Patent Publication Number: US-2023132513-A1

Title: Resin-sealed semiconductor device and method for manufacturing resin-sealed semiconductor device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a resin-sealed semiconductor device and a method for manufacturing a resin-sealed semiconductor device. 
     2. Description of the Background Art 
     Semiconductor devices with power semiconductor elements mounted thereon have increasingly had larger capacities. In order to apply large current to the power semiconductor element, the size of a lead frame serving as a main terminal needs to be enlarged. However, when the size of the lead frame is enlarged, a thermal deformation force caused by difference among linear expansion coefficients of the semiconductor element, the lead frame, and a joining material increases. Therefore, for the purpose of reducing the thermal deformation force, a sealing structure using mold resin is generally adopted in many cases. 
     Meanwhile, when the semiconductor element and a conductor member such as the lead frame are soldered to each other, surplus solder might overflow from between the semiconductor element and the conductor member. At this time, if the surplus solder wets and spreads toward the semiconductor element, this leads to failure such as short-circuit or insulation fault in the semiconductor element. Accordingly, disclosed is a configuration in which a groove for introducing the overflowed solder is provided so as to inhibit wetting and spreading of the solder (see, for example, Patent Document 1). 
     Patent Document 1: Japanese Laid-Open Patent Publication No. 2020-188162 
     In Patent Document 1, solder is interposed between a protruding surface of the conductor member and the semiconductor element, and a side surface of a protruding portion of the conductor member has a groove for inhibiting solder from widely covering the side surface, while the thickness of a solder layer is not regulated. Therefore, there is a possibility of causing variations in the thickness of a joining layer in a pressing step at the time of solder joining. 
     SUMMARY OF THE INVENTION 
     The present disclosure has been made to solve the above problem, and an object of the present disclosure is to provide a resin-sealed semiconductor device that can regulate the minimum thickness of a joining material and inhibit the joining material from leaking out of a proper range. 
     A resin-sealed semiconductor device according to the present disclosure includes: a semiconductor element; a heat spreader to which one surface of the semiconductor element is joined via a first joining material; a first lead frame joined to a surface, of the heat spreader, at which the semiconductor element is joined; a second lead frame joined to another surface of the semiconductor element via a second joining material; and mold resin sealing the first lead frame, the second lead frame, the semiconductor element, and the heat spreader together, such that a part of the first lead frame and a part of the second lead frame are exposed. The second lead frame has, on a surface thereof opposed to the semiconductor element, a protrusion to regulate a thickness of the second joining material, and a groove formed at a peripheral part of the second joining material. 
     In the resin-sealed semiconductor device according to the present disclosure, the thickness of the joining material joining the semiconductor element and the second lead frame can be regulated by the protrusion provided to the second lead frame, and wetting and spreading of the joining material can be inhibited by the groove provided to the second lead frame. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a partial sectional view schematically showing the structure of a resin-sealed semiconductor device according to the first embodiment of the present disclosure; 
         FIG.  2    is a plan view schematically showing the structure of the resin-sealed semiconductor device according to the first embodiment; 
         FIGS.  3 A to  3 C  show a manufacturing process for the resin-sealed semiconductor device according to the first embodiment; 
         FIG.  4    is a partial sectional view schematically showing the structure of a resin-sealed semiconductor device according to the second embodiment of the present disclosure; 
         FIG.  5    is a plan view schematically showing the structure of the resin-sealed semiconductor device according to the second embodiment; and 
         FIG.  6    shows a relationship between a joining angle of an above-chip joining material and maximum stress occurring in a semiconductor element in the resin-sealed semiconductor device according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     Hereinafter, embodiments of a resin-sealed semiconductor device according to the present disclosure will be described with reference to the drawings. In the drawings, the same reference characters denote the same or corresponding parts. 
     First Embodiment 
     Hereinafter, a resin-sealed semiconductor device according to the first embodiment will be described with reference to the drawings. 
       FIG.  1    is a partial sectional view schematically showing the structure of the resin-sealed semiconductor device according to the first embodiment, and  FIG.  2    is a plan view schematically showing the resin-sealed semiconductor device.  FIG.  1    corresponds to a part of a cross-section along line A-A in  FIG.  2   . 
     The resin-sealed semiconductor device (hereinafter, simply referred to as semiconductor device) includes a semiconductor element  1  as a switching element, a semiconductor element  2  as a rectification element, a heat spreader  3 , first lead frames  12 ,  13 , a second lead frame  5 , and mold resin  11 . The semiconductor element  1  as the switching element is joined to one surface of the heat spreader  3  via a below-chip joining material (see  FIGS.  3 A to  3 C ). 
     The semiconductor element  2  as the rectification element is joined to the one surface of the heat spreader  3  via a below-chip joining material. The first lead frames  12 ,  13  are joined to end portions of the one surface of the heat spreader  3  via lead joining materials (not shown). The lead joining materials are formed through joining by a solder joining material, ultrasonic metal welding, or the like so as to ensure electric conduction between the heat spreader  3  and the first lead frames  12 ,  13 , thus joining the heat spreader  3  and the first lead frames  12 ,  13  integrally. 
     The second lead frame  5  has suspension portions  14  for keeping the height at the time of joining. The second lead frame  5  is joined to the semiconductor element  1  via an above-chip joining material  4   a  and joined to the semiconductor element  2  via an above-chip joining material  4   a.  In addition, the second lead frame  5  has opening holes  6 , and a protrusion  10  for regulating a minimum thickness of the above-chip joining material  4   a.  The mold resin  11  is formed such that the semiconductor elements  1 ,  2 , the heat spreader  3 , the below-chip joining materials, parts of the first lead frames  12 ,  13 , a part of the second lead frame  5 , the lead joining materials, the opening holes  6  formed in the second lead frame  5 , a below-opening area  7  which is an area below the opening holes  6 , and the above-chip joining materials  4   a  are included inside and sealed against the outside. The first lead frames  12 ,  13  and the second lead frame  5  have parts exposed from the mold resin  11  and connected as terminals to the outside. 
     The semiconductor element  1  is formed by a semiconductor switching element such as an insulated gate bipolar transistor (IGBT) or a metal oxide semiconductor field effect transistor (MOSFET). The IGBT is an element for applying large current to a load and performing driving thereof. Preferably, the semiconductor elements  1 ,  2  are made of silicon (Si), for example, but is not limited thereto. For example, it is more preferable that semiconductor chips forming the semiconductor elements  1 ,  2  are made of any material selected from a group consisting of silicon carbide (SiC), a gallium-nitride-based material (e.g., gallium nitride (GaN)), and diamond. These materials are so-called wide bandgap semiconductor materials having wider bandgaps than silicon. The semiconductor elements  1 ,  2  formed using such a wide bandgap semiconductor material can be applied to operation at a higher temperature as compared to semiconductor elements using a silicon semiconductor material such as MOSFET. That is, the wide bandgap semiconductor materials are semiconductor materials suitable for applying large current. 
     The semiconductor element  1  has divided electrodes at an active surface thereof so that the temperature distribution on the active surface is uniform even when large current flows, and preferably has two or more divided electrodes. 
     Electrodes at active surfaces as front surface parts of the semiconductor elements  1 ,  2  are joined to the second lead frame  5  serving as main terminals, via the above-chip joining materials  4   a  made of solder joining material or the like, as described above. 
     In  FIG.  2   , it is found that there are two divided electrodes at the active surface of the semiconductor element  1  and the above-chip joining materials  4   a  are provided so as to correspond to the respective electrodes. The above-chip joining materials  4   a  are indicated by broken lines. The second lead frame  5  has, above an area between the two electrodes, the opening holes  6  so that the mold resin  11  can readily reach and fill the below-opening area  7  (see  FIG.  1   ). 
     The heat spreader  3 , the first lead frames  12 ,  13 , and the second lead frame  5  are made of metal having high conductivity. Among highly conductive metals, a copper material is most suitable in terms of electric resistance, workability, cost, and the like. Here, the copper material refers to pure copper or a copper alloy mainly composed of copper. 
     The mold resin  11  sealing the entirety including the opening holes  6  of the second lead frame  5  and the below-opening area  7  is preferably resin having a linear expansion coefficient close to the linear expansion coefficients of the heat spreader  3 , the first lead frames  12 ,  13 , and the second lead frame  5  so that a thermal deformation force occurring due to difference among the linear expansion coefficients does not become great. The linear expansion coefficient of pure copper is 16 [ppm/K] to 17 [ppm/K]. Therefore, it is desirable that also the linear expansion coefficient of the mold resin 11 is 15 [ppm/K] to 18 [ppm/K]. 
     Next, a method for manufacturing the semiconductor device according to the first embodiment will be described with reference to  FIGS.  3 A to  3 C .  FIGS.  3 A to  3 C  correspond to a sectional view along line B-B in  FIG.  2   . 
     First, in a die bonding step in  FIG.  3 A , the semiconductor element  1  as the switching element and the semiconductor element  2  as the rectification element are placed with an interval therebetween above one surface of the heat spreader  3 , and are joined thereto via the below-chip joining materials  4   b.  The semiconductor element  1  as the switching element is, for example, made from silicon, and is formed as a semiconductor chip provided with an IGBT and having two divided electrodes at the active surface. In  FIGS.  3 A to  3 C , only one electrode la is shown. The semiconductor element  2  as the rectification element is, for example, made of silicon, and is formed as a semiconductor chip provided with a diode and having one electrode at the active surface. 
     Preferably, the below-chip joining material  4   b  is any joining material selected from a group consisting of a solder joining material, a sintering-type filler mainly composed of silver, a brazing material mainly composed of silver, a material obtained by dispersing copper in tin, and gold-based alloys such as gold tin and gold germanium mainly composed of gold. These joining materials are joining materials having high thermal conductivity and high electrical conductivity. 
     Next, in a reflow step in  FIG.  3 B , the first lead frames  12 ,  13  serving as input/output terminals are connected to the heat spreader  3 , using a lead joining material (not shown). The first lead frames  12 ,  13  are joined to end portions of the surface of the heat spreader  3  at which the semiconductor elements  1 ,  2  are mounted. In addition, the second lead frame  5  serving as main terminals is joined to the two electrodes la of the semiconductor element  1 , using the above-chip joining material  4   a,  and is joined to the electrode  2   a  of the semiconductor element  2 , using the above-chip joining material  4   a.  In  FIG.  3 B , only one electrode la of the two electrodes of the semiconductor element  1  is shown, but the second lead frame  5  is connected also to the other electrode as shown in  FIG.  2   . 
     For connection between the heat spreader  3  and the first lead frames  12 ,  13 , the lead joining material (not shown) made of a solder joining material is used. However, without limitation thereto, a joining method such as ultrasonic joining or welding may be used. 
     It is desirable that the above-chip joining material  4   a  formed from a solder ribbon having a constant thickness is used for joining between the semiconductor elements  1 ,  2  and the second lead frame  5 . If the stiffness of the above-chip joining material  4   a  is low, crack occurs. Therefore, it is desirable that the thickness of the above-chip joining material  4   a  is approximately 0.2 to 0.5 mm. However, because of manufacturing variations due to a thick solder ribbon, the volume might be changed by 10% or more. In addition, the second lead frame  5  is fixed using the suspension portions  14  so as to keep the distance between the second lead frame  5  and the semiconductor elements  1 ,  2 , i.e., the height. Thus, warp occurs between the suspension portion  14  and the suspension portion  14 , so as to form a valley shape with a reduced distance between the suspension portions  14 , resulting in variations in the distance between the second lead frame  5  and the semiconductor elements  1 ,  2 . Therefore, the second lead frame  5  needs to have the protrusion  10  in order to regulate the minimum thickness of the above-chip joining material  4   a  after the above-chip joining material  4   a  is melted. 
     On the other hand, the protrusion  10  provided to the second lead frame  5  is formed by press work and thus has height variations in a range of about For example, if the solder volume varies to increase and the height of the protrusion  10  varies to decrease, at the time of joining, solder which is the above-chip joining material  4   a  might flow outward along the surface direction of the second lead frame  5 , i.e., flow to the outside of a proper range. Further, if the above-chip joining material  4   a  flows to an area between the two electrodes of the semiconductor element  1 , this causes such a problem that the electrodes are electrically connected to each other, or the opening holes  6  of the second lead frame  5  formed between the electrodes are filled and therefore resin cannot enter the area between the electrodes in the next step. 
     The second lead frame  5  according to the first embodiment has, on a surface thereof opposed to the semiconductor element  1 , the protrusion  10 , and a groove  8  provided on a side at least toward the area between the two electrodes of the semiconductor element  1  from the protrusion  10  and toward the protrusion  10  side relative to the opening holes  6 . The second lead frame  5  is placed on the above-chip joining materials  4   a  such that the grooves  8  are positioned on the outer peripheral side of the solder ribbons that are the above-chip joining materials  4   a  placed on the semiconductor elements  1 ,  2 . When the above-chip joining material  4   a  is melted, a surplus above-chip joining material  4   a  between the second lead frame  5  and the semiconductor element  1  is introduced to the groove  8  along the surface of the second lead frame  5 , so that the wetting speed of solder which is the above-chip joining material  4   a  is reduced and overflow thereof can be absorbed. That is, the groove  8  is a groove for preventing flow of solder. 
     Further, as shown in  FIG.  1   , a barrier  9  protruding toward the semiconductor element  1  side is provided between the groove  8  and the opening hole  6 , for example, at an entrance of the opening hole  6 . Thus, even if solder runs over the groove  8 , the barrier  9  can prevent wetting and spreading of the solder, whereby the solder can be prevented from flowing into the opening hole  6 . 
     The shape of the opening hole  6  formed in the second lead frame  5  exemplified in the present embodiment is a round shape. However, the shape may be freely set as long as the opening hole  6  penetrates the second lead frame  5  above the area between the electrodes of the semiconductor element  1 . 
     The groove  8  formed in the second lead frame  5  has a triangular sectional shape and is formed in a straight shape. However, without limitation thereto, the shape, the position, and the length of the groove  8  may be freely set as long as the wetting speed of solder can be reduced and overflow thereof can be absorbed. 
     The barrier  9  provided to the second lead frame  5  is located at the entrance of the opening hole  6 , as an example. However, the shape, the position, and the length of the barrier  9  may be freely set as long as solder can be prevented from flowing into the opening hole  6 . 
     Next, in a transfer molding step in  FIG.  3 C , the semiconductor elements  1 ,  2 , the heat spreader  3 , parts of the first lead frames  12 ,  13 , a part of the second lead frame  5  including the opening holes  6 , the below-opening area  7 , and the above-chip joining materials  4   a  are sealed by the mold resin  11  made of thermosetting resin. 
     The mold resin  11  need not have high thermal conductivity. Therefore, as an inorganic filler to be contained in the thermosetting resin such as epoxy resin, fused silica is most suitable among types of silicon oxide (silica) which has high fluidity when contained in thermosetting resin and whose linear expansion coefficient can be easily adjusted. In the resin-sealed semiconductor device, a large amount of copper material is used. Therefore, stress inside the resin-sealed semiconductor device can be reduced by matching the linear expansion coefficient of the mold resin  11  to the linear expansion coefficient of copper, i.e., making the linear expansion coefficient of the mold resin  11  equal or approximate to the linear expansion coefficient of copper. Accordingly, the amount of the inorganic filler may be adjusted so that the linear expansion coefficient of the mold resin  11  becomes 15 [ppm/K] to 18 [ppm/K]. Such adjustment to match the linear expansion coefficients provides an effect of improving reliability for temperature cycling. 
     As described above, according to the first embodiment, the second lead frame  5  as main terminals connected to the semiconductor element  1  having two electrodes via the above-chip joining materials  4   a  has, on the side opposed to the semiconductor element  1 , the protrusion  10 , the opening holes  6  between the two electrodes, and the groove  8  between the protrusion  10  and the opening holes  6 . Thus, the thickness of the above-chip joining material  4   a  when melted can be regulated by the protrusion  10 , and even if a surplus above-chip joining material  4   a  flows to the opening hole  6  side, the groove  8  can reduce the wetting speed and absorb the surplus above-chip joining material  4   a.  Further, the barrier  9  is provided between the opening hole  6  and the groove  8  of the second lead frame  5 , whereby the barrier  9  prevents wetting and spreading of the above-chip joining material  4   a  running over the groove  8 , thus preventing the above-chip joining material  4   a  from flowing into the opening hole  6 . 
     As described above, the structure is made such that the thickness of the above-chip joining material  4   a  can be regulated and the above-chip joining material  4   a  can be inhibited from leaking out of a proper range, whereby it becomes possible to completely fill the space including the opening hole  6  and the below-opening area  7 , with the mold resin  11 . Thus, increase in stress occurring in the semiconductor element  1  and the above-chip joining material  4   a  can be prevented, and occurrence of crack in the above-chip joining material  4   a  and the semiconductor element  1  is suppressed, whereby it is possible to provide a resin-sealed semiconductor device having a high quality and a reduced size at low cost. 
     Second Embodiment 
     Hereinafter, a semiconductor device according to the second embodiment will be described with reference to the drawings. 
       FIG.  4    is a partial sectional view schematically showing the structure of the semiconductor device according to the second embodiment, and  FIG.  5    is a plan view schematically showing the semiconductor device.  FIG.  4    corresponds to a part of a cross-section along line A-A in  FIG.  5   . In the first embodiment, the second lead frame  5  has, on the side opposed to the semiconductor element  1 , the protrusion  10 , the opening holes  6  between the two electrodes, and the groove  8  between the protrusion  10  and the opening holes  6 , whereas the second embodiment is different in that the second lead frame  5  has grooves  8  along the peripheries of the above-chip joining materials  4   a  on the side opposed to the semiconductor element  1  and the semiconductor element  2 . The grooves  8  in the second embodiment are formed along the outer peripheries of the areas where the above-chip joining materials  4   a  are provided in the manufacturing process. The other configurations are the same as those in the first embodiment, and the description thereof is omitted. 
     Also in the second embodiment, even if surplus melted solder flows out due to variations in the volume of the above-chip joining material  4   a  and the height of the protrusion  10 , the flow of solder can be inhibited owing to the grooves  8  for preventing flow of solder, which are provided along the entire inner periphery correspondingly to the semiconductor element  1 . 
     Further, the grooves  8  are provided along the entire outer peripheries of the areas where the above-chip joining materials  4   a  are provided. Thus, the joining angles between the above-chip joining materials  4   a  and the semiconductor elements  1 ,  2  can be controlled, and stress occurring in the semiconductor elements  1 ,  2  can be reduced. Hereinafter, stress occurring in the semiconductor element will be described with reference to  FIG.  6   . 
       FIG.  6    shows a relationship between the joining angle of the above-chip joining material and the maximum stress occurring in the semiconductor element in the semiconductor device according to the present embodiment. In  FIG.  6   , the maximum value of stress occurring in the semiconductor element when the semiconductor device has undergone repetitive temperature cycling from −45° C. to 150° C., has been calculated. Here, the joining angle is an angle θ of an end of the above-chip joining material  4   a  with respect to the semiconductor element  1 ,  2 , as shown in  FIG.  6   . 
     The linear expansion coefficient of the semiconductor element  1 ,  2  is 3 [ppm/K] to 5 [ppm/K], the linear expansion coefficient of the below-chip joining material  4   b  is 18 [ppm/K] to 20 [ppm/K], the linear expansion coefficient of the above-chip joining material  4   a  is 21 [ppm/K] to 23 [ppm/K], the linear expansion coefficients of the heat spreader  3  and the second lead frame  5  are 16 [ppm/K] to 17 [ppm/K], and the linear expansion coefficient of the mold resin  11  is 15 [ppm/K] to 18 [ppm/K]. The linear expansion coefficient of the semiconductor element  1 ,  2  is smallest, and the linear expansion coefficient of the above-chip joining material  4   a  is greatest. 
     The semiconductor element  1 ,  2  is made from a semiconductor material, and the strength thereof is smallest in the semiconductor device. Therefore, it is necessary to reduce stress occurring in the semiconductor element  1 ,  2 . In a case where the temperature of the resin-sealed semiconductor device is changed from a high temperature to a low temperature, a force is generated to greatly contract the above-chip joining material  4   a  relative to the semiconductor element  1 ,  2 , so that the maximum stress occurs in the semiconductor element  1 ,  2 . In a case where the joining angle θ of the above-chip joining material  4   a  is an acute angle, the joining area between the above-chip joining material  4   a  and the second lead frame  5  is small, and therefore a force to deform the above-chip joining material  4   a  only in the contracting direction occupies a major proportion. 
     In a case where the joining angle θ of the above-chip joining material  4   a  is 90° to 135°, the joining area between the above-chip joining material  4   a  and the second lead frame  5  increases, so that the ratio of a force to deform the above-chip joining material  4   a  in the expanding direction increases. As a result, the maximum stress occurring in the semiconductor element  1 ,  2  can be reduced. However, in a case where the joining angle of the above-chip joining material  4   a  is greater than 135°, the ratio of the deformation force in the expanding direction excessively increases, so that the maximum stress occurring in the semiconductor element  1 ,  2  increases. It is noted that, in a case where the temperature of the semiconductor device is changed from a low temperature to a high temperature, the force directions are merely reversed and the correlation between the joining angle θ of the above-chip joining material  4   a  and the maximum stress occurring in the semiconductor element  1 ,  2  does not change. 
     From the above, it is found that stress occurring in the semiconductor element  1 ,  2  can be reduced by setting the joining angle θ of the above-chip joining material  4   a  in a range of 90° to 135°. 
     Next, description will be given returning to the structure of the semiconductor element in the second embodiment shown in  FIG.  4    and  FIG.  5   . For example, in a case where the above-chip joining material  4   a  formed from a solder ribbon having a constant thickness is used for joining between each semiconductor element  1 ,  2  and the second lead frame  5 , and there are no variations in the volume of the above-chip joining material  4   a  and the height of the protrusion  10 , the joining angle θ of the above-chip joining material  4   a  becomes close to 90°. However, since there are variations in the volume of the above-chip joining material  4   a  and the height of the protrusion  10 , the joining angle θ of the above-chip joining material  4   a  is changed. Here, the groove  8  for preventing flow of solder is provided along the entire periphery at such a contact position where the joining angle θ of the above-chip joining material  4   a  falls within the proper range of 90° to 135°. Surplus solder due to variations in the volume of the above-chip joining material  4   a  and the height of the protrusion  10  is introduced to the groove  8  along the surface of the second lead frame. Thus, the joining angle θ of the above-chip joining material  4   a  can be controlled in the proper range of 90° to 135°. That is, as shown in  FIG.  4   , the position of the groove  8  provided toward the outer peripheral side relative to the position where the above-chip joining material  4   a  and the semiconductor element  1  contact with each other is the joining position between the above-chip joining material  4   a  and the second lead frame  5 . Thus, the joining angle θ of the above-chip joining material  4   a  can be set in the proper range. 
     Also in the second embodiment, as a matter of course, the barrier  9  is provided between the groove  8  and the opening hole  6  of the second lead frame  5 , whereby the barrier  9  prevents wetting and spreading of the above-chip joining material  4   a  running over the groove  8 , thus preventing the above-chip joining material  4   a  from flowing into the opening hole  6 . 
     As described above, the semiconductor device according to the second embodiment provides the same effects as in the first embodiment. Further, on the outer peripheral side relative to the position where the above-chip joining material  4   a  and the semiconductor element  1  contact with each other, the groove  8  is provided along the entire periphery of the above-chip joining material  4   a,  whereby it becomes possible to control the joining angle θ of the above-chip joining material  4   a  in the proper range of 90° to 135°. Thus, stress occurring in each semiconductor element  1 ,  2  can be reduced and occurrence of crack can be further suppressed, whereby it is possible to provide a resin-sealed semiconductor device having a high quality and a reduced size at low cost. 
     Other Embodiments 
     (1) The first and second embodiments have shown the examples in which the second lead frame  5  has one protrusion  10  on the side opposed to the semiconductor element  1 . However, the present disclosure is not limited thereto. The protrusions  10  may be provided for the respective two electrodes of the semiconductor element  1 . Further, the protrusion  10  may be provided so as to be opposed to the semiconductor element  2 . 
     (2) The first and second embodiments have shown the examples in which the second lead frame  5  has the opening holes  6  at positions corresponding to the area between the two electrodes of the semiconductor element  1 . However, the present disclosure is not limited thereto. In a case where the area of the second lead frame  5  is large, for example, the opening holes  6  may be also provided between the plurality of semiconductor elements  1 ,  2  so as not to produce a part that is not sealed. In addition, in a case where the semiconductor element  1  has three or more electrodes, the opening holes  6  may be provided between adjacent electrodes. 
     Although the disclosure is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects, and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations to one or more of the embodiments of the disclosure. 
     It is therefore understood that numerous modifications which have not been exemplified can be devised without departing from the scope of the present disclosure. For example, at least one of the constituent components may be modified, added, or eliminated. At least one of the constituent components mentioned in at least one of the preferred embodiments may be selected and combined with the constituent components mentioned in another preferred embodiment. 
     DESCRIPTION OF THE REFERENCE CHARACTERS 
     
         
           1  semiconductor element 
           1   a  electrode 
           2  semiconductor element 
           2   a  electrode 
           3  heat spreader 
           4   a  above-chip joining material 
           4   b  below-chip joining material 
           5  second lead frame 
           6  opening hole 
           7  below-opening area 
           8  groove 
           9  barrier 
           10  protrusion 
           11  mold resin 
           12 ,  13  first lead frame 
           14  suspension portion