Abstract:
A semiconductor device, includes: a wiring substrate having a wiring pattern on a front surface thereof; a first semiconductor chip mounted on the front surface of the wiring substrate; a first heat radiator having a first recess housing the first semiconductor chip and making contact with the front surface of the wiring substrate and the first semiconductor chip directly or with a first insulation layer; a second heat radiator making contact with a rear surface of the wiring substrate directly or with a second insulation layer; and a first fixing member passing through the first heat radiator, the wiring substrate, and the second heat radiator, and pressing the first heat radiator and the second heat radiator to the wiring substrate.

Description:
[0001]    The entire disclosure of Japanese Patent Application No. 2007-186838, filed Jul. 18, 2007 is expressly incorporated by reference herein. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates to a semiconductor device including a wiring substrate having a semiconductor chip mounted thereto, and a heat radiator. In particular, the invention relates to a semiconductor device having high heat radiation performance and high reliability. 
         [0004]    2. Related Art 
         [0005]    Semiconductor chips, such as drivers for display panels, need to secure a sufficient heat radiation ability in being mounted on wiring substrates due to the high heat value. For example, a technique for enhancing heat radiation performance is disclosed in JP-A-2002-124607 (19 to 21 paragraphs and FIG. 2), in which the upper surface of a semiconductor chip is adhesively bonded to a metallic chassis with a heat radiation sheet interposed therebetween, and a heat radiator is fixed to the rear surface of a flexible substrate in a semiconductor device including the flexible substrate having a semiconductor chip mounted on its surface. 
         [0006]    In the technique disclosed in JP-A-2002-124607, all most all forces applied either the semiconductor chip or the metallic chassis are directed to a connected portion between the upper surface of the semiconductor chip and the metallic chassis. As a result, a connected portion between the semiconductor chip and the wiring substrate may be peeled off. 
         [0007]    In order to solve the problem, there is also a method in which the heat radiator positioned on the surface of the wiring substrate is adhesively bonded to the surface of the wiring substrate. In this case, however, a force applied either the heat radiator or the wiring substrate in the face direction is directed to wiring lines formed on the surface of the wiring substrate. As a result, the wiring lines may be peeled off from the base of the wiring substrate. 
         [0008]    In this manner, it is difficult to satisfy both the heat radiation performance and the reliability. 
       SUMMARY 
       [0009]    An advantage of the invention is to provide a semiconductor device having high heat radiation performance and high reliability. 
         [0010]    A semiconductor device of the invention includes: a wiring substrate having a wiring pattern on a front surface thereof; a first semiconductor chip mounted on the front surface of the wiring substrate; a first heat radiator having a first recess housing the first semiconductor chip and making contact with the front surface of the wiring substrate and the first semiconductor chip directly or with a first insulation layer; a second heat radiator making contact with a rear surface of the wiring substrate directly or with a second insulation layer; and a first fixing member passing through the first heat radiator, the wiring substrate, and the second heat radiator, and pressing the first heat radiator and the second heat radiator to the wiring substrate. 
         [0011]    In the device, heat generated in the first semiconductor chip is transferred to the first heat radiator directly or with the first insulation layer, and also transferred to the first and second heat radiators with the wiring substrate. Heat transferred to the first and second heat radiators is dissipated in air. Consequently, heat generated in the first semiconductor chip can be efficiently dissipated. The first heat radiator is fixed to the wiring substrate with the first fixing member. Because of the structure, a large force is not applied to the first semiconductor chip even when a force is applied to either the wiring substrate or the first heat radiator in a surface direction. As a result, it can be suppressed that the connected portion between the semiconductor chip and a wiring pattern of the wiring substrate is peeled off. 
         [0012]    The wiring substrate may be capable of being bended. The wiring board may further include a second fixing member bending the wiring substrate so that the front surface of the wiring substrate makes contact with the first heat radiator. The first heat radiator may have electrical conductivity. The front surface may have a grounding wiring line at a part thereof with which the first heat radiator makes contact by the second fixing member. In this case, the grounding wiring line is grounded by making contact with the first heat radiator, allowing a grounding structure of the grounding wiring line to be simplified. 
         [0013]    Each of the first heat radiator and the second heat radiator may have an opposing portion that faces each other and be positioned outside an end portion of the wiring substrate. One of the opposing portions of the first heat radiator and the second heat radiator may have a spacer to keep a clearance between the first heat radiator and the second heat radiator by making contact with the other of the opposing portions of the first heat radiator and the second heat radiator. In this case, it can be suppressed that a force is applied to the surface by the first heat radiator approaching to the surface of the wiring substrate. 
         [0014]    The device may further include: an opening provided to the wiring substrate; and a spacer having a protruded shape and being provided to one of the opposing portions of the first heat radiator and the second heat radiator to keep a clearance between the opposing portion of the first heat radiator and the second heat radiator by passing through the opening and making contact with the other of the opposing portions of the first heat radiator and the second heat radiator. In this case, it can also be suppressed that a force is applied to the surface by the first heat radiator approaching to the surface of the wiring substrate. 
         [0015]    It is preferable that the first heat radiator make contact with the wiring substrate with the first insulation layer, and the first insulation layer adhere to one of the first heat radiator and the wiring substrate, and do not adhere the other of the first heat radiator and the wiring substrate. In this case, a large force is not applied to the interface of the wiring pattern and the base of the wiring substrate even when a force is applied to either the wiring substrate or the first heat radiator in a surface direction. As a result, it can be suppressed that the wiring pattern is peeled off from the base. 
         [0016]    The wiring substrate may have a second wiring pattern on the rear surface thereof, a second semiconductor chip mounted on the rear surface of the wiring substrate, and a second recess provided to the second heat radiator and housing the second semiconductor chip. The second semiconductor chip may make contact with a bottom face of the second recess directly or with a third insulation layer. In this case, heat generated in the second semiconductor chip is dissipated in the same manner of heat generated in the first semiconductor chip. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]    The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
           [0018]      FIGS. 1A and 1B  are sectional views for explaining a structure of a semiconductor device according to a first embodiment of the invention. 
           [0019]      FIG. 2  is a sectional view for explaining a structure of a semiconductor device according to a second embodiment of the invention. 
           [0020]      FIG. 3  is a sectional view for explaining a structure of a semiconductor device according to a third embodiment of the invention. 
           [0021]      FIG. 4  is a sectional view for explaining a structure of a semiconductor device according to a fourth embodiment of the invention. 
           [0022]      FIG. 5  is a sectional view for explaining a structure of a semiconductor device according to a fifth embodiment of the invention. 
           [0023]      FIG. 6  is a sectional view for explaining a structure of a semiconductor device according to a sixth embodiment of the invention. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0024]    Embodiments of the invention will be described with reference to the accompanying drawings.  FIG. 1A  is a plan view of a semiconductor device according to a first embodiment of the invention.  FIG. 1B  is a sectional view taken along the line A-A′ of  FIG. 1A . A semiconductor chip  1  is mounted on the surface of a flexible substrate  10 . The mounting method is a COF method, for example. The semiconductor chip  1  is, for example, a driver for a flat panel display, such as a plasma display and a liquid crystal display, and sealed on the flexible substrate  10  with a resin  1   a.    
         [0025]    The flexible substrate  10  is composed of a base  11 , a wiring pattern  12  formed on the surface of the base  11 , and a resist layer  13  covering the wiring pattern  12 . The resist layer  13  and an insulation layer  21 , which will be described later, do not cover the wiring pattern  12  at a portion in which the semiconductor chip  1  is connected to the flexible substrate  10  and at a periphery of a screw  52 , which will de described in detail. Here, a wiring line, located at the periphery of the screw  52 , of the wiring patter  12  serves as a grounding wiring line. 
         [0026]    A first heat radiating plate  30  makes contact with the front surface of the flexible substrate  10  with an insulation layer  21  having high thermal conductivity interposed therebetween while a second heat radiating plate  40  is bonded on the rear surface of the flexible substrate  10  with a thermal conductive adhesive  22  interposed therebetween. The insulation layer  21  adheres to one of the flexible substrate  10  and the first heat radiating plate  30 , but does not adhere to the other one. The insulation layer  21  can prevent the first heat radiating plate  30  and the wiring pattern  12  from being electrically conducted even when the wiring pattern  12  is exposed due to the breakage of the resist layer  13 . 
         [0027]    A part of heat generated in the semiconductor chip  1  is transferred to the first heat radiating plate  30  and the second heat radiating plate  40  through the flexible substrate  10  and the insulation layer  21  or the adhesive  22 . The first heat radiating plate  30  is a metallic plate. The second heat radiating plate  40  is also preferably is a metallic plate. For example, aluminum or cupper is used as a metal for the plate. 
         [0028]    The second heat radiating plate  40  has a screw hole while the first heat radiating plate  30  also has a screw hole at a position overlapping with the screw hole of the second heat radiating plate  40 . The flexible substrate  10  has an opening (a hole) at a position overlapping with the screw holes. The first heat radiating plate  30  and the second heat radiating plate  40  are pressed to the flexible substrate  10  by a screw  51  inserted through the screw hole of the second heat radiating plate  40 , the hole of the flexible substrate  10 , and the screw hole of the first heat radiating plate  30 . The first heat radiating plate  30  is fixed to the flexible substrate  10 . While the screw  51  is inserted from a side adjacent to the second heat radiating plate  40 , it may be inserted from a side adjacent to the first heat radiating plate  30 . In  FIG. 1B , the screw hole formed in the first heat radiating plate  30  passes through the first heat radiating plate  30 ; however, it may not be a through hole. 
         [0029]    The second heat radiating plate  40  has an opening  41  at a portion not overlapping with the semiconductor chip  1  while the first heat radiating plate  30  has a screw hole located inside the opening  41 . The flexible substrate  10  has an opening (a hole) at a position overlapping with the screw hole. Passed through the hole of the flexible substrate  10  and the screw hole of the first heat radiating plate  30 , the screw  52  bends the flexible substrate  10 , resulting in the grounding wiring line of the wiring pattern  12  being made contact with the first heat radiating plate  30 . As a result, the grounding wiring line is grounded. The flexible substrate  10  is also fixed to the first heat radiating plate  30  with the screw  52 . Here, the diameter of the head of the screw  52  is smaller than the width or the diameter of the opening  41 . Therefore, the head of the screw  52  directly makes contact with the rear surface of the flexible substrate  10  without making contact with the second heat radiating plate  40 . 
         [0030]    The first heat radiating plate  30  has a recess  31  at a portion facing the semiconductor chip  1 . On the bottom face of the recess  31 , a thermal conductive insulation layer  1   b  is provided. The semiconductor chip  1  is housed in the recess  31  and makes contact with the bottom face of the recess  31  with the insulation layer  1   b  interposed therebetween. Such structure satisfies a relationship in which the sum of the depth of the recess  31 , the thickness of the insulation layer  21 , and the thickness of the resist layer  13  is equal to the sum of the thickness of the semiconductor chip  1  and the thickness of the insulation layer  1   b.  A part of heat generated in the semiconductor chip  1  is transferred to the first heat radiating plate  30  with the insulation layer  1   b  interposed therebetween. While the insulation layer  1   b  adheres to the bottom face of the recess  31 , but may not adhere to the semiconductor chip  1 . 
         [0031]    According to the first embodiment, the semiconductor chip  1  makes contact with the first heat radiating plate  30  with the thermal conductive insulation layer  1   b  interposed therebetween. Because of this structure, heat generated in the semiconductor chip  1  is directly transferred to the first heat radiating plate  30 . In addition, the first heat radiating plate  30  makes contact with the front surface of the flexible substrate  10  with the insulation layer  21  having high thermal conductivity interposed therebetween while the second heat radiating plate  40  makes contact with the rear surface of the flexible substrate  10  with the thermal conductive adhesive  22  interposed therebetween. Because of this structure, a part of heat generated in the semiconductor chip  1  is transferred to the first heat radiating plate  30  through the flexible substrate  10  and the insulation layer  21 , and also transferred to the second heat radiating plate  40  through the flexible substrate  10  and the adhesive  22 . Heat transferred to the first radiating plate  30  and the second heat radiating plate  40  is dissipated in air, for example. 
         [0032]    Consequently, heat generated in the semiconductor chip  1  can be efficiently dissipated. 
         [0033]    The first heat radiating plate  30  is fixed to the flexible substrate  10  with the screws  51  and  52  while the second heat radiating plate  40  is fixed to the rear surface of the flexible substrate  10  with the adhesive  22 . Because of the structure, a large force is not applied to the semiconductor chip  1  even when a force is applied to either the first heat radiating plate  30  or the second heat radiating plate  40  in the surface direction. As a result, it can be suppressed that the connected portion of the semiconductor chip  1  and the wiring pattern  12  is peeled off. This effect appears remarkably in a case where the insulation layer  1   b  does not adhere to the semiconductor chip  1 . 
         [0034]    The insulation layer  21  adheres to one of the flexible substrate  10  and the first heat radiating plate  30 , but does not adhere to the other one. Because of the structure, a large force is not directed to the interface of the wiring pattern  12  and the base  11  of the flexible substrate  10  even when a force is applied to either the flexible substrate  10  or the first heat radiating plate  30  in the surface direction. As a result, it can be suppressed that the wiring pattern  12  is peeled off from the base  11 . 
         [0035]    The grounding wiring line of the wiring pattern  12  makes contact with the first heat radiating plate  30  with screw  52 , resulting in the grounding wiring line being grounded. As a result, a simple grounding structure of a grounding wiring line can be provided. 
         [0036]      FIG. 2  is a sectional view illustrating a structure of a semiconductor device according to a second embodiment of the invention, and corresponds to  FIG. 1B  of the first embodiment. The semiconductor device of the second embodiment is nearly the same as that of the first embodiment except that the flexible substrate  10  is a double-side substrate and a semiconductor chip  2  is mounted to the rear surface of the flexible substrate  10  by a COF method. Description of the same structure as that of the first embodiment is omitted. 
         [0037]    On the rear surface of the base  11  of the flexible substrate  10 , a wiring pattern  14  is formed. The wiring pattern  14  is covered with a resist layer  15 . An insulation layer  23  having high thermal conductivity, not an adhesive, is provided to the interface of the flexible substrate  10  and the second heat radiating plate  40 . That is, in the second embodiment, the second heat radiating plate  40  is fixed to the rear surface of the flexible substrate  10  with screws  51  and  52 . The insulation layer  23  adheres to one of the flexible substrate  10  and the second heat radiating plate  40 , but does not adhere to the other one. The insulation layer  23  can prevent the second heat radiating plate  40  and the wiring pattern  14  from being electrically conducted even when the wiring pattern  14  is exposed due to the breakage of the resist layer  15 . 
         [0038]    The resist layer  15  and the insulation layer  23 , which will be described later, do not cover the wiring pattern  14  at a portion in which the semiconductor chip  2  is connected to the flexible substrate  10  and at a periphery of the screw  52 . Here, a wiring line, located at the periphery of the screw  52 , of the wiring patter  14  serves as a grounding wiring line. 
         [0039]    The semiconductor chip  2  is, for example, a driver for a flat panel display, such as a plasma display and a liquid crystal display, and sealed on the flexible substrate  10  with a resin  2   a.    
         [0040]    The second heat radiating plate  40  has a recess  42  at a portion facing the semiconductor chip  2 . On the bottom face of the recess  42 , a thermal conductive insulation layer  2   b  is provided. The semiconductor chip  2  is housed in the recess  42  and makes contact with the bottom face of the recess  42  with the insulation layer  2   b  interposed therebetween. Such structure satisfies a relationship in which the sum of the depth of the recess  42 , the thickness of the insulation layer  23 , and the thickness of the resist layer  15  is equal to the sum of the thickness of the semiconductor chip  2  and the thickness of the insulation layer  2   b.    
         [0041]    As described above, the second embodiment can provide the same advantageous effect as that of first embodiment. The semiconductor chip  2  makes contact with the second heat radiating plate  40  with the thermal conductive insulation layer  2   b  interposed therebetween. Because of this structure, heat generated in the semiconductor chip  2  is directly transferred to the second heat radiating plate  40 . In addition, a part of heat generated in the semiconductor chip  2  is transferred to the first heat radiating plate  30  through the flexible substrate  10  and the insulation layer  21 , and also transferred to the second heat radiating plate  40  through the flexible substrate  10  and the insulation layer  23 . Heat transferred to the first radiating plate  30  and the second heat radiating plate  40  is dissipated in air. 
         [0042]    Consequently, heat generated in the semiconductor chip  2  can be efficiently dissipated. 
         [0043]    The second heat radiating plate  40  is fixed to the flexible substrate  10  with screws  51  and  52 . Because of the structure, a large force is not applied to the semiconductor chip  2  even when a force is applied to any one of the flexible substrate  10 , the first heat radiating plate  30 , and the second heat radiating plate  40  in the surface direction. As a result, it can be suppressed that the connected portion of the semiconductor chip  2  and the wiring pattern  14  is peeled off. This effect appears remarkably in a case where the insulation layer  2   b  does not adhere to the semiconductor chip  2 . 
         [0044]    The insulation layer  23  adheres to one of the flexible substrate  10  and the second heat radiating plate  40 , but does not adhere to the other one. Because of the structure, a large force is not directed to the interface of the wiring pattern  14  and the base  11  of the flexible substrate  10  even when a force is applied to either the flexible substrate  10  or the second heat radiating plate  40  in the surface direction. As a result, it can be suppressed that the wiring pattern  14  is peeled off from the base  11 . 
         [0045]      FIG. 3  is a sectional view illustrating a structure of a semiconductor device according to a third embodiment of the invention, and corresponds to  FIG. 1B  of the first embodiment. A semiconductor device according to the third embodiment is the same as that of the first embodiment except that the end portions of the first heat radiating plate  30  and the second heat radiating plate  40  are positioned outside the end portion of the flexible substrate  10  and faced each other, and a spacer  43  is provided to the end portion of the second heat radiating plate  40 . Description of the same structure as that of the first embodiment is omitted. 
         [0046]    The spacer  43  is formed in such a manner that the face, facing the first heat radiating plate  30 , of the end portion of the second heat radiating plate  40  is protruded toward the first heat radiating plate  30 . The upper end face of the spacer  43  butts to the first heat radiating plate  30 . As a result, the clearance between the first heat radiating plate  30  and the flexible substrate  10  and the clearance between the second heat radiating plate  40  and the flexible substrate  10  can be kept with the spacer  43 . 
         [0047]    As described above, the third embodiment can also provide the same advantageous effect as that of the first embodiment. In addition, it can be suppressed a force is applied to the resist layer  13  by the first heat radiating plate  30  approaching to the front surface of the flexible substrate  10  because the clearance between the first heat radiating plate  30  and the flexible substrate  10  can be kept with the spacer  43 . 
         [0048]      FIG. 4  is a sectional view illustrating a structure of a semiconductor device according to a fourth embodiment of the invention, and corresponds to  FIG. 2  of the second embodiment. A semiconductor device according to the fourth embodiment is the same as that of the first embodiment except that the end portions of the first heat radiating plate  30  and the second heat radiating plate  40  are positioned outside the end portion of the flexible substrate  10  and faced each other, and the spacer  43  is provided to the end portion of the second heat radiating plate  40  in the same manner shown in the third embodiment. Description of the same structure as that of the second embodiment is omitted. 
         [0049]    The third embodiment can also provide the same advantageous effect as that of the second embodiment. In the fourth embodiment, the first heat radiating plate  30  and the second heat radiating plate  40  have the same structure as that in the third embodiment. Thus, each of the clearance between the first heat radiating plate  30  and the flexible substrate  10 , and the clearance between the second heat radiating plate  40  and the flexible substrate  10  can be kept with the spacer  43 . As a result, it can be suppressed that a force is applied to the resist layers  13  and  15  by the approach of the first heat radiating plate  30  or the second heat radiating plate  40  toward the flexible substrate  10 . 
         [0050]      FIG. 5  is a sectional view illustrating a structure of a semiconductor device according to a fifth embodiment of the invention, and corresponds to  FIG. 3  of the third embodiment. A semiconductor device according to the fifth embodiment is the same as that of the third embodiment except that the end portions of the first heat radiating plate  30  and the second heat radiating plate  40  are the same position of the first embodiment, an opening  10   a  is provided to the flexible substrate  10 , and the spacer  43  is disposed at the position overlapping with the opening  10   a  and passes through the opening  10   a  to butt to the first heat radiating plate  30 . Description of the same structure as that of the third embodiment is omitted. 
         [0051]    The fifth embodiment can also provide the same advantageous effect as that of the third embodiment. 
         [0052]      FIG. 6  is a sectional view illustrating a structure of a semiconductor device according to a sixth embodiment of the invention, and corresponds to  FIG. 4  of the fourth embodiment. A semiconductor device according to the fourth embodiment is the same as that of the fourth embodiment except that the end portions of the first heat radiating plate  30  and the second heat radiating plate  40  are the same position of the first embodiment, the opening  10   a  is provided to the flexible substrate  10 , and the spacer  43  is disposed at the position overlapping with the opening  10   a  and passes through the opening  10   a  to butt to the first heat radiating plate  30 . Description of the same structure as that of the fourth embodiment is omitted. 
         [0053]    The sixth embodiment can also provide the same advantageous effect as that of the fourth embodiment. 
         [0054]    It should be understood that the above-mentioned embodiments and examples are not intended to limit the invention. Various changes and modifications can be made without departing from the spirit and scope of the invention. For example, in the above-described embodiments, the insulation layers  21  and  1   b  may not be included. In each of the second, fourth, and sixth embodiments, the insulation layers  23  and  2   b  may not be included. In addition, the substrate on which the semiconductor chip  1  and/or  2  is mounted is not necessarily a flexible substrate. Any substrates can be used as long as the substrates can be bended by the screw  52  so that the wiring pattern  12  makes contact with the first heat radiating plate  30 . 
         [0055]    Further, in the above-described embodiments, a pin may be used instead of the screws  51  and  52 . In this case, a normal hole is formed to the first heat radiating plate  30  and the second heat radiating plate  40  instead of the screw hole.