Semiconductor device and method of manufacturing the same

A semiconductor device includes a semiconductor element 1, a thermal conductor 91 located opposite a major surface of the semiconductor element 1, and a mold resin member 6 molding the semiconductor element 1 and at least a part of the thermal conductor 91, wherein at least a part of a top surface of the thermal conductor 91 has an exposed portion exposed from the mold resin member 6, the exposed portion of the thermal conductor 91 has an opening 11, and a periphery of the opening 11 forms a projecting portion 91b projecting toward an opposite side of the semiconductor element 1.

FIELD OF THE INVENTION

The present invention relates to a semiconductor device in which a semiconductor element generating a large quality of heat is suitably mounted, and a method of manufacturing the semiconductor device.

BACKGROUND OF THE INVENTION

Owing to the multiple functions and reduced size and thickness of recent electronic apparatuses, the size and thickness of semiconductor devices have been increasingly reduced, and the number of terminals on the semiconductor devices tends to increase. One known type of semiconductor device appropriate for this situation is what is called a BGA (Ball Grid Array) package from which laterally projecting external leads as used in a conventional QFP (Quad Flat Package) are omitted but which has solder balls arranged on a bottom surface of the semiconductor device in a matrix as external electrodes for electric connections, or an LGA (Land Grid Array) package having external electrodes arranged in a matrix, or a QFN (Quad Flat Non-lead) package having external electrodes arranged on the bottom surface of the semiconductor device peripherally to one another.

If a semiconductor element generating a large quantity of heat is mounted in such a resin molding (BGA, LGA, QFN, or the like) semiconductor device, the semiconductor device needs to be designed with the radiation property thereof taken into account. Japanese Patent Laid-Open No. 8-139223 discloses a semiconductor device having a structure shown below.

Now, the conventional semiconductor device disclosed in Japanese Patent Laid-Open No. 8-139223 will be described with reference to relevant drawings.

FIG. 12is a sectional view of the conventional semiconductor device.FIG. 13is a perspective view of a thermal conductor in the semiconductor device inFIG. 12.

As shown inFIGS. 12 and 13, the conventional semiconductor device100is made up of an insulating resin and composed of a substrate3having wiring patterns2formed on opposite surfaces thereof and electrically connected together via via holes7, a semiconductor element1mounted on a major surface (semiconductor element mounting surface) of the substrate3via an adhesive4, thin metal wires5electrically connecting the semiconductor element1to the wiring patterns2on the substrate3, ball electrodes8arranged in a matrix on a surface of the substrate3which is opposite the semiconductor element1mounting surface, the ball electrodes8being electrically connected to the wiring patterns2on the substrate3, and a thermal conductor9which covers the semiconductor element1mounting surface side of the substrate3and the semiconductor element1, all or a part of a top surface of the thermal conductor9being exposed from a mold resin member6to the exterior. The thermal conductor9may be placed in abutment with the substrate3and secured thereto with an adhesive (not shown) or the like or may be disposed in abutment with the substrate3without being secured thereto.

The thermal conductor9is made up of a material with a high thermal conductance such as Cu, Cu alloy, Al, Al alloy, or Fe—Ni alloy The thermal conductor9has a plurality of openings10formed in an inclined portion9alocated close to an outer periphery thereof.

In the configuration of the semiconductor device100, heat generated by the semiconductor element1is dissipated through the via holes7and the ball electrodes8and also from the major surface (the top surface inFIG. 12) of the semiconductor element1via the thermal conductor9. The semiconductor device100thus exhibits an excellent radiation property.

Furthermore, by providing, for example, a heat sink (not shown), on the top surface of the portion of the thermal conductor9exposed from the molding resin member6, it is possible to further enhance the effect of heat radiation from the major surface of the semiconductor element1.

Moreover, since the plurality of openings10are formed in the inclined portion9aof the thermal conductor9, resin can be easily injected into the gap between the thermal conductor9and the semiconductor element1in the case of resin molding. A resin injecting capability is thus improved.

Now, description will be given of a conventional method of manufacturing a semiconductor device.

As shown inFIG. 14A, the substrate3with the wiring patterns2formed on the both surfaces is provided. As shown inFIG. 14B, the semiconductor element1is fixed and mounted on a top surface of the substrate3at bonding positions with an adhesive4.

Then, as shown inFIG. 14C, electrode pads (not shown) on the semiconductor element1mounted on the substrate3are electrically connected, by the thin metal wires5, to the wiring patterns2, provided on the top surface of the substrate3.

Then, as shown inFIG. 14D, the thermal conductor9is brought into abutment with the substrate3so as to cover the semiconductor element1. The thermal conductor9and the substrate3may be secured to each other at the abutting portion with the adhesive (not shown) or the like or only brought into abutment with each other without being secured to each other. Here, the thermal conductor9is obtained by subjecting a substantially rectangular plate to drawing or the like and providing a prismatic portion in the center of the plate such that the top of the prismatic portion is exposed from the mold resin member6and shaped like a cap covering the whole semiconductor element1as shown inFIGS. 12 and 13. The openings10are formed in the inclined portion9aclose to the outer periphery of the thermal conductor9.

Then, as shown inFIG. 14E, the semiconductor element1is mounted on and electrically connected to the substrate3via the thin metal wires5. The substrate3against which the thermal conductor9abuts is set on a lower die21A of a molding die21and molded by an upper die21B of the molding die21. At this time, a bottom surface of the upper die21B of the molding die21contacts the top surface of the thermal conductor9. In this condition, the mold resin member6is injected through an injection gate21in an injection direction22s; the injection gate21is formed in the upper die21B of the molding die21in a horizontal direction. As a result, the gap on the top surface of the substrate3is covered with the mold resin member6, whereas the top surface of the thermal conductor9is exposed from the mold resin member6to the exterior. Then, after the molding resin6is cured, the upper die21B and lower die21A of the molding die21are opened.

Then, as shown inFIG. 14F, the substrate3with the top surface thereof molded by the mold resin member6is cut into semiconductor chips using a rotating blade (not shown).

Finally, the solder balls are attached to the external pad electrodes on a bottom surface of the substrate3to form the ball electrodes8, which constitute external terminals. The semiconductor device100as shown inFIG. 12can thus be manufactured.

The conventional semiconductor device100ensures the radiation property because the top surface of the thermal conductor9is exposed from the mold resin member6. However, in the process of resin molding, owing to the use of a scheme (hereinafter referred to as a side gate scheme) according to which the resin is injected through the injection gate21s, formed in a side surface of the semiconductor device100, the thin metal wires S may be deformed as shown inFIG. 15C.

FIG. 15Ais a sectional view of the side gate scheme showing a state immediately before resin molding; the sectional view is taken along an alternate long and short dash line A-A shown inFIGS. 15B and 15C.FIG. 15Bis a plan view showing the shape of the thin metal wires5observed before resin injection.FIG. 15Cis a plan view showing the shape of the thin metal wires5and the flow pattern of the resin observed after the resin injection.

As shown inFIG. 15C, the resin injected through the injection gate21sin the injection direction22sis injected so as to create ripples around the injection gate21s. Here, dotted lines6aeach show a position reached by the resin at the same time.

The amount by which the thin metal wire5is deformed is proportional to the “viscosity of the resin”, the “flow speed of the resin”, the “angle of leading end of the resin flow to the thin metal wire”, and the like. As shown inFIG. 15B, the thin metal wires5extend radially from the center of the major surface of the semiconductor element1. Thus, as shown inFIG. 15C, after the resin injection is completed, the thin metal wires5located close to the injection gate21sor at a very small angle to the leading end of the flow located opposite the injection gate are not substantially deformed. However, the other thin metal wires5are deformed according to “the flow speed of the resin”, the “angle of leading end of the resin flow to the thin metal wire”, and the like.

Therefore, for the semiconductor device with the thin metal wires5densely arranged as a result of the reduced size of the device and the increased number of terminals, the resin molding based on the conventional side gate scheme may disadvantageously cause the adjacent thin metal wires5with a short distance therebetween to be deformed and short-circuited.

To prevent the planar deformation of the thin metal wires5, a scheme (hereinafter referred to as a top gate scheme) may be adopted according to which the resin is injected through an injection gate21tformed so as to open in the top surface of the semiconductor device, as shown inFIG. 16A to 16C.

FIG. 16Ais a sectional view of the top gate scheme; the sectional view is taken along alternate long and short dash line B-B shown inFIGS. 16B and 16C.FIG. 16Bis a plan view showing the shape of the thin metal wires5observed before the resin injection.FIG. 16Cis a plan view showing the shape of the thin metal wires5and the injection pattern of the resin observed after the resin injection.

As shown inFIG. 16C, the resin injected through the injection gate21tin an injection direction22tis injected so as to create ripples around the injection gate21t. Here, the dotted lines6aeach show the position reached by the resin at the same time.

When the injection gate21tis located above the center of the semiconductor element1, all the thin metal wires5extending radially from the center of the semiconductor element1are located at a very small angle from the leading end of the flow. This prevents the thin metal wires5from being deformed, enabling high-quality semiconductor devices to be manufactured.

However, in the conventional semiconductor device100, the thermal conductor9covers the entire top surface of the semiconductor element1and is exposed from the mold resin member6to the exterior This makes it difficult to locate the injection gate of the resin above the semiconductor element1, preventing the adoption of the top gate scheme.

Furthermore, in the conventional semiconductor device100, since the thermal conductor9is located to cover the entire surface of the semiconductor element1, the thermal conductor9may obstruct the resin molding in spite of the presence of the openings10. This may disadvantageously prevent the resin from being completely filled into the mold.

DISCLOSURE OF THE INVENTION

The present invention is made in view of the above-described circumstances. An object of the present invention is to provide a semiconductor device with a stable quality which can be manufactured while preventing short-circuiting of thin metal wires and incomplete filling of resin during a manufacturing process and which exhibits an excellent radiation property and is free from thin burrs, as well as a method of manufacturing the semiconductor device.

To accomplish the object, the present invention provides a semiconductor device including a semiconductor element, a thermal conductor located opposite a major surface of the semiconductor element, and a mold resin member molding the semiconductor element and at least a part of the thermal conductor, wherein at least a part of a top surface of the thermal conductor has an exposed position exposed from the mold resin member, the exposed portion of the thermal conductor has an opening, and a periphery of the opening forms a projecting portion projecting toward an opposite side of the semiconductor element.

Furthermore, the semiconductor device further includes a substrate having a plurality of electrode terminals on a bottom surface, and the thermal conductor is located opposite the major surface of the semiconductor element fixed to a top surface of the substrate.

Furthermore, the semiconductor device further includes a die pad and a plurality of leads arranged around a periphery of the die pad and each having a bottom surface forming an external terminal and a top surface forming an internal terminal, and the thermal conductor is located opposite the major surface of the semiconductor element fixed on the die pad.

Furthermore, the projecting portion of the thermal conductor is formed integrally with the other portions of the thermal conductor.

Furthermore, a part of the projecting portion of the thermal conductor is flush with a plane substantially parallel to the other exposed portion of the thermal conductor.

Furthermore, the thermal conductor is supported by a support portion fixed on the substrate.

Furthermore, the thermal conductor is supported by a support portion fixed on a hanging lead connected to the die pad.

Furthermore, the support portion is formed by bending a part of the thermal conductor.

Furthermore, the support portion is formed by bending a part of the thermal conductor.

Furthermore, a part of the thermal conductor which is buried in the mold resin member has a roughened surface.

Furthermore, the semiconductor device further includes a plurality of thin metal wires electrically connecting the substrate and the semiconductor element together.

Furthermore, the semiconductor device further includes a plurality of thin metal wires electrically connecting the lead and the semiconductor element together.

Furthermore, the thermal conductor is connected to a ground terminal.

The present invention also provides a method of manufacturing a semiconductor device, the method including the steps of: providing a thermal conductor having an opening and a projecting portion provided around a periphery of the opening and projecting upward from a top surface of the thermal conductor, mounting the thermal conductor so that a surface of the thermal conductor which is opposite a surface thereof from which the projecting portion projects is located opposite a major surface of a semiconductor element, installing a molding die so that the projecting portion abuts against an inner wall of the molding die, and injecting resin into the molding die through an injection port formed in the molding die and through the opening to mold the semiconductor element and the thermal conductor so as to expose the projecting portion.

Furthermore, the opening in the thermal conductor is formed so as to have a diameter larger than a diameter of the injection port in the molding die, and during resin injection, a circumference of the projecting portion formed around the periphery of the opening in the thermal conductor entirely contacts an inner wall portion of the molding die which is located outside a periphery of the injection port.

Furthermore, in the step of manufacturing the thermal conductor, a cylindrical mold having a tip portion smaller than the opening in the thermal conductor and a root portion larger than the opening is inserted into the opening in the thermal conductor to bend the periphery of the opening in the thermal conductor to form the projecting portion.

Furthermore, in the step of manufacturing the thermal conductor, the projecting portion is formed around the periphery of the opening in the thermal conductor by using a first die to support the periphery of the opening in the thermal conductor, using a second die to support a part of the thermal conductor which is located outside the periphery of the opening, and moving the second die along a thickness direction of the thermal conductor relative to the first die.

Furthermore, in the step of manufacturing the thermal conductor, the projecting portion is formed, and the opening is then formed in a center of the projecting portion.

Furthermore, in the step of manufacturing the thermal conductor, the projecting portion is formed by pressing using a mold projecting the periphery of the opening in the thermal conductor.

Furthermore, in the step of manufacturing the thermal conductor, the projecting portion is formed by pressing using the mold projecting the center of the thermal conductor, and the opening is then formed in the center of the projecting portion.

Description will be given of effects of the semiconductor device and the method of manufacturing the semiconductor device according to the present invention. The semiconductor device, on which the semiconductor element generating a large quantity of heat is mounted, has the thermal conductor exposed to the exterior. This enhances the radiation property of the semiconductor device. Furthermore, the opening is formed in the thermal conductor exposed from the mold resin member to the exterior. This enables resin injection to be stably achieved so as to enable resin molding according to the top gate scheme without suffering short-circuiting of the thin metal wires in the semiconductor device and incomplete filling of the resin. The quality of the semiconductor device can thus be stabilized.

Moreover, the projecting portion is provided around the periphery of the opening. Thus, when the molding die is clamped for resin molding, the projecting portion abuts against the inner wall portion of the molding die under an appropriate contact pressure, and during the resin molding, the molding resin advances between the periphery of the opening in the thermal conductor and the inner wall surface of the molding die. This makes it possible to reliably prevent possible thin burrs to enable the resin injection to be stably achieved. The semiconductor device with a stable quality can thus be obtained.

Furthermore, the support portion is provided only in the part of the thermal conductor. This improves the fluidity of the resin, making it possible to prevent the possible incomplete filling of the resin.

DESCRIPTION OF THE EMBODIMENTS

With reference to the drawings, description will be given of semiconductor devices101,102, and103according to embodiments of the present invention. For easy understanding, in the description below, a surface of a substrate on which a semiconductor element is mounted corresponds to a top surface. Components of the semiconductor devices which have substantially the same functions as the conventional semiconductor device100are denoted by the same reference numerals.

First Embodiment

FIG. 1shows a sectional view of the semiconductor device101according to a first embodiment of the present invention.

As shown inFIG. 1, the semiconductor device101according to the present embodiment comprises a substrate3made up of an insulating resin and having wiring patterns2formed on both surfaces thereof and electrically connected together via holes7, a semiconductor element1having a plurality of electrodes (not shown) on each of a bottom surface and a top surface thereof and mounted on a top surface of the substrate3via an adhesive4, the top surface of the substrate corresponding to a major surface (this is also hereinafter referred to a semiconductor element mounting surface), thin metal wires5electrically connecting the semiconductor element1and the wiring patterns2on the substrate3together, ball electrodes8arranged in a matrix on a bottom surface of the substrate3which is opposite the semiconductor element mounting surface, the ball electrodes8being electrically connected to the wiring patterns2on the substrate3, a thermal conductor91located over the semiconductor element mounting surface of the substrate3and opposite the major surface (the circuit surface or top surface of the semiconductor element1) of the semiconductor element1and appearing to have a substantially trapezoidal cross section in a side view, and a mold resin member6that molds a part of each of the semiconductor element mounting surface of the substrate3, the semiconductor element1, and the thermal conductor91.

In particular, in the semiconductor device101according to the present embodiment, as shown inFIGS. 1 and 2, a surface of the thermal conductor91which is opposite a surface thereof located opposite the major surface of the semiconductor element1, that is, a top surface of the thermal conductor91, constitutes an exposed portion91fexposed from the mold resin member6to the exterior. An opening11is formed in a part of the exposed portion91fof the thermal conductor91, which portion is exposed to the exterior, so as to penetrate the thermal conductor91in a board thickness direction. Moreover, a projecting portion91bis provided around the periphery of the opening11so as to project toward the opposite side of an area in which the semiconductor element1is disposed, that is, from the exposed portion91ftoward the opposite side of the surface of the thermal conductor which is opposite the major surface of the semiconductor element1(in a direction in which the projecting portion91bleaves the semiconductor element1(the direction in which the exposed portion91fis more significantly exposed; upward inFIG. 1) and which is opposite to a direction in which the projecting portion91bapproaches the semiconductor element1).

As shown inFIGS. 1 and 2, the opening11is formed in the thermal conductor91so as to lie vertically above the center of the major surface of the semiconductor element1, which is substantially parallel to the top surface of the thermal conductor91(that is, in a plan view, the opening11in the thermal conductor91appears to overlap the center of the major surface of the semiconductor element1). The projecting portion91b, provided around the periphery of the opening in the thermal conductor91is shaped substantially like a truncated cone. However, the present invention is not limited to this aspect. For example, the projecting portion91bmay be shaped substantially like a truncated pyramid or may have another shape. The four corners of the thermal conductor91are bent to form support portions91aprojecting downward from a bottom surface of the thermal conductor91and each having a bottom surface abutting against the substrate3(if the thermal conductor91appears to be substantially triangular in a plan view, the three corners may be bent to form the support portions91a).

Now, a method of manufacturing the semiconductor device101will be described with reference toFIGS. 3A to 3F. InFIG. 3E, reference numeral211denotes a molding die. Reference numeral21tdenotes an injection gate as an injection port. Reference numeral22tdenotes a direction in which a molding resin is injected.

In the method of manufacturing the semiconductor device101according to the present embodiment, first, the substrate3with the wiring patterns2formed on both surfaces thereof is provided as shown inFIG. 3A. Then, as shown inFIG. 3B, the semiconductor element1is fixed and mounted on the top surface of the substrate3with the adhesive4at bonding positions. Although not shown, a plurality of the semiconductor elements1are provided in the vertical and horizontal directions of a plan view.

Then, as shown inFIG. 3C, electrode pads (not shown) on the semiconductor element1mounted on the substrate3are electrically connected, by the thin metal wires5, to the wiring patterns2, provided on the top surface of the substrate3.

The steps described above are the same as steps of the conventional method of manufacturing the semiconductor device100.

Then, as shown inFIG. 3D, the thermal conductor91located opposite the semiconductor element1is brought into abutment with the substrate3. The thermal conductor91and the substrate3may be secured to each other at the abutting portion with the adhesive (not shown) or the like or only brought into abutment with each other without being secured to each other.

Now, a method of manufacturing the thermal conductor91will be described with reference toFIGS. 4A to 4E.

As shown inFIG. 4A, the thermal conductor91is produced by etching or pressing a metal plate made up of a material with a high thermal conductance such as Cu, Cu alloy, Al, Al alloy, or Fe—Ni alloy, into a desired integral shape.

The above-described processing method is used to form the opening11in the center of the thermal conductor91so that the opening11penetrates the thermal conductor91in the board thickness direction as shown inFIG. 4B.

This structure allows the injection gate21tto be formed vertically above the center of the major surface of the semiconductor element1. The purpose of the structure is to enable resin injection based on the top gate scheme in order to prevent the thin metal wires5from being deformed by the flow of the resin during a subsequent molding step. Furthermore, the inner diameter of the opening11is formed to be larger than the outer diameter of the injection gate21tto prevent thin burrs from being created around the periphery of the opening11during the molding step. Moreover, the surface of a part of the thermal conductor91which is buried in the mold resin member6is subjected to roughening such as dimpling so as to form recesses and protrusions. This improves the adhesion between the thermal conductor91and the mold resin member6.

Then, as shown inFIG. 4C, the corners of the thermal conductor91are bent to form the support portions91aprojecting downward from the bottom surface of the thermal conductor91. A bottom surface of each of the support portions91ais brought into abutment with the substrate3.

The support portions91aof the thermal conductor91are present only in the corners of the thermal conductor91in order to allow the resin to flow smoothly during the subsequent molding step. That is, the thermal conductor9in the conventional semiconductor device100has an inclined portion close to the outer periphery thereof, whereas the thermal conductor91in the semiconductor device101according to the present embodiment does not have most of the inclined portion close to the outer periphery thereof. The thermal conductor91has no obstacle preventing resin injection, allowing the resin to flow smoothly in the semiconductor device101according to the present embodiment.

The thermal conductor91is located with the height of the support portions91aadjusted so that the height between the uppermost surface of the thermal conductor91and the lowermost surface of the substrate3is larger than the depth of a cavity in the molding die211, used during the subsequent molding step. This allows the uppermost surface of the thermal conductor91to constitute the exposed portion91fexposed from the mold resin member6to the exterior, to improve the radiation property.

In this case, when the thermal conductor91contacts an upper die211B during the subsequent molding step, if the interface between the thermal conductor91and the upper die211B remains flat, the effect of the temperature or an insufficient pressure (contact pressure) on the molding die211may create a small gap at the periphery of the opening11to cause the mold resin member6to leak. Thus, to prevent this, the projecting portion91bis formed by using a processing mold12to fix outer portions of the periphery of the opening11so as to sandwich the outer potions between an upper die and a lower die, while inserting and thrusting a thrusting processing mold13into the opening11in the thermal conductor91toward the opposite side of the mounting surface, located opposite the semiconductor element1as shown inFIG. 4D; the thrusting processing mold13has a gently inclined surface as well as a tip portion smaller than the (diameter of) opening11and a root portion larger than the (diameter of) opening11. The thermal conductor91as shown inFIG. 4Eis thus formed.

Description will be given again of the method of manufacturing the semiconductor device101according to the present embodiment. As shown inFIG. 3E, the semiconductor element1is mounted on and electrically connected to the substrate3by the thin metal wires5. The thermal conductor91abuts against the substrate3. The substrate3is set in a lower die211A of the molding die211and sealed by the upper die211B of the molding die211. At this time, a bottom surface of the upper die211B of the molding die211is in contact with the top surface of the thermal conductor91. In particular, the projecting portion91bof the thermal conductor91, formed as shown inFIG. 3E, comes into contact with an inner wall surface of the upper die211B before the outer peripheral portion of the thermal conductor91.

In this condition, the mold resin member6is injected through the injection gate21tin the injection direction22t; the injection gate21tis formed in the upper die211B of the molding die211in the vertical direction. As a result, a space portion over the top surface of the substrate3is filled with the mold resin member6, with the top surface (exposed portion91f) of the thermal conductor91exposed from the mold resin member6to the exterior. After the mold resin member6is cured, the upper die211B and lower die211A of the molding die211are opened to form the assembly of the semiconductor device molded by the mold resin member6.

Then, as shown inFIG. 3F, the substrate3with the top surface (semiconductor element mounting surface) molded by the mold resin member6is cut into semiconductor chips using a rotating blade (not shown).

Finally, solder balls are attached to external pad electrodes (electrode terminals) on a bottom surface of each of the semiconductor chips, into which the substrate3has been cut, to form the ball electrodes8, which constitute external terminals. The semiconductor device101as shown inFIG. 1can thus be manufactured.

The thermal conductor91need not be shaped like a quadrilateral (a rectangle in a plan view) as in the case of the present embodiment but may be round or polygonal. The shape of the opening11also need not be round but may be polygonal provided that the opening11is larger than the outer diameter of the injection gate. Furthermore, the support portions91aof the thermal conductor91need not necessarily abut against the substrate3but may abut against the semiconductor element1provided that the support portions91aallows the top surface of the thermal conductor91to be exposed. Moreover, the support portions91aneed not be produced by bending the corners of the thermal conductor91. Other members may be bonded to the corners of the thermal conductor91as support portions provided that the support portions allow the top surface of the thermal conductor91to be exposed to form the exposed portion91f.

Description will be given of effects of the semiconductor device101and the method of manufacturing the semiconductor device101according to the present embodiment.

As described above, in addition to the substrate3, thin metal wires5, semiconductor element1, and mold resin member6, which are provided in the conventional semiconductor device, the semiconductor device101according to the present embodiment comprises the thermal conductor91made up of the thermally conductive material and having the exposed portion91fcorresponding to the top surface thereof and exposed from the mold resin member6to the exterior, and the opening11formed in the exposed portion91fand penetrating the thermal conductor91in the board thickness direction. This enables the resin to be injected through the opening11while maintaining the conventional function of emitting heat generated in the semiconductor device101to the exterior of the semiconductor device101via the exposed portion91fof the thermal conductor91. The opening11formed in the exposed portion91fof the thermal conductor91improves the adhesion between the thermal conductor91and the mold resin member6.

The semiconductor device101allows the top gate scheme according to which the injection gate21tis formed above the opening11in the thermal conductor91, to be adopted for the molding step of the manufacturing process. This reduces the amount by which the thin metal wires5are deformed by the flow of the resin. That is, the thin metal wires5can be prevented from being short-circuited. The method of manufacturing the semiconductor device101according to the present invention enables the semiconductor device101to be manufactured while preventing the electric connection function from being degraded or disabled. The semiconductor device101can be manufactured at a high yield.

Furthermore, the inner diameter of the opening11in the thermal conductor91in the semiconductor device101is formed to be larger than the outer diameter of the injection gate21t, and the projecting portion91bis formed around the periphery of the opening11so as to project toward the opposite side of the semiconductor element1mounting surface. This makes it possible to prevent thin burrs from being created around the periphery of the opening11during the molding step. That is, if the inner diameter of the opening11in the thermal conductor91in the semiconductor device101is formed smaller than the outer diameter of the injection gate21t, the molding resin may advance between the periphery of the opening11in the thermal conductor91and the top surface of the upper die211B of the molding die211to create thin burrs. However, the above-described configuration makes this problem unlikely to occur. Moreover, since the projecting portion91bis formed around the periphery of the opening11in the thermal conductor91, when the upper die211B and lower die211A of the molding die211are closed and clamped, the projecting portion91bof the thermal conductor91is pressed hard against the planar bottom surface (inner wall surface) of the upper die211B. Then, the molding step is executed in this condition, reliably preventing the molding resin from advancing between the periphery of the opening11in the thermal conductor91and the top surface of the upper die211B of the molding die211. This makes it possible to reliably prevent thin burrs from being created around the periphery of the opening11during the molding step.

In the semiconductor device101the support portions91aare provided only in the corners of the bottom surface of the thermal conductor91. This prevents the thermal conductor91from obstructing the flow of the resin during the molding step. Defects such as incomplete filling of the resin can be prevented.

Moreover, in the semiconductor device101, the support portions91aof the thermal conductor91are provided only in the corners to reduce the abutting area between the thermal conductor91and the substrate3. This prevents the thermal conductor91from obstructing the wiring patterns2for signals. This makes the thermal conductor91composed of an electrically conductive material available though grounding. A high frequency property can thus be improved.

In short, with the semiconductor device101and the method of manufacturing the semiconductor device101according to the present embodiment, the semiconductor device101according to the present embodiment is more excellent than the conventional semiconductor device100. That is, the semiconductor device101exhibits a higher performance by, for example, reducing the deformation amount of the thin metal wires5during the molding step to prevent defects resulting from the possible short-circuiting between the thin metal wires5, allowing the resin to flow smoothly to prevent the possible incomplete filling of the resin, and achieving appropriate adhesion to the mold resin member6, offers a high manufacturing yield, and improves the high frequency property by using the grounded thermal conductor91. Moreover, the present embodiment makes it possible to reliably prevent thin burrs from being created around the periphery of the opening11, allowing the semiconductor device101with a stable quality to be manufactured.

The shape of the thermal conductor91is not limited to the one in the first embodiment.

Second Embodiment

A second embodiment as a variation of the first embodiment will be described below with reference toFIG. 5and other figures. The only difference between the semiconductor device101according to the first embodiment and a semiconductor device102according to the second embodiment, a variation of the semiconductor device101, is the shapes of a thermal conductor92and the molding die211. In the description below, components of the semiconductor device102corresponding to components of the semiconductor device101according to the first embodiment are denoted by the same reference numerals. The description of these components is omitted.

FIG. 5is a sectional view showing the semiconductor device102according to the second embodiment of the present invention.FIG. 6is a perspective view of the thermal conductor92in the semiconductor device102.

The thermal conductor92, provided in the semiconductor device102according to the second embodiment, has a projecting portion92bformed around the periphery of the opening11and projecting toward the opposite side of a surface of the thermal conductor92which is opposite the major surface of the semiconductor element1, the projecting portion92bcomprising a flat portion92cpositioned above an exposed portion92flocated around the periphery of the projecting portion92b, as shown inFIG. 5. The area of a part of the flat portion92cin which the projecting portion92bof the thermal conductor92is provided is smaller than that of the exposed portion92f, located around the periphery of the projecting portion. In the other respects, the semiconductor device102is the same as the semiconductor device101according to the first embodiment.

Similar effects can also be exerted by bringing the flat portion92cof the projecting portion92binto abutment with an upper die212B of a molding die212during the resin molding step. The width of the flat portion92cis as small as possible.

Several methods are available for forming (manufacturing) the thermal conductor92in the semiconductor device102according to the second embodiment. The methods will be sequentially described below with reference toFIGS. 7A to 10E.

FIGS. 7A to 7Eare sectional views showing a first method for manufacturing the semiconductor device102.

As shown inFIG. 7A, the thermal conductor92is produced by etching or pressing a metal plate made up of a material with a high thermal conductance such as Cu, Cu alloy, Al, Al alloy, or Fe—Ni alloy, into a desired shape.

The above-described processing method is used to form the opening11in the center of the thermal conductor92so that the opening11penetrates the thermal conductor92in the board thickness direction as shown inFIG. 7B.

This structure allows the injection gate21t(seeFIG. 3E) to be formed vertically above the center of the major surface of the semiconductor element1. The purpose of the structure is to enable resin injection based on the top gate scheme in order to prevent the thin metal wires5from being deformed by the flow of the resin during the subsequent molding step. Furthermore, the inner diameter of the opening11is formed to be larger than the outer diameter of the injection gate21tto prevent thin burrs from being created around the periphery of the opening11during the molding step. Moreover, the surface of a part of the thermal conductor92which is buried in the mold resin member6is subjected to roughening such as dimpling so as to form recesses and protrusions. This improves the adhesion between the thermal conductor92and the mold resin member6.

Then, as shown inFIG. 7C, the corners of the thermal conductor92are bent to form the support portions92aprojecting downward from the bottom surface of the thermal conductor92. A bottom surface of each of the support portions92ais brought into abutment with the substrate3.

The support portions92aof the thermal conductor92are present only in the corners of the thermal conductor92in order to allow the resin to flow smoothly during the subsequent molding step. That is, the thermal conductor9in the conventional semiconductor device100has an inclined portion close to the outer periphery thereof, whereas the thermal conductor92in the semiconductor device102according to the present embodiment does not have most of the inclined portion close to the outer periphery thereof. The thermal conductor92has no obstacle preventing resin injection, allowing the resin to flow smoothly in the semiconductor device102according to the present embodiment.

The thermal conductor92is located with the height of the support portions92aadjusted so that the height between the uppermost surface (exposed portion92f) of the thermal conductor92and the lowermost surface of the substrate3is larger than the depth of the cavity in the molding die211, used during the subsequent molding step. This allows the uppermost surface of the thermal conductor92to be exposed from the mold resin member6to the exterior to improve the radiation property.

In this case, when the thermal conductor92contacts the upper die211B during the subsequent molding step, if the interface between the thermal conductor92and the upper die211B remains flat, the effect of the temperature or an insufficient pressure (contact pressure) on the molding die211may create a small gap at the periphery of the opening11to cause the mold resin member6to leak. Thus, to prevent this, the following method is used to form the projecting portion92bprojecting toward the opposite side of the surface of the thermal conductor92which is opposite the semiconductor element1when the semiconductor device102is finally formed: as shown inFIG. 7D, a processing mold14is used to sandwich the periphery of the opening11between an upper die and a lower die, a processing mold15is used to sandwich the periphery of the projecting portion92bbetween an upper die and a lower die, the processing mold14is fixed, and the processing mold15is moved toward the area in which the semiconductor element1and the substrate3are finally disposed (downward relative to the processing mold14). The thermal conductor92as shown inFIG. 7Eis thus formed

FIGS. 8A to 8Eare sectional views showing a second method of manufacturing the thermal conductor92in the semiconductor device102according to the second embodiment of the present invention.

In the first manufacturing method, shown inFIGS. 7A to 7E, the opening11is formed before the projecting portion92bis formed. However, the second manufacturing method, shown inFIGS. 8A to 8E, is characterized in that the opening11is formed after the projecting portion92bhas been formed. In the other respects, the second manufacturing method is the same as the first manufacturing method.

FIGS. 9A to 9Eare sectional views showing a third method of manufacturing the thermal conductor92in the semiconductor device102.

The third manufacturing method which is different from the first and second manufacturing methods, shown inFIGS. 9A to 9E, is characterized in that the thermal conductor92as shown inFIG. 9Eis formed by forming the projecting portion92bby using the processing mold14to sandwich the periphery of the opening11between the upper die and the lower die, using the processing mold15to sandwich the periphery of the projecting portion92bbetween the upper die and the lower die, fixing the processing mold15, and moving the processing mold14toward the opposite side of the surface of the thermal conductor92which is opposite the semiconductor element1. In the other respects, the third manufacturing method is the same as the first manufacturing method.

FIGS. 10A to 10Eare sectional views showing a fourth method of manufacturing the thermal conductor92in the semiconductor device102.

The fourth manufacturing method, shown inFIGS. 10A to 10E, is characterized in that the opening11is formed after the projecting portion92bhas been formed. In the other respects, the fourth manufacturing method is the same as the first manufacturing method.

The semiconductor device102according to the second embodiment also allows the top gate scheme according to which the injection gate21tis formed above the opening11in the thermal conductor92, to be adopted for the molding step of the manufacturing process. This reduces the amount by which the thin metal wires5are deformed by the flow of the resin. That is, the thin metal wires5can be prevented from being short-circuited. The semiconductor device102can be manufactured at a high yield.

The projecting portion92b, projecting toward the opposite side of the semiconductor element1mounting surface, more specifically, the flat portion92cof the projecting portion92b, positioned above the periphery of the projecting portion92b, is formed around the periphery of the opening11in the thermal conductor92in the semiconductor device102. Thus, when the upper die211B and lower die211A of the molding die211are closed, the flat portion92cof the projecting portion92bof the thermal conductor92is pressed hard against the planar bottom surface of the upper die211B. Then, the molding step is executed in this condition, reliably preventing the molding resin from advancing between the periphery of the opening11in the thermal conductor92and the top surface of the upper die211B of the molding die211. This makes it possible to reliably prevent thin burrs from being created around the periphery of the opening11during the molding step.

In the semiconductor device102, the support portions92aof the thermal conductor92are also provided only in the corners. This reduces the abutting area between the thermal conductor92and the substrate3and prevents the thermal conductor92from obstructing the wiring patterns2for signals This makes the thermal conductor92composed of an electrically conductive material available though grounding. The high frequency property can thus be improved.

In short, with the semiconductor device102and the method of manufacturing the semiconductor device102according to the second embodiment, the semiconductor device102according to the present embodiment is also more excellent than the conventional semiconductor device100. That is, the semiconductor device102exhibits a higher performance by, for example, reducing the deformation amount of the thin metal wires5during the molding step to prevent defects resulting from the possible short-circuiting between the thin metal wires5, allowing the resin to flow smoothly to prevent the possible incomplete filling of the resin, and achieving appropriate adhesion to the mold resin member6, offers a high manufacturing yield, and improves the high frequency property by using the grounded thermal conductor92. Moreover, the present embodiment makes it possible to reliably prevent thin burrs from being created around the periphery of the opening11.

Third Embodiment

FIGS. 11A and 11Bshow a sectional view and a bottom view of a semiconductor device103according to a third embodiment of the present invention.FIG. 11Acorresponds to a sectional view take along an alternate long and short dash line C-C shown inFIG. 11B. In the description below, components of the semiconductor device103corresponding to components of the semiconductor device101according to the first embodiment are denoted by the same reference numerals. The description of these components is omitted.

As shown inFIGS. 11A and 11B, the semiconductor device103according to the third embodiment comprises, instead of the substrate3according to the first embodiment, a lead frame15integrally having a die pad15ccorresponding to a semiconductor element mounting area, a plurality of leads arranged around the die pad15cand each having a bottom surface constituting an external terminal15dand a top surface constituting an internal terminal15a, and hanging leads15bthat support the die pad15c.

The major surface of the semiconductor element1is secured to the die pad15cof the lead frame15with the adhesive4. The electrodes on the semiconductor element1are electrically connected to the top-surface internal terminals15aon the lead frame15by the thin metal wires5. The support portions91aof the thermal conductor91are secured to the hanging leads15b, arranged in the four corners of the semiconductor device. The mold resin member6covers the semiconductor element1, the thin metal wires5, the semiconductor element side and support portions91aof the thermal conductor91, and the top-surface internal terminals15awith the resin. In this case, the mold resin member6is provided so as to expose the top surface of the thermal conductor91, a bottom surface of the die pad15c, and the external terminals15dwhich is the lower surface of the lead to the exterior.

Furthermore, the thermal conductor91is disposed so that the surface of the thermal conductor91which is opposite the surface thereof located opposite the major surface of the semiconductor element1, that is, the top surface of the thermal conductor91is exposed to the exterior. The opening11is formed in a part of the top surface of thermal conductor91, which is exposed to the exterior, so as to penetrate the thermal conductor91in the board thickness direction. Moreover, the projecting portion91bis provided around the periphery of the opening11so as to project toward the opposite side of the area in which the semiconductor element1is disposed, that is, from the exposed portion91ftoward the opposite side of the surface of the thermal conductor91which is opposite the major surface of the semiconductor element1.

This configuration can achieve operations and effects which are similar to operations and effects of the first embodiment.

The present invention is particularly suitably applicable to a semiconductor device in which a semiconductor element generating a large quantity of heat is suitably mounted, and a method of manufacturing the semiconductor device. The present invention is effective for implementing a semiconductor device which exhibits a particularly excellent radiation property and which is requested to have a stable quality.