referring to FIGS. 8 through 10, a conventional power semiconductor device will be described hereinafter. A power semiconductor device  101  shown in FIG. 8 includes, in general, a housing  110  made of insulating material such as resin and a base plate  130  made of metal of a good thermal conductivity such as copper. The housing  110  has a bottom surface fixed on the base plate  130  by means of metal screws or adhesive (not shown). As shown in FIG. 9, the power semiconductor device  101  also includes a plurality of main terminals  111  extending from an upper surface to an inside portion of the housing  110 . The device  101  also includes an insulating substrate  115  with patterned metal layers  114   a ,  114   b  formed on both sides thereof, and a power semiconductor chip  120  mounted on the upper metal layer  114   a  by means of solder  116 . The power semiconductor chip  120  is supplied with electric power from the main terminals  111  through a plurality of metal wires  123  of metal such as aluminum. The lower metal layer  114   b  of the insulating substrate  115  is bonded on the base plate  130  through a solder  117 .  
           [0007]    In the power semiconductor device  101 , for protection of the semiconductor chip  120 , silicone gel  124  (the hatching thereof not shown for clarity) is filled over the semiconductor chip  120  and the insulating substrate  115 . The silicone gel  124  is then sealed by epoxy resin  125  deposited thereon. Lastly, a cover  126  is formed on the epoxy resin  125 .  
           [0008]    When the power semiconductor device  101  so constructed is assembled within a peripheral device, a plurality of bus bars  140 , each of which is an external conducting plate (also referred to as “conducting member”), are arranged on and connected with the main terminals by means of metal screws  145 , as shown in FIG. 9. Also, in the power semiconductor device  101 , in order to efficiently radiate undesirable heat generated by the semiconductor chip  120  outside of the power semiconductor device  101 , the base plate  130  is required to closely contact with a radiating fin  150  by means of a plurality of metal screws  147 , as illustrated by imaginary lines of FIG. 9. Therefore, according to the power semiconductor device  101 , the base plate  130  needs four through-holes  148  formed at each corner thereof for receiving metal screws  147  so as to closely contact with the radiating fin  150 .  
           [0009]    However, when the metal screws  147  are used to secure the base plate  130  on the radiating fin  150 , the housing  110  can not be extended beyond the space over the through-holes  148  of the base plate  130 . Thus, unavailable dead spaces are defined over the through-holes  148 , thereby preventing the power semiconductor device  101  from downsizing. As clearly illustrated in FIG. 8, in the actual assembly of the power semiconductor device  101  to the peripheral device, four screws  145  are required to connect two pairs of bus bars  140  with the corresponding main terminals  111 . And as above, another four screws  147  are essential to closely contact the base plate  130  with the radiating fin  150 . It is almost impossible to reduce the number of parts (screws) and tasks required for assembly.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention has an object to provide a more compact power semiconductor device, in which the base plate and the radiating fin can be secured without defining any dead space.  
           [0011]    Also, the present invention has another object to provide the power semiconductor device that can be assembled with reduced parts and tasks, in which close contact between the base plate and the radiating fin can be achieved simultaneously with connection between the bus bars and the main terminals.  
           [0012]    Further, the present invention has another object to provide the power semiconductor device, which eliminates the base plate.  
           [0013]    In particular, the present invention is to provide a semiconductor device, which includes a housing having a top and bottom surfaces, and an insulating substrate with metal layers formed on both sides thereof. The insulating substrate is surrounded within the housing. A semiconductor chip is mounted on one of the metal layer of the insulating substrate. Also, a terminal connector extends along the top surface of the housing and is bent towards the bottom surface thereof for supplying the semiconductor chip with power. In the semiconductor device, the housing has a housing through-hole extending from the top surface to the bottom surface through the housing, and also the terminal connector has a terminal through-hole which are aligned with and formed coaxially with the housing through-hole.  
           [0014]    Therefore, a fastening member (screw) extending through the housing through-hole and the terminal through-hole can be used to fasten the semiconductor device with a metal radiator, and at the same time, to realize an electrical connection between a conducting member and a terminal connector. Thus, total time required for assembly with peripheral devices and for connection between the conducting member and the terminal connector can substantially be reduced. Also, the undesirable dead spaces of the prior art are eliminated and number of parts is reduced so that the power semiconductor device of the present invention is more compact, simpler in structure, and less expensive to manufacture than the conventional power semiconductor device.  
           [0015]    Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the sprit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    The present invention more fully be understood from the detailed description given hereinafter and accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention and wherein,  
         [0017]    [0017]FIG. 1 is a schematic perspective view of a power semiconductor device according to Embodiment 1 of the present invention;  
         [0018]    [0018]FIG. 2 is a cross sectional view taken along a line II-II in FIG. 1, illustrating the power semiconductor device before assembled with the bus bars and the radiating fin;  
         [0019]    [0019]FIG. 3 is a view similar to FIG. 2, illustrating the power semiconductor device after assembled with the bus bars and the radiating fin;  
         [0020]    [0020]FIG. 4 is a top view of the power semiconductor device after assembled with the bus bars and the radiating fin;  
         [0021]    [0021]FIG. 5 is a schematic perspective view similar to FIG. 2, illustrating a power semiconductor device according to Embodiment 2 of the present invention;  
         [0022]    [0022]FIG. 6 is an enlarged cross sectional view of power semiconductor device according to Modification 1 of the present invention, illustrating the metal screws and the insulating spacer;  
         [0023]    [0023]FIG. 7 is an enlarged cross sectional view of power semiconductor device according to Modification 2 of the present invention, illustrating the metal screws and the insulating receiving member;  
         [0024]    [0024]FIG. 8 is a schematic perspective view of a power semiconductor device according to the prior art;  
         [0025]    [0025]FIG. 9 is a cross sectional view taken along a line IX-IX in FIG. 8, illustrating the power semiconductor device of the prior art after assembled with the bus bars and the radiating fin; and  
         [0026]    [0026]FIG. 10 is a top view of the power semiconductor device of the prior art after assembled with the bus bars and the radiating fin.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    Referring to the attached drawings, the details of embodiments according to the present invention will be described hereinafter. In those descriptions, although the terminology indicating the directions (for example, upper “lower”, and “vertical”) are conveniently used just for clarity, it should not be interpreted that those terminology limit the scope of the present invention. Embodiment 1.  
         [0028]    Referring now to FIGS. 1 through 4, a power semiconductor device according to Embodiment 1 of the present invention will be described hereinafter. A power semiconductor device  1  shown in FIG. 1 includes, in general, a housing  10  made of insulating material such as resin and a base plate  30  made of metal of a good thermal conductivity such as copper, which is also referred to as a supporting metal plate. The housing  10  has a bottom surface fixed on the base plate  30  by means of metal screws or adhesive (not shown). As shown in FIG. 2, the power semiconductor device  1  also includes a plurality of main terminals (also referred to as “terminal connectors”)  11 . Each of the main terminals  11  extends along and from an upper surface of the housing  10  and is bent towards the bottom surface thereof. The power semiconductor device  1  further has an insulating substrate  15  with patterned metal layers  14   a ,  14   b  formed on both sides thereof, and a power semiconductor chip  20  mounted on the upper metal layer  14   a  by means of solder  16 . The power semiconductor chip  20  is supplied with an electric power from the main terminals  11  through a plurality of metal wires  23  made of metal such as aluminum. The lower metal layer  14   b  of the insulating substrate  15  is bonded on the base plate  30  through a solder  17 .  
         [0029]    In the power semiconductor device  1 , for protection of the semiconductor chip  20 , silicone gel  24  (the hatching thereof not shown for clarity) is filled over the semiconductor chip  20  and the insulating substrate  15 . The silicone gel  24  is then sealed by epoxy resin  25  deposited thereon. Lastly, a cover  26  is formed on the epoxy resin  25 .  
         [0030]    According to the power semiconductor device  1  of the present invention, each of main terminals  11  has a terminal through-hole  2   a  extending in a vertical direction. Also, the housing  10  and base plate  30  have a housing through-hole  2   b  and a base-plate through-hole  2   c , respectively, which are aligned with and formed coaxially with the terminal through-hole  2   a  extending in the vertical direction. Therefore, the power semiconductor device  1  of the present invention, as a whole, has a through-hole  2  defined by the terminal through-hole  2   a  of the main terminal  11 , the housing through-hole  2   b  of the housing  10 , and the base-plate through-hole  2   c  of the base plate  30 .  
         [0031]    Next, referring to FIGS. 2 and 3, a process for assembly of the power semiconductor device  1  so constructed to a peripheral device will be described hereinafter. A plurality of bus bars  40  are provided, each of which is an external conducting plate (also referred to as “conducting member”). Each of the bus bars  40  also has a bus-bar through-hole  42  extending in the vertical direction and is arranged on the corresponding main terminals  11  so that the bus-bar through-hole  42  is aligned with the through-hole  2  of the power semiconductor device  1  of the present invention. On the other hand, a radiating fin  50  includes a contacting surface  51  for contacting with a bottom surface  31  of the base plate  30 . The radiating fin  50  also has a plurality of receiving members  52  such as threaded nuts, which are embedded at portions corresponding to the through-holes  2  of the power semiconductor device  1 . The radiating fin  50  is positioned beneath the power semiconductor device  1 . Each of the through-holes  42  of the bus bars  40  and the receiving members  52  of the radiating fin  50  are all aligned to the corresponding through-hole  2  of the power semiconductor device  1 . Then, a plurality of elongate fastening screws  60  made of insulating material are inserted in the through-holes  2  and  42  and in the receiving members  52  so as to connect the bus bars  40  with the housing  10  and as well as to secure the base plate  30  to the radiating fin  50 .  
         [0032]    The radiating fin  50  is secured to the base plate  30  for efficiently radiating heat generated by the semiconductor chip  20  outside of the power semiconductor device  1 , thus, it should be in close contact with the base plate  30  with an area as wide as possible. Preferably, provided between the bottom surface  31  of the base plate  30  and the contacting surface  51  of the radiating fin  50  is a grease of a good thermal conductivity (not shown) having a thickness between approximately 100  
         [0033]    microns through 200 microns.  
         [0034]    It should be noted that, in the present embodiment, the elongate fastening screw  60  is made of insulating material so that electrical connection between the main terminal  10  and the radiating fin  50  is prevented. Such insulating material includes, for example, engineering plastics and ceramics.  
         [0035]    As described above, the power semiconductor device  1  can be secured with the bus bar  40  and the radiating fin  50  by means of the single insulating screw  60  at a time. Thus, when the power semiconductor device  1  has two pairs of main terminals  11  as indicated in FIG. 1, four of the insulating screws  60  are used for assembly with the peripheral device. Therefore, comparing to the power semiconductor device according to the prior art, the number of screws to be secured are reduced in half, and the assembling task is substantially relieved. Also, in addition, the present invention eliminates the undesirable dead spaces, which would otherwise be defined at the corners over the through-holes of the base plate of the conventional power semiconductor device. Thus, a more compact power semiconductor device  1  can be realized according to the present invention.  
         [0036]    Next, referring to FIG. 5, a power semiconductor device according to Embodiment 2 of the present invention will be described hereinafter. The power semiconductor device  1  illustrated in FIG. 5 has a structure similar to that of Embodiment 1 except that it has no base plate, thus, description thereof will be provided herein focusing on the distinguishable features of Embodiment 2.  
         [0037]    According to Embodiment 2, the insulating substrate  15  also has patterned metal layers  14   a ,  14   b  formed on both sides thereof, as well as that of Embodiment 1. However, the lower metal layer  14   b  of Embodiment 2 is constructed to have an area wider than that of the insulating substrate  15  so that a stepped portion  18  is defined around the insulating substrate  15 . Meanwhile, the housing  10  of Embodiment 2 has an abutment portion  28  designed to have a size and configuration corresponding to the stepped portion  18 . Also, as above, in the power semiconductor device  1  of Embodiment 2, the base plate  30  is eliminated, thus, the insulating substrate  15  is secured directly on the housing  10  by bonding the stepped portion  18  with the abutment portion  28  with use of an appropriate adhesive (not shown).  
         [0038]    The power semiconductor device  1  so constructed has no base plate so that it can be designed thinner than that of Embodiment 1. Thus, the power semiconductor device  1  of Embodiment 2 can be even more compact in a thickness direction.  
         [0039]    Modification 1.  
         [0040]    With reference to FIG. 6, Modification 1 of Embodiment 1 will be described hereinafter, in which a fastening screw  64  made of metal and an insulating bush  65  made of insulating material are substituted for the fastening screw  60  made of insulating material of Embodiment 1. As described above, the fastening screw can be of any form if electrical connection between the main terminal  11  and the radiating fin  50  is isolated. In FIG. 6, the fastening screw  64  is made of metal, and provided between the fastening screw  64  and the bus bar  40  are a washer  65  and an insulating bush  66  made of insulating material such as engineering plastics, ceramics, and rubber. The insulating bush  66  extends downwardly beyond the main terminal  11 . Thus, the insulating bush  66  electrically isolate the metal fastening screw  64  from the main terminal  11  and the bus bar  40  so that electrical connection between the main terminal  11  and the radiating fin  50  is avoided. As a person skilled in the art can easily conceive, Modifications 1 can be applied to both Embodiments 1 and 2.  
         [0041]    Modification 2.  
         [0042]    With reference to FIG. 7, Modification 2 of Embodiment 2 will be described hereinafter, in which a metal fastening screw and an insulating receiving member made of insulating material are substituted for the insulating screw  60  of Embodiment 2. In FIG. 7, the screw  64  is made of metal, and the receiving member  54  such as a nut is made of insulating material including engineering plastics, ceramics, and rubber. The insulating nut  54  is embedded within the radiating fin  50  and bonded therein by means of appropriate adhesive (not shown) . Thus, the insulating nut  66  electrically isolate the metal fastening screw  64  from the radiating fin  50  so that electrical connection between the main terminal  11  and the radiating fin  50  is avoided.  
         [0043]    Also, Modifications 2 can basically be applied to both Embodiments 1 and 2. However, when applied to Embodiment 1, the base-plate through-holes  2   c  of the base plate  30  should be designed to have a diameter sufficiently greater than that of the metal fastening screw  64  so that connection between the metal screw  64  and the base plate  30  is avoided.