JP2015069982A - Power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power module capable of improving the heat radiation property against heat generation in a lead by ultrasonic bonding between a wiring pattern on an insulation substrate and the lead.SOLUTION: A power module houses, in a case: a base having a heat radiation property; an insulation substrate mounted on the base; a wiring pattern formed on the insulation substrate; a semiconductor element mounted on the wiring pattern; and a lead electrically connecting the wiring pattern with the exterior. The power module further comprises heat communication means for communicating heat generated at the lead to the base.

Description

  The present invention relates to a power module in which a semiconductor element and a lead are connected to an insulating substrate, and more particularly to a power module in which a lead is connected using ultrasonic bonding or the like.

  A conventional power module is made of ceramic or the like, and has a structure in which a plurality of semiconductor elements are mounted on an insulating substrate on which a wiring pattern made of copper or aluminum is formed and housed in the module. In such a power module, generally, so-called wire bonding is used for connection between the electrodes of each semiconductor element and the wiring pattern, between the wiring patterns, and between the wiring pattern and the leads. In order to flow a large current, a method of bonding a plurality of wires in parallel has been used.

  In recent years, due to the demand for miniaturization of power modules, a method of using a plate-like lead capable of making the connection occupation area smaller than the area during wire bonding has been devised. As a method for connecting such plate-like leads, a method using solder or ultrasonic bonding is already known.

  Ultrasonic bonding is a method in which two metals are rubbed together by applying an amplitude and a load with an ultrasonic tool to remove the oxide film present on the metal surface, and the new surfaces are bonded to each other by solid phase diffusion. is there.

  In addition, what was described in the following patent document 1 is already known as a technique which joins a plate-shaped lead and the wiring pattern on an insulated substrate using an ultrasonic bonding technique. In this patent document 1, it is described that a wiring pattern made of Al is applied on an insulating substrate, and Ni plating is applied to improve the bonding property when a semiconductor element is bonded onto the wiring pattern by solder. However, for the places where the leads and wiring patterns are ultrasonically bonded, it has been found that the above-mentioned Ni plating rather deteriorates the bondability. Therefore, the Ni plating should not be applied to the places where ultrasonic bonding is performed. It is described that the bonding property is improved by making it.

JP 2006-278913 A

  In the above-described conventional technology, the improvement of the bonding property between the lead and the wiring pattern is described together with the bonding property of the solder. However, the description about the suppression of the heat generation amount of the lead and the improvement of the heat radiation property is described. Therefore, there has been a problem in reducing the size and capacity of the power module.

  That is, particularly in the case of using a plate-like lead in the power module, most of the lead is arranged in a space in the casing or in a filled gel, and a large current flows to the module. Heat is generated and the lead itself becomes hot. Therefore, how to dissipate such heat to the outside or to suppress the amount of heat generation has become an important consideration for the design of power modules.

  That is, the present invention has been achieved in order to eliminate the drawbacks of the prior art described above, and the object is to ultrasonically join the wiring pattern on the insulating substrate and the lead, particularly in the lead. An object of the present invention is to provide a power module having a configuration capable of improving heat dissipation of heat generation.

  In the present invention, in order to solve the above problems and achieve the object, a base having heat dissipation, an insulating substrate mounted on the base, a wiring pattern formed on the insulating substrate, and the wiring pattern In a power module in which a semiconductor element mounted thereon and a lead for electrically connecting the wiring pattern to the outside are housed in a case, heat generated by the lead is further transmitted to the base. There is provided a power module comprising a heat transfer means.

  In the power module described above, the heat transfer means includes a wiring pattern that does not contribute to an electric circuit and is formed on a part of the insulating substrate, and the leads are on the insulating substrate. Legs that are joined to a wiring pattern that does not contribute to the electrical circuit, or the heat transfer means includes a heat radiation lead different from the lead, and the heat radiation lead is joined to the base. It is preferable that the heat dissipating lead further includes a leg portion joined to a wiring pattern that does not contribute to an electric circuit on the insulating substrate.

  According to the present invention, Joule heat generated when a large current is passed through the leads can be efficiently radiated to the wiring pattern and the base. In addition, since the temperature rise of the lead can be prevented, the downsizing design can be facilitated.

It is a perspective view which shows the whole structure of the power module which becomes Example 1 of this invention. It is a perspective view which shows the power module mentioned above in the state except the resin case. It is the expansion | deployment perspective view which specifically extracted and showed the lead part from the power module mentioned above. It is a top (upper surface) figure of the power module which becomes Example 1 mentioned above. It is a perspective view which shows the whole structure of the power module which becomes Example 2 of this invention. It is a top (upper surface) figure of the power module which becomes Example 2 mentioned above. It is a perspective view which shows the power module which becomes Example 3 of this invention in the state which removed the resin case. It is the perspective view which looked at the power module which becomes Example 3 mentioned above from the other side (namely, upper right side of FIG. 7). It is a top (upper surface) figure of the power module which becomes Example 3 mentioned above.

  Hereinafter, embodiments of a power module embodying the present invention will be described in detail with reference to the accompanying drawings.

  A power module according to a first embodiment of the present invention will be described with reference to the attached FIGS.

  First, FIG. 1 is a perspective view showing the overall configuration of the power module of this embodiment. In this figure, the base 1 is a substantially plate-like member made of aluminum, copper, aluminum alloy, copper alloy, AlSiC or the like mainly having good thermal conductivity from the viewpoint of heat dissipation. Cooling is performed by air cooling. Reference numeral 7 in the figure denotes a case. Because of the complexity of the shape, plastic that is easy to manufacture is mainly used as the material. Further, the base 1 and the case 7 are fixed to each other by, for example, a screw or an adhesive. The case 7 is provided with a screw hole 8 used when connecting to an external terminal (not shown), and in addition, a signal pin 9 is also provided. The signal pin 9 is connected mainly to the wiring pattern described below using an aluminum wire. Although not shown in the figure, normally, in order to withstand pressure, a gel is injected into the case 7 and a lid made of plastic or the like is provided.

  As described above, in the power module, since cooling is performed from the back surface of the base 1 by water cooling or air cooling, how the heat generated in the lead 5 for flowing a large current disposed therein is detected. Depending on whether it is transmitted to 1, the heat dissipation performance will be affected.

  Next, FIG. 2 is a perspective view when the resin case 7 is removed from the configuration of the power module of FIG. 1 described above. The base indicated by reference numeral 1 in the figure has an insulating substrate 2 mounted thereon via a joining member such as solder, and a wiring pattern 3 is formed on the front and back surfaces of the insulating substrate 2. Yes. A power semiconductor element 4 is mounted on the upper surface of the wiring pattern 3 via a bonding member such as solder, and a lead 5 is mounted on the wiring pattern 3. For the connection between the wiring pattern 3 and the lead 5, bonding by soldering or ultrasonic bonding is applied. The insulating substrate 2 is mainly made of a material such as alumina, AlN, or SiN, and the wiring pattern 3 is mainly made of copper or aluminum.

  Further, FIG. 3 is an exploded perspective view showing the lead portion extracted from the configuration of the power module of FIG. 2 described above. In particular, the lead 5 is made of, for example, copper or A plurality of plate-like members such as aluminum, copper alloy, and aluminum alloy are formed, and an insulating member 6 is mounted between them for insulation. More specifically, in the power module of this embodiment, the lead 5 is composed of three (sheets) leads 5a, 5b, and 5c, and the insulating member 6a, 6b is installed (inserted), and a plurality of legs extending downward are formed on both sides. This insulating member is designed to be slightly larger than the outer shape of the adjacent lead from the viewpoint of withstand voltage, and as an example, a material such as nonwoven fabric or plastic is used.

  Next, FIG. 4 is a plan (top) view of the power module of the present embodiment, showing a state where the lead portion shown in FIG. 3 is removed. In this figure, for example, a power semiconductor element 4 and a temperature detection thermistor 10 are mounted on the wiring pattern 3, and the wiring pattern 3, the semiconductor element 4, the signal pin 9, the thermistor 10, etc. A number of wires 11 are used (arranged) for electrical connection. In addition, as a material of these wires 11, aluminum is generally used mainly and the diameter is 0.3-0.5 mm widely used. A broken line in the drawing indicates a so-called bonding position 12 for connecting the lead 5 to the wiring pattern 3. However, among the wiring patterns indicated by the broken lines, in particular, the wiring patterns indicated by reference numerals 3a, 3b, 3c, and 3d are not connected by wires to other wiring patterns, so-called electric circuits. However, it is an unnecessary wiring pattern, however, it joins the lead 5 (particularly, its leg) to efficiently dissipate the heat generated in the lead 5 to the base 1.

  As described above, in the power module in which a power semiconductor element or the like is housed, the wiring patterns 3a, 3b, 3c, and 3d that do not contribute to the electric circuit are provided on the insulating substrate 2, and the leads 5 with a large amount of heat generation are provided. By adopting a configuration in which a part is joined to the wiring patterns 3a, 3b, 3c, and 3d, the heat generated in the leads 5 can be efficiently released to the base 1. Since the temperature rise of the leads can be prevented, the design can be easily performed in order to realize the miniaturization of the power module.

  Next, a power module according to another embodiment (second embodiment) of the present invention will be described in detail with reference to FIGS. 5 and 6.

  FIG. 5 is a perspective view showing the power module according to the second embodiment with its resin case removed, similar to FIG. 2 described above. As is clear from this figure, the insulating substrate 2 is mounted on the base 1 via a joining member such as solder, and the wiring pattern 3 is formed on the front and back surfaces of the insulating substrate 2. ing. A power semiconductor element 4 is mounted on the upper surface of the wiring pattern 3 via a bonding member such as solder, and a lead 5 is mounted on the wiring pattern 3. In addition, as in the above-described first embodiment, bonding by soldering or ultrasonic bonding is applied to the connection.

  Further, the lead 5 is also formed of a plurality of leads, and an insulating member 6 is mounted (inserted) between them for insulation as in the first embodiment.

  In the present embodiment (embodiment 2), a heat radiating lead 13 is further mounted on the lead 5 via an insulating member 6c. The heat dissipating lead 13 is joined to the base 1 in order to efficiently release Joule heat generated by current flowing through the lead 5 to the base 1. As a bonding method, solder or ultrasonic bonding is used.

  The heat dissipation lead 13 is also formed of a plate-like member such as copper, aluminum, copper alloy, or aluminum alloy, as in the case of the lead 5. A plurality of leg portions 131 extending in the direction is formed.

  FIG. 6 is a plan (top) view of the power module according to the second embodiment with a lead removed. Here again, the power semiconductor element 4 and the temperature detection thermistor 10 are mounted on the wiring pattern 3, and the wiring pattern 3 is electrically connected to the semiconductor element 4, the signal pin 9, the thermistor 10, and the like. As described above, a large number of wires 11 are used. In addition, the broken line in the figure also shows the joint position 12 for electrically connecting the lead 5 (its leg) on the wiring pattern 3 in the same manner as described above. Further, in the present embodiment (embodiment 2), the joining position 14 is provided on the base 1 at a position where the above-described heat radiation lead 13 (its leg portion 131) is connected.

  As described above, in the power module in which a power semiconductor element or the like is housed, a heat dissipation lead 13 is further provided together with the plurality of leads 5, and the heat dissipation lead 13 is connected to the base 1. Thus, similarly to the above, the heat generated in the lead 5 can be efficiently released to the base 1. In addition, since the temperature rise of the lead can be prevented, the design can be easily performed to realize the miniaturization. Further, by providing the above-described heat dissipation lead 13 and directly connecting the heat dissipation lead to the base 1, the degree of freedom in designing the power module without being restricted by the layout of the wiring pattern on the insulating substrate. Can be improved.

  In the drawing of this embodiment, an example is shown in which the heat radiation lead 13 and the base 1 are joined at a total of eight locations. However, the present invention is not limited to this, and for example, current capacity, module size, etc. Needless to say, the number of joints can be increased or decreased due to the restrictions.

  Subsequently, a power module according to still another embodiment (Example 3) of the present invention will be described in detail with reference to FIGS.

  FIG. 7 is a perspective view of the power module according to the third embodiment with the resin case removed. As is clear from this figure, the insulating substrate 2 is mounted on the base 1 via a joining member such as solder, and the wiring pattern 3 is formed on the front and back surfaces of the insulating substrate 2. ing. Further, a power semiconductor element 4 is mounted on the upper surface of the wiring pattern 3 via a bonding member such as solder, and further, a lead 5 is mounted on the wiring pattern 3 for connection. As in the first and second embodiments, the bonding by soldering or ultrasonic bonding is applied. Similarly, the lead 5 is formed of a plurality of leads, and an insulating member 6 for insulation is mounted (inserted) between them.

  Further, in the present embodiment (embodiment 3), similarly to the above embodiment 2, the heat radiating lead 13 is further mounted on the lead 5 via the insulating member 6c. Is joined to the base 1 and efficiently contributes to the electric circuit formed on the wiring pattern 3 in order to efficiently release Joule heat generated by current flowing through the leads 5 to the base 1. The wiring pattern is also joined. As a bonding method, solder or ultrasonic bonding is used.

  More specifically, the heat dissipating lead 13 has a plurality of legs 131 extending downward on both sides thereof, and the power module shown in FIG. 7 on the opposite side (that is, FIG. 7). As is clear from FIG. 8, which is a perspective view as viewed from the upper right side of FIG. 8, a plurality of legs 132 extending downward from one side (lower side in FIG. 8) of the heat radiating lead 13 are further formed. ing. Then, the lead 5 efficiently releases the generated heat to the base 1, so that the plurality of second legs 132 together with the base 1 are connected to the wiring patterns 3e, 3f, 3g, and 3h that do not contribute to the electric circuit. Are also connected, respectively.

  FIG. 9 is a plan (upper surface) view of the power module according to the third embodiment with the leads removed. Here again, the power semiconductor element 4 and the temperature detection thermistor 10 are mounted on the wiring pattern 3, and the wiring pattern 3 is electrically connected to the semiconductor element 4, the signal pin 9, the thermistor 10, and the like. As described above, a large number of wires 11 are used. In addition, the broken line on the wiring pattern 3 in the figure also indicates the bonding position 12 for electrically connecting the lead 5 (its leg portion) on the wiring pattern 3 and the base shown in the second embodiment, as described above. In addition to the joining position 14 for connecting the above-described heat radiation lead 13 (its leg portion 131) onto 1, the heat radiation lead 13 (particularly, its leg portion 132) is also placed on the wiring pattern 3 that does not contribute to the electric circuit. Are connected to each other.

  As described above, in the power module in which a power semiconductor element or the like is housed, a heat radiating lead 13 is provided together with the plurality of leads 5, and the heat radiating lead 13 is connected to the base 1. By adopting a configuration in which the wiring pattern 3 that does not contribute to the circuit is connected, the heat generated in the lead 5 can be released to the base 1 more efficiently. In addition, since the temperature rise of the lead can be prevented, the design can be easily performed to realize the miniaturization. In particular, in this example (Example 3), as described above, the lead and the heat dissipation lead are connected to the base together with the wiring pattern so as to surround the chip-like component such as the power semiconductor element. In addition, since a compressive force is always applied to the joining member between the insulating substrate and the base, the effect of improving the connection reliability is also achieved.

  3, 3a to 3h ... wiring pattern, 5 ... lead, 12 ... joining position, 13 ... heat dissipation lead, 131 ... leg, 132 ... second leg, 14 ... joining position

Claims (5)

A base with heat dissipation,
An insulating substrate mounted on the base;
A wiring pattern formed on the insulating substrate;
A semiconductor element mounted on the wiring pattern;
In a power module in which a lead for electrically connecting the wiring pattern to the outside is housed in a case,
A power module comprising heat transfer means for transferring heat generated in the lead to the base. In the power module according to claim 1,
The heat transfer means includes a wiring pattern that does not contribute to an electric circuit formed on a part of the insulating substrate, and the lead is a wiring pattern that does not contribute to an electric circuit on the insulating substrate. A power module comprising a leg to be joined. In the power module according to claim 1,
The power module, wherein the heat transfer means includes a heat dissipation lead different from the lead, and the heat dissipation lead includes a leg portion joined to the base. In the power module according to claim 3,
The heat radiation lead further includes a leg portion joined to a wiring pattern that does not contribute to an electric circuit on the insulating substrate.   The power module according to any one of claims 1 to 4, wherein the joining is performed by soldering or ultrasonic joining.

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