Semiconductor module and resin case

A semiconductor module includes a base substrate, a semiconductor element provided on the front surface side of the base substrate, and a resin case bonded to the front surface of the base substrate and enclosing a region in which the semiconductor element is provided, wherein the resin case has a depressed portion formed in a height direction away from the base substrate in a bottom surface bonded to the base substrate, and a connection hole that connects the depressed portion and the exterior of the resin case.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of foreign priority to Japanese Application 2015-057925 filed on Mar. 20, 2015, in the Japanese Patent Office, the disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a semiconductor module and a resin case.

2. Related Art

A semiconductor module that houses a semiconductor element such as an IGBT is already known. The semiconductor module is such that a semiconductor element provided on a base substrate is enclosed by a resin case, and the semiconductor element and an external electronic part are connected by a connection terminal provided on the resin case (for example, refer to JP-A-2008-294362).

SUMMARY

A void may occur in a thick part of a resin case because the amount of resin contraction accompanying cooling when molding the resin case is large. In order to reduce the occurrence of voids, providing in advance a thinned (also called a lightened) portion not filled with resin material in the thick portion of the resin case is conceivable.

The thinned portion is sealed by the resin case being bonded to a base substrate. However, a gaseous body inside the thinned portion of the resin case expands due to a process such as the semiconductor module being heated or exposed to a vacuum atmosphere. Further, the expanded gaseous body may exert stress on the bonding portion bonding the resin case and the base substrate, whereby the bonding portion becomes detached.

A first aspect of the disclosure provides a semiconductor module including a base substrate, a semiconductor element provided on the front surface side of the base substrate, and a resin case bonded to the front surface of the base substrate and enclosing a region in which the semiconductor element is provided, wherein the resin case has a depressed portion formed in a height direction away from the base substrate in a bottom surface bonded to the base substrate, and a connection hole that connects the depressed portion and the exterior of the resin case.

A second aspect of the disclosure provides a resin case bonded to the front surface of a base substrate on the front surface side of which a semiconductor element is provided and enclosing a region in which the semiconductor element is provided, the resin case including a depressed portion formed in a height direction away from the base substrate in a bottom surface bonded to the base substrate, and a connection hole that connects the depressed portion and the exterior of the resin case.

The heretofore described outline of the disclosure does not detail all the characteristics of the invention. Also, sub-combinations of these characteristic groups may be included in the invention.

DESCRIPTION OF EMBODIMENTS

Hereafter, the invention will be described via an embodiment of the disclosure, but the embodiment does not limit the invention according to the scope of the claims. Also, not all combinations of characteristics described in the embodiment are necessarily essential to the solution proposed by the disclosure.

FIG. 1is a diagram showing a semiconductor module100according to an embodiment of the disclosure.FIG. 1shows a perspective view of the semiconductor module100. The semiconductor module100has a base substrate10, a resin case20, and an internal circuit of a semiconductor element12and the like.

The internal circuit of the semiconductor element12and the like is disposed on the front surface side of the base substrate10. The semiconductor element12is a power semiconductor element such as an IGBT. An insulating layer, or an insulating layer on both surfaces of which a metal layer is formed, may be provided between the internal circuit and the base substrate10. The base substrate10is formed of a material such as copper, which has higher thermal conductivity than resin.

The resin case20is bonded to the front surface of the base substrate10. Also, the resin case20is such that a joining member such as a screw is inserted into a hole portion22. The resin case20is provided so as to enclose a region14in which the internal circuit is provided. The resin case20of this example has a wall portion28and wall portion30enclosing the region14.

The wall portion30is a wall that is thicker than the wall portion28. That is, the wall portion30is the thickest of the wall portions in the resin case20. The resin case20may have four wall portions enclosing the four sides of the region14. Also, a continuous region of practically equal thickness in the resin case20may be taken to be one wall portion. That is, the wall portion30may refer to the continuous region having the greatest thickness in the resin case20. The thickness of a wall portion refers to the thickness between the internal wall on the region14side and the external wall opposing the internal wall. The bottom surfaces of the wall portion28and wall portion30are bonded to the front surface of the base substrate10. Also, the wall portion28and wall portion30are provided extending in a direction perpendicular to the front surface of the base substrate10. The wall portion28and wall portion30may be formed integrally.

In this example, a sealing portion16that seals at least one portion of the internal circuit of the semiconductor element12and the like is provided in the region14enclosed by the resin case20. The sealing portion16is provided to a predetermined height from the front surface of the base substrate10. InFIG. 1, the position of the height direction in which the sealing portion16is formed is indicated by a broken line. The sealing portion16may have a height such that all the semiconductor element12can be sealed, and may have a height such that wiring in the internal circuit can be sealed.

One or more connection terminals24are provided in at least one portion of the wall portion28and wall portion30. Each connection terminal24in this example is inserted in the surfaces of the wall portion28and wall portion30on the side opposite to that of the base substrate10. InFIG. 1, the connection terminal24is provided in only the surface of one wall portion28, but the connection terminal24may also be provided in the other wall portions28and the wall portion30. An end portion of the connection terminal24on the side inserted into the resin case20is electrically connected to the internal circuit of the semiconductor element12and the like. Also, an end portion of the connection terminal24on the side not inserted into the resin case20is inserted into an insertion hole of an electrical part, such as a printed circuit board, provided opposing the semiconductor module100.

Also, the semiconductor module100may further include a cover portion covering the region14. The cover portion may be fixed to the front surface of at least one portion of the wall portion28and the wall portion30. The wall portion30of this example has one or more nuts26that fix the cover portion or a conductive member to the front surface of the wall portion30. The nut26may be inserted into or housed in a depressed portion formed in the front surface of the wall portion30. The cover portion may be an electrical part, such as a printed circuit board, connected to the semiconductor module100. The conductive member may be a metal part, such as a copper wire or copper plate, that electrically connects the semiconductor module100and a power source or load.

FIG. 2is a diagram showing an example of a bottom surface31of the resin case20. As heretofore described, an adhesive that bonds the base substrate10and the resin case20is applied to the bottom surface31. The adhesive is applied so as to pass unbroken at least once around the multiple of wall portions28and the wall portion30. That is, the adhesive is applied to the bottom surface31so as to enclose unbroken the region14.

A multiple of depressed portions32are provided in the resin case20. The depressed portion32is formed in a height direction from the bottom surface of the resin case20, away from the base substrate10. Of the wall portions, the depressed portion32of this example is provided in at least the wall portion30, which has the greatest thickness. The depressed portion32has an aperture in the bottom surface of the wall portion30, and extends in a height direction perpendicular to the front surface of the base substrate10. The depressed portion32may be formed in a multiple of wall portions that have a thickness of a pre-specified value or greater.

The sizes of the apertures of the multiple of depressed portions32may be the same, or may differ. In this example, the multiple of depressed portions32are arrayed linearly, and the aperture areas of the depressed portions32at either end are smaller than the aperture areas of the other depressed portions32. The depressed portions32are separated by separating walls35. The separating wall35is one portion of the wall portion30. The thickness of the separating wall35may be the same as that of the wall portion28, which has the smallest thickness, or may be smaller.

FIG. 3shows a sectional view of the wall portion30according to a comparison example.FIG. 3shows an A-A section ofFIG. 2. A projection38that comes into contact with the outer periphery of the base substrate10, thereby positioning the base substrate10, may be provided in the wall portion30. The projection38may be provided along the outer periphery of the resin case20. Also, a screw fixing hole36is formed in the front surface of the wall portion30. Also, a depressed portion27into which the nut26shown inFIG. 1is inserted is formed on the upper side of the screw fixing hole36. By the nut26being provided in the depressed portion27, the nut26is provided neighboring the screw fixing hole36. By a screw or the like being inserted into the screw fixing hole36and the nut26, the cover portion, the conductive member, or the like, is fixed to the front surface of the wall portion30. At least one screw fixing hole36may be provided in a position opposing one of the depressed portions32.

The wall portion30has an internal wall54on the region14side, and an external wall56opposing the internal wall54. The depressed portion32is provided between the internal wall54and the external wall56. The depressed portion32is formed so that the width remaining between the external wall56or the internal wall54and the depressed portion32is equal to or greater than the width of the wall portion28, which has the smallest thickness. The depressed portion32may be formed in the center between the internal wall54and the external wall56.

A bonding portion34is formed on the bottom surface of the wall portion30. The bonding portion34is formed so as to enclose the depressed portion32. Therefore, the depressed portion32is sealed by the base substrate10and the resin case20. After bonding the resin case20to the base substrate10, the sealing portion16is formed in the region14.

The sealing portion16is formed of a material that has fluidity before a predetermined process such as heating and is hardened by the predetermined process, as is the case with silicone gel. Also, the material of the sealing portion16has insulating properties.

When injecting a material such as silicone gel, it is preferable that the material is injected in a vacuum atmosphere in order to prevent moisture and air bubbles from being mixed with the material. However, when the semiconductor module100is exposed to a vacuum atmosphere after the resin case20is bonded to the base substrate10, a gaseous body inside the depressed portion32expands.

Also, the gaseous body inside the depressed portion32also expands when heating the semiconductor module100in order to harden the material such as silicone gel. When the gaseous body inside the depressed portion32expands due to these kinds of process, stress is exerted on the bonding portion34, and the bonding portion34may become detached. In this case, a failure occurs in that silicone gel or the like leaks out from the detached portion of the bonding portion34.

Releasing the gaseous body inside the depressed portion32between bonding portions34by applying the bonding portion34discretely is conceivable. However, the bonding strength decreases. Also, it is difficult to accurately control the interval between bonding portions34.

FIG. 4Ashows a sectional view of the wall portion30according to a first example. The wall portion30of this example differs from the configuration of the wall portion30shown inFIG. 3in further including a connection hole40. The configuration other than the connection hole40is the same as that of the wall portion30shown inFIG. 3.

The connection hole40connects the depressed portion32and the exterior of the resin case20. Therefore, even when the gaseous body inside the depressed portion32expands, the gaseous body can be released to outside the resin case20. Therefore, detachment of the bonding portion34can be prevented.

The depressed portion32has an apex portion33on the side opposite to that of the base substrate10. The apex portion33refers to a place in the depressed portion32in which the distance from the front surface of the base substrate10is the greatest. The depressed portion32of this example has a cuboid form. The surface of the cuboid on the side opposite to that of the base substrate10corresponds to the apex portion33. The connection hole40connects the apex portion33of the depressed portion32and the exterior of the resin case20. The connection hole40has an aperture42on the exterior side of the resin case20, and an aperture44on the depressed portion32side.

The exterior side aperture42in this example is formed in the bottom surface of the screw fixing hole36. Also, the depressed portion32side aperture44is formed in the apex portion33of the depressed portion32. It is preferable that the diameter of the exterior side aperture42is smaller than the inner diameter of the screw fixing hole36. By narrowing the connection hole40, thereby restricting a reduction in thickness, the gaseous body can be released to outside the resin case20without the strength of the resin case20being lost. Also, by narrowing the connection hole40, the possibility of a foreign object contaminating the inside of the depressed portion32can be reduced. Also, the screw fixing hole36is blocked with a screw or the like after the sealing portion16is formed. Therefore, when forming the sealing portion16, contamination of the depressed portion32by a foreign object can be prevented after fixing the screw, while connecting the interior of the depressed portion32to the exterior of the resin case20. The screw or the like inserted into the screw fixing hole36may be provided so as not to reach the connection hole40. The diameter of the connection hole40may be smaller than the diameter of the screw or the like. InFIG. 4A, dsrepresents the diameter of the screw or the like when received in the nut26and accommodated in the screw fixing hole26.

The connection hole40may be formed to extend perpendicular to the base substrate10in the height direction from the apex portion33of the depressed portion32. Also, the connection hole40may have a bent portion that bends in a place between the depressed portion32side aperture44and the aperture42on the exterior side of the resin case20. In this case, the possibility of a foreign object falling into the depressed portion32can be reduced.

The diameter of the aperture42of the connection hole40may be one-half or less the inner diameter of the screw fixing hole36. The area of the aperture44of the connection hole40may be one-half or less the area of the apex portion33of the depressed portion32. Also, the diameter of the aperture44of the connection hole40may be one-half or less the width of the depressed portion32. The width of the depressed portion32refers to the width in a direction from the internal wall54toward the external wall56. The area of the apex portion33of the depressed portion32may be greater than the area of the bottom surface of the screw fixing hole36. The connection hole40may have a uniform thickness from the aperture42to the aperture44.

The aperture42of the connection hole40may be provided in the center of the bottom surface of the screw fixing hole36. Also, the aperture44of the connection hole40may be provided in the center of the apex portion33of the depressed portion32. The diameter of the aperture42may be the same as the diameter of the aperture44, or may be smaller.

FIG. 4Bis a diagram showing the front surface of the wall portion30according to the first example. As heretofore described, the connection hole40is provided in the bottom surface of the screw fixing hole36. The sectional form of the connection hole40may be a circular form, or may be an elliptical or oval form. InFIG. 4B, the connection hole40is shown with an oval sectional form. It is preferable that the ellipsoid or oval has the long axis thereof in a direction parallel to the wall portion30(or to the external wall56and internal wall54). In this case, the decrease in thickness between the external wall56and the internal wall54can be reduced, and the gaseous body can be released to outside the resin case20without the strength of the resin case20being lost.

The nut26, not shown in the drawing, is disposed in the depressed portion27. In this example, the screw fixing hole36is formed in the vicinity of the center of the depressed portion27. The nut26is of an approximate regular hexagonal prism form, and the depressed portion27too may be of a hexagonal prism form that can house the nut26. The screw fixing hole36disposed on the bottom surface side of the depressed portion27is of a cylindrical form. In this example, the axis of the depressed portion27and the axis of the screw fixing hole36may coincide. The connection hole40may be provided in the vicinity of these axes, that is, in the vicinity of the center of the screw fixing hole36. It is further preferable that the depressed portion27is disposed so that two opposing faces of the depressed portion27are parallel to the external wall56and the internal wall54. As the long axis of the connection hole40is positioned in the vicinity of a plane including the two opposing faces of the depressed portion27in this case, cracking of the resin case20that may occur when inserting a screw in the nut26and applying torque can be prevented.

FIG. 4Cshows a sectional view of the wall portion30according to a modification example of the first example. The wall portion30of this example differs from the configuration of the wall portion30shown inFIG. 4Ain that one depressed portion32includes a multiple of connection holes40. Other than including the multiple of connection holes40, the configuration may be the same as that of the wall portion30shown inFIG. 4A.

Each connection hole40connects the apex portion33of the depressed portion32and the bottom surface of the screw fixing hole36. The form of each connection hole40may be the same as that of the connection hole40described inFIG. 4A. However, the sum of the diameters of the apertures of the connection holes40on the exterior side of the resin case20may be one-half or less of the inner diameter of the screw fixing hole36. In this example, the diameter of each of the connection holes40can be reduced, because of which a large foreign body can be prevented from contaminating the inside of the depressed portion32. The diameter of each of the connection holes40may be the same. Also, the diameter of each of the connection holes40may differ.

FIG. 4Dshows the front surface of the wall portion30according to a modification example of the first example. In the example ofFIG. 4C, the multiple of connection holes40are arrayed in a direction perpendicular to the external wall56and internal wall54, but the multiple of connection holes40of this example are arrayed in parallel to the wall portion30(or to the external wall56and the internal wall54) in the center of the screw fixing hole36. In this case, the decrease in thickness between the external wall56and the internal wall54can be reduced, and the gaseous body can be released to outside the resin case20without the strength of the resin case20being lost. The nut26, not shown in the drawing, is disposed in the depressed portion27. The forms and dispositions of the depressed portion27and the screw fixing hole36are the same as in the example shown inFIG. 4B. The multiple of connection holes40may be provided in the vicinity of the axes of the depressed portion27and the screw fixing hole36, that is, in the vicinity of the center of the screw fixing hole36. By the multiple of connection holes40being disposed in the vicinity of a plane including the two opposing faces of the depressed portion27, cracking of the resin case20that may occur when inserting a screw in the nut26and applying torque can be prevented.

FIG. 5Ashows a sectional view of the wall portion30according to a second example. The wall portion30of this example is such that the position in which the connection hole40is provided differs from that in the configuration of the wall portion30shown inFIGS. 4A to 4D. Other than the position of the connection hole40, the configuration is the same as that shown inFIGS. 4A through 4D.

The connection hole40of this example connects the depressed portion32and the external wall56of the wall portion30. That is, the connection hole40has the aperture44provided in the depressed portion32and an aperture46provided in the external wall56. The depressed portion32side aperture44of the connection hole40is provided in a side face of the depressed portion32. The side face of the depressed portion32is a face extending in the height direction from, for example, the front surface side of the base substrate10.

The connection hole40of this example extends in a horizontal direction approximately parallel to the front surface of the base substrate10. The external wall56side aperture46and the depressed portion32side aperture44are provided toward the apex portion33between the front surface of the base substrate10and the apex portion33of the depressed portion32. The positions of the aperture44and the aperture46are regulated by the center or center of gravity position of each aperture. That is, a height h2of the center position of the aperture44and the aperture46, with the front surface of the base substrate10as a reference, is greater than one-half of a height h1of the apex portion33.

An outer peripheral portion of the base substrate10and the resin case20warps in accordance with the difference between the thermal expansion coefficients of the base substrate10and the resin case20. By the connection hole40being provided toward the apex portion33, the amount of resin to the base substrate10side of the connection hole40can be increased, because of which the strength of the resin case20can be maintained. It is preferable that the diameters of the aperture44and the aperture46of the connection hole40are one-half or less of the height h1of the apex portion33. Therefore, the strength of the resin case20can be maintained. The diameters of the aperture44and the aperture46of the connection hole40may be one-quarter or more of the height h1.

Also, the depressed portion32may be provided toward the external wall56between the internal wall54and external wall56of the wall portion30. In this case, the connection hole40can be shortened. Also, the depressed portion32may be provided toward the internal wall54. In this case, the thickness on the side on which the connection hole40is provided can be increased.

FIG. 5Bshows a sectional view of the wall portion30according to a modification example of the second example. The wall portion30of this example is such that the form of the connection hole40differs from that of the configuration of the wall portion30shown inFIG. 5A. Other than the form of the connection hole40, the configuration may be the same as that of the wall portion30shown inFIG. 5A.

The connection hole40of this example extends in a direction nearing the base substrate10in at least one region from the depressed portion32side aperture44toward the external wall56side aperture46. That is, the connection hole40of this example extends downward of the horizontal direction (toward the base substrate10) in at least one region from the depressed portion32side aperture44toward the external wall56side aperture46.

The connection hole40shown inFIG. 5Bextends downward of the horizontal direction in all regions from the depressed portion32side aperture44toward the external wall56side aperture46. The connection hole40may descend vertically toward the front surface of the base substrate10in one region from the depressed portion32side aperture44toward the external wall56side aperture46. According to this kind of configuration, foreign objects can be prevented from infiltrating from the connection hole40.

FIG. 6shows a sectional view of the wall portion30according to a third example. The wall portion30of this example is such that the form of the connection hole40differs from that of the wall portion30shown inFIGS. 4A through 4D. Other than the form of the connection hole40, the configuration may be the same as that of the wall portion30shown inFIGS. 4A through 4D.

The connection hole40of this example connects the depressed portion32and the internal wall54of the wall portion30. That is, the connection hole40has the depressed portion32side aperture44and an aperture48on the internal wall54side. The aperture44of this example is provided in the apex portion33of the depressed portion32.

The internal wall54side aperture48of the connection hole40is formed in a position higher than the front surface of the sealing portion16in the height direction perpendicular to the front surface of the base substrate10. The position of the aperture48in this example is regulated by the position of the lowermost end of the aperture48. That is, the whole of the aperture48is exposed without being covered by the sealing portion16.

The sealing portion16may be formed to a position higher than the apex portion33of the depressed portion32. In this case, it is preferable that the depressed portion32side aperture44of the connection hole40is provided in the apex portion33. The connection hole40of this example has a first region50extending in the height direction from the depressed portion32side aperture44, and a second region52connecting an end portion of the first region50and the internal wall54side aperture48. The first region50may extend in the height direction perpendicular to the front surface of the base substrate10. The second region52may extend parallel to the front surface of the base substrate10.

According to this kind of configuration too, detachment of the bonding portion34can be prevented. Also, as the internal wall54side of the wall portion30is reinforced by the sealing portion16, the strength of the wall portion30can be maintained even when the connection hole40is provided on the internal wall54side. In the same way as the connection hole40shown inFIG. 5B, the second region52may extend in a direction toward the front surface side of the base substrate10in at least one region from the end portion of the first region50toward the internal wall54side aperture48.

Also, the depressed portion32may be provided toward the external wall56between the internal wall54and the external wall56of the wall portion30. In this case, the thickness of the wall on the side on which the connection hole40is provided can be increased. Also, the depressed portion32may be provided toward the internal wall54. In this case, the connection hole40can be shortened.

FIG. 7shows a sectional view of the wall portion30according to a fourth example. The wall portion30of this example is such that the form of the connection hole40differs from that of the wall portion30shown inFIGS. 4A through 4D. Other than the form of the connection hole40, the configuration may be the same as that of the wall portion30shown inFIGS. 4A through 4D.

The connection hole40of this example connects the depressed portion32and the internal wall54of the wall portion30. However, the position of the internal wall54side aperture of the connection hole40in this example is lower than the front surface of the sealing portion16. The position of the uppermost end on the internal wall54side of the connection hole40may be lower than the front surface of the sealing portion16. Also, the apex portion33of the depressed portion32is also provided in a position lower than the front surface of the sealing portion16. Also, it is preferable that the bonding portion34and resin case20remain on the lower side of the connection hole40. Therefore, a decrease in bonding strength can be prevented.

In this example, the sealing portion16is formed in the interiors of the depressed portion32and the connection hole40too. When the material of the sealing portion16is injected into the region14, the material of the sealing portion16is simultaneously injected into the depressed portion32and the connection hole40too. According to this kind of configuration, the gaseous body can be removed from inside the depressed portion32.

Also, when the material of the sealing portion16is heated after being injected into the interior of the depressed portion32, the possibility of the material expanding and exerting stress on the bonding portion34is conceivable. However, by increasing the sectional area of the connection hole40, a path along which the material of the sealing portion16expanded when heating returns to the region14can be secured. Therefore, detachment of the bonding portion34can be prevented.

The connection hole40may extend parallel to the front surface of the base substrate10between the depressed portion32side aperture and the internal wall54side aperture. In order that the material of the sealing portion16can be sufficiently injected into the depressed portion32, it is preferable that a height h3of the apertures in the connection hole40is greater than one-half of the height of the apex portion33of the depressed portion32.

The height h3of the connection hole40may be 90% or more of the height of the apex portion33. Also, the height position of the upper end of the connection hole40may be the same as the height position of the apex portion33of the depressed portion32. Therefore, the gaseous body remaining in the depressed portion32when the material of the sealing portion16is injected into the depressed portion32can be reduced. The height position of the upper end of the connection hole40may be higher than the apex portion33of the depressed portion32within a range lower than the front surface of the sealing portion16.

The length in the depth direction of the connection hole40shown inFIG. 7may be less than the length in the depth direction of the depressed portion32. The depth direction refers to a direction perpendicular to the height direction in a plane parallel to the internal wall54. The length in the depth direction of the connection hole40may be the same as the length in the depth direction of the depressed portion32. In this example, the interior of the connection hole40is also sealed with the sealing portion16, because of which the strength of the resin case20can be maintained even when the length in the depth direction of the connection hole40is increased.

FIG. 8is a diagram showing a modification example of the wall portion30applied to each example.FIG. 8shows one portion of the bottom surface of the wall portion30. A multiple of depressed portions32are arrayed linearly in the bottom surface of the wall portion30. The wall portion30of this example is such that a linking portion60linking neighboring depressed portions32is formed. The linking portion60is provided in the separating wall35that separates neighboring depressed portions32. Also, any connection hole40according to the first to fourth examples is formed in any one depressed portion32of a group of depressed portions32linked by the linking portion60.

FIG. 9Ais a diagram showing an example of the linking portion60.FIG. 9Ashows a B-B section ofFIG. 8. The linking portion60of this example is formed penetrating the separating wall35. The linking portion60may be provided toward the apex portion of the depressed portion32, in the same way as the connection hole40shown inFIG. 5A. Also, the diameter in the height direction of the linking portion60is one-half or less of the height of the depressed portion32. The diameter of the linking portion60may be one-quarter or more of the height of the depressed portion32.

In this example, the connection hole40is provided in the central depressed portion32of the multiple of depressed portions32disposed linearly and linked by the linking portion60. As heretofore described, the connection hole40may be any connection hole40of the first to fourth examples. According to this kind of configuration, the number of connection holes40can be reduced, whereby the strength of the resin case20can be secured.

Also, in another example, the connection hole40may be provided in the largest depressed portion32of a multiple of depressed portions32of differing sizes. Also, the connection hole40may be provided in every second one of linearly disposed depressed portions32. In this case, the size of the depressed portion32in which the connection hole40is provided may be greater than that of the depressed portion32in which the connection hole40is not provided. Herein, the size of the depressed portion32refers to the volume of the internal space of the depressed portion32. Also, the linking portion60may be provided toward the internal wall54from the center of a side surface of the depressed portion32. Therefore, the strength of an outer edge portion of the resin case20can be maintained.

FIG. 9Bis a diagram showing a modification example of the wall portion30applied to each example. The wall portion30of this example is such that the form of the linking portion60differs from that of the wall portion30shown inFIG. 9A. Other than the form of the linking portion60, the structure may be the same as that of the wall portion30shown inFIG. 9A.

The linking portion60of this example is formed by cutting away a bottom portion of the wall portion30. The size of the cutaway is the same as that of the linking portion60of through hole form shown inFIG. 9A. For example, a height h4of the cutaway is one-half or less of the height of the depressed portion32. Also, the height h4of the cutaway may be one-quarter or more of the height of the depressed portion32. According to this kind of structure too, a multiple of depressed portions32are linked, whereby the number of connection holes40can be reduced.

According to each example, detachment of the bonding portion34due to expansion of the gaseous body in the depressed portion32can be prevented. Also, as the possibility of bonding portion34detachment is low even when the depressed portion32is provided, the range over which the depressed portion32is applicable increases. Therefore, the depressed portion32is applicable to resin cases of various aspects, and the occurrence of voids in the resin case can be reduced. Consequently, a resin case and a semiconductor module of high quality can be provided.

The sectional form of the connection hole40may be circular, may be rectangular, or may be of another form. Also, the sectional form of the linking portion60may be circular, may be rectangular, or may be of another form. When the sections of the connection hole40and the linking portion60are not circular, the diameters thereof may refer to the greatest width of the sectional form.

Heretofore, the disclosure has been described using an embodiment, but the technical scope of the disclosure is not limited to the scope described in the embodiment. It will be clear to those skilled in the art that a large variety of changes or improvements can be added to the embodiment without departing from the principles and spirit of the disclosure. It will be clear from the description in the claims that an aspect to which this kind of change or improvement has been added may also be included in the technical scope of the disclosure.

It should be noted that unless particularly stated as being “before”, “preceding”, or the like, or unless the output of a previous process is used in a subsequent process, the execution of each process such as an operation, a procedure, a step, or a stage in a device, a system, a program, or a method shown in the claims, a specification, or drawings may be realized in an arbitrary order. With regard to an operation flow in the claims, a specification, or drawings, “firstly,”, “next”, or the like being used in a description for the sake of convenience does not mean that it is essential that the operation flow is implemented in this order.