JP2015056412A - Power semiconductor device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of a power semiconductor device where an electrode terminal is jointed to a conductor pattern or a surface electrode of a power semiconductor element with an ultrasonic wave.SOLUTION: A power semiconductor device 100 includes an insulation board (ceramic board 5) on which a conductor pattern 52a is formed, a power semiconductor element 1 disposed on the conductor pattern 52a, and an electrode terminal 3. The electrode terminal 3 includes a body part, and a thin wall part (a tip part 3b) formed to be thinner than the body part in advance. The thin wall part (tip part 3b) includes an ultrasonic junction part 20 jointed to the conductor pattern 52a with an ultrasonic wave.

Description

  The present invention relates to a power semiconductor device, and more particularly to a power semiconductor device in which electrode terminals are joined by ultrasonic bonding to a surface electrode of a semiconductor element or a conductor pattern on which the semiconductor element is mounted.

  In a conventional power semiconductor device, particularly a high-current power semiconductor device, in order to efficiently flow a large current, it is necessary to join electrode terminals connected to an external circuit in a large area. Solder joints have been used (for example, Patent Document 1). However, as the temperature environment in which the power semiconductor device is used becomes severe, there is a possibility that the reliability required by the conventional solder joint cannot be satisfied. Further, in the conventional solder bonding, when the power semiconductor device has a structure in which a ceramic substrate having a conductor pattern formed on both sides of the ceramic plate is solder bonded to the base plate, the electrode terminal is solder bonded. Due to this heating, the solder joining the base plate and the ceramic substrate may be remelted. For this reason, the solder that joins the electrode terminals cannot use a solder whose melting point is close to that of the solder that joins the base plate and the ceramic substrate, which requires a plurality of types of solder, which complicates the process. It was.

  As a method for solving these problems, there is a method in which electrode terminals are ultrasonically bonded to a conductor pattern on a ceramic substrate. Since ultrasonic bonding is a solid phase bonding and does not require a heating process, it is possible to bond electrode terminals in a large area without remelting the solder bonding the base plate and the ceramic substrate when bonding the electrode terminals. In addition, the reliability of the joint can be improved as compared with the solder joint.

  However, in ultrasonic bonding, bonding is performed by ultrasonically vibrating a material to be bonded with an ultrasonic horn. Therefore, joining conditions for joining electrode terminals having a cross-sectional area necessary for securing a current capacity necessary for a power semiconductor device require high pressure, strong ultrasonic vibration, and a long joining time. As a result, the deformation of the terminal joint where the electrode terminal and the conductor pattern are joined is increased, and the terminal joint is locally thinned. This creates a location where stress is likely to concentrate at the boundary (thickness boundary) between the pressed portion pressed by the ultrasonic horn and the electrode terminal body other than the pressed portion, and heat generated during operation of the power semiconductor device Concentration of stress due to deformation due to expansion and vibration in this region may cause fatigue failure of the electrode terminals, leading to a decrease in reliability of the power semiconductor device. In order to avoid these, it is conceivable to set the bonding conditions for ultrasonic bonding to be weak in order to minimize deformation, but in this case, there is a problem that the bonding strength of the terminal bonding portion is lowered.

  Therefore, in order to solve this problem, Patent Document 2 includes a non-pressing portion in which the ultrasonic bonding portion at the tip of the electrode terminal is not reduced in thickness and a pressing portion in which the thickness is reduced by being pressed by an ultrasonic horn. A technique is disclosed in which the distance in the width direction between the non-pressing portion and the boundary portion of the pressing portion is larger than the width of the tip portion of the electrode terminal.

Japanese Patent Laying-Open No. 2006-253516 (stage 0012 to stage 0014, FIG. 1) JP 2012-138458 A (0006 to 0007, 0012 to 0013, FIG. 3)

  As described above, if the bonding conditions for ultrasonic bonding are set to be weak so as to minimize deformation of the indented portion pressed by the ultrasonic horn, the bonding strength of the terminal bonding portion decreases. When the joint strength of the terminal joint is reduced, the terminal joint is easily peeled off due to the stress caused by deformation caused by thermal expansion and vibration that occurs during operation. The reliability of the semiconductor device may be reduced. In a power semiconductor device, the current flowing through the semiconductor element during operation flows through the conductor pattern on the ceramic substrate from the electrode terminal through the terminal joint, so that even if the electrode terminal is fatigued or the terminal joint is peeled off There is a risk that current does not flow through the power semiconductor device, and if the current stops flowing, the controlled device may not be normally controlled by the power semiconductor device.

  In Patent Document 2, the width direction distance of the non-pressing portion where the thickness does not decrease and the boundary portion of the pressing portion where the thickness is reduced by pressure contact with an ultrasonic horn is set to be larger than the width of the tip portion of the electrode terminal. A sonic junction is formed. By extending the distance of direct contact between the non-pressing part where the thickness does not decrease and the pressing part where the thickness decreases, the stress concentrated on the corner of the hit point is dispersed, improving the pull strength and improving the durability reliability. An improvement can be obtained. Moreover, in patent document 2, since the intensity | strength of the member neck part of a front-end | tip part improves by the stress concentration inhibitory effect, it becomes possible to increase the pushing amount of an ultrasonic joining part and to make a pressing part thin, and per unit area Bonding strength can be improved. This reduces the required bonding area and contributes to the overall size reduction.

  However, the technique of Patent Document 2 described above requires high pressure, strong ultrasonic vibration, and a long bonding time as bonding conditions for bonding the electrode terminals. Therefore, the portion pressed by the ultrasonic horn of the electrode terminal (corresponding to the ultrasonic bonding tool of Patent Document 2) at the time of ultrasonic bonding is shaved and deformed and locally thinned. This not only creates a location where stress is likely to concentrate at the boundary between the push-in portion and the electrode terminal body, but also causes the substantially L-shaped bent portion at the tip of the electrode terminal to be repeatedly deformed by ultrasonic vibration during joining. There is a risk of fatigue failure and cracking. When the substantially L-shaped bent portion undergoes fatigue failure, no current flows through the power semiconductor device as described above. If a crack is generated without fatigue failure, stress due to deformation caused by thermal expansion and vibration generated during operation concentrates on this part, and there is a risk of eventually causing fatigue failure.

  The present invention has been made to solve the above-described problems, and is for power use in which electrode terminals are ultrasonically bonded to a conductor pattern on an insulating substrate such as a ceramic substrate or a surface electrode of a power semiconductor element. In a semiconductor device, even when an electrode terminal is bent in a substantially L shape or the like when ultrasonic bonding is performed, it is intended to prevent fatigue fracture or generation of cracks in the bent portion and improve reliability. .

  The power semiconductor device of the present invention includes an insulating substrate on which a conductor pattern is formed, a power semiconductor element disposed on the conductor pattern, and an electrode terminal. The electrode terminal includes a main body portion and a main body in advance. A thin-walled portion formed thinner than the portion, and the thin-walled portion includes an ultrasonic bonding portion ultrasonically bonded to an object which is a conductor pattern or a surface electrode of a power semiconductor element.

  According to the power semiconductor device of the present invention, since the electrode terminal has a thin portion that is previously formed thinner than the main body, the electrode terminal is ultrasonically applied to an object that is a surface electrode of a conductor pattern or power semiconductor element. Even when an electrode terminal is bent into a substantially L shape or the like when bonded, fatigue failure and cracking of the bent portion can be prevented and reliability can be improved.

It is a fragmentary sectional view which shows the principal part of the semiconductor device for electric power by Embodiment 1 of this invention. It is the schematic explaining the ultrasonic bonding process of a comparative example. It is the schematic explaining the ultrasonic bonding process of a comparative example. It is the schematic explaining the ultrasonic bonding process of a comparative example. It is the schematic explaining the ultrasonic joining process by Embodiment 1 of this invention. It is the schematic explaining the ultrasonic joining process by Embodiment 1 of this invention. It is the schematic explaining the ultrasonic joining process by Embodiment 1 of this invention. It is a fragmentary sectional view which shows the principal part of the semiconductor device for electric power by Embodiment 2 of this invention. It is a fragmentary sectional view which shows the principal part of the semiconductor device for electric power by Embodiment 3 of this invention. It is a fragmentary sectional view which shows the principal part of the semiconductor device for electric power by Embodiment 4 of this invention. It is a fragmentary sectional view which shows the principal part of the power semiconductor device by Embodiment 5 of this invention. It is a fragmentary sectional view which shows the principal part of the power semiconductor device by Embodiment 6 of this invention.

  The power semiconductor device of the present invention will be described below with reference to the drawings. In each figure, the same or similar components are denoted by the same reference numerals. Between each figure, the size and scale of each corresponding component are independent. For example, between the cross-sectional views in which a part of the configuration is changed, the same component that is not changed may have a different size or scale. In addition, the configuration of the power semiconductor device actually includes a plurality of members. However, in order to simplify the description, only the portions necessary for the description are described, and other portions (for example, the power semiconductor element) , Case, heat sink, etc.) are omitted.

Embodiment 1 FIG.
FIG. 1 is a partial cross-sectional view for explaining a configuration of a main part of the power semiconductor device according to the first embodiment of the present invention. As shown in FIG. 1, the power semiconductor device 100 according to the first embodiment of the present invention includes a ceramic substrate 5 having conductor patterns 52a and 52b formed on both sides of an insulating base 51, a heat dissipation member 6, and electrode terminals. 3 etc. The heat radiating member 6 is joined to the heat radiating surface side (conductor pattern 52b side) of the ceramic substrate 5 with solder 8, and the electrode terminal 3 is ultrasonically joined to the circuit surface side (conductor pattern 52a side). The electrode terminal 3 is electrically connected to the main electrode of the power semiconductor element 1. Details will be described below. Each figure shows a coordinate system, where the x direction is a direction horizontal to the ceramic substrate 5 and the joint portion of the electrode terminal 3 extends, and the z direction is a direction perpendicular to the ceramic substrate 5. , Y direction is a direction perpendicular to the page. The x direction, y direction, and z direction of the coordinate system are orthogonal to each other.

  The electrode terminal 3 is a wiring member for electrically connecting a power semiconductor element 1 (see FIG. 12) such as an IGBT (Insulated Gate Bipolar Transistor) and an external circuit. The material of the electrode terminal 3 is preferably a metal having a low electric resistance, and generally, a material obtained by cutting or pressing a sheet metal such as Cu or Al is used. One end of the electrode terminal 3 is connected to the conductor pattern 52a, and the other end is electrically connected to another circuit member or an external circuit. The electrode terminal 3 preferably has a large cross-sectional area in order to increase the current that can be energized. However, in order to easily transmit the power applied during ultrasonic bonding to the bonding surface 3j. A thinner thickness is preferred. Therefore, in the plate material constituting the electrode terminal 3 of the first embodiment, the tip portion 3b which is the terminal tip portion including the joint surface 3j is processed in advance from the surface direction opposite to the surface having the joint surface 3j ( 5) and a thin region (thin portion) that is thinner than the tip portion 3b of the electrode terminal 3 (referred to as an electrode terminal main body as appropriate). Unlike the crushing by the ultrasonic horn 50 (see FIG. 5), the tip 3b including the joining surface 3j of the electrode terminal 3 is preferably processed by pressing or cutting. In FIG. 1, an example in which the tip portion 3 b is all a thin region, that is, an example in which a thin portion is provided at the tip portion of the electrode terminal 3 is shown.

  The tip portion 3 b of the electrode terminal 3 is a portion from the broken line 15 to the broken line 17. The distal end portion 3 b includes an ultrasonic bonding portion 20 that is a portion from the broken line 15 to the broken line 16 and an unpressurized portion 3 a that is a portion from the broken line 16 to the broken line 17. The unpressurized portion 3a is an unconnected portion that is not connected to the conductor pattern 52a. The ultrasonic bonding portion 20 is a portion having at least a bonding surface 3j facing the conductor pattern 52a, and the non-pressurized portion 3a is a portion other than the ultrasonic bonding portion 20 in the distal end portion 3b. A portion on the right side from the broken line 17 is an electrode terminal body of the electrode terminal 3. The part from the broken line 17 to the broken line 18 is the terminal bending part 3r.

  The preferable dimension of the electrode terminal 3 is shown. The thickness (unpressurized part thickness t1, see FIG. 5) of the tip part (thin part) 3b is preferably about 0.3 mm to 0.8 mm. The thickness of the electrode terminal 3 is preferably about 1.0 mm to 2.0 mm, and the width of the electrode terminal 3 (electrode terminal length in the y direction) is preferably about 2.0 mm to 6.0 mm. Further, a portion (tip portion 3b) thinner than the electrode terminal main body of the electrode terminal 3 is pressurized by the ultrasonic horn 50, and an ultrasonic horn is applied to the portion pressurized by the ultrasonic horn 50 (ultrasonic bonding portion 20). Indentations are formed in such a way that 50 tip shapes are transferred. It is preferable to provide an unpressurized portion 3a that is not pressurized by the ultrasonic horn 50 between the portion (ultrasonic bonding portion 20) pressed by the ultrasonic horn 50 and the electrode terminal body of the electrode terminal 3. The unpressurized portion 3a is more preferably 0.5 mm or longer (x-direction length).

The ceramic substrate 5 includes an insulating base 51 and conductor patterns 52 a and 52 b formed on both sides of the insulating base 51. The conductor patterns 52a and 52b are patterned conductors. The insulating base 51 is an electrical insulator and is preferably made of a material having a high thermal conductivity. Generally, a ceramic plate made of AlN, SN, Al ₂ O ₃ or the like having a thickness of 0.635 mm or 0.32 mm is used. Used. The same material is used for the conductor pattern 52a and the conductor pattern 52b. Among these, the conductor pattern 52a that forms the joint portion to be joined to the electrode terminal 3 is a wiring member for electrically connecting the power semiconductor element 1 and the external circuit, and therefore, a metal having a low electrical resistance is preferable. Therefore, Cu or Al having a thickness of about 0.5 mm or less is generally used for the conductor patterns 52a and 52b.

  The heat radiating member 6 is joined to a single or a plurality of ceramic substrates 5 by solder 8 and plays a role as a heat radiating plate, and faces the surface of the heat radiating member 6 that is joined by the solder 8 (on the opposite side). The surface) is connected to a heat sink (not shown) with thermal conductive grease or the like, so that heat generated in the power semiconductor device 100 is efficiently radiated to the outside. Therefore, the material of the heat radiating member 6 is preferably a metal having a large thermal conductivity, and generally a metal plate of Cu, Al, AlSiC or the like having a thickness of about 1 to 5 mm is used.

  The solder 8 joins the heat radiating surface side of the ceramic substrate 5 and the heat radiating member 6. Therefore, the material of the solder 8 is preferably a metal having a low melting point and a high thermal conductivity, and generally an alloy using Sn, Pb, Ag, Cu or the like is used. The thickness is preferably about 0.1 mm to 0.3 mm from the viewpoint of reliability and heat dissipation.

  Next, features and effects of the power semiconductor device 100 configured as described above will be described in comparison with the conventional power semiconductor device 110 (comparative example). 2 to 4 are schematic diagrams for explaining the ultrasonic bonding process of the comparative example. 5-7 is the schematic explaining the ultrasonic joining process by Embodiment 1 of this invention. 2-7 has shown the cross section of the junction part vicinity for every ultrasonic bonding process, respectively. 2 and 5 show a state in which the ultrasonic horn 50 is in contact with the electrode terminal 3 and the electrode terminal 13. 3 and 6 show a state in which the electrode terminal 3 and the electrode terminal 13 are vibrated with ultrasonic waves while applying a pressure 30 with the ultrasonic horn 50. 4 and 7 show a state where the electrode terminal 3 and the electrode terminal 13 are joined to the conductor pattern 52a of the ceramic substrate 5. FIG.

  The manufacturing method of the power semiconductor device 100 of the first embodiment includes four steps, that is, a thin portion forming step of forming a thin portion thinner than the electrode terminal main body at the tip portion of the electrode terminal 3, and an ultrasonic treatment of the ceramic substrate 5. A substrate fixing step for fixing to the bonding apparatus, an electrode terminal placing step for placing the electrode terminal 3 on the conductor pattern 52a of the ceramic substrate 5, and an ultrasonic bonding step for ultrasonically bonding the conductor pattern 52a and the electrode terminal 3 to each other. Contains. A thin part formation process is a process of processing the area | region including the joining area | region connected to the target object which is the conductor pattern 52a in the electrode terminal 3 thinner than a main-body part (electrode terminal main body). In FIG. 1 and FIG. 5 to FIG. 7, the tip portion 3 b (the ultrasonic bonding portion 20, the unpressurized portion 3 a) including the surface that directly contacts the conductor pattern 52 a of the ceramic substrate 5 is a thin portion. In the ultrasonic bonding process, the ultrasonic horn 50 of the ultrasonic bonding apparatus is applied from the opposite side (surface) of the electrode terminal 3 to the ceramic substrate 5 to ultrasonically bond the conductor pattern 52a and the electrode terminal 3. It is a process. In the method for manufacturing the power semiconductor device 110 of the comparative example, the thin portion forming step is deleted from the method for manufacturing the power semiconductor device 100 of the first embodiment, and the bonding conditions of the electrode terminals 13 are different.

  FIG. 5 shows a state in which the thin portion forming process, the substrate fixing process, and the electrode terminal placing process of the first embodiment are performed. FIG. 6 shows a state in which the ultrasonic bonding process of the first embodiment is being performed. FIG. 7 shows the power semiconductor device 100 after the ultrasonic bonding process of the first embodiment is completed. FIG. 2 shows a state in which the substrate fixing process and the electrode terminal placing process of the comparative example are executed. FIG. 3 shows a state in which the ultrasonic bonding process of the comparative example is being executed. FIG. 4 shows the power semiconductor device 110 after the ultrasonic bonding process of the comparative example is completed.

  In the conventional power semiconductor device 110, the thicknesses of the electrode terminals 13 are all constant. A portion from the broken line 15 (see FIG. 4) to the broken line 19 is the tip portion 13 b of the electrode terminal 13. A portion on the right side from the broken line 19 is an electrode terminal body of the electrode terminal 13. A portion from a broken line 19 to a broken line 18 is a terminal bent portion 13r. Since it is necessary to pass a current necessary for operating the power semiconductor device 110 to the electrode terminal 3, the electrode terminal 13 of the power semiconductor device 110 used for a product that handles a large current such as power generation or railway A Cu terminal having a thickness of 1.0 mm or more is generally used. When ultrasonic bonding is performed, the thicker the plate and the harder the material, the more energy required for bonding. Therefore, it is necessary to increase bonding conditions such as load, bonding time, and amplitude. However, when the joining condition is increased, as shown in FIGS. 2 to 4, the electrode terminal 13 itself is greatly deformed by the ultrasonic horn 50, or the terminal bent portion 13r is repeatedly deformed for a long time, so that the terminal bent portion 13r is deformed. May cause cracks.

  In contrast, as described above, in power semiconductor device 100 according to the first embodiment of the present invention, tip portion 3b of electrode terminal 3 is processed in advance from the surface direction opposite to the surface having bonding surface 3j. It is thinner than the electrode terminal body of the electrode terminal 3. As described above, by preliminarily thinning the portion to be pressed by the ultrasonic horn 50, the energy required for ultrasonic bonding can be reduced. If the energy required for ultrasonic bonding is reduced, the load (pressing force) and amplitude, which are bonding conditions, can be reduced and the bonding time can be shortened. Therefore, the power semiconductor device 100 of the first embodiment is shown in FIG. As shown in FIG. 7, the ultrasonic horn 50 can prevent the electrode terminal 3 itself from being greatly deformed. In addition, since the power semiconductor device 100 according to the first embodiment can shorten the time during which repeated deformation is applied to the substantially L-shaped terminal bending portion 3r by shortening the bonding time, the terminal bending portion 3r. It is possible to prevent cracks from occurring.

  Furthermore, the metal scraped off from the portion greatly deformed by the ultrasonic horn 50 of the electrode terminal 13 of the comparative example is scattered as metal scrap 13c (see FIG. 3). If these metal scraps 13c fall between the surface of the power semiconductor element 1 or between the conductor patterns 52a, the power semiconductor device 110 may cause malfunction or dielectric breakdown.

  On the other hand, in the power semiconductor device 100 according to the first embodiment of the present invention, it is possible to prevent the electrode terminal 3 from being greatly deformed by the ultrasonic horn 50 by setting the bonding condition weaker than before. Therefore, the amount that the electrode terminal 3 can be scraped is extremely small compared to the conventional case, and the generation of metal scrap 13c that is a large lump of scraped metal can be suppressed.

  Furthermore, stress is also generated in the electrode terminals 3 and 13 due to deformation caused by thermal expansion and vibration generated during operation of the power semiconductor devices 100 and 110. At this time, in the conventional power semiconductor device 110, as shown in FIG. 4, the electrode terminal 13 and the conductor pattern 52 a are joined at the portion pressed by the ultrasonic horn 50. Therefore, the projection as seen from the z direction of the portion (the portion from the broken line 15 to the broken line 16) where the electrode terminal 13 is crushed from the unpressurized portion thickness t5 of the tip end portion 13b by the ultrasonic horn 50 and thinned. The area becomes the ultrasonic bonding portion 25 as it is. The boundary between the portion where the thickness of the electrode terminal 13 is reduced and the portion where the thickness of the electrode terminal 13 remains before ultrasonic bonding is the portion indicated by the broken line 16. Further, the boundary between the ultrasonic bonding portion 25 at the distal end portion 13 b of the electrode terminal 13 and the non-bonded portion 26 that is not pressed by the ultrasonic horn 50 and is not bonded to the conductor pattern 52 a is a portion indicated by a broken line 16. . Therefore, the boundary between the parts having different thicknesses of the electrode terminal 13 and the boundary between the ultrasonic bonding portion 25 and the non-bonding portion 26 in the electrode terminal 13 are coincident with each other, that is, the above two boundaries are on the z axis in FIG. Exists on the same line. A portion surrounded by a broken-line circle 27 is a boundary portion between the ultrasonic bonding portion 25 and the non-bonding portion 26 in the electrode terminal 13 and is a boundary portion that is a portion where the thickness of the electrode terminal 13 changes.

  The boundary portion 27, which is a portion where the thickness of the electrode terminal 13 of the comparative example changes, is reduced in the thickness of the member of the electrode terminal 13 and is damaged by the vibration of the ultrasonic horn 50 during bonding. It is easy to break because it receives. Further, since the boundary portion between the ultrasonic bonded portion 25 and the non-bonded portion 26 also coincides with the boundary portion 27, the stress generated in the electrode terminal 13 is the largest in this portion. Therefore, the stress generated in the electrode terminal 13 due to deformation caused by thermal expansion and vibration generated during the operation of the power semiconductor device 110 of the comparative example is concentrated on the boundary portion 27 where the thickness of the electrode terminal 13 changes. As a result, the electrode terminal 13 may be broken and the reliability of the power semiconductor device 110 may be reduced.

  On the other hand, in the power semiconductor device 100 according to the first embodiment of the present invention, the electrode terminal 3 is not greatly deformed by the ultrasonic horn 50 and is pressed by the ultrasonic horn 50 as shown in FIG. The tip is thinned by providing an unpressurized portion 3a that is not pressurized by the ultrasonic horn 50 between the portion to be bent (ultrasonic bonding portion 20) and the terminal bending portion 3r having a different thickness of the electrode terminal 3 The mechanical influence at the time of ultrasonic bonding with respect to the boundary portion 21 between the portion 3b and the terminal bent portion 3r can be reduced, and the boundary portion 21 can be prevented from being excessively damaged. Moreover, even if the position of the ultrasonic horn 50 or the electrode terminal 3 shifts by providing the non-pressurized portion 3a so that the length is about 0.5 mm or more, the ultrasonic bonded portion 20 and the terminal bent portion 3r. Since the non-pressurized portion 3a exists without disappearing, damage to the boundary portion 21 can be prevented without being affected by the mechanical effect at the time of joining. Further, even if stress is generated in the electrode terminal 3 due to thermal deformation and thermal deformation that occur during the operation of the power semiconductor device 100, the stress is not changed because the entire unpressurized portion 3 a of the electrode terminal 3 is deformed. Dispersed throughout the pressure unit 3a. Therefore, stress does not concentrate on the thickness boundary part (part where the broken line 17 passes), the boundary part 21 and the ultrasonic bonding part 20 with different thicknesses of the electrode terminal 3, and the electrode terminal 3 breaks at that part. In addition, the product reliability can be prevented from being lowered.

  In the ultrasonic bonding part 20, the current flows to the other end side of the electrode terminal 3 through the ultrasonic bonding part 20, and the ultrasonic bonding part 20 is structurally powered with respect to the thickness direction of the ultrasonic bonding part 20. This is a heat dissipation path of the semiconductor device 100 for use. Therefore, even if the tip portion 3b of the electrode terminal 3 is thinned, the current concentration portion can be eliminated or minimized, and the current that can be energized can be maintained without causing abnormal heat generation due to the current concentration. it can. Depending on the magnitude of the current, heat generation due to energization can be further reduced by making part or all of the tip 3b wider in the y direction than other parts of the electrode terminal 3.

  If the tip portion 3b of the electrode terminal 3 is thinned, ultrasonic bonding can be applied even to thermal stress generated in the ultrasonic bonding portion 20 due to a difference in linear expansion coefficient between members due to a temperature change accompanying the operation of the power semiconductor device 100. Since the portion 20 is less likely to break, a highly reliable power semiconductor device 100 can be obtained.

  In power semiconductor device 100 of the first embodiment, tip portion 3b of electrode terminal 3 including bonding surface 3j is processed in advance from the surface direction opposite to the surface having bonding surface 3j, and is thinner than the other portions. Since the electrode terminal 3 is provided, the energy required to ultrasonically bond the electrode terminal 3 to the conductor pattern 52a can be reduced while maintaining a current amount that can be energized. Since the power semiconductor device 100 according to the first embodiment requires less energy for ultrasonic bonding, the ultrasonic horn 50 can prevent the electrode terminal 3 from being greatly deformed. Furthermore, the power semiconductor device 100 according to the first embodiment can shorten the time during which the terminal bending portion 3r is repeatedly deformed by shortening the joining time, and thus prevents the terminal bending portion 3r from cracking. be able to. In addition, the power semiconductor device 100 of the first embodiment can prevent the electrode terminal 3 from being greatly deformed, and at the same time, can suppress the generation of the metal scrap 13c, and the metal scrap 13c is on the power semiconductor element 1. It is also possible to suppress scattering on the conductor pattern 52a.

  Furthermore, in the power semiconductor device 100 of the first embodiment, the portion (ultrasonic bonding portion 20) pressed by the ultrasonic horn 50 and the thickness boundary portion where the thickness of the electrode terminal 3 is different are opened. In other words, by providing the unpressurized portion 3a thinner than the main body portion of the electrode terminal 3 between the ultrasonic bonding portion 20 and the terminal bending portion 3r, the ultrasonic horn 50 is provided at the time of ultrasonic bonding. It is possible to prevent the electrode terminal 3 from being damaged by the mechanical effect given by the above. In the power semiconductor device 100 of the first embodiment, the stress generated in the electrode terminal 3 due to deformation caused by thermal expansion and vibration generated during the operation of the power semiconductor device 100 is dispersed throughout the unpressurized portion 3a. Unlike the case where the electrode terminal 3 is broken by concentrating on the boundary portion 27 and the reliability of the product is lowered, the reliability can be increased with the high ultrasonic junction 20 and the reliability. Can be improved.

  The power semiconductor element 1 may be a general element based on a silicon wafer. However, in the present invention, the band gap is larger than that of silicon carbide (SiC), gallium nitride (GaN) -based material, or silicon such as diamond. A wide so-called wide band gap semiconductor material can be applied. The device type of the power semiconductor element 1 is not particularly limited, but a switching element such as an IGBT or MOSFET (Metal Oxide Semiconductor Field-Effect-Transistor) or a rectifying element such as a diode may be mounted. it can. For example, when silicon carbide (SiC), gallium nitride (GaN) -based material, or diamond is used for the power semiconductor element 1 that functions as a switching element or a rectifying element, it is formed of silicon (Si) that has been used conventionally. Since the power loss is lower than that of the element, the efficiency of the power semiconductor device 100 can be increased. In addition, since the withstand voltage is high and the allowable current density is also high, the power semiconductor device 100 can be downsized. Furthermore, the wide band gap semiconductor element has high heat resistance, so it can be operated at high temperature, and the radiating fin (heat sink) can be downsized and the water cooling part can be cooled by air. The power semiconductor device 100 can be further reduced in size.

  As described above, according to the power semiconductor device 100 of the first embodiment, the insulating substrate (ceramic substrate 5) on which the conductor pattern 52a is formed, and the power semiconductor element 1 disposed on the conductor pattern 52a. And the electrode terminal 3, the electrode terminal 3 having a main body portion and a thin portion (tip portion 3 b) formed in advance thinner than the main body portion, and the thin portion (tip portion 3 b) is a conductor pattern. Since the ultrasonic bonding portion 20 is ultrasonically bonded to the 52a, even when the electrode terminal is bent in a substantially L shape or the like when the ultrasonic bonding is performed, Generation of cracks can be prevented and reliability can be improved.

  According to the manufacturing method of the power semiconductor device of the first embodiment, the region including the bonding region connected to the object that is the conductor pattern 52a or the surface electrode 2 of the power semiconductor element 1 in the electrode terminal 3 The thin-walled portion forming step for forming the thin-walled portion, the substrate fixing step for fixing the insulating substrate (ceramic substrate 5) on which the power semiconductor element 1 is mounted to the ultrasonic bonding apparatus, and the object In the electrode terminal placing process for placing the electrode terminal 3 and the thin portion of the electrode terminal 3, the ultrasonic horn 50 of the ultrasonic bonding apparatus is placed on the surface facing the surface on which the electrode terminal 3 is placed on the object. And an ultrasonic bonding step of ultrasonically bonding the object and the electrode terminal 3, so that even if the electrode terminal is bent into a substantially L shape or the like when ultrasonically bonding, , Fatigue fracture and To prevent the occurrence, it is possible to improve the reliability.

Embodiment 2. FIG.
FIG. 8 is a partial cross-sectional view showing a main part of the power semiconductor device according to the second embodiment of the present invention. The power semiconductor device 100 according to the second embodiment is different from the first embodiment in that the shape of the unpressurized portion 3a of the electrode terminal 3 on the opposite side of the mounting surface facing the ceramic substrate 5 is rounded. It is. In the first embodiment, there is a step at the thickness boundary portion (the portion through which the broken line 17 passes) where the thickness of the electrode terminal 3 in FIG. 7 is different, but in the second embodiment, the step is not added to the thickness boundary portion. The connection with the pressure part 3a is smooth. If the non-pressurized portion 3a of the electrode terminal 3 is rounded, at the corner of the thickness boundary portion (the portion through which the broken line 17 passes) in FIG. Unlike repeated deformation, mechanical damage at the thickness boundary portion (portion through which the broken line 17 passes) can be reduced, and the effect of preventing the occurrence of cracks can be enhanced compared to the first embodiment. Can do.

  In addition, the same effect is acquired even if the shape on the opposite side to the mounting surface which opposes the ceramic substrate 5 in the unpressurized part 3a of the electrode terminal 3 is made into a C chamfering shape other than a rounded corner shape.

Embodiment 3 FIG.
FIG. 9 is a partial cross-sectional view showing a main part of the power semiconductor device according to the third embodiment of the present invention. In the power semiconductor device 100 of the third embodiment, the shape of the non-pressurized portion 3a of the electrode terminal 3 is a rounded corner shape as in the second embodiment, and is on the side opposite to the surface facing the ceramic substrate 5. The bent portion inner side 3c of the terminal bent portion 3r of the electrode terminal 3 is also rounded. If the shape of the unpressurized portion 3a of the electrode terminal 3 and the shape of the bent portion inside 3c of the terminal bent portion 3r of the electrode terminal 3 are rounded, the thickness boundary portion (the broken line 17 passes through the second embodiment). And the effect of preventing the occurrence of cracks can be enhanced as compared with the second embodiment.

  In addition, the same effect is acquired even if the shape of the bending part inner side 3c in the terminal bending part 3r of the electrode terminal 3 is made into a C chamfering shape other than a rounded corner shape.

Embodiment 4 FIG.
FIG. 10 is a partial cross-sectional view showing a main part of the power semiconductor device according to the fourth embodiment of the present invention. The power semiconductor device 100 of the fourth embodiment has a substantially S-shaped bend structure portion 3 d in the main body portion of the electrode terminal 3. If the electrode terminal 3 is provided with the substantially S-shaped bend structure portion 3d, the bend structure portion 3d is preferentially deformed, so that the terminal bending portion 3r of the electrode terminal 3 is not repeatedly deformed during ultrasonic bonding. In addition, the thickness of the electrode terminal 3 is different from that repeatedly deformed at the corner of the thickness boundary portion (the portion through which the broken line 17 passes) due to vibration applied during ultrasonic bonding. Mechanical damage at the boundary (portion through which the broken line 17 passes) can be reduced, and the effect of preventing the occurrence of cracks can be enhanced compared to the first embodiment.

  Further, when stress is generated in the electrode terminal 3 due to deformation caused by thermal expansion and vibration generated during operation of the power semiconductor device 100, the bend structure portion 3d is preferentially deformed. Unlike the conventional case where the electrode terminal 3 is concentrated at one place, the thickness boundary part where the electrode terminal 3 is different (the part where the broken line 17 passes) and the boundary part 21 can be improved in fracture resistance, and the reliability of the product is implemented. This can be increased compared to the first embodiment. The electrode terminal 3 may have a terminal shape having a concave bend structure portion or the like in the main body portion. In this case, the same effect as described above can be obtained.

Embodiment 5 FIG.
FIG. 11 is a partial cross-sectional view showing a main part of the power semiconductor device according to the fifth embodiment of the present invention. The power semiconductor device 100 according to the fifth embodiment is configured such that the electrode terminal 3 is formed by overlapping a plurality of electrode terminal members 11 and 12, and the electrode terminal member 11 and the electrode terminal member 12 are not fixed to each other. It is what has. A region where the electrode terminal member 11 and the electrode terminal member 12 are not fixed to each other is a region where the gap 14 in FIG. 11 is formed. In FIG. 11, the example of the electrode terminal 3 provided with the two electrode terminal members 11 and 12 was shown. In FIG. 11, the terminal bent portion 3 r that is a portion from the broken line 17 to the broken line 18 includes a terminal bent portion 11 r of the electrode terminal member 11 and a terminal bent portion 12 r of the electrode terminal member 12.

  In the power semiconductor device 100 of the fifth embodiment, the electrode terminal 3 is configured by stacking a plurality of electrode terminal members 11 and 12, thereby forming the electrode terminal 3 while maintaining a current amount that can be energized. Since the thickness of each of the terminal members 11 and 12 can be reduced, the electrode terminal 3 has flexibility, and the electrode terminal 3 is deformed by thermal expansion and vibration generated during operation of the power semiconductor device 100. Even when stress is generated, the electrode terminal members 11 and 12 of the electrode terminal 3 are individually deformed, so that the thickness of the electrode terminal 3 is different from the conventional thickness in which the stress is concentrated on one place of the electrode terminal 3. The fracture resistance can be improved at the boundary portion (portion through which the broken line 17 passes) and at the boundary portion 21, and the reliability of the product can be increased as compared with the first embodiment.

  In addition, since the front-end | tip part 3b of the electrode terminal 3 which piled up several electrode terminal members 11 and 12 can be joined at once by ultrasonic joining, the frequency | count that a deformation | transformation is repeatedly added to the electrode terminal 3 by the joining frequency | count increasing. Will not increase.

Embodiment 6 FIG.
A power semiconductor device 100 according to the sixth embodiment will be described with reference to FIG. FIG. 12 is a partial cross-sectional view showing a main part of the power semiconductor device according to the sixth embodiment of the present invention. The difference from Embodiment 1 in FIG. 1 is that the objects to which the electrode terminals 3 are joined are different. That is, the difference from FIG. 1 of Embodiment 1 is that the electrode terminal 3 is formed on the surface of the power semiconductor element 1, unlike the electrode terminal 3 bonded to the conductor pattern 52 a of the ceramic substrate 5. That is, it is bonded to the electrode 2. In the power semiconductor element 1, a back electrode 9 is formed on a surface facing the surface on which the front surface electrode 2 is formed, and the back electrode 9 is joined to the conductor pattern 52 a of the ceramic substrate 5 with solder. .

  The electrode terminal 3 is ultrasonically bonded to the surface electrode 2 formed on the surface of the power semiconductor element 1. A transistor region 10 is formed under the surface electrode 2.

  The power semiconductor element 1 is a power semiconductor element that constitutes an inverter, a converter, or the like. The power semiconductor device 100 according to the sixth embodiment may have at least one power semiconductor element 1, but is preferably configured so that the IGBT or MOSFET is connected in antiparallel with the diode. Si, SiC, GaN, or the like is used as the material of the power semiconductor element 1, but SiC has a smaller area than the surface electrode 2 with respect to the rated current of the chip as compared with Si, so that it is higher than that of Si. High density wiring technology is required. Therefore, in the power semiconductor device 100 using SiC, the merit of the present invention becomes more effective as will be described later by ultrasonically bonding the electrode terminal 3 to the surface electrode 2. When the power semiconductor element 1 of the sixth embodiment is made of Si, the rated voltage and the rated current are, for example, 1400 V and 175 A. The size and thickness of the power semiconductor element 1 are, for example, 15 mm × 15 mm in size and 0.15 mm in thickness.

  The surface electrode 2 is a metal film for electrode wiring formed on the surface of the power semiconductor element 1. Al is generally used as the material of the surface electrode 2, but an Al alloy, Cu, Cu alloy, or the like may be used. In some cases, metals such as Ti, Mo, Ni, and Au may be laminated, but in any case, the same effect can be obtained. The material of the surface electrode 2 of the sixth embodiment is, for example, Al having a thickness of 0.07 mm.

  Next, with respect to the characteristics and effects of the power semiconductor device 100 configured as described above, the conventional case where electrode terminals having a constant thickness are used and the bonding surface 3j according to the sixth embodiment of the present invention are included. A case will be described in which the tip portion 3b is processed in advance from the surface direction opposite to the surface having the joint surface 3j and the electrode terminal 3 is thinner than the other portion (main body portion).

  As described in the first embodiment, it is necessary to pass a current necessary for operating the power semiconductor device 100 to the electrode terminal 3, and this is because the electrode terminal 3 is placed on the surface electrode 2 of the power semiconductor element 1. The same applies to ultrasonic bonding. In ultrasonic bonding, the thicker the plate and the harder the material, the more energy required for bonding. Therefore, it is also necessary to increase the bonding conditions such as load, bonding time, and amplitude.

  Here, in the case where the conventional electrode terminal 13 in which the conventional thicknesses are all constant is used, the actual thickness of the surface electrode 2 is obtained under the bonding conditions necessary to obtain a sufficient bonding area during ultrasonic bonding. Is too thin, the surface electrode 2 is deformed together with the electrode terminal 3 by pressurization and ultrasonic vibration by the ultrasonic horn 50, and a part of the surface electrode 2 is destroyed, and the transistor region 10 formed thereunder The transistor is destroyed. When the surface electrode 2 is further deformed, the electrode terminal 3 comes into contact with the power semiconductor element 1 and the power semiconductor element 1 is destroyed.

  On the other hand, in the power semiconductor device 100 of the sixth embodiment, as described in the first embodiment, the tip portion 3b of the electrode terminal 3 is thinner than the other portion (main body portion). As described in the first embodiment, when the tip portion 3b of the electrode terminal 3 is thin, the energy required for ultrasonic bonding is reduced, so that the electrode terminal 3 and the surface electrode 2 are pressed by the ultrasonic horn 50. And deformation due to ultrasonic vibration can be suppressed, and the transistor in the transistor region 10 formed thereunder, that is, the power semiconductor element 1 can be prevented from being destroyed.

  Thus, in the power semiconductor device 100 of the sixth embodiment, the tip 3b of the electrode terminal 3 including the bonding surface 3j is processed in advance from the surface direction opposite to the surface having the bonding surface 3j, and other parts By providing the electrode terminal 3 that is thinner, the electrode terminal 3 is ultrasonically bonded to the surface electrode 2 formed on the surface of the power semiconductor element 1 without destroying the power semiconductor element 1. Can do. That is, the power semiconductor device 100 of the sixth embodiment has the effects of the first embodiment, suppresses the surface electrode 2 from being deformed by the pressurization and ultrasonic vibration by the ultrasonic horn 50, and below it. It is possible to prevent the transistor in the formed transistor region 10, that is, the power semiconductor element 1 from being destroyed.

  In the case of a power semiconductor device in which the surface electrode 2 and the conductor pattern 52a of the ceramic substrate 5 are connected by a wire or the like and the electrode terminal 3 is ultrasonically bonded to the conductor pattern 52a, the surface electrode 2 and the conductor pattern 52a As the cross-sectional area of the wire or the like connecting the wires decreases, the wire or the like increases the electrical resistance from the power semiconductor element 1 to the external circuit. In contrast, in the power semiconductor device 100 of the sixth embodiment, when the electrode terminal 3 is ultrasonically bonded to the surface electrode 2, the surface electrode 2 and the conductor pattern 52 a of the ceramic substrate 5 are connected by a wire or the like. As compared with the above, the surface electrode 2 and the electrode terminal 3 can be joined in a large area at a time. Since power semiconductor device 100 of the sixth embodiment can join surface electrode 2 and electrode terminal 3 at a large area at a time, the electrical resistance from power semiconductor element 1 to the external circuit can be reduced. it can. This effect is advantageous for the power semiconductor device 100 equipped with the power semiconductor element 1 made of a wide band gap semiconductor material capable of flowing a large current. That is, the power loss of the power semiconductor device 100 can be further reduced, and further high efficiency can be achieved.

  In Embodiments 1 to 6, the example in which the tip 3b is a thin part has been described, but the left side of the ultrasonic bonding part 20 (the most distal side of the electrode terminal 3) is thicker than the thin part. There may be a thick region. Further, the thin portion may be in an intermediate portion that is not the tip portion of the electrode terminal 3. Even when the thin portion is provided in the intermediate portion, the ultrasonic bonding portion 20 is formed in the thin portion. Further, the present invention can be combined with each other within the scope of the present invention, and each embodiment can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 ... Power semiconductor element, 2 ... Surface electrode, 3 ... Electrode terminal, 3a ... Unpressurized part (unconnected part), 3b ... Tip part (thin part), 3d ... Bend structure part, 3j ... Joining surface, 3r DESCRIPTION OF SYMBOLS ... Terminal bending part, 5 ... Ceramic substrate, 11 ... Electrode terminal member, 12 ... Electrode terminal member, 20 ... Ultrasonic bonding part, 50 ... Ultrasonic horn, 52a ... Conductor pattern, 100 ... Power semiconductor device.

Claims (10)

A power semiconductor device comprising: an insulating substrate on which a conductor pattern is formed; a power semiconductor element disposed on the conductor pattern; and an electrode terminal,
The electrode terminal has a main body part and a thin part formed in advance thinner than the main body part,
The thin-walled portion includes an ultrasonic bonding portion that is ultrasonically bonded to the conductor pattern. A power semiconductor device comprising: an insulating substrate on which a conductor pattern is formed; a power semiconductor element disposed on the conductor pattern; and an electrode terminal,
The electrode terminal has a main body part and a thin part formed in advance thinner than the main body part,
The thin-walled portion has an ultrasonic bonding portion ultrasonically bonded to a surface electrode formed on the front surface side of the main electrode of the power semiconductor element.   3. The power terminal according to claim 1, wherein the electrode terminal has an unconnected portion that is not connected to the conductor pattern between the ultrasonic bonding portion and the main body portion in the thin portion. Semiconductor device. The electrode terminal is
The main body portion extends in a direction away from the surface of the insulating substrate through a terminal bent portion bent from the thin portion,
4. The electric power according to claim 1, wherein a shape opposite to the insulating substrate at a boundary portion between the main body portion and the thin portion is a rounded shape or a chamfered shape. Semiconductor device.   5. The power semiconductor device according to claim 4, wherein the electrode terminal has a rounded shape or a chamfered shape on a side opposite to the insulating substrate in the terminal bending portion.   6. The power semiconductor device according to claim 1, wherein the electrode terminal has a substantially S-shaped bend portion on a side to which an external circuit is connected in the main body portion. 7. .   The power semiconductor device according to any one of claims 1 to 6, wherein the electrode terminal is configured by stacking a plurality of electrode terminal members in a direction perpendicular to the insulating substrate.   The power semiconductor device according to claim 1, wherein the power semiconductor element is formed of a wide band gap semiconductor material.   9. The power semiconductor device according to claim 8, wherein the wide band gap semiconductor material is any one of silicon carbide, a gallium nitride-based material, and diamond. A power semiconductor device manufacturing method for manufacturing the power semiconductor device according to any one of claims 1 to 9,
Forming the thin portion by forming the thin portion in the electrode terminal by making a region including a joining region connected to an object which is a surface electrode of the conductor pattern or the power semiconductor element, than the main body portion. Process,
A substrate fixing step of fixing the insulating substrate on which the power semiconductor element is mounted to an ultrasonic bonding apparatus;
An electrode terminal placing step of placing the electrode terminal on the object;
In the thin portion of the electrode terminal, an ultrasonic horn of the ultrasonic bonding apparatus is applied from the surface side facing the surface where the electrode terminal is placed on the object, and the object and the electrode terminal are And a method of manufacturing a power semiconductor device, comprising: an ultrasonic bonding step for ultrasonic bonding.

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