JP2017017229A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of suppressing reduction with time in heat resistance of a heat radiation material.SOLUTION: In a semiconductor device 2, a hardening heat radiation material 8 is sandwiched between a power card 10 and an insulation plate 6a. The hardening heat radiation material 8 is a silicon-based heat radiation material. A thickness of the hardening heat radiation material 8 is equal to or more than 15 μm and equal to or less than 100 μm. A viscosity of the heat radiation material under a use environment of the semiconductor device is equal to or more than 1,000 Pa s and equal to or less than 25,000 Pa s.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a semiconductor device. In particular, the present invention relates to a semiconductor device in which semiconductor modules containing semiconductor elements and coolers are alternately stacked.

  In the semiconductor device of the type described above, grease or an adhesive is disposed between the semiconductor module and the cooler in order to improve the cooling performance for the semiconductor element. In the semiconductor device of Patent Document 1, an insulating layer is disposed between the semiconductor module and the cooler, and an adhesive is disposed between the semiconductor module and the insulating layer, and between the insulating layer and the cooler.

Japanese Patent Laid-Open No. 2005-093593

  In the semiconductor device, the semiconductor element generates heat while the semiconductor module is in operation, and when the semiconductor module is stopped, the heat generation of the semiconductor element is also stopped. Each part of the semiconductor device including the semiconductor module, the insulating plate, and the cooler changes in temperature as the temperature of the semiconductor element changes, and repeats expansion and contraction. If expansion and contraction of the member that sandwiches the heat dissipation material are repeated, the heat dissipation material and the member that sandwiches the heat dissipation material may peel off, or air may enter the heat dissipation material and the thermal resistance of the heat dissipation material may decrease over time. .

  This specification provides the technique which suppresses that the thermal resistance of a thermal radiation material falls with time.

  The technology disclosed in the present specification is a semiconductor device in which semiconductor modules containing semiconductor elements and coolers are alternately stacked and arranged, and a load is applied in the stacking direction of the semiconductor modules and coolers About. The semiconductor device includes an insulating member sandwiched between the semiconductor module and the cooler, a curable heat dissipation material sandwiched between at least one of the semiconductor module and the insulating member, and between the insulating member and the cooler. . The thickness of the heat dissipation material is 15 μm or more and 100 μm or less, and the viscosity of the heat dissipation material in the usage environment of the semiconductor device is 1000 Pa · s or more and 25000 Pa · s or less.

  If the heat dissipating material is too thin, peeling of the member that sandwiches the heat dissipating material and the heat dissipating material tends to progress. On the other hand, if the heat dissipation material is too thick, the heat resistance of the heat dissipation material increases. By using the heat radiating material having the thickness in the above range, it is possible to suppress the heat resistance of the heat radiating plate and to prevent the heat radiating plate from being separated from the member sandwiching the heat radiating material. Further, by using a heat radiating material having a viscosity in the above-described range, the heat radiating material can be deformed following the thermal deformation of a member sandwiching the heat radiating material. Thereby, it can suppress that the thermal resistance of a thermal radiation material falls with time.

  Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a perspective view of the semiconductor device of an Example. It is sectional drawing of the semiconductor device cut | disconnected by XY plane in the coordinate system of FIG. It is a graph which shows the experimental result which shows the change of the thermal resistance with respect to the cycle number of a temperature change.

  A semiconductor device according to an embodiment will be described with reference to the drawings. FIG. 1 is a perspective view of the semiconductor device 2. The semiconductor device 2 is a unit in which a plurality of power cards 10 and a plurality of coolers 3 are stacked. In FIG. 1, reference numeral 10 is given to only one power card, and reference numerals are omitted for the other power cards. Similarly, in FIG. 1, reference numeral 3 is assigned to only one cooler, and reference numerals are omitted for the other coolers. In addition, the case 31 for housing the semiconductor device 2 is drawn with imaginary lines so that the entire semiconductor device 2 can be seen. One power card 10 is sandwiched between two coolers 3. An insulating plate 6 a is sandwiched between the power card 10 and one cooler 3, and an insulating plate 6 b is sandwiched between the power card 10 and the other cooler 3. A cured heat dissipation material 8 (see FIG. 2) is disposed between the power card 10 and the insulating plates 6a and 6b. Grease 11 (see FIG. 2) is applied between the insulating plates 6a and 6b and the cooler 3. In FIG. 1, illustration of the cured heat dissipation material 8 and the grease 11 is omitted. Further, in FIG. 1, for easy understanding, one power card 10 and insulating plates 6 a and 6 b are extracted from the semiconductor device 2 and drawn.

  One power card 10 accommodates four semiconductor elements. Specifically, the four semiconductor elements are two transistors Ta and Tb and two diodes Da and Db. The semiconductor element is cooled by the refrigerant passing through the cooler 3. The refrigerant is a liquid, typically water.

  The power card 10 and the cooler 3 are both flat plate types, and are laminated so that the flat surfaces having the largest areas face each other among the plurality of side surfaces. The power card 10 and the cooler 3 are alternately stacked, and coolers are located at both ends in the stacking direction of the units. The plurality of coolers 3 are connected by connecting pipes 5a and 5b. A refrigerant supply pipe 4a and a refrigerant discharge pipe 4b are connected to the cooler 3 positioned at one end in the stacking direction of the units. The refrigerant supplied through the refrigerant supply pipe 4a is distributed to all the coolers 3 through the connection pipe 5a. The refrigerant absorbs heat from the adjacent power card 10 while passing through each cooler 3. The refrigerant passing through each cooler 3 passes through the connecting pipe 5b and is discharged from the refrigerant discharge pipe 4b.

  When the semiconductor device 2 is accommodated in the case 31, a leaf spring 32 is inserted into the other end side in the stacking direction of the units. By the leaf spring 32, a load is applied to the unit in which the power card 10, the insulating plates 6a and 6b, and the cooler 3 are laminated from both sides in the lamination direction. The load is, for example, 3 [kN]. As will be described later, grease is applied between the insulating plate and the power card, and a heat dissipation sheet is further sandwiched. A high load of 3 [kN] stretches the grease layer thinly and increases the heat transfer efficiency from the power card 10 to the cooler 3. The power card 10 is directly deprived of heat by the insulating plates 6a and 6b. In the semiconductor device 2, the insulating plates 6a and 6b are in contact with the power card 10 containing the semiconductor elements (elements Ta, Tb, Da, and Db) with the cured heat dissipation material 8 interposed therebetween, and the power card 10 and the cooler 3 are in contact with each other. It is a device in which a load is applied in the stacking direction so that the grease 11 between them is thinned.

  The power card 10 will be described. In the power card 10, the heat radiating plates 16a and 16b are exposed on one flat surface 10a facing the insulating plate 6a. Another heat radiating plate 17 (not shown in FIG. 1) is exposed on the flat surface 10b opposite to the flat surface 10a. An insulating plate 6b is in contact with the flat surface 10b with grease interposed therebetween. Three electrode terminals 7a, 7b, and 7c extend from the upper surface of the power card 10 (the surface facing the positive direction of the Z-axis in the figure), and from the lower surface (the surface facing the negative direction of the Z-axis direction in the figure). The control terminal 29 is extended.

  The structure between the power card 10 and the cooler 3 will be described with reference to FIG. FIG. 2 is a cross-sectional view of the power card 10 of FIG. 1 cut along a plane parallel to the XY plane of the coordinate system in the drawing and across the transistors Ta and Tb.

  First, the internal structure of the power card 10 will be described. Four semiconductor elements (transistors Ta and Tb, diodes Da and Db) are accommodated in a resin package 13. The package 13 is formed by injection molding and seals the semiconductor element. Hereinafter, the flat surfaces 10a and 10b of the power card 10 may be referred to as the flat surfaces 10a and 10b of the package 13.

  All the semiconductor elements are flat chips. The collector electrode is exposed on one flat surface of the chip of the transistor Ta (Tb), and the emitter electrode is exposed on the other flat surface. The electrode on one flat surface of the transistor Ta is joined to the back surface of the heat radiating plate 16 a by solder 15. The surface of the heat radiating plate 16 a is exposed on the flat surface 10 a of the package 13. The electrode on the other flat surface of the transistor Ta is joined to the back surface of the heat sink 17 by the solder 15 via the conductive spacer 14. The surface of the heat sink 17 is exposed on the flat surface 10 b of the package 13. Note that the gate electrode of the transistor Ta (Tb) is provided at the end of one flat surface of the chip. Similarly to the transistor Ta, each electrode of the transistor Tb is joined to the heat radiating plate 16b and the heat radiating plate 17 using the solder 15 and the spacer 14.

  The heat sink 16a is a part of the electrode terminal 7a. In the electrode terminal 7a for connecting the electrode of the transistor Ta to another external device, a portion exposed to the flat surface 10a of the package 13 corresponds to the heat radiating plate 16a. Since the electrode terminal 7a is in contact with the electrode of the transistor Ta, it easily conducts heat inside the transistor Ta. On the other hand, since the cooler 3 is made of aluminum (conductive metal), it is necessary to insulate it from the heat sink 16a. Therefore, the semiconductor device 2 has the insulating plate 6a sandwiched between the cooler 3 and the heat radiating plate 16a (power card 10). The insulating plates 6a and 6b are made of ceramics that are thin, highly insulating, and have good heat conductivity. The heat sink 16a (electrode terminal 7a) and the spacer 14 are made of copper having excellent conductivity and heat conductivity. The same applies to the heat sink 16b and the heat sink 17.

  Similarly to the heat dissipation plate 16a, the heat dissipation plates 16b and 17 are also part of the electrode terminals 7b and 7c. The diodes Da and Db are also flat chips like the transistors Ta and Tb. The electrodes exposed on the flat surfaces of the diodes Da and Db are connected to the heat sinks 16a, 16b, and 17 in the same manner as the transistors Ta and Tb.

A cured heat radiating material 8 is disposed on the entire surface of the heat radiating plate 16 a and the heat radiating plate 16 b and the flat surface 10 a of the package 13. The cured heat radiating material 8 is disposed on the entire surface of the heat radiating plate 16b and between the flat surface 10a of the package 13 and the insulating plate 6a. The curing heat dissipation material 8 is, for example, a silicon-based heat dissipation material that cures at room temperature. Curing heat dissipation material 8 includes a filler containing zinc oxide and aluminum oxide. The filler has a size of about 10 μm. As the curing heat dissipation material 8, a material having a viscosity before curing of 800 Pa · s or less is selected. Further, after the curing, the cured heat dissipation material 8 has a linear expansion coefficient of 1.0 × 10 ⁻⁴ to 10 ⁻⁶ (1 / K) and an elongation of 50% or more under the usage environment of the semiconductor device 2. Yes, with a viscosity of 1000 Pa · s to 25000 Pa · s. Curing heat dissipation material 8 has a thickness of 15 μm or more and 100 μm or less. The cured heat radiation material 8 is not firmly bonded to the entire surface of the heat dissipation plate 16a and the heat dissipation plate 16b and the flat surface 10a and the insulating plate 6a of the package 13, and the entire surface of the heat dissipation plate 16a and the heat dissipation plate 16b. When the flat surface 10a of the package 13 and the insulating plate 6a are thermally deformed, they are bonded to such an extent that they can be easily peeled off.

  In the modification, the curing heat dissipation material 8 may be a heat-curing heat dissipation material. Further, the cured heat dissipation material 8 may be an adhesive or an adhesive. That is, the cured heat dissipation material 8 may be any heat dissipation material having the above properties.

  The curing heat radiation material 8 is formed between the power card 10 and the insulating plate 6a before curing, and is cured by applying a load from both sides of the power card 10 and the insulating plate 6a. In addition, the hardening heat dissipation material 8 may be arrange | positioned between the power card 10 and the insulating board 6a after hardening.

  Grease 11 is applied between the insulating plate 6 a and the cooler 3. Similarly, grease 11 is also applied between the insulating plate 6b and the cooler 3.

  Between the flat surface 10 a of the power card 10 and the cooler 3, the power card 10, the cured heat radiating material 8, the insulating plate 6 a, the grease 11, and the cooler 3 are stacked in this order. Between the flat surface 10 b of the power card 10 and the cooler 3, the power card 10, the cured heat radiating material 8, the insulating plate 6 b, the grease 11, and the cooler 3 are stacked in this order.

  The effect of the present embodiment will be described. If a heat dissipating material that does not harden silicone oil such as grease is disposed between the power card 10 and the insulating plate 6a, the silicon oil is removed from the power card 10 by thermal deformation of the silicon oil, the power card 10 and the insulating plate 6a. It leaves from between the insulating plates 6a, and air enters. As a result, the cooling performance of the semiconductor device is reduced. On the other hand, in the semiconductor device 2 of the present embodiment, the silicon oil contained in the cured heat dissipation material 8 is cured. For this reason, it is possible to suppress the silicon oil from dropping from between the power card 10 and the insulating plate 6a. Thereby, it can suppress that the cooling performance of the semiconductor device 2 falls.

  Further, the cured heat dissipation material 8 has a thickness of 15 μm or more and 100 μm or less. When the thickness of the cured heat radiating material 8 is relatively thin, less than 15 μm, the detachment between the cured heat radiating material 8 and the power card 10 or the insulating plate 6a easily progresses, and the thermal resistance increases. On the other hand, when the thickness of the cured heat dissipation material 8 increases, the thermal resistance increases. Thermal resistance can be suppressed by setting the thickness of the cured heat dissipation material 8 to 15 μm or more and 100 μm or less.

Further, as the curing heat dissipation material 8, a material having a viscosity before curing of 800 Pa · s or less is selected. Further, the cured heat dissipation material 8 has a linear expansion coefficient of 1.0 × 10 ⁻⁴ to 10 ⁻⁶ (1 / K) after curing, an elongation of 50% or more, and a viscosity of 1000 to 25000 Pa · s. Choose one. According to this configuration, the cured heat radiating material 8 can be deformed following the thermal deformation of the power card 10 and the insulating plate 6 a sandwiching the cured heat radiating material 8. Further, even when a difference occurs in the thermal deformation between the power card 10 and the insulating plate 6a, the cured heat radiating material 8 itself is prevented from being peeled off from the power card 10 and the insulating plate 6a. can do.

  In FIG. 3, an experiment in which a cycle of temperature change in which the semiconductor element of the semiconductor device 2 is heated and cooled by using three types of curing heat dissipation materials 8 of different materials was repeated was performed. In this experiment, the change in the thermal resistance of the cured heat dissipation material 8 was observed. In this experiment, the experiment was performed using the cured heat radiation materials 8A, 8B, and 8C made of three kinds of materials having different elongation (%) and viscosity after curing (Pa · s). Further, in this experiment, as a comparative example, an experiment using grease instead of the cured heat radiation material 8 was also performed. The elongation (%) of the cured heat radiation materials 8A, 8B, and 8C is a result of a test based on JIS K 6251 using No. 5 type dumbbell test pieces. Curing heat dissipation materials 8A, 8B, and 8C have viscosities at 23 ° C. The combinations of (elongation (%), viscosity (Pa · s)) of the cured heat radiation materials 8A, 8B, and 8C are (47, 3,973), (4, 25, 535), and (192, 6, 872), respectively. ).

  Experimental results of the cured heat dissipation materials 8A, 8B, and 8C are shown as results RA, RB, and RC, respectively. Moreover, the experimental result of grease is shown by result RG. In the graph of FIG. 3, the horizontal axis indicates the number of cycles of temperature change when the temperature change at which heat is generated and cooled is one cycle, and the vertical axis indicates thermal resistance (° C./W). As is clear from the experimental results, in the heat radiating materials 8A and 8C having relatively large elongation and low viscosity, deterioration of thermal resistance was suppressed as compared with grease. Therefore, the elongation of the cured heat radiating material 8 is preferably 47% or more. On the other hand, in the heat radiating material 8B having a relatively large elongation and a high viscosity, the thermal resistance was deteriorated more than the grease. The reason for this is that the cured heat radiating material 8B has a small elongation and is not easily deformed, so that peeling occurred at the interface between the power card 10 and the insulating plate 6a sandwiching the cured heat radiating material 8B.

  As is clear from the above experiment, according to the cured heat radiating material 8 of this example, it is possible to suppress the thermal resistance from decreasing with time.

  Points to be noted regarding the technology described in the embodiments will be described. It should be noted that in the drawing, the thickness of the grease layer, the thickness of the cured heat dissipation material, and the like are emphasized in order to help understanding.

  As shown in FIG. 2, the inside of the cooler 3 is a simple cavity. In the internal space of the cooler 3, fins that contact the back surface of the side plates that contact the insulating plates 6a and 6b may be provided.

  In the above embodiment, the cured heat radiation material 8 is disposed between the power card 10 and the insulating plates 6a and 6b. However, the cured heat radiating material 8 may be arranged in place of the grease 11 between each of the insulating plates 6 a and 6 b and the cooler 3. In this case, the cured heat dissipation material 8 may be disposed between the power card 10 and the insulating plates 6a and 6b, or grease may be disposed.

  Moreover, you may form a hollow in the surface of heat sink 16a, 16b, 17b, and may arrange | position the hardening heat dissipation material 8 in the hollow. According to this configuration, the thickness of the cured heat dissipation material 8 can be controlled in accordance with the depth of the recess. As a result, the thermal resistance of the cured heat dissipation material 8 can be controlled.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Semiconductor device 3: Cooler 4a: Refrigerant supply pipe 4b: Refrigerant discharge pipe 5a, 5b: Connection pipe 6a, 6b: Insulating plates 7a, 7b, 7c: Electrode terminal 8: Curing heat dissipation material 10: Power card 10a, 10b : Flat surface 11: Grease 13: Package 14: Spacer 15: Solder 16a, 16b, 17: Heat sink 29: Control terminal 31: Case 32: Leaf spring Da, Db: Diode Ta, Tb: Transistor

Claims (1)

A semiconductor device in which a semiconductor element is housed and a cooler are alternately stacked and arranged, and a load is applied in the stacking direction of the semiconductor module and the cooler,
An insulating member sandwiched between the semiconductor module and the cooler;
A curable heat dissipation material sandwiched between at least one of the semiconductor module and the insulating member and between the insulating member and the cooler;
The thickness of the heat dissipation material is 15 μm or more and 100 μm or less,
The semiconductor device, wherein the heat dissipation material has a viscosity of 1000 Pa · s or more and 25000 Pa · s or less in an environment where the semiconductor device is used.

Images