JP2011192689A - Power module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the heat dissipation of a power module for mounting a semiconductor bare chip on a substrate by a connection method using wire bonding and a ribbon wire. <P>SOLUTION: In the power module 10 including a substrate 11 provided with one surface and the other surface, a heat spreader 12 disposed at the side of one surface of the substrate 11, a semiconductor bare chip 13 mounted to the substrate 11 through the heat spreader 12, a sealing material 14 for sealing the semiconductor bare chip 13 mounted to the substrate 11, and a radiator 15 provided at the side of the other surface of the substrate 11, the heat spreader 12 has a planar first diffusion part 121 in thermal contact with the substrate 11 and the semiconductor bare chip 13, respectively, and one or a plurality of second diffusion parts 122 erected from the first diffusion part 121 in the opposite direction of the substrate 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power module in which an electronic component such as a semiconductor element is mounted on a substrate.

  Conventionally, a power module in which a semiconductor element is mounted on a resin substrate or the like in a bare chip state is known. Such a power module is used, for example, in power equipment such as an air conditioner, and performs power conversion and control.

  In the conventional power module 80 shown in FIG. 8, the semiconductor bare chip 3 is mounted on one surface side of the substrate 1 via the heat spreader 2, and the radiator 5 is disposed on the other surface side of the substrate 1 via an insulating layer (not shown). Is provided. An electrode pad 6 is formed on one surface side of the substrate 1, and a terminal (not shown) on the upper surface of the semiconductor bare chip 3 and the electrode pad 6 are connected by an electrical connection member 7. The semiconductor bare chip 3 is protected by a sealing material 4 such as a resin. A well-known thermal via 8 is provided at a location where the substrate 1 is in thermal contact with the heat spreader 2. Heat generated in the semiconductor bare chip 3 is conducted to the radiator 5 via the heat spreader 2 and the thermal via 8 of the substrate 1. Since the heat spreader 2 diffuses heat, the heat dissipation of the power module 80 can be improved.

  In recent years, due to the multi-functionality of power equipment, a corresponding amount of power is required for its operation. On the other hand, the power module is required to be miniaturized, and the heat generation amount per unit area (or unit volume) increases according to the demand. Therefore, heat dissipation measures for the power module are important.

  In the power module 80 shown in FIG. 8, the larger the area of the heat spreader 2, the larger the contact area with the radiator 5 through the thermal via 8 of the substrate 1, and the heat dissipation of the power module 80 is improved. However, if the area of the heat spreader 2 is increased, the size of the power module 80 also increases, and therefore it is not possible to meet the demand for downsizing of the power module 80.

  For example, the heat dissipation of the power module 80 can be further improved by using a metal substrate such as an Al substrate having a higher thermal conductivity than a resin substrate, but the Al substrate is more expensive than the resin substrate, It is not preferable in terms of cost.

  The following patent document discloses an electronic device in which a heat spreader is provided so as to cover a semiconductor chip, and heat radiating fins are attached to the heat spreader. The heat generated in the semiconductor chip is transferred to the heat radiating fins through the heat spreader, so that the heat is radiated. A recess corresponding to the shape of the semiconductor chip is formed in the heat spreader. Since the semiconductor chip is accommodated in the recess, the area in thermal contact with each other is increased, and the heat dissipation efficiency is improved.

  However, the patent document does not consider a wire bonding or a connection method using a ribbon electric wire. Therefore, it cannot be applied to the power module 80.

Japanese Patent Laid-Open No. 9-218347

  The present invention has been made in view of such circumstances, and an object of the present invention is to improve the heat dissipation of a power module in which a semiconductor bare chip is mounted on a substrate by a bonding method using wire bonding or a ribbon electric wire. is there.

  The power module of the present invention includes a substrate having one surface and another surface, a heat spreader disposed on one surface of the substrate, a semiconductor bare chip mounted on the substrate via the heat spreader, and a semiconductor bare chip mounted on the substrate. A sealing material for sealing, and a radiator provided on the other surface side of the substrate, wherein the heat spreader is in a plate-like first diffusion portion in thermal contact with the substrate and the semiconductor bare chip, and from the first diffusion portion. And a second diffusion portion that stands in the opposite direction of the substrate. The heat generated in the semiconductor bare chip is diffused toward the first diffusion portion and the second diffusion portion of the heat spreader.

  The power module of the present invention includes an electrode pad provided on one surface of the substrate, and an electrical connection member that electrically connects the semiconductor bare chip and the electrode pad, and the second diffusion portion is connected to the electrical connection member. Non-contact.

  In the power module of the present invention, the second diffusion portion has a plate shape or a rod shape.

  In the power module of the present invention, a part of the second diffusion portion is exposed from the sealing material.

  According to the power module of the present invention, since the second diffusion portion is provided so as to stand in the opposite direction of the substrate from the first diffusion portion of the heat spreader, the area of the portion where the heat spreader is in thermal contact with the substrate is enlarged. The surface area of the heat spreader as a whole can be increased. Thereby, the amount of heat diffusion is improved, the heat dissipation of the power module is improved, and at the same time, the demand for downsizing of the power module can be met.

  According to the power module of the present invention, since the second diffusion portion of the heat spreader is provided so as to be non-contact with the electrical connection member, the electrical connection member electrically connects the semiconductor bare chip and the electrode pad. It won't be a hindrance. Thereby, it can apply to the power module which mounts a semiconductor bare chip on a board | substrate by the connection method using wire bonding or a ribbon electric wire.

  According to the power module according to the present invention, since the second diffusion portion can be formed in a plate shape or a rod shape, the degree of freedom with respect to the arrangement of the electrical connection members is high. This makes it possible to deal with various patterns with respect to the positional relationship between the terminals of the semiconductor bare chip and the electrode pads on the substrate.

  According to the power module according to the present invention, since a part of the second diffusion portion is exposed from the sealing material, the heat diffused by the heat spreader can be conducted to the air without passing through the sealing material. it can. Thereby, the heat dissipation of a power module can further be improved.

It is sectional drawing along the (a) top view and (b) A1-A1 line which show the power module which concerns on 1st embodiment. It is sectional drawing along the A2-A2 line (refer Fig.1 (a)) which shows the power module which concerns on 1st embodiment. It is sectional drawing along the (a) top view and (b) B1-B1 line which show the modification of the power module which concerns on 1st embodiment. It is the (a) top view which shows the power module which concerns on 2nd embodiment, and sectional drawing along the C1-C1 line. It is sectional drawing which shows the power module which concerns on 3rd embodiment. It is sectional drawing which shows the other modification of the power module which concerns on 1st embodiment. It is sectional drawing which shows the modification of the power module which concerns on 3rd embodiment. It is sectional drawing along the (a) top view and (b) D1-D1 line which show the conventional power module.

  Hereinafter, embodiments of a power module according to the present invention will be described with reference to the drawings. In the present specification, each drawing is schematically shown, and when the same reference numeral is given, the same configuration is shown. In this specification, the one surface of the substrate indicates the surface on the side where the semiconductor bare chip or the like is provided, and the other surface of the substrate indicates the surface on the side where the radiator is provided. For convenience of explanation, the sealing material is not shown in the plan views of the drawings, and the electrode pads and the electrical connection members are not shown in the cross-sectional views (excluding FIG. 2).

  As shown in FIGS. 1 and 2, the power module 10 according to the first embodiment includes a substrate 11, a heat spreader 12 provided on one surface of the substrate 11, and a semiconductor mounted on the substrate 11 via the heat spreader 12. A bare chip 13, a sealing material 14 for sealing the semiconductor bare chip 13, and a radiator 15 provided on the other surface of the substrate 11 are provided.

  The substrate 11 is an insulating plate. An electronic circuit is formed on the substrate 11. Specifically, the substrate 11 may be a resin substrate using an epoxy resin or the like, or a ceramic substrate using alumina or the like. More specifically, the substrate 11 is a glass epoxy resin substrate or the like. Although not shown, the substrate 11 is appropriately provided with a well-known thermal via 18. Through the thermal via 18, heat conduction from the heat spreader 12 to the radiator 15 and connection between the semiconductor bare chip 13 and the electronic circuit are performed.

  The heat spreader 12 is a conductor having high thermal conductivity. The heat spreader 12 effectively diffuses the heat of the semiconductor bare chip 13. The heat spreader 12 is soldered on the thermal via 18 provided on the substrate 11.

  The heat spreader 12 includes a first diffusion part 121 and a second diffusion part 122. The first diffusion part 121 is formed in a plate shape and is in thermal contact with the substrate 11 and the semiconductor bare chip 13. The second diffusion part 122 is formed in a plate shape, and stands upright from the first diffusion part 121 in the direction opposite to the substrate 11. A second diffusion part 122 is formed at the end of the first diffusion part 121. The second diffusion part 122 is formed integrally with the first diffusion part 121 by any method such as bending or deep drawing. The second diffusion part 122 is not necessarily formed at the end of the first diffusion part 121. For example, you may form inside the edge part of the 1st spreading | diffusion part 121 by methods, such as welding.

  The size of the heat spreader 12 is appropriately designed according to the size of the semiconductor bare chip 13 and the width and thickness of the sealing material 14. The thickness of each of the first diffusion part 121 and the second diffusion part 122 is, for example, about 1 mm, but may be formed thinner. The thickness of the first diffusing portion 121 and the thickness of the second diffusing portion 122 are not necessarily the same, and may be formed so that their thicknesses are different from each other.

  As the material of the heat spreader 12, it is preferable to use a metal material such as copper or an alloy containing copper having a high thermal conductivity and a low thermal expansion coefficient. The thermal diffusion efficiency can be improved and thermal deformation can be prevented.

  The semiconductor bare chip 13 is an electronic component for performing power conversion and control in a power device. The semiconductor bare chip 13 is, for example, a semiconductor element such as a transistor or a diode, and more specifically, an IGBT (Insulated Gate Bipolar Transistor), an FWD (Free Wheeling Diode), or the like. The semiconductor bare chip 13 is mounted on one surface side of the substrate 11 so as to be electrically and thermally connected to the first diffusion portion 121 of the heat spreader 12. The semiconductor bare chip 13 and the electronic circuit formed on the substrate 11 are thermally connected via the heat spreader 12 and the well-known thermal via 18. You may connect to the electronic circuit of the board | substrate 11 not via the thermal via 18. FIG. For example, in the case of an IGBT bare chip, the collector is connected to the first diffusion unit 121.

  The sealing material 14 is for sealing and protecting the semiconductor bare chip 13 and is provided on one surface side of the substrate 11. Examples of the material of the sealing material 14 include a thermosetting resin having high heat resistance and low thermal stress, and more specifically, an epoxy resin, a phenol resin, or a synthetic resin combining these. This is because deformation due to heat can be prevented. The sealing material 14 is formed in an arbitrary shape such as a rectangular parallelepiped shape by a method such as cast molding or compression molding, and protects the semiconductor bare chip 13 by covering the entire semiconductor bare chip 13. At this time, the heat spreader 12 is simultaneously covered with the sealing material 14. This is to prevent a short circuit.

  The radiator 15 is for radiating heat generated in the semiconductor bare chip 13, and is provided on the other surface of the substrate 11. Examples of the radiator 15 include a metal plate having a high thermal conductivity, a heat sink, a refrigerant jacket, and the like, and these can be arbitrarily selected. An insulating layer (not shown) is provided between the radiator 15 and the substrate 11 in order to prevent a short circuit. The radiator 15 is attached to the substrate 11 by any attachment means such as screws.

  In the power module 10, an electrode pad 16 is provided on one surface side of the substrate 11. A terminal (not shown) on the upper surface of the semiconductor bare chip 13 and the electrode pad 16 are connected by an electrical connection member 17. At this time, the second diffusion part 122 and the electrical connection member 17 are not in contact with each other.

  The electrode pad 16 is a conductive foil having high conductivity. A wiring pattern of an electronic circuit is formed on one surface of the substrate 11 by this conductive foil, and the electrode pad 16 is a part thereof. Examples of the material of the electrode pad 16 include a metal material, and more specifically, copper and an alloy containing copper.

  The electrical connection member 17 is a conductor that electrically connects a terminal (not shown) of the semiconductor bare chip 13 and the electrode pad 16, and specifically, is a conductive wire or a conductive tape. The size of the electrical connection member 17 such as the diameter of the conductive wire, the width of the conductive tape, and the length thereof is appropriately designed according to the amount of current and the wiring pattern. As shown in FIG. 2, the electrical connection member 17 is connected by being laid from the semiconductor bare chip 13 side to the electrode pad 16 side by a connection method using wire bonding or a ribbon electric wire. Examples of the material of the electrical connection member 17 include a metal material, specifically, copper, aluminum, silver, gold, and the like.

  When the electrical connecting member 17 and the heat spreader 12 come into contact, an electrical short circuit occurs. Therefore, the second diffusion part 122 of the heat spreader 12 is provided so as not to contact the electrical connection member 17. In other words, the second diffusion part 122 is not provided at a location where the electrical connection member 17 crosses over the first diffusion part 121 of the heat spreader 12. For this reason, the electrical connection member 17 can be electrically connected from the semiconductor bare chip 13 side to the electrode pad 16 side without obstructing the connection method using wire bonding or ribbon electric wires. For example, when performing wire bonding, it is necessary to prevent the bonding head from coming into contact with the second diffusion portion 122, but it is not necessary to increase the height of the bonding wire.

  Next, the heat radiation effect of the power module 10 of the present embodiment will be described. The heat generated in the semiconductor bare chip 13 is mainly conducted to the first diffusion part 121 of the heat spreader 12. Since the first diffusion part 121 has a larger area than the semiconductor bare chip 13, the conducted heat is diffused in the first diffusion part 121. The diffused heat is further conducted to the radiator 15 via the thermal via 18 of the substrate 11, and the power module 10 is radiated.

  On the other hand, a part of the heat conducted to the first diffusion part 121 is conducted to the second diffusion part 122. The heat conducted to the second diffusion part 122 is conducted to the air through the sealing material 14 and is radiated. Since the second diffusion portion 122 is provided upright from the first diffusion portion 121, the thermal conductivity in the height direction and the direction toward the side surface of the sealing material 14 is higher than that of a conventional plate-shaped heat spreader. . For this reason, the heat dissipation of the power module 10 by the air cooling from the one surface side of the board | substrate 11 can be improved compared with the past.

  As described above, the power module 10 can dissipate heat by air cooling via the second diffusion part 122 and the sealing material 14 in addition to heat radiation by the conventional radiator 15. In other words, heat can be radiated on one side and the other side of the substrate 11.

  Thus, by providing the heat spreader 12 with the second diffusion portion 122, the surface area of the heat spreader 12 as a whole is increased as compared with the conventional case. For this reason, the diffusion amount of the heat generated in the semiconductor bare chip 13 is improved, and the heat dissipation of the power module 10 can be improved. Since the surface area of the heat spreader 12 as a whole can be increased without increasing the area of the first diffusion part 121, it is possible to meet the demand for downsizing of the power module.

  The power module 10 according to the first embodiment of the present invention has been described above, but the power module according to the present invention can be implemented in other forms.

  For example, when the diode-type semiconductor bare chip 23 such as FWD is mounted on the substrate 11 as in the power module 20 shown in FIG. 3, the heat spreader 22 may be used. The heat spreader 22 includes a first diffusion portion 221 formed in a plate shape, and a second diffusion portion that stands vertically from the first diffusion portion 221 in the opposite direction of the substrate 11 and is connected to three sides of the first diffusion portion 221. 222. The second diffusion part 222 may be formed by connecting a plurality of plate-like members, or may be formed as one member by extrusion molding or the like. Also in this case, the second diffusion part 222 and the electrical connection member 17 can be brought into non-contact with each other.

  Further, as in the power module 30 according to the second embodiment shown in FIG. 4, the second diffusion part 322 standing in the opposite direction of the substrate 11 from the first diffusion part 321 of the heat spreader 32 may be formed in a rod shape. . When wire bonding or the like is performed, the electrical connection member 17 may be located near the first diffusion portion 321 as shown in FIG. 4 due to the arrangement of the electrode pads 16. By forming the second diffusion part 322 and the electric connection member 17, the second diffusion part 322 and the electrical connection member 17 can be brought into non-contact with each other.

  Depending on the arrangement of the electrode pads 16, a heat spreader formed by appropriately combining plate-like or rod-like second diffusion portions 322 may be used. As a result, the degree of freedom with respect to the arrangement of the electrical connection member 17 is increased, and the positional relationship between the terminals of the semiconductor bare chip 13 and the electrode pads 16 on the substrate 11 can correspond to various patterns.

  Like the power module 40 according to the third embodiment shown in FIG. 5, a form in which a part of the second diffusion portion 122 of the heat spreader 12 is exposed may be used. Since the heat conductivity of the heat spreader 12 is higher than the heat conductivity of the sealing material 14, the heat dissipation efficiency from the exposed portion 123 to the air is higher than the heat dissipation efficiency from the sealing material 14 to the air. Since a part (exposed portion 123) of the second diffusion portion 122 is exposed from the sealing material 14, the heat diffused by the heat spreader 12 can be conducted to the air without passing through the sealing material 14. Thereby, the heat dissipation of the power module 40 can be improved.

  Like the heat spreader 12 a provided in the power module 50 shown in FIG. 6, the second diffusion part 122 a may be formed so as to stand obliquely from the first diffusion part 121. Compared with the heat spreader 12 provided in the power module 10 where the second diffusion part 122 stands vertically from the first diffusion part 121, the surface area can be further increased.

  As in the power module 60 shown in FIG. 7, the second diffusion part 122 b of the heat spreader 12 b may be provided with a flange, and the flange may be exposed from the sealing material 14 as an exposed part 123 b. Since the exposed portion 123b has a larger area than the exposed portion 123 of the heat spreader 12 provided in the power module 40, the heat dissipation of the power module 60 can be further improved.

  The power module of the present invention is not limited to the above embodiment. For example, the second spreader of the heat spreader may be provided over as wide a range as possible as long as a space for wire bonding can be secured so that the bonding head does not come into contact with the second spreader of the heat spreader. It is also possible to use a heat spreader in which a minimum required notch portion is formed in a second diffusion portion having a square shape standing up from the peripheral edge portion of the first diffusion portion.

  Alternatively, an inverter circuit can be formed by connecting a plurality of power semiconductors such as IGBT and FWD in parallel on the heat spreader.

  As described above, the power module according to the present invention is a technique described in the above embodiment according to various conditions such as the heat generation amount of the semiconductor bare chip mounted on the substrate, the wiring pattern of the electronic circuit including the electrode pads, and the performance of the radiator. It can be implemented as a power module including a heat spreader appropriately designed by combining the above.

  It should be noted that the present invention can be implemented in a mode in which various improvements, modifications, or variations are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Moreover, you may implement with the form which substituted any invention specific matter to the other technique within the range which the same effect | action or effect produces.

DESCRIPTION OF SYMBOLS 1, 11: Board | substrate 2, 12, 12a, 12b, 22, 32: Heat spreader 3, 13, 23: Semiconductor bare chip 4, 14: Sealing material 5, 15: Radiator 6, 16: Electrode pad 7, 17: Electricity Connection members 8, 18: Thermal vias 121, 221, 321: First diffusion parts 122, 122a, 122b, 222, 322: Second diffusion parts 123, 123b: Exposed parts 10, 20, 30, 40, 50, 60, 80: Power module

Claims (4)

A substrate having one side and the other side;
A heat spreader disposed on one side of the substrate;
A semiconductor bare chip mounted on the substrate via the heat spreader;
A sealing material for sealing the semiconductor bare chip mounted on the substrate;
A radiator provided on the other side of the substrate,
The heat spreader includes a plate-like first diffusion portion that is in thermal contact with each of the substrate and the semiconductor bare chip, and a second diffusion portion that stands up in the opposite direction of the substrate from the first diffusion portion. Power module. An electrode pad provided on one surface of the substrate;
An electrical connection member for electrically connecting the semiconductor bare chip and the electrode pad;
The power module according to claim 1, wherein the second diffusion portion is non-contact with the electrical connection member.   3. The power module according to claim 1, wherein the second diffusion portion has a plate shape or a rod shape. 4. The power module according to claim 1, wherein a part of the second diffusion portion is exposed from the sealing material. 5.

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