JP3829641B2 - Power semiconductor module - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a water cooling structure of a module having a power semiconductor element with a high calorific value, such as a power MOSFET, an IGBT (Insulated gate bipolar transistor).
[0002]
[Prior art]
FIG. 2, FIG. 3 and FIG. 4 show conventional power semiconductor modules used in a large capacity inverter that controls a high output motor such as a motor for a hybrid electric vehicle. FIG. 2 shows a so-called indirect cooling module in which a power semiconductor module 29 is fixed to a heat sink 27 with a thermal conductive grease 26. FIG. 3 shows a direct cooling module 32 in which the copper base 24 of FIG. 2 is used as the copper base 30 with fins 31 and the heat conductive grease 26 of FIG. FIG. 4 shows a direct cooling module in which the power semiconductor chip 10 is soldered to a heat sink 40 having a water channel 14.
[0003]
In FIG. 2, the power semiconductor chip 10 is bonded by solder 11 to an aluminum nitride substrate 23 composed of a copper plate 20, an aluminum nitride 21, and a backside copper plate 22 that are circuit patterns. Further, the aluminum nitride substrate 23 is bonded to the copper base 24 with solder 25. With such a structure, the power semiconductor module 29 is a so-called insulation module in which the power semiconductor chip 10 and the copper base 24 are electrically insulated. For example, when an insulating module is assembled as an inverter, it is not necessary to consider the electrical insulation between the module and the heat sink 27, so that it is easy to handle. The module is radiated by a heat sink 27 in which fins 29 are formed via an aluminum nitride substrate 23 and a copper base 24. This prior art has a water cooling structure in which the water channel 14 is constituted by the heat sink 27 and the water channel cover 15. In the case of this prior art, since it is water-cooled, heat transfer higher than that of air cooling is achieved, but the temperature rises at 26 parts of heat-conducting grease having a two-digit thermal conductivity lower than that of the metal member. Further, the temperature of the aluminum nitride substrate 23, which is a feature of the insulating module, also rises because it has a lower thermal conductivity than metal.
[0004]
In FIG. 3, the fins 31 are provided on the copper base 30 of the power module 32. The copper base 30 and the water channel cover 15 constitute a water channel 14, and a base direct cooling structure in which cooling water is directly applied to the copper base 30. In this structure, since the fins 31 are provided on the copper base 30 which is a flat plate in FIG. 2, it is necessary to consider that the fins 31 are not deformed in the solder bonding process of the aluminum nitride substrate 23. Furthermore, aluminum nitride substrates with high thermal resistance still exist.
[0005]
FIG. 4 shows the power semiconductor chip 10 attached to the aluminum heat sink 40 in which the low heat resistance is improved by removing the insulating substrate (aluminum nitride substrate) of the base direct cooling structure module shown in FIG. Are directly bonded with solder 11. That is, in FIG. 2 and FIG. 3, the heat sink and the chip are electrically insulated modules, whereas in this prior art, the heat sink is a non-insulated module that is not electrically insulated. This prior art has a structure in which the heat of the power semiconductor chip 10 is dissipated by the water-cooled heat sink 40 without inclusions other than the solder 11.
[0006]
[Problems to be solved by the invention]
The reason why the power semiconductor module is water-cooled is to reduce the thermal resistance Rth (j−w) from the semiconductor chip junction to the refrigerant. However, in the case of the prior art shown in FIGS. 2 and 3, since there is an insulating substrate 23 for insulating the power semiconductor chip 10 and the module bases 27 and 30, there is a limit to the reduction in thermal resistance.
[0007]
Since the structure of FIG. 4 is a non-insulating module, for example, when the power semiconductor chip 10 is an IGBT, the heat sink 40 serves as a collector electrode. That is, a high voltage is applied to the heat sink 40. Therefore, a sufficient insulation distance between adjacent heat sinks must be taken. Moreover, since a voltage is also applied to the cooling water, the insulation must be ensured by sufficiently increasing the purity of the cooling water. Further, when a voltage is applied to the cooling water, a leak current naturally flows though it is weak, and there is a concern that corrosion of the heat sink 40 is promoted by the leak current.
[0008]
An object of the present invention is to provide a power semiconductor module that does not require consideration for the purity of cooling water or consideration for an insulation distance, has excellent corrosion resistance, high reliability, and sufficiently low thermal resistance.
[0009]
[Means for Solving the Problems]
FIG. 1 shows a cross-sectional view of the power semiconductor module of the present invention. In the present invention, the power semiconductor module 16 indicates a portion above the insulating layer 13. In the power semiconductor module of the present invention, the power semiconductor chip 10 is bonded to the heat sink / collector electrode (in the case of IGBT) 12 with the solder 11, and the insulating layer 13 is provided on the opposite surface of the heat semiconductor chip 10 mounting surface of the heat sink 12. The facing surface and the water channel cover 15 form a water channel 14. With such a configuration, an insulating module in which the cooling water and the power semiconductor module 16 are insulated is obtained.
[0010]
The heat of the power semiconductor chip 10 is sufficiently diffused by the heat sink 12 which is thicker (~ 1 mm or more) than the conventional wiring pattern 20 (thickness: ~ 0.3 mm) of FIG. Therefore, the heat transfer area of the insulating layer 13 becomes sufficiently large, and the thermal resistance of the insulating layer 13 becomes small enough to be ignored. Furthermore, in the power semiconductor module of the present invention, since the insulating layer 13 at the interface between the cooling water and the heat sink 12 is made of a resin such as epoxy or glass such as phosphate glass, it also serves as a corrosion resistant coating.
[0011]
As shown in FIG. 5, the power semiconductor module of the present invention is provided with fins 52 on a heat sink 50 and an insulating layer 51 formed on the outside thereof. The water channel 14 is constituted by the water channel cover 15 and the heat sink 50, and the heat transfer area is increased by the fins 52. At the same time, the thermal resistance of the insulating layer 51 is greatly reduced, so that a further reduction in the thermal resistance can be realized.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0013]
Example 1
The present embodiment will be described with reference to FIG. FIG. 6 is a schematic cross-sectional view of a one-phase IGBT module on which one upper and lower arm is mounted. The voltage / current rating is 600V / 200A, and the chip sizes of the IGBT 60 and the freewheeling diode (FWD) 61 are approximately 10 mm and 7 mm, respectively. A fin 66 having a length 691 / width 695 / spacing 696 of 6 mm / 6 mm / 3 mm and four heat sinks 693 formed on a plate having a thickness 697 of 3 mm, eutectic solder 690 and IGBT 60 and FWD 61 chip are soldered. Glued. The heat sink 693 is made of tough pitch copper (C1100), and the surface is treated with electroless Ni plating (film thickness: about 6 μm). The plane dimension is 2 cm × 4 cm. Here, the unevenness of the heat sink 693 should be 0.1 mm or more, and more preferably 2 mm or more. Further, the surface of the heat sink 693 other than the chip mounting surface 694 is coated with bismuth glass (film thickness: 20 μm) whose main component is Bi ₂ O ₃ .
[0014]
The bismuth glass preferably has a thickness of less than 50 μm. In addition to bismuth glass, any glass having a melting point of 660 ° C. or lower and lower than the melting point of aluminum can be applied to this embodiment. The thickness of the solder 690 is approximately 0.1 mm, and the thickness of the Si chip is approximately 0.5 mm. The heat sink 693 on which each of the IGBT 60 and the FWD 61 is mounted is bonded with a silicone adhesive 64 to a so-called insert case 62 in which P, N, output, control terminal (not shown), and an N electrode 67 are integrally formed. The The material of the insert case 62 is polyphenylene sulfide (PPS). The external dimensions are 9 cm (L) × 3.5 cm (W) × 3 cm (H). A printed circuit board (PCB) 69 is adhered to the insert case 62 with a silicone adhesive 64 for the control circuit. Electrical wiring is performed with aluminum wires 68 that are ultrasonic wire bonded. The wire diameter is 0.3 mmφ and 24 wires are connected per chip in consideration of current capacity. Sealing is performed with an epoxy resin 63. In the IGBT module, sealing with silicone gel is generally used, but in this embodiment, since sealing is performed only with a so-called hard resin, the reliability of waterproofing is further improved as compared with the case of the adhesive 64 alone.
[0015]
When all the terminals of the IGBT module of this embodiment are short-circuited, the module is placed on a copper plate, and the insulation withstand voltage between the copper plate and all the short-circuited terminals is measured, it is 4 KV, which is sufficient as an IGBT module with an element withstand voltage of 600 V Value.
[0016]
Cooling is performed by adhering the case bottom surface 698 of the IGBT module of this embodiment to the water channel cover and applying cooling water to the heat sink 693. FIG. 7 shows a cross-sectional structure including the cooling system. The IGBT module 74 is basically the same as the structure of FIG. 6, and in this embodiment, a copper plate (C1100) 71 is insert-molded on the entire bottom surface of the insert case 75. The water channel cover 72 is made of aluminum die casting. The cooling water is sealed by the copper plate 71 and the bottom surface of the case 75 and the water channel cover 72 are screwed together with the gasket 70.
[0017]
Cooling water was passed through the water channel 73 at a flow rate of 3 m / s, and the thermal resistance of the IGBT 60 was measured. As a result, Rth (jw) = 0.09 ° C./W. In the case of the prior art of FIG. 2, Rth (j−w) = 0.32 ° C./W 2 at the same flow rate of 3 m / s, and the thermal resistance could be reduced by 70% or more. Further, Rth (j−w) when the glass layer 65 is not present is 0.08 ° C./W, and the thermal resistance is increased only by about 10% as compared with the case of the prior art of FIG. It is easy to implement as.
[0018]
The reason why the heat sink 693 is made of copper (C1100) is that heat resistance reduction is given top priority, and aluminum may be used in consideration of manufacturing costs. When the heat sink 693 was made of aluminum (JIS A 1100) (the shape was the same), the thermal resistance was measured in the same manner. As a result, Rth (j−w) = 0.11 ° C./W 2. Since aluminum has a lower thermal conductivity than copper, the thermal resistance is somewhat increased, but is lower than that of the prior art structure of FIG. In the case of an aluminum heat sink, since the linear expansion coefficient is larger than that of copper, the distortion of the under-chip solder 690 is larger than that of copper. Therefore, in the case of an aluminum heat sink, the solder 690 is made as thick as 0.2 mm.
[0019]
The material of the heat sink 693 may be oxygen-free copper (C1020), aluminum die casting, or the like, and may be selected in consideration of manufacturing cost and thermal resistance.
[0020]
(Example 2)
This embodiment will be described using the schematic cross-sectional structure diagram of FIG. 8. This embodiment differs from the embodiment shown in FIGS. 6 and 7 in that the shape of the heat sink 82 and the insert case 81 associated therewith are different. The other parts are exactly the same. The fins 66 are formed on the heat sink 693 in FIG. 6, but in the present embodiment, the flat heat sink 82 has the same material and plating specifications. The surface of the heat sink 82 is measured between the peaks and valleys of the unevenness, and the average value of the five points from the largest is 0.1 mm or less, and it is more preferable that the unevenness is 0.05 mm or less. After the IGBT and FWD chips are solder bonded to the heat sink 82, the heat sink is bonded to the insert case 81 with a silicone adhesive. Insulation is performed by adhering a heat conductive resin sheet 80 to the entire module bottom surface. The heat conductive resin sheet 80 is obtained by kneading an alumina filler with an epoxy resin, and has a film thickness of 0.1 mm and a heat conductivity of 1.6 W / m · ° C. Adhesion is performed by so-called thermocompression bonding, in which the material is heated to 150 ° C. and pressurized. In the structure of this embodiment, the module bottom surface is covered with a resin sheet 80. In addition, the thickness of the heat conductive resin sheet should just be thinner than 0.3 mm, Preferably it is 0.2 mm or less.
[0021]
When this module was mounted on a copper plate and the dielectric breakdown voltage between all terminals and the copper plate was measured, it was 6 KV and a sufficient breakdown voltage was confirmed. Further, as in Example 1, when cooling water was allowed to flow under the heat conductive resin sheet 80 at a flow rate of 3 m / s and the thermal resistance of the IGBT chip 60 was measured, Rth (j−w) = 0.2 ° C./W there were. In this embodiment, a low thermal resistance was realized as compared with the conventional structure of FIG.
[0022]
Example 3
FIG. 9 shows a schematic cross-sectional structure of this example. FIG. 9 shows a one-arm module on which an IGBT chip 60, an FWD chip 61, and a chip resistor 94 are mounted. An IGBT chip 60, an FWD chip 61, and a chip resistor 94 are bonded to each other by a eutectic solder 690 on a Ni-plated copper (C1020) lead frame 91 having a size including outer leads of about 7 cm × 6 cm and a thickness of 1 mm. . On the back surface of the lead frame 91 to which the IGBT chip 60 and the FWD chip 61 are soldered, the same low melting point glass 90 as that of the first embodiment is coated with a film thickness of 20 μm. Each chip and the lead frame 91 are connected by ultrasonic bonding of an aluminum wire 68. The chip resistor 94 is connected to the gate of the IGBT chip 60, and its purpose is to prevent oscillation of the IGBTs 60 connected in parallel. The lead frame 91 is epoxy molded with epoxy resin so that the back surface is exposed. Thereafter, the portion 93 is again molded with epoxy resin so that the back glass coated lead frame 91 on which the IGBT chip 60 and the FWD chip 61 are mounted is exposed. The transfer mold resin 93 has an overhang 97 of about 1.5 mm on the back surface of the back glass-coated lead frame 91. This is because the lead frame 91 is caulked with the transfer mold resin 93 to ensure waterproofing. The height of the package is about 6 mm.
[0023]
FIG. 12 is a lead frame shape diagram before sealing with epoxy resin. FIG. 9 described above shows the AA cross section in the figure in a state where the resin is sealed and attached to the cooling device. The IGBT 60 and FWD 61 are bonded to the collector pattern 120 of the lead frame, and the emitter is connected to the emitter pattern 122 by an aluminum wire 68. Aluminum wires other than the auxiliary emitter wire 123 and the gate wire 124 are drawn only on a pair of IGBTs and FWDs for simplification. The aforementioned chip resistor 94 is bonded to the gate pattern 126, and the auxiliary emitter wire 123 is connected to the pattern 125. Holes 121 at the four corners of the lead frame are module mounting holes. The heat of the IGBT 60 and the FWD 61 spreads over the entire collector pattern 120 having a size of about 5 cm × 2 cm and can efficiently dissipate heat, thereby realizing a low thermal resistance.
[0024]
This package was bonded to the circuit case 96 to form a water channel 95 with the water channel cover 15. The thickness of the water channel is 2 mm. When a water pressure of about 2 kg / cm ² was applied to the water channel 95, no penetration of cooling water into the package was observed, and it was found that there was no concern about cooling water penetration at a practical water pressure. Further, when the thermal resistance of the IGBT 60 was measured at a flow rate of 3 m / s as before, Rth (j−w) = 0.1 ° C./W 2 and a sufficiently small thermal resistance could be realized. Also, the withstand voltage was a sufficient value as in Examples 1 and 2.
[0025]
Example 4
FIG. 10 shows a schematic cross-sectional structure of this example. In this example, transfer mold resin 93 was used for insulation. In this embodiment, an IGBT 60, FWD 61, and chip resistor 94 are mounted on a lead frame 91 that is not coated on the back surface at all, and the back surface of the lead frame is exposed and transfer molded with a resin 92. The lead frame 91, solder 690, and the like are the same as those in the third embodiment. Insulation is performed by forming an insulating layer 101 made of a transfer mold resin, the entire back surface of which is sealed with a transfer mold resin 93 as shown in the figure. In FIG. 10, the thickness of the insulating layer 101 made of transfer mold resin is expressed with emphasis, and the actual thickness is about 0.2 mm. In this structure, the sealing resin and the insulating resin are used in common to reduce the manufacturing cost, and at the same time, the waterproofness of the package becomes more complete.
[0026]
When the water channel 95 is formed by this package, the circuit case 96, and the water channel cover 15 and the thermal resistance is measured, Rth (j−w) = 0.26 ° C./W (flow rate: 3 m / s). Lower thermal resistance than prior art structures.
[0027]
(Example 5)
FIG. 11 shows a schematic diagram of a cross-sectional structure of this example. This embodiment is the same as FIG. 9 except that the structure of FIG. 9 is provided with a corrosion-resistant coating layer 110 for achieving corrosion resistance. The corrosion resistant coating layer 110 is a copper foil (C1020) having a thickness of 0.1 mm in this embodiment, and in the case of an ethylene glycol antifreeze generally used as cooling water, the coating has been operated for 15 years. The elution of copper at the time is predicted to be negligibly small, and sufficient corrosion resistance can be expected. The thermal resistance was the same value as in FIG. 9 because the resistance of copper was so small that it could be ignored.
[0028]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the consideration with respect to a cooling water purity and the consideration with respect to an insulation distance are unnecessary, it is excellent in corrosion resistance, it is highly reliable, and a power semiconductor module with sufficient low thermal resistance can be provided.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a power module of the present invention.
FIG. 2 is a cross-sectional view of a conventional power module.
FIG. 3 is a cross-sectional view of another prior art power module.
FIG. 4 is a cross-sectional view of yet another prior art power module.
FIG. 5 is a cross-sectional view of the power module of the present invention.
FIG. 6 is a cross-sectional view of the power module according to the first embodiment.
7 is a schematic diagram when a water channel is configured by the module of FIG. 6;
FIG. 8 is a cross-sectional view of a power module according to a second embodiment.
FIG. 9 is a cross-sectional view of a power module according to a third embodiment.
FIG. 10 is a cross-sectional view of a power module according to a fourth embodiment.
FIG. 11 is a cross-sectional view of a power module according to a fifth embodiment.
12 is a schematic plan view of a lead frame of Example 3. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Power semiconductor chip, 11, 25,690 ... Solder, 12 ... Heat sink and collector or drain or cathode electrode, 13 ... Insulating layer, 14, 73, 95 ... Waterway, 15,72 ... Waterway cover, 16 , 29, 32 ... power semiconductor module, 20 ... copper plate (circuit pattern), 21 ... aluminum nitride, 22 ... copper plate, 23 ... aluminum nitride substrate, 24 ... copper base, 26 ... thermal grease, 27, 30, 40, 50 , 82, 693 ... heat sink, 29, 31, 52, 66 ... fin, 51, 65, 90 ... low melting glass layer, 60 ... IGBT chip, 61 ... FWD chip, 62, 75, 81 ... insert case, 63 ... epoxy Resin, 64 ... Silicone adhesive, 67 ... N electrode, 68 ... Aluminum wire, 69 ... Printed circuit board, 70 ... Gasket 71 ... Copper plate for module fastening, 74 ... IGBT module, 76 ... Heat sink / case boundary layer, 80 ... High thermal conductive resin sheet, 91 ... Lead frame, 92, 93 ... Transfer mold resin, 94 ... Chip resistor, 96 ... Circuit case, 97 ... Overhang, 101 ... Insulating layer by transfer mold resin, 110 ... Corrosion-resistant coating layer, 120 ... Lead frame collector pattern, 121 ... Module mounting hole, 122 ... Lead frame emitter pattern, 123 ... Auxiliary emitter aluminum wire, 124 ... Gate aluminum wire, 125 ... lead frame auxiliary emitter pattern, 126 ... lead frame gate pattern, 691 ... fin length, 694 ... heat sink chip mounting surface, 695 ... fin width, 696 ... fin spacing 697 ... heat sink thickness, 698 ... bottom of the case.

Claims (13)

A power semiconductor chip;
A metal body mounted with the power semiconductor chip and diffusing heat of the power semiconductor chip;
Water cooling means for cooling the power semiconductor chip,
The power semiconductor chip is electrically bonded to one surface of the metal body by an adhesive means,
An insulating layer is coated on the other surface of the metal body,
The insulating layer is in contact with the cooling water of the water cooling means,
The insulating layer is made of low melting glass or resin having a melting point of 660 ° C. or lower, or made by modifying the metal body by introducing oxygen or nitrogen atoms into the surface of the metal body. A power semiconductor module characterized by comprising: The power semiconductor module according to claim 1,
The power semiconductor module, wherein the low melting point glass is bismuth oxide glass. The power semiconductor module according to claim 1 or 2,
The power semiconductor module according to claim 1, wherein the insulating layer made of the low-melting glass has a thickness of 50 μm or less. The power semiconductor module according to claim 1,
The power semiconductor module, wherein the resin is a mixture of an epoxy resin and an alumina filler. The power semiconductor module according to claim 1 or 4,
The power semiconductor module, wherein the insulating layer made of the resin has a thickness of 300 μm or less. The power semiconductor module according to any one of claims 1, 4 and 5,
The power semiconductor module, wherein the resin is a resin that seals the power semiconductor chip. A power semiconductor chip;
A metal body mounted with the power semiconductor chip and diffusing heat of the power semiconductor chip;
Wiring electrically connected to the power semiconductor chip;
Water cooling means for cooling the power semiconductor chip,
The power semiconductor chip is electrically bonded to one surface of the metal body by an adhesive means,
An insulating layer is coated on the other surface of the metal body,
The insulating layer is in contact with the cooling water of the water cooling means,
The power semiconductor module, wherein the power semiconductor chip, the metal body, and the wiring are sealed with a hard resin. A power semiconductor chip;
A metal body mounted with the power semiconductor chip and diffusing heat of the power semiconductor chip;
Water cooling means for cooling the power semiconductor chip,
The metal body is made of copper or aluminum or an alloy thereof,
The power semiconductor chip is electrically bonded to one surface of the metal body by an adhesive means,
The other surface of the metal body has an unevenness of 0.1 mm or more on the surface,
The surface of the other surface of the metal body including the irregularities is coated with an insulating layer,
The power semiconductor module, wherein the insulating layer is in contact with cooling water of the water cooling means. A power semiconductor chip;
A metal plate mounted with the power semiconductor chip and diffusing heat of the power semiconductor chip;
A resin case for sealing the power semiconductor chip and the metal plate;
Water cooling means for cooling the power semiconductor chip,
The power semiconductor chip is electrically bonded to the metal plate by bonding means,
The metal plate is bonded to the resin case such that the surface facing the mounting surface of the power semiconductor chip is exposed on the bottom surface of the resin case,
The entire bottom surface of the resin case where the metal plate is exposed is covered with an integral insulating layer,
The insulating layer is in contact with the cooling water of the water cooling means,
The power semiconductor module, wherein the insulating layer is made of a resin mainly composed of an epoxy resin. A power semiconductor chip;
A metal body mounted with the power semiconductor chip and diffusing heat of the power semiconductor chip;
Water cooling means for cooling the power semiconductor chip,
The power semiconductor chip is electrically bonded to the metal body by bonding means,
The power semiconductor chip is electrically bonded to one surface of the metal body by an adhesive means,
An insulating layer is coated on the other surface of the metal body,
A thin film made of a material different from the insulating layer is fixed to the surface of the insulating layer,
The power semiconductor module, wherein the thin film is in contact with cooling water of the water cooling means. The power semiconductor module according to claim 10,
The power semiconductor module, wherein the thin film has a thickness of 0.1 mm or less. A power semiconductor chip;
A metal body mounted with the power semiconductor chip and diffusing heat of the power semiconductor chip;
A resin case for sealing the power semiconductor chip and the metal body;
Water cooling means for cooling the power semiconductor chip,
The power semiconductor chip is electrically bonded to the metal body by bonding means,
An insulating layer is coated on the opposite surface of the adhesion surface of the metal body with the power semiconductor chip,
The insulating layer has a thickness of 0.1 mm or less, and a thin film made of a material different from the insulating layer is bonded to the insulating layer.
The power semiconductor module, wherein the thin film is in contact with cooling water of the water cooling means. The power semiconductor module according to claim 10 or 12,
The power semiconductor module, wherein the thin film is made of copper or aluminum metal.

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