Power semiconductor device

Abstract

To provide a power semiconductor device that suppresses a void and a cracking that occurs in an insulation material when water entered into an internal part of a device is immersed into the insulation material when it is heated, and prevent a partial discharge and an insulation damage.SOLUTION: A power semiconductor device 100A comprises: an insulation substrate 2a onto which a power semiconductor element 1 is mounted onto one surface; a heat radiation base plate 3 that is bonded to a surface of an insulation circuit board 2 on the side opposite to a surface where a power semiconductor element 1 is mounted; a case 4 that is fixed to the heat radiation base plate 3, and surrounds the insulation substrate 2a; an insulation material 5 that insulates and seals the power semiconductor element 1 and the insulation substrate 2a in an inner side of the case 4; and a lid 6 that is integrally formed with the case 4, or a lid 6 that is fixed to the case 4 by bonding means. A ventilation hole 50 having a porous material is provided to at least one part of a portion that is not contacted to the case 4 or the insulation material 5 of the lid 6.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power semiconductor device. [Background technology]

[0002] In recent years, environmental and resource issues on a global scale have come into the spotlight, and in order to utilize resources effectively, promote energy conservation, and reduce greenhouse gas emissions, high-efficiency power conversion devices, such as inverter devices that use switching of power semiconductor elements, have been attracting attention. These power conversion devices are being widely applied to a wide range of applications, including home appliances such as refrigerators and air conditioners, industrial machinery, hybrid electric vehicles (HEVs), electric vehicles (EVs), railways, and power and social infrastructure-related equipment.

[0003] A power conversion device is composed of many parts, such as a power semiconductor device (power module) with built-in power semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors), bus bars, capacitors, inductors, various sensors, and control circuits. Small and reliable power conversion devices are required to reduce the installation space and ensure safety. To achieve this, it is important to reduce the size and improve the reliability of power semiconductor devices, which are the main components of power conversion devices.

[0004] Currently, IGBTs and diodes made mainly of Si are used as power semiconductor elements in power semiconductor devices. As mentioned above, power semiconductor devices are becoming smaller and have larger capacities, and this is leading to a demand for stable operation at high temperatures. Power semiconductor elements are also required to have "high voltage resistance," "low on-resistance," and "high-speed switching" characteristics. SiC, which has a dielectric breakdown field strength 10 times that of Si and a band gap three times that of Si, has begun to be applied as a next-generation power semiconductor element and is expected to become widespread. This next-generation power semiconductor element will be able to be used at even higher temperatures than Si devices, so power semiconductor devices require high reliability at high temperatures.

[0005] For example, Patent Document 1 is a power semiconductor device that aims to achieve high reliability in high-temperature operation. Patent Document 1 discloses a power semiconductor device in which a lead pin block has a base portion on which many lead pins stand, a lid receiving step portion, an engagement claw portion that engages with an engagement claw portion on the inner surface of the frame portion, a guide pin portion that is inserted into a guide hole of a female connector of the lead pin during use, and an air vent hole that penetrates the base portion in the thickness direction from a recess in the lid receiving step portion to the step portion of the engagement claw portion. In Patent Document 1, when the lead pin block is dropped onto the inner surface of the frame portion and the engagement claw portion is engaged with the engagement claw portion, the block is tightly held in place and is prevented from falling out, but the gap between the block and the frame portion is closed by a seal member. The internal space of the case is in communication with the outside air through the air vent hole.

[0006] According to the configuration of Patent Document 1, when the lead pin block is inserted into the frame and assembled, the fitting gap with the frame is blocked by a seal member on the inner space side, so that even if the temperature of the gel resin sealant rises due to heating for fixing the insulating cover to the insulating case frame or heat generation from the semiconductor element, causing the gel resin sealant to thermally expand, the gel resin sealant will not seep out from the gap. In addition, when the gel resin sealant expands, the air pressure of the residual air in the inner space increases, but since an air vent hole is formed, the internal pressure does not increase and the gel resin sealant can be allowed to expand freely. This is said to suppress the occurrence of excessive thermal stress and improve reliability.

[0007] Patent Document 2 also discloses a power semiconductor device that will not break even if the volume of the soft sealing material expands due to heat generation during testing or operation, and has a case to which a substrate used as a bottom plate is attached, a semiconductor element and electrical connection members are attached to the side of the substrate facing the inside of the case, a soft sealing material is injected into the case, and a hard sealing material is injected on top of that.The power semiconductor device has a compensation space connected to the space inside the case into which the soft sealing material is injected, and is formed so that the soft sealing material expands into the compensation space when the temperature rises, and the compensation space is connected to the atmosphere surrounding the power semiconductor device through an opening provided in the case.

[0008] According to the configuration of Patent Document 2, by providing a compensation space inside, the soft sealing member can expand in volume, and it is possible to prevent high pressure that may damage the power semiconductor device from occurring inside the power semiconductor device. It is also considered preferable to provide an opening in the wall of the case that forms the compensation space, thereby communicating the air inside the compensation space with the outside air surrounding the device, so that the power semiconductor device can breathe.

[0009] The power semiconductor devices of Patent Document 1 and Patent Document 2 described above both have a substrate with a semiconductor element mounted inside a case, the semiconductor element and substrate are insulated and sealed with a gel resin sealant, and have a structure in which an air hole ("air vent hole" in Patent Document 1, "opening" in Patent Document 2) is formed in a part of the case or in a part of the lead pin block. It is said that this prevents overflow from gaps and rise in internal pressure due to volume expansion of the gel resin sealant when the semiconductor element is operating and generates heat, and suppresses the occurrence of excessive thermal stress.

[0010] Meanwhile, in the shipping test of a power semiconductor device in which a board carrying a power semiconductor element is bonded to a heat dissipating base plate with a bonding material such as solder, there is a process for inspecting the bonding state between the heat dissipating base plate and the board. The power semiconductor device is immersed in water, and ultrasonic waves are used to inspect whether there are any solder voids or sink marks at the bonding interface between the heat dissipating base plate and the board. This is an important inspection for confirming the heat dissipation of the power semiconductor element to the base plate and the reliability of the power semiconductor device. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 8-162571 [Patent Document 2] Japanese Patent Application Publication No. 63-28052 Summary of the Invention [Problem to be solved by the invention]

[0012] In the above-mentioned techniques of Patent Document 1 and Patent Document 2, water may enter the inside of the device through a vent hole formed in a part of the case or a part of the lead pin block. The water that has entered the device causes the inside of the device to become a high-temperature and high-humidity state due to heating such as a high-temperature blocking test, which is also performed in the inspection process, and the water vapor permeates into the gel resin sealant. Also, the water that has permeated into the gel resin sealant vaporizes to form voids and cracks in the gel resin sealant. Thereafter, when a high voltage is applied in a partial discharge test or a withstand voltage test, partial discharge may occur or insulation breakdown may occur. In conventional power semiconductor devices, it was necessary to improve these points.

[0013] A power semiconductor device is used by being incorporated into a power conversion device. In this case, depending on the housing structure of the power conversion device and the environment in which it is used, it is expected that water such as rainwater or condensation water may get on the power semiconductor device. In the techniques of Patent Documents 1 and 2, it is expected that water may infiltrate into the device under the usage environment through a vent hole formed in a part of the case or a part of the lead pin block. Moisture that has infiltrated inside the device may reduce the insulation and reliability of the device, and this point also needed to be improved.

[0014] The present invention has been made in consideration of the above circumstances, and aims to provide a power semiconductor device that prevents partial discharge and dielectric breakdown by suppressing the penetration of moisture that has entered the device into the insulating material and the generation of voids and cracks in the insulating material when heated. [Means for solving the problem]

[0015] In order to solve the above problems, the power semiconductor device of the present invention is a semiconductor device comprising an insulating substrate having a semiconductor element mounted on one side thereof, a heat dissipation base joined to the surface opposite to the surface on which the semiconductor element is mounted, a case fixed to the heat dissipation base and surrounding the insulating substrate, an insulating material that insulates and seals the semiconductor element and the insulating substrate inside the case, and a lid formed integrally with the case or a lid fixed to the case by a joining means, and is characterized in that at least a portion of the portion of the case or the lid that is not in contact with the insulating material is provided with an air vent having a porous material. Effect of the Invention

[0016] According to the present invention, partial discharge and dielectric breakdown can be prevented by suppressing the penetration of moisture that has entered the device into the insulating material and the generation of voids and cracks in the insulating material when heated. [Brief description of the drawings]

[0017] [Figure 1] 1 is a plan view showing a structure of a power semiconductor device according to a first embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view of FIG. 1 along AA'. [Diagram 3] 1 is a circuit diagram illustrating an operation of a power semiconductor device according to an embodiment of the present invention. [Figure 4] FIG. 1 is a circuit diagram showing a configuration example of a protection circuit connected to an input side of a conventional internal circuit. [Diagram 5] 5 is a cross-sectional view showing an example of the structure of an internal circuit and a protection circuit shown in FIG. 4. [Figure 6] FIG. 11 is a cross-sectional view showing a structure of a power semiconductor device of a comparative example. [Figure 7A] FIG. 1 is a table showing the results of reliability tests of the power semiconductor devices according to the first to fifth embodiments and the power semiconductor device of the comparative example. [Figure 7B] FIG. 1 is a table showing the results of reliability tests of the power semiconductor devices according to the first to fifth embodiments and the power semiconductor device of the comparative example. [Figure 7C]FIG. 1 is a table showing the results of reliability tests of the power semiconductor devices according to the first to fifth embodiments and the power semiconductor device of the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. (First embodiment) 1 is a cross-sectional view showing the structure of a power semiconductor device according to a first embodiment of the present invention. This embodiment is an example in which the semiconductor device is applied to a power semiconductor device including a power semiconductor element. As shown in FIG. 1, the power semiconductor device 100A comprises an insulating circuit board 2 having a power semiconductor element 1 mounted on one side thereof, a heat dissipating base plate 3 (heat dissipating base) joined to the surface of the insulating circuit board 2 opposite to the surface on which the power semiconductor element 1 (semiconductor element) is mounted, a case 4 fixed to the heat dissipating base plate 3 and surrounding the insulating board 2a, a gel-like insulating material 5 that insulates and seals the power semiconductor element 1 and the insulating circuit board 2 inside the case 4, and a lid 6 that covers the entire upper part of the power semiconductor device 100A and is fixed to the case 4, and at least a portion of the portion of the lid 6 that is not in contact with the insulating material 5 is provided with an air vent 50 having a porous material.

[0019] The ventilation hole 50 has a hole 11 opened in the case 4 or the lid 6, and a gas-permeable waterproof layer 7 that allows air to pass but not water, arranged to cover the hole 11. This embodiment is an example in which the ventilation hole 50 is provided in a part of the lid 6, but it is also possible to provide the ventilation hole 50 in the case 4.

[0020] The gas-permeable waterproof layer 7 is a moisture-permeable waterproof membrane that allows air to pass through but not water. The gas-permeable waterproof layer 7 is a porous material made of resin, ceramic, or metal. The pore size of the porous material is in the range of 0.01 μm to 100 μm (described later).

[0021] A method for manufacturing the power semiconductor device 100A configured as above will now be described. As shown in FIG. 1, an insulating circuit board 2 of a power semiconductor device 100A has a circuit electrode 2b bonded to one surface of an insulating board 2a and a back electrode 2c bonded to the other surface thereof via a brazing material 2d.

[0022] The insulating substrate 2a is selected from the following depending on the normal element withstand voltage of the power semiconductor device 100A. That is, for the power semiconductor device 100A with a normal element withstand voltage of 1200V or more, ceramics such as aluminum oxide, aluminum nitride, and silicon nitride are used for the insulating substrate 2a. Also, for the power semiconductor device 100A with an element withstand voltage of less than 1200V, a highly thermally conductive resin substrate in which a highly thermally conductive filler is dispersed in an organic resin is used. In the case of a highly thermally conductive resin substrate, the circuit electrode 2b and the back electrode 2c are bonded to the substrate by the adhesive force of the resin, so no brazing material is used.

[0023] The circuit electrodes 2b are formed into a circuit shape required for the circuit operation of the power semiconductor device 100A using a technique such as etching. First, the power semiconductor element 1 is bonded onto the circuit electrode 2b of the insulating circuit board 2 via a bonding material 8 such as solder or sintered metal. Next, the electrodes of the power semiconductor element 1 and the circuit electrode 2b of the insulating circuit board 2 are connected using thin metal wires such as aluminum to form a necessary circuit (thin metal wires are omitted in FIG. 1). Then, the heat dissipating base plate 3 and the back electrode of the circuit insulating board 2 are bonded via a bonding material 9 such as solder. Then, an adhesive is applied to the outer periphery of the heat dissipating base plate 3 to fix the case 4 and the heat dissipating base plate 3. In addition to the adhesive, the heat dissipating base plate 3 and the case 4 may be fixed with screws (adhesive and screws are omitted in the drawing). Then, a terminal 10 is bonded onto the circuit electrode 2b of the insulating circuit board 2 using a technique such as ultrasonic waves.

[0024] Thereafter, the lid 6 is placed on the top of the power semiconductor device 100A, and the case 4 and the lid 6 are bonded and fixed with an adhesive. Here, the lid 6 is formed in advance with a hole 11 (a gas-permeable waterproof layer 7 is formed in this hole 11 later) so that the gel insulating material can be injected into the inside of the device. The gel insulating material 5 is then injected from the hole 11, and the gel insulating material 5 is cured under predetermined curing conditions. Silicone gel is generally used as the gel insulating material 5, but other resins other than silicone may be used as long as they have insulating properties. Finally, an adhesive (jointing means) is applied around the hole 11 of the lid 6, and a gas-permeable waterproof layer 7 that allows air to pass through but not water is adhered and fixed to the hole 11 to complete the power semiconductor device 100A. That is, in FIG. 1, the lid 6 is fixed with an adhesive (not shown) that is a jointing means, but the case 4 and the lid 6 may be formed integrally. The material of the case 4 and the lid 6 is, for example, a metal material. In the case of a metal material, the case 4 and the lid 6 may be fixed by welding.

[0025] For the gas-permeable waterproof layer 7 of the power semiconductor device 100A, a porous metal body made of stainless sintered metal, with a pore size of 2 μm and a thickness of 5 mm, was used. Here, a porous metal body made of stainless sintered metal was used, but any porous metal body that does not allow water to easily penetrate into the power semiconductor device and ensures ventilation to the outside can be used. Other porous metal bodies may be made of copper, silver, aluminum, titanium, and various other metal alloys. In addition to metals, porous bodies made of ceramics such as aluminum oxide may also be used.

[0026] [Advantages of the First Embodiment] The power semiconductor device 100A (FIG. 1) of the first embodiment includes an insulating substrate 2a having a power semiconductor element 1 mounted on one side thereof, a heat dissipating base plate 3 joined to the surface of the insulating circuit substrate 2 opposite to the surface on which the power semiconductor element 1 is mounted, a case 4 fixed to the heat dissipating base plate 3 and surrounding the insulating substrate 2a, an insulating material 5 that insulates and seals the power semiconductor element 1 and the insulating substrate 2a inside the case 4, and a lid 6 formed integrally with the case 4 or a lid 6 fixed to the case 4 by a joining means (for example, an adhesive). At least a part of the part of the case 4 or the lid 6 that is not in contact with the insulating material 5 is provided with an air hole 50 having a porous material. That is, the semiconductor device 100A includes an air hole 50 having a porous material (gas permeable waterproof layer 7) in at least a part of the part (space 21) of the lid 6 that is not in contact with the insulating material 5. The air hole 50 may be provided in at least a part of the part (space 21) of the case 4 that is not in contact with the insulating material 5.

[0027] By doing so, by arranging an air vent 50 having a gas-permeable waterproof layer 7 (porous material) in the part of the case 4 or the lid 6 facing the internal space, the internal space can be kept at atmospheric pressure, and voids and cracks that occur in the silicone gel can be suppressed.

[0028] That is, as will be described later in comparison with the comparative example in FIG. 6, when the module that leaked air at high temperature is returned to room temperature, the inside becomes a negative pressure state, and the negative pressure is maintained for a long time. It was found that this negative pressure causes voids 33 (FIG. 6) in the silicone gel, which causes voltage resistance failure. In the power semiconductor device 100A of this embodiment, the vent hole 50 having a porous material is arranged in the part of the lid 6 that is not in contact with the insulating material 5, so that the internal space is always kept at atmospheric pressure even when there is a temperature change from a high temperature to room temperature. This makes it possible to prevent the occurrence of voids and cracks in the silicone gel. Since it is possible to prevent the occurrence of voids and cracks in the gel insulating material, it is possible to prevent partial discharge and insulation breakdown, and to realize a small and highly reliable power semiconductor device.

[0029] In addition, the ventilation hole 50 has a gas-permeable waterproof layer 7 made of a porous material that allows air to pass through but not water. This makes it possible to prevent moisture from entering through the hole 11 of the ventilation hole 50 while maintaining the internal space at atmospheric pressure, and to prevent moisture that has entered the power semiconductor device 100A from penetrating into the gel-like insulating material 5.

[0030] The power semiconductor device 100A can prevent partial discharge and dielectric breakdown by suppressing the penetration of moisture that has entered the device into the gel-like insulating material 5 and the generation of voids and cracks in the gel-like insulating material when heated.

[0031] Second embodiment 2 is a cross-sectional view showing the structure of a power semiconductor device according to a second embodiment of the present invention, in which the same components as those in FIG. The structure and manufacturing method of the power semiconductor device 100B of the second embodiment are substantially the same as those of the power semiconductor device 100A of FIG. 1, and only the differences will be described.

[0032] 2, a recess 6a is formed on the lid 6 around a hole 11 formed in the lid 6, and a gas-permeable waterproof layer 7 that allows air to pass through but not water to pass through is adhered and fixed to the lid 6 in the recess 6a via an adhesive (jointing means). The recess 6a is a so-called "countersink" so that the upper surface of the gas-permeable waterproof layer 7 and the upper surface of the lid 6 are flush with each other. The gas-permeable waterproof layer 7 of the power semiconductor device 100B is a porous film made of fluororesin (PTFE: polytetrafluoroethylene), with a pore size of 1.0 μm and a thickness of 0.25 mm. Other resin porous bodies 7 include polyethylene, polypropylene, polymethyl methacrylate, etc., and may be porous bodies made of other resins.

[0033] [Effects of the second embodiment] In the power semiconductor device 100B of the second embodiment, a recess 6a recessed from the outside to the inside of the lid 6 is formed at the hole 11 of the ventilation hole 50, and the gas-permeable waterproof layer 7 is fixed to the recess 6a with an adhesive. In this case, it is preferable that the surface of the lid 6 and the surface of the gas-permeable waterproof layer 7 are flush with each other. Since the gas-permeable waterproof layer 7 is arranged so as to rest on the recess 6a via the adhesive, the bonding area between the hole 11 and the gas-permeable waterproof layer 7 can be made larger than the ventilation hole 50 of the power semiconductor device 100A in FIG. 1, thereby improving the sealing performance and long-term stability.

[0034] (Third embodiment) 3 is a cross-sectional view showing the structure of a power semiconductor device according to a third embodiment of the present invention. In explaining FIG. 3, the same components as those in FIG. 1 and FIG. The structure and manufacturing method of the power semiconductor device 100B of the third embodiment are substantially the same as those of the power semiconductor device 100A in FIG. 1 and the power semiconductor device 100B in FIG. 2, and only the differences will be described.

[0035] In the power semiconductor device 100C shown in FIG. 3, a hole 11 is formed in a part of the lid 6, and a flanged protrusion 6b (protrusion) is formed around the hole 11. A rubber material (sealing material) 13 (jointing means) and a gas-permeable waterproof layer 7 are arranged on the upper surface of the flanged protrusion 6b, and a cap 14 made of an elastic material is placed on top of it and fixed so that no gap is formed between the lid 6 and the gas-permeable waterproof layer 7. The end of the cap 14 is a key portion 14a, and when the cap 14 is attached, this key portion 14a expands slightly and fits into the flanged protrusion 6b. The cap 14 is pressed against the flanged protrusion 6b of the lid 6, and the key portion 14a fits into the flanged protrusion 6b, thereby fixing the lid 6, the cap 14, the gas-permeable waterproof layer 7, and the rubber material 13. The rubber material 13 serves as a packing.

[0036] [Effects of the third embodiment] In the third embodiment of the power semiconductor device 100C, the ventilation hole 50 has a flanged protrusion 6b protruding outward from the lid 6, a hole 11 opened in the flanged protrusion 6b, a gas-permeable waterproof layer 7 fixed via a rubber material (sealing material) 13 so as to cover the hole 11, and a cap 14. The gas-permeable waterproof layer 7 is adhered to the rubber material 13, and is fixed to the flanged protrusion 6b by the cap 14 so as to press down on the rubber material 13, thereby improving the sealing performance. In particular, there is an advantage that the gas-permeable waterproof layer 7 can be replaced by removing and attaching the cap 14.

[0037] (Fourth embodiment) 4 is a cross-sectional view showing the structure of a power semiconductor device according to a fourth embodiment of the present invention. In explaining FIG. 4, the same components as those in FIGS. The structure and manufacturing method of a power semiconductor device 100D of the fourth embodiment are substantially the same as those of the power semiconductor devices 100A, 100B and 100C of FIGS. 1 to 3, and only the differences will be described.

[0038] The power semiconductor device 100D shown in Figure 4 is formed by crimping the gas-permeable waterproof layer 7 to a metal crimping material 15 (see crimp 7a), and insert-molding the metal crimping material 15 to which the gas-permeable waterproof layer 7 is crimped into the resin material of the lid 6. By insert-molding the gas-permeable waterproof layer 7 and the metal crimping material 15 into the resin material of the lid 6, the lid 6 and the gas-permeable waterproof layer 7 can be firmly fixed even if the adhesive strength between the resin material of the lid 6, the gas-permeable waterproof layer 7, and the adhesive is weak.

[0039] [Effects of the fourth embodiment] In the power semiconductor device 100D of the fourth embodiment, the ventilation hole 50 is insert-molded in the lid 6. With this configuration, even when the thickness of the lid 6 is thin, for example, and the bonding area between the resin material of the lid 6 and the gas-permeable waterproof layer 7 is not large and the adhesive strength of the adhesive is weak, it is possible to firmly fix the lid 6 and the gas-permeable waterproof layer 7 together.

[0040] Fifth embodiment 5 is a cross-sectional view showing the structure of a power semiconductor device according to a fifth embodiment of the present invention. In explaining FIG. 5, the same components as those in FIGS. The structure and manufacturing method of a power semiconductor device 100D of the fifth embodiment are substantially the same as those of the power semiconductor devices 100A, 100B and 100C of FIGS. 1 to 4, and only the differences will be described.

[0041] The power semiconductor device 100D shown in Figure 4 is formed by crimping the gas-permeable waterproof layer 7 to a metal crimping material 15 (see crimp 7a), and insert-molding the metal crimping material 15 to which the gas-permeable waterproof layer 7 is crimped into the resin material of the lid 6. By insert molding the gas-permeable waterproof layer 7 and the metal crimping material 15 into the resin material of the lid 6, the lid 6 and the gas-permeable waterproof layer 7 can be firmly fixed together even if the adhesive strength between the resin material of the lid 6, the gas-permeable waterproof layer 7, and the adhesive (joining means) is weak.

[0042] 5, the gas-permeable waterproof layer 7 includes gas-permeable waterproof layers 7b and 7c made of two porous films having different pore sizes. That is, the gas-permeable waterproof layer 7 is formed by stacking two gas-permeable waterproof layers 7b and 7c having different pore sizes. The gas-permeable waterproof layer 7b facing the inside of the power semiconductor device 100E is a porous film made of fluororesin (PTFE: polytetrafluoroethylene), with a pore size of 0.5 μm and a thickness of 0.25 mm. The gas-permeable waterproof layer 7c on the outside of the power semiconductor device 100E is a porous film made of fluororesin (PTFE: polytetrafluoroethylene), with a pore size of 2.0 μm and a thickness of 0.25 mm, just like the gas-permeable waterproof layer 7b.

[0043] By using a combination of gas-permeable waterproof layers 7b and 7c having different pore sizes, the ease of gas entering from the inside and the outside is changed, making it difficult for water vapor to enter the inside of the device from the outside and easy for water vapor to exit from the inside of the device.

[0044] [Effects of the fifth embodiment] In the power semiconductor device 100E of the fifth embodiment, the gas-permeable waterproof layer 7 has two gas-permeable waterproof layers 7b and 7c with different pore sizes, and the outer gas-permeable waterproof layer 7c has a larger pore size than the inner gas-permeable waterproof layer 7b. This makes it difficult for water vapor to enter the device from the outside, and makes it easy for water vapor to exit the device from the inside. In other words, if there is only one gas-permeable waterproof layer 7, the pore size is the same, and it is not possible to change the movement of water that enters the device or exits the device. However, there is a demand to prevent water vapor from entering the device and to expel water vapor from the device as much as possible, and the power semiconductor device 100E of this embodiment can meet this demand.

[0045] [Comparative Example] The following describes a comparison of reliability test results between the power semiconductor devices according to the first to fifth embodiments and a comparative example. <Configuration of Comparative Example> 6 is a cross-sectional view showing the structure of a power semiconductor device of a comparative example, in which the same components as those in FIG. The power semiconductor device of the comparative example shown in FIG. 6 has a hole 30 for injecting a gel insulating material in a part of the lid 6, and an air hole 31 for preventing an increase in the internal pressure of the device when the power semiconductor device generates heat. A gel insulating material is injected from the hole 30 for injecting the gel insulating material, the gel insulating material is cured under a predetermined curing condition, and then the hole 30 for injecting the gel is covered with the cap 32. The hole 30 for injecting the gel insulating material is in a state of being covered with the cap 32. However, the inside and outside of the power semiconductor device are in a state of ventilation through the ventilation hole 31. This ventilation hole 31 does not have a function of preventing water from passing through, unlike the gas-permeable waterproof layer 7 in each embodiment, and water easily penetrates into the inside of the device from the outside.

[0046] <Reliability testing of power semiconductor devices> [Reliability testing of power semiconductor devices] Reliability tests were carried out on the power semiconductor devices according to the first to fifth embodiments and a comparative example to confirm the effects of the present invention. The method of the reliability tests will be described.

[0047] (1) Water immersion test In the shipping test of power semiconductor devices, the bonding condition between the heat dissipation base plate and the insulating circuit board is inspected by ultrasonic inspection. In the ultrasonic inspection, the power semiconductor device is immersed in water. Therefore, to simulate this inspection, the power semiconductor device was immersed in water for about 20 minutes.

[0048] (2) High temperature storage test In the shipping test of power semiconductor devices, after ultrasonic inspection, the device is dried and subjected to a high-temperature blocking test, and the power semiconductor device is heated multiple times. To simulate this, the power semiconductor device was placed in a high-temperature chamber and subjected to heat treatment at 80°C for 1 hour and 100°C for 4 hours.

[0049] (3) Insulation test In a shipping test of a power semiconductor device, a partial discharge test and a withstand voltage test are performed as insulation tests to inspect the insulation of the device. The partial discharge test voltage and the withstand voltage test voltage are stipulated in standards such as IEC (International Electrotechnical Commission) and JIS (Japanese Industrial Standards) according to the withstand voltage of the element of the power semiconductor device. In order to verify the reliability of the power semiconductor devices 100A to 100D of the first to fifth embodiments and the comparative example, (1) a water immersion test and (2) a high-temperature storage test were performed, and finally, (3) a partial discharge test and a dielectric withstand voltage test were performed as an insulation test.

[0050] Both the partial discharge test and the dielectric strength test are carried out by shorting all the terminals of the power semiconductor device and applying a high voltage between all the terminals and the heat dissipation base. In the partial discharge test, a voltage of 7 kVrms is applied for 1 minute, then reduced to 5.1 kVrms and applied for 30 seconds, and the amount of discharged charge of partial discharge is measured in the last 5 seconds. If a partial discharge occurs and the amount of discharged charge exceeds 10 pC, the insulation is judged to be "bad", and if it is within 10 pC, it is judged to be "good". In the voltage resistance test, a voltage of 10.2 kVrms was applied for one minute, and if no dielectric breakdown occurred, the insulation was judged to be "bad," and if no dielectric breakdown occurred, the insulation was judged to be "good."

[0051] With reference to a comparative example in FIG. 6, a problem with a conventional power semiconductor device (high-voltage power module, hereinafter referred to as module) will be described. The air leak test at the blocking test temperature is carried out according to the following procedure. The module of the comparative example was immersed in Fluorinert and heated on a hot plate, and a test was performed to see whether the internal pressure of the module changed and whether air leaked to the outside. When a module that leaks air at high temperatures is returned to room temperature, the inside of the device is placed in a negative pressure state, and this negative pressure is maintained for a long time. This negative pressure causes voids 33 (Figure 6) in the silicone gel, resulting in poor pressure resistance.

[0052] In a voltage resistance test of the module, dielectric breakdown occurs at a rate of 3 to 4%, which deteriorates the yield. The above problem was discovered for the first time by the present inventors. The present inventors speculated that the cause of the dielectric breakdown was voids 33 (FIG. 6) that occur in the silicone gel.

[0053] 7A to 7C are diagrams showing, in the form of a table, the results of reliability tests of the power semiconductor devices 100A to 100D of the first to fifth embodiments and a power semiconductor device of a comparative example. Fig. 7A is a diagram showing the partial discharge test results, and Fig. 7B is a diagram showing the dielectric strength test results. Fig. 7C is a diagram showing the pass / fail judgment of the test, summarizing the results of the partial discharge test (Fig. 7A) and the dielectric strength test (Fig. 7B) after the water immersion test and the high-temperature storage test. In the diagram, a circle indicates a "pass" judgment, and a cross indicates a "fail" judgment.

[0054] As shown in Figures 7A to 7C, for the sample corresponding to the power semiconductor device 100A of the first embodiment, the sample corresponding to the power semiconductor device 100B of the second embodiment, the sample corresponding to the power semiconductor device 100C of the third embodiment, the sample corresponding to the power semiconductor device 100D of the fourth embodiment, and the sample corresponding to the power semiconductor device 100E of the fifth embodiment, all seven out of seven samples passed the partial discharge test and the dielectric breakdown test with a good result.

[0055] In this way, all of the power semiconductor devices 100A to 100E according to the first to fifth embodiments are Both the partial discharge test and the dielectric breakdown test passed with a positive result.

[0056] In contrast, in the samples corresponding to the power semiconductor device of the comparative example, partial discharge occurred in 5 out of 7 units in the partial discharge test (Fig. 7A), resulting in a failure judgment, and in the insulation withstand voltage test (Fig. 7B), insulation breakdown occurred in 4 out of 7 units, resulting in a failure judgment, and the tests could not be passed (Fig. 7C).

[0057] After the insulation test, the lids 6 of each of the power semiconductor devices 100A-100E of the first to fifth embodiments and the power semiconductor device of the comparative example were opened to observe the inside of the power semiconductor device. It was confirmed that there were no voids or cracks in the gel-like insulating material in the power semiconductor device of the first to fifth embodiments. In contrast, it was confirmed that voids were generated in the gel-like insulating material in the power semiconductor device of the comparative example.

[0058] [effect] As described above, the power semiconductor devices 100A-100E are provided with the ventilation holes 50 having a porous material in at least a part of the portion of the case 4 or the lid 6 that is not in contact with the insulating material 5. This prevents water from entering the inside of the power semiconductor devices 100A-100E, and prevents voids and cracks from occurring in the gel insulating material even when the power semiconductor devices 100A-100E generate heat or are heated from the outside during testing. As a result, it is possible to realize a power semiconductor device that can suppress the occurrence of partial discharge and maintain a dielectric strength voltage.

[0059] The above-described embodiments are merely examples, and the present invention is not limited to these embodiments as long as the characteristics of the invention are not impaired. The present invention is not limited to the above-described embodiment, and includes other modifications and applications without departing from the gist of the present invention described in the claims. [Explanation of symbols]

[0060] 1. Power semiconductor element (semiconductor element) 2. Insulated circuit board 2a Insulating substrate 3 Heat dissipation base plate (heat dissipation base) 4 Cases 5. Gel-like insulating material (insulating material) 6 Lid 6a Recess 6b Flanged protrusion (protrusion) 7,7a,7b,7c Gas permeable waterproof layer (porous material) 11 Hole 12 Adhesive (joining means) 13 Sealing material (rubber material) (jointing means) 14 Cap 15 Metal rivets 21 Space inside power semiconductor device 33 Void 50 Ventilation holes 100A, 100B, 100C, 100D, 100E Power semiconductor device (semiconductor device)

Claims

1. A semiconductor device comprising: An insulating substrate having a semiconductor element mounted on one surface thereof; a heat dissipation base joined to a surface opposite to the surface on which the semiconductor element is mounted; a case fixed to the heat dissipation base and surrounding an insulating substrate; an insulating material that insulates and seals the semiconductor element and the insulating substrate inside the case; a lid formed integrally with the case or fixed to the case by a joining means; A vent hole having a porous material is provided in at least a part of the case or the lid that is not in contact with the insulating material. A semiconductor device comprising:

2. The air vent has a hole opened in the case or the lid, and a gas-permeable waterproof layer arranged to close the hole, which allows air to pass but does not allow water to pass through.

2. The semiconductor device according to claim 1,

3. The air vent has a recess formed at the hole portion that is recessed from the outside of the case or the lid to the inside, and the gas-permeable waterproof layer is fixed to the recess by a joining means.

3. The semiconductor device according to claim 2.

4. The air vent has a protrusion protruding to the outside of the case or the lid, the hole opened in the protrusion, and the gas-permeable waterproof layer fixed by a joining means so as to close the hole.

3. The semiconductor device according to claim 2.

5. The gas-permeable waterproof layer is a moisture-permeable waterproof membrane that allows air to pass through but not water.

3. The semiconductor device according to claim 2.

6. The gas-permeable waterproof layer is a porous material made of resin, ceramic, or metal.

3. The semiconductor device according to claim 2.

7. The ventilation hole is insert molded into the case or the lid.

2. The semiconductor device according to claim 1,

8. The porous material has a pore size ranging from 0.01 μm to 100 μm.

2. The semiconductor device according to claim 1,

9. The porous material is formed of a plurality of gas-permeable waterproof layers having different pore sizes.

2. The semiconductor device according to claim 1,

10. The gas-permeable waterproof layers have an outer gas-permeable waterproof layer with a larger pore size than an inner gas-permeable waterproof layer.

10. The semiconductor device according to claim 9.

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