Semiconductor device

Abstract

To provide a semiconductor device, particularly a power semiconductor device required to operate stably at high temperatures, the semiconductor device restraining permeation of water component infiltrating into the device to an insulating material and occurrence of voids and cracks in the insulating material when heated, thereby preventing partial discharge and dielectric breakdown.SOLUTION: A semiconductor device includes a semiconductor substrate on which a semiconductor element is mounted, and a housing that hermetically seals the semiconductor substrate. The housing has a pressure adjusting section that changes the volume inside the housing in accordance with the pressure inside the housing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device, and more particularly to a power semiconductor device that is required to operate stably at high temperatures. [Background technology]

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

[0003] A power conversion system is composed of numerous components, such as power semiconductor devices (power modules) incorporating power semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors), bus bars, capacitors, inductors, various sensors, and control circuits. Compact, highly reliable power conversion systems are required to reduce 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 systems.

[0004] Currently, power semiconductor elements in power semiconductor devices mainly use IGBTs and diodes made of Si. As mentioned above, power semiconductor devices are becoming smaller and have larger capacities, which requires stable operation at high temperatures. Power semiconductor elements are also required to have high breakdown voltage, low on-resistance, and high-speed switching characteristics. SiC, which has a breakdown field strength 10 times that of Si and a band gap 3 times that of Si, is beginning to be applied as a next-generation power semiconductor element and is expected to become more widespread. These next-generation power semiconductor elements will be able to operate at even higher temperatures than Si devices, so power semiconductor devices must have high reliability at high temperatures.

[0005] Patent Document 1, for example, is an example of a power semiconductor device that aims to achieve high reliability during high-temperature operation. Patent Document 1 discloses a power semiconductor device in which a lead pin block includes a base portion from which many lead pins stand, a lid receiving step portion, engaging claws on the inner surface of a frame portion, guide pins that are inserted into guide holes in a female connector of the lead pins 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 engaging claw. In Patent Document 1, when the lead pin block is dropped onto the inner surface of the frame portion and the engaging claws are engaged with the engaging claws, the block is tightly secured to prevent it from coming loose, but the gap between the block and the frame portion is sealed with a seal. The space inside the semiconductor device is in communication with the outside air via 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 gap between the frame and the lead pin block is sealed with a sealant on the internal space side. Therefore, even if the temperature of the gel resin encapsulant rises due to heating for fixing the insulating lid to the insulating case frame or heat generated by the semiconductor element, causing the gel resin encapsulant to thermally expand, the gel resin encapsulant will not seep out of the gap. Furthermore, as the gel resin encapsulant expands, the air pressure of the residual air in the internal space increases. However, the air vent holes prevent this internal pressure from increasing, allowing the gel resin encapsulant to expand freely. This is said to suppress the occurrence of excessive thermal stress and improve reliability.

[0007] Furthermore, Patent Document 2 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 that has a case with a substrate used as a bottom plate attached, a semiconductor element and electrical connection members attached to the side of the substrate facing the inside of the case, a soft sealing material injected into the case, and a hard sealing material injected on top of that, and that has a protection space connected to the space inside the case into which the soft sealing material has been injected, and is formed so that the soft sealing material expands into the protection space when the temperature rises, and that the protection 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 protection space inside, the soft sealing material can expand in volume, preventing the generation of high pressure inside the power semiconductor device that could damage the power semiconductor device. It is also considered preferable to provide an opening in the wall of the case that forms the protection space, allowing the air inside the protection space to communicate with the outside air surrounding the device, thereby allowing the power semiconductor device to breathe.

[0009] The power semiconductor devices in Patent Documents 1 and 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 vent (an "air vent hole" in Patent Document 1, and an "opening" in Patent Document 2) is formed in part of the case or in part of the lead pin block. When the semiconductor element is operating and generating heat, the gel resin sealant expands in volume, preventing overflow from gaps and an increase in internal pressure, and suppressing the generation of excessive thermal stress.

[0010] Meanwhile, in the shipping test of a power semiconductor device in which a substrate carrying a power semiconductor element is bonded to a heat-dissipating base plate with a bonding material such as solder, there is a process to inspect the bonding condition between the heat-dissipating base plate and the substrate. The power semiconductor device is immersed in water, and ultrasonic waves are used to inspect the presence of solder voids or sink marks at the bonding interface between the heat-dissipating base plate and the substrate. This is an important inspection to confirm the heat dissipation performance 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 Publication No. 63-28052 Summary of the Invention [Problem to be solved by the invention]

[0012] In the technologies described in Patent Documents 1 and 2, water may enter 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 creates a high-temperature, high-humidity environment inside the device due to heating, such as during a high-temperature blocking test performed as part of the inspection process during the aforementioned shipping test. This vaporizes the water and penetrates into the gel-like resin encapsulant. Furthermore, the vaporized water forms voids and cracks in the gel-like resin encapsulant. Subsequently, when a high voltage is applied during a partial discharge test or a withstand voltage test, partial discharges or dielectric breakdown may occur. These issues needed to be addressed in conventional power semiconductor devices.

[0013] Furthermore, power semiconductor devices are incorporated into power conversion devices for use. In this case, depending on the housing structure of the power conversion device and the environment in which it is used, it is possible that water such as rainwater or condensation may get on the power semiconductor device. Furthermore, in hot and humid environments such as during the rainy season, the inside of the device may also become humid through the ventilation holes. When the temperature drops under these conditions, moisture may be trapped inside the device. With the technologies of Patent Documents 1 and 2, it is possible that water may enter the device during use through ventilation holes formed in a part of the case or a part of the lead pin block. Moisture that enters the device may reduce the device's insulation and reliability, 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] The present invention has the following configuration for solving the above problems. A semiconductor device comprising a semiconductor substrate on which a semiconductor element is mounted and a housing that hermetically seals the semiconductor substrate, wherein the housing has a pressure adjusting section that changes the volume inside the housing in accordance with the pressure inside the housing. [Effects of the Invention]

[0016] According to the present invention, it is possible to prevent moisture from penetrating into the device, and to suppress voids and cracks that occur in the insulating material when heated by moisture that has penetrated the insulating material, thereby preventing partial discharge and dielectric breakdown.

[0017] Furthermore, since an excessive increase in internal pressure when the temperature rises can be prevented, stress applied to the gel insulating material can be prevented, and crushing and cracking of the gel insulating material can be prevented. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view schematically illustrating a structure of a power semiconductor device according to a first embodiment of the present invention. [Figure 2] 2A to 2C are diagrams illustrating deformation of an expandable / contractible part in response to pressure inside the device in the power semiconductor device according to the first embodiment of FIG. 1. [Figure 3] FIG. 4 is a cross-sectional view schematically illustrating the structure of a power semiconductor device according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view schematically illustrating the structure of a power semiconductor device according to a third embodiment of the present invention. [Figure 5] 1A and 1B are a cross-sectional view showing a structure of a power semiconductor device of Comparative Example 1 (Conventional Example 1) and a diagram for explaining a problem that occurs in the conventional power semiconductor device. [Figure 6] 1A and 1B are a cross-sectional view showing a structure of a power semiconductor device of Comparative Example 2 (Conventional Example 2) and a diagram for explaining a problem that occurs in the conventional power semiconductor device. [Figure 7A] 10 is a diagram showing partial discharge test results for the first to third embodiments of the power semiconductor device of the present invention and comparative examples 1 and 2. FIG. [Figure 7B]1 is a diagram showing the results of a dielectric strength test in the first to third embodiments of the power semiconductor device of the present invention and comparative examples 1 and 2. FIG. [Figure 7C] 10 is a diagram showing test pass / fail results for the first to third embodiments of the power semiconductor device of the present invention and comparative examples 1 and 2. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0020] 1 is a cross-sectional view showing a structure of a power semiconductor device according to a first embodiment of the present invention. This embodiment is an example in which a semiconductor device is applied to a power semiconductor device including a power semiconductor element.

[0021] 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 dissipation base plate 3 (heat dissipation 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 dissipation base plate 3 and surrounding the insulating circuit board 2, a gel-like insulating material 5 inside the case 4 that insulates and seals the power semiconductor element 1 and the insulating circuit board 2, 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 part of the portion of the lid 6 that is not in contact with the insulating material 5 is provided with a movable part 50 that deforms in response to the pressure in the space 31 inside the device.

[0022] The movable part 50 has a hole 7 opened in the case 4 or the lid 6, an expandable movable part 21 that is arranged to close the hole 7 and deforms due to the pressure in the space 31 inside the device, and a frame part 22 that bonds the expandable movable part to the side wall of the hole in the lid. The expandable movable part 21 and the frame part 22 in this embodiment are made of a rubber-like organic material that is impermeable to air and water.

[0023] Except for the frame portion 22 that is bonded to the side wall of the hole in the lid via the adhesive 10, the rubber-like organic material of the expandable movable portion 21 is formed thinner than the frame portion 22 so that it deforms in response to pressure changes in the space 31 inside the device. This embodiment is an example in which the movable portion 50 is provided in a part of the lid 6, but it is also possible to provide the movable portion 50 in the case 4. In the claims, the insulated circuit board 2 on which the power semiconductor element 1 is mounted is called the "semiconductor substrate," and the state in which the lid 6 is fixed to the case 4 and the "semiconductor substrate" is hermetically sealed is called the "housing." Also, the movable part 50 that moves so as to change the volume inside the "housing" by deforming in response to the pressure in the space 31 inside the device corresponds to the "pressure adjusting part" described in the claims.

[0024] A method for manufacturing the power semiconductor device 100A configured as described above will now be described.

[0025] As shown in FIG. 1, the insulating circuit board 2 of the power semiconductor device 100A has a circuit electrode 2b bonded to one surface of an insulating substrate 2a and a back electrode 2c bonded to the other surface via a brazing material 2d.

[0026] The insulating substrate 2a is selected from the following materials depending on the normal device breakdown voltage of the power semiconductor device 100A. That is, for the power semiconductor device 100A with a normal device breakdown voltage of 1200V or more, ceramics such as aluminum oxide, aluminum nitride, and silicon nitride are used for the insulating substrate 2a. On the other hand, for the power semiconductor device 100A with a device breakdown voltage of less than 1200V, a high thermal conductive resin substrate in which a high thermal conductive filler is dispersed in an organic resin is used. In the case of a high thermal 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 required.

[0027] The circuit electrodes 2b are formed with a circuit using a technique such as etching in a circuit shape required for the circuit operation of the power semiconductor device 100A.

[0028] First, the power semiconductor element 1 is bonded onto the circuit electrodes 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 electrodes 2b of the insulating circuit board 2 are connected using thin metal wires such as aluminum to form the required circuit (thin metal wires are omitted from Figure 1). Then, the heat dissipating base plate 3 and the backside electrodes of the insulating circuit board 2 are bonded via a bonding material 9 such as solder. Next, adhesive 10 is applied to the outer periphery of the heat dissipating base plate 3 to secure the case 4 to the heat dissipating base plate 3. In addition to the adhesive, the heat dissipating base plate 3 and the case 4 may also be secured together with screws (screws are not shown). Then, terminals 11 are bonded onto the circuit electrodes 2b of the insulating circuit board 2 using a technique such as ultrasound.

[0029] Thereafter, a lid 6 is placed on top of the power semiconductor device 100A, and the case 4 and the lid 6 are bonded and fixed together using an adhesive 10. Here, a hole 7 (a movable part 50 will be formed in this hole 7 later) is formed in the lid 6 in advance so that a gel insulating material can be injected into the device. Then, the gel insulating material 5 is injected through the hole 7, and the gel insulating material 5 is hardened under predetermined hardening conditions. Silicone gel is generally used as the gel insulating material 5, but any material having insulating properties may be used, and other resins other than silicone may also be used.

[0030] Finally, adhesive 10 (jointing means) is applied around hole 7 in lid 6, and movable part 50, which deforms in response to the pressure in device internal space 31, more specifically frame part 22 of movable part 50, is adhesively fixed to hole 7 to complete power semiconductor device 100A. Note that in FIG. 1, lid 6 is fixed to case 4 with adhesive 10, which is jointing means, but case 4 and lid 6 may also be formed integrally. The material of case 4 and lid 6 is, for example, an organic insulating material such as PPS (polyphenylene sulfide) or PBT (polybutylene terephthalate).

[0031] A rubber-like organic material is used for the movable part 50 (the expandable movable part 21, the frame part 22) of the power semiconductor device 100A. Here, silicone rubber is used, but any material may be used as long as it does not easily penetrate water or air into the power semiconductor device and deforms in response to pressure changes in the device's internal space 31. The frame part 22 of the movable part 50 is thick in the vertical direction, and the expandable movable part 21 inside the frame part is thin in the vertical direction so that it can deform and move. For example, the frame part 22 is 5 mm thick, and the thin-walled movable part 21 is 200 μm thick. In addition to silicone rubber, other rubber materials such as natural rubber, nitrile rubber, urethane rubber, acrylic rubber, isoprene rubber, butadiene rubber, and styrene rubber may also be used as the rubber-like organic material for the movable part 50. A rubber material with excellent heat resistance, cold resistance, aging resistance, ozone resistance, and weather resistance so that it can withstand the environment in which the semiconductor device is used for a long period of time is preferred.

[0032] By making the housing of the power semiconductor device 100A the airtight structure described above, it is possible to prevent moisture from entering the inside of the device, and as shown in Figure 2, when the temperature rises during operation of the device, the expandable movable part 21 of the movable part 50 extends outward from the device in a direction (21a) that expands the volume of the space 31 inside the device, thereby minimizing the increase in pressure in the space 31 inside the device. Also, when the temperature drops during shutdown of the device, it extends inward from the device in a direction (21b) that reduces the volume of the space inside the device, thereby changing the volume inside the housing and minimizing the decrease in pressure in the space 31 inside the housing, thereby minimizing the occurrence of voids and cracks in the silicone gel.

[0033] As will be described later, in a semiconductor device with ventilation holes, such as in Comparative Example 1 (FIG. 5), moisture penetrates the device through the ventilation holes and gradually penetrates into the silicone gel. At high temperatures, the penetrated moisture evaporates, creating voids 32 in the silicone gel, potentially resulting in partial discharges and poor pressure resistance. In a sealed semiconductor device without ventilation holes, such as in Comparative Example 2 (FIG. 6), the pressure inside the device increases at high temperatures. When the adhesive between the case and lid can no longer withstand the increased pressure, air leaks from the adhesive interface between the case and lid. When the device temperature drops, the internal space of the device becomes negative pressure. This negative pressure seals the case and lid, preventing air from entering the semiconductor device from the outside and maintaining the negative pressure for a long period of time. This negative pressure creates voids 32 in the silicone gel, potentially resulting in partial discharges and poor pressure resistance. In contrast, the power semiconductor device 100A of this embodiment includes a movable part 50 that deforms in response to the pressure in the space inside the device, located in a portion of the lid 6 that is not in contact with the insulating material 5. This prevents moisture from entering the device and prevents voids from forming in the silicone gel due to the evaporation of moisture at high temperatures. Furthermore, even when the temperature changes from low to high or from high to low, the deformation of the movable part reduces the pressure change in the space inside the device. This prevents voids and cracks from forming in the silicone gel. Since voids and cracks can be prevented from forming in the gel insulating material, partial discharge and dielectric breakdown can be prevented, resulting in a compact, highly reliable power semiconductor device.

[0034] Furthermore, if the temperature of the semiconductor device becomes abnormally higher than expected and the expandable / contractable part 21 is no longer able to accommodate the pressure change in the space inside the device within its deformation range, as in Comparative Example 2, it is expected that air will leak from the adhesive interface between the case and the lid, and the internal space of the device will enter a negative pressure state when the device is returned to room temperature. In this case, the expandable / contractable part 21 will deform in a direction that reduces the volume of the internal space of the device at the same temperature compared to its initial, unexpanded state. The soundness of the semiconductor device can also be determined by checking this deformation. If no change is observed in the movable part even when the temperature of the device changes, this indicates that the device is not sealed, which may indicate that the device is absorbing moisture. The soundness of the semiconductor device can also be evaluated by monitoring the change in the movable part when the temperature changes.

[0035] As a method of monitoring, the movable part of the extendable movable part 21 may be color-coded to indicate normal and abnormal ranges, allowing visual inspection to determine whether the device is healthy, or a scale may be provided to allow the user to read the values displayed on the scale. Specifically, by providing a concentric pattern on the rubber-like member, the size of the concentric circles changes when the rubber-like member stretches due to a change in pressure, and the state of the pressure change can be estimated from this size. Also, by painting each of the multiple concentric circles a different color, the color tone changes as the rubber-like member stretches (the color becomes lighter as it stretches), and the state of the pressure change can be estimated based on this change in color tone.

[0036] If necessary, a device such as a strain sensor that converts the amount of movement of the movable part of the expandable movable part 21 into an electrical signal can be provided, and a system that automatically monitors the soundness based on the electrical signal can be provided.

[0037] Furthermore, semiconductor devices may be used in high-altitude areas. If the semiconductor device is hermetically sealed at the time of factory shipment, the internal volume of the housing will be large from the start (in the configuration of Example 1, the rubber-like member is used in a state where it protrudes to the outside), which may result in the housing being unable to absorb pressure changes. Therefore, a pressure adjustment hole can be provided in part of the housing to adjust the internal pressure of the housing to the local pressure. After transporting the semiconductor device to the area where it will be used, the hole is opened to adjust the internal pressure of the housing to the local atmospheric pressure, and then the hole is closed with a screw, thereby adapting the semiconductor device to the area where it will be used. Reference numeral 60 in FIG. 1 is an example of a pressure adjustment screw. Any device other than a screw can be used as long as it can temporarily open the interior of the housing to the outside. In the claims, this screw-like member is referred to as an "air opening portion." Furthermore, when the semiconductor device according to the present invention is mounted on an aircraft, the air pressure outside the housing fluctuates repeatedly and to a large extent. Under such operating conditions, adjusting the pressure inside the housing to match the external air pressure may actually promote the formation of voids and cracks in the silicone gel. For semiconductor devices used under such conditions, it may be effective to provide a limiter that limits the amount of adjustment by the pressure adjustment unit. An effective limiter is a plate-shaped member that prevents the rubber-like member from expanding further upward. An example of a limiter is shown in Figure 2 as 70. A pipe-shaped member 70 with one closed end is provided to cover the rubber-like member. The pipe-shaped member 70 has a side hole 71 that communicates with the outside air, allowing the rubber-like member to be subjected to external air pressure. [Example]

[0038] 3 is a cross-sectional view showing the structure of a power semiconductor device according to a second embodiment of the present invention. In explaining FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals.

[0039] The structure and manufacturing method of the power semiconductor device 100B of the second embodiment are almost the same as those of the power semiconductor device 100A of FIG. 1, and only the differences will be described.

[0040] 3, a movable part 51 composed of a frame part 24 and a bellows-shaped expandable movable part 23 is disposed in a hole 7 formed in the lid 6. This point differs from the power semiconductor device 100A of the first embodiment. An adhesive 10 (jointing means) is applied around the hole 7 of the lid 6, and the frame part 24 of the movable part 51, which deforms in response to the pressure inside the device, is adhesively fixed to the hole 7 to complete the power semiconductor device 100B.

[0041] A power semiconductor device 100B (FIG. 3) of the second embodiment includes an insulating substrate 2a having a power semiconductor element 1 mounted on one surface thereof, a heat dissipation base plate 3 joined to the surface of the insulating circuit board 2 opposite to the surface on which the power semiconductor element 1 is mounted, a case 4 fixed to the heat dissipation base plate 3 and surrounding the insulating circuit board 2, an 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 formed integrally with the case 4 or fixed to the case 4 by a joining means (e.g., an adhesive), and includes a movable part 51 that expands and contracts in response to the pressure in the space inside the semiconductor device in at least a part of a portion of the case 4 or the lid 6 that is not in contact with the insulating material 5. That is, the semiconductor device 100A includes a movable part 51 that expands and contracts in response to the pressure in the space inside the semiconductor device in at least a part of a portion of the lid 6 that is not in contact with the gel-like insulating material 5. By doing this, by disposing movable part 51 that expands and contracts in response to the pressure in the space inside the semiconductor device on the portion of case 4 or lid 6 facing the device's internal space, moisture can be prevented from entering the device, and when the temperature rises during device operation, bellows-shaped movable part 23 expands outward in the direction expanding the volume of space 31 inside the device, thereby minimizing the increase in pressure in device internal space 31. Also, when the temperature drops during device operation, it contracts inward in the direction reducing the volume of the device internal space, thereby minimizing the decrease in pressure in device internal space 31, thereby suppressing the occurrence of voids and cracks in the silicone gel. Furthermore, instead of bellows-shaped movable part 23, a disk-shaped member such as a diaphragm can be used, or a bellows-shaped movable part can be combined with a diaphragm to accommodate greater pressure changes inside the housing. [Example]

[0042] 4 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. 4, the same components as those in FIGS. 1 and 3 are denoted by the same reference numerals.

[0043] The structure and manufacturing method of the power semiconductor device 100C of the third embodiment are almost the same as those of the power semiconductor device 100A of FIG. 1 and the power semiconductor device 100B of FIG. 2, and only the differences will be described.

[0044] 4, a movable part 52 composed of an outer tubular part 27, a gasket 25, and a plunger 26 is disposed in a hole 7 formed in the lid 6. This point differs from the power semiconductor device 100A of the first embodiment and the power semiconductor device 100B of the second embodiment. The power semiconductor device 100C is completed by applying adhesive 10 (jointing means) around the hole 7 of the lid 6, and adhesively fixing the outer tubular part 27 of the movable part 52, which deforms in response to the pressure inside the device, to the hole 7.

[0045] The power semiconductor device 100C of the third embodiment comprises an insulating substrate 2a having a power semiconductor element 1 mounted on one side thereof, a heat dissipation base plate 3 joined to the surface of the insulating circuit board 2 opposite to the surface on which the power semiconductor element 1 is mounted, a case 4 fixed to the heat dissipation base plate 3 and surrounding the insulating circuit board 2, an 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 formed integrally with the case 4 or fixed to the case 4 by a joining means (e.g., an adhesive), and at least a portion of the portion of the case 4 or the lid 6 that is not in contact with the insulating material 5 comprises a movable part 52 that expands and contracts in accordance with the pressure in the space inside the semiconductor device.

[0046] That is, the semiconductor device 100A is provided with a movable part 52 that expands and contracts in response to the pressure in the space inside the semiconductor device, in at least a portion of the portion (space 31) of the lid 6 that is not in contact with the gel-like insulating material 5. By arranging the movable part 52 that expands and contracts in response to the pressure in the space inside the semiconductor device on the portion of the case 4 or the lid 6 that faces the space inside the device, it is possible to prevent moisture from entering the device, and the movable part made up of the gasket 25 and the plunger 26 expands outward from the device in a direction that expands the volume of the space 31 inside the device when the temperature rises during operation, thereby minimizing the increase in pressure in the space 31 inside the device, and also shrinks inward from the device in a direction that reduces the volume of the space inside the device when the temperature drops during shutdown of the device, thereby minimizing the decrease in pressure in the space 31 inside the device, thereby suppressing the generation of voids and cracks in the silicone gel.

[0047] By using the plunger 26, it becomes easier to monitor changes in the moving part when the temperature changes, as described in Example 1. When the rubber-like member of Example 1 is used, it is somewhat difficult to accurately determine how much the moving part has moved, but monitoring the up and down movement of the plunger 26 allows for more quantitative understanding than when a rubber-like member is used. By providing a scale on the vertical bar of such plunger 26 or displaying the scale in different colors, it becomes possible to monitor (manage) changes in the moving part more quantitatively and easily.

[0048] Furthermore, by increasing the range of movement of the plunger as necessary, it is possible to accommodate larger volume changes. Furthermore, limiters can be provided above and below the plunger, and a system can be provided that detects and alerts the plunger when it attempts to move beyond the limiter. In other words, if the plunger attempts to move beyond the limiter, some abnormality may have occurred in the semiconductor device, and by alerting the system, accidents in vehicles equipped with the semiconductor device can be prevented. Furthermore, as described in Example 1, by limiting the range of movement of the plunger, pressure fluctuations within the housing can be limited to a predetermined pressure range, which can prevent the formation of voids and cracks in the silicone gel from being promoted in semiconductor devices used under conditions where pressure fluctuations are repeated, such as in aircraft. [Comparative Example] The following describes the results of reliability tests of the power semiconductor devices according to the first to third embodiments and Comparative Examples 1 and 2, in comparison with each other. <Configuration of Comparative Example 1> 5 is a cross-sectional view showing the structure of the power semiconductor device of Comparative Example 1. The same components as those in FIG.

[0049] The power semiconductor device of the comparative example shown in FIG. 5 has a hole 7 formed in a part of the lid 6 for injecting a gel insulating material, and an air vent 14 formed to prevent the internal pressure inside the device from increasing when the power semiconductor device generates heat.

[0050] Gel insulating material is injected through hole 7 for injecting the gel insulating material, and the gel insulating material is cured under predetermined curing conditions, after which hole 7 for injecting the gel is covered with cap 13. Hole 7 for injecting the gel insulating material is covered with cap 13. However, the inside and outside of the power semiconductor device are ventilated by ventilation hole 14. This ventilation hole 14 allows water or moisture to easily penetrate into the inside of the device from the outside. <Configuration of Comparative Example 2> 6 is a cross-sectional view showing the structure of a power semiconductor device of Comparative Example 2. The same components as those in FIG.

[0051] In the power semiconductor device of the comparative example shown in FIG. 6, a hole 7 is formed in a part of the lid 6 for injecting a gel insulating material.

[0052] Gel insulating material is injected through hole 7 for injecting the gel insulating material, and the gel insulating material is cured under predetermined curing conditions, after which hole 7 for injecting the gel is covered with cap 13. Hole 7 for injecting the gel insulating material is covered with cap 13. No ventilation hole like in Comparative Example 1 is provided, and the device is sealed. Water or moisture does not easily penetrate into the device from the outside. <Reliability testing of power semiconductor devices> [Reliability testing of power semiconductor devices] The effects of the present invention were confirmed by carrying out reliability tests on the power semiconductor devices according to the first to third embodiments and Comparative Examples 1 and 2. The reliability test method will now be described. (1) Submersion test In the shipping test of power semiconductor devices, ultrasonic inspection is used to inspect the bonding condition between the heat dissipation base plate and the insulating circuit board. For ultrasonic inspection, the power semiconductor device is immersed in water. Therefore, to simulate this inspection, the power semiconductor device was immersed in water for approximately 20 minutes. (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 these tests, 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. (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 properties of the device. The partial discharge test voltage and the withstand voltage test voltage are specified by standards such as the International Electrotechnical Commission (IEC) and the Japanese Industrial Standards (JIS) according to the withstand voltage of the element of the power semiconductor device. To verify the reliability of the power semiconductor devices 100A to 100C of the first to third embodiments and the comparative examples 100D and 100E, (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 insulation tests.

[0053] Both the partial discharge test and the dielectric strength test are carried out by short-circuiting all terminals of the power semiconductor device and applying a high voltage between all terminals and the heat sink base.

[0054] 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 the 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."

[0055] In the withstand voltage test, a voltage of 10.2 kVrms was applied for one minute, and if no breakdown occurred, the insulation was judged to be "bad," and if no breakdown occurred, the insulation was judged to be "good."

[0056] Referring to Comparative Example 2 in FIG. 6, the problems with the conventional power semiconductor device (high-voltage power module, hereinafter referred to as module) will be described.

[0057] The air leak test at the blocking test temperature is carried out according to the following procedure.

[0058] The module of Comparative Example 2 was immersed in Fluorinert and heated on a hot plate, and a test was conducted to check the change in the internal pressure of the module and whether or not there was any air leakage to the outside.

[0059] 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, which is maintained for a long time. This negative pressure causes voids 32 (Figure 6) in the silicone gel, resulting in a pressure resistance failure.

[0060] In a voltage resistance test of the module, dielectric breakdown occurs at a rate of 3 to 4%, which reduces 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 32 (FIG. 6) that occur in the silicone gel.

[0061] 7A to 7C are diagrams showing, in tables, the results of reliability tests on the power semiconductor devices 100A to 100C of the first to third embodiments and the power semiconductor device of the 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 an × indicates a "fail" judgment.

[0062] 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, and the sample corresponding to the power semiconductor device 100C of the third embodiment, all seven out of seven samples passed the partial discharge test and the dielectric breakdown test with a good result.

[0063] In this way, all of the power semiconductor devices 100A to 100C of the first to third embodiments Both the partial discharge test and the dielectric breakdown test passed with a positive result.

[0064] In contrast, in the samples corresponding to the power semiconductor device of Comparative Example 1, partial discharge occurred in 5 out of 7 units in the partial discharge test (FIG. 7A), and the test was judged as failed in 4 out of 7 units in the dielectric withstand voltage test (FIG. 7B), resulting in dielectric breakdown and failing the test (FIG. 7C). Furthermore, in the samples corresponding to the power semiconductor device of Comparative Example 2, partial discharge occurred in two out of seven units in the partial discharge test (FIG. 7A), resulting in a failure judgment, and in the dielectric strength test (FIG. 7B), insulation breakdown occurred in one out of seven units, resulting in a failure judgment, and the test could not be passed (FIG. 7C).

[0065] After the insulation test, the lids 6 were opened to observe the interiors of the power semiconductor devices 100A to 100C of the first to third embodiments and the power semiconductor devices of Comparative Examples 1 and 2. It was confirmed that there were no voids or cracks in the gel-like insulating material in the power semiconductor devices 100A to 100C of the first to third embodiments. In contrast, it was confirmed that voids were generated in the gel-like insulating material in the power semiconductor devices 100D and 100E of Comparative Examples 1 and 2. [effect] As described above, the power semiconductor devices 100A-100C include a movable portion that expands and contracts in response to the pressure in the space inside the semiconductor device, at least in a portion of the case 4 or lid 6 that is not in contact with the insulating material 5. This prevents water from entering the power semiconductor devices 100A-100C, and minimizes changes in the pressure in the space inside the device even when the power semiconductor devices 100A-100C generate heat or are heated from the outside during testing, thereby preventing voids and cracks from occurring in the gel insulating material. As a result, a power semiconductor device that can suppress the occurrence of partial discharge and maintain a dielectric strength voltage can be realized.

[0066] The above-described embodiments are merely examples, and the present invention is not limited to these embodiments as long as the features of the invention are not impaired.

[0067] The present invention is not limited to the above-described embodiment, and includes other modifications and applications within the scope of the claims. [Explanation of symbols]

[0068] 1. Power semiconductor element (semiconductor element) 2. Insulated circuit board 2a Insulating substrate 2b circuit electrode 2c back electrode 2d brazing material 3 Heat dissipation base plate (heat dissipation base) 4 cases 5. Gel-type insulating material (insulating material) 6 Lid 7 Hole 8. Bonding materials (solder, sintered metal) 9. Joining materials (solder, sintered metal) 10. Adhesive 11 terminals 12 nuts 13 Cap 14 Ventilation holes 21, 23 Telescopic movable part 22, 24 Frame section 25 Gasket 26 Plunger 27 Outer cylinder 31 Space inside semiconductor device 32 Void 50, 51, 52 Moving parts 100A, 100B, 100C, 100D, 100E Power semiconductor device (semiconductor device)

Claims

1. a semiconductor substrate on which a semiconductor element is mounted; a housing that hermetically seals the semiconductor substrate; A semiconductor device comprising: the housing includes a pressure adjusting unit that changes the volume inside the housing in accordance with the pressure inside the housing; A semiconductor device comprising:

2. 2. The semiconductor device according to claim 1, The semiconductor device is characterized in that the pressure adjusting section has a movable section that expands and contracts in response to the pressure inside the housing.

3. 3. The semiconductor device according to claim 2, The semiconductor device is characterized in that at least a part of the movable portion is made of an elastic member.

4. 4. The semiconductor device according to claim 3, The semiconductor device is characterized in that the elastic member is made of a rubber-like organic material or a spring.

5. The semiconductor device according to any one of claims 2 to 4, a soundness evaluation unit that evaluates the soundness of the semiconductor device based on the amount of change in operation of the movable part; A semiconductor device comprising:

6. The semiconductor device according to any one of claims 2 to 4, The semiconductor device further comprises a gel-like insulating material provided inside the housing for insulating and sealing the semiconductor substrate.

7. The semiconductor device according to any one of claims 2 to 4, The semiconductor device further comprises an air opening portion for temporarily opening the inside of the casing to the outside air.

8. The semiconductor device according to any one of claims 2 to 4, A semiconductor device comprising: a limiter for limiting the operating range of a movable part of the pressure adjusting part.

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