JP2007324351A - Pressure-contact semiconductor module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve reliability in cooling/heating cycles and resistance to pressure, while enhancing cooling efficiency. <P>SOLUTION: A cooling fin 17 is formed into a columnar structure whose cross section has a perfect_circle shape with a diameter D, and whose column length is 5 mm. The coolings fin are arranged in a grid form at a fin pitch of 1.25D, 1.5D, 2D or 3D, in a channel 20 circulating cooling water of a cooler 16 so as to cool an IGBT 12 and a diode 13 by heat exchanging between the cooling fins 17 and the cooling water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure contact type semiconductor module in which a semiconductor element such as an exothermic IGBT is mounted by pressure contact with an external pressure device.

  Conventionally, as a pressure contact type semiconductor device in which a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) is mounted by pressure contact with an external pressure device, heat transfer that also serves as a conductive surface as a cooling member on both sides of the semiconductor element A semiconductor device having a surface is known. In this semiconductor device, one of the heat transfer surfaces is laminated to a flat semiconductor element, and the other is laminated to a flat semiconductor element or an insulating member that is a part of a support. They are combined (see, for example, Patent Document 1). The laminated cooling members are immersed in a low-boiling organic refrigerant such as Freon and cooled by boiling of the refrigerant.

  In recent years, environmental issues have become more important and the use of Freon, an environmentally hazardous substance (ozone-depleting substance), has been regulated, and the use of pressure-contact type semiconductor devices immersed in refrigerant has also been reviewed. It tends to be. For this reason, as a pressure-contact type semiconductor device, a conversion from a method of immersing in a refrigerant to a method of cooling using a heat pipe has been attempted (for example, see Patent Document 2). In the conventional method of cooling using a heat pipe, waste heat is performed using the heat transporting power of the heat pipe.

  On the other hand, semiconductor devices including power modules are widely used in automobiles. When mounting a semiconductor device on a vehicle, the semiconductor device is generally mounted in an engine room. For example, in a THS (Toyota Hybrid System) having a large output, the mounting position is generally inside an inverter case arranged side by side next to the engine.

However, in the future, by reducing the size of the power module, mounting it near the motor or mounting it in the motor / housing, etc., we will move toward reducing costs while reducing wire harnesses, saving space, etc. Can be considered. In other words, even in the engine room, the mounting position of the semiconductor device has changed from a position close to the radiator, which is the most suitable position for exhausting heat and being close to the motor, to a position farther from the radiator than the motor. It is possible to come. As described above, when the mounting position of the semiconductor device is close to the motor, a large number of parts are arranged in addition to the engine body on the way, so that the path has a winding structure. Therefore, when trying to mount a vehicle using a winding path, it is necessary to bend the heat pipe.
Japanese Patent Publication No. 51-47576 Japanese Patent Publication No. 7-27996

  It is known that the heat pipe can be bent freely, but the heat transport force decreases with the number of bendings. The heat transport capacity of the heat pipe depends on the shape of the working fluid enclosed in the inside and the wick inside (circulating the working fluid using capillarity using heat pipe grooves or metal fibers) and the diameter of the heat pipe. Dependent. However, for the hydraulic fluid, an appropriate system (water or ammonia near room temperature, naphthalene at high temperature, etc.) should be selected for the intended use temperature, and is therefore determined by its purpose and environmental temperature. There is little room for selection, and wicks, etc., that have been well studied industrially are currently used, and there is little room for change in consideration of performance and cost.

Therefore, in order to compensate for the decrease in heat transport force accompanying bending, the diameter of the heat pipe must be increased, but this is not desirable because it goes against space saving and cost reduction. Moreover, in order for the hydraulic fluid to recirculate in the wick, not only the capillary pressure (interfacial tension) but also the influence of gravity is exerted. Therefore, it is generally desirable that the heat generating source is below the cooling section.
However, assuming that the bending of the heat pipe in the case of being mounted on the vehicle as described above is complicated, it is not always possible to secure a structure in which the vertical relationship is maintained at the bent portion of the route in the middle, and the heat transport force There is a possibility of further increasing the decline.

  On the other hand, in the water-cooled structure, there is a possibility that pressure loss may occur at the bent part, but by increasing the pump capacity, the amount corresponding to the pressure loss can be reduced without increasing the diameter of the cooling water pipe. It is possible to compensate.

  Therefore, when it is configured as a water-cooled pressure-contact type semiconductor module, it is possible to incorporate the high reliability and parts replacement characteristic unique to the pressure-contact type structure, which greatly reduces the space and cost when mounted on an automobile. Improvement is expected.

  In addition, in a pressure-contact type semiconductor module, it is important that the cooling structure is a structure that can withstand the pressure during pressure contact, and an improvement in pressure resistance performance is also required for the structure.

  The present invention has been made in view of the above, and an object thereof is to provide a pressure contact type semiconductor module having high cooling efficiency and excellent reliability and pressure resistance of a thermal cycle, and to achieve the object. To do.

In order to achieve the above object, a pressure contact type semiconductor module according to the present invention includes a semiconductor element mounted on a wiring metal plate by pressure contact, the semiconductor element and the semiconductor element arranged, and the semiconductor element A metal plate for wiring for supplying power to the substrate and a heat conductive fin having a columnar structure satisfying any of the following conditions (1) to (3), and at least the semiconductor element is cooled by heat exchange with the heat conductive fin: A cooler, and an insulating member that is disposed between the wiring metal plate and the cooler and electrically insulates the semiconductor element and the cooler.
"conditions"
(1) 0.1 mm ≦ maximum diameter D ≦ 1.0 mm and D ≦ fin pitch S ≦ 1.25D
(2) 0.2 mm ≦ maximum diameter D ≦ 0.5 mm and 1.25D <fin pitch S ≦ 1.5D
(3) 0.2 mm ≦ maximum diameter D <0.3 mm and 1.5 D <fin pitch S ≦ 2.0 D

  Here, the maximum diameter D is the maximum length of a cross section perpendicular to the length direction of the pillars of the fins of the columnar structure (for example, in the case of a cylindrical structure with a perfectly circular section, the diameter of the circular section, In the case of a prismatic structure such as a triangular column having a regular triangular section or a square column having a square section, the maximum side length or diagonal length in each case. The fin pitch S is the shortest distance between the center line and the center line passing through the center of the cross section of each fin of the columnar structure with the length direction of the column as a perpendicular.

In the pressure-contact type semiconductor module of the present invention, the fin diameter (for example, the diameter for a cylinder, the maximum diameter for an elliptical cylinder) and the arrangement (fins of fins) shown in the above conditions (1) to (3) are used as fins for heat exchange. By providing columnar-structured heat conduction fins that satisfy the arrangement interval), the fins are made finer, for example, a flow path for circulating the refrigerant, a circulation ease that can be circulated with a small power, and heat transfer are enhanced. The heat exchange efficiency of the semiconductor device can be kept high, and the cooling capacity of the semiconductor element can be improved. For example, even when the flow rate of the refrigerant is small and heat exchange is difficult, cooling can be performed with high efficiency and the reliability of the cooling cycle can be improved. Further, since it is configured in a columnar structure that satisfies the fin diameter and arrangement (arrangement interval) of the above conditions, it also has a pressure resistance performance that can suppress deformation due to external pressure when the semiconductor element is pressed from outside.
Moreover, in the press-contact type semiconductor module of the present invention, the number of parts can be reduced due to the configuration.

  In addition, since the pressure contact type semiconductor module of the present invention is a semiconductor element mounted with pressure applied by applying external pressure, the linear expansion of the module member in contact with the semiconductor element including the electrode and the linear expansion of the semiconductor element This difference can be mitigated by slipping, and is excellent in reliability in the thermal cycle.

  In the press-contact type semiconductor module of the present invention, the cooler is configured by providing a hollow portion through which a refrigerant flows, and heat conduction fins are provided in the hollow portion to exchange heat with the refrigerant flowing through the hollow portion. In addition, the shape of the cooler can be maintained.

  By providing heat conductive fins with columnar structures that satisfy the fin diameter and arrangement of the above conditions in the hollow part of the cooler, the refrigerant can be circulated and circulated satisfactorily even with small power, and the semiconductor element can be cooled with high efficiency. be able to. Further, it is possible to prevent pressure deformation due to the press-contact of the hollow portion shape, and thus the module shape.

  The heat conductive fins are preferably configured in a cylindrical structure and / or a prismatic structure. The cylindrical structure includes a perfect circle and an ellipse, and the prismatic structure includes a polygonal column such as a triangular column, a quadrangular column, and a hexagonal column. If the heat conducting fins are formed in a cylindrical or prismatic structure, it is easy to manufacture, and while maintaining high heat exchange efficiency (that is, cooling efficiency of the semiconductor element), it is possible to secure a high pressure strength against the external pressure of the module. it can.

  In addition, the heat conduction fin has a length in the column length direction (column length direction) in the range of 0.1 to 20 mm (more preferably in the range of 0.3 to 10 mm) in terms of fin efficiency with respect to the cooling capacity. It is preferable to do. Especially preferably, it is 2D-4D.

The insulating member constituting the pressure contact type semiconductor module of the present invention has a high thermal conductivity and a small coefficient of linear expansion. Specifically, the coefficient of linear expansion is 3 × 10 ⁻⁶ / K to 1 × 10 ⁻⁵ / K, More preferably, it can be formed using ceramics of 3 × 10 ⁻⁶ / K to 7 × 10 ⁻⁶ / K. When this ceramic is used, the coefficient of thermal expansion between the semiconductor element that generates heat can be reduced, and the heat transfer efficiency can be improved and thermal deformation can be prevented. This is effective in suppressing warpage and can improve the reliability of the module.

  Among the ceramics, it is preferable to use one or two or more kinds selected from aluminum nitride, aluminum oxide, silicone nitride, silicone oxide, beryllium oxide, and silicone carbide.

The wiring metal plate constituting the pressure contact type semiconductor module of the present invention is made of a metal having a thermal conductivity of 17 W / m · K or more and a specific resistance of 1 × 10 ⁻⁵ Ω · cm or less. It is preferred that The wiring board on which the semiconductor element is disposed is likely to rise in temperature directly due to the heat generated by the semiconductor element, but since heat transfer efficiency and electrical conductivity can be ensured, the cooling efficiency of the semiconductor element is improved and the warp due to thermal stress At the same time, it is effective in that the operation performance of the element can be kept good.

  Among the above metals, the wiring metal plate is preferably configured using at least one selected from copper, aluminum, tungsten, and molybdenum.

  According to the present invention, it is possible to provide a pressure contact type semiconductor module that has high cooling efficiency and is excellent in the reliability and pressure resistance of a cooling cycle.

  Hereinafter, embodiments of the pressure contact type semiconductor module of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments.

  The pressure contact type semiconductor module according to the present embodiment is provided with fins having a cylindrical structure at a predetermined interval on the side opposite to the side where the elements of the insulating film are provided, and by flowing cooling water to exchange heat with the fins. It is configured to be capable of cooling.

  As shown in FIG. 1, the semiconductor module of this embodiment includes a Cu wiring board 11 that is a wiring metal plate, IGBTs 12 and diodes 13 that are semiconductor elements placed in pressure contact with the Cu wiring board 11, Cu A green sheet 14 that is an insulating film (insulating member) that is in contact with the side of the wiring board 11 where the semiconductor element is not disposed, and a cooler 16 that is formed on the side of the green sheet 14 that does not contact the Cu wiring board 11. And.

  The Cu wiring board 11 is made of a copper plate having a length of 30 mm, a width of 15 mm and a thickness of 0.3 mm. The IGBT 12 and the diode 13 (semiconductor element) are pressed against the surface of the copper plate, and are electrically connected to an external power source. The diode 13 can be operated by supplying a current.

  The wiring metal plate can be appropriately selected and configured from an electrically conductive metal material according to the purpose and the like, and includes, for example, aluminum, tungsten, molybdenum, copper and tungsten or molybdenum in addition to the copper plate. A composite material or the like can be used.

Preferably, it is a metal material having a thermal conductivity of 17 W / m · K or more, ensuring heat transfer efficiency, increasing the cooling efficiency of the IGBT 12 and the diode 13, and avoiding warping due to thermal stress, such as copper, aluminum, tungsten And molybdenum are preferred. In addition, a metal material having a specific resistance of 1 × 10 ⁻⁵ Ω · cm or less is preferable, and copper, aluminum, tungsten, and molybdenum are also used from the viewpoint of ensuring thermal conductivity and electrical conductivity and maintaining the operation performance of the element. Are more preferable, and copper and aluminum are particularly preferable.

  Although there is no restriction | limiting in particular as board | plate thickness of Cu wiring board, Usually, it is about 0.1-0.5 mm, and 0.2-0.4 mm is a preferable range at the point of wiring resistance and a thermal stress. In addition, what is necessary is just to select suitably about sizes other than the thickness of Cu wiring board according to the objective.

  On this Cu wiring board 11, as shown in FIG. 1, one IGBT and one diode are provided, and a unit which is a minimum unit necessary for forming an inverter is configured.

A commercially available IGBT and diode can be appropriately selected and used.
Further, for example, in the case of a three-phase inverter used for a hybrid vehicle or the like, as shown in FIG. 4, the unit is composed of three units (arms) in series (or multiples thereof) in parallel. .

The green sheet 14 is an insulating film having an insulating property of a specific resistance of 1 × 10 ¹² Ω · cm or more after firing, and is configured to have a size of length 35 mm × width 20 mm × thickness 0.6 mm. By this green sheet, the Cu wiring board 11 provided with the IGBT and the diode and the cooler 16 are electrically insulated.

  The thickness of the green sheet 14 can be selected in the range of 0.3 to 1.0 mm in consideration of the material, insulation performance, strength, and the like.

The green sheet 14 is obtained by mixing and kneading an aluminum nitride powder, an organic binder such as polyvinyl butyral, a plasticizer such as dibutyl phthalate, and an organic solvent such as toluene, and the obtained slurry is uniformly mixed with a doctor blade. The sheet is formed so as to have a thickness and the sheet is formed to a thickness of 0.635 mm after firing, and then the sheet is cut and die-cut such as a press is performed using a mold. Can be formed into a sheet shape.
In addition, since a green sheet shrink | contracts 10 to 20% by drying, degreasing, and baking, it is desirable to form thicker than desired thickness beforehand.

  The green sheet 14 of the present embodiment is a green sheet previously formed into a sheet shape as described above, first heated at a temperature of 900 ° C. or less, dried and degreased, and subsequently in a temperature range of 1600 to 1900 ° C. It was produced by baking for 5 hours. Thereafter, the surface is oxidized in an oxygen atmosphere at a temperature of 1200 ° C. or lower to form an aluminum oxide film.

  For the green sheet (insulating member), in addition to the above aluminum nitride, it can be suitably selected from ceramic materials having high thermal conductivity and a small linear expansion coefficient. As the ceramic material, in addition to aluminum nitride, for example, aluminum oxide, silicone nitride, silicone oxide, beryllium oxide, silicone carbide and the like can be used, and one or more kinds can be selected and used depending on the purpose and the like. .

  As shown in FIG. 1, the green sheet 14 and the cooling fin 17 are interposed between the green sheet 14 and a cooling fin 17 described later on the element non-formation surface side of the green sheet 14 that does not contact the Cu wiring board 11. Are provided, or a correction metal plate 15 is provided to balance the linear expansion coefficient (as a symmetry plane of the Cu wiring board).

  The correction metal plate 15 is made of a copper plate having a length of 35 mm, a width of 20 mm, and a thickness of 0.3 mm. Further, the correction metal plate can be formed using a metal plate having the same coefficient of linear expansion as the metal plate for wiring (here, Cu wiring plate) in addition to the copper plate.

  The cooler 16 has a flow path 20 through which cooling water for cooling the IGBT and the diode by heat exchange flows on the side of the correction metal plate 15 that does not contact the green sheet 14, and the correction metal plate 15 in the flow path 20. And a plurality of cooling fins 17 arranged in a grid pattern at right angles (90 °) to the surface of the substrate. You may make it arrange | position at random.

  The arrangement angle of the cooling fin 17 with respect to the surface of the correction metal plate does not necessarily need to be 90 °, and may be selected according to the fin shape, flow rate, and other purposes, but can withstand the pressure (stress) at the time of press contact. From the viewpoint of obtaining the pressure resistance to be obtained, it is preferable that the angle formed between the joint surface of the cooling fin such as the correction metal plate and the length direction of the column of the cooling fin is in the range of 90 ° ± 2 °.

The flow path 20 has a frame 18 formed in an endless rectangular shape consisting of four surfaces of 35 mm in length and 20 mm in width using a copper plate having a thickness of 5 mm so as to follow the outer periphery of the correction metal plate 15. In addition, the copper plate 19 having a thickness of 1.0 mm is disposed and fixed on the surface opposite to the bonding surface side via a packing.
The frame that forms the flow path may be formed by forming a predetermined size using a heat-resistant resin material. As the heat-resistant resin material, for example, a thermoplastic resin such as polyphenylene sulfide can be used.

  As shown in FIG. 1, taper screw joints are attached to the two opposite surfaces of the frame 18, respectively, and an inlet 21 for supplying cooling water to the inside and heat-cooled and warmed cooling. An outlet 22 for discharging water to the outside is formed, and the cooling water supplied from the inlet 21 flows through the passage and is discharged to the outside from the outlet 22 to exchange heat with the cooling water. Thus, the IGBT and the diode can be cooled.

  The cooling fin 17 is formed by aligning a copper wire having a circular cross section so as to have a length of 5 mm, and as shown in FIG. 8 mm (2 mm, 0.3 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 5 mm) were produced; see Table 1 below) and formed into a cylindrical structure with a column length L of 5 mm. As shown in FIG. 3, the fin pitch S is n times the diameter D (nD; 1.25 times (1.25D) in this embodiment) on the surface of the correction metal plate 15 as shown in FIG. Four types of 5 times (1.5D), 2 times (2D), and 3 times (3D) were prepared (see Table 1 below), and arranged at a pitch (Sn).

About the diameter D of a cooling fin, the range of 0.1-1.0 mm is suitable, and it can select so that either of the said conditions (1)-(3) may be satisfy | filled. Preferably, it is the range of 0.2-0.5 mm.
Moreover, 0.1-20 mm is preferable and, as for the length (column length) of the column of a cooling fin, 0.2-10 mm (further 0.3-10 mm) is more preferable. Especially preferably, it is 2D-4D.
Further, the fin pitch S is preferably 1.5 D or less, and more preferably 1.25 D or less. The lower limit value of the fin pitch S is D.
Among the above conditions (1) to (3), it is preferable that the condition (1) or the condition (2) or the condition (1) is satisfied.

  The cooling fin 17 is applied by applying a brazing material (for example, silver brazing) or the like to the cut surface (and / or the correction metal plate 15 and / or the copper plate 19) of each cooling fin, and brazing the cooling fin. It is possible to form by cutting the cut surface provided with etc. into contact with the correction metal plate 15 and the copper plate 19 and joining by brazing in a furnace having a temperature of 700 ° C. or more in an inert atmosphere.

The cooling fin has a cylindrical structure with a perfect cross section as in this embodiment, and the cross-sectional shape is (i) an ellipse, (ii) an equilateral triangle (see FIG. 2- (c)), or an isosceles triangle. In addition, a triangular shape such as a right triangle, a square (see FIG. 2B), a rectangle such as a rectangle and a trapezoid, and other polygonal shapes such as a hexagon and an octagon can be selected as appropriate.
In addition, the cooling fins may be configured only by the same shape, and a plurality of shapes and / or diameters (diameter when the cross section is circular, elliptical when the cross section is the maximum length when the polygon is a polygon) are mixed. May be configured.

  There is no restriction | limiting in particular about the distribution | circulation speed of the cooling water (refrigerant) which distribute | circulates the flow path 20 of the cooler 16, Usually, 0.1-10 L / min is preferable. When the conditions (1) to (3) are satisfied, good cooling efficiency can be obtained within the above range.

The press contact type semiconductor module of this embodiment can be manufactured as follows.
A green sheet (insulating plate) 14 prepared as described above is formed on the surface of a copper plate (length 35 mm × width 20 mm × thickness 0.3 mm) prepared as the correction metal plate 15, and Cu wiring is further formed on the green sheet 14. The plate 11 is stacked and placed flat, sandwiched between a correction metal plate side and a Cu wiring board side by a tungsten frame, and directly bonded at a copper-copper oxide eutectic point of 1060 to 1070 ° C. Make it.

  Here, a mask is formed on the Cu wiring board 11 of the multilayer substrate by photolithography, and only the surface of the Cu wiring board is disposed so as to be immersed in an etching solution mainly containing ferric chloride. By performing the etching, a wiring pattern (circuit) is formed on the Cu wiring board 11. In the etching, it is important to adjust the position so that the side of the correction metal plate 15 on which the fin is formed is not immersed in the etching solution.

  Next, 8 types of copper wires with different diameters (0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 5 mm) are prepared as cylindrical fins, and each has a length of 5 mm. Cut to align. At this time, polishing the cut surface of the cut copper wire to make it a smooth surface is effective for joining with the correction metal plate or the like.

  Next, a copper plate having a thickness of 5 mm is prepared, and the copper plate is cut by wire cutting to produce a frame 18 constituting the side wall of the cooler 16. And the through-hole of two places (it may be three or more places) for connecting the taper screw joint used as the inlet / outlet of a cooling water is opened on the side surface of a frame using a lathe.

  Next, each cut copper wire is divided into diameters in a carbon jig (having a plurality of circular holes corresponding to the arrangement of cooling fins arranged (a grid-like arrangement position; see FIG. 3)). Insert. A frame 18 made of a copper plate is disposed outside the carbon jig. Subsequently, a brazing material a [for example, silver brazing (a bonding material in which a metal such as copper is added to silver)] is applied to the cut surface of each copper wire and the surface corresponding to the thickness of the frame. Are placed in contact with each other on the surface of the correction metal plate 15 and placed in a furnace in an inert atmosphere. Then, brazing is performed by heating at a temperature of 700 ° C. or higher and bonding is performed. After removing the carbon jig, the brazing material a and the composition used above were further applied to the cut surface opposite to the bonding surface bonded to each copper wire (cooling fin) and the laminated substrate of the frame, and the surface for the thickness. Differently, a brazing material b having a melting point lower than that of the brazing material a (in the case of silver brazing, the solidus line (melting point) is scattered within the range of 600 to 800 ° C. due to the difference in composition) is applied, and this coated surface A copper plate 19 having a thickness of 1.0 mm serving as a lid is placed on top of the other. In this state, it is again placed in an inert atmosphere furnace, heated at a temperature of 600 to 700 ° C., brazed, and joined.

  Thereafter, as shown in FIG. 1- (a), the inlet 21 and the outlet 22 of the cooling water are formed by attaching tapered screw joints to the two through holes provided in the frame 18.

Further, on the side where the wiring pattern (circuit) of the Cu wiring board 11 provided on the green sheet 14 is formed as described above, an IGBT (many 5 mm square to about 1 cm square for automobiles) is provided. 12 and the diode 13 are placed, and the periphery of the IGBT or the like is surrounded by a frame made of resin or the like in order to prevent a positional shift of the IGBT or the like. In this state, the IGBT 12 and the diode 13 are sandwiched between two heat radiating plates (CuMo plates) having high thermal conductivity through the collector electrode of the IGBT 12 and the cathode electrode of the diode 13 and pressurized at 10 MPa. Press contact with the Cu wiring board 11. At this time, the semiconductor element can be fixed so as to be pressed using a bolt and a nut. Usually, the lower surface of the semiconductor element is often a collector electrode in the IGBT and a cathode electrode in the diode. The pressure at the time of pressure contact is generally in the range of 1 to 100 MPa.
The emitter electrode and gate electrode of the IGBT 12 and the anode electrode of the diode 13 and the pad of the Cu wiring board 11 are wire-bonded using a thin aluminum wire having a diameter of 100 to 300 μm to electrically connect the external power and the control circuit. Make a good connection.

  As described above, in this embodiment, as shown in Table 1 below, eight types of cooling (diameter D = 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 5 mm) are provided. A pressure-contact type semiconductor module in which fins are arranged in a grid pattern at four pitches (fin pitch S = 1.25D, 1.5D, 2D, 3D) is prepared.

Next, the performance of each pressure contact type semiconductor module of this embodiment will be described.
(1) Measurement of thermal resistance The inlet 21 and outlet 22 provided in the cooler 16 constituting the semiconductor module of the present invention and the circulating nozzle of the cooling water / warm water circulating device are communicated by a hose to a temperature of 65 ° C. Hot water (hereinafter abbreviated as “Tw”) is circulated at a constant flow rate. This cooling water / warm water circulation device plays a role of, for example, a radiator and a pump mounted in an automobile.

Next, a voltage (hereinafter abbreviated as “Vge”) is applied between the gate electrode and the emitter electrode. At this time, when Vge exceeding a threshold value (Vge (th); usually 4V to 8V) is applied, the IGBT is turned on. In this embodiment, 15 V is applied as Vge.
When a voltage (hereinafter abbreviated as “Vce”) is applied between the collector electrode and the emitter electrode, a current (hereinafter abbreviated as “Ice”) starts to flow between the collector electrode and the emitter electrode. In the saturated state, current hardly flows until Vce is about 2V (since the IGBT has a PN junction), but when it exceeds about 1 to 2V, Ice increases as Vce increases. At this time, heat Q corresponding to the power loss represented by the product of Vce and Ice is generated in the IGBT.

  An insulated sheath thermocouple is brought into contact with the emitter electrode (the upper surface of the IGBT), the surface temperature of the IGBT is measured, and the measured value is taken as the junction temperature of the IGBT (hereinafter abbreviated as “Tj”). The temperature difference ΔT between the IGBT and the cooling water is ΔT = Tj−Tw.

  From the above, the thermal resistance from the semiconductor element to the cooling water (hereinafter abbreviated as “Rth”) is calculated as Rth = ΔT / Q.

  Based on the above, the flow rate of the cooling water was 12 L / min (high-speed flow), current was passed through the IGBT 12, and Rth was measured. The measured value with the pressure contact type semiconductor module of the present invention was less than 0.4 K / W. there were. This value is compared with the conventional commercially available IGBT power module having a thermal resistance (between the element and the case) of 0.4 to 0.6 K / W, and the pressure contact type of the present embodiment configured in a water-cooled type. The thermal resistance of the semiconductor module (Rth is the addition of the thermal resistance of the cooler in addition to the element and the case) is extremely small and good.

Each pressure contact type semiconductor module was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1 below.
<Evaluation criteria>
○: No deformation due to pressure contact, Rth value less than 0.4 K / W, low thermal resistance, and excellent cooling effect even when the flow rate was reduced (0.6 L / min).
Δ: The cooling effect was insufficient, or the heat resistance was low and the cooling efficiency was good, but the fin shape was deformed by the pressure during pressure welding, and the structure could not be maintained.
X: The fin shape was deformed by the pressure at the time of pressure contact and the structure could not be maintained, the value of Rth was 0.4 K / W or more, and the cooling effect was inferior.

The cooling capacity was higher as the cooling fin diameter D was smaller and the fin pitch Sn was narrower. However, in contrast to what is predicted from the local heat transfer between the fin and the cooling water, which is calculated quantitatively by thermofluid calculation, there is a tendency to be somewhat dependent on the arrangement interval of the cooling fins. This is considered to be due to the influence of the heat conductivity (thermal resistance) of the cooling fin, the correction metal plate, the metal constituting the wiring metal plate, and the insulating plate existing in the path from the cooling water to the semiconductor element. .
As shown in Table 1, in the press contact type semiconductor module including the cooling fins that satisfy the above-described conditions (1) to (3) in the present invention, the cooling efficiency is good and the deformation due to the pressurization during the press contact is performed. Could also be effectively prevented.

(Second Embodiment)
A second embodiment of the semiconductor module of the present invention will be described with reference to FIGS. In the present embodiment, the cooling fins disposed in the flow path 20 of the cooler 16 configured as shown in FIG. 1- (c) are arranged in a staggered arrangement.

  Also in the present embodiment, one IGBT and one diode are provided as semiconductor elements for each Cu wiring board on the green sheet, and a unit that is a minimum unit necessary for forming an inverter is configured. Moreover, the same reference numerals are given to the same components as those in the first embodiment, and the detailed description thereof is omitted.

In the semiconductor module of the present embodiment, as shown in FIG. 2- (a), the cooling fin 17 formed into a perfect circular columnar structure (column length L = 5 mm) having a cross section of a diameter D is shown in FIG. 5 are arranged in a zigzag pattern shown in FIG.
About the diameter D and fin pitch Sn of each cooling fin, it was made to be the same as that of 1st Embodiment.

  Also in this embodiment, a pressure contact type semiconductor module was produced in the same manner as in the first embodiment, and the same evaluation was performed. As a result, the same result as in the first embodiment was obtained. Specifically, it is as shown in Table 1 above.

  In this embodiment, the cooling fins are arranged in a zigzag pattern, and when the flow rate of the cooling water is high, a thermal resistance almost equal to that of the grid pattern of the first embodiment is obtained. The staggered arrangement was more effective in terms of thermal resistance when making the flow velocity.

(Third embodiment)
A third embodiment of the semiconductor module of the present invention will be described with reference to FIGS. In this embodiment, a cooling fin having a quadrangular prism structure is provided in the flow path 20 of the cooler 16 configured as shown in FIG. 1- (c).

  Also in the present embodiment, one IGBT and one diode are provided as semiconductor elements for each Cu wiring board on the green sheet, and a unit that is a minimum unit necessary for forming an inverter is configured. Moreover, the same reference numerals are given to the same components as those in the first embodiment, and the detailed description thereof is omitted.

  In the semiconductor module of the present embodiment, the cooling fin is cut by aligning a copper plate having a thickness corresponding to the length of one side of the quadrangular section to a length of 5 mm at intervals corresponding to the width of the side. As shown in (b), the cross-section is a diagonal D (maximum diameter [mm]; in this embodiment, 0.1 mm, 0.2 mm, 0.3 mm, 0.5 mm, 1 mm, 2 mm, 3 mm, 5 mm) A square column structure in which the column length L is 5 mm (see Table 1 above).

  As shown in FIG. 3, the cooling fins are arranged in a grid pattern on the surface of the correction metal plate 15, and the fin pitch is n times the diagonal D (nD; 1.25 times (1.25D) in this embodiment). Four types of 5 times (1.5D), 2 times (2D), and 3 times (3D) were prepared (see Table 1), and they are arranged at a pitch (Sn).

  Also in this embodiment, a pressure contact type semiconductor module was produced in the same manner as in the first embodiment, and the same evaluation was performed. As a result, the same result as in the first embodiment was obtained. Specifically, it is as shown in Table 1 above.

  In the above description, the case where the cross-sectional shape of the cooling fin is a perfect circle shape or a square shape has been mainly described, but the same effect can be obtained even when the cross-sectional shape is other than those described above. In addition, from the viewpoint of pressure resistance during pressure contact, it is desirable to have a polygonal cross-sectional shape such as a triangle or a quadrangle.

  In the above-described embodiment, the configuration using a cooler that performs cooling by passing cooling water as a refrigerant has been mainly described. However, the cooling system is configured not to necessarily form a flow path but to be cooled by air or the like. Also good.

  In addition to the cooling water, a liquid such as oil or other LLC (long life coolant (coolant that can be used for a long time)) can be used as the refrigerant used in the cooler.

In the pressure contact type semiconductor module of the present invention, the copper plate 19 serving as a lid is joined to the correction metal plate 15 with the green sheet (insulating plate) 14 and the Cu wiring board 11 overlapped as in the above embodiments. Instead of the multilayer substrate, the surface of the correction metal plate of the multilayer substrate is joined to the cooling fin, and the multilayer substrate is provided at both ends of the cooling fin with the cooling fin as the center (that is, the cooler is arranged in the center). It is also possible to have a symmetric structure, so that reliability can be improved and semiconductor elements can be mounted at high density. Further, in such a configuration, the thermal stress is canceled and the effect of suppressing the occurrence of warpage can be obtained.
The configuration of the target structure can be applied in each of the above-described embodiments.

  In the present invention, by configuring the cooling fin so as to satisfy any of the above-mentioned conditions (1) to (3), various design requirements (for example, manufacturing method, metal material, manufacturing accompanying these) Depending on the cost, the diameter, shape, and arrangement of the cooling fins (heat conduction fins) can be arbitrarily selected, and the cooling efficiency, pressure resistance, and cooling cycle are superior to those of conventional semiconductor modules. It is possible to ensure reliability.

As described above, since the cooling fins are configured to satisfy any of the above-described conditions (1) to (3), good cooling performance can be obtained. When there is an upper limit or when the cost of the pump is limited, it is possible to arbitrarily select the flow rate of cooling water and the pressure loss associated with the pump power. The selection method in this case is based on the following guidelines.
That is, when the flow rate of circulating coolant is the same, the pressure loss tends to increase when both the maximum diameter D and the fin pitch S of the heat conducting fins are small, and conversely, when both the maximum diameter D and the fin pitch S are large, the pressure Loss tends to be small. Therefore, when flow control is performed using a pump having the same power performance (performance: lift x discharge amount or motor capacity), when designing with a reduced cooling water flow rate, the maximum diameter D and fin pitch of the heat conduction fins When designing with an increased flow rate of cooling water such that S is reduced (when the cooling water temperature is high or the temperature of the refrigerant used is close to the boiling point, etc.), the maximum diameter D and fin pitch of the heat conducting fins By selecting the maximum diameter and the fin pitch so that both S are large, it is possible to obtain the required cooling performance with the same power. By selecting in this way, design requirements such as the flow rate of cooling water can be set to the conditions that maximize the pump efficiency.

(A) is a top view which shows the structure of the semiconductor module which concerns on 1st Embodiment of this invention, (b) is the side surface when the semiconductor module which concerns on 1st Embodiment of this invention of (a) is seen from the side surface It is a figure, (c) is the AA 'sectional view taken on the line of (a). (A) is a perspective view which shows the cooling fin of the cylindrical structure which comprises the semiconductor module which concerns on 1st Embodiment of this invention, (b) is the square pillar which comprises the semiconductor module which concerns on 3rd Embodiment of this invention. It is a perspective view which shows the cooling fin of a structure, (c) is a perspective view which shows the example of the heat conductive fin of a triangular prism structure. It is a figure for demonstrating the state which arranged the cooling fin in the grid pattern shape. It is explanatory drawing for briefly explaining the structural example of the circuit of a three-phase inverter. It is a figure for demonstrating the state which arranged the cooling fin in zigzag form.

Explanation of symbols

11 ... Cu electrode plate 12 ... IGBT
13 ... Diode 14 ... Green sheet (insulating member)
16 ... Cooler 17 ... Cooling fin

Claims (8)

A semiconductor element;
A wiring metal plate on which the semiconductor element is arranged and supplies power to the semiconductor element;
A heat conductive fin having a columnar structure satisfying any of the following (1) to (3), and a cooler for cooling at least the semiconductor element by heat exchange with the heat conductive fin;
(1) 0.1 mm ≦ maximum diameter D ≦ 1.0 mm and D ≦ fin pitch S ≦ 1.25D
(2) 0.2 mm ≦ maximum diameter D ≦ 0.5 mm and 1.25D <fin pitch S ≦ 1.5D
(3) 0.2 mm ≦ maximum diameter D <0.3 mm and 1.5 D <fin pitch S ≦ 2.0 D
An insulating member disposed between the wiring metal plate and the cooler to electrically insulate the semiconductor element and the cooler;
A pressure contact type semiconductor module in which the semiconductor element is mounted on the wiring metal plate by pressure contact.   The cooler has a hollow portion that circulates a refrigerant, and the heat conducting fins are disposed in the hollow portion, exchange heat with the refrigerant that circulates through the hollow portion, and maintain the shape of the cooler. The press-contact type semiconductor module according to claim 1.   The pressure contact type semiconductor module according to claim 1, wherein the heat conducting fin has a cylindrical structure and / or a prismatic structure.   4. The press-contact type semiconductor module according to claim 1, wherein the heat conductive fin has a length in a column length direction of a columnar structure of 0.1 to 20 mm. 5. 5. The press contact according to claim 1, wherein the insulating member is made of ceramics having a linear expansion coefficient of 3 × 10 ⁻⁶ / K to 1 × 10 ⁻⁵ / K. Type semiconductor module.   6. The pressure contact type semiconductor module according to claim 5, wherein the insulating member is made of at least one selected from aluminum nitride, aluminum oxide, silicone nitride, silicone oxide, beryllium oxide, and silicone carbide. The metal plate for wiring is made of a metal having a thermal conductivity of 17 W / m · K or more and a specific resistance of 1 × 10 ⁻⁵ Ω · cm or less. The press contact type semiconductor module of any one of Claims.   8. The press contact type semiconductor module according to claim 7, wherein the wiring metal plate is made of at least one selected from copper, aluminum, tungsten, and molybdenum.

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