POWER MODULE, POWER SEMICONDUCTOR DEVICE, AND MANUFACTURING METHODS THEREFOR

The power module includes: a heat spreader having a plate shape and having heat conducting property; a semiconductor element at least thermally connected to a one-side surface of the heat spreader; a highly-heat-dissipating insulation adhesive sheet having a plate shape and having a one-side surface thermally connected to an other-side surface of the heat spreader; a metal plate having a one-side surface thermally connected to an other-side surface of the highly-heat-dissipating insulation adhesive sheet; and a sealing resin member sealing the semiconductor element, the heat spreader, the highly-heat-dissipating insulation adhesive sheet, and the metal plate in a state where an other-side surface of the metal plate is exposed, wherein the highly-heat-dissipating insulation adhesive sheet is a complex obtained by impregnating, with a resin, a porous ceramic sintered body in which ceramic particles have a gap and have been integrally sintered.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a power module, a power semiconductor device, and manufacturing methods therefor.

2. Description of the Background Art

In a power module used mainly for power conversion, a semiconductor element is joined to a heat spreader or the like having heat conducting property by means of a joining member, and the semiconductor element and the heat spreader are sealed by a resin member. In recent years, increase of the capacities and decrease of the sizes of power modules have been progressing, and power modules that have small sizes and favorable cooling efficiencies and that are highly reliable, have been required. In order to realize increase of the capacity of a power module without increasing the size of a semiconductor element, heat generated by the semiconductor element needs to be efficiently diffused to outside since high current is caused to flow in the semiconductor element. Thus, attempts have been made to decrease the thermal resistances of a heat dissipation member, an insulation member, and a joining member that are provided between a semiconductor element and a cooler such as a heatsink.

The thermal resistances of the heat dissipation member, the insulation member, and the joining member are compared as follows. The heat dissipation member and the joining member are members that serve mainly to cause current to flow, and thus, in general, the thermal resistances of these members are low. Meanwhile, the insulation member serves to insulate and separate the cooler and the semiconductor element from each other in a power module provided with the cooler, and thus the thermal resistance of the insulation member tends to become high. A member for realizing decrease of the thermal resistance of an insulation member is disclosed (see, for example, Patent Document 1).

The disclosed insulation member is configured as a board of a nitride-based ceramic resin complex in which a porous nitride-based ceramic sintered body having three-dimensionally continuous pores has been impregnated with a thermosetting resin composition in an incompletely cured state. Patent Document 1 describes, in an example, that a dielectric breakdown voltage was 10.0 kV and a thermal conductivity at 25° C. was 100 W/(m·K) owing to the disclosed configuration. These values are values applicable to an insulation member that insulates and separates a cooler and a semiconductor element from each other and that decreases the thermal resistance of the interval between the cooler and the semiconductor element.

A configuration of a semiconductor device having an insulation resin layer which is a conventional insulation member, is disclosed (see, for example, Patent Document 2). The insulation resin layer is provided between a copper plate and a heat spreader which is mounted with a semiconductor element, and a cooler is thermally connected to the copper plate. The disclosed insulation resin layer has a configuration in which an inorganic powder filler having high heat conducting property such as ceramic particles is contained in a thermosetting resin such as epoxy resin. It is described that ceramic particles of aluminum nitride, silicon nitride, boron nitride, aluminum oxide (alumina), silicon oxide (silica), magnesium oxide, zinc oxide, titanium oxide, and the like are suitable as the inorganic filler having high heat conducting property.

In the above Patent Document 1, the board of the nitride-based ceramic resin complex has an excellent dielectric breakdown voltage and an excellent thermal conductivity. However, Patent Document 1 does not disclose any specific configuration in which the board of the nitride-based ceramic resin complex is applied to a power module, but merely discloses processing the disclosed nitride-based ceramic resin complex into a heat-conducting insulation adhesive sheet and performing heating and pressure-bonding of the heat-conducting insulation adhesive sheet to an adherend such as a metal plate or a metal circuit board. It is inferred that, in order to obtain two metal circuit boards ensured to be insulated from each other, a board of a ceramic resin complex in which impregnation with a resin in a semi-cured state has been performed is interposed between the metal circuit boards, and heating and pressure-bonding are performed so as to configure the two metal circuit boards to be insulated from each other. If such a manufacturing method is employed, portions of the board of the ceramic resin complex that are in contact with the metal circuit boards are pressurized while an outer peripheral portion of the board of the ceramic resin complex that is not in contact with the metal circuit boards is kept in an unconstrained state, during the heating and pressure-bonding. The resin in a semi-cured state flows in a direction toward the unconstrained outer peripheral portion. At this time, with a focus on a pressure generated inside the ceramic resin complex, the internal pressure is maximized at the center of gravity of the ceramic resin complex, and meanwhile, at an unconstrained side surface of the ceramic resin complex, the pressure on the side surface portion is zero. Since the pressure applied to the inside of the board of the ceramic resin complex decreases in a direction toward the outer peripheral portion, a gap that is present inside the board of the ceramic resin complex, particularly, near the outer peripheral portion, cannot be filled with the resin. Consequently, a problem arises in that an electric discharge path is formed at a portion at which the gap remains, whereby the insulation reliability of the ceramic resin complex decreases.

In the above Patent Document 2, the insulation resin layer has no portion at which a gap remains after pressurization. Thus, the copper plate and the heat spreader which is mounted with the semiconductor element can be insulated from each other. However, a thermal conductivity that can be attained by the resin insulation layer having the disclosed configuration is about 16 W/(m·K) at most, and thus a problem arises in that decrease of the thermal resistance of the insulation member is not sufficient. In addition, both the thermosetting resin and the ceramic particles flow to the periphery during molding with the resin member, and thus a problem arises in that an electric discharge path is formed by the resin having flowed, whereby the insulation reliability decreases.

SUMMARY OF THE INVENTION

Considering this, an object of the present disclosure is to provide: a power module and a power semiconductor device in which decrease of insulation reliability is inhibited and increase of heat dissipation is realized; and manufacturing methods therefor.

A power module according to the present disclosure includes: a heat spreader having a plate shape and having heat conducting property; a semiconductor element at least thermally connected to a one-side surface of the heat spreader; a highly-heat-dissipating insulation adhesive sheet having a plate shape and having a one-side surface thermally connected to an other-side surface of the heat spreader; a metal plate having a one-side surface thermally connected to an other-side surface of the highly-heat-dissipating insulation adhesive sheet; and a sealing resin member sealing the semiconductor element, the heat spreader, the highly-heat-dissipating insulation adhesive sheet, and the metal plate in a state where an other-side surface of the metal plate is exposed, wherein the highly-heat-dissipating insulation adhesive sheet is a complex obtained by impregnating, with a resin, a porous ceramic sintered body in which ceramic particles have a gap and have been integrally sintered.

A manufacturing method for a power module according to the present disclosure includes: a member preparation step of preparing a heat spreader having a plate shape and having heat conducting property, a semiconductor element at least thermally connected to a one-side surface of the heat spreader, a highly-heat-dissipating insulation adhesive sheet having a plate shape and having a one-side surface thermally connected to an other-side surface of the heat spreader, and a metal plate having a one-side surface thermally connected to an other-side surface of the highly-heat-dissipating insulation adhesive sheet; and a sealing resin member injection step of injecting under pressure a sealing resin member, which is uncured, into a mold in a state where the heat spreader, the semiconductor element, the highly-heat-dissipating insulation adhesive sheet, and the metal plate are placed in the mold, wherein the metal plate has an other-side surface exposed from the sealing resin member after execution of the sealing resin member injection step, the highly-heat-dissipating insulation adhesive sheet is a complex obtained by impregnating, with a resin, a porous ceramic sintered body in which ceramic particles have a gap and have been integrally sintered, the ceramic sintered body has a gap not filled with the resin before execution of the sealing resin member injection step, and the sealing resin member injection step includes pressurizing the highly-heat-dissipating insulation adhesive sheet by injection pressure of the sealing resin member so that the gap not filled with the resin is filled with the resin.

The power module according to the present disclosure includes: a heat spreader having a plate shape; a semiconductor element at least thermally connected to a one-side surface of the heat spreader; a highly-heat-dissipating insulation adhesive sheet having a plate shape and having a one-side surface thermally connected to an other-side surface of the heat spreader; a metal plate having a one-side surface thermally connected to an other-side surface of the highly-heat-dissipating insulation adhesive sheet; and a sealing resin member sealing these members in a state where an other-side surface of the metal plate is exposed, wherein the highly-heat-dissipating insulation adhesive sheet is a complex obtained by impregnating, with a resin, a porous ceramic sintered body in which ceramic particles have a gap and have been integrally sintered. Consequently, no electric discharge path is formed in the gap in the ceramic sintered body, and thus decrease of the insulation reliability of the power module can be inhibited. Since the highly-heat-dissipating insulation adhesive sheet is a complex obtained by impregnating, with a resin, a porous ceramic sintered body in which ceramic particles have a gap and have been integrally sintered, increase of heat dissipation in the power module can be realized.

The manufacturing method for the power module according to the present disclosure includes: a member preparation step of preparing a heat spreader having a plate shape, a semiconductor element at least thermally connected to a one-side surface of the heat spreader, a highly-heat-dissipating insulation adhesive sheet having a plate shape and having a one-side surface thermally connected to an other-side surface of the heat spreader, and a metal plate having a one-side surface thermally connected to an other-side surface of the highly-heat-dissipating insulation adhesive sheet; and a sealing resin member injection step of injecting under pressure a sealing resin member, which is uncured, into a mold in a state where the heat spreader, the semiconductor element, the highly-heat-dissipating insulation adhesive sheet, and the metal plate are placed in the mold, wherein the highly-heat-dissipating insulation adhesive sheet is a complex obtained by impregnating, with a resin, a porous ceramic sintered body in which ceramic particles have a gap and have been integrally sintered, the ceramic sintered body has a gap not filled with the resin before execution of the sealing resin member injection step, and the sealing resin member injection step includes pressurizing the highly-heat-dissipating insulation adhesive sheet by injection pressure of the sealing resin member so that the gap not filled with the resin is filled with the resin. Consequently, no electric discharge path is formed in the gap. This makes it possible to significantly improve the insulation reliability of the entire highly-heat-dissipating insulation adhesive sheet including an edge of the highly-heat-dissipating insulation adhesive sheet. Thus, decrease of the insulation reliability of the power module can be inhibited.

Hereinafter, power modules, power semiconductor devices, and manufacturing methods therefor according to embodiments of the present disclosure will be described with reference to the drawings. Description will be given while the same or corresponding members and portions in the drawings will be denoted by the same reference characters.

First Embodiment

FIG.1is a perspective view schematically showing a power semiconductor device100according to a first embodiment.FIG.2is a cross-sectional view schematically showing the power semiconductor device100, taken at the cross-sectional position A-A inFIG.1.FIG.3is a cross-sectional view schematically showing another power semiconductor device100according to the first embodiment.FIG.4is a cross-sectional view schematically showing another power semiconductor device100according to the first embodiment.FIG.5illustrates a manufacturing process for the power semiconductor device100. The power semiconductor device100has a power module200mounted with semiconductor elements1such as power control semiconductor elements, and is used for a power conversion device or the like. In the cross-sectional views shown in the present embodiment, a surface in the upward direction of each member is defined as a one-side surface, and a surface in the downward direction of each member is defined as an other-side surface.

The power semiconductor device100includes the power module200and a cooler9. As shown inFIG.2, the cooler9is thermally connected via a metal joining body8to a surface of a metal plate7that is exposed from a sealing resin member5. The cooler9is formed from, for example, an aluminum alloy or a copper material which have excellent heat conducting properties. The material of the cooler9is preferably an aluminum alloy that, because of a low weight thereof, eliminates the need for consideration of the weight of the entire power semiconductor device100and that, because of an excellent corrosion resistance thereof, eliminates the need for consideration of influence of corrosion. As specific materials, ADC12 suitable for die casting, and A6063 applicable to forging and cutting work and having a high thermal conductivity, are more preferable.

The cooler9includes a plurality of heat dissipation fins9aformed in a flat plate shape on a surface of the cooler9that is on an opposite side to the metal joining body8. The heat dissipation fins9aare provided to further efficiently dissipate, to outside, heat generated from each semiconductor element1inside the power module200. The heat dissipation fins9aare provided to the cooler9by means of cutting, die casting, forging, or the like. The heat dissipation structure to be provided to the cooler9is not limited to the heat dissipation fins9a,and a flow path through which a cooling liquid such as water or antifreeze liquid is caused to pass may be formed in the cooler9.

The metal joining body8is formed from, for example, a solder. The material of the metal joining body8is not limited to a solder and may be sintered Ag or sintered Cu which are highly-heat-conducting materials, and a joining method such as ultrasonic joining or welding may be selected. The material of the metal joining body8needs to be selected in consideration of balance with a material of a joining body4(described later) used inside the power module200. For example, if each of the joining body4and the metal joining body8is formed from a solder, material selection should be performed such that: the solder of the metal joining body8has a low melting point; and the difference in melting point between the bodies is 30° C. or higher or, in consideration of mass productivity, 40° C. or higher. If the metal joining body8is formed from a solder having a higher melting point than the joining body4, a portion of the joining body4used inside the power module200might melt at the time of connection by means of the metal joining body8, whereby a malfunction might occur. If the joining body4is formed from sintered Ag or sintered Cu, the metal joining body8may be formed from a solder, or sintered Ag or sintered Cu.

By thus configuring the power semiconductor device100, heat generated from the semiconductor element1inside the power module200can be efficiently dissipated from the cooler9to outside. Further, if the heat dissipation fins9aare provided to the cooler9, heat generated from the semiconductor element1can be further efficiently dissipated from the cooler9to outside.

As shown inFIG.2, the power module200includes: a heat spreader3having a plate shape and having heat conducting property; the semiconductor element1at least thermally connected to a one-side surface of the heat spreader3; a highly-heat-dissipating insulation adhesive sheet6having a plate shape and having a one-side surface thermally connected to an other-side surface of the heat spreader3; a metal plate7having a one-side surface thermally connected to an other-side surface of the highly-heat-dissipating insulation adhesive sheet6; and the sealing resin member5sealing the semiconductor element1, the heat spreader3, the highly-heat-dissipating insulation adhesive sheet6, and the metal plate7in a state where an other-side surface of the metal plate7is exposed. Although the power module200has two semiconductor elements1aand1bin the present embodiment, the number of the semiconductor elements1included by the power module200is not limited thereto. In the present embodiment, each semiconductor element1formed in a plate shape has an electrode on each of both surfaces thereof. If the semiconductor element1has an electrode on each of both surfaces thereof, the semiconductor element1is thermally and electrically connected to the one-side surface of the heat spreader3. Meanwhile, if the semiconductor element1has an electrode only on a one-side surface thereof, the semiconductor element1is thermally connected to the one-side surface of the heat spreader3.

The power module200further includes: a first lead frame2aelectrically connected to the one-side surface of the semiconductor element1; a second lead frame2belectrically connected to the one-side surface of the heat spreader3; and third lead frames2c(not shown inFIG.2) electrically connected to a control pad provided on the one-side surface of the semiconductor element1. The sealing resin member5seals the first lead frame2a,the second lead frame2b,and the third lead frames2csuch that an end portion of the first lead frame2athat extends in a direction away from a portion of the first lead frame2athat is connected to the semiconductor element1, an end portion of the second lead frame2bthat extends in a direction away from a portion of the second lead frame2bthat is connected to the heat spreader3, and an end portion of each third lead frame2cthat extends in a direction away from a portion of the third lead frame2cthat is connected to the semiconductor element1, are exposed.

The semiconductor elements1aand1bare connected to the one-side surface of the heat spreader3by means of respective joining bodies4a.Principal current is conducted in the first lead frame2aand the second lead frame2b.The first lead frame2ais connected to the one-side surfaces of the semiconductor elements1aand1bby means of respective joining bodies4b.The second lead frame2bis connected to the one-side surface of the heat spreader3by means of a joining body4c.Control current is conducted in the third lead frame2c.The third lead frame2cis connected to the control pad by means of a joining body4d.The joining body4dand the third lead frame2care shown inFIG.7explaining a manufacturing method described later.

By thus configuring the power module200, heat generated when the semiconductor elements1aand1bare operated is transmitted in the order of the joining bodies4a,the heat spreader3, the highly-heat-dissipating insulation adhesive sheet6, and the metal plate7. Heat transmitted to the metal plate7is transmitted via the metal joining body8to the cooler9and dissipated from the cooler9to outside.

The power module200is desirably configured such that: the highly-heat-dissipating insulation adhesive sheet6and the heat spreader3are in contact with each other, and the highly-heat-dissipating insulation adhesive sheet6and the metal plate7are in contact with each other; and only a component of the highly-heat-dissipating insulation adhesive sheet6is interposed between the highly-heat-dissipating insulation adhesive sheet6and the heat spreader3, and between the highly-heat-dissipating insulation adhesive sheet6and the metal plate7. When the constituents inside the power module200are sealed by the sealing resin member5, the sealing resin member5may be interposed between the highly-heat-dissipating insulation adhesive sheet6and the heat spreader3, and between the highly-heat-dissipating insulation adhesive sheet6and the metal plate7. If the sealing resin member5is interposed therebetween, a portion at which the sealing resin member5is interposed is thicker, by the thickness of the interposed sealing resin member5, than the other portion at which the sealing resin member5is not interposed. Accordingly, the heat dissipation quality of the portion at which the sealing resin member5is interposed deteriorates. If the highly-heat-dissipating insulation adhesive sheet6and the heat spreader3are in contact with each other and the highly-heat-dissipating insulation adhesive sheet6and the metal plate7are in contact with each other, only the component of the highly-heat-dissipating insulation adhesive sheet6is interposed between the highly-heat-dissipating insulation adhesive sheet6and the heat spreader3, and between the highly-heat-dissipating insulation adhesive sheet6and the metal plate7. Therefore, decrease of the heat dissipation quality of the power module200can be prevented.

Adjustments of a mold retaining time, injection pressure of the sealing resin member5, and the like in a sealing resin member injection step described later enable manufacturing so as to obtain the configuration in which the highly-heat-dissipating insulation adhesive sheet6and the heat spreader3are in contact with each other and the highly-heat-dissipating insulation adhesive sheet6and the metal plate7are in contact with each other. From the viewpoint of insulation quality and heat dissipation quality, the sealing resin member5or the like which is not the component of the highly-heat-dissipating insulation adhesive sheet6may be interposed at a portion where influences on insulation quality and heat dissipation quality are small, such as a portion near the outer periphery of the highly-heat-dissipating insulation adhesive sheet6. However, a crack that occurs in a metal circuit board or the like may originate from the interposed member such as the sealing resin member5. Thus, the configuration in which the highly-heat-dissipating insulation adhesive sheet6and the heat spreader3are in contact with each other and the highly-heat-dissipating insulation adhesive sheet6and the metal plate7are in contact with each other, is desirable.

<Constituents of Power Module200>

Each of the constituents of the power module200will be described. Examples of the materials of the constituents are presented, and the materials are not limited to the described materials. Each of the semiconductor elements1aand1bis formed from, for example, Si. Each of the semiconductor elements1aand1bmay be formed from a semiconductor material having a wide bandgap. A wide-bandgap semiconductor is formed from a material selected from the group consisting of SiC, GaN, GaO, and diamond. If each of the semiconductor elements1aand1bis formed from a semiconductor material having a wide bandgap, losses in the semiconductor elements1aand1bcan be decreased. Since the losses in the semiconductor elements1aand1bcan be decreased, the capacity of the power semiconductor device100can be easily increased.

Each of the first lead frame2a,the second lead frame2b,and the third lead frame2cis formed from, for example, copper, aluminum, silver, or a copper-clad material which have high electric conductivities. Since high current needs to be conducted in the first lead frame2aand the second lead frame2b,a material having a low electric resistivity such as pure copper (C1020) is preferably selected. Each of the first lead frame2a,the second lead frame2b,and the third lead frame2cis made of, for example, a plate metal obtained by punching a metal flat plate having a fixed thickness by means of a press die or the like.

In the present embodiment, the semiconductor element1is thermally and electrically connected to the one-side surface of the heat spreader3. Thus, the heat spreader3is formed from, for example, copper, aluminum, silver, or a copper-clad material which have high electric conductivities, in the same manner as the above lead frames. Since the heat spreader3has a larger area than the lead frames, influence inflicted by the electric resistivity of the used material on electrical properties of the power module200is small. However, since the proportions of the volume and the mass of the heat spreader3in the power module200are large, the linear expansion coefficient of the heat spreader3inflicts large influences on the heat-cycle resistances of the highly-heat-dissipating insulation adhesive sheet6and the metal joining body8. The heat-cycle resistance is an index of deterioration of the insulation quality and the heat dissipation quality of the power module200after a heat cycle test. If the material of the cooler9is A6063, the linear expansion coefficient of A6063 is 21 [ppm/K] to 25 [ppm/K]. If a material having a linear expansion coefficient approximate to that of A6063 is selected, the heat-cycle resistance is improved. Meanwhile, from the viewpoint of heat dissipation quality, increase of heat dissipation is more easily realized if a copper material is selected, than if a material satisfying the linear expansion coefficient being 21 [ppm/K] to 25 [ppm/K] is selected. Thus, it is favorable to select a constituent in consideration of the trade-off relationship between heat-cycle resistance and increase of heat dissipation.

The highly-heat-dissipating insulation adhesive sheet6is a complex obtained by impregnating, with a resin, a porous ceramic sintered body in which ceramic particles have a gap and have been integrally sintered. The gap in the ceramic sintered body is filled with the impregnating resin. The proportion of the gap in the ceramic sintered body is, for example, favorably equal to or lower than 10% and ideally 0%. The resin is, for example, a thermosetting resin composition. The highly-heat-dissipating insulation adhesive sheet6is sealed by the sealing resin member5in a state where the ceramic sintered body is impregnated with the resin in a semi-cured state. After the sealing, the highly-heat-dissipating insulation adhesive sheet6and the sealing resin member5are cured by post-mold curing. The highly-heat-dissipating insulation adhesive sheet6has, for example, a dielectric breakdown voltage of 10.0 kV and a thermal conductivity at 25° C. of 100 W/(m·K).

The metal plate7is formed from, for example, the same material as that of the heat spreader3. If the metal plate7and the heat spreader3are formed from the same material, the highly-heat-dissipating insulation adhesive sheet6is sandwiched between the constituents formed from the same material, and thus the heat-cycle resistance is improved. Stress at a contact portion of the highly-heat-dissipating insulation adhesive sheet6generated by heat when the power module200and the cooler9are connected by means of the metal joining body8, is mitigated, and the resistance of the contact portion of the highly-heat-dissipating insulation adhesive sheet6to a heat cycle during use of the power semiconductor device100becomes high. Ideally, it is desirable that the metal plate7and the heat spreader3have the same thickness. If the material of the metal plate7is oxygen-free copper which is the same as the material of the heat spreader3, stress that is generated on the highly-heat-dissipating insulation adhesive sheet6does not change even when the metal plate7has a thickness of 0.3 mm or larger. Thus, the thickness of the metal plate7is preferably 0.3 mm or larger.

The sealing resin member5is, for example, a material in which an inorganic filler has been contained in a thermosetting resin such as epoxy resin. Stress that is generated on the sealing resin member5after sealing, is increased, and thus it is desirable to select, as the sealing resin member5, a material having a linear expansion coefficient approximate to those of the constituents of the power module200such that no peel occurs between the sealing resin member5and the constituents. Specifically, the sealing resin member5is desirably a material having a linear expansion coefficient approximate to that of the heat spreader3having a high proportion of volume and a high proportion of mass in the power module200. For example, if the heat spreader3is formed from oxygen-free copper, the linear expansion coefficient of the sealing resin member5is favorably 15 [ppm/K] to 19 [ppm/K]. The glass transition temperature Tg of the sealing resin member5is desirably equal to or higher than a maximum rated temperature of each of the semiconductor elements1aand1band is, for example, 175° C. or higher.

The joining bodies4a,4b,and4care each formed from, for example, a solder. The material of each of the joining bodies4a,4b,and4cis not limited to a solder and may be sintered Ag or sintered Cu which are highly-heat-conducting materials. The joining bodies4band4cmay be formed from the same material and may be joined together by using a means such as ultrasonic joining, since this enables concurrent connections thereof, i.e., from the viewpoint of manufacturability. Each joining body4ais included in a heat dissipation path through which heat generated from the corresponding one of the semiconductor elements1aand1bis transmitted to the cooler9. Thus, if a highly-heat-conducting material such as sintered Ag or sintered Cu is selected as a material of the joining body4a,further increase of the capacity of the power module200can be realized. In addition, the configuration of the power semiconductor device100according to the present disclosure is a configuration in which, as explained with a manufacturing process described later, the semiconductor element1and the heat spreader3are connected by means of the joining body4abefore the highly-heat-dissipating insulation adhesive sheet6is provided. This configuration eliminates the need for imposing constraint conditions regarding temperature, pressurizing force, and the like on the connection by means of the joining body4a.This elimination also contributes to increase of the capacity of the power semiconductor device100. As shown inFIG.7, the joining body4dis, for example, a bonding wire. A bonding wire can be used as the joining body4dbecause control current is a very small current as compared to power used for principal current. If a bonding wire is used as the joining body4d,it is possible to select, for example, a material such as aluminum, copper, gold, or the like as a material of the bonding wire.

COMPARATIVE EXAMPLE

A comparative example in which the highly-heat-dissipating insulation adhesive sheet6is used will be described with reference toFIG.16.FIG.16is a side view of the comparative example of the configuration in which the highly-heat-dissipating insulation adhesive sheet6is used. In the comparative example, metal circuit boards20each having a plate shape are respectively in contact with both surfaces of the highly-heat-dissipating insulation adhesive sheet6formed in a plate shape. In order to obtain two metal circuit boards20ensured to be insulated from each other, the highly-heat-dissipating insulation adhesive sheet6in which impregnation with the resin in a semi-cured state has been performed is interposed between the metal circuit boards20, and heating and pressure-bonding are performed so as to configure the two metal circuit boards20to be insulated from each other. During pressure-bonding, pressures are applied in the directions indicated by the arrows inFIG.16.

If the metal circuit boards20are manufactured by such a manufacturing method, portions of the highly-heat-dissipating insulation adhesive sheet6that are in contact with the metal circuit boards20are pressurized while an outer peripheral portion of the highly-heat-dissipating insulation adhesive sheet6that is not in contact with the metal circuit boards20is kept in an unconstrained state, during the heating and pressure-bonding. The resin in a semi-cured state flows in a direction toward the unconstrained outer peripheral portion. At this time, with a focus on a pressure generated inside the highly-heat-dissipating insulation adhesive sheet6, the internal pressure is maximized at the center of gravity of the highly-heat-dissipating insulation adhesive sheet6, and meanwhile, at the unconstrained outer peripheral portion of the highly-heat-dissipating insulation adhesive sheet6, the pressure on the said outer peripheral portion is zero. Since the pressure applied to the inside of the board of the highly-heat-dissipating insulation adhesive sheet6decreases in a direction toward the outer peripheral portion, a gap that is present inside the board of the highly-heat-dissipating insulation adhesive sheet6, particularly, near the outer peripheral portion, cannot be filled with the resin. Consequently, an electric discharge path is formed at a portion at which the gap remains, whereby the insulation reliability between the two metal circuit boards20decreases.

The phenomenon involving the presence of a portion at which the gap remains after pressurization, is considered to more prominently occur in the highly-heat-dissipating insulation adhesive sheet6than in a conventional insulation resin layer in which an inorganic powder filler having high heat conducting property such as ceramic particles is contained in a thermosetting resin such as epoxy resin. The internal pressure of the highly-heat-dissipating insulation adhesive sheet6changes according to the viscosity and the flow rate of the flowing resin on the basis of fluid dynamics. Since a higher viscosity of the resin leads to a higher internal pressure, a higher viscosity of the resin makes it more likely for the gap to be filled with the resin. Thus, the insulation quality of the highly-heat-dissipating insulation adhesive sheet6becomes higher. However, if the outer peripheral portion of the highly-heat-dissipating insulation adhesive sheet6is unconstrained, the pressure on the outer peripheral portion is zero as described above. Either in the conventional insulation resin layer or the highly-heat-dissipating insulation adhesive sheet6, the resin is softened and flows upon heating at the time of heating and pressure-bonding. In the conventional insulation resin layer, the resin and the ceramic particles flow together. Meanwhile, in the highly-heat-dissipating insulation adhesive sheet6, the ceramic sintered body and the impregnating resin do not flow together. Thus, even if the same resin is used for the conventional insulation resin layer and the highly-heat-dissipating insulation adhesive sheet6, the highly-heat-dissipating insulation adhesive sheet6has a higher resin flow rate and a lower nominal viscosity than the conventional insulation resin layer. Therefore, it is important for the highly-heat-dissipating insulation adhesive sheet6to have a structure that allows adhesion while improving the internal pressure.

In the present disclosure, the sealing resin member5which is uncured is injected under pressure into a mold in a state where the highly-heat-dissipating insulation adhesive sheet6and the like are placed in the mold. When the members including the highly-heat-dissipating insulation adhesive sheet6are sealed by the sealing resin member5, the highly-heat-dissipating insulation adhesive sheet6is thermally connected to the heat spreader3and the metal plate7in a closed space, whereby a hydrostatic pressurizing force is generated in the entire highly-heat-dissipating insulation adhesive sheet6on the basis of Pascal's law. Before the sealing resin member5is injected into the mold, the ceramic sintered body has a gap not filled with the resin. Upon injection of the sealing resin member5, the highly-heat-dissipating insulation adhesive sheet6is pressurized by injection pressure of the sealing resin member5so that the gap not filled with the resin is filled with the resin.

By thus configuring the power module200, the gap in the ceramic sintered body is filled with the impregnating resin in the highly-heat-dissipating insulation adhesive sheet6. Consequently, no electric discharge path is formed in the gap, whereby decrease of the insulation reliability of the power module200can be inhibited. The highly-heat-dissipating insulation adhesive sheet6is a complex obtained by impregnating, with the resin, the porous ceramic sintered body in which the ceramic particles have the gap and have been integrally sintered, and thus, since the highly-heat-dissipating insulation adhesive sheet6has a thermal conductivity at 25° C. of, for example, 100 W/(m·K), increase of heat dissipation in the power module200can be realized.

<Electrical Configuration of Power Module200>

An electrical connection configuration of the power module200will be described. Each of the semiconductor elements1aand1bhas an active surface portion and a passive surface portion on the one-side surface thereof and has an active surface portion on the other-side surface thereof, for example. Principal current of the power semiconductor device100is conducted to these active surface portions. The active surface portion on the one-side surface of each of the semiconductor elements1aand1bis connected to the first lead frame2aby means of the corresponding joining body4bso that power is inputted from, and outputted to, outside of the power module200. The active surface portion on the other-side surface of each of the semiconductor elements1aand1bis connected to the heat spreader3by means of the corresponding joining body4aso that power is inputted from, and outputted to, outside of the power module200via the second lead frame2bconnected to the heat spreader3. If the semiconductor elements1aand1bare switching elements, the passive surface portions on the front surface portions thereof are provided with control pads related to operations of the semiconductor elements1aand1b.There is also a case where protective control pads intended for overheat protection and overcurrent protection of the semiconductor elements1aand1bare provided. These control pads are connected to the third lead frames2cby means of the joining body4d.The joining body4dand the third lead frames2care shown inFIG.7explaining a manufacturing method described later.

Examples of the types of the semiconductor elements1aand1band the electrical configuration of the power module200will be described with reference toFIG.2toFIG.4. InFIG.2, the semiconductor element1ais a switching element, and the semiconductor element1bis a diode. The switching element is a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT). If one more power module200having the same configuration is disposed to be line-symmetric with an end portion of the first lead frame2athat is exposed from the sealing resin member5, and both lead frames are connected to each other, the two power modules200can perform, for example, an inverter operation. Each power module200in such a configuration is called an arm. One of the power modules200is referred to as an upper arm, and the other power module200is referred to as a lower arm. In each arm, current conduction from the second lead frame2bto the first lead frame2ais referred to as forward-direction current conduction and is made only on the switching element side. Meanwhile, current conduction from the first lead frame2ato the second lead frame2bis referred to as backflow current conduction and is made only in the diode.

InFIG.3, the power module200has only the semiconductor element1a.The semiconductor element1ais a switching element that includes a function of a diode, and is, for example, an RC-IGBT or an SiC-MOSFET. In this case, current flows to the semiconductor element la either in the forward direction or the backflow direction. Since heat generation occurs in the same element either in the forward direction or the backflow direction, the amount of heat generation is larger so that a more highly-heat-dissipating structure is needed, than in the configuration shown in FIG.2in which the switching element and the diode are combined.

FIG.4shows a configuration in which an upper arm and a lower arm are integrated in one power module200. Each of the semiconductor elements1aand1bis a switching element that includes a function of a diode, and is, for example, an RC-IGBT or an SiC-MOSFET. The semiconductor elements1aand1bare respectively connected to separate heat spreaders3, and a fourth lead frame2dmakes connection between the two heat spreaders3. With such a configuration, the size of the power semiconductor device100can be decreased. Although an example in which only one element is mounted on each heat spreader3has been presented inFIG.4, a configuration in which two or more switching elements are mounted on one heat spreader3or a configuration in which two or more diodes are mounted on one heat spreader3, may be employed. Alternatively, a configuration in which a plurality of the upper and lower arms are integrated may be employed.

At the time of an operation of the power semiconductor device100, a voltage that is, at most, equal to an element withstand voltage of each of the semiconductor elements1aand1bis generated between the power module200and the cooler9. The cooler9is always provided to be fixed to a base (not shown). A base portion is a portion that a person can touch by a hand. If dielectric breakdown occurs in the power semiconductor device100, high voltage is applied to the base portion. In the power semiconductor device100, insulation between the cooler9and each of the first lead frame2aand the second lead frame2bis ensured with a space insulation distance obtained in consideration of the creeping discharge resistance of the sealing resin member5. Further, insulation between the heat spreader3and the cooler9is ensured with a solid insulation withstand voltage of the highly-heat-dissipating insulation adhesive sheet6. When heat generated from each of the semiconductor elements1aand1bis dissipated to the cooler9, the dissipation always occurs via the highly-heat-dissipating insulation adhesive sheet6. Thus, setting of the thickness of the highly-heat-dissipating insulation adhesive sheet6to be large in order to ensure insulation, leads to decrease of heat dissipation quality. Since ensuring of insulation and increase of heat dissipation are in a trade-off relationship, the power semiconductor device100needs to be designed in view of both effects.

<Manufacturing Method for Power Semiconductor Device100>

A manufacturing method for the power semiconductor device100will be described with reference toFIG.5. The manufacturing method for the power semiconductor device100includes a member preparation step (S11), a sealing resin member injection step (S12), a curing step (S13), and a cooler connection step (S14). First three steps S11, S12, and S13among the four steps constitute a manufacturing method for the power module200.

The details of each step will be described. Here, a manufacturing method for the power semiconductor device100having the configuration shown inFIG.2will be described. The member preparation step is a step of preparing: the heat spreader3having a plate shape and having heat conducting property; the semiconductor elements1aand1bat least thermally connected to the one-side surface of the heat spreader3; the highly-heat-dissipating insulation adhesive sheet6having a plate shape and having the one-side surface thermally connected to the other-side surface of the heat spreader3; and the metal plate7having the one-side surface thermally connected to the other-side surface of the highly-heat-dissipating insulation adhesive sheet6. The power semiconductor device100shown inFIG.2further includes the first lead frame2a,the second lead frame2b,and the third lead frames2c,and thus these frames are also prepared in the present step.

The member preparation step includes a plurality of steps.FIG.6andFIG.7are side views of power module intermediates170and180in the manufacturing process for the power semiconductor device100.FIG.8is a diagram for explaining the manufacturing process for the power semiconductor device100according to the first embodiment. Each of the power module intermediates170and180is a structure obtained in the course of manufacturing the power module200.

In a first step of the member preparation step, the semiconductor elements1aand1bare thermally and electrically connected to the one-side surface of the heat spreader3by using the respective joining bodies4aas shown inFIG.6, whereby the power module intermediate170is formed. In the next step, the first lead frame2ais electrically connected to the one-side surfaces of the semiconductor elements1aand1bby using the respective joining bodies4bas shown inFIG.7. Then, the second lead frame2bis electrically connected to the one-side surface of the heat spreader3by using the joining body4c.Further, the third lead frames2care electrically connected to the control pad on the one-side surface of the semiconductor element1aby using the joining body4d.These lead frames are connected, whereby the power module intermediate180shown inFIG.7is formed. Connection of the first lead frame2ausing the joining bodies4band connection of the second lead frame2busing the joining body4cmay be concurrently performed or may be performed in separate steps. InFIG.7, each lead frame is bent in the upward direction in the drawing. However, the lead frame may be bent in a subsequent step.

In the next step, as shown inFIG.8, the one-side surface of the highly-heat-dissipating insulation adhesive sheet6is thermally connected to the other-side surface of the heat spreader3, and the one-side surface of the metal plate7is thermally connected to the other-side surface of the highly-heat-dissipating insulation adhesive sheet6. The highly-heat-dissipating insulation adhesive sheet6and the heat spreader3may be integrated with each other when the power module intermediate180is placed in a mold in the next sealing resin member injection step. Likewise, although the metal plate7and the highly-heat-dissipating insulation adhesive sheet6are integrated with each other inFIG.8, the highly-heat-dissipating insulation adhesive sheet6and the metal plate7may be integrated with each other when these members are placed in a mold in the next sealing resin member injection step.

The sealing resin member injection step is a step of injecting under pressure the sealing resin member5, which is uncured, into a mold in a state where the heat spreader3, the semiconductor elements la and lb, the highly-heat-dissipating insulation adhesive sheet6, the metal plate7, the first lead frame2a,the second lead frame2b,and the third lead frames2care placed in the mold. If the power module intermediate180, the highly-heat-dissipating insulation adhesive sheet6, and the metal plate7have not been integrated with each other, the metal plate7, the highly-heat-dissipating insulation adhesive sheet6, and the power module intermediate180are placed in this order in mold. The temperature of the mold is maintained at a fixed temperature in advance. The power module intermediate180, the highly-heat-dissipating insulation adhesive sheet6, and the metal plate7are retained in the mold for a predetermined time. The predetermined retaining time is, for example, 5 seconds or longer. After these members are retained for the predetermined retaining time, the sealing resin member5is injected into the mold under a fixed pressure. The sealing resin member injection step may involve transfer molding or injection molding. Further, a vacuum may be created before injection of the sealing resin member5. The metal plate7has the other-side surface exposed from the sealing resin member5after execution of the sealing resin member injection step.

From the time at which the injection of the sealing resin member5is completed, an internal pressure is hydrostatically generated in the entire highly-heat-dissipating insulation adhesive sheet6on the basis of Pascal's law. The generated pressure is equal to a molding pressure which is the injection pressure. Thus, a higher internal pressure can be generated in the highly-heat-dissipating insulation adhesive sheet6than in the case of performing pressurization in a state where a side surface is unconstrained as in the comparative example. Before execution of the sealing resin member injection step, the ceramic sintered body of the highly-heat-dissipating insulation adhesive sheet6has a gap not filled with the resin. In the sealing resin member injection step, the entire highly-heat-dissipating insulation adhesive sheet6is pressurized by the injection pressure of the sealing resin member5, whereby the gap not filled with the resin is filled with the resin. The proportion of the gap in the ceramic sintered body is, for example, favorably equal to or lower than 10% and ideally 0%. Since the gap not filled with the resin is filled with the resin, no electric discharge path is formed in the gap. Thus, the insulation reliability of the entire highly-heat-dissipating insulation adhesive sheet6including an edge of the highly-heat-dissipating insulation adhesive sheet6can be significantly improved. Since the insulation reliability of the highly-heat-dissipating insulation adhesive sheet6is improved, decrease of the insulation reliability of the power module200can be inhibited.

A thickness change rate of the highly-heat-dissipating insulation adhesive sheet6in the sealing resin member injection step is desirably equal to or higher than 1% and equal to or lower than 11%. If the sealing resin member injection step is performed under the condition that the thickness of the highly-heat-dissipating insulation adhesive sheet6does not change, the ceramic sintered body of the highly-heat-dissipating insulation adhesive sheet6does not follow a recess, a projection, and a distortion between the heat spreader3and the highly-heat-dissipating insulation adhesive sheet6, and between the highly-heat-dissipating insulation adhesive sheet6and the metal plate7. Consequently, an area of only the thermosetting resin composition which is the resin, may be formed. If the thickness change rate of the highly-heat-dissipating insulation adhesive sheet6in the sealing resin member injection step is set to be equal to or higher than 1% and equal to or lower than 11%, the ceramic sintered body of the highly-heat-dissipating insulation adhesive sheet6follows the recess, the projection, and the distortion. Consequently, the area of only the thermosetting resin composition is absent, and the heat dissipation quality of the power semiconductor device100can be improved. The thickness change rate of the highly-heat-dissipating insulation adhesive sheet6can be adjusted by, for example, optimizing the molding pressure and the retaining time in the sealing resin member injection step.

The curing step is a step of performing post-mold curing for concurrently curing the sealing resin member5and the resin of the highly-heat-dissipating insulation adhesive sheet6at a predetermined temperature. If the sealing resin member5and the resin of the highly-heat-dissipating insulation adhesive sheet6are thermosetting resins, the curing step is needed. The temperature in the post-mold curing is, for example, 175° C.FIG.9is a perspective view of a power module intermediate190having undergone the sealing resin member injection step.FIG.10is a cross-sectional view schematically showing the power module intermediate190, taken at the cross-sectional position B-B inFIG.9. As shown inFIG.10, the end portions of the first lead frame2a,the second lead frame2b,and the third lead frames2c(not shown inFIG.10), and the other-side surface of the metal plate7, are in a state of being exposed from the sealing resin member5. If tie-bar cutting work for cutting the lead frames and terminal bending work have not been performed on the power module intermediate190, the tie-bar cutting work and the terminal bending work are performed after the sealing resin member injection step and the curing step, whereby the power module200is formed.

The cooler connection step is a step of thermally connecting the cooler9via the metal joining body8to the other-side surface of the metal plate7that is exposed from the sealing resin member5. Through the cooler connection step, the power semiconductor device100shown inFIG.1is formed. The temperature is increased to a predetermined temperature, and the power module200and the cooler9are connected via the metal joining body8. For example, if the metal joining body8is formed from a solder, the temperature is increased to 200° C. or higher, and the power module200and the cooler9are connected. For the metal joining body8, a material that is used with the temperature thereof being increased to a temperature at which the joining bodies4a,4b,and4care not melted again during the cooler connection step, is selected. If the joining bodies4a,4b,and4care melted again at the temperature to which the temperature of the metal joining body8has been increased, the insulation reliability of the power module200considerably decreases.

As described above, the power module200according to the first embodiment includes: the heat spreader3having a plate shape; the semiconductor elements1aand1bat least thermally connected to the one-side surface of the heat spreader3; the highly-heat-dissipating insulation adhesive sheet6having a plate shape and having the one-side surface thermally connected to the other-side surface of the heat spreader3; the metal plate7having the one-side surface thermally connected to the other-side surface of the highly-heat-dissipating insulation adhesive sheet6; and the sealing resin member5sealing these members in a state where the other-side surface of the metal plate7is exposed. The highly-heat-dissipating insulation adhesive sheet6is a complex obtained by impregnating, with a resin, a porous ceramic sintered body in which ceramic particles have a gap and have been integrally sintered. Consequently, no electric discharge path is formed in the gap in the ceramic sintered body, and thus decrease of the insulation reliability of the power module200can be inhibited. The highly-heat-dissipating insulation adhesive sheet6is the complex obtained by impregnating, with the resin, the porous ceramic sintered body in which the ceramic particles have the gap and have been integrally sintered, and thus, since the highly-heat-dissipating insulation adhesive sheet6has a thermal conductivity at 25° C. of, for example, 100 W/(m·K), increase of heat dissipation in the power module200can be realized.

If the highly-heat-dissipating insulation adhesive sheet6and the heat spreader3are in contact with each other, and the highly-heat-dissipating insulation adhesive sheet6and the metal plate7are in contact with each other, only the component of the highly-heat-dissipating insulation adhesive sheet6is interposed between the highly-heat-dissipating insulation adhesive sheet6and the heat spreader3, and between the highly-heat-dissipating insulation adhesive sheet6and the metal plate7. Therefore, decrease of the heat dissipation quality of the power module200can be prevented. In addition, if each of the semiconductor elements1aand1bis formed from a semiconductor material having a wide bandgap, losses in the semiconductor elements1aand1bcan be decreased. Since the losses in the semiconductor elements1aand1bcan be decreased, the capacity of the power semiconductor device100can be easily increased.

The power semiconductor device100according to the first embodiment includes: the power module200according to the present disclosure; and the cooler9thermally connected via the metal joining body8to the surface of the metal plate7that is exposed from the sealing resin member5. Consequently, heat generated from each of the semiconductor elements1aand1binside the power module200can be efficiently dissipated from the cooler9to outside. The power module200according to the present disclosure can be manufactured in a mother factory, and the cooler connection step of connecting the cooler can be performed in another factory. Thus, the manufacturability of the power semiconductor device100can be improved, and manufacturing cost for the power semiconductor device100can be decreased.

The manufacturing method for the power module200according to the first embodiment includes: the member preparation step of preparing the heat spreader3having a plate shape, the semiconductor elements1aand1bat least thermally connected to the one-side surface of the heat spreader3, the highly-heat-dissipating insulation adhesive sheet6having a plate shape and having the one-side surface thermally connected to the other-side surface of the heat spreader3, and the metal plate7having the one-side surface thermally connected to the other-side surface of the highly-heat-dissipating insulation adhesive sheet6; and the sealing resin member injection step of injecting under pressure the sealing resin member5, which is uncured, into a mold in a state where the heat spreader3, the semiconductor elements la and lb, the highly-heat-dissipating insulation adhesive sheet6, and the metal plate7are placed in the mold. The metal plate7has the other-side surface exposed from the sealing resin member5after execution of the sealing resin member injection step. The highly-heat-dissipating insulation adhesive sheet6is a complex obtained by impregnating, with a resin, a porous ceramic sintered body in which ceramic particles have a gap and have been integrally sintered. The ceramic sintered body has a gap not filled with the resin before execution of the sealing resin member injection step. The sealing resin member injection step includes pressurizing the highly-heat-dissipating insulation adhesive sheet6by injection pressure of the sealing resin member5so that the gap not filled with the resin is filled with the resin. Consequently, no electric discharge path is formed in the gap. Thus, the insulation reliability of the entire highly-heat-dissipating insulation adhesive sheet6including the edge of the highly-heat-dissipating insulation adhesive sheet6can be significantly improved. Since the insulation reliability of the highly-heat-dissipating insulation adhesive sheet6is improved, decrease of the insulation reliability of each of the power module200and the power semiconductor device100can be inhibited.

If the thickness change rate of the highly-heat-dissipating insulation adhesive sheet6in the sealing resin member injection step is set to be equal to or higher than 1% and equal to or lower than 11%, the ceramic sintered body of the highly-heat-dissipating insulation adhesive sheet6follows a recess, a projection, and a distortion between the heat spreader3and the highly-heat-dissipating insulation adhesive sheet6, and between the highly-heat-dissipating insulation adhesive sheet6and the metal plate7. Consequently, the area of only the thermosetting resin composition which is the resin, is absent, and the heat dissipation quality of the power semiconductor device100can be improved. Since the manufacturing method for the power semiconductor device100according to the first embodiment includes the step of thermally connecting the cooler9via the metal joining body8to the surface of the metal plate7that is exposed from the sealing resin member5, it is possible to easily manufacture a power semiconductor device100in which heat generated from each of the semiconductor elements1aand1binside the power module200can be efficiently dissipated from the cooler9to outside.

Second Embodiment

A power semiconductor device100according to a second embodiment will be described.FIG.11is a cross-sectional view schematically showing the power semiconductor device100according to the second embodiment, taken at the same position as the cross-sectional position A-A inFIG.1.FIG.12is a cross-sectional view schematically showing the power semiconductor device100, taken at the cross-sectional position C-C inFIG.11. InFIG.12, the sealing resin member5is not shown. The power semiconductor device100according to the second embodiment is formed such that the highly-heat-dissipating insulation adhesive sheet6thereof has a size different from that in the first embodiment.

As seen in a direction perpendicular to the one-side surface of the metal plate7, an outer periphery portion of the highly-heat-dissipating insulation adhesive sheet6is located inward of an outer periphery portion of the metal plate7. In the present embodiment, as shown inFIG.12, the highly-heat-dissipating insulation adhesive sheet6is smaller at each edge thereof in the lateral direction than the metal plate7by X. Meanwhile, the highly-heat-dissipating insulation adhesive sheet6is smaller at each edge thereof in the longitudinal direction than the metal plate7by Y. The magnitudes of X and Y are larger than 0, and the highly-heat-dissipating insulation adhesive sheet6is formed to have an arbitrarily-selected size. If, at the outer periphery portion of the highly-heat-dissipating insulation adhesive sheet6, the resin protrudes from the highly-heat-dissipating insulation adhesive sheet6, the outer periphery portion of the highly-heat-dissipating insulation adhesive sheet6including the protruding resin is set to be located inward of the outer periphery portion of the metal plate7. The same applies also if the ceramic sintered body protrudes from the highly-heat-dissipating insulation adhesive sheet6.

If the outer periphery portion of the highly-heat-dissipating insulation adhesive sheet6protrudes from the metal plate7, flow of the sealing resin member5at the time of sealing the power module200leads to occurrence of chipping from the highly-heat-dissipating insulation adhesive sheet6or leads to generation of a crack in the highly-heat-dissipating insulation adhesive sheet6. In the case where chipping from the highly-heat-dissipating insulation adhesive sheet6occurs, a fragment chipped from the highly-heat-dissipating insulation adhesive sheet6remains inside the power module200in association with the flow of the sealing resin member5. Consequently, other members such as the semiconductor element1might be damaged, and the reliability of the power module200might be decreased. Meanwhile, in the case where a crack is generated in the highly-heat-dissipating insulation adhesive sheet6, the insulation reliability of the power module200might be decreased. It is noted that, if only the resin of the highly-heat-dissipating insulation adhesive sheet6protrudes, the reliability of the power module200might be decreased owing to generation of a foreign substance due to the resin in the same manner as in the case where chipping from the highly-heat-dissipating insulation adhesive sheet6occurs.

As described above, in the power semiconductor device100according to the second embodiment, as seen in the direction perpendicular to the one-side surface of the metal plate7, the outer periphery portion of the highly-heat-dissipating insulation adhesive sheet6is located inward of the outer periphery portion of the metal plate7. Consequently, none of the edges of the outer periphery of the highly-heat-dissipating insulation adhesive sheet6protrudes from the metal plate7. Thus, it is possible to inhibit: the risk that flow of the sealing resin member5at the time of sealing the power module200leads to occurrence of chipping from the highly-heat-dissipating insulation adhesive sheet6; and the risk that the said flow leads to generation of a crack in the highly-heat-dissipating insulation adhesive sheet6. Since the risk of occurrence of chipping from the highly-heat-dissipating insulation adhesive sheet6and the risk of generation of a crack in the highly-heat-dissipating insulation adhesive sheet6are inhibited, the reliability of each of the power module200and the power semiconductor device100can be improved.

Third Embodiment

A power semiconductor device100according to a third embodiment will be described.FIG.13is a cross-sectional view schematically showing the power semiconductor device100according to the third embodiment, taken at the same position as the cross-sectional position A-A inFIG.1. The power semiconductor device100according to the third embodiment is configured such that a step3ais formed in a side surface of the heat spreader3.

As seen in a direction perpendicular to the one-side surface of the heat spreader3, an outer periphery portion of the surface, of the heat spreader3, that is in contact with the highly-heat-dissipating insulation adhesive sheet6has at least one step3awhich is formed so as to be recessed from the outer periphery portion toward an inner portion of the heat spreader3. Although one step3ais provided in the present embodiment, the number of the steps3ais not limited to one, and two or more steps3amay be provided.

In the power semiconductor device100, a stress that is generated on the highly-heat-dissipating insulation adhesive sheet6owing to a heat cycle caused when the power semiconductor device100is used and when the power module200and the cooler9are connected via the metal joining body8, is largest at the outer periphery portion of the surface, of the heat spreader3, that is in contact with the highly-heat-dissipating insulation adhesive sheet6. The portion at which the stress increases, experiences heightening of the risk that chipping from the highly-heat-dissipating insulation adhesive sheet6occurs and the risk that a crack is generated in the highly-heat-dissipating insulation adhesive sheet6.

As described above, in the power semiconductor device100according to the third embodiment, as seen in the direction perpendicular to the one-side surface of the heat spreader3, the outer periphery portion of the surface, of the heat spreader3, that is in contact with the highly-heat-dissipating insulation adhesive sheet6has at least one step3awhich is formed so as to be recessed from the outer periphery portion toward the inner portion of the heat spreader3. Consequently, the area in which the heat spreader3and the sealing resin member5are in contact with each other increases at the portion at which the stress increases. Thus, the stress that is generated on the highly-heat-dissipating insulation adhesive sheet6can be decreased. Since the stress that is generated on the highly-heat-dissipating insulation adhesive sheet6is decreased, the heat-cycle resistance of the highly-heat-dissipating insulation adhesive sheet6is improved. Therefore, a power semiconductor device100having a high insulation reliability can be obtained.

Fourth Embodiment

A power semiconductor device101according to a fourth embodiment will be described.FIG.14is a perspective view schematically showing the power semiconductor device101according to the fourth embodiment.FIG.15is a cross-sectional view schematically showing the power semiconductor device101, taken at the cross-sectional position D-D inFIG.14. The power semiconductor device101according to the fourth embodiment includes two coolers9and9b.

In addition to the constituents of the power module200, a power module201includes: an additional heat spreader3bwhich has a plate shape and has heat conducting property and to which surfaces of the semiconductor elements1aand1bthat are on an opposite side to the heat spreader3are thermally connected; an additional highly-heat-dissipating insulation adhesive sheet6awhich has a plate shape and has heat conducting property and to which a surface of the additional heat spreader3bthat is on an opposite side to the semiconductor elements1aand1bis thermally connected; and an additional metal plate7ato which a surface of the additional highly-heat-dissipating insulation adhesive sheet6athat is on an opposite side to the additional heat spreader3bis thermally connected. The sealing resin member5seals the additional heat spreader3b,the additional highly-heat-dissipating insulation adhesive sheet6a,and the additional metal plate7ain a state where a surface of the additional metal plate7athat is on an opposite side to the additional highly-heat-dissipating insulation adhesive sheet6ais exposed.

In the present embodiment, the power module201includes the first lead frame2aand metal spacers10between the additional heat spreader3band the semiconductor elements1aand1b.The first lead frame2ais connected to the one-side surfaces of the semiconductor elements1aand1bby means of the joining bodies4b.The metal spacers10are thermally connected to the first lead frame2aby means of joining bodies4e.The metal spacers10are thermally connected to the additional heat spreader3bby means of joining bodies4e.Each metal spacer10is formed from, for example, copper, aluminum, silver, or a copper-clad material in the same manner as the first lead frame2a.Each joining body4eis formed from, for example, a solder, sintered Ag, or sintered Cu in the same manner as the joining body4a.

The power semiconductor device101includes the power module201and the coolers9and9b.The cooler9bis thermally connected via a metal joining body8ato the surface of the additional metal plate7athat is exposed from the sealing resin member5. In the same manner as the cooler9, the cooler9bis formed from, for example, an aluminum alloy or a copper material which have excellent heat conducting properties. In the same manner as the metal joining body8, the metal joining body8ais formed from, for example, a solder, sintered Ag, or sintered Cu, but the material of the metal joining body8ais not limited thereto.

Regarding a manufacturing method for the power module201, features that are added to the manufacturing method for the power module200described in the first embodiment will be described. The member preparation step includes further preparing: the additional heat spreader3bwhich has a plate shape and has heat conducting property and to which the surfaces of the semiconductor elements1aand1bthat are on the opposite side to the heat spreader3are thermally connected; the additional highly-heat-dissipating insulation adhesive sheet6awhich has a plate shape and has heat conducting property and to which the surface of the additional heat spreader3bthat is on the opposite side to the semiconductor elements1aand1bis thermally connected; and the additional metal plate7ato which the surface of the additional highly-heat-dissipating insulation adhesive sheet6athat is on the opposite side to the additional heat spreader3bis thermally connected. In the case where the power module201further includes the metal spacers10as shown inFIG.15, the metal spacers10are also prepared.

The sealing resin member injection step includes injecting under pressure the sealing resin member5, which is uncured, into a mold in a state where the heat spreader3, the semiconductor elements1aand1b,the highly-heat-dissipating insulation adhesive sheet6, the metal plate7, the additional heat spreader3b,the additional highly-heat-dissipating insulation adhesive sheet6a,and the additional metal plate7aare placed in the mold. The additional metal plate7ahas a surface exposed from the sealing resin member5after execution of the sealing resin member injection step, the surface being on an opposite side to a surface, of the additional metal plate7a,to which the surface of the additional highly-heat-dissipating insulation adhesive sheet6ais thermally connected. If the sealing resin member5and the resin of each of the highly-heat-dissipating insulation adhesive sheet6and the additional highly-heat-dissipating insulation adhesive sheet6aare thermosetting resins, the curing step is further performed.

A manufacturing method for the power semiconductor device101will be described. The cooler connection step includes thermally connecting the cooler9via the metal joining body8to the surface of the metal plate7that is exposed from the sealing resin member5, and thermally connecting the cooler9bvia the metal joining body8ato the surface of the additional metal plate7athat is exposed from the sealing resin member5. The coolers9and9bmay be concurrently connected or separately connected. Manufacturing in this manner makes it possible to easily manufacture a power semiconductor device101in which heat generated from each of the semiconductor elements1aand1binside the power module201can be efficiently dissipated from the coolers9and9bto outside.

As described above, in the power semiconductor device101according to the fourth embodiment, the power module201further includes: the additional heat spreader3bwhich has a plate shape and has heat conducting property and to which the surfaces of the semiconductor elements1aand1bthat are on the opposite side to the heat spreader3are thermally connected; the additional highly-heat-dissipating insulation adhesive sheet6awhich has a plate shape and has heat conducting property and to which the surface of the additional heat spreader3bthat is on the opposite side to the semiconductor elements1aand1bis thermally connected; and the additional metal plate7ato which the surface of the additional highly-heat-dissipating insulation adhesive sheet6athat is on the opposite side to the additional heat spreader3bis thermally connected. The sealing resin member5seals the additional heat spreader3b,the additional highly-heat-dissipating insulation adhesive sheet6a,and the additional metal plate7ain a state where the surface of the additional metal plate7athat is on the opposite side to the additional highly-heat-dissipating insulation adhesive sheet6ais exposed. Consequently, further increase of heat dissipation in the power module201can be realized. Since further increase of heat dissipation in the power module201is realized, it is possible to further increase the output of the power semiconductor device101and further decrease the size of the power semiconductor device101.

In the manufacturing method for the power module201according to the fourth embodiment, the member preparation step includes further preparing: the additional heat spreader3bwhich has a plate shape and has heat conducting property and to which the surfaces of the semiconductor elements1aand1bthat are on the opposite side to the heat spreader3are thermally connected; the additional highly-heat-dissipating insulation adhesive sheet6awhich has a plate shape and has heat conducting property and to which the surface of the additional heat spreader3bthat is on the opposite side to the semiconductor elements is thermally connected; and the additional metal plate7ato which the surface of the additional highly-heat-dissipating insulation adhesive sheet6athat is on the opposite side to the additional heat spreader3bis thermally connected. The sealing resin member5, which is uncured, is injected under pressure into a mold in a state where the heat spreader3, the semiconductor elements1aand1b,the highly-heat-dissipating insulation adhesive sheet6, the metal plate7, the additional heat spreader3b,the additional highly-heat-dissipating insulation adhesive sheet6a, and the additional metal plate7aare placed in the mold. The additional metal plate7ahas a surface exposed from the sealing resin member5after execution of the sealing resin member injection step, the surface being on the opposite side to the surface, of the additional metal plate7a,to which the surface of the additional highly-heat-dissipating insulation adhesive sheet6ais thermally connected. Consequently, it is possible to easily manufacture a power module200in which further increase of heat dissipation is realized.

Since the manufacturing method for the power semiconductor device101according to the fourth embodiment includes the step of thermally connecting the cooler9via the metal joining body8to the surface of the metal plate7that is exposed from the sealing resin member5, and thermally connecting the cooler9bvia the metal joining body8a to the surface of the additional metal plate7athat is exposed from the sealing resin member5, it is possible to easily manufacture a power semiconductor device101in which heat generated from each of the semiconductor elements1aand1binside the power module201can be efficiently dissipated from the coolers9and9bto outside.

DESCRIPTION OF THE REFERENCE CHARACTERS

2afirst lead frame

2bsecond lead frame

2cthird lead frame

2dfourth lead frame

5sealing resin member

6highly-heat-dissipating insulation adhesive sheet

7aadditional metal plate

8metal joining body

8ametal joining body

20metal circuit board

100power semiconductor device

101power semiconductor device

170power module intermediate

180power module intermediate

190power module intermediate