Patent Application
20250149399
The present disclosure relates to a power module and a power conversion apparatus.
A power module is mounted on every product such as an industrial apparatus, a home electrical appliance, and an information terminal, and high productivity is required in a power module. A high heat radiation property is required in a power module mounted on an electrical automobile, and a high degree of flatness is required to ensure fastening to a water-cooling jacket. Also required is a package form adoptable to SiC semiconductor which has a high possibility of becoming mainstream in the future since the SiC semiconductor has a high operation temperature and is excellent in efficiency.
The power module is becoming popular in every situation of power generation, power transmission, and power regeneration of electrical energy with increase of environmental problems. Large current and high voltage are handled in the power module, thus a ceramic substrate having a high insulation property and a high heat radiation property is used as an insulating substrate. However, aluminum nitride and silicon nitride, for example, as a material of a ceramic base material has a significantly small linear expansion coefficient compared with copper and aluminum used for a heat radiation member, for example. Thus, when these members are bonded, large heat stress occurs in a bonding position, and there is a problem that a warpage and a crack in a temperature cycle easily occur in the heat radiation member.
For example, proposed in Patent Document 1 is a structure of a power module in which a semiconductor element is mounted on a ceramic substrate, a circuit is formed by wire bonding, and a pin terminal is used as an external terminal.
Patent Document 1: Japanese Patent No. 5978589
However, in the technique described in Patent Document 1, a front surface conductive layer serving as a circuit pattern is provided on an upper surface of the ceramic substrate to mount the semiconductor element and the pin terminal, and a back surface conductive layer is provided on almost an entire lower surface of the ceramic substrate.
In a case of an in-vehicle power module mounted on an electrical automobile, for example, a size of an element exceeds 10 mm square, the number of elements is twelve in a case of 6in1 module, and a size of the ceramic substrate is large, that is 60 mm to 70 mm.
When the large ceramic substrate is bonded to a heat radiation member made of copper or aluminum, an excessive warpage occurs in the heat radiation member by reason that there is a large difference of linear expansion coefficient between the ceramic substrate and the heat radiation member. When a power module is water-cooled (liquid-cooled) using the heat radiation member, the power module needs to be generally fixed to a water-cooling jacket which is a metal rigid body. A warpage is suppressed to some extent by fastening with a screw, for example, however, the warpage needs to be further suppressed to evenly apply deformation pressure to an O-ring to obtain a watertight state.
Accordingly, an object of the present disclosure is to provide a technique capable of suppressing a warpage of a heat radiation member caused by heat stress in a power module.
A power module according to the present disclosure includes: a semiconductor element; an insulating substrate including a front surface conductive layer on which the semiconductor element is mounted and a back surface conductive layer on a side opposite to the front surface conductive layer; and a heat radiation member bonded to the back surface conductive layer, wherein a bonding region in the insulating substrate bonded to the heat radiation member is a region corresponding to a portion on which the semiconductor element is mounted, and an area of the front surface conductive layer is larger than an area of the back surface conductive layer.
According to the present disclosure, the area of the bonding region in the insulating substrate bonded to the heat radiation member is reduced, thus the warpage of the heat radiation member caused by heat stress can be suppressed.
These and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
An embodiment 1 is described hereinafter using the diagrams.
As illustrated in
The case 5 is made of Polyphenylenesulfide (PPS) resin, and is formed into a rectangular frame-like shape in a top view. A size of the case 5 is 100 mm in width, 80 mm in depth, and 6 mm in thickness. The external electrode 61 and the signal electrode 63 are integrally formed with the case 5 by insert molding.
The fin base 70 is made of aluminum alloy, and includes a base part 70a and a plurality of pin parts 70b protruding to a lower side from the base part 70a. The base part 70a is formed into a rectangular shape in a top view. A size of the base part 70a is 100 mm in width, 80 mm in depth, and 3 mm in thickness. A size of each pin part 70b is 1.5 mm in diameter and 5 mm in length.
A peripheral edge part of an upper surface of the base part 70a is fixed to the case 5 by an adhesive agent 81. Nickel plating is applied to a region in the base part 70a except for the peripheral edge part of the upper surface thereof, and the region is bonded to the ceramic substrate 10 by a solder 30. The solder 30 is made of 96.5% tin, 3% silver, and 0.5% copper, and a melting point of the solder 30 is 217° C.
Each of two ceramic substrates 10 includes a base material 11, a front surface conductive layer 12, and a back surface conductive layer 13. The base material 11 is made of aluminum nitride, and a thickness of the base material 11 is 0.64 mm. The front surface conductive layer 12 is made of copper, and is provided on an upper surface of the base material 11. The front surface conductive layer 12 forms a mounting surface of the ceramic substrate 10 on which the semiconductor elements 21 and 22 are mounted. The back surface conductive layer 13 is made of copper, and is provided on a lower surface of the base material 11. The back surface conductive layer 13 forms a surface of the ceramic substrate 10 on a side opposite to the mounting surface thereof. Both the front surface conductive layer 12 and the back surface conductive layer 13 have a thickness of 0.8 mm, and formed by deposition by brazing.
The front surface conductive layer 12 of each of two ceramic substrates 10 includes a region on which the semiconductor elements 21 and 22 are mounted and a region for forming a circuit by a wire 41. Three groups of semiconductor elements 21 and 22 in six groups of semiconductor elements 21 and 22 constituting the 6in1 module are mounted on the front surface conductive layer 12 of each of two ceramic substrates 10 by the solder 30. The semiconductor element 21 is a diode made of silicon, and a size of the semiconductor element 21 is 13 mm in width, 10 mm in depth, and 0.2 mm in thickness. The semiconductor element 22 is an insulated gate bipolar transistor (IGBT) made of silicon, and a size thereof is 13 mm in width, 13 mm in depth, and 0.2 mm in thickness.
Two ceramic substrates 10A and 10B are described next. The ceramic substrate 10A (outline dimension 35 mm×65 mm) includes one front surface conductive layer 12 (outline dimension 31 mm×61 mm), and three groups of semiconductor elements 21 and 22 are mounted on one front surface conductive layer 12. The ceramic substrate 10B (outline dimension 45 mm×65 mm) includes four front surface conductive layers 12, and one group of semiconductor elements 21 and 22 is mounted on each of three large front surface conductive layers 12 (outline dimension 30 mm×19 mm).
A main terminal of each of the semiconductor elements 21 and 22 is connected to the external electrode 61 insert-formed in the case 5 by the wire 41 (0.4 in diameter) made of aluminum. A gate electrode 221 of the semiconductor element 22 and a signal electrode 63 insert-formed in the case 5 are wire-bonded by a wire 42 (0.15 in diameter) made of aluminum to form a circuit.
The sealing resin 82 is made of epoxy resin in which a silica filler is diffused.
Herein, the region corresponding to the portion in the back surface conductive layer 13 on which the semiconductor elements 21 and 22 are mounted indicates a region in the back surface conductive layer 13 facing the semiconductor elements 21 and 22 via the base material 11 and the front surface conductive layer 12.
Described next is another example and still another example of the ceramic substrate 10.
A process of manufacturing the power module 202 is described next.
As illustrated in
Next, as illustrated in
Finally, as illustrated in
As described above, the power module 202 according to the embodiment 1 includes: the semiconductor elements 21 and 22; the ceramic substrate 10 including the mounting surface on which the semiconductor elements 21 and 22 are mounted; and the fin base 70 bonded to the surface of the ceramic substrate 10 on the side opposite to the mounting surface, wherein the bonding region in the ceramic substrate 10 bonded to the fin base 70 is the region corresponding to the portion on which the semiconductor elements 21 and 22 are mounted, and the area of the bonding region in the ceramic substrate 10 bonded to the fin base 70 is smaller than the area of the portion on which the semiconductor elements 21 and 22 are mounted.
Accordingly, when the area of the bonding region in the ceramic substrate 10 bonded to the fin base 70 is reduced, the warpage of the fin base 70 caused by the heat stress can be suppressed.
The ceramic substrate 10 includes the back surface conductive layer 13 forming the surface on the side opposite to the mounting surface, and the back surface conductive layer 13 is formed in the region corresponding to the portion on which the semiconductor elements 21 and 22 are mounted. The area of the back surface conductive layer 13 can be reduced, thus a weight of the power module 202 can be reduced. According to the above configuration, increase of durability and reduction of an energy consumption amount of the power module 202 can be achieved.
In any case of
Herein, three groups of semiconductor elements 21 and 22 are mounted on each of two ceramic substrates 10A and 10B. It is considered to be effective to reduce the number of semiconductor elements 21 and 22 mounted on each ceramic substrate 10 to one or two to reduce the outline dimension of the ceramic substrate 10 as much as possible from a viewpoint of temperature cycle performance and a warpage in each ceramic substrate 10. However, a region (frame region) large enough to locate only the base material 11 to some extent is necessary in the peripheral edge part of the ceramic substrate 10 to ensure an insulation property for the fin base 70, thus if the ceramic substrate 10 is divided too much, the frame region in the whole ceramic substrate 10 is increased, and the whole power module 202 gets large. Thus, it is considered to be effective to locate two ceramic substrates 10 to achieve the outline dimension so that three groups of semiconductor element 21 and 22 can be mounted to each ceramic substrate 10.
A modification example of the embodiment 1 is described next.
As illustrated in
A height of the convex part 71 is 1.0 mm. The sealing resin 82 has low heat conductivity, thus when the convex part 71 is provided, a thickness of the sealing resin 82 filling the gap between the base material 11 and the base part 70a of the fin base 70 can be reduced. Accordingly, Joule heat occurring in a bonding position between the wire 41 and the front surface conductive layer 12 can be easily radiated.
As illustrated in
The case 5 has a size different from that in the embodiment 1. The size of the case 5 is 70 mm in width, 120 mm in depth, and 6 mm in thickness.
In the fin base 70, the base part 70a has a size different from that in the embodiment 1. The size of the base part 70a is 70 mm in width, 120 mm in depth, and 3 mm in thickness.
Each of three ceramic substrates 10 has two front surface conductive layers 12 (outline dimension 41 mm×32 mm). Two groups of semiconductor elements 21 and 22 are mounted on each of two front surface conductive layers 12 in three ceramic substrates 10.
As illustrated in
Herein, two groups of semiconductor elements 21 and 22 are mounted on each of three ceramic substrates 10A, 10B, and 10C. It is considered to be effective to reduce the number of semiconductor elements 21 and 22 mounted on each ceramic substrate 10 to one or two to reduce the outline dimension of the ceramic substrate 10 as much as possible from a viewpoint of temperature cycle performance and a warpage in each ceramic substrate 10. However, a region (frame region) large enough to locate only the base material 11 to some extent is necessary in the peripheral edge part of the ceramic substrate 10 to ensure an insulation property for the fin base 70, thus when the ceramic substrate 10 is divided too much, the frame region in the whole ceramic substrate 10 is increased, and the whole power module 202 gets large. Thus, it is considered to be effective to locate three ceramic substrates 10 to achieve the outline dimension so that two groups of semiconductor element 21 and 22 can be mounted to each ceramic substrate 10.
The power module 202 according to an embodiment 2 is described next.
As illustrated in
As described above, in the power module 202 according to the embodiment 2, the ceramic substrate 10 includes the back surface conductive layer 13 forming the surface on the side opposite to the mounting surface, and the solder resist 131 is formed in the region in the back surface conductive layer 13 other than the region corresponding to the portion on which the semiconductor elements 21 and 22 are mounted so that the region is not bonded to the fin base 70.
Accordingly, the region in the back surface conductive layer 13 other than the region corresponding to the portion on which the semiconductor elements 21 and 22 are mounted is not bonded to the base part 70a of the fin base 70. When the area of the bonding area in the ceramic substrate 10 bonded to the fin base 70 is reduced, the warpage of the fin base 70 caused by the heat stress can be suppressed.
The convex part 71 in the modification example of the embodiment 1 may be provided to have contact with the region in which the solder resist 131 is formed in the ceramic substrate 10. Also in this case, the heat radiation property of Joule heat occurring in the bonding position between the wire 41 and the front surface conductive layer 12 can be improved.
The power module 202 according to an embodiment 3 is described next.
As illustrated in
As described above, in the power module according to the embodiment 3, the ceramic substrate 10 includes the back surface conductive layer 13 forming the surface on the side opposite to the mounting surface, and the back surface conductive layer 13 is divided into the first region 13a as the region corresponding to a portion on which the semiconductor elements 21 and 22 are mounted and the second region 13b as the other region by the slit 13c.
Accordingly, a difference of area between the front surface conductive layer 12 and the back surface conductive layer 13 is reduced, and the bonding area in the ceramic substrate 10 bonded to the fin base 70 can be reduced without an additional process such as a case of forming the solder resist 131.
The convex part 71 in the modification example of the embodiment 1 may be provided to have contact with the second region 13b. Also in this case, the heat radiation property of Joule heat occurring in the bonding position between the wire 41 and the front surface conductive layer 12 can be improved.
In the above description, the base material 11 is made of aluminum nitride, however, a similar effect is obtained even when the base material 11 is made of silicon nitride or alumina. In the above description, the front surface conductive layer 12 and the back surface conductive layer 13 are made of copper, however, a similar effect is obtained even when they are made of aluminum by reforming surfaces thereof to be solder-wetted by nickel plating, for example.
In the above description, the fin base 70 is made of aluminum alloy, however, a similar effect is obtained even when the fin base 70 is made of copper or copper alloy. In the above description, the semiconductor elements 21 and 22 are made of silicon, however, a similar effect is obtained even when they are wide bandgap semiconductor such as silicon carbide and gallium nitride.
In the above description, the solder 30 is made of 96.5% tin, 3% silver, and 0.5% copper, and a melting point of the solder 30 is 217° C., however, a similar effect is obtained even when the solder 30 is made of 99.3% tin and 0.7% copper, and a melting point is 224° C., or when the solder 30 is made of 95% tin and 5% antimony, and a melting point is 240° C.
A similar effect is obtained even when the solder 30 is partially replaced with a bonding material other than the solder such as a silver epoxy adhesive agent, a silver sintering material, or a brazing material.
In the above description, the wires 41 and 42 are made of aluminum, however, a similar effect is obtained even when they are made of copper or aluminum alloy containing a slight amount of additive such as iron.
A similar effect is obtained by performing soldering on the upper surfaces of the semiconductor elements 21 and 22 using a copper frame to form the circuit in place of forming the circuit by wire bonding using the wires 41 and 42.
In the above description, the case 5 is made of PPS, it is also possible to improve heat resistance by replacing the material of the case 5 with liquid crystal polymer (LCP).
In the above description, the external electrode 61 and the signal electrode 63 are the copper frames, however, a similar effect is obtained even when nickel plating is appropriately applied thereon or they are replaced with copper alloy frames or nickel-plating aluminum frames.
In the above description, the sealing resin 82 is made of epoxy resin in which a silica filler is diffused, however, a filler such as alumina may be diffused in place of the silica filler, or a similar effect is obtained even when the sealing resin 82 is made of epoxy resin in which silicone resin is mixed. A similar effect is obtained even when the sealing resin 82 is made of only silicone resin.
Applied in the present embodiment is the power module 202 according to the embodiments 1 to 3 described above to a power conversion apparatus. Application of the power module 202 according to the embodiments 1 to 3 is not limited to a specific power conversion apparatus, however, described hereinafter as an embodiment 4 is a case of applying the power module 202 according to the embodiments 1 to 3 to a three-phase inverter.
A power conversion system illustrated in
The power conversion apparatus 200 is a three-phase inverter connected between the power source 100 and the load 300, converts a direct current power supplied from the power source 100 into an alternating current power, and supplies the alternating current power to the load 300. As illustrated in
The load 300 is a three-phase electrical motor driven by the alternating current power supplied from the power conversion apparatus 200. The load 300 is not for a specific purpose of usage, but is an electrical motor mounted on various types of electrical apparatuses, thus is used as an electrical motor for a hybrid automobile, an electrical automobile, a railroad vehicle, an elevator, or an air-conditioning machine, for example.
Details of the power conversion apparatus 200 are described hereinafter. The main conversion circuit 201 includes a switching element (not shown) and a reflux diode (not shown), and when the switching element is switched, the main conversion circuit 201 converts the direct current power supplied from the power source 100 into the alternating current power, and supplies the alternating current power to the load 300. Examples of a specific circuit configuration of the main conversion circuit 201 include various configurations, however, the main conversion circuit 201 according to the present embodiment is a three-phase full-bridge circuit with two levels, and can be made up of six switching elements and six reflux diodes antiparallelly connected to each switching element. At least one of each switching element and each reflux diode of the main conversion circuit 201 is made up of the power module 202 corresponding to any one of the embodiments 1 to 3 described above. Six switching elements are connected two by two in series to constitute upper and lower arms, and each pair of the upper and lower arms constitutes each phase (U phase, V phase, and W phase) of a full-bridge circuit. Output terminals of the pair of the upper and lower arms, that is to say, three output terminals of the main conversion circuit 201 are connected to the load 300.
The main conversion circuit 201 includes a drive circuit (not shown) driving each switching element, however, the drive circuit may be built in the power module 202, or also applicable is a configuration that the drive circuit is provided separately from the power module 202. The drive circuit generates a drive signal for driving a switching element of the main conversion circuit 201, and supplies the drive signal to a control electrode of the switching element of the main conversion circuit 201. Specifically, the drive circuit outputs a drive signal for making the switching element enter an ON state and a drive signal for making the switching element enter an OFF state to a control electrode of each switching element in accordance with a control signal from the control circuit 203 describe hereinafter. When the switching element is kept in the ON state, the drive signal is a voltage signal (ON signal) larger than a threshold voltage of the switching element, and when the switching element is kept in the OFF state, the drive signal is a voltage signal (OFF signal) smaller than the threshold voltage of the switching element.
The control circuit 203 controls the switching element of the main conversion circuit 201 so that a desired electrical power is supplied to the load 300. Specifically, the control circuit 203 calculates a time (on time) at which each switching element of the main conversion circuit 201 should enter the ON state based on the electrical power to be supplied to the load 300. For example, the control circuit 203 can control the main conversion circuit 201 by PWM control modulating the on time of the switching element in accordance with the voltage to be outputted. Then, the control circuit 203 outputs to a control command (control signal) to the drive circuit so that the ON signal is outputted to the switching element which should enter the ON state and the OFF signal is outputted to the switching element which should enter the OFF state at each point of time. The drive circuit outputs the ON signal or the OFF signal as the drive signal to the control electrode of each switching element in accordance with the control signal.
In the power conversion apparatus according to the present embodiment, the power module 202 according to the embodiments 1 to 3 is applied as the switching element and the reflux diode of the main conversion circuit 201, thus reduction of weight, increase of durability, and reduction of an energy consumption amount can be achieved.
Described in the present embodiment is the example of applying the power module 202 according to the embodiments 1 to 3 to three-phase inverter with two levels. However, the power module 202 according to the embodiments 1 to 3 is not limited thereto, but can be applied to various power conversion apparatuses. In the present embodiment, the power conversion apparatus with two levels is applied, however, a power conversion apparatus with three or multi levels may be applied, or the power module 202 according to the embodiments 1 to 3 may be applied to a single-phase inverter when the electrical power is supplied to a single-phase load. When the electrical power is supplied to a direct current load, for example, the power module 202 according to the embodiments 1 to 3 can be applied to a DC/DC converter or an AC/DC converter.
The power conversion apparatus to which the power module 202 according to the embodiments 1 to 3 is applied can be used not only in the case where the load described above is the electrical motor but can be used as a power source apparatus of an electrical discharge machine, a laser beam machine, an induction heat cooking machine, or a wireless power supply system, and further can also be used as a power conditioner of a solar power system or an electricity storage system, for example.
Although the present disclosure is described in detail, the foregoing description is in all aspects illustrative and does not restrict the disclosure. It is therefore understood that numerous modification examples can be devised.
Each embodiment can be arbitrarily combined, or each embodiment can be appropriately modified or omitted.
The aspects of the present disclosure are collectively described hereinafter as appendixes.
A power module, comprising:
The power module according to Appendix 1, wherein
The power module according to Appendix 1, wherein
The power module according to Appendix 1, wherein
The power module according to Appendix 1, wherein
The power module according to Appendix 1, wherein
A power conversion apparatus, comprising:
10, 10A, 10B, 10C ceramic substrate, 13 back surface conductive layer, 13a first region, 13b second region, 13c slit, 21, 22, semiconductor element, 70 fin base, 71 convex part, 131 solder resist, 200 power conversion apparatus, 201 main conversion circuit, 202 power module, 203 control circuit.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-062224 | Apr 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/010614 | 3/17/2023 | WO |
