JP2013033876A - Semiconductor module and spacer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the fluctuation of pressing force applied between constituent members constructing a semiconductor module due to a temperature change of the semiconductor module, in the semiconductor module in which electrode layers and electrode terminals of the semiconductor module are electrically connected by a pressure welding.SOLUTION: In a semiconductor module 1 comprising: semiconductor elements 2a to 2d; and an AC electrode terminal 3 and DC electrode terminals 4, 5 which are electrically connected to any of electrode layers of the semiconductor elements 2a to 2d, spacers 6 are provided between the AC electrode terminal 3 and the DC electrode terminals 4, 5. The spacers 6 are arranged in the vicinity of the semiconductor elements 2a to 2d. The spacers 6 are structured by insulating and covering the surface of spacer metal bodies. As the metal material constituting the spacers 6, a metal material having an expansion coefficient almost equal to an average thermal expansion coefficient of lamination parts of the semiconductor elements 2a to 2d is used.

Description

  The present invention relates to a semiconductor module that electrically connects an electrode layer and an electrode terminal of a semiconductor element by pressure welding.

  As a typical insulated power semiconductor module, there is an IGBT (Insulated Gate Bipolar Transistor) module used in a power converter such as an inverter. In addition, standards for “green green power semiconductor module” or “Isolated power semiconductor devices” represented by the IGBT module are established in JEC-2407-2007 and IEC60747-15, respectively.

  In a general green-type power semiconductor module, a semiconductor element such as an IGBT or a diode as a switching element is a copper circuit having a DBC (Direct Bond Copper) substrate (or DCB substrate) as an electrode layer provided on the lower surface of the semiconductor element. It is soldered on a foil and provided on a circuit (for example, Non-Patent Document 1). The DBC substrate is obtained by directly bonding a copper circuit foil to an insulating plate made of ceramics or the like.

  The electrode layer provided on the upper surface of the semiconductor element is electrically connected to the copper circuit foil on the DBC substrate by connecting an aluminum wire by a method such as ultrasonic bonding. A copper terminal (lead frame or bus bar) for connecting electricity from the copper circuit foil of the DBC substrate to the outside is connected to the copper circuit foil by soldering or the like. Furthermore, this area is surrounded by a (super) engineering plastic case and filled with silicon gel or the like for electric green.

  In recent years, the operating temperature of semiconductor elements has been increasing. When the operating temperature is 175 ° C. to 200 ° C., since this temperature is close to the melting point of the solder material, there are cases where a conventional solder material cannot be used. Therefore, as a material to be replaced with solder, for example, metal-based high-temperature solder (Bi, Zn, Au), compound-based high-temperature solder (Sn—Cu), low-temperature sintered metal (Ag powder, nanoAg), and the like have been proposed. In addition, SiC, which is a next-generation semiconductor element, has been reported to operate at 250 to 300 ° C.

  On the other hand, a flat pressure contact structure package has been proposed as a semiconductor module structure that does not use solder (Non-Patent Documents 1 and 2).

  In the flat pressure contact structure package, the contact terminal and the semiconductor element are connected and the semiconductor element and the substrate are connected by pressure contact. In a general flat pressure contact structure package, a guide for positioning the semiconductor element and the contact terminal is provided at an end portion of the semiconductor element (for example, IGBT, diode). Then, the semiconductor element is provided on a substrate (Mo substrate, DBC substrate, etc.) with the upper electrode layer of the semiconductor element in contact with the contact terminal. As described above, the contact terminal and the substrate are provided in the semiconductor module with the semiconductor element sandwiched therebetween.

  Since the flat pressure contact structure package has a flat structure, the semiconductor element can be cooled from both sides. For this reason, in general, both sides of the flat pressure contact structure package are pressed with heat sinks to cool both sides of the flat pressure contact structure package, and the heat sink is used as a conductive member. Furthermore, since the flat type pressure contact structure package connects the semiconductor elements and electrode terminals by pressure contact, the semiconductor elements are electrically and thermally connected to the outside without using solder.

  In a semiconductor module having a flat pressure contact structure, it is necessary to assemble the semiconductor module so that the pressure contact force is equally applied to each semiconductor element or the like. For example, pressure welding requires that the upper and lower heat sinks of the flat pressure contact structure package be electrically green, and the flat pressure contact structure package is pressed by a leaf spring, but the pressure contact force of this design is the electrode of the flat pressure contact structure package It is necessary to ensure that the post is applied evenly. These have know-how, and if the pressure contact is poor, the semiconductor element may be destroyed. In addition, the user performs the pressure contact between the heat sink and the flat pressure contact structure package mainly. In addition, skill is required to make full use of the heat sink and the leaf spring for pressure contact, which prevents the miniaturization of the circuit. For this reason, the flat type pressure contact structure package is applied to a limited apparatus, and a conventional type of insulated power semiconductor module that is easy to use is widely used instead.

  In order to improve the reliability of the semiconductor module such as temperature cycle and power cycle, it is necessary to improve the problem caused by the difference in thermal expansion coefficient of each member (semiconductor, metal, ceramics, etc.) constituting the semiconductor module. (For example, Patent Documents 1 to 3). For example, between the substrate and the copper base and between the substrate and the copper terminal, the shear stress acts on the solder connecting the copper and the ceramic due to the difference in thermal expansion coefficient between the copper and the ceramic. This shear stress may cause cracks in the solder and increase the thermal resistance or peel off the terminals. Similarly, cracks may also occur in the solder between the semiconductor element and the substrate. In addition, stress may be generated due to the difference in thermal expansion between aluminum and the semiconductor element at the connection portion of the aluminum wire on the semiconductor element, and the aluminum wire may be fatigued.

  As the power density increases, the bonding temperature between the electrode on the semiconductor element and the aluminum wire increases, and the shear stress of the solder and the stress of the aluminum wire increase. On the other hand, it is necessary to design the structure of the semiconductor module so that the influence of thermal expansion does not become apparent over the period until the design life of the semiconductor module is reached. With the advent of wideband cap semiconductor elements that can be used at high temperatures such as SiC and GaN, there is a demand for further reduction of the effects of thermal expansion. Further, semiconductor modules that make use of the performance of semiconductor elements that can be used at high temperatures, such as SiC and GaN, are also required to have improved reliability such as temperature cycle and power cycle of the semiconductor module.

  Therefore, in order to achieve high reliability, environmental friendliness, and convenience at the same time, there is a need for an easy-to-use insulated power semiconductor module that does not use solder bonding or wire bonding.

JP-A-11-17087 JP 2004-319991 A JP 2002-83915 A

IEEJ Technical Committee on High Performance and High Performance Power Devices and Power ICs, “Power Device and Power IC Handbook”, Corona, July 1996, p289, p336 Hiroshi Mori, Yasukazu Seki, “Recent Advances in Large Capacity IGBTs”, The Institute of Electrical Engineers of Japan, The Institute of Electrical Engineers of Japan, May 1998, Vol. 118 (5), pp. 274-277

  However, in a semiconductor module in which the electrode layer of the semiconductor element and the electrode terminal are electrically connected by pressure welding, the contact pressure is kept good when the contact pressure of the entire contact surface between the constituent members constituting the semiconductor module is not uniform. The current may be concentrated on the spot where it is. The local concentration of current on the contact surface may cause local thermal expansion and thermal deformation of members constituting the semiconductor module, and may impair the operation reliability of the semiconductor module.

  In addition, since the thermal expansion coefficients of the constituent members constituting the semiconductor module are different, the pressure contact force applied to the constituent members constituting the semiconductor module may change due to a temperature change of the semiconductor module or a semiconductor element provided in the semiconductor module. There is.

  In view of the above circumstances, the present invention provides a semiconductor module in which an electrode layer and an electrode terminal of a semiconductor element are electrically connected by pressure welding, and the pressure welding force applied to the constituent members constituting the semiconductor module is independent of the temperature of the semiconductor module. The object is to contribute to maintaining the range within a predetermined range, thereby contributing to improvement of the operation reliability of the semiconductor module.

  The semiconductor module of the present invention that achieves the above object is a semiconductor module in which an electrode layer and an electrode terminal of a semiconductor element are electrically connected by pressure welding, and the surface is insulated between the electrode terminals connected to the electrode layer of the semiconductor element. It is characterized by providing a spacer made of a coated metal.

  The semiconductor module of the present invention that achieves the above object is a semiconductor module in which an electrode layer and an electrode terminal of a semiconductor element are electrically connected by pressure welding, and a stacking direction of a stacked portion in which the electrode terminal and the semiconductor element are stacked In parallel, a spacer made of a metal whose surface is covered with an insulating coating is provided.

  The spacer of the present invention that achieves the above object is provided between electrode terminals connected to the electrode layer of the semiconductor element in a semiconductor module that electrically connects the electrode layer and electrode terminal of the semiconductor element by pressure welding. The spacer is characterized in that the surface of the metal member is covered with an insulating coating.

  In addition, the spacer of the present invention that achieves the above object is a semiconductor module that electrically connects an electrode layer and an electrode terminal of a semiconductor element by pressure contact, and a stacking direction of a stacked portion in which the semiconductor element and the electrode terminal are stacked The spacer is provided by insulatingly coating the surface of the metal member.

  According to the above invention, in the semiconductor module in which the electrode layer of the semiconductor element and the electrode terminal are electrically connected by pressure contact, the pressure contact force applied to the constituent members constituting the semiconductor module is predetermined regardless of the temperature of the semiconductor module. It can contribute to maintaining it within the specified range.

2 is a cross-sectional view of the semiconductor module according to Embodiment 1. FIG. 2 is a cross-sectional view of the semiconductor module according to the first embodiment, taken along line AA. FIG. It is an expanded sectional view of the heat radiator which concerns on Embodiment 1. FIG. It is a characteristic view which shows the relationship between the temperature of a laminated member, and the normal stress concerning a semiconductor element. 6 is a cross-sectional view of a semiconductor module according to Embodiment 2. FIG.

  A semiconductor module and a spacer according to an embodiment of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a cross-sectional view of main parts of a semiconductor module 1 according to Embodiment 1 of the present invention. The semiconductor module 1 according to the first embodiment of the present invention includes semiconductor elements 2a to 2d, an AC electrode terminal 3, DC electrode terminals 4 and 5, and a spacer 6.

  The semiconductor elements 2a and 2b are provided on the lower surface of the AC electrode terminal 3 via a stress buffer plate 7 (contact electrode), and the AC electrode terminal 3 and the P-side electrode layer (or N-side electrode layer of the semiconductor elements 2a and 2b). ) Are electrically connected. The semiconductor elements 2c and 2d are provided on the upper surface of the AC electrode terminal 3 via a stress buffer plate 7, and the AC electrode terminal 3 and the N-side electrode layer (or P-side electrode layer) of the semiconductor elements 2c and 2d are electrically connected. Connected to. In the description of the embodiment, for the sake of convenience, the top surface and the bottom surface are used, but the vertical direction does not limit the present invention in any way (the same applies to Embodiment 2 described later). Although not shown, an electrode layer (for example, aluminum) is formed in a film shape on the contact surfaces of the semiconductor elements 2a to 2d that are in contact with the stress buffer plate 7 by a method such as vapor deposition.

  A DC electrode terminal 4 (− pole) is provided via a stress buffer plate 7 on the surface opposite to the surface on which the AC electrode terminal 3 of the semiconductor elements 2a and 2b is provided, and the DC electrode terminal 4 and the semiconductor elements 2a and 2b are provided. N-side electrode layers (or P-side electrode layers) are electrically connected. Further, a DC electrode terminal 5 (+ pole) is provided via a stress buffer plate 7 on a surface opposite to the surface on which the AC electrode terminal 3 of the semiconductor elements 2c and 2d is provided, and the DC electrode terminal 5 and the semiconductor element 2c are provided. , 2d P-side electrode layer (or N-side electrode layer) is electrically connected.

  The spacer 6 is provided between the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5). The spacer 6 is configured by forming an insulating layer on the surface of a spacer body made of metal. As an insulating material for forming this insulating layer, for example, an epoxy resin, a silicon resin, a fluororesin, an aramid fiber, or the like is used. The insulating layer is formed by a method of coating the spacer body with the insulating material or a method of coating the spacer body with paper (sheet) made of the insulating material.

  2 is a cross-sectional view of the AA portion of the semiconductor module 1 shown in FIG. Hereinafter, the portion in the vicinity of the semiconductor element 2a will be described in detail, but the same applies to the portions in the vicinity of the other semiconductor elements 2b to 2f, and detailed description thereof will be omitted to avoid repetition.

  As shown in FIG. 2, the spacer 6 is disposed so as to surround the semiconductor element 2a. The spacer 6 is provided as close as possible to the semiconductor element 2a. By providing the spacer 6 in the vicinity of the semiconductor element 2a, a laminated member including the semiconductor element 2a (semiconductor element 2a, stress buffer plate 7, AC electrode terminal) even under any heat generation conditions (or heat dissipation conditions) of the semiconductor element 2a. 3. The temperature of the DC electrode terminal 4) and the spacer 6 can be made substantially equal.

  The thickness d of the spacer 6 is preferable because the heat dissipation is improved as it is thicker. However, since the thickness d of the spacer 6 is restricted by the distance between the semiconductor element 2a and the adjacent semiconductor element (for example, the semiconductor element 2b), the thickness d of the spacer 6 is It is appropriately selected according to the space formed in the semiconductor module 1 (size of the semiconductor module 1). When the semiconductor element 2a is a switching device, a gap is provided between the spacers 6, and the gate wiring 14 is provided in the gap, whereby a gate signal can be extracted from the gap. Further, when the semiconductor element 2a is not a switching device, the spacer 6 may be provided so as to surround the periphery of the semiconductor element 2a.

  The arrangement form of the spacers 6 is not limited to the form arranged so as to surround the semiconductor element 2a as illustrated in FIG. 2, but includes a plurality of semiconductor elements (for example, the semiconductor element 2a and the semiconductor element 2b). The pressure contact force applied to the contact surface between the semiconductor element 2a and the stress buffer plate 7 is within a predetermined range, and the pressure contact force applied to the contact surface between the semiconductor element 2a and the stress buffer plate 7 is uniform. The spacer 6 is appropriately disposed in the semiconductor module 1.

  The metal (spacer main body) constituting the spacer 6 is a portion laminated by the height of the spacer 6 among the constituent members constituting the semiconductor module 1 laminated in parallel with the spacer 6 in the pressing direction of the semiconductor element 2a ( Thereafter, a member having a thermal expansion coefficient (linear expansion coefficient) substantially the same as the average thermal expansion coefficient (linear expansion coefficient) of the laminated portion is selected. An average expansion coefficient is calculated | required by dividing the product of the thickness of each structural member which comprises the semiconductor module 1, and the thermal expansion coefficient of these structural members by the height of a laminated part.

In the semiconductor module 1 shown in FIG. 1, the stacked portion of the semiconductor elements 2a includes the semiconductor element 2a, the stress buffer plates 7 and 7, a part of the AC electrode terminal 3, and a part of the DC electrode terminal 4 (AC electrode terminal 3 and The depth of a fitting groove 9 described later in the DC electrode terminal 4 is shown. For example, as a component constituting the semiconductor module 1, a semiconductor element 2a (silicon semiconductor element, thermal expansion coefficient: 3 ppm / ° C., thickness: 0.3 mm), stress buffer plate 7 (tungsten stress buffer plate, thermal expansion coefficient) : 7 ppm / ° C., thickness: 0.5 mm), AC electrode terminal 3 and DC electrode terminal 4 (copper electrode terminal, thermal expansion coefficient: 16 ppm / ° C., thickness (depth of fitting groove 9): 0.5 mm ) Is used, the average coefficient of thermal expansion k of the stacked portion of the semiconductor element 2a is calculated as in equation (1), and is approximately 10.4 ppm / ° C.
k = (3 × 0.3 + 7 × 0.5 + 7 × 0.5 + 16 × 0.5 + 16 × 0.5) / (0.3 + 0.5 + 0.5 + 0.5 + 0.5) (1)
Examples of the material having a thermal expansion coefficient close to the average thermal expansion coefficient k calculated by the equation (1) include ferritic stainless steel (JIS standard SUS430). Therefore, in the embodiment, as an example of the spacer 6, a ferritic stainless steel whose surface is covered with an aramid fiber insulating paper is used. Since the insulating layer formed on the surface of the spacer 6 is smaller than the height of the spacer 6 (direction in which the semiconductor element 2a is pressed), the thermal expansion coefficient of the spacer 6 is the thermal expansion coefficient of the spacer body. Can be approximated by

  The thickness of the insulating layer formed on the surface of the spacer 6 does not conduct due to the voltage applied between the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5) (can withstand a potential difference between the electrode terminals). ) About a thickness. For example, when there is a potential difference of 1000 V between the AC electrode terminal 3 and the DC electrode terminal 4 (DC electrode terminal 5), the potential difference between the electrode terminals can be endured if the thickness of the insulating layer is 250 μm or more.

  The spacer 6 is not limited to this embodiment, and the spacer 6 may be made of other stainless steel, copper-molybdenum-based composite material (CuMo), aluminum-silicon carbide-based composite material (AlSiC), or the like. In this case, an insulating layer is formed on the surface of the spacer body made of a material excellent in the above. CuMo can control a thermal expansion coefficient between 7-10 ppm / degrees C by changing the composition ratio of Cu and Mo. Also, AlSiC has a coefficient of thermal expansion of between 6 and 15 ppm / ° C. by changing the composition ratio of Al and SiC or by gradually changing the composition of Al and SiC in the thickness direction (composition gradation). Can be controlled.

  For the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5), a well-known electrode material (such as copper or aluminum) is used. A fitting groove 9 into which the spacer 6 is fitted is formed in the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5). The depth of the fitting groove 9 may be a depth that can hold the spacer 6. By adjusting the depth of the fitting groove 9, the average thermal expansion coefficient of the stacked portion of the semiconductor elements 2 a can be made closer to the thermal expansion coefficient of the spacer 6. For example, when the material constituting the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5) is copper (thermal expansion coefficient is 16 ppm / ° C.), copper is a constituent material constituting the other semiconductor module 1. The coefficient of thermal expansion is greater than As a result, as the depth of the fitting groove 9 is increased, a material having a large thermal expansion coefficient can be used for the spacer 6. Further, when the fitting groove 9 is formed so that the end face of the spacer 6 and the bottom of the fitting groove 9 are in surface contact, the pressure contact force applied between the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5). Can be supported by the end face of the spacer 6, and the contact surface between the AC electrode terminal 3 and the DC electrode terminal 4 (or DC electrode terminal 5) and the spacer 6 becomes large, so that the heat conduction efficiency can be improved.

  In the vicinity of the case 10 of the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5), a stress buffer groove 11 for reducing stress due to a temperature difference between the semiconductor element 2a and the case 10 is formed. . Although not shown, a holder for positioning the semiconductor element 2a is formed between the AC electrode terminal 3 and the DC electrode terminal 4 (or DC electrode terminal 5), and the horizontal positioning of the semiconductor element 2a is performed. And fixing is performed. In addition, it is good also as a form which the spacer 6 positions the semiconductor element 2a, without forming a holder.

  Insulating plates 12 are respectively provided on the surface of the DC electrode terminal 4 opposite to the surface to which the semiconductor elements 2a and 2b are connected and the surface of the DC electrode terminal 5 opposite to the surface to which the semiconductor elements 2c and 2d are connected. A radiator 8 is provided. A groove 8a for providing an O-ring is formed in the vicinity of the side end of the surface where the radiators 8, 8 face each other, and a case 10 is provided in the groove 8a via an O-ring made of fluoro rubber. . By directly joining the insulating plate 12 and the case 10 to the radiator 8, the heat dissipation of the semiconductor module 1 is improved. Moreover, the airtightness of the semiconductor module 1 improves by providing the case 10 via the O-ring between the side end portions of the radiator 8. In addition, you may seal between the heat radiator 8 and the case 10 with an adhesive etc. instead of providing an O-ring. Further, the periphery of the spacer 6 may be molded without providing the case 10.

  FIG. 3 shows an enlarged cross-sectional view of the radiator 8 provided in the semiconductor module 1. As shown in FIG. 3, a groove 8 b is formed in the radiator 8, and a spring 13 (pressing the insulating plate 12 (each component member constituting the stacked portion of the semiconductor elements 2 a) in the groove 8 b in the direction of the semiconductor element 2 a. Elastic member). When the radiator 8 is fixed in a state where the spring 13 is provided in the groove 8b, the insulating plate 12, the DC electrode terminal 4 (or the DC electrode terminal 5), and the stress buffer plate 7 are semiconductors by the elastic force of the spring 13. It is pressed in the direction of the element 2a. As shown in FIG. 1, when the radiator 8 is provided above and below the semiconductor module 1, a groove 8b is formed in each radiator 8, and a spring 13 is provided in the groove 8b.

  The radiator 8 is formed with a refrigerant path 8c through which a refrigerant (liquid or gas) flows. By forming a groove 8b between the refrigerant paths 8c, the spring 13 provided in the groove 8b is cooled by the refrigerant. Is done. As a result, regardless of the operating conditions of the semiconductor module 1 (the operating temperature of the semiconductor module 1 and the heat dissipation conditions of the semiconductor module 1), the temperature of the spring 13 can be kept relatively low and the temperature fluctuation range is small. Therefore, the variation of the elastic force of the spring 13 caused by the thermal expansion of the spring 13 (the pressure at which the spring 13 presses the insulating plate 12) or the difference in the thermal expansion of the radiator 8 and the spring 13 is reduced. Can do.

  FIG. 4 shows the result of a simulation test (simulation) of the pressure contact force applied to the surface of the semiconductor element 2a when the temperature of the semiconductor module 1 is changed in the semiconductor module 1 having the above configuration.

Example 1
The semiconductor module according to Example 1 is the same as the spacer 6 in the semiconductor module 1 shown in FIG. 1, but the thermal expansion coefficient of the spacer 6 matches the average thermal expansion coefficient of the stacked portion of the semiconductor elements 2 a with an error of 10%. We used what is. The semiconductor module of Example 1 was configured by applying a 5 MPa pressure contact force to the semiconductor element 2a by the spring 13 at 20 ° C. The case 10 is made of aluminum oxide (Al ₂ O ₃ ), and the insulating plate 12 is a Si ₃ N ₄ ceramic plate (thickness, 0.3 mm) bonded with 0.3 mm copper. Was used.

  Then, when the temperature of the stacked portion of the semiconductor element 2a and the spacer 6 is increased to an arbitrary temperature (maximum 180 ° C.), the change of the pressure force acting on the surface of the semiconductor element 2a was simulated by simulation software (ANSYS). . In the structural analysis by ANSYS, it was assumed that the case 10 was at room temperature, and the stacked portion of the semiconductor element 2a and the spacer 6 were at the same temperature.

(Example 2)
In the semiconductor module according to the second embodiment, in the semiconductor module 1 shown in FIG. 1, as the spacer 6, the thermal expansion coefficient of the spacer 6 matches the thermal expansion coefficient of the stacked portion of the semiconductor elements 2a with an error of 2%. A thing was used. Other configurations and conditions are the same as those in the first embodiment.

(Comparative Example 1)
As the semiconductor module according to Comparative Example 1, the semiconductor module 1 shown in FIG. Other configurations and conditions are the same as those in the first embodiment.

  When Examples 1 and 2 in the characteristic diagram shown in FIG. 4 are compared with Comparative Example 1, by providing the spacer 6 in the semiconductor module, the pressure contact applied to the surface of the semiconductor element 2a as the temperature of the semiconductor element 2a and the spacer 6 increases. It can be seen that the increase in force is suppressed. For example, when the pressure contact force applied to the surface of the semiconductor element 2a exceeds 100 MPa, the semiconductor element 2a may be damaged. However, as in Examples 1 and 2, the first embodiment of the present invention is located near the semiconductor element 2a. By providing such a spacer 6, it is possible to reduce an increase in pressure contact force applied to the surface of the semiconductor element 2 a with respect to a temperature change of the semiconductor element 2 a (semiconductor module 1).

  Further, comparing Example 1 and Example 2 in the characteristic diagram shown in FIG. 4, the closer the value of the thermal expansion coefficient of the spacer 6 is to the average thermal expansion coefficient of the stacked portion of the semiconductor elements 2 a in the vicinity of the spacer 6, It can be seen that an increase in the pressing force applied to the surface of the semiconductor element 2a due to the temperature rise of the semiconductor element 2a (spacer 6) is suppressed.

  As described above, by using a material having the same thermal expansion coefficient as an error within 10% of the average thermal expansion coefficient of the laminated portion of the semiconductor element 2a in the vicinity of the spacer 6 as the metal material constituting the spacer 6, the semiconductor element 2a It is possible to suppress an increase in pressure contact force acting on the surface of the semiconductor element 2a as the temperature rises. Furthermore, by using a material having the same thermal expansion coefficient as the error within 2% of the average thermal expansion coefficient of the stacked portion of the semiconductor elements 2 a in the vicinity of the spacer 6 as the metal material constituting the spacer 6, the semiconductor element 2 a ( The increase of the pressure contact force acting on the surface of the semiconductor element 2a accompanying the temperature increase of the spacer 6) is remarkably suppressed.

  When the temperature of the semiconductor module 1 (semiconductor element 2a) rises, the stacked portion of the semiconductor element 2a thermally expands in the height direction (that is, the stacked direction of the stacked portion). On the other hand, the case 10 is provided at a position away from the semiconductor element 2a, and the temperature distribution is considered to be different from that of the semiconductor element 2a. When the temperature of the case 10 is lower than the temperature around the semiconductor element 2a, the thermal expansion amount of the case 10 is smaller than the thermal expansion amount of the stacked portion of the semiconductor element 2a. In this case, assuming that the radiator 8 is not deformed, the height of the semiconductor module 1 is limited to the height of the case 10. As a result, in a state where the thickness of the stacked portion of the semiconductor element 2a is limited by the case 10, the stacked portion of the semiconductor element 2a is thermally expanded to form each component member (particularly, the surface of the semiconductor element 2a) that forms the semiconductor module 1. An excessive pressure contact force is applied between them.

  Therefore, by providing the spacer 6 in the vicinity of the semiconductor element 2a, the pressing force acting on the semiconductor element 2a can be shared by the spacer 6, and it is possible to suppress an excessive pressure contact force from being applied to the semiconductor element 2a. . If the average thermal expansion coefficient of the laminated portion of the semiconductor element 2a is close to the thermal expansion coefficient of the spacer 6, the spacer 6 also thermally expands by substantially the same amount in accordance with the thermal expansion of the laminated portion, so that the height increases. Regardless of the temperature of 1, the pressing force applied to the laminated portion can be shared by the spacer 6. The closer the average thermal expansion coefficient of the stacked portion and the value of the thermal expansion coefficient of the spacer 6 are, the closer the stacked portion of the semiconductor element 2a and the spacer 6 have with the temperature of the stacked portion of the semiconductor element 2a (the temperature of the spacer 6). The amount of thermal expansion becomes substantially equal. As a result, it is possible to reduce an increase in pressure contact force between the constituent members forming the semiconductor module 1 (particularly, the surface of the semiconductor element 2a), which is caused by the temperature rise in the stacked portion of the semiconductor element 2a.

(Embodiment 2)
FIG. 5 is a cross-sectional view of a main part of the semiconductor module 15 according to the second embodiment of the present invention. The semiconductor module 15 according to the second embodiment of the present invention is different from the semiconductor module 1 according to the first embodiment in the arrangement form of the DC electrode terminals 4 and 5 and the AC electrode terminal 3. Therefore, the same reference numerals are given to the same configurations as those of the semiconductor module 1 according to the first embodiment, and detailed description thereof is omitted.

  As shown in FIG. 5, the semiconductor module 15 according to the second embodiment of the present invention includes semiconductor elements 2 a and 2 c, AC electrode terminals 3, DC electrode terminals 4 and 5, and a spacer 6.

  The semiconductor elements 2a and 2c are provided on the lower surface of the AC electrode terminal 3 via a stress buffer plate 7 (contact electrode), respectively, and the P-side electrode layer (or N-side electrode layer) of the semiconductor elements 2a and 2c and the AC electrode terminal 3 are electrically connected.

  On the surface opposite to the surface on which the AC electrode terminal 3 of the semiconductor element 2a is provided, a DC electrode terminal 4 (-pole) is provided via a stress buffer plate 7, and the N-side electrode layer (or P) of the semiconductor element 2a is provided. Side electrode layer) and the DC electrode terminal 4 are electrically connected. On the other hand, on the surface opposite to the surface on which the AC electrode terminal 3 of the semiconductor element 2c is provided, the DC electrode terminal 5 (+ pole) is provided via the stress buffer plate 7, and the P-side electrode layer (or the semiconductor element 2c) (or , N-side electrode layer) and the DC electrode terminal 5 are electrically connected.

  The spacer 6 is provided between the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5). A fitting groove 9 into which the spacer 6 is fitted is formed in the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5), and the spacer 6 is fitted into the fitting groove 9.

  In the vicinity of the case 10 of the AC electrode terminal 3 and the DC electrode terminal 4 (or the DC electrode terminal 5), a stress buffering groove 11 for reducing stress due to a temperature difference between the semiconductor elements 2a and 2c and the case 10 is formed. The

  A radiator 8 is provided on the upper surface of the AC electrode terminal 3 and the lower surfaces of the DC electrode terminals 4 and 5 via insulating plates 12. Grooves 8a for providing O-rings are formed in the vicinity of the side ends of the surfaces where these radiators 8, 8 face each other, and a case 10 is provided between the side ends of the radiators 8, 8 via O-rings. It is done.

  The radiator 8 has a groove (not shown) provided with a spring 13 (elastic member) that presses the insulating plate 12 (and each component constituting the semiconductor module 15) in the direction of the semiconductor element 2a (or the semiconductor element 2c). Is formed. And the spring 13 is provided in this groove part, and the heat radiator 8 is fixed. As a result, the insulating plate 12, the AC electrode terminal 3, the DC electrode terminals 4 and 5, and the stress buffer plate 7 are pressed in the direction of the semiconductor element 2a (or the semiconductor element 2c) by the elastic force of the spring 13. The radiator 8 is formed with a refrigerant path 8c through which a refrigerant (liquid or gas) flows. By forming a groove part in which the spring 13 is provided between the refrigerant path 8c, the spring 13 provided in the groove part is cooled. Is done.

  Similar to the semiconductor module 1 according to the first embodiment, the semiconductor module 15 according to the second embodiment provides the semiconductor elements 2a and 2c by providing the insulating spacer 6 made of metal in the vicinity of the semiconductor elements 2a and 2c. It is possible to apply a pressing force within a certain range. Further, by providing the spring 13 in the radiator 8, it is possible to reduce the influence of the operating condition of the semiconductor module 15 (the temperature of the semiconductor elements 2 a and 2 c) on the elastic force of the spring 13. In the semiconductor module 15 according to the second embodiment, since the AC electrode terminal 3 is disposed at a position close to the radiator 8, in addition to the effects of the semiconductor module 1 according to the first embodiment, the AC electrode terminal 3 heat dissipation is improved.

  As described above with reference to specific embodiments, according to the semiconductor module of the present invention, by providing the semiconductor module with the spacer made of metal whose surface is covered with insulation, the temperature of the semiconductor element increases. Since the spacer thermally expands, it is possible to prevent an excessive pressing force from being applied to the semiconductor element. In other words, regardless of the temperature distribution inside the semiconductor module, the operating conditions of the semiconductor element, or the heat dissipation conditions, the thermal expansion amount (thickness direction of the laminated part) of the laminated part of the semiconductor element accompanying the temperature rise of the semiconductor element and the vicinity of this laminated part Since the thermal expansion amounts of the spacers to be arranged are substantially equal, it is possible to maintain the pressure contact force applied to the interface between the constituent members forming the stacked portion such as the semiconductor element in an appropriate pressure range. Therefore, an appropriate contact pressure (pressure contact force) can be applied to the semiconductor element without applying a large local stress to each component constituting the semiconductor module even in any operating environment and operating temperature of the semiconductor module. . As a result, the occurrence of abnormal thermal runaway can be prevented without increasing the contact thermal resistance and the contact electrical resistance at the interfaces of the constituent members constituting the semiconductor module, including the surface of the semiconductor element.

  Further, according to the spacer of the present invention, it is easy to design so that an appropriate pressure contact force is applied to the semiconductor element. That is, when a resin or plastic material is used as a material for the spacer, the resin or plastic material has a creep characteristic (a characteristic that the deformation of the material increases with time under a certain load) The coefficient of thermal expansion changes greatly before and after the glass transition temperature. Furthermore, it is difficult to predict deformation and changes in physical properties of resins and plastic materials due to anisotropy in physical properties such as a coefficient of thermal expansion. Therefore, like the spacer of the present invention, by using a spacer made of a metal having an insulating coating layer formed on the surface as the spacer, the thickness in the thickness direction of the stacked portion of the semiconductor element is maintained in the pressure contact type semiconductor module. Compared to the case where resin or plastic is used as the material of the spacer, the spacer 6 can be designed so that an appropriate pressure contact force is applied to the semiconductor element according to the operating conditions of the semiconductor module (particularly in a high temperature environment). It becomes easy.

  In addition, when a metal material constituting the spacer is made of a material having a thermal expansion coefficient that is substantially equal to the average thermal expansion coefficient of the stacked portion of the semiconductor element, the temperature of the semiconductor module (semiconductor element) increases as the temperature of the semiconductor element increases. The thermal expansion amounts of the stacked portion and the spacer are substantially equal, and an increase in the pressure contact force applied to the surface of the semiconductor element that occurs as the temperature of the semiconductor module (semiconductor element) increases can be reduced. That is, by making the thermal expansion amounts of the semiconductor element stack and the spacer substantially the same, the height of the semiconductor element stack and the spacer becomes substantially equal regardless of the temperature in the vicinity of the semiconductor element stack including the semiconductor element. The pressure contact force applied between the constituent members constituting the semiconductor module (particularly the surface of the semiconductor element) can be set within a predetermined design value range. That is, even when the semiconductor module operates in a high temperature environment, the pressure contact force applied to the surface (electrode surface) of the semiconductor element can be kept within a certain range (for example, 5 to 10 MPa). In particular, an appropriate contact pressure can be maintained on the front and back surfaces of a semiconductor element in which an electrode layer such as aluminum (Al) is formed by vapor deposition. As a result, it is possible to prevent damage to the front and back surfaces (electrode layers) of the semiconductor element due to excessive pressure contact with the semiconductor element. Furthermore, since the contact pressure as uniform as possible can be ensured with respect to the entire contact surface between the constituent members constituting the semiconductor module, the reliability of the semiconductor module is improved.

  Further, by providing the spacer in the semiconductor module, a heat radiation path is formed in the pressure contact direction in parallel with the stacked portion of the semiconductor elements, so that the heat radiation performance of the semiconductor module is improved. That is, the heat dissipation of the semiconductor module is improved by forming the spacer with a metal material having a high thermal conductivity. Since the surface of this spacer is covered with insulation, there is no fear of short-circuiting by the spacer, and it can be provided near the semiconductor element that is a heating element, and even if the spacer is dropped, short-circuiting in the semiconductor module is prevented. As a result, the safety of the semiconductor module is improved.

  In general, in a semiconductor module in which an electrode layer and an electrode terminal of a semiconductor element are electrically connected by pressure contact, the heat dissipation of the semiconductor module is likely to change when the contact pressure between the constituent members constituting the semiconductor module changes. That is, at a portion where the contact pressure is low, the electrical conductivity is reduced, and the path for radiating Joule heat due to energization is narrowed. On the other hand, Joule heat is generated due to the concentration of current at a location where good contact is maintained. As a result, the temperature of the specific member locally increases. If the member is locally thermally expanded or deformed, it becomes difficult to maintain a uniform contact pressure at the contact surface between the members.

  In the semiconductor module of the present invention, the contact pressure between the members can be ensured to be equal to or higher than a certain pressure (for example, 1 MPa) by providing a spacer made of a metal whose surface is insulated in the semiconductor module in the vicinity of the semiconductor element. As a result, local concentration of stress can be prevented and heat dissipation of the semiconductor module can be maintained, so that the reliability of the semiconductor module is improved.

  Further, by forming a fitting groove into which the spacer is fitted in the AC electrode terminal (and DC electrode terminal), the lateral displacement of the spacer can be prevented, and the depth of the fitting groove can be adjusted to stack the semiconductor elements. The average thermal expansion coefficient of the portion can be made substantially equal to the thermal expansion coefficient of the spacer. By adjusting the average thermal expansion coefficient of the laminated portion, a material having a larger thermal expansion coefficient can be used as the material constituting the spacer. As a result, since the material having high thermal conductivity and matching with the effective thermal expansion coefficient of the stacked portion of the semiconductor element can be selected as the material of the spacer, the reliability and heat dissipation of the semiconductor module are improved. In addition, since the mechanical strength and rigidity of the AC electrode terminal and the DC electrode terminal decrease as the depth of the fitting groove increases and the area (cross-sectional area) in which the spacer of the fitting groove fits increases, The depth of the fitting groove and the size of the cross-sectional area are appropriately set in consideration of the mechanical strength of the electrode terminal (or DC electrode terminal) and the thermal expansion coefficient of the spacer.

  Further, by forming a stress buffering groove between the case of the AC electrode terminal (or DC electrode terminal) and the laminated portion (or spacer) of the semiconductor element, the laminated portion (or spacer) of the semiconductor element and the case The influence of thermal stress due to the temperature difference (and the difference in thermal expansion coefficient) can be reduced. That is, it is possible to reduce stress (shear stress or the like) applied to the constituent members constituting the semiconductor module such as the AC electrode terminal (and DC electrode terminal), the case, and the semiconductor element.

  In the semiconductor module of the present invention, if the insulating material and the radiator are directly connected to the interface between the insulating material and the radiator without using thermal grease or the like, the heat dissipation of the semiconductor module is further improved.

  In addition, by forming a groove portion in the heat radiator provided in the semiconductor module for providing an elastic member (spring) that presses the electrode terminal in the direction of the semiconductor element, the temperature change (temperature rise) of the elastic member during operation of the semiconductor module is small. Therefore, the contraction length from the natural length of the elastic member resulting from the difference in thermal expansion coefficient between the elastic member and the radiator (the pressing force that the elastic member applies to each component constituting the semiconductor module) varies depending on the operating conditions of the semiconductor module. Can be suppressed.

  Although the present invention has been described in detail only for the specific examples described above, it is obvious to those skilled in the art that various changes and modifications can be made within the scope of the technical idea of the present invention. It goes without saying that such variations and modifications belong to the semiconductor module of the present invention and the spacer of the present invention.

  For example, as in the spacer structure of the present invention, the case provided in the semiconductor module is made of metal and the surface thereof is covered with insulation, so that the case is thermally expanded in accordance with the temperature change of the laminated portion of the semiconductor element. Can be made. As a result, if the case does not thermally expand, the dimensions of the stacked portion of the semiconductor element and the case due to the thermal expansion of the stacked portion of the semiconductor element absorbed by the deformation of the heat sink and other components constituting the semiconductor module The deviation can be absorbed by the thermal expansion of the case. In addition, since the deformation difference due to thermal expansion of the radiator and other components is reduced, the sealing performance for blocking the entry of foreign matter from the outside of the semiconductor module is improved. Further, by absorbing the thermal expansion of the stacked portion of the semiconductor elements by the thermal expansion of the case, the pressure contact force applied to the interface between the constituent members constituting the semiconductor module can be within a predetermined range. That is, the pressure contact force applied to the interface between the members constituting the stacked portion of the semiconductor element can be set within a predetermined range regardless of the temperature change in the semiconductor module, and the reliability of the semiconductor module is improved. Therefore, it is possible to prevent a decrease in contact thermal resistance and an increase in electrical resistance due to a decrease in contact pressure between members constituting the stacked portion of the semiconductor element, and damage to the surface of the semiconductor element due to an increase in this contact pressure. Can be prevented.

  Further, the type of the semiconductor element and the arrangement form of the semiconductor element and the electrode terminal can be appropriately changed according to the use of the semiconductor module. The semiconductor module can be used as an inverter, a converter, and the like, and a semiconductor element (IGBT), a thyristor (GTO thyristor, etc.), a transistor (MOSFET, etc.), and a diode (FWD, etc.) are appropriately selected according to each application. . For example, when a semiconductor module is used as an inverter, an inverter circuit in which a plurality of switching elements and diodes are incorporated in parallel is formed. On the other hand, when using a semiconductor module as a converter, a converter circuit is comprised only by a rectifier element (diode).

  Further, the arrangement form of the spacers is not limited to the form provided between the electrode terminals as in the embodiment. For example, the arrangement form of the spacers is parallel to the stacking direction of the stacked portion including the semiconductor elements and the electrode terminals in the semiconductor module. If it arrange | positions to, the effect similar to embodiment can be acquired. In other words, the purpose of providing the spacer in the semiconductor module is to increase the mechanical strength (resistance to vibration, etc.) in the thickness direction of the semiconductor module, to maintain horizontal insulation between adjacent semiconductor elements, and to improve the heat dissipation of the semiconductor module. Although the spacer is provided for any purpose, the thermal expansion coefficient of the spacer is substantially equal to the average thermal expansion coefficient of the stacked portion including the semiconductor element provided in a location close to the spacer. As a result, a uniform pressure contact force can be applied to the semiconductor element regardless of the temperature of the semiconductor module (semiconductor element).

DESCRIPTION OF SYMBOLS 1,15 ... Semiconductor module 2a-2f ... Semiconductor element 3 ... AC electrode terminal (1st electrode terminal)
4 ... DC electrode terminal (-pole) (second electrode terminal)
5 ... DC electrode terminal (+ electrode) (second electrode terminal)
6 ... Spacer 7 ... Stress buffer plate 8 ... Radiator 8b ... Groove 9 ... Fitting groove 10 ... Case (frame)
11 ... Stress buffer groove 12 ... Insulating plate 13 ... Spring (elastic member)

Claims (12)

A semiconductor element;
A first electrode terminal electrically connected to the electrode layer of the semiconductor element;
A second electrode terminal electrically connected to the other electrode layer of the semiconductor element;
A spacer made of a metal whose surface is insulated and provided between the first electrode terminal and the second electrode terminal;
A semiconductor module comprising: The semiconductor module according to claim 1, wherein a thermal expansion coefficient of the spacer is substantially equal to an average thermal expansion coefficient of a stacked portion of semiconductor elements provided in the vicinity of the spacer. 3. The semiconductor module according to claim 2, wherein a thermal expansion coefficient of the spacer is equal to an average thermal expansion coefficient of a stacked portion of semiconductor elements provided in the vicinity of the spacer within an error of 10%. The semiconductor module according to claim 1, wherein a fitting groove into which the spacer is fitted is formed in at least one of the first electrode terminal and the second electrode terminal. The depth of the fitting groove is adjusted, and the average expansion coefficient of the stacked portion is adjusted so that the thermal expansion coefficient of the spacer and the average expansion coefficient of the stacked portion are substantially equal. 5. The semiconductor module according to 4. Forming the fitting groove such that the bottom of the fitting groove and the end face of the spacer are in surface contact;
The semiconductor module according to claim 4. A radiator is provided through an insulating plate on at least one of the first electrode terminal and the second electrode terminal,
The semiconductor module according to any one of claims 1 to 6, wherein a groove is provided in the radiator to provide an elastic member that presses the insulating plate toward the semiconductor element. The semiconductor module according to claim 7, wherein a casing is provided on a side end portion of the radiator through an O-ring. 9. The semiconductor module according to claim 1, wherein a stress buffering groove is formed in at least one of the first electrode terminal and the second electrode terminal. 10. A semiconductor element;
A first electrode terminal electrically connected to the electrode layer of the semiconductor element;
A second electrode terminal electrically connected to the other electrode layer of the semiconductor element;
In a semiconductor module having
A semiconductor module comprising a spacer made of a metal whose surface is insulated and coated in parallel with a stacking direction of a stacked portion in which the first electrode terminal, the semiconductor element, and the second electrode terminal are stacked. In the semiconductor module for electrically connecting the electrode layer of the semiconductor element and the electrode terminal by pressure contact, a spacer provided between the electrode terminals connected to the electrode layer of the semiconductor element,
The spacer is formed by insulatingly coating the surface of a metal member. In a semiconductor module for electrically connecting an electrode layer and an electrode terminal of a semiconductor element by pressure contact, a spacer provided in parallel with a stacking direction of a stacked portion in which the semiconductor element and the electrode terminal are stacked,
The spacer is formed by insulatingly coating the surface of a metal member.

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