JP2009076592A - Method of crimping electrode of semiconductor device and heat slinger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method capable of uniformly crimping one electrode of a semiconductor device and a heat slinger, while being able to prevent the semiconductor device from being damaged without using any spacer and any hole, when a plurality of the semiconductor devices are pinched by an upper electrode and a lower electrode and one electrode of the upper electrode and the lower electrode is crimped to the heat slinger. <P>SOLUTION: In a method of crimping one electrode of semiconductor devices 25, 26 and a heat slinger 21 wherein a plurality of the semiconductor devices 25, 26 are pinched by an upper electrode 27 and a lower electrode 23 and one electrode of the upper electrode 27 and the lower electrode 23 is crimped to the heat slinger 21, an auxiliary crimping jig 51 is inserted between the plurality of semiconductor devices 25, 26, and there is equipped a crimping jig 52 engaged with peripheries of one electrode and the auxiliary crimping jig 51 while forming and surrounding gaps between the plurality of semiconductor devices 25, 26 and the other electrode, and one electrode is crimped to the heat slinger 21 by pushing the crimping jig 52. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for crimping a semiconductor element electrode and a radiator plate, wherein a plurality of semiconductor elements are sandwiched between an upper electrode and a lower electrode, and one of the upper electrode and the lower electrode is crimped to a radiator plate.

  2. Description of the Related Art Conventionally, a semiconductor device has been disclosed in which a heat sink is disposed above and below a power semiconductor element such as an IGBT to improve heat dissipation, and a spacer is provided between the upper and lower heat sinks to prevent damage to the semiconductor element due to mold clamping. Is known (for example, Patent Document 1).

FIG. 5 is a cross-sectional view showing an example of the configuration of a conventional semiconductor device. In the semiconductor device 1, a plurality of spacers 9 such as a columnar shape are provided between the lower heat radiating plate 5 and the upper heat radiating plate 8 arranged in parallel at positions where they do not interfere with each of the semiconductor elements 2 and 3. Provided. When these spacers 9 are resin-molded with the semiconductor elements 2 and 3 sandwiched between the lower and upper radiator plates 5 and 8, the mold clamping force (compression force) of the mold die is applied to the semiconductor elements. It functions as a pressure receiving portion (resistor portion) that can be received instead of 2 and 3, whereby a sufficient clamping force can be applied while preventing damage to the semiconductor elements 2 and 3. In FIG. 5, 6 and 7 are electrode blocks, and 4 is solder.
JP 2004-303900 A

  However, in the above conventional semiconductor device, a plurality of spacers 9 are inserted into the gaps between the upper and lower heat sinks 5 and 8, and the holes (recesses) 10 for fitting and positioning the spacers 9 on the upper and lower heat sinks 5 and 8. , 11 need to be installed. For this reason, a plurality of spacers 9 that cannot be reused and the drilling of the upper and lower heat sinks 5 and 8 are required. Therefore, when the above-described conventional method for manufacturing a semiconductor device is applied to the method for crimping the electrode of the semiconductor element and the heat sink of the present invention, a plurality of non-reusable spacers and the drilling of the upper and lower electrodes And the work becomes complicated and the cost increases.

  The present invention has been made in view of the above points. When a plurality of semiconductor elements are sandwiched between an upper electrode and a lower electrode, and one of the upper electrode and the lower electrode is pressure-bonded to a heat radiating plate. An object of the present invention is to provide a crimping method that can prevent damage to a semiconductor element without using a spacer or a hole, and that can uniformly crimp one electrode of the semiconductor element and a heat sink.

In order to achieve the above object, the present invention provides an electrode of a semiconductor element in which a plurality of semiconductor elements are sandwiched between an upper electrode and a lower electrode, and one of the upper electrode and the lower electrode is crimped to a heat sink. In the method of crimping the heat sink and
An auxiliary crimping jig is inserted between the plurality of semiconductor elements to form a gap with the plurality of semiconductor elements and the other electrode, and a crimping jig is engaged with the peripheral edge of the one electrode and the auxiliary crimping jig. Attach and press the crimping jig to crimp the one electrode to the heat sink.

  According to the present invention, a plurality of semiconductor elements and a plurality of semiconductor elements and the other electrode are surrounded by forming a gap and pressing a crimping jig engaging with a peripheral edge of one electrode and an auxiliary crimping jig. Without pressing the other electrode, it is possible to press the periphery of one electrode and between a plurality of semiconductor elements. Accordingly, damage to the semiconductor element can be prevented without using a spacer or a hole, and one electrode of the semiconductor element and the heat radiating plate can be uniformly bonded. The auxiliary crimping jig and the crimping jig can be reused.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating an example of a basic configuration of a semiconductor device.

  As shown in FIG. 1, the basic configuration of this semiconductor device includes an insulating sheet 22, a lower electrode 23, a first solder layer 24 a, a first semiconductor element 25 (second semiconductor element 26), and a second on a heat sink 21. The solder layer 24b and the upper electrode 27 are laminated. In other words, the first semiconductor element 25 and the second semiconductor element 26 (hereinafter referred to as semiconductor elements 25 and 26) are disposed below the first solder layer 24a and the second solder layer 24b (hereinafter referred to as solder layers 24a and 24b). It is sandwiched between the electrode 23 and the upper electrode 27.

  The first semiconductor element 25 is a power semiconductor element such as an IGBT or a power MOSFET, for example. In the case of an IGBT, the first semiconductor element 25 includes a collector electrode (not shown) on the lower surface, and an emitter electrode (not shown) and a gate electrode (not shown) on the upper surface.

  The emitter electrode and the gate electrode are formed by laminating Al in regions isolated from each other on the upper surface of the IGBT 25. The emitter electrode is electrically connected to the upper electrode 27 via the second solder layer 24b, and the gate electrode is electrically connected to the external electrode (not shown) via a bonding wire (not shown). Has been.

  The collector electrode is formed by laminating Al on the entire lower surface of the IGBT 25, and is electrically connected to the lower electrode 23 via the first solder layer 24a.

  The IGBT 25 can control ON / OFF of the current flowing from the collector electrode to the emitter electrode by controlling the voltage of the gate electrode.

  The second semiconductor element 26 is, for example, a free-wheeling diode element that prevents damage to the first semiconductor element (IGBT) 25 due to back electromotive force. The upper surface of the second semiconductor element 26 is electrically connected to the emitter electrode of the first semiconductor element 25 via the second solder layer 24b, the upper electrode 27, and the second solder layer 24b. On the other hand, the lower surface of the second semiconductor element 26 is electrically connected to the collector electrode of the first semiconductor element 25 via the first solder layer 24a, the lower electrode 23, and the first solder layer 24a.

  The upper electrode 27 and the lower electrode 23 are made of Al or Cu excellent in conductivity and heat dissipation.

  This semiconductor device has six sets of the basic configuration described above and forms an electric circuit described later.

  FIG. 2 is a diagram illustrating an example of an electric circuit of the semiconductor device. This semiconductor device constitutes a three-phase AC inverter circuit 30 that converts a DC current into a three-phase AC current by connecting six sets of IGBTs 25 and a reflux diode 26 in a three-phase bridge connection. The output part of the three-phase AC inverter circuit 30 is connected to a three-phase motor 31. For this reason, the rotational speed and output torque of the three-phase motor 31 can be easily changed by changing the on / off switching frequency of the IGBT 25.

  When a current flows through the three-phase AC inverter circuit 30 to drive the three-phase motor 31, heat is generated in the semiconductor elements 25 and 26. Since the semiconductor elements 25 and 26 do not operate normally when overheated, the heat sink 21 is installed.

  The heat sink 21 is made of Al or Cu having high thermal conductivity. The heat generated in the semiconductor elements 25 and 26 is radiated by the heat radiating plate 21 via an insulating sheet 22 described later. This prevents overheating of the semiconductor elements 25 and 26 and prevents thermal destruction of the semiconductor elements 25 and 26.

  The insulating sheet 22 is formed of, for example, an epoxy resin that is excellent in flexibility and insulation. Silicon grease may be applied to the surface of the insulating sheet 22 in order to improve adhesion to the heat radiating plate 21 and enhance heat dissipation. The silicon grease fills the gaps between the concave and convex portions of the lower electrode 23 and the heat radiating plate 21, and quickly conducts heat from the lower electrode 23 to the heat radiating plate 21.

  Epoxy resin has low heat dissipation compared to the heat sink 21, and if it is too thick, the heat of the semiconductor elements 25 and 26 is difficult to conduct to the heat sink 21, so that the insulation between the lower electrode 23 and the heat sink 21 is improved. As thin as possible.

  As described above, the insulating sheet 22 is inserted between the lower electrode 23 and the heat radiating plate 21 to ensure insulation between one lower electrode 23 and the other five lower electrodes 23. Details of the pressure bonding method between the lower electrode 23 and the heat sink 21 will be described later.

  3 and 4 are views showing an embodiment of the pressure-bonding method of the present invention, where (a) is a schematic perspective view, and (b) is a cross-sectional view taken along line AA of (a). . The crimping method of the present embodiment is such that the lower electrode 23, the semiconductor elements 25 and 26, and the upper electrode 27 are soldered and laminated, and the lower electrode 23 and the heat sink are interposed via the insulating sheet 22. 21 and the second step (see FIG. 4).

  In the first step, first, a columnar auxiliary positioning jig 41 is installed on the lower electrode 23 as shown in FIG.

  Subsequently, as shown in FIG. 3B, two first solder foils 24a are arranged on the lower electrode 23 so as to sandwich the auxiliary positioning jig 41, and the first solder foils 24a are arranged on the first solder foils 24a. One of the first semiconductor element 25 and the second semiconductor element 26 is mounted. That is, the rectangular first semiconductor element 25 and the second semiconductor element 26 are disposed on the lower electrode 23 so as to sandwich the columnar auxiliary positioning jig 41.

  Subsequently, the upper electrode 27 is installed on the semiconductor elements 25 and 26 via the second solder foil 24b.

  The height-direction dimension of the auxiliary positioning jig 41 is smaller than the total height-direction dimension of the first solder foil 24a, the semiconductor elements 25, 26, and the second solder foil 24b, and the gap between the lower electrode 23 and the upper electrode 27. It is getting smaller.

  Subsequently, a frame-shaped positioning jig 42 is attached. The opening 43 of the positioning jig 42 has a quadrangular shape in plan view, and has a structure in which the area decreases in three steps from the bottom to the top along the height direction. The openings 43a, 43b, 43c at the respective stages form cavities in which the outer peripheral surfaces of the lower electrode 23, the semiconductor elements 25, 26, and the upper electrode 27 are substantially inverted.

  When the positioning jig 42 is mounted from the lower opening 43a, the opening 43a sequentially stores the upper electrode 27, the semiconductor elements 25 and 26, and the lower electrode 23 inside. The opening 43b following the opening 43a sequentially houses the upper electrode 27 and the semiconductor elements 25 and 26 inside. When the mounting of the positioning jig 42 is finally completed, the lower electrode 23 is positioned in the large opening 43a, the semiconductor elements 25 and 26 are positioned in the small opening 43b, and the upper electrode 27 is positioned in the predetermined position in the smaller opening 43c. can do. Further, in the state where the positioning is completed, the auxiliary positioning jig 41 is engaged with the groove portions 44 a and 44 b formed on the pair of left and right side surfaces of the positioning jig 42, and the first semiconductor element 25, the second semiconductor element 26, Are held at predetermined intervals. In this way, the lower electrode 23, the semiconductor elements 25 and 26, and the upper electrode 27 are positioned.

  Finally, heat treatment is performed in an atmospheric furnace with the auxiliary positioning jig 41 and the positioning jig 42 attached, and the first solder foil 24a and the second solder foil 24b are melted to form the lower electrode 23, the semiconductor elements 25, 26, The upper electrode 27 is soldered. Soldering is performed at a relatively low temperature at which the semiconductor elements 25 and 26 are not thermally destroyed, for example, at 180 ° C. to 300 ° C.

  For the solder foils 24a and 24a, for example, a Sn—Pb alloy, a Sn—Ag—Cu alloy, a Sn—Zn—Bi alloy, or a Sn—Zn—Al alloy can be used.

  By soldering and metal bonding, the emitter electrode of the first semiconductor element (IGBT) 25 and the second semiconductor element (freewheeling diode) via the first solder layer 24a, the upper electrode 27, and the first solder layer 24a. 26 is electrically connected to the anode side. In addition, the collector electrode of the first semiconductor element (IGBT) 25 and the cathode side of the second semiconductor element (reflux diode) 26 are conducted through the second solder layer 24b, the lower electrode 23, and the second solder layer 24b. The

  The auxiliary positioning jig 41 and the positioning jig 42 used in the first step are formed of ceramics having poor wettability with molten solder and high heat resistance. Thereby, it is possible to prevent the auxiliary positioning jig 41 and the positioning jig 42 from being fused to the molten solder, and the auxiliary positioning jig 41 and the positioning jig 42 are removed and reused even after soldering. can do. The auxiliary positioning jig 41 and the positioning jig 42 may be made of metal, and the mold releasability may be ensured by applying ceramic fine particles to the surface of the metal.

In addition, although inexpensive Al ₂ O ₃ may be used for the ceramic forming the auxiliary positioning jig 41 and the positioning jig 42, AlN, Si ₃ N ₄ , SiC having higher thermal conductivity than Al ₂ O _3. May be used. By increasing the thermal conductivity of the auxiliary positioning jig 41 and the positioning jig 42, when performing heat treatment for soldering, the temperature raising time can be shortened and the temperature can be equalized, and the heat treatment time can be shortened. And good soldering can be performed.

  Further, since the auxiliary positioning jig 41 and the positioning jig 42 are formed of ceramics having a relatively small thermal expansion coefficient, the upper electrode 27 and the lower electrode 23 formed of Al or Cu having a relatively large thermal expansion coefficient The difference in thermal expansion is large. Therefore, when soldering, a sufficient clearance is set so that the auxiliary positioning jig 41 and the positioning jig 42 do not damage the upper electrode 27, the semiconductor elements 25, 26, and the lower electrode 23 by suppressing thermal expansion. Yes.

  In the second step, the lower electrode 23, the semiconductor elements 25 and 26, and the upper electrode 27 soldered in the first step are pressure-bonded to the heat sink 21 via the insulating sheet 22.

  In the second step, first, as shown in FIG. 4A, an insulating sheet 22 is interposed on the lower electrode 23 side, the semiconductor elements 25 and 26, and the upper electrode 27 soldered in the first step. The heat sink 21 is arranged.

  Subsequently, as shown in FIG. 4B, a columnar auxiliary crimping jig 51 having a quadrangular cross section is inserted into a hollow section having a quadrangular cross section surrounded by the lower electrode 23, the semiconductor elements 25 and 26, and the upper electrode 27. To do. The auxiliary crimping jig 51 may also be used as the auxiliary positioning jig 41. When the auxiliary positioning jig 41 is also used, the second positioning process can be started without removing the auxiliary positioning jig 41 after the first process, and the work can be simplified. 25, 26 and the solder layers 24a and 24b can be prevented from being damaged.

  The auxiliary crimping jig 51 may be formed of ceramics or metal, but is preferably a metal having high fracture toughness, for example, cast iron or stainless steel.

  Further, the auxiliary crimping jig 51 may be provided with a protrusion (not shown) on the lower surface. When a later-described crimping jig 52 is pressed, the lower electrode 23 can be crimped to the heat radiating plate 21 by the protrusion on the lower surface.

  Subsequently, a frame-shaped crimping jig 52 is mounted. The crimping jig 52 may also be used as the positioning jig 42. When the positioning jig 42 is also used, the second process can be started without removing the positioning jig 42 after the first process, and the work can be simplified.

  The crimping jig 52 may be formed of ceramics or metal, but is preferably a metal having high fracture toughness, for example, cast iron or stainless steel.

  The auxiliary crimping jig 51 and the crimping jig 52 have a sufficient clearance so that the upper electrode 27, the semiconductor elements 25 and 26, and the lower electrode 23 are not pressed and damaged by elastic deformation during crimping. Yes.

  When the crimping jig 52 is mounted from the lower opening 53a, the opening 53a stores the upper electrode 27, the semiconductor elements 25 and 26, and the lower electrode 23 sequentially inward as in the positioning jig 42. I will do it. The opening 53b following the opening 53a sequentially stores the upper electrode 27 and the semiconductor elements 25 and 26 inside. When the mounting of the crimping jig 52 is completed, the lower electrode 23 is stored in the large opening 53a, the semiconductor elements 25 and 26 are stored in the small opening 53b, and the upper electrode 27 is stored in the smaller opening 53c.

  When the crimping jig 52 is completely mounted, the crimping jig 52 is in contact with the peripheral edge of the upper surface of the lower electrode 23 at the stepped portion 55 between the large opening 53a and the small opening 53b, and the semiconductor elements 25, 26. The upper electrode 27 is surrounded while forming a gap.

  Further, in this state, the auxiliary crimping jig 51 is sandwiched between the upper ends of the pair of left and right grooves 54 a and 54 b formed on the side surface of the crimping jig 52 and the lower electrode 23. That is, the auxiliary crimping jig 51 has an upper surface in contact with the upper ends of the grooves 54 a and 54 b of the crimping jig 52 and a lower surface in contact with the lower electrode 23.

  Subsequently, when the crimping jig 52 is pressed, the peripheral edge of the lower electrode 23 can be pressed by the stepped portion 55 of the crimping jig 52, and the lower part is pressed by the auxiliary crimping jig 51 disposed between the semiconductor elements 25 and 26. The vicinity of the center of the electrode 23 can be pressed. Thereby, the periphery and the center vicinity of the lower electrode 23 can be pressed, and the lower electrode 23 and the heat sink 21 can be crimped | compressed uniformly.

  Here, since the crimping jig 52 forms a gap with the semiconductor elements 25 and 26, even if pressed, the crimping jig 52 does not directly press the semiconductor elements 25 and 26. In addition, since the crimping jig 52 forms a gap with the upper electrode 27, it does not press the semiconductor elements 25 and 26 via the upper electrode 27 even when pressed. Therefore, damage to the semiconductor elements 25 and 26 can be prevented.

  Subsequently, the lower electrode 23, the insulating sheet 22, and the heat radiating plate 21 are crimped, and the lower electrode 23 and the heat radiating plate 21 are screwed to each other, so that the lower electrode 23, the insulating sheet 22, and the heat radiating plate 21 are pressed. Can be maintained. After the screw fastening, the auxiliary crimping jig 51 and the crimping jig 52 are removed and reused.

  A semiconductor device having the electric circuit of FIG. 2 is manufactured by sealing six basic configurations of the semiconductor device thus formed together with an insulating gel in one resin package (not shown). . The periphery of the resin package is bonded to the heat sink 21 and includes input / output terminals outside.

  As described above, according to the crimping method of this embodiment, the crimping jig 52 can be pressed to press the peripheral edge of the lower electrode 23 with the stepped portion 55 of the crimping jig 52, and the semiconductor elements 25, 26. The vicinity of the center of the lower electrode 23 can be pressed by the auxiliary crimping jig 51 inserted therebetween, and the lower electrode 23 and the heat sink 21 can be uniformly crimped. Further, even if the crimping jig 52 is pressed, the semiconductor elements 25 and 26 and the upper electrode 27 are not pressed, and the semiconductor elements 25 and 26 sandwiched between the upper electrode 27 and the lower electrode 23 are prevented from being damaged. Can do. Further, the reusable auxiliary crimping jig 51 and the crimping jig 52 can be used to crimp the lower electrode 23 to the heat radiating plate 21 without drilling holes in the upper electrode 27 and the lower electrode 23.

  If the first step of the present embodiment is performed after the second step of the present embodiment, the entire surface of the lower electrode 23 can be pressed, and the lower electrode 23 and the radiator plate 21 can be uniformly bonded. . However, the resin insulating sheet 22 disposed between the lower electrode 23 and the heat sink 21 in the second step is damaged by the heat treatment in the first step, and insulation cannot be ensured. Therefore, the first step of this embodiment cannot be performed after the second step of this embodiment.

  The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, although the semiconductor elements 25 and 26 of the present embodiment are composed of the first semiconductor element 25 and the second semiconductor element 26, the auxiliary crimping jig 51 is inserted between the plurality of semiconductor elements to press the lower electrode 23. As many as possible, there is no limit to the number of semiconductor elements disposed between the lower electrode 23 and the upper electrode 27.

  In the present embodiment, the lower electrode 23 and the heat sink 21 of the semiconductor elements 25 and 26 are crimped. However, when the heat sink 21 is disposed on the upper electrode 27 side, the upper portions of the semiconductor elements 25 and 26 are disposed. The electrode 27 and the heat sink 21 may be pressure-bonded. Even the upper electrode 27 of the semiconductor elements 25 and 26 can be pressure-bonded to the heat radiating plate 21 as in the case of the lower electrode 23.

  Further, in this embodiment, the insulating sheet 22 is inserted between the lower electrode 23 and the heat radiating plate 21 to ensure insulation between one lower electrode 23 and the other five lower electrodes 23. As long as the potentials of the plurality of lower electrodes 23 are always controlled to be the same, the plurality of lower electrodes 23 may be connected to each other to be conducted. For example, in the three-phase AC inverter circuit of FIG. 2, the three lower electrodes 23 can be connected to each other to be conducted.

  Further, in this embodiment, the lower electrode 23 and the heat radiating plate 21 are screwed together via the insulating sheet 22, but the lower electrode 23 and the heat radiating plate 21 are adhesively fixed using the adhesive insulating sheet 22. Also good. In any case, the lower electrode 23 and the radiator plate 21 can be uniformly crimped using the auxiliary crimping jig 51 and the crimping jig 52 without damaging the semiconductor elements 25 and 26. The adhesive insulating sheet 22 is formed of, for example, a resin containing a pressure sensitive adhesive or a hot melt adhesive.

It is sectional drawing which showed an example of the basic composition of a semiconductor device. It is a figure showing an example of an electric circuit of a semiconductor device. It is the figure which showed one Example of the crimping | compression-bonding method of this invention. It is the figure which showed one Example of the crimping | compression-bonding method of this invention. It is sectional drawing which showed an example of the structure of the conventional semiconductor device.

Explanation of symbols

21 Heat Dissipation Plate 22 Insulating Sheet 23 Lower Electrode 25 First Semiconductor Element 26 Second Semiconductor Element 27 Upper Electrode 41 Auxiliary Positioning Jig 42 Positioning Jig 51 Auxiliary Crimping Jig 52 Crimping Jig

Claims (1)

In a method of crimping a semiconductor element electrode and a heat sink plate, sandwiching a plurality of semiconductor elements between an upper electrode and a lower electrode, and crimping one of the upper electrode and the lower electrode to a heat sink plate,
A pressure bonding jig is inserted between the plurality of semiconductor elements, and is surrounded by forming a gap with the plurality of semiconductor elements and the other electrode, and is bonded to the peripheral edge of the one electrode and the auxiliary pressure bonding jig. A method of crimping a semiconductor element electrode and a radiator plate, wherein a jig is attached and the crimping jig is pressed to crimp the one electrode to the radiator plate.

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