Semiconductor device and power conversion device

A semiconductor device includes a positive electrode-side semiconductor element, a negative electrode-side semiconductor element, a positive electrode plate, a negative electrode plate, an AC electrode plate, a positive electrode-side auxiliary electrode terminal, a negative electrode-side auxiliary electrode terminal, a positive electrode-side capacitor, and a negative electrode-side capacitor. The positive electrode plate is connected to a first positive electrode of the positive electrode-side semiconductor element. The negative electrode plate is connected to a second negative electrode of the negative electrode-side semiconductor element. The AC electrode plate is connected to a first negative electrode of the positive electrode-side semiconductor element and a second positive electrode of the negative electrode-side semiconductor element. The positive electrode-side capacitor is connected to the positive electrode plate and the positive electrode-side auxiliary electrode terminal. The negative electrode-side capacitor is connected to the negative electrode plate and the negative electrode-side auxiliary electrode terminal.

TECHNICAL FIELD

The present invention relates to a semiconductor device and a power conversion device.

BACKGROUND ART

As an example of a semiconductor device, a semiconductor power module including a semiconductor element for controlling electric power is known. It is known that, in a power conversion device configured using a semiconductor power module, noise is produced by the switching operation of the semiconductor element, the potential variations in a motor driven by the power conversion device, and the like. Since such noise leads to malfunctions of various electronic devices, a noise filter is inserted so as to suppress noise.

As one of the noise suppression means described above, there is a method of utilizing, as a noise filter, a capacitance produced between a semiconductor element and a heat dissipation conductor. Since the electrode joining a semiconductor element is generally connected to a heat dissipation conductor through a thin insulator, a capacitance exists between the semiconductor element and the heat dissipation conductor. This capacitance is utilized as a filter to control the path through which a noise current flows, thereby suppressing noise.

For example, Japanese Patent Laying-Open No. 2015-149883 (PTD 1) discloses a power conversion device configured to suppress noise by utilizing a capacitance produced between a semiconductor element and a heat dissipation conductor as a proximity bypass capacitor. Furthermore, this power conversion device includes a remote bypass capacitor that is longer in current path than the proximity bypass capacitor and greater in capacitance than the proximity bypass capacitor, thereby allowing suppression of noise in a large frequency region.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

In the power conversion device disclosed in the above-mentioned document, the capacitance produced between the semiconductor element and the heat dissipation conductor in the semiconductor power module is utilized as a filter, which causes a problem that noise is spread from the heat dissipation conductor. Specifically, there is a problem that a noise current flows into the heat dissipation conductor to cause generation of radiation noise from the heat dissipation conductor. Furthermore, when the heat dissipation conductor is connected to the ground, there is also a problem that a noise current propagates through the ground to a system power supply, a control circuit and the like.

The present invention has been made in light of the above-described problems. An object of the present invention is to provide a semiconductor device and a power conversion device, by which radiation noise produced from a heat dissipation conductor and a noise current diffused from the heat dissipation conductor can be suppressed.

Solution to Problem

A semiconductor device of the present invention includes a positive electrode-side semiconductor element, a negative electrode-side semiconductor element, a positive electrode plate, a negative electrode plate, an alternating-current (AC) electrode plate, a positive electrode-side auxiliary electrode terminal, a negative electrode-side auxiliary electrode terminal, a positive electrode-side capacitor, and a negative electrode-side capacitor. The positive electrode-side semiconductor element includes a first positive electrode and a first negative electrode. The negative electrode-side semiconductor element includes a second positive electrode and a second negative electrode. The positive electrode plate is connected to the first positive electrode of the positive electrode-side semiconductor element. The negative electrode plate is connected to the second negative electrode of the negative electrode-side semiconductor element. The AC electrode plate is connected to the first negative electrode of the positive electrode-side semiconductor element and the second positive electrode of the negative electrode-side semiconductor element. The positive electrode-side capacitor is connected to the positive electrode plate and the positive electrode-side auxiliary electrode terminal. The negative electrode-side capacitor is connected to the negative electrode plate and the negative electrode-side auxiliary electrode terminal.

Advantageous Effects of Invention

According to the semiconductor device of the present invention, a noise current can be controlled by: a current path formed of the first positive electrode, the positive electrode plate, the positive electrode-side capacitor, and the positive electrode-side auxiliary electrode in the positive electrode-side semiconductor element; and a current path formed of the second negative electrode, the negative electrode plate, the negative electrode-side capacitor, and the negative electrode-side auxiliary electrode in the negative electrode-side semiconductor element. Accordingly, when each of the positive electrode-side semiconductor element and the negative electrode-side semiconductor element is connected to a heat dissipation conductor through an insulator, a noise current flowing through the heat dissipation conductor can be reduced. Thus, the radiation noise produced from the heat dissipation conductor and the noise current diffused from the heat dissipation conductor can be suppressed.

DESCRIPTION OF EMBODIMENTS

The embodiments of the present invention will be hereinafter described with reference to the accompanying drawings.

First Embodiment

Referring toFIGS. 1 and 2, the schematic configuration of a semiconductor power module according to the first embodiment of the present invention will be hereinafter described. In the present embodiment, as an example of the semiconductor device, a semiconductor power module including a semiconductor element for controlling electric power will be described.FIG. 1is a cross-sectional view schematically showing the internal configuration of a semiconductor power module according to the first embodiment, which is taken along a line I-I inFIG. 2.FIG. 2is a top view schematically showing the internal configuration of the semiconductor power module according to the first embodiment.

A semiconductor power module (semiconductor device)1of the present embodiment mainly includes a heat dissipation conductor2, an insulator3, a positive electrode plate4, a negative electrode plate5, an AC electrode plate6, a positive electrode-side semiconductor element7, a negative electrode-side semiconductor element8, a first connection conductor9, a second connection conductor10, a positive electrode-side capacitor11, a negative electrode-side capacitor12, a positive electrode-side auxiliary electrode terminal13, a negative electrode-side auxiliary electrode terminal14, a sealing material15, a positive electrode terminal41, a negative electrode terminal51, and an AC electrode terminal61.

Insulator3is disposed on heat dissipation conductor2, on which positive electrode plate4, negative electrode plate5and AC electrode plate6are disposed. Insulator3is provided between heat dissipation conductor2and each of positive electrode plate4, negative electrode plate5and AC electrode plate6.

Positive electrode-side semiconductor element7, positive electrode-side capacitor11and positive electrode terminal41are provided on positive electrode plate4. Positive electrode-side semiconductor element7includes a positive electrode (the first positive electrode)71and a negative electrode (the first negative electrode)72. Positive electrode plate4is connected to positive electrode (the first positive electrode)71of positive electrode-side semiconductor element7. Negative electrode (the first negative electrode)72of positive electrode-side semiconductor element7is connected to AC electrode plate6through first connection conductor9. Positive electrode-side capacitor11is connected to positive electrode plate4. Positive electrode-side capacitor11is disposed across positive electrode plate4from insulator3. Also, positive electrode-side capacitor11is disposed across insulator3from heat dissipation conductor2. Positive electrode-side auxiliary electrode terminal13is provided on positive electrode-side capacitor11. Positive electrode-side capacitor11is connected to positive electrode-side auxiliary electrode terminal13. Positive electrode terminal41is connected to positive electrode plate4. In the above description, positive electrode-side semiconductor element7is provided on positive electrode plate4and connected to AC electrode plate6through first connection conductor9, but positive electrode-side semiconductor element7may be provided on AC electrode plate6and connected to positive electrode plate4through first connection conductor9. In other words, positive electrode-side semiconductor element7only has to be connected to one of positive electrode plate4and AC electrode plate6through first connection conductor9.

First connection conductor9, negative electrode-side semiconductor element8and AC electrode terminal61are provided on AC electrode plate6. Negative electrode-side semiconductor element8includes a positive electrode (the second positive electrode)81and a negative electrode (the second negative electrode)82. AC electrode plate6is connected to positive electrode (the second positive electrode)81of negative electrode-side semiconductor element8. Negative electrode (the second negative electrode)82of negative electrode-side semiconductor element8is connected to negative electrode plate5through second connection conductor10. AC electrode terminal61is connected to AC electrode plate6. In the above description, negative electrode-side semiconductor element8is provided on AC electrode plate6and connected to negative electrode plate5through second connection conductor10, but negative electrode-side semiconductor element8may be provided on negative electrode plate5and connected to AC electrode plate6through second connection conductor10. In other words, negative electrode-side semiconductor element8only has to be connected to one of negative electrode plate5and AC electrode plate6through second connection conductor10.

Insulator3, positive electrode plate4, negative electrode plate5, AC electrode plate6, positive electrode-side semiconductor element7, negative electrode-side semiconductor element8, first connection conductor9, second connection conductor10, positive electrode-side capacitor11, and negative electrode-side capacitor12that are disposed on heat dissipation conductor2are covered with sealing material15. Furthermore, positive electrode-side auxiliary electrode terminal13, negative electrode-side auxiliary electrode terminal14, positive electrode terminal41, negative electrode terminal51, and AC electrode terminal61are also covered with sealing material15. However, a part of each of positive electrode-side auxiliary electrode terminal13, negative electrode-side auxiliary electrode terminal14, positive electrode terminal41, negative electrode terminal51, AC electrode terminal61, positive electrode-side auxiliary electrode terminal13, and negative electrode-side auxiliary electrode terminal14is exposed to the outside of sealing material15.

It is to be noted that sealing material15is not shown inFIG. 2for the purpose of showing the internal configuration of semiconductor power module1. The same also applies to other top views. Although not shown inFIGS. 1 and 2, semiconductor power module1may include a case into which sealing material15is introduced.

Since positive electrode plate4and negative electrode plate5face heat dissipation conductor2with thin insulator3interposed therebetween, a stray capacitance16exists between heat dissipation conductor2and positive electrode plate4while a stray capacitance18exists between heat dissipation conductor2and negative electrode plate5. In this case, positive electrode-side capacitor11is provided such that the capacitance of positive electrode-side capacitor11is greater than stray capacitance16. In other words, the capacitance of positive electrode-side capacitor11is greater than the capacitance provided between positive electrode (the first positive electrode)71of positive electrode-side semiconductor element7and heat dissipation conductor2with positive electrode plate4interposed therebetween. Furthermore, negative electrode-side capacitor12is provided such that the capacitance of negative electrode-side capacitor12is greater than stray capacitance18. In other words, the capacitance of negative electrode-side capacitor12is greater than the capacitance provided between negative electrode (the second negative electrode)82of negative electrode-side semiconductor element8and heat dissipation conductor2with negative electrode plate5interposed therebetween.

Then, referring toFIGS. 3 and 4, an example of the specific configuration of semiconductor power module1according to the present embodiment will be hereinafter described. Semiconductor power module1shown in each ofFIGS. 3 and 4is a single-phase bridge inverter configured to have a structure shown in each ofFIGS. 1 and 2.FIG. 3is a circuit diagram schematically showing the configuration of a single-phase bridge inverter in semiconductor power module1.FIG. 4is a top view schematically showing the internal configuration of the single-phase bridge inverter in semiconductor power module1.

First connection conductor9and second connection conductor10each may be made of an optional material having conductivity and formed in an optional shape. First connection conductor9and second connection conductor10each are formed, for example, of a copper lead frame, an aluminum wire, or the like. Thereby, a single-phase bridge inverter21is formed. Stray capacitance16is a parasitic capacitance that exists between positive electrode plate4and heat dissipation conductor2. Stray capacitance18is a parasitic capacitance that exists between negative electrode plate5and heat dissipation conductor2. Also, heat dissipation conductor2is connected to the ground.

Generally, noise is produced by the switching operation of the semiconductor element, the potential variations in the motor connected to the AC electrode terminal, and the like. A noise current flows through a current path with a small impedance. A current I and an impedance Z with respect to a capacitance C are expressed by the following equations (1) and (2), respectively.
I=V/Z(2)
Z=1/(jωC)=1/(j2πfC)  (2)

In this case, j indicates an imaginary component, ω indicates an angular frequency, f indicates a frequency, and V indicates a voltage. Since a noise current is produced by an instantaneous switching operation and potential variations, this noise current contains a lot of high frequency components having a high frequency f. In other words, impedance Z in the equation (2) shows a low value with respect to the current containing high frequency components having frequency f. On the other hand, impedance Z shows a high value with respect to the current containing low frequency components having low frequency f. Furthermore, based on the equation (2), impedance Z shows a lower value as capacitance C is greater. Accordingly, a path having a large capacitance is provided to thereby allow formation of a path exhibiting a small impedance with respect to the noise current containing a lot of high frequency components. Thereby, the path through which a noise current flows can be set in advance, so that it becomes possible to control the current so as not to flow into a path with a low noise tolerance.

The functions and effects of the present embodiment will then be described.

According to semiconductor power module1of the present embodiment, the noise current can be controlled by: a current path formed of positive electrode (the first positive electrode)71of positive electrode-side semiconductor element7, positive electrode plate4, positive electrode-side capacitor11, and positive electrode-side auxiliary electrode terminal13; and a current path formed of negative electrode (the second negative electrode)82of negative electrode-side semiconductor element8, negative electrode plate5, negative electrode-side capacitor12, and negative electrode-side auxiliary electrode terminal14. Accordingly, when each of positive electrode-side semiconductor element7and negative electrode-side semiconductor element8is connected to heat dissipation conductor2through insulator3, the noise current flowing through heat dissipation conductor2can be reduced. Therefore, it becomes possible to suppress the radiation noise generated from heat dissipation conductor2and the noise current diffused from heat dissipation conductor2.

Furthermore, according to semiconductor power module1of the first embodiment in the present invention, positive electrode-side capacitor11that is greater in capacitance than stray capacitance16is provided on the positive electrode side. In other words, the capacitance of positive electrode-side capacitor11is greater than the capacitance provided between positive electrode (the first positive electrode)71of positive electrode-side semiconductor element7and heat dissipation conductor2with positive electrode plate4interposed therebetween. Thereby, it becomes possible to form a noise current path that is lower in impedance than the path of the noise current flowing through stray capacitance16into heat dissipation conductor2. Furthermore, negative electrode-side capacitor12that is greater in capacitance than stray capacitance18is provided on the negative electrode side. In other words, the capacitance of negative electrode-side capacitor12is greater than the capacitance provided between negative electrode (the second negative electrode)82of negative electrode-side semiconductor element8and heat dissipation conductor2with negative electrode plate5interposed therebetween. Accordingly, it becomes possible to form a noise current path that is lower in impedance than the path of the noise current flowing through stray capacitance18into heat dissipation conductor2. Thereby, it becomes possible to control the noise current so as not to flow through a path with a low noise tolerance. As a result, the noise current flowing through stray capacitances16and18into heat dissipation conductor2can be suppressed, so that it becomes possible to reduce the radiation noise generated from heat dissipation conductor2and the noise current propagating through heat dissipation conductor2to the outside.

Also, by using a capacitor, without having to change the structure of semiconductor power module1, the capacitance of the noise current path provided on each of the positive electrode side and the negative electrode side can be readily changed to a desired value. In other words, it becomes possible to readily provide a path that is lower in impedance than the path extending through heat dissipation conductor2with respect to the noise current containing a lot of high frequency components.

Furthermore, in the case where the ratio of the capacitance of negative electrode-side capacitor12to the capacitance of positive electrode-side capacitor11is set at 0.9 to 1.1, the impedance can be balanced between the positive electrode side and the negative electrode side. Accordingly, the potential variations in the circuit during the operation of the inverter can be reduced. Thereby, generation of the noise by potential variations can be suppressed.

Furthermore, according to semiconductor power module1of the first embodiment in the present invention, positive electrode-side semiconductor element7is connected to one of positive electrode plate4and AC electrode plate6through first connection conductor9. Negative electrode-side semiconductor element8is connected to one of negative electrode plate5and AC electrode plate6through second connection conductor10. Thereby, electrical connection can be readily established through the connection of first connection conductor9and second connection conductor10.

Second Embodiment

The same configurations as those in the above-described embodiment are designated by the same reference characters unless otherwise particularly explained, and the description thereof will not be repeated. The same also applies to the third to seventh embodiments.

Referring toFIGS. 5 and 6, a semiconductor power module1according to the second embodiment of the present invention will be hereinafter described.FIG. 5is a top view schematically showing the internal configuration of semiconductor power module1according to the second embodiment.FIG. 6is a circuit diagram schematically showing the configuration of semiconductor power module1according to the second embodiment.

Semiconductor power module1according to the second embodiment is a semiconductor power module including a three-phase bridge inverter22formed by combining three single-phase bridge inverters shown in the first embodiment.

In this way, semiconductor power module1according to the second embodiment is similar in basic configuration to semiconductor power module1according to the first embodiment, but is different from semiconductor power module1according to the first embodiment in that three-phase bridge inverter22is formed inside a single module and that positive electrode-side capacitor11and negative electrode-side capacitor12that are disposed in each phase are shared in common.

According to semiconductor power module1of the second embodiment, the path through which a noise current flows can be set in advance, so that the current can be controlled so as not to flow through the path having a low noise tolerance. Furthermore, three-phase bridge inverter22is formed inside a single module, and positive electrode-side capacitor11and negative electrode-side capacitor12are shared in common, so that the module can be reduced in size.

Third Embodiment

Then, referring toFIGS. 7 and 8, a semiconductor power module1according to the third embodiment will be hereinafter described.FIG. 7is a top view schematically showing the internal configuration of a single-phase bridge inverter in semiconductor power module1according to the third embodiment.FIG. 8is a top view schematically showing the internal configuration of a three-phase bridge inverter in semiconductor power module1according to the third embodiment.

Semiconductor power module1according to the third embodiment shown inFIG. 7is different from semiconductor power module1according to the first embodiment or the second embodiment mainly in that negative electrode plate5is disposed on negative electrode-side semiconductor element8and negative electrode-side reflux diode20.

Semiconductor power module1according to the third embodiment further includes an auxiliary electrode plate23. Auxiliary electrode plate23is provided on insulator3. Negative electrode-side auxiliary electrode terminal14is connected to auxiliary electrode plate23. Negative electrode-side capacitor12is disposed on auxiliary electrode plate23. Negative electrode plate5is disposed on negative electrode-side capacitor12. Negative electrode plate5is disposed on negative electrode-side reflux diode20. Negative electrode plate5is disposed on negative electrode-side semiconductor element8. Negative electrode-side semiconductor element8is connected to negative electrode-side reflux diode20through negative electrode plate5. Negative electrode plate5is provided on negative electrode terminal51.

Semiconductor power module1according to the third embodiment shown inFIG. 8is a semiconductor power module including a three-phase bridge inverter formed by combining three single-phase bridge inverters shown inFIG. 7.

In semiconductor power module1according to the third embodiment shown inFIG. 8, negative electrode plate5is disposed on negative electrode-side semiconductor elements8a,8band8c. Negative electrode plate5is disposed on negative electrode-side reflux diodes20a,20band20c. Negative electrode-side semiconductor elements8a,8b, and8care connected to negative electrode-side reflux diodes20a,20b, and20c, respectively, through negative electrode plate5.

According to semiconductor power module1of the third embodiment, negative electrode plate5is disposed on negative electrode-side semiconductor element8(8a,8b,8c) and negative electrode-side capacitor12. Thus, negative electrode plate5is provided on a plane different from positive electrode plate4and AC electrode plate6, so that semiconductor power module1can be further reduced in size.

Fourth Embodiment

Then, referring toFIG. 9, a semiconductor power module1according to the fourth embodiment will be hereinafter described.FIG. 9is a perspective view schematically showing a part of the internal configuration of semiconductor power module1according to the fourth embodiment.FIG. 9does not show heat dissipation conductor2, insulator3and sealing material15for the sake of explanation.

Positive electrode-side semiconductor element7and positive electrode-side reflux diode19are disposed on positive electrode plate4. Positive electrode (the first positive electrode)71of positive electrode-side semiconductor element7and the negative electrode of positive electrode-side reflux diode19are connected to positive electrode plate4.

AC electrode plate6is disposed on positive electrode-side semiconductor element7and positive electrode-side reflux diode19. Negative electrode-side semiconductor element8and negative electrode-side reflux diode20are disposed on AC electrode plate6. Negative electrode (the first negative electrode)72of positive electrode-side semiconductor element7and the positive electrode of positive electrode-side reflux diode19are connected to positive electrode (the second positive electrode)81of negative electrode-side semiconductor element8and the negative electrode of negative electrode-side reflux diode20through AC electrode plate6.

Negative electrode plate5is disposed on negative electrode-side semiconductor element8and negative electrode-side reflux diode20. Negative electrode (the second negative electrode)82of negative electrode-side semiconductor element8and the positive electrode of negative electrode-side reflux diode20are connected to negative electrode plate5.

According to the semiconductor power module of the fourth embodiment, positive electrode-side semiconductor element7and negative electrode-side semiconductor element8are arranged in a three-dimensional structure. Therefore, it becomes possible to implement a semiconductor element having a high density as compared with the conventional semiconductor power module in which positive electrode-side semiconductor element7and negative electrode-side semiconductor element8are arranged in the same plane, so that the semiconductor power module can be further reduced in size.

Furthermore, according to the semiconductor power module of the fourth embodiment, positive electrode-side reflux diode19and negative electrode-side reflux diode20are arranged in a three-dimensional structure. Therefore, it becomes possible to implement a semiconductor element having a high density as compared with the conventional semiconductor power module in which positive electrode-side reflux diode19and negative electrode-side reflux diode20are arranged in the same plane, so that the semiconductor power module can be further reduced in size.

Fifth Embodiment

Then, a semiconductor power module1according to the fifth embodiment will be hereinafter described with reference toFIGS. 10 and 11.FIG. 10is a top view schematically showing the internal configuration of an example of semiconductor power module1according to the fifth embodiment.FIG. 10corresponds toFIG. 4.FIG. 11is a perspective view schematically showing the internal configuration of another example of the semiconductor power module according to the fifth embodiment.FIG. 11also corresponds toFIG. 9.

Semiconductor power module1according to the fifth embodiment is different from semiconductor power module1according to each of the first to fourth embodiments in that a common auxiliary electrode terminal100is connected to positive electrode-side capacitor11and negative electrode-side capacitor12.

In semiconductor power module1according to the fifth embodiment, positive electrode-side auxiliary electrode terminal13and negative electrode-side auxiliary electrode terminal14are integrated with each other to form common auxiliary electrode terminal100. As positive electrode-side auxiliary electrode terminal13connected to positive electrode-side capacitor11and negative electrode-side auxiliary electrode terminal14connected to negative electrode-side capacitor12, common auxiliary electrode terminal100is connected to positive electrode-side capacitor11and negative electrode-side capacitor12.

According to semiconductor power module1of the fifth embodiment, common auxiliary electrode terminal100is connected to positive electrode-side capacitor11and negative electrode-side capacitor12, so that the structure can be simplified and reduced in size.

Sixth Embodiment

Then, referring toFIGS. 12 and 13, a semiconductor power module1according to the sixth embodiment will be hereinafter described.FIG. 12is a cross-sectional view schematically showing the internal configuration of semiconductor power module1according to the sixth embodiment.FIG. 13is a schematic cross-sectional view schematically showing the configuration of a stacked conductor pattern according to the sixth embodiment.

Semiconductor power module1according to the sixth embodiment is different from semiconductor power module1according to each of the first to fifth embodiments in that stacked conductor patterns200and201are provided as positive electrode-side capacitor11and negative electrode-side capacitor12, respectively. In the present embodiment, each of positive electrode-side capacitor11and negative electrode-side capacitor12includes a conductor203and an insulator202. Positive electrode-side capacitor11is formed by sandwiching insulator202between positive electrode plate4and conductor203while negative electrode-side capacitor12is formed by sandwiching insulator202between negative electrode plate5and conductor203.

As shown inFIG. 12, stacked conductor patterns200and201each has a configuration in which insulator202and conductor203are alternately stacked. The number of stacks of insulator202and conductor203may be one, or may be two or more. The following is an explanation with reference to an example of the case where the number of stacks is more than one. Each of positive electrode-side capacitor11and negative electrode-side capacitor12includes a plurality of conductors203and a plurality of insulators202that are equal in number to the plurality of conductors203. Insulators202and conductors203are stacked alternately one by one sequentially in a single column on each of positive electrode plate4and negative electrode plate5. Among conductors203stacked on positive electrode plate4, a conductor203in an odd-numbered layer counted from positive electrode plate4is connected to positive electrode-side auxiliary electrode terminal13and a conductor203in an even-numbered layer counted from positive electrode plate4is connected to positive electrode plate4. Among conductors203stacked on negative electrode plate5, a conductor203in an odd-numbered layer counted from negative electrode plate5is connected to negative electrode-side auxiliary electrode terminal14and a conductor203in an even-numbered layer counted from negative electrode plate5is connected to negative electrode plate5.

Referring toFIG. 13, the configuration of stacked conductor pattern200will be hereinafter specifically described. For example, when three layers are stacked, stacked conductor pattern200includes a first insulator202a, a second insulator202b, a third insulator202c, a first conductor203a, a second conductor203b, and a third conductor203c.

First insulator202a, second insulator202band third insulator202c; and first conductor203a, second conductor203band third conductor203care alternately stacked in a single column specifically such that first insulator202a, first conductor203a, second insulator202b, second conductor203b, third insulator202c, and third conductor203care stacked in this order. First insulator202ais sandwiched between positive electrode plate4and first conductor203a. Second insulator202bis sandwiched between first conductor203aand second conductor203b. Third insulator202cis sandwiched between second conductor203band third conductor203c. First conductor203ais connected to third conductor203c. Second conductor203bis connected to positive electrode plate4. Third conductor203cis connected to positive electrode-side auxiliary electrode terminal13.

In this way, when first conductor203a, second conductor203band third conductor203cthat are stacked are connected in every layer, capacitances204a,204band204cproduced between conductors are connected in parallel with one another. Thus, the capacitance produced between positive electrode plate4and positive electrode-side auxiliary electrode terminal13can be increased in capacity.

Stacked conductor pattern201also has the same configuration. Stacked conductor pattern201is different from stacked conductor pattern200in that: first insulator202ais sandwiched between negative electrode plate5and first conductor203a; second conductor203bis connected to negative electrode plate5; and third conductor203cis connected to negative electrode-side auxiliary electrode terminal14. In stacked conductor pattern201, the capacitance produced between negative electrode plate5and negative electrode-side auxiliary electrode terminal14can be increased in capacity.

The capacitance of stacked conductor pattern200connected to the positive electrode side is represented as εS/d using: facing areas S between positive electrode plate4and first conductor203a, between first conductor203aand second conductor203b, between second conductor203band third conductor203c; and a thickness d and a dielectric constant ε of first insulator202a, second insulator202band third insulator202c. On the other hand, stray capacitance16on the positive electrode side is represented as ε′S′/d′ using: a facing area S′ between positive electrode plate4and heat dissipation conductor2; and a thickness d′ and a dielectric constant ε′ of insulator3. Accordingly, when the ratio of εS/d to ε′S′/d′ is set to be greater than 1, the same effect as that of semiconductor power module1according to each of the first to fifth embodiments can be obtained. In order to increase capacitance εS/d of the stacked conductor pattern, for example, the area of conductor203may be increased, the number of stacks of conductors203may be increased, the thickness of insulator202may be reduced, the dielectric constant of insulator202may be increased, and the like. This also applies to stacked conductor pattern201on the negative electrode side.

According to semiconductor power module1of the sixth embodiment, stacked conductor pattern200and stacked conductor pattern201are provided as positive electrode-side capacitor11and negative electrode-side capacitor12, respectively. Accordingly, by using stacked conductor patterns200and201, without having to use a capacitor, the capacitance larger in capacity than stray capacitances16and18can be implemented.

According to power module1of the present embodiment, positive electrode-side capacitor11is formed by sandwiching insulator202between positive electrode plate4and conductor203while negative electrode-side capacitor12is formed by sandwiching insulator202between negative electrode plate5and conductor203. Accordingly, a capacitance with large capacity can be implemented by stacking conductor203and insulator202.

Furthermore, according to power module1of the present embodiment, each of positive electrode-side capacitor11and negative electrode-side capacitor12includes a plurality of conductors203and a plurality of insulators202that are equal in number to the plurality of conductors203. Among conductors203stacked on positive electrode plate4, a conductor203in an odd-numbered layer counted from positive electrode plate4is connected to positive electrode-side auxiliary electrode terminal13and a conductor203in an even-numbered layer counted from positive electrode plate4is connected to positive electrode plate4. Also, among conductors203stacked on negative electrode plate5, a conductor203in an odd-numbered layer counted from negative electrode plate5is connected to negative electrode-side auxiliary electrode terminal14and a conductor203in an even-numbered layer counted from negative electrode plate5is connected to negative electrode plate5. Thus, a capacitance with large capacity can be implemented by stacking a plurality of conductors203and a plurality of insulators202.

Seventh Embodiment

Then, referring toFIGS. 14 and 15, a power conversion device300according to the seventh embodiment will be hereinafter described.FIG. 14is a circuit diagram schematically showing the configuration of power conversion device300according to the seventh embodiment.FIG. 15is a circuit diagram schematically showing the configuration of a modification of the power conversion device according to the seventh embodiment.

Power conversion device300includes a semiconductor power module1. A DC power supply301and a smoothing capacitor302are connected in parallel with positive electrode terminal41and negative electrode terminal51of semiconductor power module1. AC electrode terminals61a,61band61care connected to a motor (load)303. Heat dissipation conductor2is connected to the ground. In this case, the ground is defined as a reference potential of the power conversion device, and provided as a metal housing and the like of power conversion device300, for example. Motor303is housed in a motor-accommodating metal housing (a load-accommodating metal housing)304. Also, motor-accommodating metal housing304is connected to positive electrode-side auxiliary electrode terminal13and negative electrode-side auxiliary electrode terminal14of semiconductor power module1through a connection line306. A stray capacitance305exists between motor303and motor-accommodating metal housing304. Thus, a current path307and a current path308each are formed by three-phase bridge inverter22, positive electrode-side capacitor11or negative electrode-side capacitor12, connection line306, stray capacitance305, and motor303.

According to semiconductor power module1of the seventh embodiment, positive electrode-side auxiliary electrode terminal13and negative electrode-side auxiliary electrode terminal14are connected to motor-accommodating metal housing304. Also, the capacitance by positive electrode-side capacitor11and the capacitance by negative electrode-side capacitor12are greater than stray capacitance16and stray capacitance18, respectively. Accordingly, current path307and current path308are low in impedance with respect to the noise current containing a high frequency component. Thus, the noise current can be controlled. Therefore, the noise current flowing through heat dissipation conductor2can be suppressed. Consequently, it becomes possible to reduce the noise current propagating through heat dissipation conductor2and the radiation noise generated from heat dissipation conductor2.

Furthermore, as shown inFIG. 15, motor-accommodating metal housing304may be connected to the ground through an inductor309. In the modification of the power conversion device according to the seventh embodiment, motor-accommodating metal housing304is connected to the ground through inductor309.

Inductor309shows a high impedance with respect to the noise current containing a lot of high frequency components as represented in the following equation (3). In this case, L indicates an inductance.
Z=jωL=j2πfL(3)

In the modification of the power conversion device according to the seventh embodiment, motor-accommodating metal housing304is connected to the ground through inductor309. Accordingly, the electric potential of motor-accommodating metal housing304can be stabilized at the electric potential of the ground, and the noise current flowing through the ground can be suppressed. Therefore, the noise propagating from the ground can be suppressed.

Semiconductor power module1according to each of the first to seventh embodiments has a configuration in which positive electrode-side capacitor11and negative electrode-side capacitor12or stacked conductor patterns200and201are incorporated by sealing material15, but may be connected to positive electrode terminal41and negative electrode terminal51on the outside of sealing material15. In this case, positive electrode-side auxiliary electrode terminal13, negative electrode-side auxiliary electrode terminal14or common auxiliary electrode terminal100may be entirely exposed.

In addition, the members forming semiconductor power module1according to each of the first to seventh embodiments only have to be connected by any method but may be connected, for example, by solder, an adhesive and the like.

The above-described embodiments can be combined as appropriate.

REFERENCE SIGNS LIST