Power semiconductor device and method for manufacturing power semiconductor device

A power semiconductor device includes: a plurality of power modules including control terminals; a heat sink, on which the plurality of power modules are mounted; and a control substrate, to which the control terminals are fixed. The plurality of power modules each include a first protruding portion close to the control terminals, and a second protruding portion far from the control terminals. The heat sink has, at a position corresponding to the first protruding portion, a first recessed portion formed to have an inner diameter larger than an outer diameter of the first protruding portion, and engaged with the first protruding portion. At a position corresponding to the second protruding portion, the heat sink has a second recessed portion formed to have the shape of an elongated hole whose minor diameter is larger than an outer diameter of the second protruding portion, and engaged with the second protruding portion.

TECHNICAL FIELD

The present invention relates to a power semiconductor device including a mechanism for preventing erroneous mounting of a power module, and a method of manufacturing the power semiconductor device.

BACKGROUND ART

In recent years, power semiconductor devices have been beginning to be widely used in automobiles in addition to general industries and railways. An increased ratio of automobiles are being electrified in the forms of, for example, a hybrid vehicle, which uses an engine and a motor both as drive sources, and an electric vehicle, which uses a motor alone as a drive source.

An electrified vehicle is required to be reduced in the size and weight of each part within a limited space in order to help to improve fuel efficiency of the vehicle. A hybrid vehicle is particularly limited in the layout of parts because an engine and a motor are required to share an engine room and a space in which peripheral parts are arranged is consequently small. Accordingly, downsizing of a power semiconductor device increases the degree of freedom in the layout of parts in the small space of the engine room, and leads to the downsizing of the vehicle itself as well. In-vehicle power semiconductor devices are strongly demanded to be downsized for such reasons (see Patent Literature 1, for example).

A trend among in-vehicle power semiconductor devices is to integrate a plurality of types of power converters for the purpose of space saving and cost reduction. For instance, a system using two motors to efficiently manage drive energy and regenerative energy requires two direct current-alternating current conversion circuits in order to drive the two motors separately. The system also requires a step-up converter circuit to obtain a desired system voltage and current through boosting with the use of a step-up converter while keeping an input voltage from a battery low. Those three circuits are accommodated on the same substrate to be used as a function-integrated power semiconductor device.

Constituent parts of a power semiconductor device include a power module, a control substrate, a capacitor, a cooler, and a reactor. Of those listed parts, main parts that determine the size of the power semiconductor device are the power module and the control substrate. When two direct current-alternating current conversion circuits and one step-up converter are mounted on one control substrate, it is preferred to use the same power module in each of the circuits in order to avoid erroneous mounting of the circuits on the control substrate.

The power module type used in this case is required to be the type of the power module in the circuit that has the highest output voltage out of output voltages required of the three circuits. However, this means that a power module larger than required is used in other circuits, and the control substrate is set to an unnecessarily large size as well in order to mount the power module. The control substrate is therefore downsized by using a different power module in each of the three circuits so that the power module is suitable for the output voltage required of the circuit.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, when a different power module is mounted in each of three circuits accommodated on one control substrate, there is a fear that a power module intended for one of the circuits is mounted in another circuit by mistake.

The present invention has been made to solve the problem described above, and an object of the present invention is to provide a power semiconductor device capable of preventing erroneous mounting of a plurality of types of power modules to be mounted on the same control substrate, and a method of manufacturing the power semiconductor device.

Solution to Problem

A power semiconductor device according to one embodiment of the present invention includes: a plurality of power modules, to which control terminals are mounted; a heat sink, on which the plurality of power modules are mounted; and a control substrate having a fixing portion, to which the control terminals are to be fixed, formed thereon. Each of the plurality of power modules each includes a first protruding portion and a second protruding portion. The first protruding portion is formed at a position closer to the control terminals than the second protruding portion is formed. The heat sink has a first recessed portion to be engaged with the first protruding portion at a position corresponding to the first protruding portion when the plurality of types of power modules are mounted. The heat sink further has a second recessed portion to be engaged with the second protruding portion at a position corresponding to the second protruding portion when the plurality of types of power modules are mounted. The first recessed portion is formed to have an inner diameter greater than an outer diameter of the first protruding portion. The second recessed portion is formed to have a shape of an elongated hole having a minor diameter that is greater than an outer diameter of the second protruding portion.

Advantageous Effects of Invention

According to the power semiconductor device of one embodiment of the present invention, erroneous mounting of a power module can be prevented when a plurality of different power modules are mounted on one control substrate.

DESCRIPTION OF EMBODIMENTS

Now, with reference to the drawings, a power semiconductor device according to each of preferred embodiments of the present invention is described.

First Embodiment

FIG.1is a top view of a power semiconductor device1according to a first embodiment of the present invention.FIG.2is a top view of a heat sink60, which is a constituent part of the power semiconductor device1.FIG.3is a sectional view of the power semiconductor device1taken along the line III-III ofFIG.1.FIG.4AtoFIG.4Dare a top view, a front view, a rear view, and a side view, respectively, of a power module10. Similarly,FIG.5AtoFIG.5Dare a top view, a front view, a rear view, and a side view, respectively, of a power module20, andFIG.6AtoFIG.6Dare a top view, a front view, a rear view, and a side view, respectively, of a power module30.

As illustrated inFIG.1, the power semiconductor device1includes one control substrate50, one heat sink60, and a plurality of power modules10,20, and30. The control substrate50is detached inFIG.1in order to make it easier to see the arrangement of the power modules10,20, and30.

As illustrated inFIG.1, three circuits, namely, a direct current-alternating current conversion circuit50a, a direct current-alternating current conversion circuit50b, and a step-up converter circuit50c, are formed on amounting surface of the control substrate50. The direct current-alternating current conversion circuit50aserves as a motor drive circuit to which the power modules are connected. The direct current-alternating current conversion circuit50bserves as a motor drive circuit to which the power modules20are connected. The power modules30are connected to the step-up converter circuit50c. The control substrate50also has a plurality of mounting holes40, to which control terminals11,21, and31of the power modules10,20, and30, respectively, are fixed.

The heat sink60is divided into three areas, namely, areas A to C as indicated by the dash-dot-dot lines inFIG.2. The area A is an area in which six power modules10are mounted. The area B is an area in which four power modules20are mounted. The area C is an area in which six power modules30are mounted. Recessed portions60aand60b, recessed portions60cand60d, and recessed portions60eand60ffor positioning the power modules10,20, and30, respectively, are formed in the areas A, B, and C, respectively.

The recessed portions60a,60c, and60eare formed to have a cylindrical shape, and the recessed portions60b,60d, and60fare shaped as elongated holes each shaped by connecting two semicircles to each other by two straight lines. The recessed portions60b,60d, and60fare formed to have the elongated hole shape in order to deal with dimensional changes caused by thermal expansion of the heat sink60or the power modules10,20, and30, and dimensional fluctuations of the heat sink60or the power modules10,20, and30due to a manufacturing error.

The heat sink60is formed from a material chosen after comprehensive consideration of differences in linear expansion coefficient from the power modules, heat conductivity, weight, cost, and other factors. When a ceramic substrate with a pattern on each side, which is created by bonding Cu, Al, or a similar electrode material to each side of an insulating material, for example, Si3N4 or AlN, is used in the power modules10,20, and30, the difference in linear expansion coefficient at a pattern thickness within the range of pattern thicknesses used in practice (from 0.3 mm to 1.0 mm) is from 7 ppm/K to 12 ppm/K, and thus the ceramic substrate is a small-thermal expansion material. A composite material such as AlSiC or CuMo is accordingly favorable when importance is given to the difference in liner expansion coefficient between the heat sink60and the power modules10,20, and30. When Cu and a resin insulating material are used as main materials of the power modules10,20, and30, on the other hand, the linear expansion coefficient of Cu (16.8 ppm/K) is used as a rough indicator, and Cu or Al is accordingly favorable as the heat sink material. Note that, the combinations given above are not the only favorable materials because factors other than the difference in linear expansion coefficient are to be considered as well.

FIG.3is a sectional view of the power semiconductor device1taken along the lines III-III ofFIG.1. The control substrate50, which is illustrated in a detached state inFIG.1, is illustrated in a mounted state inFIG.3. The description given here takes as an example a portion in which the power modules10are fixed to the heat sink60. The configuration of this example, except dimensions, is the same also for portions in which the power modules20and30are fixed to the heat sink60.

As illustrated inFIG.3, control terminals11are mounted to each power module10to protrude toward a space above the power module10. The control substrate50is fixed to upper portions of the control terminals11. The control terminals11are inserted into the mounting holes40, which are formed in the control substrate50illustrated inFIG.1, and a fixing member80fixes the control substrate50to the inserted control terminals11.

The power module10includes a protruding portion12, which is formed to have a columnar shape and which protrudes toward a bottom surface of the power module10, in an end portion of the power module10on the side on which the control terminals11are mounted. The power module10includes another protruding portion13, which is formed to have a columnar shape and which protrudes toward the bottom surface of the power module10, in an end portion of the power module10on the opposite side from the end portion in which the protruding portion12is formed. The recessed portion60acorresponding to the protruding portion12and the recessed portion60bcorresponding to the protruding portion13are formed in the heat sink60. The protruding portions12and13are inserted to the recessed portions60aand60bof the heat sink60, respectively, to thereby position the power module10. The power module10is fixed to the heat sink60by a fixing layer70.

A material having a fixing function, high in heat radiation performance, and small in long-term deterioration, for example, solder or an electrically conductive adhesive, is used for the fixing layer70and the fixing material80. A sintered Ag material, a sintered Cu material, a sintered CuSn material, or a material similarly durable at a higher temperature than solder or an electrically conductive adhesive may also be used for the fixing layer70and the fixing material80. While bonding surfaces of the heat sink60and the power module10require no particular surface treatment when the material of the fixing layer70is an electrically conductive adhesive, bonding to an Al-based material is difficult when solder or a sintered material is used to bond metals. In the latter case, fine bonding is accomplished by performing surface treatment such as electrolytic Ni plating, electroless NiP plating, or Sn plating.

The power modules10,20, and30are connected to the circuits50a,50b, and50c, respectively, and are each configured with the use of a power chip optimum for the connected circuit. Consequently, there is almost no interchangeability in terms of power between the power modules10,20, and30. This means that the power semiconductor device1on the whole experiences power excess/shortage unless a power module of a prescribed type is mounted in a prescribed place.

The power semiconductor device1according to the first embodiment is therefore provided with a mechanism for preventing erroneous mounting of the power modules10,20, and30. The mechanism for preventing erroneous mounting of the power modules10,20, and30in the first embodiment is described below.

As illustrated inFIG.2, six pairs of the recessed portions60aand60bare formed in the area A of the heat sink60. Four pairs of the recessed portions60cand60dare formed in the area B. Six pairs of the recessed portions60eand60fare formed in the area C.

As illustrated inFIG.4AandFIG.4D, each power module10includes eight control terminals11. The control terminals11are lines for gate driving of the power chip, and lines for signals to a current sensor and to a temperature sensor built in the chip. Each of the control terminals11is mounted to the power module10to protrude perpendicularly to a mounting surface of the heat sink60when the power module10is mounted to the heat sink60. The control terminals11are each inserted into one of the mounting holes40of the control substrate50illustrated inFIG.1, and are soldered to the control substrate50.

The power module10also includes the columnar protruding portion12formed on an end surface of the power module10on the side on which the control terminals11are mounted, and the columnar protruding portion13formed on an end surface of the power module10on the opposite side. The protruding portion12is inserted into one of the recessed portions60aof the heat sink60illustrated inFIG.2, and the protruding portion13is inserted into one of the recessed portions60bof the heat sink60. The recessed portion60ais formed to have an inner diameter slightly greater than the outer diameter of the protruding portion12. The recessed portion60b, on the other hand, is formed to have a minor diameter that is greater than the outer diameter of the protruding portion13and to have a major diameter large enough to allow the protruding portion13to move a little within the recessed portion60b.

The clearance between the protruding portion12and the recessed portion60ais small, and the clearance between the protruding portion13and the recessed portion60bis large. The protruding portion12is inserted into the recessed portion60aat a small clearance in order to position each of the control terminals11mounted near the protruding portion12in relation to the arrangement of the mounting holes40of the control substrate50.

In this manner, the power module10can be positioned with respect to the heat sink60by the insertion of the protruding portions12and13of the power module10into the recessed portions60aand60bof the heat sink60. The control terminals11of the power module10can then be positioned with respect to the mounting holes40of the control substrate50. The same applies to the power modules20and the power modules30.

As illustrated inFIG.5AandFIG.5D, each power module20includes eight control terminals21. The control terminals21are, similarly to the control terminals11of each power module10, lines for gate driving of the power chip and lines for signals to a current sensor and to a temperature sensor built in the chip. Similarly to the control terminals11of each power module10, the control terminals21are mounted to the power module20to protrude perpendicularly to the mounting surface of the heat sink60when the power module20is mounted to the heat sink60. Similarly to the control terminals11of each power module10, the control terminals21are each inserted into one of the plurality of mounting holes40formed in the control substrate50illustrated inFIG.1, and are soldered to the control substrate50.

The power module20also includes a columnar protruding portion22formed on an end surface of the power module20on the side on which the control terminals21are mounted, and a columnar protruding portion23formed on an end surface of the power module20on the opposite side. The protruding portion22is inserted into one of the recessed portions60cof the heat sink60illustrated inFIG.2, and the protruding portion23is inserted into one of the recessed portions60dof the heat sink60.

The recessed portion60cis formed to have an inner diameter slightly greater than the outer diameter of the protruding portion22. The recessed portion60d, on the other hand, is formed to have a minor diameter that is greater than the outer diameter of the protruding portion23and to have a major diameter large enough to allow the protruding portion23to move a little within the recessed portion60d. The recessed portions60cand60dare formed in this manner and the protruding portions22and23of the power module20are assembled into the heat sink60, to thereby position the power module20with respect to the heat sink60.

As illustrated inFIG.6AandFIG.6D, each power module30includes four control terminals31. The control terminals31are, similarly to the control terminals11and12, lines for gate driving of the power chip and lines for signals to a current sensor and to a temperature sensor built in the chip. Each of the control terminals31is mounted to the power module30to protrude perpendicularly to the mounting surface of the heat sink60when the power module30is mounted to the heat sink60. The control terminals31are each inserted into one of the mounting holes40of the control substrate50illustrated inFIG.1, and are soldered to the control substrate50.

The power module30also includes a columnar protruding portion32formed on an end surface of the power module30on the side on which the control terminals31are mounted, and a columnar protruding portion33formed on an end surface of the power module30on the opposite side. The protruding portion32is inserted into one of the recessed portions60eof the heat sink60illustrated inFIG.2, and the protruding portion33is inserted into one of the recessed portions60fof the heat sink60.

The recessed portion60eis formed to have an inner diameter slightly greater than the outer diameter of the protruding portion32. The recessed portion60f, on the other hand, is formed to have a minor diameter that is greater than the outer diameter of the protruding portion33and to have a major diameter large enough to allow the protruding portion33to move a little within the recessed portion60f. The recessed portions60eand60fare formed in this manner and the protruding portions32and33of the power module30are assembled into the heat sink60, to thereby position the power module30with respect to the heat sink60.

As illustrated inFIG.1,FIG.6C, andFIG.6D, the protruding portion32formed in the power module30is arranged so that the direction of a straight line D3connecting the protruding portion32and the protruding portion33is unparallel to and offset from the direction of a straight line D1connecting the protruding portion12and the protruding portion13of the power module10and the direction of a straight line D2connecting the protruding portion22and the protruding portion23of the power module20. The offset is set so that an angle formed between the straight line D3and the straight lines D1and D2is 5° or more.

A distance L2between the protruding portion22and the protruding portion23of the power module20illustrated in FIG.5C is set longer than a distance L1between the protruding portion12and the protruding portion13of the power module10illustrated inFIG.4C.

As illustrated inFIG.2, the arrangement of one pair of the recessed portions60aand60bformed in the area A of the heat sink60corresponds to the arrangement of one pair of the protruding portions12and13formed in one power module10. The arrangement of one pair of the recessed portions60cand60dformed in the area B corresponds to the arrangement of one pair of the protruding portions22and23formed in one power module20. The arrangement of one pair of the recessed portions60eand60fformed in the area C corresponds to the arrangement of one pair of the protruding portions32and33formed in one power module30.

The protruding portions12and13of each power module10are designed so that the protruding portions12and13do not fit in and accordingly cannot be inserted into the recessed portions60cand60din the area B and the recessed portions60eand60fin the area C. The protruding portions22and23of each power module20are designed so that the protruding portions22and23do not fit in and accordingly cannot be inserted into the recessed portions60aand60bin the area A and the recessed portions60eand60fin the area C. The protruding portions32and33of each power module30are designed so that the protruding portions32and33do not fit in and accordingly cannot be inserted into the recessed portions60aand60bin the area A and the recessed portions60cand60din the area B.

In the power semiconductor device1according to the first embodiment, a positional relationship of the two protruding portions included in each power module10, the positional relationship of the two protruding portions included in each power module20, and the positional relationship of the two protruding portions included in each power module30are varied from one another in this manner. Combined with this, the recessed portions60aand60bformed in the area A of the heat sink60, the recessed portions60cand60dformed in the area B, and the recessed portions60eand60fformed in the area C are arranged so that the arrangement of the recessed portions in the area A, the arrangement of the recessed portions in the area B, and the arrangement of the recessed portions in the area C correspond to the positional relationship of the protruding portions in each power module10mounted in the area A, the positional relationship of the protruding portions in each power module20mounted in the area B, and the positional relationship of the protruding portions in each power module30mounted in the area C, respectively. A mistake in which a power module is mounted in an area that is not an area in which the power module is to be mounted can thus be prevented for the power modules10,20, and30.

The power semiconductor device1includes six power modules10, four power modules20, and six power modules30in the first embodiment, but the types and numbers of power modules included are not limited thereto. The protruding portions are also not limited to the mode in the first embodiment, in which one pair of protruding portions is formed in each power module. For instance, each power module may be provided with three or more protruding portions.

The protruding portions provided in the power modules have a columnar shape, and the recessed portions formed in the heat sink have a cylindrical shape and the shape of an elongated hole in the first embodiment, but the present invention is not limited thereto. For instance, the protruding portions may have hemispherical tips, or the protruding portions may have the shape of a rectangular column while the recessed portions are shaped as rectangular holes or elongated holes. It is preferred to bevel the tips of the protruding portions when the protruding portions are formed to have the shape of a rectangular column.

In the first embodiment, the protruding portions32and33of each power module30are arranged to be offset, and the distance between the protruding portions22and23in each power module20is varied from the distance between the protruding portions in each of the other power modules10and30, to thereby prevent erroneous mounting of the power modules. However, the present invention is not limited thereto. The erroneous mounting may be prevented by, for example, varying the number or shape of protruding portions from one power module type to another power module type.

In the first embodiment, four control terminals31are mounted to each power module30, eight control terminals11are mounted to each power module10, and eight control terminals21are mounted to each power module20. However, the numbers of control terminals are not limited thereto, and may be changed to suit specifications of the power semiconductor device1or the use of the power modules.

The protruding portions formed in the power modules10,20, and30are preferred to be molded from a resin material compatible with injection molding and high in heat resistance. When lead-free solder is used for the fixing layer70, in particular, the melting point of the solder is from about 220° C. to about 240° C. and thus, taking temperature fluctuations during the soldering process into consideration, it is preferred that the fixing layer70have a heat resistance of 260° C. or higher. Examples of the suitable material include polyphenylene sulfide (PPS), liquid crystal polymer resin, and fluorine-based resin. When a metal-based sintered material is used for the bonding, the processing temperature is within the range of from about 250° C. to about 300° C. in many cases, and a material having further higher heat resistance is accordingly selected to reduce heat deformation of the protruding portions.

A method of manufacturing the power semiconductor device1according to the present invention is described next.FIG.7is a diagram for illustrating an assembling procedure of the power semiconductor device1.FIG.8AtoFIG.8Eare diagrams for illustrating a void removal step in the method of manufacturing the power semiconductor device1.

FIG.9is a graph for showing changes with time of a temperature T of the fixing layer70by which the power modules10are fixed to the heat sink60, and changes with time of a pressure P of the atmosphere of the fixing layer70. InFIG.9, the axis of abscissa indicates a time t, and the axis of ordinate indicates the temperature T of the fixing layer70and the pressure P of the atmosphere of the fixing layer70. The solid line in the graph represents changes in the temperature T of the fixing layer70, and the broken line represents changes in the pressure P of the atmosphere of the fixing layer70. The dot-dash line in the graph represents a melting temperature Tm of the fixing layer70.

The description given here takes the power modules10as an example, but applies to the power modules20and30as well.

As illustrated inFIG.7, a solder71in a cream form is applied first as the fixing layer70to places in which the power modules10are to be mounted on the mounting surface of the heat sink60.

Next, in each power module10, the protruding portion12near the control terminals11is lined up with and inserted into the corresponding one of the recessed portions60aof the heat sink60. The other protruding portion of the power module10, namely, the protruding portion13, is next inserted into the corresponding one of the recessed portions60bof the heat sink60.

The distance between the protruding portion12and protruding portion13of the power module10is changed by thermal expansion, and also fluctuates due to a manufacturing error. The changes and the fluctuations, however, can be accommodated because each recessed portion60bis shaped as an elongated hole.

Next, the entire power module10is pressed lightly against the heat sink60to spread the solder71without leaving space between the power module10and the heat sink60.

A void removal step, in which an air bubble generated in the solder and called a void is removed, is executed at this point. A void remaining in the solder71cuts off a heat radiation path of the power module10, and is accordingly required to be removed. The void removal step is described with reference toFIG.8andFIG.9.

First, the solder71in the state ofFIG.8Ais heated and melted by raising the temperature T of the solder71to the melting temperature Tm of the solder71or higher as shown inFIG.9. A void Vo then appears in the melted solder71as illustrated inFIG.8B.

Next, in the manner shown inFIG.9, vacuuming is performed on the power semiconductor device1to reduce the pressure of the atmosphere of the melted solder71. The pressure reduction may be started before the solder71is heated. As the pressure reduction progresses, the internal pressure of the void Vo caught in the melted solder71becomes high relative to the outside, and the void Vo grows larger as illustrated inFIG.8C. The grown void Vo causes the power module10to lift off from the heat sink60.

The pressure reduction is continued at least until the pressure of the atmosphere of the melted solder71becomes 10 kPa or lower. This causes the void Vo to grow further and reach an end portion of the layer of the solder71as illustrated inFIG.8D. The interior of the void Vo then communicates to the outside of the melted solder71, thereby expelling air in the void Vo to the outside of the melted solder71. At this point, as illustrated inFIG.8E, the power module10lifted from the heat sink60sinks back into the heat sink60.

When the movement of the power module10settles down, as shown inFIG.9, the pressure reduction is ceased to return the pressure of the atmosphere of the melted solder71to the atmospheric pressure. In the case of a failure to expel the void Vo in the melted solder71, the remaining void Vo behaves to shrink when the melted solder71is returned from the reduced pressure to the atmospheric pressure. The size of the void Vo is made as small as possible by the shrinkage. On the other hand, a shift in the location of the void Vo in the process of void shrinking causes the power module10to lift, or the shrinking of the void Vo causes the power module10to sink down. The positional shift of the power module10can be minimized despite the lifting or sinking of the power module10, because of the protruding portions provided in the power module10and the recessed portions formed in the heat sink.

The heating of the melted solder71is then ceased. This completes the void removal step.

Next, when the melted solder71is solidified, the control substrate50is mounted to the plurality of control terminals11,21, and31of the power modules10,20, and30. Specifically, the control substrate50is pressed down along the control terminals11,21, and31until the control terminals11,21, and31protrude from the mounting holes40of the control substrate50for a length long enough for soldering.

Next, upper portions of the control terminals11,21, and31that are protruding from the control substrate50are soldered to the control substrate50. This completes the manufacturing of the power semiconductor device1.

In the void removal step, the power module10behaves to lift off from the heat sink60and then sink down. When a diagonal line of the power module10is set to a length of 55 mm, and the thickness of the layer of the solder71is set to from about 0.050 mm to about 0.500 mm, the height of the protruding portions12and13from the bottom surface of the power module10is preferred to be set to about from 1.5 mm to about 3.0 mm in order to prevent the protruding portions12and13of the power module10from sliding out of the recessed portions60aand60bof the heat sink60. The height of the protruding portions12and13is determined in proportion to the length of the diagonal line of the power module10.

A power semiconductor device1according to a second embodiment of the present invention is described next with reference toFIG.10andFIG.11.

Second Embodiment

The second embodiment differs from the first embodiment in that a guide member90is mounted to the control substrate50. The rest of the configuration is the same as in the first embodiment.

As illustrated inFIG.10, the guide member90used to guide the tips of the control terminals11into the mounting holes40of the control substrate50is mounted to the control substrate50of the second embodiment. The description given here takes as an example how the control substrate50is mounted to the control terminals11of each power module10. However, the control substrate50is mounted to the control terminals21and31of the power modules20and30in the same manner as in the example.

The guide member90is formed from an insulative resin material having high heat resistance, for example, liquid crystal polymer resin or fluorine-based resin. The guide member is fixed to the back of a circuit surface of the control substrate50with a heat resistant adhesive or the like.

FIG.11is an enlarged view of a portion E ofFIG.10. The guide member90is formed from a rectangular solid block material and, as illustrated inFIG.11, tapered through-holes are formed in a middle portion of the guide member90. Out of opening portions of each tapered through-hole, the smaller opening portion is formed to have an inner diameter large enough for one control terminal11to pass through. The guide member90is fixed with the opening portion smaller in inner diameter lined up with the corresponding one of the mounting holes40of the control substrate50.

When the control substrate50is mounted to the control terminal11, the tip of the control terminal11is touched to the opening portion of the guide member90that is larger in inner diameter, and is guided to the mounting hole40of the control substrate50. Once the tip of the control terminal11protrudes through to the circuit surface side of the control substrate50, the control substrate50and the control terminal11are fixed with the fixing material80, which is solder or a similar material.

According to the power semiconductor device1of the second embodiment, the guide member90configured to guide the control terminals11to the mounting holes40is mounted to the control substrate50in this manner. This enables the plurality of control terminals11to be quickly positioned and inserted into the plurality of mounting holes40of the control substrate50. The productivity of the power semiconductor device1can accordingly be improved.

The guide member90in the second embodiment is a rectangular solid block material in which tapered through-holes circular in cross section are formed, but is not limited thereto. For instance, the guide member90may be a columnar material in which tapered through-holes are formed, or the tapered through-holes may have a polygonal shape in cross section.

Third Embodiment

A third embodiment of the present invention is described with reference toFIG.12,FIG.13A, andFIG.13B.FIG.12is a top view for illustrating a direction X and a direction Y in each power semiconductor device according to the present invention.FIG.13Ais a top view of a power semiconductor device according to the third embodiment.FIG.13Bis a diagram for illustrating a cross section of the power semiconductor device ofFIG.13A.

As a soldering method other than the method of the first embodiment in which the solder71mixed with a flux is used, there is a method in which the processing chamber is put under a reducing atmosphere by the time solder finishes melting to keep the solder material from having a reducing action. The reducing atmosphere requires balance between low oxygen concentration and oxidation-reduction actions, and it is preferred to set the atmosphere to H2, HCOOH, N2, or the like, and set the oxygen concentration to 10 ppm or less.

When this method is used, solder can be supplied in a bulk form in which a given amount is secured. The bulk form may be varied depending on the required volume and shape of a portion to be soldered, to be chosen from a thin sheet form, a spherical form, a cubic form, a rectangular solid form, and the like.

Solder having a bulk form does not contain a residual component unlike solder mixed with a flux, and accordingly does not require washing of the product after soldering. Another advantage is that maintenance, for example, cleaning due to contamination on soldering equipment, can be performed at a decreased frequency. On the other hand, bulk-form solder is a block of metal and accordingly has no viscosity, and thus the solder itself does not have a positioning function. When the solder is not positioned, the bulk-form solder is displaced from a predetermined position in some cases in a conveyance step prior to soldering by, for example, the bumping of the work over a joint portion between conveyance rails, or acceleration in acceleration/deceleration while the work is conveyed. As a result, a required amount of solder may not be charged in a required place, resulting in a fear of having defective soldering.

As illustrated inFIG.12, each power module10, each power module20, and each power module30include a first protruding portion and a second protruding portion, and a positional shift of the bulk-form solder in the direction X can accordingly be regulated. The protruding portions, however, are incapable of regulating a positional shift in the direction Y. In addition, when bulk-form solder, particularly solder in a thin sheet form, is used to bond over a large area, the sheet-form solder is warped to generate an air space between the heat sink60and the solder, or between the solder and the power modules10, as a factor hindering the evening out of heat.

Herein, the solder in a thin sheet form is sheet-form solder having a thickness of from about 0.100 mm to about 0.500 mm, and the bonding over a large area means the bonding of solder bonding surfaces each having a dimension of from about 10 mm to about 60 mm along one side.

When heat is not evened out satisfactorily during a heating process for soldering, the solder lopsidedly wets and spreads on one of the two surfaces to be joined that has exceeded the melting point of the solder. Consequently, the solder may fail to spread to a place in which soldering is required, which leads to a fear of having defective soldering.

In order to solve the two problems, namely, the positional shift of the solder in the direction Y and the evening out of heat when the solder having a sheet form is used, in the third embodiment, as illustrated inFIG.13A, a block100made of metal high in heat conductivity is placed above the power modules10,20, and30along the longitudinal direction of the heat sink60.

The metal block100forms a heat transmission path above the power modules10,20, and30. As illustrated inFIG.13B, the metal block100also regulates the position of sheet-form solder72in the direction Y with the use of protruding portions101protruding downward from the metal block100. The metal block100is mounted to the heat sink60in a detachable manner. The metal block100is positioned on the heat sink60by a positioning pin102provided in at least each end portion of the metal block100, and a positioning hole (not shown) formed in the heat sink60. The positioning pin102may be provided on the heat sink60side while the positioning hole is formed in the metal block100side.

This stabilizes the quality of soldering, and improves the productivity of the power semiconductor device1as well. In addition, heat can be evened out in the large-sized power semiconductor device1conveyed into a furnace by placing the metal block100so that the metal block100stretches over the plurality of power modules10,20, and30, which are aligned in a single line.

REFERENCE SIGNS LIST