Patent Publication Number: US-11049835-B2

Title: Semiconductor module

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. application Ser. No. 15/837,560 filed Dec. 11, 2017, which claims benefit of priority to U.S. Provisional Patent Application No. 62/434,119, filed Dec. 14, 2016, the entire content of which is incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a semiconductor module. 
     Description of Related Art 
     There has been known a semiconductor module in which a semiconductor die provided on a conductive die pad is sealed by a resin. In general, resins exhibit a poor thermal conductivity, so that the size of a conductive die pad is increased thereby to dissipate the heat generated in a semiconductor die. 
     SUMMARY 
     However, a stress test in which reflow is carried out in a hot and humid environment has confirmed the occurrence of detachment between a conductive die bonding agent, which is used to connect a semiconductor die to a conductive die pad, and the conductive die pad. In addition, operation failures, such as a malfunction and fluctuations in gain value, have been also confirmed. 
     The present disclosure has been made in view of the circumstances described above, and it is an object of the disclosure to provide a semiconductor module that reduces the detachment between a conductive die bonding agent and a conductive die pad or a semiconductor die, and operation failures. 
     A semiconductor module according to an aspect of the present disclosure includes: a substrate; a conductive die pad provided on the substrate; a semiconductor die provided on the conductive die pad; a conductive die bonding agent that electrically connects the conductive die pad and the semiconductor die; a wire bonding pad provided on the substrate; and a wire that electrically connects the wire bonding pad and the semiconductor die. The semiconductor module further includes a sealing resin that seals at least the conductive die pad, the semiconductor die, the conductive die bonding agent, the wire bonding pad, and the wire. Further, the area of the conductive die pad is 5.0 mm 2  or less in a planar view. 
     A semiconductor module according to another aspect of the present disclosure includes: a substrate; a conductive die pad which is provided on the substrate and the surface material of which is Cu; a semiconductor die provided on the conductive die pad; and a conductive die bonding agent which electrically connects the conductive die pad and the semiconductor die. The semiconductor module according to this aspect further includes a wire bonding pad which is provided on the substrate and the surface material of which is a metal containing Au; and a wire which electrically connects the wire bonding pad and the semiconductor die. 
     A semiconductor module according to yet another aspect of the present disclosure includes: a substrate; a first conductive die pad provided on the substrate; a second conductive die pad provided adjacently to and apart from the first conductive die pad on the substrate; and a semiconductor die. The semiconductor module according to this aspect further includes a conductive die bonding agent which is in contact with the first conductive die pad, the second conductive die pad, and a substrate in a gap between the first conductive die pad and the second conductive die pad, and which electrically connects the first conductive die pad and the second conductive die pad and the semiconductor die. 
     According to the present disclosure, a semiconductor module can be provided, which restricts the detachment between a conductive die bonding agent and a conductive die pad or a semiconductor die. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A through 1D  present schematic plan views illustrating a semiconductor module of a comparative example and a semiconductor module of an embodiment; 
         FIGS. 2A and 2B  present the sectional views of a semiconductor module according to the comparative example; 
         FIG. 3  is a sectional view of a semiconductor module according to a first embodiment; 
         FIGS. 4A and 4B  present sectional views of a semiconductor module according to a second embodiment; 
         FIG. 5  is a sectional view of a semiconductor module according to a third embodiment; 
         FIGS. 6A and 6B  present graphs illustrating the areas of conductive die pads (and conductive die bonding agents) and the results of hot and humid stress tests; 
         FIGS. 7A and 7B  present graphs illustrating the distances between the conductive die pad and a semiconductor die in a planar view, and the results of hot and humid stress tests; 
         FIG. 8  illustrates the edge of a conductive die pad having an inverse tapered shape; 
         FIG. 9  is a plan view illustrating a conductive die bonding agent with reduced wet spread; 
         FIG. 10  is a plan view illustrating a conductive die pad on a plurality of heat dissipation vias; 
         FIG. 11  is a sectional view of a PCB base in which an anti-flow groove has been formed; 
         FIGS. 12A and 12B  present plan views illustrating a semiconductor die provided on conductive die pads formed apart from each other; 
         FIG. 13  is a sectional view of a semiconductor module according to a fifth embodiment; 
         FIGS. 14A and 14B  present diagrams illustrating the manufacturing process of the semiconductor module according to the fifth embodiment; and 
         FIG. 15  is a graph illustrating the comparison in gain fluctuation value after a hot and humid stress test between a conductive die pad using NiPdAu as the surface material thereof and a conductive die pad using Cu as the surface material thereof. 
     
    
    
     DETAILED DESCRIPTION 
     The following will describe in detail the embodiments of the present disclosure with reference to the accompanying drawings. A description of the elements that have the same functions or configurations as those of comparative examples or other embodiments will be simplified or omitted. The following embodiments are illustrations for explaining the present disclosure and are not meant to limit the present disclosure only to the embodiments. Further, the present disclosure can be implemented in a variety of modifications insofar as the modifications do not depart from the spirit of the present disclosure. 
       FIGS. 1A-1D  present schematic plan views illustrating a semiconductor module  1  according to a comparative example and semiconductor modules  2 ,  3  and  4  according to the embodiments.  FIG. 1A  illustrates the semiconductor module  1  according to the comparative example, which includes a PCB base  16  (substrate), a conductive die pad  11   a  placed on the PCB base  16 , two semiconductor dies  12   a  and  12   b  placed on the conductive die pad  11   a , and a conductive die bonding agent (conductive die bond), which is not illustrated, the bonding agent being used to electrically connect the semiconductor dies  12   a  and  12   b  to the conductive die pad  11   a . The semiconductor module  1  further includes a plurality of wires  13  for electrically interconnecting the semiconductor dies  12   a  and  12   b , or electrically connecting the semiconductor dies  12   a  and  12   b  with other metal wiring (not illustrated). Further, these elements are sealed by a sealing resin (not illustrated). 
       FIG. 1B  illustrates a semiconductor module  2  according to a first embodiment. A conductive die pad  11   b  of the semiconductor module  2  is formed to have an area that is smaller than the area of the conductive die pad  11   a  of the comparative example, as observed in a planar view. Hence, the distance between the boundaries of the semiconductor dies  12   a  and  12   b  and the boundary of the conductive die pad  11   b  is smaller than that in the comparative example. Further, the area of a conductive die bonding agent (not illustrated) applied onto the conductive die pad  11   b  is also smaller. The semiconductor module  2  will be further described hereinafter. 
       FIG. 1C  illustrates a semiconductor module  3  according to a second embodiment. A conductive die pad  11   c  of the semiconductor module  3  and a conductive die pad  11   c ′ adjacent to the conductive die pad  11   c  are formed apart from each other. Further, the semiconductor dies  12   b  and  12   a  are formed on the conductive die pads  11   c  and  11   c ′, respectively. The adjoining semiconductor dies  12   a  and  12   b  are electrically connected by at least one wire  13 . The semiconductor module  3  will be further described hereinafter. 
       FIG. 1D  illustrates a semiconductor module  4  according to a third embodiment. A semiconductor die  12   b  of adjoining semiconductor dies  12   a  and  12   b  of the semiconductor module  4  does not require electrical connection from a bottom surface. Hence, a conductive die pad for the semiconductor die  12   b  is not provided, while a conductive die pad  11   d  electrically connected with the semiconductor die  12   a  through a conductive die bonding agent (not illustrated) is provided. The semiconductor die  12   b  is connected directly to a PCB base  16  through an insulating die bonding agent or through a solder resist (not illustrated). The semiconductor module  4  will be further described hereinafter. 
       FIG. 2A  is a sectional view of a semiconductor module  1 ′ according to another comparative example. As illustrated in the sectional view, the semiconductor module  1 ′ includes a PCB base  16  (substrate), a conductive die pad  11   a  placed on the PCB base  16 , a semiconductor die  12   a  placed on the conductive die pad  11   a , and a conductive die bonding agent  14   a  which electrically connects the conductive die pad  11   a  and the semiconductor die  12   a . Further, a wire bonding pad  18  and a metal wire connected to the wire bonding pad  18  are formed on the PCB base  16  such that the wire bonding pad  18  is adjacent to and apart from the conductive die pad  11   a . The wire bonding pad  18  and the semiconductor die  12   a  are electrically connected by a wire  13 . Metal wiring for the connection is protected by a solder resist  15 . Further, these elements are sealed by a sealing resin  17 . 
     The semiconductor module  1 ′ was subjected to a stress test, in which a plurality of reflows at 250° C. or more are carried out in a hot and humid environment (e.g. a temperature of 80° C. or more and a humidity of 80% or more) (hereinafter referred to as “the hot and humid stress test”). The test results have revealed detachment  100  between the conductive die bonding agent  14   a  and the conductive die pad  11   a , as illustrated in  FIG. 2B . It has also been confirmed that the detachment occurs between the conductive die bonding agent  14   a  and the semiconductor die  12   a  in some cases, and the detachment occurs also between the sealing resin  17  and the conductive die pad  11   a  in some cases. Further, defects in characteristics, such as operation failures and fluctuations in gain value, were also confirmed. 
     The inventors have carried out the hot and humid stress test, using semiconductor dies and conductive die pads of various different shapes and sizes to identify the cause, and have found that the conductive die bonding agent is responsible for the detachment and the operation failures. The inventors have further discovered that the foregoing problems can be effectively restrained by decreasing the areas of the conductive die pads, regardless of the sizes or the shapes of the semiconductor dies. 
       FIG. 3  to  FIG. 5  are the sectional views of the semiconductor modules  2 ,  3  and  4  according to the first to the third embodiments, illustrating the modes that enable the area of each conductive die pad to be decreased. Each mode can be used in combination with other modes or used alone. The following will first describe the configurations of the semiconductor modules  2 ,  3  and  4 , and then describe the advantages of the configurations. 
       FIG. 3  is a sectional view of the semiconductor module  2  according to the first embodiment. As described above, the conductive die pad  11   b  differs from the conductive die pad  11   a  of the comparative example in that the conductive die pad  11   b  is designed to have a smaller area than that of the conductive die pad  11   a  in a planar view. More specifically, the area of the conductive die pad  11   a  of the comparative example is approximately 6.1 mm 2 , and the area of the conductive die pad  11   b  of the present embodiment is approximately 5.0 mm 2 . Further, the amount and the viscosity of the conductive die bonding agent  14   a  are adjusted in advance so as not to run off of the conductive die pad  11   b . Therefore, the area of the conductive die bonding agent  14   a  in the planar view is also approximately 5.0 mm 2 . 
     The area of the conductive die pad  11   b  (and the conductive die bonding agent  14   a ) has been reduced, so that a distance X between the boundary of the conductive die pad  11   b  (and the conductive die bonding agent  14   a ) and the boundary of the semiconductor die  12   a  in the planar view decreases accordingly. 
     The distance X between the boundary of the conductive die pad  11   b  and the semiconductor die  12   a  in the planar view refers to a smallest distance among the distances of the perpendiculars between the sides constituting the boundary of the conductive die pad  11   b  (and the conductive die bonding agent  14   a ) and the corresponding sides of the semiconductor die  12   a . Hence, if the distance between an upper side of the conductive die pad  11   b  and an upper side of the semiconductor die  12   a  in the planar view is 0.1 mm, and the distance between the remaining sides of the conductive die pad  11   b  and the corresponding remaining sides of the semiconductor die  12   a  is 0.3 mm, then the distance X will be 0.1 mm. The distance X of the semiconductor module  10  in the comparative example is 0.125 mm, while the distance X of the semiconductor module  2  is 0.07 mm. 
     The advantageous effect of the embodiment obtained by the reduced area of the conductive die pad  11   b  (and the conductive die bonding agent  14   a ) will be discussed later. 
       FIG. 4A  is a sectional view of a semiconductor module  3  according to a second embodiment. For the second embodiment and after, the aspects common to the first embodiment or the comparative example will not be described, and only different aspects will be described. In particular, the same operation and effect obtained by the same configuration will not be described for each embodiment. 
     The semiconductor module  3  differs from the semiconductor module  2  according to the first embodiment in that a conductive die pad  11   c  and a conductive die pad  11   c ′ (a second conductive die pad) adjacent to the conductive die pad  11   c  are formed apart from each other. Further, semiconductor dies  12   a  and  12   b  (a second semiconductor die) are provided on the conductive die pads  11   c ′ and  11   c , respectively. The adjoining semiconductor dies  12   a  and  12   b  are electrically connected by at least one wire  13  (a second wire). 
     Providing the plurality of conductive die pads  11   c  and  11   c ′ formed apart on a plurality of adjacent semiconductor dies  12   a  and  12   b , respectively, by the wire  13  as described above makes it possible to decrease the areas of the conductive die pads. The amount and viscosity of conductive die bonding agents  14   a  and  14   c  (a second conductive die bonding agent) are adjusted to prevent the conductive die bonding agents  14   a  and  14   c  from running off of the conductive die pads  11   c  and  11   c ′ due to their surface tensions. This makes it possible to also decrease the areas of the conductive die bonding agents as the areas of the conductive die pads are decreased. 
       FIG. 4B  is a sectional view of a semiconductor module  3   a , which is a modification example of the semiconductor module  3  according to the second embodiment. The semiconductor module  3   a  differs from the semiconductor module  2  in that a solder resist  15  is provided on a region between adjoining semiconductor dies  12   a  and  12   b  (a third semiconductor die) on the conductive die pad  11   b . Therefore, conductive die bonding agents  14   a  and  14   b  (a third conductive die bonding agent) are blocked by the solder resist  15 , thus making it possible to decrease the surface areas of the conductive die bonding agents  14   a  and  14   b  to 4.9 mm 2 . Further, the solder resist  15  is provided adjacently to the semiconductor dies  12   a  and  12   b , so that the distance between the boundary of the conductive die bonding agents  14   a  and  14   b  and the semiconductor die  12   a  in the planar view can be further decreased to, for example, X=0.04 mm to 0.06 mm. 
       FIG. 5  is a sectional view of a semiconductor module  4  according to a third embodiment. The semiconductor module  4  differs from the semiconductor module  2  according to the first embodiment in that a solder resist  15 ′ (a second solder resist) is provided on a part of a conductive die pad  11   d , and the solder resist  15 ′ and a semiconductor die  12   b  are connected by an insulating die bonding agent  14   b  (insulating die bonding agent). Providing the semiconductor die  12   b , which is not required to be electrically connected to a bottom surface, on the solder resist  15 ′ makes it possible to restrain a conductive die bonding agent  14   a  from spreading with a resultant increased surface area thereof. Further, the insulating die bonding agent  14   b  is used, so that the area occupied by the conductive die bonding agent can be reduced. 
       FIG. 6A  illustrates the relationship between the area of a conductive die pad (and a conductive die bonding agent) and the occurrence rate of detachment in the hot and humid stress test.  FIG. 6B  illustrates the relationship between the area of the conductive die pad (and the conductive die bonding agent) and the operation failure rate in the hot and humid stress test. 
     As illustrated in  FIG. 6A  and  FIG. 6B , when the area of the conductive die pad (and the conductive die bonding agent) was 6.1 mm 2  (the comparative example), the sealing resin was detached in a part of 60% or more of the entire area of the product, and 40% or more of the semiconductor module incurred operation failures. When the area of the conductive die pad  11   b  (and the conductive die bonding agent  14   a ) was 5.0 mm 2  (the first embodiment), the detachment rate of the sealing resin remained below 40% of the entire area of the product, and below 10% of the semiconductor module incurred operation failures. 
     Even when the size of the semiconductor die  12   a  was changed, reductions in detachment and operation failure were verified if the area of the conductive die pad  11   b  (and the conductive die bonding agent  14   a ) was 5.0 mm 2 . For example, when the size of the semiconductor die  12   a  was, e.g., 1.16 mm×1.06 mm, the foregoing effect was verified. 
     Further, when the sum of the areas of the conductive die pads  11   c  and  11   c ′ (and the conductive die bonding agents  14   a  and  14   b ) was 4.9 mm 2  (the second embodiment and a modification example thereof), further reductions in detachment and operation failure were verified. It was possible to reduce the operation failure rate, in particular, to 0%. 
     In addition, when the area of the conductive die pad  11   c  was 3.2 mm 2  (the third embodiment), further reductions in detachment and operation failure were verified. It was possible to reduce, in particular, both the detachment occurrence rate and the operation failure to 0%. 
     Further, the results of similar hot and humid stress tests carried out on various configurations obtained by combining the foregoing configurations have revealed that, qualitatively, the detachment and operation failures can be reduced by decreasing the areas of the conductive die pads. For example, as illustrated by the second embodiment in comparison with the configuration of the comparative example, even if the surface area of the conductive die bonding agent is 5.0 mm 2  or more, the effect for reducing the detachment and the operation failures is obtained by adopting a configuration free of a conductive die bonding agent in a region between adjoining semiconductor dies, which are electrically connected by a wire, as compared with a configuration involving a conductive die bonding agent. Similarly, even if the surface area of the conductive die bonding agent is 5.0 mm 2  or more, the effect for reducing the detachment and the operation failures is obtained by using an insulating die bonding agent in the case of a semiconductor die that does not require the electrical connection from a bottom surface, as compared with the case involving the conductive die bonding agent, as illustrated by the third embodiment in comparison with the configuration of the comparative example. However, the operation failure rate in the hot and humid stress tests was dramatically decreased, regardless of the size of the semiconductor die, by setting the surface area of the conductive die pad (and the conductive die bonding agent) to 5.0 mm 2  or less. 
     Further,  FIG. 7A  illustrates the relationship between the distance X and the detachment occurrence rate in the hot and humid stress tests.  FIG. 7B  illustrates the relationship between the distance X and the operation failure rate in the hot and humid stress tests. The experiment results can be obtained mainly by further decreasing the size of the conductive die pad  11   b  of the semiconductor module  2 . 
     As illustrated in  FIG. 7A  and  FIG. 7B , when X was 0.125 mm (the comparative example), the sealing resin was detached in a portion of 60% or more of the entire area of the product, and 40% or more of the semiconductor module incurred operation failures. When X was 0.07 mm, the detachment rate of the sealing resin was below 40% of the entire area of the product, and below 10% of the semiconductor module incurred operation failures. 
     Even when the size of the semiconductor die  12   a  was changed, reductions in detachment and operation failure were verified when X was set to 0.07 mm. Further, it was possible to reduce the operation failure rate to 0% by further decreasing X to 0.06 mm, and to reduce the detachment occurrence rate to 0% by further decreasing X to 0.04 mm. 
     Thus, the detachment and the operation failures can be reduced by decreasing the distance X between the boundary of the semiconductor die and the boundary of the conductive die pad (and the boundary of the conductive die bonding agent that runs off of the conductive die pad) in the planar view. This is because, when a part of the conductive die bonding agent, which part exists in a gap between the conductive die pad and the semiconductor die, is compared with a part of the conductive die bonding agent, which part exists in a gap between the portion of the conductive die pad around the semiconductor die and the sealing resin, the latter conductive die bonding agent is considered to contribute to the detachment from the sealing resin and an operation failure. The foregoing effect is displayed when the area of the conductive die pad is set to 5.00 mm 2  or less; however, even if the area of the conductive die pad is larger than 5.00 mm 2 , the foregoing effect will be displayed by decreasing the distance X. 
     As described above, in the structure in which the conductive die bonding agent electrically connects the conductive die pad and the semiconductor die is sealed by a resin, setting the areas of the conductive die pad and the conductive die bonding agent to 5.00 mm 2  or less enables the operation failure rate to be reduced by approximately 30% in comparison with the cases where the areas are set to be larger than 5.00 mm 2 . When the foregoing setting of the areas is applied to all or nearly all the conductive die pads in a semiconductor module, the advantageous effect is more obvious. Alternatively, however, the setting of the areas may be applied to only several conductive die pads and the conductive die bonding agents (e.g. at least half the conductive die pads with the conductive die bonding agents included in the semiconductor module). Further, a part of the conductive die bonding agent may run off of a conductive die pad. 
     Decreasing the area of a conductive die pad leads to a higher possibility of the conductive die bonding agent running off of the conductive die pad and coming in contact with a wire bonding pad  18 , resulting in an operation failure. Hence, as illustrated in  FIG. 8 , the edge of a conductive die pad  11   e  may be formed to have an inverse tapered shape (shaped to expand in the opposite direction from the surface of a PCB base  16 ), and on a section perpendicular to the surface of the PCB base  16 , an angle of contact α with the PCB base  16  may be set to an obtuse angle so as to increase the surface tension relative to the conductive die bonding agent  14   a  thereby to restrain the conductive die bonding agent  14   a  from running off. 
     The following will describe the manufacturing method for the conductive die pad  11   e . First, a mask (not illustrated) is attached to the surface of the PCB base  16  not provided with the conductive die pad  11   e . The mask has an acute contact angle with respect to the surface of the PCB base  16 . With the mask attached, the conductive die pad  11   e  is formed by plating or the like. Since the mask has the acute contact angle with respect to the surface of the PCB base  16 , the conductive die pad  11   e  can be formed to have the inverse tapered shape with the obtuse contact angle α. 
     Thus, forming the edge of the conductive die pad  11   e  into the inverse tapered shape makes it possible to increase the angle of contact with the conductive die bonding agent and therefore to restrain the conductive die bonding agent from running off. This enables the conductive die pad  11   e  to have a reduced area. As a result, the area of the conductive die pad  11   e  exposed to the sealing resin  17  makes it possible to decrease the area of the conductive die bonding agent opposing thereto, thus enabling the occurrence of detachment, which is attributable to the conductive die bonding agent, to be restrained. Alternatively, only a part of the edge of the conductive die pad  11   e  rather than the entire edge may be formed to the inverse tapered shape. 
     Further, the material of the conductive die bonding agent may be changed to a material which has a higher thermal conductivity than that of a conventional material. In the case of the comparative example, the entire bottom surface of the semiconductor die  12   a  has the wet spread of the conductive die bonding agent  14   a  in order to satisfy required heat dissipation characteristics. On the other hand, using a conductive die bonding agent having a higher thermal conductivity, e.g., a conductive die bonding agent  14   d  of 2.5 [W/m·K] or more, makes it possible to satisfy a specification even if the area of the conductive die bonding agent is reduced. 
     For example, almost the entire or the entire conductive die bonding agent  14   d  may be formed to remain within the region occupied by the semiconductor die  12   a  provided on the conductive die pad  11   b  in the planar view, as illustrated in  FIG. 9 . In other words, it can be said that, in the planar view, a region of the outer edge (a fourth region) exposed to the sealing resin in the region occupied by the conductive die pad  11   b  surrounds a region (a third region) covered by the conductive die bonding agent  14   d.    
     Further, as illustrated in  FIG. 10 , a configuration may be adopted, in which a plurality of heat dissipation vias  19   d  are formed in a region occupied by a conductive die bonding agent  14   e  in the planar view in order to improve the heat dissipation. The vias  19   d  formed in the substrate are filled with a metal, thus providing high heat dissipation effect. Therefore, the wet spread area of the conductive die bonding agent  14   e  can be reduced, and the heat dissipation characteristics can be maintained while restraining the conductive die bonding agent  14   e  from running off of the conductive die pad  11   b , by providing the conductive die pad  11   b  and the conductive die bonding agent  14   e  such that the plurality of vias  19   d  are included in the region occupied by the conductive die bonding agent  14   e.    
     Further, a configuration that combines the conductive die bonding agent  14   d  having a higher thermal conductivity and the foregoing configuration may be adopted to further reduce the wet spread area of the conductive die bonding agent  14   d . In addition, the area of the wet spread can be reduced also by introducing a conductive die bonding agent  14   e  with a higher viscosity. For example, even in a case where a conductive die bonding agent with a regular viscosity (a sixth conductive die bonding agent) is used and runs off of the conductive die pad  11   b  and comes in contact with the PCB base  16 , it is possible to maintain a larger contact angle to restrain the wet spread by using the conductive die bonding agent  14   e  having a higher viscosity (e.g. 8000 [cP] or more). 
     Further, in place of a conductive die bonding agent, a conductive die attach film (DAF) may be used to connect a semiconductor die and a conductive die pad in a region where the possibility of the occurrence of at least the detachment is likely to be high. With this arrangement, the wet spread problem can be eliminated. 
     Further, as illustrated in  FIG. 11 , a configuration may be adopted, in which a groove  20  is formed in the PCB base  16  to stop the wet spread of the conductive die bonding agent  14   c  that runs off of the conductive die pad  11   b . For example, even if the conductive die bonding agent  14   c  runs off, the conductive die bonding agent will flow into the groove  20  formed in the surface of the PCB base  16  between the semiconductor die  12   a  and the wire bonding pad  18  connected with the semiconductor die  12   a  by the wire  13 , thus enabling an operation failure to be restrained. 
     Each of the configurations may be used alone or may be combined. Further, the configurations can be applied regardless of the area of a conductive die pad (and a conductive die bonding agent). 
     The following will describe a fourth embodiment. 
     For the fourth embodiment and after, the aspects common to the first embodiment will not be described, and only different aspects will be described. In particular, the same operation and effect obtained by the same configuration will not be described for each embodiment. 
     A semiconductor module according to the present embodiment has a configuration in which a semiconductor die and a plurality of conductive die pads formed apart are bonded by a conductive die bonding agent. The conductive die bonding agent electrically connects at least one conductive die pad and a semiconductor die, and electrically connects another conductive die pad, which is formed apart from the foregoing conductive die pad, and the semiconductor die, and covers a region between the semiconductor die and a substrate, the region being located between the conductive die pads. 
     For example,  FIG. 12A  illustrates a configuration which has nine conductive die pads  11   f  formed apart from each other and a semiconductor die  12   a  electrically connected with at least a part of each of the conductive die pad  11   f  through a conductive die bonding agent  14   a  (not illustrated). In the planar view, therefore, the semiconductor die  12   a  has regions that overlap at least a part of each of the conductive die pads  11   f.    
     Thus, the conductive die pads  11   f  are provided, being divided into smaller segments arranged in a mesh-like pattern. With this arrangement, the conductive die bonding agent  14   a  provides the electrical connection between each of the conductive die pads  11   f  and the semiconductor die  12   a . In addition, the conductive die bonding agent  14   a  is positioned in the gaps between the conductive die pads  11   f  and the semiconductor die  12   a  so as to provide contact with the surface of a PCB base  16  having a height and a material that are different from those of the conductive die pads  11   f , thus making it possible to restrain the detachment by the enhanced adhesive strength due to an anchoring effect based on the difference in height. 
     As illustrated in  FIG. 12B , the conductive die pads  11   f  arranged in the mesh-like pattern may be provided, in a via land shape, as annular conductive die pads connected to the vias  19   d , which are passed through a part of or the entire PCB base  16 . In this case, the heat dissipation effect of the via land can be expected in addition to the anchoring effect, so that the occurrence of the detachment can be prevented due to the restraint of the wet spread of the conductive die bonding agent  14   a.    
     The following will describe a fifth embodiment. 
     As illustrated in  FIG. 13 , a semiconductor module  5  includes a PCB base  16  (substrate), on which a conductive die pad  11   g  and a semiconductor die  12   a  provided on the conductive die pad  11   g  are placed, the conductive die pad  11   g  and the semiconductor die  12   a  being electrically connected by a conductive die bonding agent  14   a . Further, adjacently to the conductive die pad  11   g , a wire bonding pad  18  and a metal wire provided continuously from the wire bonding pad  18  are formed. The semiconductor die  12   a  and the wire bonding pad  18  are electrically connected by a wire  13 . Further, the semiconductor die  12   a , the conductive die pad  11   g , the conductive die bonding agent  14   a , the wire  13 , the wire bonding pad  18  and the like are sealed by a sealing resin  17 . 
     In the present embodiment, the surface of the wire bonding pad  18  is made of Cu plated with Au or an alloy containing Au, such as NiPdAu. Hence, the wire bonding pad  18  can be ideally attached to the wire  13  made of, in particular, gold or the like. 
     The conductive die pad  11   g , on which the semiconductor die  12   a  having the other end of the wire  13  is provided, is not plated with an alloy containing Au. The conductive die pad  11   g , including its surface, is made of Cu. Further, the Cu, which is the material of the conductive die pad  11   g , and the semiconductor die  12   a  are electrically connected by the conductive die bonding agent  14   a.    
     The structure described above can be obtained according to the method illustrated in  FIGS. 14A-14B . 
     First, Cu is used to form the wire bonding pad  18 , the wires connected thereto and the conductive die pad  11   g  on the PCB base  16 . Then, a solder resist is applied to the wires excluding the wire bonding pad  18  to protect the wires. Subsequently, a mask film  21  is attached to the conductive die pad  11   g , the Cu of which is to be exposed, and then the conductive die pad  11   g  with the mask film  21  on is placed in an Au plating tank to carry out Au plating ( FIG. 14A ). 
     As a result, the conductive die pad  11   g  with the mask film  21  attached thereto, including the surface thereof, is formed of Cu, and the surface of the wire bonding pad  18  is plated with NiPdAu. Thereafter, the semiconductor die  12   a  is bonded onto the conductive die pad  11   g  by the conductive die bonding agent  14   a , and the entire workpiece is sealed by the sealing resin  17 . 
     The semiconductor module  5  described above can be accomplished by the aforesaid manufacturing process. Alternatively, Au may be plated on the surface of the conductive die pad  11   g  without attaching the mask film  21 , and then the plating may be removed using a laser  22  to expose the Cu surface, as illustrated in  FIG. 14B . 
       FIG. 15  is a graph illustrating the comparison of the gain fluctuation values after the hot and humid stress test between the case where NiPdAu is used as the material of the surface of the conductive die pad and the case where Cu is used as the material. As illustrated in the graph, a gain fluctuation value below 1 dB has been achieved in the latter case in contrast to the former case where the gain fluctuation value was 1.6 dB or more. 
     The above has described the illustrative embodiments of the present disclosure. 
     The semiconductor module  2  described above with regard to  FIG. 3 , for example, includes the PCB base  16 , the conductive die pad  11   b  placed on the substrate, the semiconductor die  12   a  provided on the conductive die pad  11   b , the conductive die bonding agent  14   a  that electrically connects the conductive die pad  11   b  and the semiconductor die  12   a , the wire bonding pad  18  provided on the PCB base  16 , the wire  13  that electrically connects the wire bonding pad  18  and the semiconductor die  12   a , and the sealing resin  17  that seals at least the conductive die pad  11   b , the semiconductor die  12   a , the conductive die bonding agent  14   a , the wire bonding pad  18 , and the wire  13 . In the planar view, the area of the conductive die pad  11   b  is 5.0 mm 2  or less. 
     This arrangement makes it possible to provide a semiconductor module that restrains the detachment between a conductive die bonding agent and a conductive die pad or a semiconductor die and to restrain an operation failure. Further, in the planar view, the minimum value of the distance X between the boundary of the conductive die pad  11   b  and the semiconductor die  12   a  may be 0.07 mm or less. With this arrangement, the amount of the conductive die bonding agent  14   a  that runs off of the semiconductor die  12   a  and is exposed to the sealing resin  17  can be reduced, thus enabling the detachment to be restrained. 
     Further, as shown in  FIG. 4A , the conductive die pad  11   c  provided adjacently to and apart from the conductive die pad  11   c ′, the semiconductor die  12   b  provided on the conductive die pad  11   c , the conductive die bonding agent  14   c  that electrically connects the conductive die pad  11   c  and the semiconductor die  12   b , and the wire  13  that electrically connects the semiconductor die  12   a  and the semiconductor die  12   b  may be provided on the PCB base  16 . With this arrangement, the conductive die pads are divided between adjoining semiconductor dies, thus making it possible to restrain the wet spread of the conductive die bonding agent. 
     Further, as shown in  FIG. 4B , the semiconductor die  12   b  provided adjacently to the semiconductor die  12   a , the conductive die bonding agent  14   b  that electrically connects the conductive die pad  11   b  and the semiconductor die  12   b  may be provided on the conductive die pad  11   b , and the solder resist  15  provided in the gap between the semiconductor die  12   a  and the semiconductor die  12   b  may be provided on the conductive die pad  11   b . With this arrangement, the solder resist  15  provided between the semiconductor dies restrains the wet spread of the conductive die bonding agent  14   a  into the region. 
     Further, as shown in  FIG. 5 , the second solder resist  15 ′ provided adjacently to the semiconductor die  12   a , a fourth semiconductor die  12   b  provided on the second solder resist  15 ′, and the insulating or conductive die bonding agent  14   b  that connects the fourth semiconductor die  12   b  and the second solder resist  15 ′ may be provided on the conductive die pad  11   d . With this arrangement, for a semiconductor die that does not require electrical connection from the bottom surface, the insulating die bonding agent is provided, thus making it possible to restrain the occurrence of the detachment or the like attributable to a conductive die bonding agent. 
     On at least one section perpendicular to the surface of the PCB base  16 , the conductive die pad  11   e  may be formed to have an inverse tapered shape having the obtuse contact angle α with respect to the PCB base  16  so as to expand in the opposite direction from the surface of a PCB base  16 , as shown in  FIG. 8 . This arrangement makes it possible to restrain the conductive die bonding agent from running off. 
     The conductive die pad  11   b  has the third region covered by the conductive die bonding agent  14   d , and the fourth region exposed to the sealing resin  17 , as shown in  FIGS. 9 and 11 . In the planar view, the third region may be surrounded by the fourth region. With this arrangement, the surface area of the conductive die bonding agent can be reduced, thus making it possible to restrain the occurrence of the detachment attributable to the conductive die bonding agent. 
     Further, as shown in  FIG. 10 , a plurality of vias  19   d  may be provided in the third region in the planar view. The plurality of vias  19   d  are passed through the PCB base  16  and have therein a metal electrically connected with the conductive die pad  11   b . This arrangement enables heat to be dissipated from the plurality of vias  19   d , so that required heat dissipation characteristics can be maintained even when the amount of the conductive die bonding agent is decreased. 
     As the conductive die bonding agent, the conductive die bonding agent  14   e  may be used. The conductive die bonding agent  14   e  has a viscosity that is higher than the viscosity of the conductive die bonding agent  14   a  that runs off of the conductive die pad  11   b  and comes in contact with the PCB base  16  when the same amount as that of the conductive die bonding agent  14   e  is used, and also has a higher angle of contact than the angle of contact between the conductive die bonding agent  14   a  and the PCB base  16 . With this arrangement, the wet spread of the conductive die bonding agent  14   e  can be restrained. 
     Further, as shown in  FIG. 11 , the groove  20  is formed in the region between the conductive die pad  11   b  and the wire bonding pad  18  on the PCB base  16 , and a part of the conductive die bonding agent  14   c  may flow into the groove  20 . This arrangement enables the wet spread of the conductive die bonding agent  14   e  to be restrained, so that the detachment due to the wet spread can be restrained. 
     Further, as shown in  FIG. 13 , the semiconductor module  5  includes the PCB base  16 , the conductive die pad  11   g  which is provided on the PCB base  16  and the surface material of which is Cu, the semiconductor die  12   a  provided on the conductive die pad  11   g , the conductive die bonding agent  14   a  that electrically connects the conductive die pad  11   g  and the semiconductor die  12   a , the wire bonding pad  18  which is provided on the PCB base  16  and the surface material of which is a metal containing Au, and the wire  13  that electrically connects the wire bonding pad  18  and the semiconductor die  12   a . This arrangement makes it possible to provide a semiconductor module that exhibits improved gain characteristics, as compared with the case where a conductive die pad using Au as its surface material is adopted. 
     A metal wire to be connected to the wire bonding pad  18  may be further provided, and the conductive die pad  11   g  and the metal wire may be formed using the same metal material containing Cu. With this arrangement, the conductive die pad and the metal wire can be formed in the same process. 
     Further, as shown in  FIG. 12A , the semiconductor module may include the PCB base  16 , the first conductive die pad  11   f  provided on the PCB base  16 , the second conductive die pad  11   f  provided adjacently to and apart from the first conductive die pad  11   f  on the PCB base  16 , the semiconductor die  12   a , and the conductive die bonding agent  14   a  which is in contact with the first conductive die pad  11   f , the second conductive die pad  11   f , and the PCB base  16  in the gap between the first conductive die pad  11   f  and the second conductive die pad  11   f  and which electrically connects the first conductive die pad  11   f  and the second conductive die pad  11   f  to the semiconductor die  12   a . According to this configuration, the conductive die bonding agent is in contact with both the conductive die pads and the substrate, thus making it possible to further restrain the detachment by the anchoring effect. 
     Further, as shown in  FIG. 12B , the vias  19   d  may be provided, which are passed through the PCB base  16  and which have therein metals to be electrically connected with the conductive die pads  11   f ′, and the vias  19   d  may be provided, which are passed through the PCB base  16  and which have therein metals to be electrically connected with the conductive die pads  11   f ′. With this arrangement, heat can be dissipated through the vias, so that the conductive die bonding agent that is responsible for the detachment can be decreased. 
     Further, a first conductive die pad may be formed to be annular and connected to a first via  19   d , and a second conductive die pad may be formed to be annular and connected to a second via  19   d . With this arrangement, conductive die pads can be provided by making use of a via land. 
     The embodiments described above are intended for easy understanding of the present disclosure, and are not to be considered as limiting the present disclosure. The present disclosure can be modified or improved without departing from the spirit thereof, and the present disclosure covers equivalents thereof. More specifically, anything obtained by adding design alterations, as necessary, to the embodiments by persons skilled in the art will be encompassed by the scope of the present disclosure insofar as the features of the present disclosure are included. For example, the elements used in the embodiments and the placement, the materials, the conditions, the shapes, the sizes, and the like of the elements are not limited to those illustrated and may be changed, as appropriate. Further, it is needless to say that the embodiments are illustrative, and configurations illustrated in different embodiments can be partly replaced or combined, and these are to be covered by the scope of the present disclosure insofar as the features of the present disclosure are included.