Patent Publication Number: US-2023163049-A1

Title: Semiconductor device and method for manufacturing the same

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a semiconductor device and a method for manufacturing the same. 
     Description of the Background Art 
     A conventional semiconductor device includes a lead frame having a shape disclosed in, for example, Japanese Patent Application Laid-Open No.  2004 - 63688 . 
     A semiconductor device, before transfer molding, that is, before a part of a lead frame is covered with an insulating sealing resin, is in a state where respective components, such as the lead frame and a metal wire, are exposed. Therefore, the conventional semiconductor device has had a problem that deformation of the lead frame, deformation of the metal wire, breakage of a metal wire bonding portion due to vibration, or the like may occur when handled in its manufacturing steps. When such deformation or breakage occurs, a short circuit may occur between different electrodes, resulting in a challenge to quality assurance of the semiconductor device. 
     A mold resin to be used in the transfer molding generally contains epoxy as a main component, and is a black opaque resin for heat resistance and a reduction in internal stress. Therefore, it has been difficult to confirm the above deformation or breakage after the transfer molding, and it has taken a lot of verification time to select a defective product and a deteriorated product. 
     As described above, the conventional semiconductor device has room for improvement in quality. 
     SUMMARY 
     An object of the present disclosure is to provide a semiconductor device capable of improving quality and a method for manufacturing the same. 
     A semiconductor device according to the present disclosure includes: a lead frame having a plurality of die pad portions electrically independent from each other; a semiconductor element provided on each of the die pad portions; a wire electrically connecting the semiconductor element and the lead frame; an epoxy-based resin provided on at least a part of the lead frame; and a sealing resin covering at least each of the die pad portions, the semiconductor element, the wire, and the epoxy-based resin. 
     According to the present disclosure, quality of the semiconductor device can be improved. 
     These and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the present disclosure when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view illustrating an example of an external appearance of a semiconductor device according to a first preferred embodiment; 
         FIG.  2    is a cross-sectional view taken along line A-A of  FIG.  1   ; 
         FIG.  3    is a view illustrating an example of a manufacturing step of the semiconductor device according to the first preferred embodiment; 
         FIG.  4    is a view for explaining a step of coating an epoxy-based liquid resin according to the first preferred embodiment; 
         FIGS.  5  to  7    are views each illustrating an example of a manufacturing step of the semiconductor device according to the first preferred embodiment; 
         FIG.  8    is a cross-sectional view illustrating an example of a configuration of a molding apparatus according to the first preferred embodiment; 
         FIG.  9    is a top view illustrating the example of the configuration of the molding apparatus according to the first preferred embodiment; 
         FIG.  10    is a cross-sectional view illustrating an example of the configuration of the molding apparatus according to the first preferred embodiment; 
         FIG.  11    is a top view illustrating the example of the configuration of the molding apparatus according to the first preferred embodiment; 
         FIG.  12    is a view illustrating an example of a configuration of a semiconductor device according to a second preferred embodiment; 
         FIG.  13    is a view illustrating an example of a configuration of a semiconductor device according to a third preferred embodiment; and 
         FIG.  14    is a cross-sectional view illustrating an example of a configuration of a semiconductor device according to a fourth preferred embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Preferred Embodiment 
     &lt;Configuration&gt; 
       FIG.  1    is a schematic view illustrating an example of an external appearance of a semiconductor device  1  according to a first preferred embodiment.  FIG.  2    is a cross-sectional view taken along line A-A of  FIG.  1   . 
     As illustrated in  FIG.  2   , the semiconductor device  1  includes a lead frame  2 , a die pad portion  3 , a power semiconductor element  4 , an IC chip  5 , a bonding material  6 , a metal wire  7 , a mold resin  8  (sealing resin), an insulating layer  9 , a heat dissipation layer  10 , and an epoxy-based liquid resin  12  (epoxy-based resin). Note that, in  FIG.  2   , the epoxy-based liquid resin  12  is not illustrated. 
     The lead frame  2  includes a plurality of the die pad portions  3  as illustrated, for example, in  FIG.  3   . Each of the die pad portions  3  is electrically independent. On each of the die pad portions  3 , the power semiconductor element  4  is provided via the bonding material  6 . In the example of  FIG.  2   , two power semiconductor elements  4  are provided on one die pad portion  3 . The power semiconductor element  4  is, for example, a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT). 
     The power semiconductor element  4  is electrically connected to the other power semiconductor element  4  provided on the same die pad portion  3  by the metal wire  7 . The power semiconductor element  4  is also electrically connected, by the metal wire  7 , to the lead frame  2  protruding outward from one surface of the mold resin  8 . 
     The IC chip  5  is provided, via the bonding material  6 , on the lead frame  2  protruding outward from the other surface of the mold resin  8 . Here, the other surface of the mold resin  8  means a surface facing the one surface of the mold resin  8 . The IC chip  5  is electrically connected to the other power semiconductor element  4  by the metal wire  7 . 
     The insulating layer  9  is provided on a back surface of the die pad portion  3 . The heat dissipation layer  10  is provided on a back surface of the insulating layer  9 . 
     The mold resin  8  is provided to cover (seal) a part of the lead frame  2 , the die pad portions  3 , the power semiconductor elements  4 , the IC chip  5 , the metal wires  7 , the insulating layer  9 , and a part of the heat dissipation layer  10 . The heat dissipation layer  10  is exposed on a part of the back surface of the mold resin  8 . The mold resin  8  has an insulating property. 
     &lt;Manufacturing method&gt; 
       FIGS.  3  to  7    are views each illustrating an example of a manufacturing step of the semiconductor device  1 . Note that, in  FIGS.  3  to  7   , the insulating layer  9  and the heat dissipation layer  10  are not illustrated. 
     First, the power semiconductor element  4  is provided on the die pad portion  3  and the IC chip  5  is provided on the lead frame  2 , as illustrated in  FIG.  3   . 
     Next, the upper surface of the end portion of the lead frame  2 , including the die pad portion  3  is coated with the epoxy-based liquid resin  12 , as illustrated in  FIGS.  4  and  5   . Specifically, the upper surfaces of the end portions of the lead frame  2  and the die pad portion  3  illustrated in  FIG.  5    are coated with the epoxy-based liquid resin  12 , by using a syringe  11  illustrated in  FIG.  4   . The epoxy-based liquid resin  12  cures after being applied to form an insulating layer. Note that the coefficient of linear expansion of the epoxy-based liquid resin  12  is set to 15 to 18 [× 10   −6 /° C.] in consideration of the coefficient of linear expansion of the mold resin  8 , but the former coefficient of linear expansion is not limited thereto. In addition, an epoxy-based liquid resin curable at room temperature or constant temperature is adopted as the epoxy-based liquid resin  12 . 
     The syringe  11  is included in a non-illustrated epoxy-based liquid resin coating apparatus. The epoxy-based liquid resin coating apparatus can move the syringe  11  in any of an X-direction, a Y-direction, and a Z-direction, so that the epoxy-based liquid resin  12  can be applied at any position. Note that the drive method of the syringe  11  and the discharge method of the epoxy-based liquid resin  12  are not particularly limited. 
     Next, the two power semiconductor elements  4  provided on the same die pad portion  3  are connected by the metal wire  7 , the power semiconductor element  4  and the lead frame  2  are connected by the metal wire  7 , and the power semiconductor element  4  and the IC chip  5  are connected by the metal wire  7 , as illustrated in  FIG.  6   . 
     Next, the mold resin  8  is provided to cover a part of the lead frame  2 , the die pad portions  3 , the power semiconductor elements  4 , the IC chips  5 , the metal wires  7 , and the epoxy-based liquid resin  12 , as illustrated in  FIG.  7   . Transfer molding using the mold resin  8  is performed by using a molding apparatus illustrated, for example, in  FIGS.  8  to  11   . The molding apparatus includes an upper mold  13 , a lower mold  14 , a plunger  15 , a cavity  16 , and a gate  17 . The cavity  16  has a shape corresponding to the outer shape of the semiconductor device  1 . 
     As illustrated in  FIGS.  8  and  9   , a pot (space surrounded by the lower mold  14  and the plunger  15 ) is filled with the mold resin  8 . The lead frame  2  in the state illustrated in  FIG.  6    is placed in the cavity  16 . Note that, in  FIGS.  8  to  11   , the lead frame  2  is not illustrated. As illustrated in  FIGS.  10  and  11   , the mold resin  8  is melted by the heat of the upper mold  13  and the lower mold  14 , and is injected into the cavity  16  through the gate  17  as the plunger  15  rises. As a result, the semiconductor device after the molding illustrated in  FIG.  7    is obtained. Thereafter, the semiconductor device  1  illustrated in  FIG.  1    is obtained through the steps of: cutting out the semiconductor device from the lead frame  2 ; bending a portion corresponding to the terminal of the lead frame  2 ; and the like. 
     &lt;Effects&gt; 
     Conventionally, there has been a problem that deformation of a lead frame, deformation of a metal wire, or the like may occur when handled in the steps after the wiring of metal wires through transfer molding, resulting in a short circuit between different electrodes. 
     On the other hand, in the first preferred embodiment, the upper surfaces of the end portions of the lead frame  2  and the die pad portion  3  are coated with the epoxy-based liquid resin  12 , so that insulation distances can be secured between different electrodes (between the lead frames  2  adjacent, between the die pad portions  3  adjacent, and between the lead frame  2  and the die pad portion  3  adjacent). As a result, the quality of the semiconductor device  1  can be improved. Although the case, where the upper surfaces of the end portions of the lead frame  2  and the die pad portion  3  are coated with the epoxy-based liquid resin  12 , has been described above, the same effects can be obtained even when the side surfaces of the lead frame  2  and the die pad portion  3  are coated with the epoxy-based liquid resin  12 . Note that the epoxy-based liquid resin  12  may be provided on at least either the upper surfaces of the end portions or the side surfaces of the lead frame  2  and the die pad portion  3 . 
     Second Preferred Embodiment 
     &lt;Configuration and Manufacturing Method&gt; 
       FIG.  12    is a cross-sectional view illustrating an example of a configuration of a semiconductor device according to a second preferred embodiment. The semiconductor device according to the second preferred embodiment is characterized by including a metal wire  20  provided, on its surface, with an epoxy-based liquid resin (epoxy-based resin). Since other configurations are similar to those of the semiconductor device  1  according to the first preferred embodiment, detailed description thereof is omitted here. Note that, in  FIG.  12   , the mold resin  8 , the insulating layer  9 , and the heat dissipation layer  10  are not illustrated. 
     An epoxy-based liquid resin coating apparatus moves the syringe  11  in any of the X-direction, the Y-direction, and the Z-direction, and coats the surface of the metal wire  7  illustrated, for example, in  FIG.  6    with the epoxy-based liquid resin. The metal wire  20  can be obtained after the epoxy-based liquid resin coating the surface of the metal wire  7  cures. 
     &lt;Effects&gt; 
     By coating the metal wire with the epoxy-based liquid resin, the metal wire can be reinforced against deformation. In the semiconductor device including the metal wire  20 , it is possible to prevent breakage of a metal wire bonding portion due to vibration that is a problem with the material of a metal wire whose diameter is, for example, 100 μm or less. As a result, the semiconductor device according to the second preferred embodiment can be improved in quality more than the semiconductor device according to the first preferred embodiment. 
     Third Preferred Embodiment 
     &lt;Configuration and Manufacturing Method&gt; 
       FIG.  13    is a cross-sectional view illustrating an example of a configuration of a semiconductor device according to a third preferred embodiment. The semiconductor device according to the third preferred embodiment is characterized by including an epoxy-based liquid resin  30  in a bonding portion between the metal wire  7  and the lead frame  2 , a bonding portion between the metal wire  7  and the power semiconductor element  4 , and a bonding portion between the metal wire  7  and the IC chip  5 . The bonding portion is also referred to as a stitch. Since other configurations are similar to those of the semiconductor device  1  according to the first preferred embodiment, detailed description thereof is omitted here. Note that, in  FIG.  13   , the mold resin  8 , the insulating layer  9 , and the heat dissipation layer  10  are not illustrated. 
     An epoxy-based liquid resin coating apparatus moves the syringe  11  in any of the X-direction, the Y-direction, and the Z-direction, and coats each of the bonding portions illustrated in  FIG.  13    with the epoxy-based liquid resin. The epoxy-based liquid resin  30  is obtained after the epoxy-based liquid resin coating each of the bonding portions cures. 
     &lt;Effects&gt; 
     Deformation of a metal wire progresses from the bonding portion of the metal wire as a starting point. By providing the epoxy-based liquid resin  30  in the bonding portions for reinforcement, as illustrated in  FIG.  13   , deformation of the metal wire can be prevented, and breakage of the bonding portion of the metal wire due to vibration can also be prevented. In addition, it is sufficient to coat only the bonding portions with the epoxy-based liquid resin, so that the epoxy-based liquid resin can be applied without being affected by a variation in the wiring shape of the metal wire. As a result, the semiconductor device according to the third preferred embodiment can be improved in quality more than the semiconductor device according to the first preferred embodiment. 
     Although the configuration, in which the semiconductor device  1  according to the first preferred embodiment includes the epoxy-based liquid resin  30 , has been described above, a configuration may be adopted in which the semiconductor device according to the second preferred embodiment includes the epoxy-based liquid resin  30 . In the case of the configuration, the effects of the second preferred embodiment can also be obtained in addition to the above effects of the third preferred embodiment. 
     Fourth Preferred Embodiment 
     &lt;Configuration and Manufacturing Method&gt; 
       FIG.  14    is a cross-sectional view illustrating an example of a configuration of a semiconductor device according to a fourth preferred embodiment. The semiconductor device according to the fourth preferred embodiment is characterized in that an epoxy-based liquid resin  40  is included on the lower surface of the die pad portion  3  and a part of the epoxy-based liquid resin  40  is exposed from the mold resin  8 . That is, the semiconductor device according to the fourth preferred embodiment includes the epoxy-based liquid resin  40  instead of the insulating layer  9  and the heat dissipation layer  10  in the semiconductor device  1  according to the first preferred embodiment. Since other configurations are similar to those of the semiconductor device  1  according to the first preferred embodiment, detailed description thereof is omitted here. The epoxy-based liquid resin  40  is obtained by performing a surface treatment on a filler as a part of the contained substances to improve thermal conductivity. The thermal conductivity of the epoxy-based liquid resin 40 is7 [W/m. K] or more. 
     &lt;Effects&gt; 
     In the semiconductor device  1  including the insulating layer  9  and the heat dissipation layer  10  that has been described in the first preferred embodiment, there has been a problem that the adhesion at the interface between the die pad portion  3  of the lead frame  2  and the insulating layer  9  decreases, which is a contradiction to achieve the characteristics. On the other hand, in the semiconductor device according to the fourth preferred embodiment, the epoxy-based liquid resin  40  having high thermal conductivity is used, so that the epoxy-based liquid resin  40  in a liquid state improves the adhesion between the die pad portion  3  and the epoxy-based liquid resin  40 . As a result, the quality of the semiconductor device can be improved. 
     In addition, the materials, respectively making up the insulating layer  9  and the heat dissipation layer  10 , have high manufacturing costs and manufacturing difficulties due to the required characteristics, which are expensive materials in the semiconductor device. When the epoxy-based liquid resin  40  is used instead of the insulating layer  9  and the heat dissipation layer  10 , as in the semiconductor device according to the fourth preferred embodiment, the number of materials is reduced, so that the manufacturing cost of the semiconductor device can be reduced. 
     In the above description, a configuration has been described in which the epoxy-based liquid resin  40  is included instead of the insulating layer  9  and the heat dissipation layer  10  in the semiconductor device  1  according to the first preferred embodiment, but the present disclosure is not limited thereto. A configuration may be adopted in which the epoxy-based liquid resin  40  is included instead of, for example, the insulating layer  9  and the heat dissipation layer  10  in the semiconductor device according to the second or third preferred embodiment. In the case of this configuration, the effects of the second or third preferred embodiment can also be obtained in addition to the above effects of the fourth preferred embodiment. Alternatively, the epoxy-based liquid resin  40  may be provided only on the lower surface of the die pad portion  3  without providing the epoxy-based liquid resin  12  on the surfaces of the lead frame  2  and the die pad portion  3  as in the first to third preferred embodiments. 
     Note that, within the scope of the present disclosure, respective preferred embodiments can be freely combined, or each preferred embodiment can be appropriately modified or omitted.
         While the disclosure has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous modifications and variations can be devised.