JP2013179230A - Semiconductor module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve convenience in assembling a semiconductor module having the gate electrode layers and the gate electrode terminals of semiconductor elements electrically connected by pressing them to contact each other, thereby improving the operational reliability of the semiconductor module.SOLUTION: A gate electrode post 3 is created on a gate electrode layer 8 of a semiconductor element 2. An insulation case 4 is created on the semiconductor element 2 so as to cover the gate electrode post 3. A groove 4a is formed on a surface of the insulation case 4 facing the gate electrode layer 8, and a spring 5 for pressing the gate electrode post 3 to touch the gate electrode layer 8 is created in the groove 4a. An insertion hole 4b through which a gate electrode terminal 6 is inserted is formed in the insulation case 4, and the gate electrode terminal 6 is inserted through the insulation case 4 to touch the gate electrode post 3 under pressure, whereby the gate electrode terminal 6 and the gate electrode layer 8 are electrically connected via the gate electrode post 3.

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.

  In recent years, high-voltage, high-capacity IGBTs (Insulated Gate Bipolar Transistors) have been developed for insulated power semiconductor modules used in fields such as industrial and vehicle systems, transformers, and power converters such as inverters. Has been applied. Standards for “insulated power semiconductor modules” or “Isolated power semiconductor devices” represented by this IGBT module are established in JEC-2407-2007 and IEC60747-15, respectively.

  In a general insulated power semiconductor module, semiconductor elements such as IGBTs and diodes that are switching elements are soldered onto a DBC (Direct Bond Copper) -based copper circuit foil via an electrode layer provided on the lower surface of the semiconductor element. (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.

  An aluminum wire is connected to the electrode layer provided on the upper surface of the semiconductor element by a method such as ultrasonic bonding. This aluminum wire is electrically connected to, for example, a copper circuit foil on the DBC substrate. A copper terminal (lead frame or bus bar) for connecting to the outside from the copper circuit foil of the DBC substrate is connected to the copper circuit foil by soldering. In addition, this is surrounded by a (super) engineering plastic case, which is filled with silicone gel for electrical insulation.

  In recent years, the operating temperature of semiconductor elements has been increasing. For example, a SiC semiconductor, which is a next-generation semiconductor element, has been reported to operate at 250 to 300 ° C. When the operating temperature is 175 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 nanopaste), and the like have been proposed.

  Further, 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). The flat type pressure contact structure package performs electrical connection between the electrode layer of the semiconductor element and the contact terminal, and electrical connection between the electrode layer of the semiconductor element and the substrate 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). The semiconductor element is provided on a substrate (such as a Mo substrate or a DBC substrate) with the upper electrode layer of the semiconductor element in contact with the contact terminal. That is, 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. Further, since the flat pressure contact structure package connects the semiconductor element and the electrode terminal by pressure contact, the semiconductor element is electrically and thermally connected to the outside without using solder.

  In flat pressure welding structure semiconductor modules, it is necessary to electrically insulate the heat sinks above and below the flat pressure welding package that presses the semiconductor module, and the flat pressure welding package is pressed with leaf springs. It is necessary to ensure that the force is evenly applied to the electrode posts of the flat pressure contact structure package. 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, a semiconductor module having a flat pressure contact structure requires skill to be fully used, for example, because the heat sink and the leaf spring for pressure contact prevent the miniaturization of the circuit. For these reasons, 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 temperature cycle, power cycle, etc. of a semiconductor module having a semiconductor element operable at high temperature, the thermal expansion coefficient of each member (member made of semiconductor, metal, ceramics, etc.) constituting the semiconductor module It is necessary to solve the problems caused by the differences. For example, since the thermal expansion coefficients of copper and ceramics are different between the substrate and the copper base and between the substrate and the copper terminal, a shear stress acts on the solder connecting the copper and the ceramic when the temperature of the semiconductor module rises. This shear stress may cause cracks in the solder and increase the thermal resistance or peel off the electrode terminals. Similarly, the solder between the semiconductor element and the substrate may be cracked. In addition, depending on conditions, it is considered that 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 of semiconductor modules increases year by year, the junction temperature inside the semiconductor element such as the junction between the electrode layer of 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 required to further improve the reliability of semiconductor modules such as temperature cycle and power cycle.

  Therefore, in order to achieve high reliability, environmental friendliness, and convenience of the semiconductor module at the same time, it is easy to cool on both sides without using solder joint or wire bond, and the insulation type power semiconductor module is advantageous in terms of heat dissipation. Is in the spotlight again.

  As shown in FIG. 2, the conventional semiconductor module 13 is configured using an insulated gate semiconductor element 2 such as an IGBT or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Then, the control gate terminal 14 and the control emitter terminal 15 (or control source terminal) are drawn out of the semiconductor module 13. The gate terminal 14 and the gate electrode layer 8 are connected by connecting the copper circuit foil 18 provided with the chip resistor 17 and the gate terminal 14 with the aluminum wire 16, and connecting the chip resistor 17 and the gate electrode layer 8 with the aluminum wire 16. It is done by connecting with. The emitter terminal 15 and the emitter electrode layer 7 are connected by connecting the emitter terminal 15 and the emitter electrode layer 7 with an aluminum wire 16. The aluminum wire 16 is connected using a method such as ultrasonic bonding.

  There is a demand for a highly reliable semiconductor module that does not use a connection method using an aluminum wire 16 to extract control signals from the gate electrode layer 8 and the emitter electrode layer 7 (or source electrode layer) (for example, Patent Document 1). ). In addition, a highly reliable semiconductor module that does not use the chip resistor 17 between the gate electrode layer 8 and the gate terminal 14 is required.

  Therefore, prior to the present invention, the inventors provided a semiconductor module 19 in which a leaf spring-like gate electrode terminal 20 having the same resistance value as that of the chip resistor 17 as shown in FIG. developed. In this semiconductor module 19, the gate electrode terminal 20 is formed in a leaf spring shape, and the end of the gate electrode terminal 20 is in pressure contact with the gate electrode layer 8 within a certain pressure range. Since the gate electrode terminal 20 has the function of the chip resistor 17, the joint portion of the aluminum wire 16 is reduced as compared with the circuit of the conventional semiconductor module 13, and the operation reliability and assembly convenience of the semiconductor module 19 are improved. To do.

Special table 2007-507080 gazette

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, the area of the gate electrode layer formed in the semiconductor element is small, and when the semiconductor module is configured by providing the gate electrode terminal in pressure contact with the gate electrode layer, it may be difficult to align the gate electrode terminal. Further, the contact surface between the gate electrode layer and the gate electrode terminal may be shifted due to the vibration of the semiconductor module.

  In view of the above circumstances, the present invention provides a technique that contributes to improvement in assembly convenience and improvement in operation reliability of a semiconductor module that electrically connects a gate electrode layer and a gate electrode terminal of a semiconductor element by pressure welding. With the goal.

  One aspect of the semiconductor module of the present invention that achieves the above object is a semiconductor module comprising a semiconductor element and a gate electrode terminal electrically connected to a gate electrode layer of the semiconductor element, wherein the gate electrode And a gate electrode post interposed between the layer and the gate electrode terminal, and an elastic member that presses the gate electrode post against the gate electrode layer.

  According to another aspect of the semiconductor module of the present invention for achieving the above object, in the semiconductor module, the gate electrode terminal is connected to the gate electrode with a pressure contact force smaller than a pressure contact force for pressing the elastic member against the gate electrode post. It is characterized by being pressed against the post.

  Another aspect of the semiconductor module of the present invention that achieves the above object is characterized in that an insulating case that presses the elastic member against the gate electrode post is provided in the semiconductor module.

  Another aspect of the semiconductor module of the present invention that achieves the above object is characterized in that in the semiconductor module, a fitting groove into which an end of the elastic member is fitted is formed in the insulating case.

  Another aspect of the semiconductor module of the present invention that achieves the above object is characterized in that in the semiconductor module, the gate electrode post is formed by layering a conductor formed in a sheet shape.

  According to the above invention, it is possible to contribute to the improvement of the assembling convenience and the operation reliability of the semiconductor module in which the gate electrode layer and the gate electrode terminal of the semiconductor element are electrically connected by pressure contact.

It is principal part sectional drawing of the semiconductor module which concerns on embodiment of this invention. It is a principal part top view of the semiconductor module which concerns on a prior art. It is principal part sectional drawing of the semiconductor module which concerns on a prior art.

  The semiconductor module of the present invention will be described in detail with reference to FIG. In the following description, the cross-sectional view shown in FIG. 1 schematically shows the semiconductor module 1 according to the embodiment of the present invention, and the dimensional ratio on the drawing and the actual dimensional ratio do not necessarily match. It is not a thing.

(Embodiment)
FIG. 1 is a cross-sectional view of a main part of a semiconductor module 1 according to an embodiment of the present invention. As shown in FIG. 1, the semiconductor module 1 according to the embodiment includes a semiconductor element 2, a gate electrode post 3, an insulating case 4, a spring 5, and a gate electrode terminal 6.

  The semiconductor element 2 is, for example, a switching element such as an IGBT or a MOSFET, and an emitter electrode layer 7 (source electrode layer) and a gate electrode layer 8 (control electrode layer) are formed on the upper surface thereof, and a collector electrode layer 9 ( A drain electrode layer) is formed. In the description of the embodiment, for convenience, the top surface and the bottom surface are used, but the vertical direction does not limit the present invention.

  An insulating sheet 10 is provided in the vicinity of the emitter electrode layer 7 and the gate electrode layer 8 of the semiconductor element 2 to ensure insulation between the electrode layers 7 and 8 and the upper peripheral electrode. An emitter (source) electrode post 11 is connected to the emitter electrode layer 7 by pressure contact, and the emitter electrode layer 7 and an emitter electrode terminal (not shown) are electrically connected via the emitter electrode post 11. A collector (drain) electrode post 12 is connected to the collector electrode layer 9 by pressure contact, and the collector electrode layer 9 and a collector electrode terminal (not shown) are electrically connected via the collector electrode post 12.

  The gate electrode post 3 is a plate-like conductor provided in contact with the insulating sheet 10 of the semiconductor element 2 and electrically connects the gate electrode layer 8 and the gate electrode terminal 6. The gate electrode post 3 is a connecting member to which the gate electrode terminal 6 is connected. The gate electrode terminal 6 is electrically connected to the gate electrode layer 8 through the gate electrode post 3. The material for forming the gate electrode post 3 is preferably a material having high conductivity and high elasticity, and heat resistance that does not deteriorate against heat generated from the semiconductor element 2 (heat resistance temperature is 250 ° C. or higher, more preferably, 300 ° C. or higher. ) Is required. Therefore, the gate electrode post 3 is made of, for example, a single metal such as aluminum (Al), copper (Cu), nickel (Ni), or molybdenum (Mo) or an alloy such as austenitic stainless steel (for example, SUS304). It is formed.

  The gate electrode post 3 has a convex portion in contact with the gate electrode layer 8. In order to ensure insulation between the gate electrode layer 8 and the upper peripheral electrode, an insulating film (not shown) having a thickness of about several micrometers is formed on the outer periphery of the gate electrode layer 8 to expose the gate electrode layer 8. The surface exists in a portion recessed from the insulating film portion. Therefore, the height of the end of the convex portion of the gate electrode post 3 is set to about several micrometers higher than the height of the insulating film portion formed on the outer peripheral portion of the gate electrode layer 8, and the gate electrode post 3 in contact with the gate electrode layer 8. By making the area of the end of the convex portion smaller than the area of the gate electrode layer 8 (an area smaller than the insulating film portion), the bondability between the gate electrode post 3 and the gate electrode layer 8 is better. It will be a thing.

  The insulating case 4 is provided on the semiconductor element 2 so as to cover the gate electrode post 3. The insulating case 4 is formed from an insulating material such as ceramic or resin. A groove 4a is formed on the surface of the insulating case 4 facing the semiconductor element 2 and in the vicinity of the portion extending in the normal direction of the electrode surface of the gate electrode layer 8, and the gate electrode post 3 is connected to the gate electrode in the groove 4a. A spring 5 is provided in pressure contact with the layer 8. The insulating case 4 is formed with an insertion hole 4b through which the gate electrode terminal 6 is inserted so that the gate electrode terminal 6 can be electrically connected to the gate electrode post 3 through the insulating case 4.

  The spring 5 is an elastic member that applies a necessary pressure contact force to a contact portion between the gate electrode post 3 and the gate electrode layer 8. The material forming the spring 5 and the shape of the spring 5 are not particularly limited, and a well-known material and shape (spring constant) are appropriately selected and used.

  The gate electrode terminal 6 is provided by pressing the gate electrode post 3 in the direction of the semiconductor element 2. By making the shape of the gate electrode terminal 6 into a shape having elasticity such as a spring, the end of the gate electrode terminal 6 is always in pressure contact with the gate electrode post 3, and the electrical connection between the gate electrode terminal 6 and the gate electrode post 3 is achieved. Secure connection. In addition, by selecting the material and shape of the gate electrode terminal 6 so that the resistance value of the gate electrode terminal 6 becomes the value of the gate resistance, the gate resistance provided in the conventional circuit becomes unnecessary, Assembling convenience of the semiconductor module 1 is improved.

  As described above, according to the semiconductor module 1 according to the embodiment of the present invention, the gate electrode terminal 6 can be easily positioned by connecting the gate electrode layer 8 and the gate electrode terminal 6 via the gate electrode post 3. Thus, even if the area of the gate electrode layer 8 is small, the reliability of the electrical connection between the gate electrode terminal 6 and the gate electrode layer 8 can be ensured. That is, by increasing the size of the gate electrode post 3, even if the tip position of the gate electrode terminal 6 is shifted on the gate electrode post 3, the gate electrode post 3 causes the gate electrode terminal 6 to be positioned between the gate electrode terminal 6 and the gate electrode layer 8. Conductivity can be ensured.

  Further, by increasing the size of the gate electrode post 3, it is possible to adjust the arrangement location of the gate electrode terminal 6. As a result, the gate electrode terminal 6 can be provided separately from conductors such as other electrode terminals through which a large current flows, so that a short circuit of the gate electrode terminal 6 can be prevented.

  Further, by providing the gate electrode post 3 on the gate electrode layer 8, the heat dissipation of the semiconductor module 1 is improved. In the semiconductor element 2 during the switching operation, the semiconductor element 2 becomes a heating element and becomes high temperature, and the junction between the gate electrode layer 8 and the gate electrode post 3 also becomes high temperature. If the portion of the gate electrode layer 8 is excessively heated, it may be difficult to control the semiconductor element 2, and particularly in the case of a normally-on device, there is a possibility that the off operation cannot be performed. When the gate electrode post 3 is provided on the gate electrode layer 8 as in the semiconductor module 1 of the present invention, the contact area between the heat generating portion (the gate electrode layer 8 and the gate electrode post 3) and the outside increases. That is, the gate electrode post 3 acts as a heat dissipation path around the gate electrode layer 8. As a result, the heat dissipation of the semiconductor module 1 is improved. If the gate electrode post 3 is formed by stacking conductive sheets in layers, the contact area between the gate electrode post 3 and the outside becomes wider, so that the heat dissipation of the semiconductor module 1 is further improved.

  In addition, when the gate electrode terminal 6 is electrically connected to the gate electrode layer 8 via the gate electrode post 3, the gate electrode terminal 6 is not in direct contact with the gate electrode terminal 6. The gate electrode layer 8 is not damaged.

  In addition, by providing the spring 5 that presses the gate electrode post 3 against the gate electrode layer 8, it is easy to design the gate electrode post 3 so that the pressure necessary to press the gate electrode post 3 against the gate electrode layer 8 is applied. Become. At this time, the pressing force with which the spring 5 presses the gate electrode post 3 is made larger than the pressing force with which the gate electrode terminal 6 presses the gate electrode post 3. Thus, by applying an appropriate contact pressure to the gate electrode post 3 and the gate electrode layer 8 by the spring 5, the pressure contact force with which the gate electrode terminal 6 presses the gate electrode post 3 is changed between the gate electrode terminal 6 and the gate electrode. What is necessary is just to press-contact with the press-contact force which can maintain the electrical contact of the electrode post 3. As a result, the selection range of the material constituting the gate electrode terminal 6 and the structure of the gate electrode terminal 6 is increased.

  In addition, the contact force between the gate electrode terminal 6 and the gate electrode post 3 should be increased by making the pressure contact force with which the spring 5 presses the gate electrode post 3 greater than the pressure contact force with which the gate electrode terminal 6 presses the gate electrode post 3. Even if they are shifted, the contact between the gate electrode layer 8 and the gate electrode post 3 is maintained by the pressure contact of the spring 5, so that the operation reliability of the semiconductor module 1 is improved. In other words, the reliable contact between the gate electrode post 3 and the gate electrode layer 8 by the pressure contact by the spring 5 is a countermeasure against the displacement of the contact position due to the vibration of the gate electrode terminal 6, and the pressure contact causes the gate electrode terminal 6 and the gate electrode layer to be contacted. The long-term reliability of the semiconductor module 1 to which 8 is connected can be improved.

  Further, by providing the insulating case 4, the contact position accuracy between the gate electrode terminal 6 and the gate electrode post 3 can be improved. That is, by processing the insulating case 4 into a shape that can fix the gate electrode terminal 6, the gate electrode post 3, and the spring 5, each member can be positioned easily and accurately. Further, since the insulating case 4 is provided, the insulation between the gate electrode layer 8, the gate electrode post 3 or the gate electrode terminal 6 and the outside (or another conductor in the vicinity of the gate electrode layer 8) is improved. 1 noise countermeasure. In particular, in the case of the semiconductor element 2 provided with the gate electrode layer 8 and the emitter (or source) electrode layer 7 close to each other, the insulation between the gate electrode layer 8 and the emitter electrode layer 7 by the insulating case 4 and the insulating sheet 10. Can be secured. Insulating sheet 10 and insulating sheet 10 can be further enhanced by forming insulating sheet 10 from an elastic material.

  In addition, when a fitting groove (spot) for fitting the spring 5 is formed in the insulating case 4 or the gate electrode post 3, the insulating case 4 and the spring 5 or the gate electrode post 3 and the spring 5 are fixed as a single body. Therefore, the positioning of the spring 5 and the fixing of the spring 5 are more reliable. Similarly, when a fitting groove (spot) for fitting the gate electrode terminal 6 is formed in the gate electrode post 3, the gate electrode post 3 and the gate electrode terminal 6 are fixed as a single unit. Positioning and fixing of the gate electrode terminal 6 become more reliable.

  Note that the semiconductor module of the present invention is not limited to the above-described embodiment, and the design can be changed as appropriate without departing from the characteristics of the present invention, and the modified form is also the semiconductor module according to the present invention. .

  For example, the present invention electrically connects a gate electrode layer (control electrode layer) of a semiconductor element and a gate electrode terminal (control electrode terminal) for connection to the outside (or another circuit inside) by pressure welding. It can be applied to a semiconductor module.

  According to the semiconductor module of the present invention, the gate electrode layer of the semiconductor element and the gate electrode terminal can be electrically connected without using a bonding agent such as solder. Therefore, the reliability of the semiconductor module such as temperature cycle and power cycle can be improved by applying it to a semiconductor module that takes advantage of the performance of a semiconductor element that can be used at high temperatures such as SiC and GaN.

  Then, by using the semiconductor module of the present invention for a power converter such as an insulated power semiconductor module or an inverter that requires high temperature operation, the operation reliability of the insulated power semiconductor module or the power converter can be improved. .

DESCRIPTION OF SYMBOLS 1 ... Semiconductor module 2 ... Semiconductor element 3 ... Gate electrode post 4 ... Insulating case 4a ... Groove 4b ... Insertion hole 5 ... Spring (elastic member)
6 ... Gate electrode terminal 7 ... Emitter electrode layer 8 ... Gate electrode layer 9 ... Collector electrode layer 10 ... Insulating sheet

Claims (5)

A semiconductor element;
A gate electrode terminal electrically connected to the gate electrode layer of the semiconductor element;
A semiconductor module comprising:
A gate electrode post interposed between the gate electrode layer and the gate electrode terminal;
A semiconductor module comprising: an elastic member that presses the gate electrode post against the gate electrode layer. 2. The semiconductor module according to claim 1, wherein the gate electrode terminal is pressed against the gate electrode post with a pressing force smaller than a pressing force for pressing the elastic member against the gate electrode post. The semiconductor module according to claim 1, further comprising an insulating case that presses the elastic member against the gate electrode post. The semiconductor module according to claim 3, wherein a fitting groove into which an end of the elastic member is fitted is formed in the insulating case. 5. The semiconductor module according to claim 1, wherein the gate electrode post is formed by layering a conductor formed in a sheet shape. 6.

Images