Coolant cooled type semiconductor device

A coolant cooled type semiconductor device capable of achieving a superior heat radiation capability is provided, while having a simple structure. While a plurality of semiconductor modules 1 are arranged in such a manner that main surface directions of these semiconductor modules 1 are positioned in parallel to each other in a interval along a thickness direction thereof. These semiconductor modules 1 are sandwiched by coolant tube 2 having folded portions with fixing members 6, 7, 10. As a consequence, both surfaces of the semiconductor module 1 can be cooled by a single coolant tube with a uniform pinching force.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a coolant cooled type semiconductor device.

2. Description of the Related Arts

To improve cooling characteristics of semiconductor modules that contain semiconductor chips having terminals, it has been proposed that water cooling type cooling members are made in contact with semiconductor modules so as to cool these semiconductor modules. Also, Japanese Laid-open Patent Application No. Hei-6-291223 has proposed a double-sided heat-radiating type semiconductor module in which heat is radiated from both surfaces of this semiconductor module.

However, in the above-described conventional water-cooling type semiconductor modules, a cooling member must be joined to the semiconductor modules, while maintaining superior heat transfer characteristics. To realize such superior heat transfer characteristics, there is the best way such that an electrode (also having heat transfer function) that is exposed from the main surfaces of the semiconductor modules is joined to the cooling member by a soldering material.

If the cooling member is a cooling unit through which water or coolant passes, the cooling unit may be connected to either a refrigerating cycle apparatus or a cooling water circulating apparatus. Therefore, the above-explained electrode member of the semiconductor module and the cooling member is set to a predetermined potential (normally, ground potential) equal to that of the refrigerating cycle apparatus, or the cooling water circulating apparatus.

However, when such an electrically insulating spacer is employed, since the electrode member of the semiconductor module cannot be joined to the cooling member, the electrode member of the semiconductor module and also the cooling member must be strongly pressed against the electrically insulating spacer under such a condition that uniform pinching pressure is given to the respective face portions in order to reduce the thermal resistance between the electrode member of the semiconductor module and the cooling member.

The above-described construction in which both the semiconductor module and the cooling member are strongly pressed against the insulating spacer under uniform pinching pressure would induce the complex entire structure. Also, the pinching force cannot be controlled easily. In other words, when the pinching force is low, the thermal resistance between the semiconductor module and the cooling member is increased, so that the cooling capability is lowered. To the contrary, when the pinching force is excessively high, the semiconductor chips built in the semiconductor module are broken.

Also, in order to cool double-sided of a large number of these semiconductor chips, or double-sided cooling type semiconductor card modules, a large number of the above-explained cooling members are branched, resulting in complex structures and increased manufacture cost. These increase the risk that fluids may be leaked due to an increased total number of joint places of the coolant distribution tubes.

SUMMARY OF THE INVENTION

The present invention has been made to solve the above-explained problem, and therefore, has an object to provide a coolant cooled type semiconductor device having a simple structure and also capable of realizing a superior heat radiation capability, and further capable of reducing a possibility of fluid leakages.

According to a first aspect of the present invention, a semiconductor device is disposed between a first cooling member and a second cooling member, a first insulating member is disposed between the first cooling member and the semiconductor device a second insulating member is disposed between the second cooling member and the semiconductor device. In this way, the semiconductor is insulated from the first and the second cooling member while heat generated in the semiconductor device radiates through the cooling members.

According to a second aspect of the present invention, a cooled type semiconductor device comprises: first and second cooling members, through which a coolant flows, pinching a semiconductor device therebetween tightly by a fixing member.

It is preferable that a cooling unit has a flat shape and has a first portion corresponding to the first cooling member, a second portion corresponding to the second cooling member, and a folded portion connecting the first and second portions.

According to a third aspect of the present invention, a cooled type semiconductor device comprises: a first semiconductor chip having a high side semiconductor switching element which has a first positive and a first negative electrodes, a second semiconductor chip having a low side semiconductor switching element which has a second positive and a second negative electrodes, wherein the first negative electrode and the second positive electrode are connected to a common mid terminal, the first positive electrode is connected to a high potential terminal and the second negative electrode is connected to a low potential terminal whose electric potential is lower than that of the high potential terminal.

According to a fourth aspect of the present invention, a cooled type semiconductor module comprising: a first heat radiating plate disposed on a main surface of the module and a second heat radiating plate disposed on a back surface of the module, wherein a heat sink contacts the first radiating plate, and a biasing-holding member connected with the heat sink presses the semiconductor module to the heat sink.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Referring now to drawings, a description will be made of a coolant cooled type semiconductor device according to first preferred embodiment of the present invention.

FIG. 1is a sectional view showing a substantial part of this coolant cooled type semiconductor device along a thickness direction thereof.

Structure of Semiconductor Module

The cooled type semiconductor module1has a coolant tube2and spacers3made of a metal or having a thermal transfer characteristic. More specially, the semiconductor module1has a semiconductor chip101ain which an IGBT element is formed, a semiconductor chip101bin which a flywheel diode is formed, a metal heat transfer plate102working as a heat sink as well as an electrode (namely, emitter side in this embodiment), and a metal heat transfer plate103working as a heat sink as well as an electrode (namely, collector side in this embodiment) likewise. Reference numeral104denotes soldering layers. A metal heat transfer plate102has projecting portions102aprojecting on sides of the semiconductor chips101aand101bthereof, and a projecting terminal portion102b. A metallic heat transfer plate103has a projecting terminal portion103b. A control electrode terminal105is connected to a gate electrode of the IGBT through a bonding wire108. Insulating plates8are disposed on both sides of the semiconductor module1. A sealing resin portion19seals the semiconductor chips101aand101b.

Both the semiconductor chips101aand101bare joined to a main surface (major surface) provided on an inner side of the metal heat transfer plate103by the soldering layer104, and the projecting portions102aof the metal heat transfer plate102are joined to main surfaces of the semiconductor chips101aand101bby the soldering layer104at an opposite side of the metal heat transfer plate103. As a result, an anode electrode and a cathode electrode of the flywheel diode are connected to a collector electrode and an emitter electrode of the IGBT in a so-called “back-to-back connection” manner. For instance, Mo and W are employed for the metal heat transfer plates102and103. The soldering layers104may be replaced with other joint function materials.

The two projecting portions102ahave a difference in thicknesses which are capable of absorbing a difference in thickness between the semiconductor chip101aand the semiconductor chip101b, so that an outer major surface of the metal heat transfer plate102constitutes a flat plane.

The sealing resin portion19is made of, for example, an epoxy resin, and is molded to cover side surfaces of these metal heat transfer plates102and103. As a result, both the semiconductor chips101aand101bare molded by the sealing resin portion19. It should be understood that the outer main surfaces, namely contact heat receiving surfaces of the metal heat transfer plates102and103are completely exposed.

The projecting terminal portions102band103bare provided to project from the sealing resin portion19in the right direction as viewed in FIG.1. Plural control electrode terminals105so-called “lead frame terminals” are connected to the gate (control) electrode of the semiconductor chip101awhere the IGBT is formed.

In this embodiment, each of the insulating plates8corresponding to an insulating spacer is composed of an aluminum nitride film, but alternatively other insulating films may be adopted. The insulating plates8closely contact the metal heat transfer plates102and103, while completely covering these heat metal transfer plates102and103. Alternatively, the insulating plates8may be simply made in contact with both the metal heat transfer plates102and103, or a heat transfer material such as silicone grease may be coated thereto. The insulating plates8can be joined to these metal heat transfer plates102and103by various methods. Further, each of the insulating plates8may closely contact the side of the coolant tube2.

The coolant tube2is manufactured in such a manner that an aluminum alloy is manufactured by either an extract-molding method or an extrude-molding method to form a plate member, and this plate member is cut off at a necessary length. As shown inFIG. 1, a sectional area of the coolant tube2, as viewed along a thickness direction thereof, has a large number of flow paths22which are partitioned by a large number of partition walls21. These partition walls21extend at a given interval in a flow path direction.

In accordance with this structure, the pinching pressure applied to the respective portions on the contact heat-receiving surface20of the coolant tube2can be made constant.

In this embodiment, each of the spacers (namely, soft material member)3is made of a soft metal plate such as a soldering alloy. Alternatively, the spacer3may be made of a film that is coated on a contact plane of the coolant tube2. The surface of this soft-material spacer3can be easily deformed by receiving pressure (will be explained later), and the deformed spacer3can be easily fitted to very fine concave/convex portions and cambers of the insulating material8, and also to very small concave/convex portions and cambers of the coolant tube2so that thermal resistance can be reduced by closely contacting. Optionally, grease having a thermal transfer characteristic may be coated on surfaces of the spacer3. Of course this spacer3may be omitted.

Structure of the Semiconductor Device

Referring now to FIG.2andFIG. 3, a description will be made on an example of a coolant cooled type semiconductor device with employment of the above-explained double-sided heat-radiating type semiconductor module.FIG. 2is a plane view for indicating this semiconductor device whose lid is taken out.FIG. 3is a cross-sectional view of this semiconductor device shown in FIG.2.

In the drawings, reference numeral1shows semiconductor modules, reference numeral2indicates the coolant tube, reference numeral4denotes a case whose one end is opened, and reference numeral5denotes smoothing capacitors. Also, reference numeral6denotes supporting plates, reference numeral7denotes through bolts, reference numeral10shows nuts, reference numeral11denotes a lid, reference numeral23denotes a coolant distribution tube on an inlet side, reference numeral24is a coolant distribution tube on an outlet side, reference numeral27shows a nut used to fix the coolant distribution tube. Reference numeral23ashows a tip portion of the coolant distribution tube23.

The coolant flat tube2is folded (bent) to have a winding shape and is disposed inside the case4. In this embodiment, the coolant tube2is folded three times so as to have three spaces. These three spaces are isolated from each other by three folded portions2a,2band2c. Three pairs of contact heat receiving planes20,20of the coolant tube2are disposed in each space respectively and are arranged along an up-and-down direction in FIG.2. Each pair of the contact heat receiving planes20,20extends to a right/left (lateral) direction inFIG. 2, so that each pair of the contact heat receiving planes20,20is disposed parallel to the other pairs as viewed in this drawing. These contact heat receiving planes20,20are made flat, and are located opposite and parallel to each other. Reference numerals2a,2b, and2crepresent curved (folded) portions of the coolant tube2.

One pair of the three pairs of the contact heat receiving planes20and20that is located at a lower position inFIG. 2, namely the flat portions of the both sides of the curved portion2aof the coolant tube2are closely contacted to both surfaces of the three double-sided heat-radiating type semiconductor modules1through a spacer3(not shown in FIG.2and FIG.3), so that the semiconductor modules1can radiate heat generated therein from both sides thereof which closely contact the contact heat receiving planes20,20. These three double-sided heat-radiating type semiconductor module1will constitute an upper arm (high side) of a 3-phase inverter circuit which drives a load such as a motor.

Another one pair of the three pairs of the contact heat receiving planes20and20that is located at an upper position inFIG. 2, namely the flat portions of the both sides of the curved portion2cof the coolant tube2are closely contacted to both surfaces of the three double-sided heat-radiating type semiconductor modules1through a spacer3(not shown in FIG.2and FIG.3), so that the semiconductor modules1can radiate heat generated therein from both sides thereof which closely contact the contact heat receiving planes20,20. These three double-sided heat-radiating type semiconductor module1will constitute a lower arm (low side) of a 3-phase inverter circuit.

The remaining pair of the three pairs of contact heat receiving planes20,20that are located at a center position, namely the flat portions of the both sides of the curved portion2bof the coolant tube2are closely contacted to the outer surface of two smoothing capacitors5.

Each of these semiconductor switching elements is arranged in such a manner that one flywheel diode has a back-to-back connection to one IGBT element, as explained in the above embodiment.

The smoothing capacitors5are connected between a positive DC power supply and a negative DC power supply of the above-explained 3-phase inverter circuit. These smoothing capacitors5are employed so as to prevent a switching noise from entering to the DC power supplies through a power supply line.

As previously described, both the surfaces of the respective double-sided heat-radiating type semiconductor modules1are closely contacted the contact heat receiving planes20of the coolant tubes2. Moreover, pinching plates6abut against the flat planes of the coolant tubes2and2provided on the lower and upper outermost sides. The through bolts7pass through both the upper end portions and the lower end portions of both the pinching plates6and6along a stacking direction, i.e., the up and down direction inFIG. 2, and are fastened by nuts10.

Fastening force of the nuts10is adjusted in such a manner that the pressure force applied to the semiconductor modules1exerted by the coolant tubes2becomes a predetermined value. In other word, such a pressuring member constituted by the pinching plate6, the through bolt7, and the nut10may have a function capable of setting the pinching force applied to the semiconductor module1exerted by the coolant tubes2, and also another function as a structural member capable of supporting the 3-phase inverter circuit apparatus.

As shown inFIG. 3, one end of the coolant tube2is joined to an inlet of a coolant distribution tube23, and the other end of the coolant tube2is joined to an outlet coolant distribution tube25. Both a tip end portion23aof the coolant distribution tube23and a tip end portion (not shown) of the coolant distribution tube25are projected from the bottom portion of the case4downwardly. A screw (thread) is formed on this tip end portion23a, and this screw may be coupled to a coolant distribution tube of an externally provided refrigerating cycle apparatus (not shown). It should be understood that this coolant tube2may constitute a portion of an evaporator of this refrigerating cycle apparatus, or the entire portion thereof. Reference numeral27shows a nut which fastens/fixes the coolant distribution tubes23and25onto a bottom portion of the case4.

In accordance with this structure, since the coolant tubes2can be detachably coupled to the external cooling mechanism (heat radiation apparatus) outside the case, even when the fluids (coolant) are leaked from these coupling portions (above-mentioned tip end portions), it is possible to avoid such an adverse influence caused by the short-circuit occurred in the circuit. Also, the apparatus can be partially replaced.

In accordance with this embodiment, since both the arms of the 3-phase inverter circuit are cooled by the same coolant which flows along the both of arms, fluctuations in the heat radiation capabilities between these arms can be reduced.

Also, a difference in cooling capabilities among the respective double-sided heat-radiating type semiconductor modules1disposed in the same arm can be reduced.

Furthermore, each of the double-sided heat-radiating type semiconductor modules1is pressured by a common pressuring member, i.e., the folded coolant tube2, so that pinching force per unit area as well as pinching areas, which is applied between each of the semiconductor modules1and the coolant tube2, is made substantially equal to each other.

As a result, a difference in the pinching force of the coolant tubes2with respect to the semiconductor modules1can be reduced. In other words, all of the semiconductor modules1are applied a substantial uniform pinching force with the folded coolant tube2.

After all, while the difference in the cooling capabilities among the respective semiconductor modules1is made small, such a compact semiconductor device having a superior cooling characteristic can be realized.

Also, while the smoothing capacitor5may also be cooled under better condition, in such a case that the double-sided heat-radiating type semiconductor module1radiates very large heat under a transient state, this smoothing capacitor5can absorb heat through the coolant tubes2, thereby functioning as a heat sink.

Modification

Even when the above-explained semiconductor module1of the embodiment is replaced by a semiconductor chip, a similar operation and effect may be achieved.

Second Embodiment

FIG.4andFIG. 5show a coolant cooled type semiconductor device according to another embodiment of the present invention.FIG. 4is a plan view for indicating this semiconductor device from which a lid thereof is taken out.FIG. 5is a cross-sectional view for representing this semiconductor device of FIG.4.

Structure of Semiconductor Device

In this semiconductor device of this embodiment, while the semiconductor module1, the coolant tube2, the smoothing capacitor5, and the pinching plate6are made in the same array as that of the embodiment1, this above-mentioned component set is sandwiched by three sets of leaf spring members9. This leaf spring member9, as shown inFIG. 6, is constituted by one piece of center leaf portion90b, and one pair of plate-shaped both edge portions90aand90a. The center leaf portion90bis arranged parallel to a bottom portion of the case4. One pair of both edge portions90aand90aare elongated from the respective both edge portions of this center leaf portion90bat a right angle, respectively, and also are located opposite to each other. Reference numeral91shows a groove portion which is formed in the center leaf portion90bof a large-sized spring member90.

In accordance with this embodiment, the respective members can be assembled in a simpler manner. In addition, pinching forces applied to the respective members do not have so much fluctuation in each other. In other words, the constant pinching force can be obtained in a simple manner, and also either the semiconductor chip or the double-sided heat-radiating type semiconductor module can be detachably mounted in a very simple manner, so that the replacement workability can be considerably improved.

Third Embodiment

Referring now to FIG.7andFIG. 8, a description will be made of an example of a coolant cooled type semiconductor device with employment of a dual-plane heat-radiating type semiconductor module.FIG. 7is a plane view for indicating this semiconductor device whose lid is taken out.FIG. 8is a cross sectional view for representing this semiconductor device of FIG.7.

Reference numeral1shows a semiconductor module, reference numeral2A indicates a coolant tube, reference numeral4denotes a case whose one end is opened, and reference numeral5represents one pair of smoothing capacitors which are connected in parallel to each other. Also, reference numeral6denotes a pinching plate, reference numeral9shows a leaf spring member, reference numeral11indicates a lid, reference numeral43denotes an inlet header, reference numeral44is an outlet header, and reference numerals25and26show coolant distribution tubes, and reference numeral27shows a nut used to fix the coolant distribution tubes.

The coolant distribution tubes25and26are fixed on a bottom portion of the case4by using nuts. Tip portions of the coolant distribution tubes25and26penetrate the bottom portion of the case4to be projected along the downward direction.

Both the coolant distribution tubes25and26are communicated to lower edges of the inlet header43and the outlet header44in an integral form within the case4. Both the inlet header43and the outlet header44own hollow plane shape. The headers43and44are stood on the bottom surface of the case4at a right angle within the case4, and are positioned opposite to each other in a parallel manner with an interval. Six pairs of coolant tubes2are arranged among main counter surfaces of both the inlet header43and the outlet header44.

The respective coolant tubes2are arranged in parallel to each other on the main surfaces of both the inlet and outlet headers43and44at the right angle. Both edges of these coolant tubes2are separately communicated and joined to both the inlet and outlet headers43and44. As will be explained later, each of these coolant tubes2owns a hollow thick-plate shape.

The coolant tubes2in each pair pinches the double-sided heat radiating type semiconductor module1. Six pieces of semiconductor modules1which constitute a 3-phase inverter circuit are sandwiched by different pairs of coolant tubes2and2.

The pinching plates6made of metal flat plates are closely contacted to outer-sided main surfaces of such coolant tubes2and2which sandwich the semiconductor module1. One set of these pinching plate6, coolant tube2, semiconductor module1, coolant tube2, and pinching plate6are pressed by the leaf spring member9. The pinching plate6may also function as a heat sink. The leaf spring member9has an U-shaped form made of a spring rigid plate. This plate spring member9sandwiches the above-explained set between both edge portions of this plate spring member9under certain pressure. It should also be noted that while the pinching plate6is omitted, one pair of coolant tubes2and2, the semiconductor module1, and the coolant tube2may be directly sandwich-pressured by this leaf spring member6.

The smoothing capacitor5owns a compressed shape, and a flat outer surface of this smoothing capacitor5is closely contacted to a rear main surface of the header44.

Each of the semiconductor modules1constitutes each of semiconductor switching elements of the 3-phase inverter circuit. Each of these semiconductor switching elements is arranged in such a manner that one flywheel diode is cross-coupled to one IGBT element. One of the paired semiconductor modules1and1constitutes a high-sided semiconductor module of a single-phase inverter circuit, whereas the other module of the paired semiconductor modules1and1constitutes a low-sided semiconductor module of the same single-phase inverter circuit. As a consequence, 3 pairs of these semiconductor modules1and1constitute a single-phase inverter circuit for a U-phase, a single-phase inverter circuit for a V-phase, and a single-phase inverter circuit for a W-phase, respectively. The smoothing capacitor5corresponds to such a smoothing capacitor which is connected between a positive DC power supply and a negative DC power supply of the above-explained 3-phase inverter circuit. This smoothing capacitor5is employed so as to suppress switching noise.

The coolants having the same flow rates and the same temperatures are supplied through the inlet header43to the respective coolant tubes2. Furthermore, since these coolant tubes are sandwich-pressured by a common sandwich-pressuring member, sandwich-pressure force per unit area, which is applied between each of the semiconductor modules1and the coolant tube2is made substantially equal to each other, and also the sandwich-pressure areas are made equal to each other. As a result, the sandwich-pressure force of the coolant tubes2with respect to the semiconductor modules1is made substantially equal to each other. As a result, the cooling capabilities of the respective semiconductor modules1can be made substantially equal to each other.

Fourth Embodiment

Structure of Semiconductor Device

FIG. 9is a plan view for indicating this semiconductor device whose lid is taken out.FIG. 10is a cross-sectional view for representing this semiconductor device of FIG.9.

In the drawings, reference numeral7indicates a through bolt, reference numeral10represents a nut.

Different features between the semiconductor device in the third embodiment and the semiconductor device in the fourth embodiment will be mainly explained below.

Six pairs of compressed coolant tubes2A are separately provided with a interval along a thickness direction thereof. Among each pair of these coolant tubes2A and2A, one pair of semiconductor modules1and1are sandwiched along a vertical direction of FIG.9.

As previously explained inFIG. 7, both surfaces of each phase of the semiconductor modules1and1are sandwiched by the coolant tubes2A and2A, while the smoothing capacitors5having the compressed cylindrical shapes are also sandwiched between the coolant tubes2A and2A as shown in FIG.9. In other words, Five spaces are disposed among the coolant tubes2A, one pair of the semiconductor modules and the smoothing capacitor5is disposed alternately in each space. Moreover, the pinching plates6abut against the coolant tubes2A and2A provided on the right and left outermost sides. The through bolts7pass through both the upper end portions and the lower end portions of both the pinching plates6and6along the stacking direction, and are fastened by the nuts10.

The fastening force of the nut10is adjusted in such a manner that the sandwich-pressure force applied to the semiconductor module1exerted by the coolant tubes2A and2A becomes a predetermined value. In other words, such a sandwich-pressuring member constituted by the pinching plate6, the through bolt7, and the nut10may have a function capable of setting the sandwich-pressure force applied to the semiconductor module1exerted by the coolant tubes2A and2A, and also another function as a structural member capable of assembling/supporting the 3-phase inverter circuit apparatus.

Therefore, since these coolant tubes are sandwich-pressured by a common sandwich-pressuring member, sandwich-pressure force per unit area, which is applied between each of the semiconductor modules1and the coolant tube2is made substantially equal to each other, and also the sandwich-pressure areas are made equal to each other as described above-mentioned embodiment.

Modification

Even when the above-explained semiconductor module1of the embodiment is replaced by a semiconductor chip, a similar operation effect may be achieved.

Fifth Embodiment

Structure of Semiconductor Device

FIG. 11is a plan view for indicating this semiconductor device, from which a lid thereof is taken out, andFIG. 12is a cross-sectional view for representing this semiconductor device of FIG.11.

In this semiconductor device of this embodiment, while a set of the semiconductor module1, the coolant tube2A, the smoothing capacitor5, and the pinching plate6are made in the same array as that of the fourth embodiment, this component set is sandwiched by a large-sized leaf spring member90in a batch mode.

This large-sized leaf spring member90is made by enlarging the leaf spring member9as explained in the third embodiment. The large-sized leaf spring member90is constituted by one piece of center leaf portion90b, and one pair of plate-shaped both edge portions90aand90a. The center leaf portion90bis arranged at an attitude parallel to the bottom portion of the case4. One pair of both edge portions90aand90aare elongated from the respective both edge portions of this center leaf portion90bat a right angle, respectively, and also are located opposite to each other. Reference numeral91shows a groove portion which is formed in the center leaf portion90bof the large-sized spring member90as shown in FIG.13.

In accordance with this embodiment, the respective members can be assembled in a simpler manner, and the pinching force having a small fluctuation can be applied to the respective members.

Moreover, since one piece of the pinching structure (large-sized spring member90) can apply the pinching force equal to each coolant tube2A, semiconductor module (semiconductor chips), and smoothing capacitor5, such a large current control semiconductor device having a compact and simple pinching construction can be realized.

Modifications of Detail Construction of Cooling System

A connecting structure of the headers43,44and the flat cooling tube2A shown inFIG. 7, for example, will next be explained with reference toFIGS. 14 and 15.FIG. 14shows a transversal sectional view of a main portion of the semiconductor device of FIG.7.FIG. 15shows a cross-sectional view taken along an arrow XV—XV of FIG.14.

The headers43,44respectively have opening portions50,60fitting the flat cooling tube2thereinto in connecting positions of the flat cooling tube2. The opening portions50,60are surrounded by concave portions51,61having a ring shape. These ring-shaped concave portions51,61are respectively constructed by inside sleeve wall portions52,62joined to end portions of the flat cooling tube2A, outside sleeve wall portions53,63, and ring-shaped bottom wall portions54,64connecting the inside sleeve wall portions52,62and the outside sleeve wall portions53,63.

The outside sleeve wall portions53,63face the inside sleeve wall portions52,62at predetermined intervals, and surround the inside sleeve wall portions52,62on outer sides. InFIG. 14, the concave portions51,61are formed in a U-shape biting into sides of the headers5,6. End portions of the flat cooling tube2are fitted into these opening portions50,60, and are soldered to inner circumferential faces of the inside sleeve wall portions52,62.

Incidentally, the opening portions50,60and concave portions51,61constitute connecting tube portions. Similar members of the headers43and44described in any following embodiments also constitute the connecting tube portions.

In accordance with this embodiment, the concave portions51,61of the headers43,44can be easily elastically deformed in the thickness direction (also called an X-direction) of the semiconductor module1in comparison with the flat cooling tube2A. Therefore, when positions of the flat cooling tube2A and the semiconductor module1are shifted in the above X-direction in assembly, this position shift can be absorbed by the elastic deformation.

In accordance with the coolant cooled type semiconductor device of the above embodiment, the following effects can be obtained.

A cooling fluid (coolant) at low temperature is uniformly distributed to each semiconductor module1, and dispersion of cooling effects can be reduced. Each semiconductor module1can radiate heat to the flat cooling tubes2A on both sides so that the cooling effects are excellent.

A pair of flat cooling tubes2A and the semiconductor module1are nipped and pressed by the U-shaped leaf spring member9as a pinching member. Accordingly, the semiconductor module1can come in close contact with the flat cooling tubes2A by a simple structure using uniform force in each portion so that contact heat resistance can be reduced.

The ring-shaped concave portions51,61constituting flat cooling tube connecting portions of the headers43,44surround the flat cooling tubes2A. In addition, plate thickness of these ring-shaped concave portions51,61are set to be equal to or smaller than an average thickness of the flat cooling tubes2A in the X-direction so that rigidity of the ring-shaped concave portions51,61in the X-direction is set to be smaller than that of the flat cooling tubes2A. Accordingly, when a space width between the pair of flat cooling tubes2A is smaller than a thickness of the semiconductor module1, and positions of the flat cooling tubes2A and the semiconductor modules1are misarranged, this error in size can be preferably absorbed without curving the flat cooling tubes2A in a bow shape. As a result, the flat cooling tube2A can preferably come in contact with the above metallic heat radiating plate of the semiconductor module2A without irregularities on each portion of main faces of the flat cooling tube coming in contact with the semiconductor module.

Modified Mode

In the above embodiment, the flat cooling tube2A can be displaced by the ring-shaped concave portions51,61in the X-direction. However, a thin sleeve portion may be projected from each of the headers43,44to an end portion of the flat cooling tube2A, and the flat cooling tube2A may be also joined to this sleeve portion.

In this case, this sleeve portion can be easily elastically deformed in the X-direction with main portions of the headers43,44as starting points. Therefore, while the deformation of the flat cooling tube2A itself is restrained, the flat cooling tube2A is displaced in the X-direction, and the flat cooling tube2A and the semiconductor module1can preferably come in close contact with each other.

When a thin connecting tube portion formed separately from the flat cooling tube2A and the headers43,44is interposed between the flat cooling tube2A and the headers43,44, similar to the above case, this connecting tube portion can be preferentially elastically deformed so that similar effects can be obtained. Further, portions of the headers43,44connected to the flat cooling tube2A may be also plastically deformed instead of the elastic deformation. However, the elastic deformation is advantageous since no hindrance is caused in repetitious exchange of the semiconductor module1, etc. Furthermore, there are also effects in that force of this elastic deformation can be utilized as one portion or all portions of force for pressing and biasing the flat cooling tube2A against the semiconductor module1.

Sixth Embodiment

A coolant cooled type semiconductor device in another embodiment will be explained with reference toFIGS. 16 and 17. In this embodiment, the flat cooling tube2A on an outermost side in the X-direction among the flat cooling tubes2A inFIGS. 14 and 15is replaced with a first high rigid flat cooling tube45, and an (N+2)-th flat cooling tube2A (N is an integer equal to or greater than one) from the first high rigid flat cooling tube45is changed to a second high rigid flat cooling tube46. The first and second high rigid flat cooling tubes45,46are fixed to the headers43,44without the ring-shaped concave portions51,61shown inFIGS. 14 and 15.

In this embodiment, a coil spring40is interposed instead of the U-shaped leaf spring member9shown inFIGS. 14 and 15between a pair of flat cooling tubes2A,2A facing each other.

The central second flat cooling tube46in the X-direction cools semiconductor modules1on both sides in the X-direction. Therefore, the second high rigid flat cooling tube46has a flow path section larger than that of each of the other flat cooling tubes2A,45.

The first and second flat cooling tubes45,46are set to be thick and have very high rigidity so that no first and second flat cooling tubes45,46are easily displaced in the X-direction in comparison with the flat cooling tube2A. As a result, if a bus bar is wired with these first and second flat cooling tubes45,46as references in connection of the bus bar to the semiconductor module1, dispersion of a connecting position of the bus bar and the semiconductor module1is reduced, and a connecting work of a joining portion can be easily made.

Modified Mode

A modified example of the semiconductor device of this embodiment will be explained with reference toFIGS. 18 and 19. In this embodiment, the coil spring40of the above embodiment shown inFIGS. 16 and 17is changed to a leaf spring41. In accordance with this construction, an insertion work of the leaf spring41is easily made in comparison with the coil spring40so that an assembly process can be simplified. Further, since the leaf spring41can face the flat cooling tube2A over a wide area in comparison with the coil spring40, the leaf spring41can further uniformly bias each portion of the flat cooling tube2A through the pinching plate6.

Seventh Embodiment

A coolant cooled type semiconductor device of another embodiment will be explained with reference toFIGS. 20to22. In this embodiment, a cap47is attached to each of end faces of the flat cooling tube2A, and each of end faces is covered with the cap47. Instead of this, a pair of header communication opening portions48,48opened into headers43,44in a cooling fluid circulating direction (in the X-direction) is formed in the flat cooling tube2A.

The headers43,44respectively have elastic sleeve portions500,600. The elastic sleeve portions500,600are located between a pair of flat cooling tubes2A,2A nipping the semiconductor module1, and have a bellows shape in both end openings each surrounding the header communication opening portion48and soldered to the flat cooling tube2A. The headers43,44also respectively have rigid sleeve portions501,601. The rigid sleeve portions501,601are located between a pair of flat cooling tubes2A,2A adjacent to each other on a non-existing side of the semiconductor module1, and have a straight tube shape in both end openings each surrounding the header communication opening portion48and soldered to the flat cooling tube2A. Each of the elastic sleeve portions500,600has a through hole communicated with the header communication opening portion48and a circumferential wall portion surrounding the through hole. This circumferential wall portion is constructed by a short metallic sleeve formed in a bellows shape, etc. Accordingly, both end portions of the flat cooling tube2A, the elastic sleeve portions500,600and the rigid sleeve portions501,601are integrated with each other by soldering and the like so as to constitute the headers.

In accordance with this embodiment, since the elastic sleeve portions500,600are formed in the bellows shape easily elastically deformed, the elastic sleeve portions500,600can be extended and contracted by nipping pressure of the U-shaped leaf spring member9in accordance with the thickness of the semiconductor module1. Thus, the semiconductor module1and the flat cooling tube2A can preferably come in contact with each other without curving and deforming the flat cooling tube2A. Further, a clearance for inserting the semiconductor module between the flat cooling tubes2A,2A prior to the insertion of the semiconductor module1can be set to be large so that an insertion work of the semiconductor module1can be easily made.FIG. 22is a side view of the flat cooling tube2A seen from the X-direction.

Eighth Embodiment

A coolant cooled type semiconductor device in another embodiment will be explained with reference toFIGS. 23to25. In this embodiment, in the semiconductor device of the above embodiment shown inFIGS. 20to22, the rigid sleeve portions501,601are omitted, and a central flat cooling tube2B except for flat cooling tubes2A in both end portions in the X-direction comes in contact with each of semiconductor modules1,1on both sides in the X-direction. An entire set of the semiconductor module and the flat cooling tube is nipped and pressed by a single U-shaped leaf spring member9ain the X-direction.

In accordance with this embodiment, the rigid sleeve portions501,601of the above embodiment can be omitted, and the semiconductor device can be made compact and the number of assembly works can be reduced in comparison with the above embodiment. However, in this embodiment, it is preferable to uniformly cool each semiconductor module1by increasing a cooling fluid flow path section of the central flat cooling tube2A for cooling the semiconductor modules1on both sides.

Ninth Embodiment

A coolant cooled type semiconductor device in another embodiment will be explained with reference to FIG.26. This embodiment is characterized in that the headers43,44respectively have flange-shaped sleeve portions502,602having a large diameter and adjacent to the semiconductor module1.

This flange-shaped sleeve portion501can easily elastically deformed in the X-direction so that the flat cooling tube2A can be displaced on each of both sides of the semiconductor module1. When ring-shaped concave portions are arranged instead of the flange-shaped sleeve portions502,602around the headers43,44, similar effects can be obtained, but a problem of an increase in fluid resistance within the headers43,44is caused.

In this embodiment, portions of the headers43,44between the flat cooling tubes2A,2A adjacent to each other without nipping and supporting the semiconductor module1are set to rigid sleeve portions55a,65ahaving a straight tube shape. However, the flat cooling tube2A can be easily elastically or plastically deformed in the X-direction by setting these header portions to flange-shaped sleeve portions, ring-shaped concave portions or bellows portions.

Tenth Embodiment

A coolant cooled type semiconductor device in another embodiment will be explained with reference toFIGS. 27 and 28.

This embodiment is characterized in that a flat cooling tube2C on one side of the semiconductor module1is set to be thick and have high rigidity in a thickness direction of the semiconductor module in the semiconductor device, and a flat cooling tube2D on the other side of the semiconductor module1is set to be thin and have low rigidity (easily deformed) in the thickness direction of the semiconductor module, and the ring-shaped concave portions51,61of the headers43,44are omitted.

The above difference in rigidity may be also obtained by changes in materials and shapes instead of the construction in which the flat cooling tube2D is thinly formed in comparison with the flat cooling tube2C.

In accordance with such a construction, when the flat cooling tube2A is nipped and pressed by the U-shaped leaf spring9, the flat cooling tube2A on the low rigid side is curved in a bow shape on a side of the semiconductor module1and comes in close contact with the semiconductor module1as shown inFIG. 27so that the following effects can be obtained.

The semiconductor module1can preferably come in face contact with the flat cooling tube2C on one side even when an error in size is caused. Accordingly, cooling can be secured.

The position of the semiconductor module1in the X-direction can be positioned with respect to the high rigid flat cooling tube2C.

At least a central portion of the other flat cooling tube2ccurved in a bow shape can also come in close contact with the semiconductor module1by bow-shaped curvature of this flat cooling tube2c. Accordingly, great heat radiating performance can be secured in comparison with a case in which there is no such curvature.

It is not necessary to form an elastic deforming structure in the headers43,44or connecting portions of the headers43,44and the flat cooling tubes2C,2D so that the structure becomes simple.

The flat cooling tube2D of low rigidity may be curved by the U-shaped leaf spring member9in the bow shape in the X-direction in an elastic limit range, and may be also curved in a plastic deforming range exceeding the elastic limit.

In this embodiment, connecting tube portions of headers43and44, which connect to the flat cooling tubes2C and2D, are rigid in comparison with those constituted by the opening portions50,60and concave portions51,61shown in FIG.14.

Incidentally, both ends of each flat cooling tube2D or2C connecting to both of the header43and44, respectively serve as connecting tube portions to the header43and44.

Eleventh Embodiment

A coolant cooled type semiconductor device in another embodiment will be explained with reference to FIG.29.

In this embodiment, one of a pair of flat cooling tubes nipping the semiconductor module1is set to have low rigidity by a method different from that in the tenth embodiment. Namely, a flat cooling tube2E is formed as a low rigid portion by boring in both end portions of the flat cooling tube2A of the third embodiment, for example. The flat cooling tube2E is also set to be thin and have no partition wall.

Thus, while deformation of the flat cooling tube2E is restrained by giving high rigidity to a central portion of the flat cooling tube2E coming in contact with the semiconductor module1, both end portions of the flat cooling tube2E can be set to have low rigidity. Accordingly, the central portion of the flat cooling tube2E can preferably come in close contact with the semiconductor module1by biasing the U-shaped leaf spring member9.

Modified Mode

FIG. 32shows a modified structure of the cooling unit. This modified mode adopts a structure in which the flat cooling tube2E is pressed against the semiconductor module1by the coil spring40already described instead of the U-shaped leaf spring member9.

Twelfth Embodiment

A coolant cooled type semiconductor device in another embodiment will be explained with reference to FIG.30.

In this embodiment, the flat cooling tube2A is set to have low rigidity by a method different from that in the tenth or eleventh embodiments. Namely, a central portion2fof the flat cooling tube in this embodiment is connected to a tip portion2gof the flat cooling tube connected to the headers43,44by a thin flange-shaped sleeve portion2hhaving a large diameter. A central portion of the flange-shaped sleeve portion2his formed such that a diameter of this central portion is larger than that of each of both end portions of the flange-shaped sleeve portion2h. The same shape as the central portion is formed.

Thus, while deformation of the flat cooling tube is restrained by giving high rigidity to the central portion2fof the flat cooling tube coming in contact with the semiconductor module1, the flange-shaped sleeve portion2hcan be set to have low rigidity. Accordingly, the central portion2fof the flat cooling tube can preferably come in close contact with the semiconductor module1by biasing the U-shaped leaf spring member9.

Modified Mode

FIG. 33shows a modified structure of the cooling unit. In this modified mode, the coil spring40described above is used instead of the U-shaped leaf spring member9.

Thirteenth Embodiment

A coolant cooled type semiconductor device in another embodiment will be explained with reference to FIG.31.

In this embodiment, both end portions of the flat cooling tube are set to have low rigidity by a method different from that in the tenth through twelfth embodiments. Namely, each of both end portions of the flat cooling tube in this embodiment has a thin flange-shaped sleeve portion2ihaving a large diameter. This flange-shaped sleeve portion2ihas a ring-shaped concave portion2ksurrounding a thick central portion2fof the flat cooling tube.

Modified Mode

FIG. 34shows a modified mode. In this modified mode, the coil spring40already described is used instead of the U-shaped leaf spring member9.

Fourteenth Embodiment

A coolant cooled type semiconductor device in another embodiment will be explained with reference toFIGS. 35A and 35B.

In this embodiment, flat cooling tubes2A,2A of the semiconductor module1are formed in the same shape, and are plastically deformed in a direction away from the semiconductor module1previously (FIG.35A), whereby the width of a space for inserting the semiconductor module1thereinto is sufficiently secured. After the semiconductor module1is inserted, the flat cooling tubes2A,2A are deformed by biasing the U-shaped leaf spring member9, and come in contact with the semiconductor module1by a predetermined pressure (FIG.35B). Thus, an insertion work of the semiconductor module1can be simplified.

The flat cooling tube45having low rigidity as described above and the flat cooling tube2A having high rigidity may be also utilized instead of the flat cooling tubes2A,2A.

Fifteenth Embodiment

A coolant cooled type semiconductor device in another embodiment will be explained with reference toFIGS. 36 and 37.

In this embodiment, a base plate10000is arranged below the flat cooling tube2A in an arranging direction (X-direction) of the semiconductor modules. The headers43,44are fixed to this base plate1000.

A pair of fixing wall portions1001is fixed vertically to the base plate1000. Two sets each constructed by a pair of the flat cooling tube2A and the flat cooling tube2E having low rigidity in comparison with the flat cooling tube2A and a semiconductor module1pinched by these flat cooling tubes2A,2E are arranged between both the fixing wall portions1001. Pressing (sandwiching) plates33,33and a wedge-shaped member1002are arranged between both sets. Each of the pressing plates33,33comes in close contact with a main face of the flat cooling tube2E on a side opposed to the semiconductor module, and is increased in thickness toward a downward direction. A surface of the pressing plate33on a side of the wedge-shaped member is set to a slanting face. The wedge-shaped member1002is formed in a shape thinned toward the downward direction. A bolt is inserted into the wedge-shaped member1002, and a tip portion of the bolt is screwed into the base plate1000as shown in FIG.37. Accordingly, the wedge-shaped member1002is moved toward the base plate1000, so that the wedge-shaped member1002thrust the pressing plates33,33and the flat cooling tubes2E,2E in a lateral direction parallel to the base plate1000. As a result, semiconductor modules1come in close contact with the flat cooling tubes2A,2A by fastening the bolt. The wedge-shaped member1002is pushed steady and prevented from returning backward by the bolt.

Modified Mode

The pressing plate33can be molded integrally with the flat cooling tube2A.

Sixteenth Embodiment

This embodiment will be explained to show another type of semiconductor module having an object to provide both a semiconductor switching module capable of constituting a compact three-phase power inverter circuit, and also a semiconductor device realized by employing this semiconductor switching module.

FIG. 38is a sectional view for showing a semiconductor switching module along a thickness direction thereof, andFIG. 39is a sectional view for representing a semiconductor device with employment of this semiconductor switching module along a thickness direction thereof.

Structure of Semiconductor Switching Module

InFIG. 38, reference numeral201shows a high-sided plate, reference numeral202indicates a low-sided plate, reference numeral202ashows a spacer, reference numeral203indicates a middle-sided plate, reference numeral203arepresents another spacer, reference numeral204adenotes a semiconductor chip provided on the high side, and reference numeral204bshows a semiconductor chip provided on the low-side. Also, reference numeral205shows a soldering layer, reference numeral206arepresents a control electrode terminal, reference numerals207aand207bindicate bonding wires, reference numeral208denotes a sealing resin portion, reference numeral209shows an outer main surface (major plane) of the low-sided plate202, reference numeral11represents an outer main surface (major plane) of the high-sided plate201, and reference numeral212shows an outer main surface of the middle-sided plate203.

The high-sided plate1, the low-sided plate202, the spacer202a, the middle-sided plate203, and the spacer203aare plane plates and made of metal such as tungsten and molybdenum. Alternatively, these members may be made of such as copper, or an aluminum alloy.

The semiconductor chip204ais interposed between an inner main surface of the high-sided plate201, and one surface of main surfaces of the spacer203a. Therefore, semiconductor chip204ais joined to both these surfaces by way of the soldering layer205. The other surface of the main surfaces of the spacer203ais joined to an inner main surface of the middle-sided plate203by the soldering manner.

The semiconductor chip204bis interposed between an inner main surface of the middle-sided plate203, and one surface of main surfaces of the spacer202a. Therefore, the semiconductor chip204bis joined to both these surfaces by way of the soldering layer205. The other surface of the main surfaces of this spacer202ais joined to an inner main surface of the low-sided plate202by the soldering manner.

The spacers202aand203aown a difference in thickness thereof which are capable of absorbing a difference in a thickness between the semiconductor chip4aand the semiconductor chip204b, which is different in thickness from the semiconductor chip204a. As a result, an outer main surface of the high-sided plate201may be made at the same height with respect to the outer main surface of the low-sided plate202. In other words, the outer main surfaces of the high-sided plate201and the low-sided plate202is disposed in a substantially same plane.

In accordance with this arrangement, both the high-sided plate201and the low-sided plate202may be made in close contact with a cooling member through a thinner electric insulating member, for example, on the same plane of the cooling member. Thus, the superior double-sided cooling effect may be achieved with having the simple construction.

In addition, an extra gap can be secured by the spacers202aand203abetween either the high-sided plate201or the low-sided plate202, and the middle-sided plate203, for example, so that a connection member for connecting the control electrode of the semiconductor chip and the control electrode terminal thereof, e.g., an arranging space of the bonding wire may be secured without any design problem.

The respective plates201to203own projected terminal portions210,220,230(seeFIGS. 40 and 41) which are elongated along either front in a depth direction of a plane inFIG. 38or rear in the depth direction thereof. The projected terminal portions210,220,230are connected to external bus bars (not shown).FIG. 40is an exploded diagram for indicating such a semiconductor switching module made before the spacers202aand203aare joined to the semiconductor chips204aand204b.FIG. 41is an oblique perspective figure for showing such a semiconductor switching module made after the spacers202aand203ahave been joined to the semiconductor chips204aand204b.

It should be understood in this embodiment that the control electrode terminals206aare firstly formed with the respective plates201and203in an integral form, and are cut away from these plates201and203after the wire bonding or the resin molding. Since such a manufacturing manner is generally known in the normal lead frame resin molding technique, a detailed explanation thereof is omitted. While five sets of these control electrode terminals206aare illustrated as to a single semiconductor chip in the drawings, these control electrode terminals are constituted by a gate terminal, a drain terminal, a current mirror sense terminal, and two temperature detecting terminals for detecting the temperature of the semiconductor chip. If no sensor such as temperature sensor is required, then only both the gate terminal and the drain terminal may be required in this minimum condition.

It should also be noted that the widths of the respective plates201to203are made wider than those of the spacers202aand203a, and thus, the respective plates201to203are further projected from the peripheral portions of the spacers202aand202boutwardly along the plane direction. As a result, the base portions of the terminals may be joined to the inner main surfaces of the respective plates201to203, and then, may be projected outwardly along the plane direction.

It should also be noted that the respective plates201to203have connecting holes201a,202a, and203afor connecting these plates to bus bars or electrodes and the like of other element or device and the like. Screws and the like are fixed through the connecting holes.

The bonding wires207aand207bare used to connect bonding pads with the control electrode terminal206a. These bonding pads may constitute control electrodes of the semiconductor chips204aand204b. The control electrode terminal206ais projected outwardly along the plane direction.

The sealing resin portion208may be, for example, an epoxy molding resin, and may mold both the semiconductor chips204aand204b. While the sealing resin portion208covers the side surfaces of the respective plates201to203and also covers the side surfaces of the semiconductor chips204aand204b, the outer main surfaces209,211and212of the respective plates201,202and203are exposed, and an edge portion of the sealing resin portion208along the thickness direction thereof is limited to inner sides rather than the outer main surfaces209to212. As a consequence, the outer main surfaces209to212can be readily made in close contact with a flat surface of a cooling member.

The soldering layer205may be replaced with a solder material, an electrically conductive adhesive agent and the like. Also, these electrically conductive joint materials may be employed for connecting the spacers202aand203ato the respective plates201to203. Alternatively, the spacers202aand203amay be formed with the respective plates201and203in an integral form.

Apparently, the control electrodes of the semiconductor chips204aand204bmay be connected to the control electrode terminals206aby the bonding wires207aand207bor bump joints.

InFIG. 41, while both the low-sided plate and the high-sided plate are arranged on one main side, other components such as the middle-sided plate and the control electrode are arranged on the opposite side. Alternatively, for instance, both the low-sided plate and the middle-sided plate may be arranged on one side. Also, the position of the low-sided plate may be changed by the position of the middle-sided plate.

In accordance with the arrangement above described, while a double-sided cooling functions of the semiconductor chips (modules) are maintained, the single-phase inverter circuit can be formed in a single inverter module. The single-phase circuit can be made compact and also a total number of assembling steps can be reduced, whereby when the semiconductor module is applied to a vehicle, for example, an anxiety about loosening of fastening portions with respect to vehicle vibrations and others can be mitigated.

Also, since the middle-sided plate (either output electrode bus bar of single-phase inverter circuit or a portion thereof) may constitute a common board of both the semiconductor chips, the high packaging arrangement of both the semiconductor chips can be realized. Moreover, a total number of wiring components can be reduced, a total number of connecting steps can be decreased, and loss occurred in the wiring lines can be reduced.

Modification Mode

A modification mode of the present invention is shown in FIG.42.

In the above-explained embodiment, the semiconductor chips204aand204bare constructed of the MOS transistors. InFIG. 42, an IGBT is employed as these semiconductor chips204aand204b. In the case that an IGBT is employed so as to control switching of an inductive load, a flywheel diode must be cross-coupled to this IGBT. As a result, a semiconductor chip204cin which the flywheel diode is formed is connected parallel between the respective plates201and203, and another semiconductor chip204din which the flywheel is formed is connected parallel between the respective plates202and203.

Also, inFIG. 42, a projected terminal portion230of the middle-sided plate203is extracted along the same direction to the projected terminal portion210of the high-sided plate201and the projected terminal portion220of the low-sided plate202.

Furthermore, in this modification, the control electrode terminal206ais projected to a side opposite to the projected terminal portions210,220, and230of the respective plates201to203. As a result, the wiring lines can be easily detoured, and the electric insulation can be easily made between the terminals and the wiring lines. Entering of the switching noise into the control electrode terminal206acan be reduced.

InFIG. 42, the semiconductor chip is constituted by both a transistor chip and a flywheel diode chip, which are interposed in a parallel manner between one of the high-sided plate201and the low-sided plate202and the middle-sided plate203, while being separated from each other.

In accordance with this construction, each of the semiconductor chips owns such a two-chip structure that one of an IGBT (insulated-gate bipolar transistor), an MOST (insulated-gate transistor) and a BPT (bipolar transistor), for example, and a flywheel diode are connected in a parallel manner, so that a compact single-phase large current inverter circuit having the superior cooling characteristic can be realized.

It should be noted that since a thickness of either an IGBT chip or a BPT chip is normally different from a thickness of a flywheel diode chip, a difference in thickness between these chips may be solved by interposing one pair of spacers having a difference in thickness between the high-sided plate201and the middle-sided plate203, and also between the low-sided plate202and the middle-sided plate203, respectively.

Incidentally, the spacers202aand203amay also own projected terminal portions elongated from the sealing resin portion208along a direction substantially equal to a plane direction instead of the terminal210,220or230.

According to this arrangement, since the spacers are projected from the sealing resin portions along the plane direction so as to constitute the terminals, the simple terminal structures having high reliability can be realized.

Moreover, main electrode terminals may be joined to inner main surfaces of the high-sided plate201, the low-sided plate202, and the middle-sided plate203, and also are projected outside along the plane direction instead of the terminal210,220or230formed in the respective plates201,202and203.

With employment of such a structure, for instance, low-cost terminals having very low resistance values, made of copper and the like, can be employed as compared with electric resistance values of Mo and W.

Furthermore, it is preferably that a metal material having a coefficient of linear expansion approximately equal to that of the semiconductor chip is employed as the spacers and the middle-sided plate and the. The shape of this metal material may be easily processed, and also both the material cost and the shape-processing cost may be reduced.

Structure of Semiconductor Device)

A semiconductor device with employment of this semiconductor switching module is indicated in FIG.39.

Reference numerals221and221show cooling members corresponding to heat radiation fins. Reference numeral233shows an insulating material, and reference numeral234represents a silicon grease layer.

The insulating material233is made in close contact with the outer main surfaces209and211of the respective plates201and202. A silicon grease layer may be coated or interposed between both the outer main surfaces209and211. The cooling member221is made in close contact with flat contact planes of the cooling members221and221through the silicone grease layer234. A large number of concave/convex portions, namely fin are formed on the outer main surfaces of the plates201and202.

InFIG. 39, through holes are formed in both a right edge portion and a left edge portion of the cooling members221and221. A through bolt231is inserted into these through holes, and a nut232is screwed to the through bolt231, so that the semiconductor switching module is pinched by one pair of these cooling members221and221. In other words, in accordance with this embodiment, these cooling members221and221may work not only the cooling member but a force-transferring member so that the pinching force produced by the bolt and the nut is transferred to the contact planes in order that the cooling members221and221can be made in close contact with the semiconductor switching module under better condition. Alternatively, these heat-radiating members221and221may be replaced by, for instance, the coolant tube as described above embodiments.

FIG. 39represents such a condition that the cooling members221and221pinch only one phase of the semiconductor switching module in the three-phase inverter system (namely, single-phase inverter circuit). Alternatively, these cooling members221and221may sandwich the other two phases of the semiconductor switching modules at the same time toward the rear depth direction of the plane in FIG.38.

Seventeenth Embodiment

Referring now toFIG. 43, a description will be made of a semiconductor switching module according to another embodiment, and also a semiconductor device for constituting a 3-phase inverter circuit with employment of this switching module.FIG. 43is a plan view for indicating a major portion of this semiconductor device.

In this embodiment,FIG. 43shows a plan view of a semiconductor switching module300containing the 3-phase inverter circuit in which three sets of the single-phase inverter circuit shown inFIG. 42are integrated inside the sealing resin portion208.

Also, in this embodiment, while the semiconductor switching module300is pinched by the cooling members221and221shown inFIG. 39from both sides thereof, a semiconductor device which constitutes an one module of a 3-phase inverter circuit may be realized.

It should be noted that symbol203U shows a middle-sided plate for a U-phase, symbol203V indicates a middle-sided plate for a V-phase, and symbol203W represents a middle-sided plate for a W-phase, which are arranged in parallel to each other. One edge of each of these middle-sided plates constitutes a projected terminal portion30U,30V, or30W, respectively.

While the semiconductor chips204aand4bin which the IGBT is formed, respectively, the semiconductor chips204cand204din which the flywheel diode is formed, respectively. The respective flywheel diodes are cross-coupled to the respective IGBTs similar to the above-mentioned semiconductor switching module.

Although a control electrode terminal is not shown in this drawing, the control electrode terminal may be formed by way of a so-called “lead frame manufacturing process.”

Namely, the three-phase semiconductor switching module has a high-sided semiconductor chip in which a high-sided semiconductor switching element is formed, and a low-sided semiconductor chip in which a low-sided semiconductor switching element is formed. The three-phase semiconductor switching module is also arranged by connecting three sets of a single-phase inverter circuit in a parallel manner. The single-phase inverter circuit is arranged by series-connecting both the semiconductor switching elements.

The three-phase semiconductor switching module comprises of a high-sided plate and a low-sided plate, which are made of metal plates respectively, and also middle-sided plates of a U-phase, a V-phase, and a W-phase;

Main electrode surfaces of both the semiconductor chips for the U-phase on the output sides thereof are directly joined, or joined via electrically conductive members to an inner main surface of the middle-sided plate for the U-phase, while the main electrode surfaces thereof are separated from each other.

Main electrode surfaces of both the semiconductor chips for the V-phase on the output sides thereof are directly joined, or joined via electrically conductive members to an inner main surface of the middle-sided plate for the V-phase, while the main electrode surfaces thereof are separated from each other.

Main electrode surfaces of both the semiconductor chips for the W-phase on the output sides thereof are directly joined, or joined via electrically conductive members to an inner main surface of the middle-sided plate for the W-phase, while the main electrode surfaces thereof are separated from each other.

A main electrode surface of the high-sided semiconductor chip for each phase on the side of a high potential power supply is directly joined, or joined via an electrically conductive member to an inner main surface of the high-sided plate.

A main electrode surface of the low-sided semiconductor chip for each phase on the side of a low potential power supply is directly joined, or joined via an electrically conductive member to an inner main surface of the low-sided plate.

Both the semiconductor chips are covered in an integral form by a sealing resin portion, which is molded, while exposing outer main surfaces of the middle-sided plate for each phase, the high-sided plate for each phase, and the low-sided plate for each phase.

In accordance with this arrangement, the three-phase inverter circuit is built in the semiconductor switching module, while employing five bus-bar-shaped members in total, namely the high-sided plate, the three middle-sided plate, and the low-sided plate. Furthermore, it is possible to realize such a module that the respective semiconductor chips are arranged in a matrix shape in a constant interval. Therefore, the arrangement of the semiconductor switching module can be considerably simplified, and also can output high power by cooling both surfaces thereof, while this semiconductor switching module can be made compact.

Other Embodiments

Embodiments explained below show semiconductor devices for large electric power, which are easily manufactured so as to be excellent in practical property, and have an excellent heat radiating characteristics.

Preferred modes of the present invention will be explained with reference to the following embodiments.

Eighteenth Embodiment

Entire Construction

FIG. 44is a circuit diagram of a three-phase inverter circuit device for controlling an operation of a driving motor of an electric automobile.

Reference numeral221designates a battery (direct current power source). Each of reference numerals222to227designates a semiconductor element constructed by an NMOS transistor utilizing a parasitic diode as a flywheel diode.

The semiconductor element222constitutes a U-phase upper arm, and the semiconductor element223constitutes a U-phase lower arm. The semiconductor element224constitutes a V-phase upper arm, and the semiconductor element225constitutes a V-phase lower arm. The semiconductor element26constitutes a W-phase upper arm, and the semiconductor element227designates a W-phase lower arm. These semiconductor elements are individually mounted as semiconductor modules150to650, respectively.

Reference numerals151and152respectively designate a positive direct current power source terminal (drain side) of the U-phase upper (high side) arm, and an alternating current output terminal (source side) of the U-phase upper arm. Reference numerals251and252respectively designate an alternating current output terminal (drain side) of the U-phase lower (low side) arm, and a negative direct current terminal (source side) of the U-phase lower arm.

Reference numerals351and352respectively designate a positive direct current power source terminal (drain side) of the V-phase upper (high side) arm, and an alternating current output terminal (source side) of the V-phase upper arm. Reference numerals451and452respectively designate an alternating current output terminal (drain side) of the V-phase lower (low side) arm, and a negative direct current terminal (source side) of the V-phase lower arm.

Reference numerals551and552respectively designate a positive direct current power source terminal (drain side) of the W-phase upper (high side) arm, and an alternating current output terminal (source side) of the W-phase upper arm. Reference numerals651and652respectively designate an alternating current output terminal (drain side) of the W-phase lower (low side) arm, and a negative direct current terminal (source side) of the W-phase lower arm.

Each of the positive direct current power source terminals151,351,551is connected to a positive electrode terminal of a smoothing capacitor228and a positive electrode terminal of the battery221. Each of the negative direct current power source terminals252,452,652is connected to a negative electrode terminal of the smoothing capacitor228and a negative electrode terminal of the battery221. The U-phase alternating current output terminals152,251are connected to each other at a connection point153. The V-phase alternating current output terminals352,451are connected to each other at a connection point353. The W-phase alternating current output terminals552,651are connected to each other at a connection point553. Thus, electric power is supplied to a armature winding (not shown) of a three-phase alternating current motor229.

A controller130outputs a control voltage to a gate electrode of each semiconductor element, and detects a temperature of each semiconductor element, etc. Operations of the above three-phase inverter circuit and the smoothing capacitor228are well known. Accordingly, a detailed explanation of these operations is omitted here.

Semiconductor Module

A semiconductor module150of the U-phase upper arm will next be explained with reference toFIGS. 45A and 45B.FIGS. 45A and 45Brespectively show an exploded perspective view of this semiconductor module and a perspective view of the entire semiconductor module.

Reference numerals155,156and158respectively designate a metallic heat transfer plate having the positive direct current power source terminal151, a metallic heat transfer plate having the alternating current output terminal152, and a signal terminal (also called a control electrode terminal) of the semiconductor element (a semiconductor element chip for large electric power)222. The signal terminal158includes a terminal for controlling the operation of a gate electrode of an NMOS transistor, and a signal terminal for an internal monitor of the semiconductor element222. Five signal terminals158are arranged in each ofFIGS. 45A and 45B.

The semiconductor element222is soldered onto the metallic heat transfer plate155, and the metallic heat transfer156is soldered onto an upper face of the semiconductor element222. These metallic heat transfer plates are sealed by resin159in a state in which external main faces of the metallic heat transfer plates155,156are exposed and terminals151,152,158are projected. These members constitute the semiconductor module150.

In this embodiment, the signal terminal158and the positive direct current power source terminal (also called a drain electrode terminal)151are particularly arranged on the same side (particularly, a long side) of the rectangular semiconductor module150. The signal terminal158is arranged on a half side of this long side, and the positive direct current power source terminal (drain electrode terminal)101is arranged on the other half side of this long side as shown in FIG.45B. The alternating current output terminal (also called a source electrode terminal)152is arranged in a half portion on a side opposed to the side from which terminals158,151are projected. Namely, the alternating current output terminal152is projected in a direction opposite to the signal terminal158.

Here, heat resistance from a junction portion of the semiconductor element (NMOS transistor)222to the metallic heat transfer plate155on a drain side in the semiconductor module150is set to R1. Heat resistance from the junction portion of the semiconductor element222to the metallic heat transfer plate156on a source side is set to R2. If thickness of both the metallic heat transfer plates155,156are set to be equal to each other, a relation between R1and R2becomes “R1<R2”.

The reasons are as follows. A main face of the semiconductor element222disposed on its drain area side is joined to the metallic heat transfer plate105over an entire face of this main face. In contrast to this, with respect to a main face of the semiconductor element222disposed on its source area side, it is necessary to project one portion of the metallic heat transfer plate156disposed on a source side toward the semiconductor element222so as to secure a three-dimensional space for connection with each signal terminal158using wiring bonding and avoid this three-dimensional space. Therefore, only the remaining portion obtained by subtracting the above three-dimensional space from the main face of the semiconductor element222disposed on its source area side can be joined to the metallic heat transfer plate156. Therefore, the above-mentioned heat resistance relation is formed.

The semiconductor modules350,550of the other upper arms have the same construction as the semiconductor module150. The semiconductor modules250,450,650of the lower arms also have the same construction as the semiconductor modules150,350,550of the upper arms. In this case, the positive direct current power source terminal of the semiconductor module of the upper arm is replaced with an alternating current output terminal in the semiconductor module of the lower arm, and the alternating current output terminal of the semiconductor module of the upper arm is replaced with a negative direct current power source terminal in the semiconductor module of the lower arm.

When an IGBT is adopted as the semiconductor module222, a separate flywheel diode is required. However, the flywheel diode may be arranged on a left-hand side of the semiconductor element222in FIG.45A. In this case, the flywheel diode is mounted in a shape in which a cathode side of the flywheel diode is directed to the metallic heat transfer plate155having the positive direct current power source terminal151.

Semiconductor Module

Reference numerals255,256,258and259respectively designate a metallic heat transfer plate having the alternating current output terminal251, a metallic heat transfer plate having the negative direct current power source terminal252, a control electrode terminal of the semiconductor element223, and mold resin.

FIGS. 47 and 48show an inverter device using the semiconductor module250.FIG. 48shows a side view of this inverter device.FIG. 47is a partial plan view of a U-phase portion, andFIG. 48is a side view seen from an arrow XXXXVIII of FIG.47.

A heat sink110is constructed by a metallic plate of a water cooling structure forming a cooling flow path therein. For example, the heat sink110is formed by an aluminum die-cast method. The heat sink110is not limited to water cooling. For example, the heat sink110may be constructed by a flat tube formed by extrusion or drawing of aluminum (Al) having strength and an airtight (sealing) property able to seal a refrigerant of an air conditioner for an automobile and the like, and may be also constructed by a well-known refrigerant reservoir of a boiling-cooling type.

Each of reference numerals150,250designates a semiconductor module (hereinafter, also called a card type semiconductor module). Reference numeral112designates a fixing member (a biasing-holding member in the present invention). A pair of fixing members112is detachably fixed to the heat sink110by screws113from above the semiconductor modules150,250. The fixing members112individually press the semiconductor modules150,250against an upper face of the heat sink110.

A smoothing capacitor228is adjacent to the semiconductor modules50,250, and is fixed onto the heat sink110in a posture in which a bottom face of the smoothing capacitor228comes in contact with the heat sink. Reference numerals111+ and111− respectively designate a positive direct current input bus bar and a negative direct current input bus bar which are also respectively the direct current input terminals151,251of the semiconductor modules150and250, and positive and negative electrodes of the smoothing capacitor228.

An insulator1111is interposed to electrically insulate the positive and negative direct current input bus bars111+,111−. Reference numeral121designates an alternating current output bus bar of the U-phase connecting the alternating current output terminals152,251of the semiconductor modules150,250and the three-phase alternating current motor229. Constructions with respect to the V-phase and the W-phase are similar to the construction with respect to the U-phase. Accordingly, an explanation of these constructions are omitted here.

The controller130is arranged in parallel with the heat sink110above the semiconductor modules150,250although this arrangement is not illustrated here. The controller130is connected to control electrode terminals158,258of the respective semiconductor modules150,250, etc.

A member having a heat conducting property and an electric insulation performance, e.g., an insulation heat radiating sheet of a silicone system is nipped on a contact face115of each of the semiconductor modules150,250and the heat sink110, and a contact face116of each of the semiconductor modules150,250and the fixing member112. However, this insulation heat radiating sheet can be replaced with an insulating substrate such as ceramics, etc., and heat radiating grease on both faces of this insulating substrate. A heat radiating sheet of a silicone system having a good heat conducting property and a heat conducting grease, etc. are also interposed on a contact face117of the fixing member112and the heat sink110. If the fixing member is an insulating member such as resin, etc., no electric insulating property is required in the heat conducting members nipped on the contact faces116and117.

In accordance with the above embodiment, the semiconductor module150is stably held in the heat sink110without using solder joining. Accordingly, it is not necessary to consider life of solder, so that life of the entire semiconductor device can be extended. Since no solder joining is used, it is not necessary to use an expensive material such as Al—SiC, etc. in the heat sink110so that cost of the entire semiconductor device can be reduced.

Further, the semiconductor device can be assembled by a simple manufacture arrangement irrespective of large heat capacity of the heat sink110. Since the semiconductor device is constructed so as to be mechanically detached, the semiconductor device is excellent in recycle property and is easily exchanged.

Further, heat can be radiated from both faces of the semiconductor element within the semiconductor module to the heat sink110by applying the fixing member112made by a metallic material having a good heat conducting property, e.g., Cu and aluminum. Accordingly, heat radiating performance can be greatly improved in comparison with a case in which heat is radiated from one face of the semiconductor element. As a result, the semiconductor element can be made compact so that the semiconductor device can be made compact and reduced in cost. One fixing member112may be prepared every semiconductor module, and a lot of semiconductor modules may be also fixed by one fixing member.

Fixing Member

The fixing member112will be further explained with reference to FIG.49.FIG. 49is a side view of a main portion of this device.

The fixing member112has a beam portion1121for pressing and biasing the semiconductor module, and a pair of leg portions1122projected from both ends of the beam portion1121to a side of the heat sink110. A hole (not shown) extends through each of both the leg portions1122in a thickness direction of the semiconductor module150. The fixing member112is fixed to the heat sink110by fastening a screw113to the heat sink110through this hole. The semiconductor module150is nipped and pressed by the heat sink110and the beam portion1121of the fixing member112.

An insulation heat conducting member120is arranged between a metallic heat radiating plate (not shown) of the semiconductor module150disposed on its heat sink side and an upper face of the heat sink110. The insulation heat conducting member120is also arranged between a metallic heat radiating plate (not shown) of the semiconductor module150disposed on a side opposed to the heat sink and a lower face of the beam portion1121of the fixing member112. A heat conducting member122is arranged between a lower face of the leg portion1122of the fixing member112and the upper face of the heat sink110.

In this embodiment, the heat conducting member122is constructed by a soft material having a good heat conducting property, and is softer than the insulation heat conducting member120.

In such a construction, when the fixing member120is fastened to the heat sink110by the screw113, the semiconductor module150can be strongly pressed against the heat sink110by the hard heat conducting member120. Accordingly, heat can be preferably radiated from a lower side face of the semiconductor module150to the heat sink110. A material softer than the insulation heat conducting member120is used in the heat conducting member122so that the insulation heat conducting member120fully fits the lower face of the leg portion1122and the upper face of the heat sink110, and heat resistance can be reduced.

For example, aluminum nitride and a hard silicone rubber sheet can be adopted as the insulation heat conducting member120. For example, solder, heat conducting grease and a graphite sheet can be adopted as the heat conducting member122. A material having an electric insulating property, e.g., a silicone rubber sheet having low hardness may be also adopted as the heat conducting member122. The screw113may be manufactured by a metal, and may be also manufactured by resin having an electric insulating property.

Modified Mode

In the above embodiment, the insulation heat conducting member120is nipped between the semiconductor module150and the beam portion1121of the fixing member112. However, the heat conducting member122may be changed to an insulation heat conducting member having an electric insulating property, and,the insulation heat conducting member120may be also set to a conducting member having an electric conducting property. The semiconductor module150and the beam portion1121of the fixing member112may come in direct contact with each other. Resin is used in the screw113. In such a construction, the fixing member112can be used as a wiring member or a terminal connected to the metallic heat radiating plate of the semiconductor module150on a side opposed to the heat sink.

Nineteenth Embodiment

Another embodiment will next be explained with reference to FIG.49.

In this embodiment, an average coefficient km 1 of thermal expansion of the leg portion1122of the fixing member112and the heat conducting member122is set to be in conformity (within an error of 1%) with an average coefficient km 2 of thermal expansion of the semiconductor module150and two insulation heat conducting members120between a pair of metallic heat radiating faces. In this specification, an average coefficient km of thermal expansion of plural members A, B is set to be prescribed by the following formula.

Here, k1is a coefficient of thermal expansion (a coefficient of linear expansion) of the member A, t1is a thickness of the member A, k2is a coefficient of thermal expansion (a coefficient of linear expansion) of the member B, and t2is a thickness of the member B.

In such a construction, it is possible to dissolve thermal stress caused by the difference in coefficient of thermal expansion between the semiconductor module150and the leg portion1122so that reliability with the passage of time can be improved. The above difference in coefficient of thermal expansion is allowed if this difference lies in a range in which this difference has no bad influence on each portion of the semiconductor module at a maximum using temperature or a minimum using temperature.

Modified Mode

In conformity setting of this average coefficient of thermal expansion, temperatures of the leg portion1122of the fixing member112, the heat conducting member122, the semiconductor module150and the two insulation heat conducting members120are respectively different from each other. Therefore, expansion amounts of these members, etc. in their thickness directions are different from each other.

A material of the leg portion1122, etc. can be selected to compensate the difference in expansion amount due to the difference in temperature between these respective parts such that a total expansion amount of the leg portion1122of the above fixing member112and the heat conducting member122in the thickness direction is conformed to that of the semiconductor module150and the two insulation heat conducting members120in the thickness direction at the maximum using temperature at which the expansion amount is maximized. Further, the material of the leg portion1122, etc. can be selected such that the above difference in expansion amount lies in an allowable range at each using temperature of the semiconductor module100.

Twentieth Embodiment

Another embodiment will next be explained with reference to FIG.50.

In this embodiment, a main cooling fluid passage M is formed within the heat sink110, and a cooling fluid flows through this passage M. A sub-cooling fluid passage S is also formed in the fixing member112. Both end openings of the sub-cooling fluid passage S of the fixing member112are communicated with the main cooling fluid passage M of the heat sink110. Both the passages M, S are substantially connected in series or parallel to each other. Thus, the semiconductor module150can be further preferably cooled.

Reference numeral360designates a packing. This packing360can also have a function for elastically absorbing thermal stress due to the difference in coefficient of thermal expansion between the fixing member112and the semiconductor module100in the thickness direction of the semiconductor module100. Reference numeral120designates an insulation heat conducting member for electrically insulating the metallic heat radiating plate of the semiconductor module150, the heat sink110and the fixing member112.

In this embodiment, the cooling fluid flows through the fixing member, but the fixing member may be constructed by a heat pipe and may be fixed to the heat sink.

Another embodiment will next be explained with reference to FIG.51.

In this embodiment, other circuit parts (a smoothing capacitor in this embodiment) are overlapped and arranged on the semiconductor modules150,250through bus bars161,262. The fixing member112presses the semiconductor modules150,250against the heat sink110through the smoothing capacitor228.

In such a construction, circuit mounting density can be improved. Further, it is possible to shorten the wiring distance between the semiconductor module150constituting an inverter circuit and the smoothing capacitor228absorbing a switching serge voltage between a pair of direct current terminals of this semiconductor module150. Accordingly, electric power loss and generated loss due to wiring resistance can be reduced. The smoothing capacitor228and the bus bars161,262can have a heat sink function of the semiconductor module150. In other words, the bus bars151and252serve like the metallic heat transfer plate155and the metallic heat transfer plate256.

The metallic heat radiating plate of each of the semiconductor modules150,250on a side opposed to the heat sink constitutes a + or − direct current terminal of the inverter circuit. The metallic heat radiating plate (not shown) of each of the semiconductor modules150,250on a heat sink side constitutes an alternating current output terminal. The two semiconductor modules150,250are nipped and pressed by one fixing member112.

Each of the bus bars161,262has a concave portion c into which each of a + direct current terminal281and a − input terminal282of the smoothing capacitor228is fitted. Thus, a transversal shift of the smoothing capacitor228can be prevented, and a position of the smoothing capacitor is easily aligned at its mounting time. A side face of this concave portion c is set to a taper face having a gradually narrowed bottom so that both direct current terminals281,282of the smoothing capacitor228are easily fitted and aligned in position. The smoothing capacitor228can have plural + direct current terminals281and plural − direct current terminals282. In this case, a plurality of said concave portions fitted to these terminals are arranged.

Modified Mode

In this embodiment, a material of the leg portion1122, etc. are selected such that an average expansion coefficient km 3 of the semiconductor modules150,250, the smoothing capacitor228and the bus bars161,262in the thickness direction of the semiconductor module150is conformed to an average expansion coefficient km 4 of the leg portion1122of the fixing member112in its thickness direction.

Similarly to the above formula, each of the average expansion coefficients km 3, km 4 is defined as a value obtained by dividing a total expansion amount per rise in unit temperature of plural constructional members by a total distance of these plural members in their thickness directions. Otherwise, similarly to the above modified mode, while the actual expansion amount of each portion in its thickness direction is set by considering a temperature distribution at a predetermined temperature (normally a maximum using temperature) of the semiconductor modules150,250, the expansion amounts in the thickness direction on both of the leg portion1122and the semiconductor modules150,250may be set to be in conformity with each other. In any case, the problem of thermal stress as a serious problem in a fixing system of the pinching semiconductor module of this construction can be solved at a practical level.

Another embodiment will next be explained with reference to FIG.51.

In this embodiment, the bus bars161,262are set to metallic heat radiating plates of the semiconductor module150on a side opposed to the heat sink in a two-story circuit structure of the twenty-first embodiment shown in FIG.51. Accordingly, in this embodiment, the metallic heat radiating plates161,262of the semiconductor modules150,250on the side opposed to the heat sink respectively have concave portions c into which a + direct current terminal281and a − minus input terminal282of the smoothing capacitor228are fitted. Thus, a transversal shift of the smoothing capacitor228can be prevented, and a position of the smoothing capacitor is easily aligned at its mounting time. The other effects are the same as the twenty-first embodiment.

Modified Mode

In this embodiment, the material of the leg portion1122, etc. are selected such that an average expansion coefficient km 5 of the semiconductor modules150,250and the smoothing capacitor228in the thickness direction of the semiconductor module150is conformed to an average expansion coefficient km 6 of the leg portion1122of the fixing member112in its thickness direction. The average expansion coefficients km 5, km 6 are calculated by the above formula although explanations of these calculations are omitted. Similarly to the above modified mode, while the actual expansion amount of each portion in its thickness direction is set by considering a temperature distribution at a predetermined temperature (normally a maximum using temperature) of the semiconductor modules150,250, the expansion amounts in the thickness direction on both of the leg portion1122and the semiconductor modules150,250may be also conformed to each other. In any case, the problem of thermal stress as a serious problem in a fixing system of the pinching semiconductor module of this construction can be solved at a practical level.

Another embodiment will next be explained with reference to FIG.52.

In this embodiment, the fixing member112has an elastic deforming portion1123having a curving shape in which a beam portion1121particularly has a large elastic modulus toward the thickness direction of the semiconductor module150. In such a construction, it is possible to greatly reduce the thermal stress caused by the difference in coefficient of thermal expansion already described between the semiconductor module150and the leg portion1122in the thickness direction of the semiconductor module150.

Another embodiment will next be explained with reference to FIG.53.

In this embodiment, the heat sink110has a pair of side wall portions111projected on both sides of the semiconductor module150, and the fixing member112is formed by a metallic thin plate. Both end portions of the fixing member112are fixed to the side wall portions by screws113manufactured by resin.

In accordance with this construction, the fixing member112can be easily elastically deformed in the thickness direction of the semiconductor module150so that the above thermal stress can be preferably absorbed. Further, the heat radiating distance between the heat sink110and a metallic heat radiating plate of the semiconductor module150on a side opposed to the heat sink is shortened. Accordingly, a reduction in heat radiating property can be restrained although the fixing member112is made thin.

Another embodiment will next be explained with reference to FIG.54.

In this embodiment, the metallic heat radiating plate156of the semiconductor module150on a side opposed to the heat sink has an irregular portion1061fitted to an irregular portion11211of a beam portion1121of the fixing member112. A metallic heat radiating plate (not shown) of the semiconductor module100on a heat sink side and a leg portion1122of the fixing member112respectively come in close contact with the heat sink110through insulation heat conducting members having an electric insulating property. A screw113is manufactured by resin. A side face of the irregular portion is set to a taper face so as to easily fit and position the irregular portion. Thus, the fixing member112is easily positioned with respect to the semiconductor module150so that a transversal shift of the semiconductor module150can be prevented, and the heat resistance between the semiconductor module150and the fixing member112can be reduced. The fixing member112can be also used as a terminal of the metallic heat radiating plate156of the semiconductor module150on the side opposed to the heat sink.

This irregular fitting structure can be also used in contact of the metallic heat radiating plate of the semiconductor module150on the heat sink side and the heat sink110. However, in this case, the metallic heat radiating plate of the semiconductor module150on the heat sink side is preferably set to have the same electric potential (normally ground electric potential) as the heat sink.

Another embodiment will next be explained with reference to FIG.55.

In this embodiment, the heat sink110has a stopper1101coming in contact with a resin mold portion159of the semiconductor module150and regulating a transversal shift of the semiconductor module150. Thus, no semiconductor module is transversally shifted from the heat sink or a biasing-holding member even in a high vibration environment such as an electric automobile so that reliability can be improved. Since a side face of this stopper1101is set to a taper face (slanting face), the semiconductor module150is easily positioned.

Modified Mode

In the above modified mode, the stopper is arranged in the heat sink110, but may be also arranged in the fixing member112so as to prevent the transversal shift of the semiconductor module150. In this case, the semiconductor module150is easily positioned by setting the side face of the stopper to a taper face (slanting face).

Another embodiment of the inverter device of the present invention will be explained with reference toFIGS. 56 and 57.FIG. 56is a partial plan view of a U-phase portion.FIG. 57is a side view seen from an arrow LVII of FIG.56.

The heat sink110is constructed by a metallic plate of a water cooling structure forming a cooling flow path therein. For example, the heat sink1101is formed by a die-cast method. Reference numeral150designates a card type semiconductor module. The structure of the card type semiconductor module150is already explained in the eighteenth embodiment.

The card type semiconductor module (also called a semiconductor module)150is detachably fixed by fastening a screw113from above the fixing member (biasing-holding member)112. The fixing member (biasing-holding member)112presses the semiconductor module150against an upper face of the heat sink110. A semiconductor module250of a lower arm has the same construction as the semiconductor module150. Similarly to the semiconductor module150, the semiconductor module250is fixed so as to be pressed against the heat sink110in a state in which the semiconductor module250is horizontally rotated 180 degrees with respect to the semiconductor module150in FIG.56.

A smoothing capacitor228is adjacent to the semiconductor modules150,250and is fixed such that a bottom face of the smoothing capacitor228comes in contact with the heat sink110. A positive direct current input bus bar111+ and a negative direct current input bus bar111− respectively connect direct current input terminals151,252of the semiconductor modules150and250, and positive and negative electrodes of the smoothing capacitor228. An insulator1111nips the positive and negative direct current input bus bars111+ and111− so as to electrically insulate these bus bars from each other. An alternating current output bus bar121of the U-phase connects alternating current output terminals152,251of the semiconductor modules150,250and a three-phase alternating current motor229. Constructions with respect to the V-phase and the W-phase are similar to the construction of the U-phase. Accordingly, an explanation of these constructions is omitted here.

A controller130is arranged approximately in parallel with the heat sink above the semiconductor module although this arrangement is not illustrated here. The controller130is connected to signal electrodes158,258of the respective semiconductor modules, etc.

A member having a heat conducting property and an electrical insulative property, e.g., a heat radiating sheet of a silicone system is pinched between the heat sink110and each of the semiconductor modules150,250at a contact face115and between the biasing-holding member112and each of the semiconductor modules150,250at a contact face116. A member having a good heat conducting property, e.g., a heat radiating sheet of a silicone system, grease, etc. are nipped on a contact face117of the biasing-holding member112and the heat sink110. If the biasing-holding member is an insulating member such as resin having a good heat conducting property, etc., no electric insulating property is required in the heat conducting member nipped on the contact face116. A member having a good heat conducting property may be also similarly nipped on the bottom face of a capacitor and a contact face of the heat sink.

FIG. 56shows only the U-phase, but a three-phase inverter can be simply constructed by arranging similar constructions with respect to the V-phase and W-phase in parallel with each other on a side of FIG.56.

The other constructions are the same as the eighteenth embodiment. In accordance with this embodiment, the following operational effects can be obtained.

First, semiconductor modules150to650are mounted to the heat sink110in a posture in which a main face of the semiconductor modules150to650on a drain area side having small heat resistance among two main faces of these semiconductor modules is pressed against the heat sink110having high cooling performance. Therefore, heat radiating property is improved, and the cooling property of a semiconductor element can be further improved.

Next, as shown inFIGS. 45B and 56, the drain electrode terminal (positive direct current power source terminal)151of the semiconductor module150is arranged approximately with rotation symmetry with respect to the source electrode terminal (alternating current output terminal)152of the semiconductor module150. In other words, the drain electrode terminal151is arranged at a half portion of one of two longitudinal sides parallel to each other in a rectangular shape of the semiconductor module150, which is positioned in a diagonal direction to a portion of the other of two longitudinal sides in which the source electrode terminal152is formed. Namely, the drain electrode terminal151is disposed on the one of the two longitudinal sides parallel to each other, while the source electrode terminal152is disposed on the other of two longitudinal sides. Additionally, the drain electrode terminal151and the source electrode terminal152are shifted from each other in a direction parallel to the two longitudinal sides.

The signal terminal158is arranged at another half of the one of the longitudinal sides parallel each other described above (another half portion on a side at which the drain electrode terminal101is formed in FIG.45B). Accordingly, switching elements of six arms of the three-phase inverter can be reasonably arranged at high density by one kind of card module so that the inverter can be made compact.

Such a construction will be explained further in detail with reference to FIG.56. The semiconductor module150of an upper arm of the U-phase and the semiconductor module250of a lower arm can be obtained by rotating the semiconductor module250180 degrees on the same plane with respect to the semiconductor module150and setting the semiconductor module250to be adjacent to the semiconductor module150.

The source terminal152is projected from the semiconductor module150in a lower half inFIG. 56along a pair of long sides opposing and parallel to each other of the semiconductor modules150and250. Similarly, the source terminal252is projected from the semiconductor module250in an upper half in FIG.56. Since these terminals152,252are not overlapped, the distance between both the semiconductor modules150,250can be shortened so that high density mounting can be performed. These terminals have the same construction with respect to a pair of semiconductor modules350and450and a pair of semiconductor modules550and650in the other phases.

The positive direct current input bus bar111+ and the negative direct current input bus bar111− can be mutually overlapped and extended until the positive direct current power source terminal151and the negative direct current power source terminal152of the semiconductor module150. Accordingly, the wiring inductance occurred between both the bus bars111+ and111− can be reduced by mutual induction effects. As a result, a serge voltage superposed on the bus bars111+ and111− can be reduced in accordance with switching of semiconductor elements222,223.

Next, in this embodiment, as shown inFIG. 58, a water cooling flow path160is arranged within the heat sink110. Reference numeral120designates a good heat conducting member of e.g., a silicon system having a high electric insulating property. A columnar projecting portion1123is projected from a tip of the leg portion1122of the biasing-holding member112. The projecting portion1123is pressed and fitted into a hole reaching the water cooling flow path160, which is opened to an upper face of the heat sink110.

Cooling water of the water cooling flow path160can preferably cool this projecting portion1123by increasing the length of a tip of the projecting portion1123projected into the water cooling flow path160. As a result, the heat resistance between the heat sink110and the biasing-holding member112can be reduced. The screw113can be also omitted in this figure. However, in this case, the feature of mechanical detachability is lost.

As shown inFIG. 59, the tip of the projecting portion1123may be also set to have a length at which the projecting portion1123is not projected into the water cooling flow path150. In this case, the heat resistance between the heat sink110and the biasing-holding member112is slightly increased in comparison withFIG. 58, but there is an advantage in which possibility of leakage of cooling water from the clearance of a press-fitting portion can be also excluded. Further, a cooling water passage communicated between projecting portions1123on both sides of the biasing-holding member112may be also arranged within the biasing-holding member112. In such an arrangement, the cooling water can flow on both sides of the semiconductor module150so that excellent cooling effects can be realized.