Power module

An object of the present invention is to provide a power module having high reliability. The power module according to the present invention, includes a circuit body and a case housing the circuit body. The case has a first case member including a first base plate and a second case member including a second base plate. The first case member has a first side wall portion formed in an arrangement direction of the first base plate and the second base plate. The second case member has a second side wall portion formed in the arrangement direction, the second side wall portion coupling to the first side wall portion. The first side wall portion and the second side wall portion are formed so as to have the sum of lengths of the first side wall portion and the second side wall portion in the arrangement direction smaller than the thickness of the circuit body. The first case member has a deforming portion smaller than the first base plate and the second base plate in rigidity.

TECHNICAL FIELD

The present invention relates to a power module, and particularly relates to a power module used for a power conversion device that controls a motor for vehicular drive.

BACKGROUND ART

A power conversion device including a power module having a power semiconductor module housed in a metal-made case having a heat dissipating unit, has been known. For example, electric vehicles, such as electric motor vehicles or hybrid motor vehicles, are equipped with this type of power conversion device.

The power semiconductor module is sealed with resin in a state where both front and back surfaces of a power semiconductor element have been soldered to conductive plates and electrode terminals have been exposed. The metal-made case has heat dissipating units to be attached to the respective conductive plates with an insulating adhesive having thermal conductivity, on both sides thereof. Each of the heat dissipating units includes a plurality of fins for dissipating heat, formed thereon. The metal-made case has a bottomed-can-shape including an opening on the side of one side end portion, with a flange portion. The power semiconductor module is housed in the metal-made case in a state where the electrode terminals of the power semiconductor element have been inserted through the opening of the metal-made case.

This metal-made case has a structure having a frame and two fin plates each including the plurality of fins formed, joined to each other. The frame includes openings facing front and back surfaces of a circuit body including the power semiconductor elements sealed with the adhesive, formed thereon. The openings include the pair of fin plates each having the plurality of fins, arranged and joined therein (for example, refer to PTL 1).

In this type of power semiconductor device, it is necessary to release heat generated by the power semiconductor element during conducting operation, to the exterior through a heat dissipating member. Therefore, when tensile stress occurs in the insulating adhesive under operating conditions in which thermal cycles are loaded, there is a risk that detachment occurs at a coupling interface. Therefore, a technique of causing compressive stress to remain in the insulating adhesive, has been disclosed (for example, refer to PTL 2).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, in order to cause compressive stress to remain in a circuit body sealed with resin in a state where both front and back surfaces of a power semiconductor element has been soldered to conductive plates and electrode terminals have been exposed, a power semiconductor module described in PTL 2 includes a distance between fin plates of a metal-made case, formed smaller than the thickness of the circuit body. When the circuit body is inserted into the metal case, it is necessary to widen the case to dimensions into which the circuit body can be put. There is a possibility that pressing force of a fin base portion varies (decreases) during this process. Thus, it is difficult to generate desired compressive stress stably.

Therefore, an object of the present invention is to provide a power module having high reliability by causing desired compressive stress to remain stably in an insulating layer and inhibiting a heat dissipating unit from being apart from a power semiconductor module.

Solution to Problem

In order to solve the above problem, a power module according to the present invention, includes: a circuit body having a power semiconductor element; and a case housing the circuit body. The case has: a first case member including a first base plate facing one surface of the circuit body; and a second case member including a second base plate facing another surface on a side opposite to the one surface of the circuit body. The first case member has a first side wall portion formed in an arrangement direction of the first base plate and the second base plate. The second case member has a second side wall portion formed in the arrangement direction, the second side wall portion coupling to the first side wall portion. The first side wall portion and the second side wall portion are formed so as to have a sum of lengths of the first side wall portion and the second side wall portion in the arrangement direction smaller than a thickness of the circuit body. The first case member has a deforming portion smaller than the first base plate and the second base plate in rigidity.

Advantageous Effects of Invention

Heat dissipation capable of inhibiting separation from a power semiconductor unit improves so that reliability can be improved.

DESCRIPTION OF EMBODIMENTS

First Embodiment

A power conversion device according to one embodiment of the present invention will be described below with reference to the drawings.

FIG. 1is an outer perspective view of the power conversion device according to the one embodiment of the present invention.FIG. 2is an exploded perspective view of the power conversion device illustrated inFIG. 1.

The power conversion device200is used for a power supply device of an electric motor vehicle or a hybrid motor vehicle. Not to be illustrated, the power conversion device200has an inverter circuit coupled to a motor generator, built therein. The power conversion device200also includes a booster circuit coupled to an external battery, and a control circuit that controls the entirety.

The power conversion device200has a housing main body201formed of aluminum-based metal, such as aluminum or aluminum alloy, and a bottom cover202fastened to the housing main body201with fastening members (not illustrated). The housing main body201and the bottom cover202can be formed by integral molding. An upper cover, not illustrated, is fastened to an upper portion of the housing main body201with fastening members so that a case is hermetically formed.

Peripheral walls211for forming a cooling channel are formed and a cooling chamber210is formed with the peripheral walls211and the bottom cover202, inside the housing main body201.

A supporting member220having a plurality of side walls221(four inFIG. 2), and a plurality of power modules100(three inFIG. 2) to be arranged between the respective side walls221, are housed in the cooling chamber210. Details of the power modules100will be described later.

A pair of through holes is provided to one side portion of the housing main body201. An inlet pipe203ais provided to one of the through holes. An outlet pipe203bis provided to the other of the through holes. A cooling medium, such as cooling water, flows into the cooling chamber210through the inlet pipe203a, flows through cooling passages between the side walls221of the supporting member220and the respective power modules100, and flows out of the outlet pipe203b. The cooling medium that has flowed out of the outlet pipe203b, is refrigerated by a cooling device, such as a radiator, not illustrated, and then circulates so as to flow into the cooling chamber210through the inlet pipe203aagain.

The cooling chamber210is sealed with a covering member240through a sealing member231. The covering member240has openings241each through which a direct-current positive electrode terminal35aof a power semiconductor element built in a power semiconductor module, housed in each of the power modules100is inserted. Peripheral edge portions of the covering member240are fixed to upper portions of the peripheral walls211forming the cooling chamber210, with fastening members not illustrated.

A capacitor module250including a plurality of capacitor elements251for smoothing direct-current power to be supplied to the inverter circuit, is housed in an outside region of the cooling chamber210of the housing main body201.

A direct-current side bus bar assembly261is arranged on upper portions of the capacitor module250and the power modules100. The direct-current side bus bar assembly261transmits the direct-current power between the capacitor module250and the power modules100.

A control circuit board assembly262including a driver circuit unit that controls the inverter circuit, is arranged above the direct-current side bus bar assembly261and the covering member240.

An alternating-current side bus bar assembly263is coupled to the power modules100so as to transmit alternating-current power. The alternating-current side bus bar assembly263has a current sensor.

The power modules100will be described with reference toFIGS. 3 to 10andFIGS. 14 to 18.

FIG. 3is an outer plan view of one of the power modules100according to the one embodiment of the present invention.FIG. 4is an outer side view of the power module100according to the one embodiment of the present invention.FIG. 5is a longitudinal sectional view taken along line A-A′ of the power module100illustrated inFIG. 3.FIG. 6is a cross sectional view taken along line B-B′ of the power module100illustrated inFIG. 3.FIG. 7is an exploded sectional view of the power module100illustrated inFIG. 6. Furthermore,FIGS. 8 to 10are views illustrating different parts of a manufacturing process of the power module100illustrated inFIG. 6.

Furthermore,FIG. 13is an outer perspective view of power semiconductor units to be housed in the power module100, viewed from the side of a front surface.FIG. 14is an outer perspective view of the power semiconductor units, viewed from the side of a back surface.FIG. 15is a perspective view in a state where sealing resin of the power semiconductor units illustrated inFIG. 13has been removed.FIG. 16is a perspective view before wire bonding is performed between electrode terminals and a power semiconductor element in each of the power semiconductor units illustrated inFIG. 15. Furthermore,FIG. 17is a sectional view taken along line IX-IX of a power semiconductor unit10A illustrated inFIG. 16. Note that, reference signs for members of a power semiconductor unit10B corresponding to those of the power semiconductor unit10A, are also added inFIG. 17.

As illustrated inFIGS. 5 and 6, the power module100including a power semiconductor module30having a switching element, to which transfer molding has been performed, housed in a metal-made case40that is a CAN cooler. Here, the CAN-typed cooler is a cooler having a flat and cylindrical shape, with an insertion opening17on one side and a bottom on the other side. The metal-made case40is formed of a member having electric conduction, such as a composite material of Cu, Cu alloy, Cu—C, or Cu—CuO, or a composite material of Al, Al alloy, AlSiC, or Al—C.

The power semiconductor module30functions as a circuit body including the power semiconductor elements and conductive plates, to be described later, modularized.

As illustrated inFIGS. 3 and 4, the metal-made case40includes a pair of heat dissipating members41each having a plurality of heat dissipating fins42. The pair of heat dissipating members41functions as a first case portion and a second case portion forming a housing space for the power semiconductor module30.

Here, each of the heat dissipating members41is integrally formed with a sealing portion11in a region on the side close to the opening of the metal-made case40, having the heat dissipating fins42on a base portion41b. Note that the base portions41balso function as base portions that sandwich the power semiconductor module30.

As illustrated inFIGS. 5 and 6, a side wall portion43for forming a side wall of the metal-made case40is integrally formed in a region in which the sealing portion11of each of the heat dissipating members41is not formed.

A deforming portion44is formed to each of the heat dissipating members41so as to surround the periphery of the base portion41b. The deforming portion44also couples the base portion41band the side wall portion43.

The deforming portion44is characterized in that the rigidity is smaller than that of the base portion41b. For example, as illustrated inFIGS. 5 and 6, a structure including the thickness of the deforming portion44thinner than the thickness of the base portion41b, can be made. For example, a recess portion44bis provided on a surface of each of the heat dissipating members41, on the side to be in contact with the power semiconductor module30. Thus, the deforming portion44thinner than the base portion41bcan be formed.

The pair of heat dissipating members41is joined at the respective side wall portions43. Examples of the joining that can be applied include friction stir welding (FSW), laser welding, and brazing. With the metal-made case having this type of shape, even when the power module100is inserted into a channel through which a coolant, such as water, oil, or organic matter, flows, the simple structure can prevent the cooling medium from entering the inside of the power module100.

As illustrated inFIGS. 5 and 6, a heat conductive insulating layer51is interposed between the power semiconductor module30housed in the metal-made case40and each of the pair of base portions41b. The insulating layers51conduct heat generated from the power semiconductor module30, to the heat dissipating members41b. The insulating layers51are formed of a material having high heat conductivity and large dielectric strength. For example, a thin film of aluminum oxide (alumina) or aluminum nitride, or an insulating sheet or an adhesive, including impalpable powder thereof, can be used. To be described later, the conductive plates33to36(refer toFIGS. 13 and 14) to which the power semiconductor elements are soldered, are exposed on both front and back surfaces of the power semiconductor module30. The insulating layers51couple the conductive plates33to36and the heat dissipating members41bso that heat conduction can be performed.

Gaps of the metal-made case40and the insulating layers51with respect to the power semiconductor module30are filled with second sealing resin49.

As illustrated inFIGS. 16 and 17, the conductive plate33on the side of an alternating-current output and the conductive plate34on the side of a direct-current negative electrode are arranged on the same plane on the side of the front surface of the power semiconductor module30.

As illustrated inFIG. 13, the first sealing resin6exposes an upper surface33bof the conductive plate33and an upper surface34bof the conductive plate34, and covers the entire periphery of the conductive plates33and34on the side of the front surface of the power semiconductor module30. A surface of the first sealing resin6is flush with the upper surface33bof the conductive plate33and the upper surface34bof the conductive plate34.

As illustrated inFIGS. 16 and 17, the conductive plate35on the side of a direct-current electrode and the conductive plate36on the side of the alternating-current output are arranged on the same plane on the side of the back surface of the power semiconductor module30.

As illustrated inFIG. 14, the first sealing resin6exposes an upper surface35bof the conductive plate35and an upper surface36bof the conductive plate36, and covers the entire periphery of the conductive plates35and36on the side of the back surface of the power semiconductor module30. Another surface of the first sealing resin6is flush with the upper surface35bof the conductive plate35and the upper surface36bof the conductive plate36.

As illustrated inFIG. 17, each of the power semiconductor element31U and a diode32U is attached between the conductive plate35and the conductive plate33through a solder material61on one side and through a solder material62on the other side. Similarly, each of the power semiconductor element31L and a diode32L is attached between the conductive plate36and the conductive plate34through solder materials61and62on one side and the other side, respectively.

FIG. 18is a circuit diagram of a circuit built in the power semiconductor module30according to the one embodiment. The following descriptions will be given with reference to the drawings together with the circuit diagram. The power semiconductor element31U, the diode32U, the power semiconductor element31L, and the diode32L are included in an upper-and-lower-arm series circuit121.

As illustrated inFIG. 15, the direct-current positive electrode terminal35ais formed on the conductive plate35on the side of the direct-current electrode, and an alternating-current output terminal36ais formed on the conductive plate36on the side of the alternating-current output. Bonding is performed to the power semiconductor element31U and the diode32U with respect to the conductive plate35on the side of the direct-current positive electrode so that an upper arm circuit is configured. Input and output portions of the power semiconductor element31U are coupled to a plurality of signal terminals24U through wires26U.

As illustrated inFIG. 15, bonding is performed to the power semiconductor element31L and the diode32L with respect to the conductive plate36on the side of the alternating-current output so that a lower arm circuit is configured26U. Input and output portions of the power semiconductor element31L are coupled to a plurality of signal terminals24L through wires26L.

As illustrated inFIGS. 15 and 16, the conductive plate35, the conductive plate33, the direct-current positive electrode terminal35a, the signal terminals24U, the power semiconductor element31U, and the diode32U are included in the power semiconductor unit10A. The conductive plate36, the conductive plate34, the alternating-current output terminal36a, signal terminals24L, the power semiconductor element31L, and the diode32L are included in the power semiconductor unit10B.

As illustrated inFIG. 15, a lead38is integrally formed with the conductive plate33. A leading end of the lead38is coupled to the conductive plate36. Accordingly, the power semiconductor unit10A and the power semiconductor unit10B are coupled to each other. The power semiconductor unit10B includes a temperature sensor8(refer toFIG. 15) for detecting the temperature of the conductive plate36, namely, the temperature of the power semiconductor element31L.

As illustrated inFIGS. 13 and 14, the power semiconductor module30has a structure including the power semiconductor unit10A and the power semiconductor unit10B that have been sealed with the first sealing resin6, and the direct-current positive electrode terminal35a, the signal terminals24U, the alternating-current output terminal36a, and the signal terminals24L that have been sealed with the second sealing resin15so as to be exposed from the periphery of the first sealing resin6.

[Method of Manufacturing the Power Module100]

As illustrated inFIGS. 13 and 14, the power semiconductor unit10A and the power semiconductor unit10B are sealed with the first sealing resin6so that the power semiconductor module30is formed.

As illustrated inFIG. 7, the insulating layers51are formed on both of the front and back surfaces of the power semiconductor module30, namely, on one side on which the upper surface33bof the conductive plate33and the upper surface34bof the conductive plate34have been exposed and on the other side on which the upper surface35bof the conductive plate35and the upper surface36bof the conductive plate36have been exposed. For example, a method of sticking an insulating sheet, or a method of applying an insulating adhesive can be used for the formation of the insulating layers51.

A manufacturing process until the above power semiconductor module30and insulating layers51are housed in the metal-made case40, will be described withFIGS. 7 to 10.

FIG. 7illustrates a state before the power semiconductor module30and the insulating layers51are sandwiched by the pair of heat dissipating members41.

A surface41ais a predetermined surface of one of the heat dissipating members41, to be contacted with one of the insulating layers51. A surface43bis a predetermined surface to be coupled to the side wall portion43of the other heat dissipating member41. A distance between the surface41aand the surface43bis defined as t1.

Similarly, a surface41cis a predetermined surface of the other heat dissipating member41to be contacted with the other insulating layer51. A surface43cis a predetermined surface to be coupled to the side wall portion43of the one of the heat dissipating members41. A distance between the surface41cand the surface43cis defined as t2.

The total thickness of the power semiconductor module30and the insulating layers51is defined as t3.

The side wall portions43of the pair of heat dissipating members41are formed so that the sum of the distance t1and the distance t2in length is shorter than the total thickness t3of the power semiconductor module30and the insulating layers51. Accordingly, the heat dissipating members41can cause compressive stress to remain in the power semiconductor module30and the insulating layers51. The deforming portions44having rigidity smaller than that of the base portions41bare provided between the side wall portions43and the base portions41b. Thus, deformation of the deforming portions44can absorb variation of processing dimensions of the power semiconductor module30.

As illustrated inFIG. 8, for example, pressing jigs45make pressurization P1to the base portions41bof the pair of heat dissipating members41so as to press the power semiconductor module30from the outside. The pressurization attaches the power semiconductor module30and the base portions41bon the front and back sides thereof through the insulating layers51. The pressurization may attach the pair of base portions41bat once, or may attach the base portions41bone by one.

After that, as illustrated inFIG. 9, second pressing jigs46make pressurization P2from the outsides of the side wall portions43of the pair of heat dissipating members41. Thus, the deforming portions44deform so that the surfaces43bto be coupled to each other of the side wall portions43of the pair of heat dissipating members41are in contact.

After that, as illustrated inFIG. 10, joining is made at coupling portions43eof the respective side wall portions43of the pair of heat dissipating members41. Examples of the joining that can be applied include friction stir welding (FSW), laser welding, and brazing.FIG. 10illustrates an exemplary state where the joining is made by thrusting a tool47of the friction stir welding (FSW).

During the above manufacturing process, the power module100illustrated inFIGS. 3 to 6is formed.

As illustrated inFIG. 6, the power module100formed in this manner, has a distance t5between a surface on which the fins of one of the base portions41bhave been formed and a surface on which the fins of the other base portion41bhave been formed, larger than a distance t4between an upper surface43dof one of the side wall portions43and an upper surface43dof the other side wall portion43.

A distance t7between bases of the respective deforming portions44of the pair of heat dissipating members41, on the sides of the base portions41b, is larger than a distance t6between bases of the respective deforming portions44on the sides of the side wall portions43.

As illustrated inFIG. 9, when the second pressing jigs46press the side wall portions43from the outsides and then the deforming portions44deform, for example, plastic deformation is performed with the pressing jigs45pressing the base portions41b. Thus, the base portions41bcan be prevented from rising due to bending deformation.

As illustrated inFIG. 6, the deforming portions44are coupled to positions apart from the centers of the base portions41bin a thickness direction so that flexural rigidity (the second moment of area) of the base portions41bincreases. Thus, the amount of bending deformation decreases so that an effect of inhibiting the rising near center portions of the base portions41bis acquired.

In particular, the deforming portions44are arranged on the sides of fins of the base portions41bin the thickness direction, namely, move away from the power semiconductor module30so that tensile stress to be generated at coupling surfaces between the base portions41band the insulating layers51can be reduced even in a case where the second sealing resin49expands due to a variation in temperature, such as temperature cycles, and the heat dissipating members41receive outward force. Thus, an effect that detachment is inhibited from occurring in interfaces between the insulating layer51, the conductive plate33, and the conductive plate34, is acquired.

According to the above results, causing the compressive stress to remain stably in the insulating sheets of the power module can be made, and the insulating sheets can be prevented from being detached. Therefore, the power module having high reliability can be achieved.

Second Embodiment

FIG. 11illustrates a modification of the power module illustrated inFIG. 6. Reference signs the same as those inFIG. 6indicate the same constituent components. Thus, the duplicate detailed descriptions will be omitted.

In the modification illustrated inFIG. 11, deforming portions44of heat dissipating members41bforming a metal-made case40are provided near the centers of base portions41bin a thickness direction.

Accordingly, flexural rigidity (the second moment of area) of fin bases decreases. Thus, during the use of the power module, an effect of inhibiting tensile stress from occurring in the deforming portions44is acquired and an effect of inhibiting fatigue failures from occurring in the deforming portions44is acquired even in a case where bending deformation occurs in the base portions41bor even in a case where outward deformation has been made.

Third Embodiment

FIG. 12illustrates another modification of the power module of the power conversion device illustrated inFIG. 6. Reference signs the same as those inFIG. 6indicate the same constituent components. Thus, the duplicate detailed descriptions will be omitted.

In the modification illustrated inFIG. 12, protruding portions48are provided to side wall portions43of heat dissipating members41forming a metal-made case40. The protruding portions48are formed so as to protrude in a direction that moves away from the metal-made case40. When the side wall portions43of the pair of heat dissipating members41are joined, an effect that pressurization is easily performed by second pressing jigs46, is acquired. In a case where the joining is performed by FSW, rigidity of coupling portions is secured and coupling is made to be easy. In addition, an effect of inhibiting heat generated at a leading end of a tool from being transmitted to coupling interfaces between insulating layers51and a power semiconductor module30, is acquired.

In the embodiments described above, the manufacturing process of performing the sandwiching with the heat dissipating portions41bafter the insulating layers51are formed on the power semiconductor module30, has been exemplified. However, the insulating layers51are not necessarily formed on the side of the power semiconductor module30, and may be previously provided on the side of the heat dissipating members41.

In the embodiment described above, a pin fin is applied to the shape of each of the heat dissipating fins42of the heat dissipating members41. However, other shapes, such as a straight fin and a corrugated fin, may be applied.

In the embodiments described above, the exemplary vehicular power conversion device with which an electric motor vehicle or a hybrid motor vehicle is equipped, has been described. The present invention can be similarly applied to a power conversion device having a cooling structure including a power module that is immersed in a cooling medium.

In addition, the present invention is not limited to the above embodiments. Various modifications can be made and applied within the scope of the spirit of the present invention.

REFERENCE SIGNS LIST