Patent Application
20200303273
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2019-052340, filed on Mar. 20, 2019; the entire contents of which are incorporated herein by reference.
Embodiments relate to a power module.
Conventionally, a power module that controls a current has been developed, and includes a substrate fixed inside a housing, and power semiconductor elements mounted to the substrate; electrodes of the power semiconductor elements are drawn out of the housing by a metal plate terminal; and a gel material is filled into the housing. It is desirable for such a power module to have high reliability for the thermal load generated when repeatedly conducting/blocking.
A power module according to an embodiment includes a housing including an external terminal exposed at an outer surface of the housing, a substrate provided inside the housing, a semiconductor element mounted to the substrate, a wire connected to the semiconductor element, a metal plate terminal provided inside the housing, and a gel material provided inside the housing; the metal plate terminal connects the external terminal to an electrode of the semiconductor element; and the gel material covers the wire, the semiconductor element, the substrate, and a portion of the metal plate terminal. The metal plate terminal includes a first portion disposed inside the gel material between the wire and a top plate of the housing, a second portion bent with respect to the first portion and connected to the electrode of the semiconductor element, and a third portion extending from an end portion of the first portion toward the substrate.
A first embodiment will now be described.
The drawings are schematic; and the components are not illustrated or emphasized as appropriate. This is similar for the other drawings described below as well. For example, in
As shown in
Multiple external terminals 14 are provided at the top plate 13. The external terminals 14 are exposed at the outer surface of the housing 10. Through-holes 15 are formed to pierce the top plate 13 and the external terminals 14. Although the direction from the bottom plate 11 toward the top plate 13 is called “up” and the direction from the top plate 13 toward the bottom plate 11 is called “down” hereinbelow, these expressions are for convenience and are independent of the direction of gravity. “Up” and “down” also are generally referred to as the “vertical direction.”
For example, an insulative substrate 20 is provided on the bottom plate 11. Multiple semiconductor elements 21 are mounted on the upper surface of the substrate 20. The semiconductor element 21 is, for example, a power semiconductor element, e.g., a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), an IGBT (Insulated Gate Bipolar Transistor), a bipolar transistor, a diode, etc. The major semiconductor material that is used to form the semiconductor element 21 is, for example, silicon carbide (SiC) or silicon (Si). For example, two or three electrodes 22 are provided on each semiconductor element 21. Wires 23 are connected between the electrodes 22 of the different semiconductor elements 21. Loops are formed in the wires 23 above the semiconductor elements 21.
For example, three metal plate terminals 30 are provided inside the housing 10. Only one metal plate terminal 30 is illustrated in
Planar portions 31 to 37 are provided as one body in the metal plate terminal 30. The planar portions 31 to 35 are consecutively arranged in this order. The planar portion 31 is positioned between the side plate 12 and the top plate 13 of the housing 10 and is connected to the external terminals 14 via bolts 16 inserted into the through-holes 15. In the specification, a “connection” means an electrical connection.
The planar portion 32 is bent to extend downward from the end edge of the planar portion 31 inside the housing 10. The planar portion 33 is bent to extend in a direction (hereinbelow, called the “horizontal direction”) parallel to the upper surface of the substrate 20 from the lower end edge of the planar portion 32. The planar portion 34 extends downward from the end edge of the planar portion 33 at the side opposite to the boundary between the planar portion 33 and the planar portion 32. The planar portion 35 is bent to extend in the horizontal direction from the lower end edge of the planar portion 34 and is connected to the electrode 22 of the semiconductor element 21. Thus, the metal plate terminal 30 connects the external terminals 14 to the electrodes 22 of the semiconductor elements 21.
The planar portion 36 of the metal plate terminal 30 is bent to extend obliquely downward from one of the two end edges of the planar portion 33 other than the end edge continuous with the planar portion 32 and the end edge continuous with the planar portion 34. The tip of the planar portion 36 is a free end. Similarly, the planar portion 37 is bent to extend obliquely downward from the other of the two end edges described above. The tip of the planar portion 37 is a free end. For example, the planar portions 36 and 37 are tilted to extend away from each other downward.
The planar portions 36, 33, and 37 are consecutively arranged in this order. Therefore, the planar portion 32 that extends upward, the planar portion 36 that extends obliquely downward, the planar portion 34 that extends downward, and the planar portion 37 that extends obliquely downward are positioned in four mutually-orthogonal directions when viewed from the planar portion 33 spreading in the horizontal direction.
The wires 23 are disposed in the region directly under the planar portion 33, that is, between the substrate 20 and the planar portion 33. In other words, the planar portion 33 is disposed between the top plate 13 and the wires 23.
A gel material 40 is sealed inside the housing 10. The gel material 40 covers the substrate 20, the semiconductor elements 21, and the wires 23. The gel material 40 also covers the lower portion of the planar portion 32 of the metal plate terminal 30 and the entirety of each of the planar portions 33 to 37. The gel material 40 is insulative; and the elastic modulus of the gel material 40 is lower than the elastic modulus of a metal. The gel material 40 is made of, for example, a silicone gel. The breakage of the wires 23 due to thermal stress can be suppressed by the gel material 40. Also, the insulative properties between the metal plate terminals 30, between the wires 23, between the metal plate terminal 30 and the wires 23, etc., can be ensured by the gel material 40. Also, the substrate 20, the semiconductor elements 21, the wires 23, etc., are protected by the gel material 40 from oxygen, moisture, fine particles, etc., entering the housing 10 from the outside.
The gel material 40 does not fill the entire interior of the housing 10; and an air layer 41 exists on the gel material 40 inside the housing 10. The housing 10 is not in a perfectly airtight state; and the air of the air layer 41 can flow in and out of the housing 10. The gel material 40 deforms easily, but is a solid formed as one body and does not leak externally through gaps of the housing 10.
An operation of the power module according to the embodiment will now be described.
When electrical power is supplied to the power module 1 and the semiconductor elements 21 conduct, the semiconductor elements 21 generate heat; and the temperature of the entire power module 1 rises. Accordingly, each member of the power module 1 undergoes thermal expansion; but the thermal expansion coefficient is different between the members. The thermal expansion coefficient of the gel material 40 is larger than the thermal expansion coefficient of the housing 10 and the thermal expansion coefficient of the metal plate terminal 30. Therefore, when the temperature of the power module 1 rises, the increase rate of the volume of the gel material 40 becomes larger than the increase rate of the volume of the housing 10; and the upper surface of the gel material 40 rises. When the conduction of the power module 1 stops, the temperature of the power module 1 decreases from the high temperature to room temperature. Thereby, the volume of the gel material 40 decreases; and the upper surface of the gel material 40 drops.
In the power module 101 according to the comparative example as shown in
Thus, as the heating and the cooling of the power module 101 repeats as the power module 101 operates, a shear force is repeatedly applied to the gel material 40; and cracks occur in the gel material 40. As a result, the support effect of the wires 23, the insulation effect of the metal plate terminals 30 and the wires 23, and the protection effect from the external environment which are provided by the gel material 40 decrease; the likelihood of dielectric breakdown occurring between the metal plate terminals 30 increases; and the reliability of the power module 101 undesirably decreases.
Conversely, in the power module 1 according to the embodiment as shown in
Accordingly, compared to the comparative example, the shear force that is applied to the gel material 40 by the metal plate terminal 30 is small in the embodiment. Therefore, in the power module 1, the occurrence of the cracks in the gel material 40 can be suppressed. As a result, the reliability of the power module 1 according to the embodiment is high.
By disposing the planar portion 33 at a constant height in the power module 1 according to the embodiment, a space for forming the loops of the wires 23 can be ensured between the substrate 20 and the planar portion 33. Therefore, contacting and shorting of the wires 23 to the planar portion 33 can be prevented.
A second embodiment will now be described.
As shown in
The rigidity of the low-rigidity plate 51 is lower than the rigidity of the planar portion 33 of the metal plate terminal 30. For example, the Young's modulus of the material of the low-rigidity plate 51 is lower than the Young's modulus of the material of the metal plate terminal 30. The low-rigidity plate 51 is made of, for example, a resin material and is made of, for example, PET (PolyEthylene Terephthalate).
For example, the low-rigidity plate 51 is bonded to the upper surface of the planar portion 33 of the metal plate terminal 30 by bonding, fastening by bolts, etc. When viewed from above, the low-rigidity plate 51 is larger than the planar portion 33; and end portions 51a of the low-rigidity plate 51 jut from the end portions 33a of the planar portion 33.
An operation of the power module according to the embodiment will now be described.
As described above, when viewed from above in the power module 2, the end portions 51a of the low-rigidity plate 51 jut from the end portions 33a of the planar portion 33. Therefore, when the gel material 40 moves vertically due to the thermal cycles, the gel material 40 moves to flow around the end portions 51a of the low-rigidity plate 51 without flowing around the end portions 33a of the planar portion 33.
As shown in
The material of the low-rigidity plate 51 may be the same as the material of the metal plate terminal 30; and the thickness of the low-rigidity plate 51 may be thinner than the thickness of the planar portion 33 of the metal plate terminal 30. The rigidity of the low-rigidity plate 51 is caused to be lower than the rigidity of the planar portion 33 thereby; and the effects described above can be obtained. The low-rigidity plate 51 may be bonded to the lower surface of the planar portion 33.
Otherwise, the configuration, the operations, and the effects of the embodiment are similar to those of the first embodiment.
A third embodiment will now be described.
As shown in
It is favorable for the partition plate 61 to be made of an insulating material; and the partition plate 61 is made of, for example, a resin material. The partition plate 61 has a configuration in which one rectangular plate is bent into a C-shape. More specifically, vertical portions 63 and 64 that extend downward from two sides of a horizontal portion 62 are provided as one body with the horizontal portion 62 in the partition plate 61.
For example, the horizontal portion 62 is bonded to the upper surface of the planar portion 33 of the metal plate terminal 30 by fixing by a bonding agent, an adhesive sheet, fastening by bolts, etc. When viewed from above, the configuration of the horizontal portion 62 is substantially the same as the configuration of the planar portion 33 or slightly larger. The vertical portions 63 and 64 are bent from the horizontal portion 62 to cover the end portions 33a at the two sides of the planar portion 33. For example, the lower ends of the vertical portions 63 and 64 do not reach the substrate 20. A space 65 between the planar portion 33 and the substrate 20 is partitioned from the periphery by the planar portions 33 and 34 of the metal plate terminal 30, the vertical portions 63 and 64 of the partition plate 61, and a portion of the side plate 12 of the housing 10.
An operation and effects of the power module according to the embodiment will now be described.
In the embodiment as shown in
In other words, when the power module 3 is heated, the gel material 40 expands; but the planar portions 33 and 34, the vertical portions 63 and 64, and the side plate 12 impede the upward movement of the portion 40a of the gel material 40 disposed inside the space 65. On the other hand, the portions 40b of the gel material 40 disposed outside the space 65 move upward along the surfaces of the vertical portions 63 and 64 of the partition plate 61. At this time, the vertical portions 63 and 64 are substantially not interposed in the movement path of the portions 40b; therefore, the vertical portions 63 and 64 substantially do not apply shear forces to the portions 40b of the gel material 40. Therefore, the occurrence of the cracks in the gel material 40 can be suppressed.
Because the partition plate 61 is insulative, shorts do not occur even when the partition plate 61 contacts the wires 23 and the electrodes 22 of the semiconductor elements 21.
The horizontal portion 62 of the partition plate 61 may be adhered to the lower surface of the planar portion 33 of the metal plate terminal 30.
Otherwise, the configuration, the operations, and the effects of the embodiment are similar to those of the first embodiment.
A fourth embodiment will now be described.
As shown in
Similarly to the partition plate 61, it is favorable for the partition plate 66 to be made of an insulating material; and the partition plate 66 is made of, for example, a resin material. Although the partition plate 66 also has a configuration in which one rectangular plate is bent into a C-shape, the direction of the bend is different from that of the partition plate 61. Vertical portions 67, 68, and 69 are provided as one body in the partition plate 66.
For example, the vertical portion 67 of the partition plate 66 is bonded to the surface of the planar portion 34 of the metal plate terminal 30 at the side opposite to the planar portion 33 by being fixed by a bonding agent, an adhesive sheet, fastening by bolts, etc. For example, the lower end of the vertical portion 67 does not reach the substrate 20. The vertical portions 68 and 69 are bent from the two horizontal-direction end portions of the vertical portion 67 toward the planar portion 32. A space that corresponds to the region directly under the planar portion 33 of the metal plate terminal 30, i.e., the space 65 between the planar portion 33 and the substrate 20, is partitioned from the periphery by the planar portions 33 and 34 of the metal plate terminal 30, the vertical portions 68 and 69 of the partition plate 66, and a portion of the side plate 12 of the housing 10.
The vertical portion 67 of the partition plate 66 may be bonded to the surface of the planar portion 34 of the metal plate terminal 30 at the planar portion 33 side.
Otherwise, the configuration, the operations, and the effects of the embodiment are similar to those of the third embodiment.
A first test example will now be described.
In the test example, the effects of the height of the planar portion 33 of the metal plate terminal 30, i.e., the distance from the bottom plate 11, on the strain of the gel material 40 were verified.
As shown in
The strain that is generated in each portion of the gel material 40 for the power module 101 shown in
Such a simulation was performed multiple times for different heights of the planar portion 33. As shown in
A second test example will now be described.
In the test example, the effects of the existence of the partition plate in the third and fourth embodiments on the strain of the gel material was verified.
The model shown in
As shown in
According to the embodiments described above, a power module that has high reliability can be realized.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-052340 | Mar 2019 | JP | national |
