Semiconductor Module and Method for Manufacturing the Same

Abstract

To reduce manufacturing cost.SOLUTION: Semiconductor elements 5 and 6 are mounted on the upper surface of a frame portion 1. A heat sink 12 is bonded to the lower surface of the frame portion 1. An insulating sheet 13 is provided on the lower surface of the heat sink 12. A sealing material 14 seals the frame portion 1, the semiconductor elements 5 and 6, and the heat sink 12 to form a module body 15. The thickness of the heat sink 12 is 50% or more of the thickness of the module body 15.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a semiconductor module and a method for manufacturing the same.

Background Art

[0002] Transfer molded power modules using insulating sheets of resin mixtures having high heat dissipation are used in a wide range of fields such as home appliances. A semiconductor element is mounted on the upper surface of the frame portion, and a heat sink is provided on the lower surface of the frame portion to improve heat dissipation. An insulating sheet is provided to insulate the power circuit inside the module from the outside.

[0003] Conventionally, the insulating sheet has been disposed between the frame portion and the heat sink. However, since the insulating sheet is adjacent to the semiconductor element which is a heat generation source, it has been necessary to make the insulating sheet highly heat resistant. A configuration in which an insulating sheet is provided on the lower surface of the heat sink has also been proposed (see, for example, Patent Document 1), but it has not been possible to sufficiently suppress the temperature rise of the insulating sheet only by that.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to make the insulating sheet highly heat resistant, it is necessary to adjust the filler content or change the resin material. Since these changes make the insulating sheet expensive, there has been a problem that the manufacturing cost increases.

[0006] The present disclosure has been made to solve the above-described problems, and an object thereof is to obtain a semiconductor module and a method for manufacturing the same that can reduce the manufacturing cost.

Means for Solving the Problem

[0007] The semiconductor module according to the present disclosure includes a frame portion, a semiconductor element mounted on the upper surface of the frame portion, a heat sink joined to the lower surface of the frame portion, an insulating sheet provided on the lower surface of the heat sink, and a sealing material that seals the frame portion, the semiconductor element, and the heat sink to form a module body, wherein the thickness of the heat sink is 50% or more of the thickness of the module body. Further, the cross-section of the heat sink is a trapezoid in which the lower side on the insulating sheet side is longer than the upper side on the frame part side It is characterized by this.

[0008] The manufacturing method of the semiconductor module according to the present disclosure includes a step of providing an insulating sheet on the lower surface of a heat sink, a step of putting the heat sink and the insulating sheet into a first mold and sealing them with a first sealing material to form a lower part of the module, a step of placing a frame portion on the upper surface of the heat sink exposed from the first sealing material, a step of mounting a semiconductor element on the upper surface of the frame portion, and a step of putting the lower part of the module, the frame portion, and the semiconductor element into a second mold and sealing the frame portion and the semiconductor element with a second sealing material to form an upper part of the module. The thickness of the heat sink is 50% or more of the total thickness of the lower part and the upper part of the module It is characterized by this.

Advantages of the Invention

[0009] In the semiconductor module according to the present disclosure, an insulating sheet is provided on the lower surface of the heat sink, and the thickness of the heat sink is 50% or more of the thickness of the module body. By sufficiently separating the insulating sheet from the semiconductor element which is a heat generation source, thermal breakdown of the insulating sheet can be suppressed. Therefore, since a highly heat-resistant insulating sheet is not required, the manufacturing cost can be reduced.

[0010] In the manufacturing method of the semiconductor module according to the present disclosure, the lower part and the upper part of the module are molded separately. Thereby, individual selection of the resin materials and the molding conditions for both of them becomes possible. Therefore, since the manufacturing process can be simplified, the manufacturing cost can be reduced.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] A semiconductor module according to an embodiment and a manufacturing method thereof will be described with reference to the drawings. The same or corresponding components may be denoted by the same reference numerals, and repeated description may be omitted.

[0013] Embodiment 1. FIG. 1 is a cross-sectional view showing a semiconductor module according to Embodiment 1. The frame portions 1 and 2 and the terminals 3 and 4 are provided at the same height and are separated from each other. Semiconductor elements 5 and 6 are mounted on the upper surface of the frame portion 1. For example, the semiconductor element 5 is an IGBT, and the semiconductor element 6 is a diode. A control element 7 is mounted on the frame portion 2. The upper surface electrodes of the semiconductor elements 5 and 6 are connected to each other by a wire 8. The upper surface electrode of the semiconductor element 6 is connected to one end of the terminal 3 by a wire 9. The control electrode of the semiconductor element 5 is connected to the control element 7 by a wire 10. One end of the control element 7 and the terminal 4 are connected by a wire 11. The control element 7 drives the semiconductor element 5 according to a signal input from the terminal 4, and the output signals from the semiconductor elements 5 and 6 are output from the terminal 3.

[0014] A heat sink 12 is joined to the lower surface of the frame portion 1. An insulating sheet 13 is provided on the lower surface of the heat sink 12. The insulating sheet 13 is a mixture of an epoxy resin and a filler. The filler is a particulate ceramic-based additive.

[0015] A sealing material 14 seals the frame portion 1, the semiconductor elements 5 and 6, and the heat sink 12 to form a module body 15. The sealing material 14 is an epoxy resin or the like. The other ends of the terminals 3 and 4 protrude from the side surface of the module body 15, respectively. The lower surface of the insulating sheet 13 is exposed from the sealing material 14 on the lower surface of the module body 15. A copper foil or the like may be provided on the lower surface of the insulating sheet 13. The lower surface of the module body 15 serves as a heat dissipation surface. The heat dissipation surface is adhered by an external heat dissipation fin and a grease material.

[0016] Next, the effects of the present embodiment will be described in comparison with a comparative example. FIG. 2 is a cross-sectional view showing a semiconductor module according to the comparative example. In the comparative example, an insulating sheet 16 is disposed between the frame portion 1 and the heat sink 12. Since the insulating sheet 16 is adjacent to the semiconductor element which is a heat generation source, the insulating sheet 16 is exposed to a high temperature almost at the same level as the maximum temperature of the semiconductor elements 5 and 6. Therefore, since it is necessary to make the insulating sheet 16 have high heat resistance, the manufacturing cost increases. In recent years, with the practical application of SiC devices, an insulating sheet having high heat resistance is required in the structure of the comparative example. However, since the glass transition temperature of the resin mixture of the insulating sheet 16 is generally 160 to 170°C, a significant improvement in heat resistance is difficult in terms of technology and cost. On the other hand, in the present embodiment, since the insulating sheet 13 is provided on the lower surface of the heat sink 12, the insulating sheet 13 can be separated from the semiconductor elements 5 and 6 which are heat generation sources.

[0017] In the comparative example, 10% of the thermal resistance of the main heat dissipation path on the lower surface side of the module is the frame portion 1, and 90% is the insulating sheet 16. On the other hand, in the present embodiment, 10% of the thermal resistance of the main heat dissipation path is the frame portion 1, 30% is the heat sink 12, and 60% is the insulating sheet 13. Therefore, in the present embodiment, the proportion of the insulating sheet 13 in the thermal resistance of the main heat dissipation path can be reduced.

[0018] FIG. 3 is a diagram showing the relationship between the ratio of the thickness of the heat sink to the thickness of the module body and the temperature of the insulating sheet. The thermal resistance was estimated based on the thermal conductivity and the longitudinal thickness of the materials of the respective layers existing between the semiconductor elements 5 and 6 which are heat generation sources and the insulating sheet 13, and the temperature of the insulating sheet 13 was calculated. In the region where the ratio A / B of the thickness A of the heat sink 12 to the thickness B of the module body 15 is less than 50%, the temperature of the insulating sheet 13 decreases remarkably as the thickness A of the heat sink 12 increases. When A / B becomes 50% or more, the temperature decrease of the insulating sheet 13 gradually becomes dull. When A / B reaches 75%, the temperature decrease of the insulating sheet 13 saturates.

[0019] Therefore, in this embodiment, the thickness A of the heat sink 12 is set to be 50% or more of the thickness B of the module body 15 (A / B ≥ 0.50), and more preferably 75% or more (A / B ≥ 0.75). That is, by sufficiently separating the insulating sheet 13 from the semiconductor elements 5 and 6 which are heat sources, the thermal resistance of the heat transfer path between the two is deliberately increased. As a result, the ambient temperature of the insulating sheet 13 decreases, so that thermal breakdown of the insulating sheet 13 can be suppressed. Therefore, since a highly heat-resistant insulating sheet is not required, the manufacturing cost can be reduced. In addition, a power device with a higher operating temperature can be mounted as the semiconductor elements 5 and 6.

[0020] The heat flow from the semiconductor elements 5 and 6 is thermally diffused by the heat sink 12 having a large heat capacity. At this time, transient heat is flattened and released from the heat dissipation surface. Since the thick heat sink 12 stores the heat flow once before releasing it to the outside in this way, the ambient temperature of the insulating sheet 13 of this embodiment provided on the lower surface of the heat sink 12 is about 20°C to 30°C lower than that of the insulating sheet 16 of the comparative example provided directly below the semiconductor elements 5 and 6. However, the temperature difference between the two varies depending on operating conditions and the like.

[0021] Also, in the comparative example, since the height of the frame portion 1 is lower than that of the frame portion 2 and the terminals 3 and 4, the sealing material 14 above the frame portion 1 becomes thick. Therefore, since the thermal resistance from the semiconductor elements 5 and 6 mounted on the frame portion 1 to the upper surface of the module is more than 10 times that of the heat dissipation path on the lower surface side of the module, the upper surface side of the module hardly becomes a heat dissipation path.

[0022] On the other hand, in this embodiment, the terminals 3 and 4 and the frame portions 1 and 2 are of the same height. For this reason, the sealing material 14 above the frame portion 1 can be made thin, and the thermal resistance from the semiconductor elements 5 and 6 to the upper surface of the module can be reduced. Therefore, the heat dissipation performance of the entire module can be improved. In addition, since the height of the frame portion 1 increases, it is also effective to separate the insulating sheet 13 from the semiconductor elements 5 and 6 which are heat sources.

[0023] Also, aluminum is used as the material of the heat sink 12 from the viewpoints of cost and workability. On the other hand, the material of the frame portion 1 is copper or the like. Therefore, the thermal conductivity of the heat sink 12 is lower than that of the frame portion 1. The thermal resistance R [m 2 ·K / W] is obtained by R = d / λ from the thickness d [m] of the heat insulating material and the thermal conductivity λ [W / (m·K)]. Therefore, since the thermal resistance between the semiconductor elements 5 and 6 which are heat generation sources and the insulating sheet 13 increases, the ambient temperature of the insulating sheet 13 can be lowered. Note that it is preferable that the material of the heat sink 12 is an alloy material having a lower thermal conductivity than aluminum.

[0024] Embodiment 2. FIG. 4 is a cross-sectional view showing a semiconductor module according to Embodiment 2. The sealing material 14 has a first sealing material 14a provided on the lower surface side of the frame portion 1 and a second sealing material 14b provided on the upper surface side of the frame portion 1. A bonding interface 17 exists between the first sealing material 14a and the second sealing material 14b. The first sealing material 14a and the second sealing material 14b are directly bonded via the bonding interface 17. The bonding interface 17 can be confirmed by visual inspection or analysis. The first sealing material 14a and the second sealing material 14b may be the same material or different materials.

[0025] The first sealing material 14a covers the side surfaces of the heat sink 12 and the insulating sheet 13. The upper surface of the heat sink 12 is exposed from the first sealing material 14a and is flush with the upper surface of the first sealing material 14a. The second sealing material 14b covers the upper surfaces and side surfaces of the frame portions 1 and 2 and the terminals 3 and 4, the semiconductor elements 5 and 6, the control element 7, and the wires 8 to 11. The lower surface of the second sealing material 14b is flush with the lower surfaces of the frame portions 1 and 2 and the terminals 3 and 4. The lower surface of the frame portion 1 is exposed from the second sealing material 14b and is in contact with the upper surface of the heat sink 12.

[0026] Further, the cross-section of the heat sink 12 is a trapezoid in which the lower side on the insulating sheet 13 side is longer than the upper side on the frame portion 1 side. Therefore, the area of the upper surface of the heat sink 12 that receives heat from the semiconductor elements 5 and 6, which are heat sources, is smaller than the area of the lower surface of the heat sink 12 that releases heat to the external radiation fins. As a result, the thermal resistance between the semiconductor elements 5 and 6 and the insulating sheet 13 can be further increased, and the rise in the ambient temperature of the insulating sheet 13 can be further suppressed. Also, since heat can be diffused throughout the heat sink 12, the heat sink 12 can be miniaturized. Other configurations are the same as those in the first embodiment.

[0027] FIGS. 5 to 9 are cross-sectional views showing a method of manufacturing a semiconductor module according to the second embodiment. First, as shown in FIG. 5, an insulating sheet 13 is provided on the lower surface of the heat sink 12. The heat sink 12 and the insulating sheet 13 are placed in a first mold 18. Next, as shown in FIG. 6, a first sealing material 14a is injected into the first mold 18 to seal the heat sink 12 and the insulating sheet 13 with the first sealing material 14a to form a module lower portion 15a. As shown in FIG. 7, the upper surface of the module lower portion 15a is flat, and the upper surface of the first sealing material 14a and the upper surface of the heat sink 12 are flush.

[0028] Next, as shown in FIG. 8, the frame portions 1 and 2 and the terminals 3 and 4 are placed on the upper surface of the module lower portion 15a at the same height. In particular, the frame portion 1 is placed on the upper surface of the heat sink 12 exposed from the first sealing material 14a. The semiconductor elements 5 and 6 are mounted on the upper surface of the frame portion 1. The semiconductor elements 5 and 6 are wire-connected to the terminals 3 and 4. The module lower portion 15a, the frame portions 1 and 2, a part of the terminals 3 and 4, and the semiconductor elements 5 and 6 are placed in a second mold 19.

[0029] Next, as shown in FIG. 9, a second sealing material 14b is injected into the second mold 19 to seal the frame portions 1 and 2 and the semiconductor elements 5 and 6 with the second sealing material 14b to form a module upper portion 15b. The semiconductor module according to the present embodiment is manufactured by the above steps.

[0030] Conventionally, after mounting chips on the frame portion and bonding wires, molding was performed in a batch manner. The insulating sheet was adhered to the frame portion by the temperature and pressure of resin curing during molding.

[0031] In contrast, in the present embodiment, the lower module portion 15a and the upper module portion 15b are molded separately. Therefore, the resin materials or molding conditions of the first sealing material 14a and the second sealing material 14b may be different from each other. As a result, individual selection of the resin materials and molding conditions for both can be achieved. Thus, the manufacturing process can be simplified, and the manufacturing cost can be reduced. In addition, process design optimized for each molding process becomes possible, and the manufacturing quality is improved.

[0032] Also, it is preferable that the upper surface of the lower module portion 15a is flat. Thereby, the frame portions 1, 2 and the terminals 3, 4 can be placed on the upper surface of the lower module portion 15a at the same height. Further, similar to Embodiment 1, the thickness of the heat sink 12 is 50% or more of the total thickness of the lower module portion 15a and the upper module portion 15b, but preferably 75% or more. Thereby, the same effect as in Embodiment 1 can be obtained. Further, the manufacturing method of the present embodiment can be similarly applied even when the cross section of the heat sink 12 is rectangular as in Embodiment 1.

[0033] Note that the semiconductor elements 5 and 6 are not limited to those formed of silicon, and may be formed of a wide-bandgap semiconductor having a larger bandgap than silicon. The wide-bandgap semiconductor is, for example, silicon carbide, a gallium nitride-based material, or diamond. Since a semiconductor chip formed of such a wide-bandgap semiconductor has high breakdown voltage and allowable current density, it can be miniaturized. By using this miniaturized semiconductor chip, a semiconductor device incorporating this semiconductor chip can also be miniaturized and highly integrated. Further, since the semiconductor chip has high heat resistance, the heat dissipation fins of the heat sink can be miniaturized and the water cooling part can be air-cooled, so that the semiconductor device can be further miniaturized. Further, since the semiconductor chip has low power loss and high efficiency, the semiconductor device can be made highly efficient.

[0034] As described above, the preferred embodiments and the like have been described in detail. However, the present invention is not limited to the above-described embodiments and the like, and various modifications and substitutions can be made to the above-described embodiments and the like without departing from the scope described in the claims. Hereinafter, aspects of the present disclosure will be summarized as appendices.

[0035] (Appendix 1) A frame part, A semiconductor element mounted on the upper surface of the frame part, A heat sink joined to the lower surface of the frame part, An insulating sheet provided on the lower surface of the heat sink, A sealing material that seals the frame part, the semiconductor element, and the heat sink to form a module body, A semiconductor module, characterized in that the thickness of the heat sink is 50% or more of the thickness of the module body. (Appendix 2) The semiconductor module according to Appendix 1, characterized in that the thickness of the heat sink is 75% or more of the thickness of the module body. (Appendix 3) The sealing material has a first sealing material provided on the lower surface side of the frame part and a second sealing material provided on the upper surface side of the frame part. The semiconductor module according to appended claim 1 or 2, characterized in that a bonding interface exists between the first sealing material and the second sealing material. (Appended claim 4) Further comprising a terminal having one end connected to the semiconductor element and the other end protruding from a side surface of the sealing material, The semiconductor module according to any one of appended claims 1 to 3, characterized in that the terminal and the frame portion are at the same height. (Appended claim 5) The semiconductor module according to any one of appended claims 1 to 4, characterized in that a cross section of the heat sink is a trapezoid in which a lower side on the insulating sheet side is longer than an upper side on the frame portion side. (Appended claim 6) The semiconductor module according to any one of appended claims 1 to 5, characterized in that a thermal conductivity of the heat sink is lower than a thermal conductivity of the frame portion. (Appended claim 7) The semiconductor module according to any one of appended claims 1 to 6, characterized in that the insulating sheet is a mixture of a resin and a filler. (Appended claim 8) The semiconductor module according to any one of appended claims 1 to 7, characterized in that the semiconductor element is formed of a wide bandgap semiconductor. (Appended claim 9) A step of providing an insulating sheet on a lower surface of a heat sink, A step of placing the heat sink and the insulating sheet in a first mold and sealing them with a first sealing material to form a lower part of a module, A step of placing a frame portion on an upper surface of the heat sink exposed from the first sealing material, A step of mounting a semiconductor element on an upper surface of the frame portion, A method for manufacturing a semiconductor module, comprising: a step of placing the lower part of the module, the frame portion, and the semiconductor element in a second mold and sealing the frame portion and the semiconductor element with a second sealing material to form an upper part of the module. (Appended claim 10) The manufacturing method of the semiconductor module according to appended note 9, characterized in that the resin materials or the mold forming conditions of the first sealing material and the second sealing material are different from each other. (Appended note 11) The upper surface of the lower part of the module is flat, The frame part and the terminals are placed on the upper surface of the lower part of the module, The manufacturing method of the semiconductor module according to appended note 9 or 10, characterized in that the terminals are wire-connected to the semiconductor elements and sealed with the second sealing material. (Appended note 12) The manufacturing method of the semiconductor module according to any one of appended notes 9 to 11, characterized in that the thickness of the heat sink is 50% or more of the total thickness of the lower part and the upper part of the module. (Appended note 13) The manufacturing method of the semiconductor module according to any one of appended notes 9 to 11, characterized in that the thickness of the heat sink is 75% or more of the total thickness of the lower part and the upper part of the module.

Explanation of reference numerals

[0036] 1 Frame part, 3, 4 Terminals, 5, 6 Semiconductor elements, 12 Heat sink, 13 Insulating sheet, 14 Sealing material, 14a First sealing material, 14b Second sealing material, 15 Module body, 15a Lower part of module, 15b Upper part of module, 17 Bonding interface, 18 First mold, 19 Second mold

Claims

1. A frame portion, A semiconductor element mounted on the upper surface of the frame portion, A heat sink joined to the lower surface of the frame portion, An insulating sheet provided on the lower surface of the heat sink, And a sealing material that seals the frame portion, the semiconductor element, and the heat sink to form a module body, The thickness of the heat sink is 50% or more of the thickness of the module body, The semiconductor module is characterized in that a cross section of the heat sink is a trapezoid in which a lower side on the insulating sheet side is longer than an upper side on the frame portion side.

2. The semiconductor module according to claim 1, wherein the thickness of the heat sink is 75% or more of the thickness of the module body.

3. The sealing material has a first sealing material provided on the lower surface side of the frame portion and a second sealing material provided on the upper surface side of the frame portion, The semiconductor module according to claim 1 or 2, characterized in that a bonding interface exists between the first sealing material and the second sealing material.

4. Further comprising a terminal having one end connected to the semiconductor element and the other end protruding from a side surface of the sealing material, The semiconductor module according to claim 1 or 2, characterized in that the terminal and the frame portion are at the same height.

5. The semiconductor module according to claim 1 or 2, characterized in that the thermal conductivity of the heat sink is lower than the thermal conductivity of the frame portion.

6. The semiconductor module according to claim 1 or 2, characterized in that the insulating sheet is a mixture of resin and filler.

7. The semiconductor module according to claim 1 or 2, characterized in that the semiconductor element is formed of a wide bandgap semiconductor.

8. A step of providing an insulating sheet on the lower surface of the heat sink; A step of placing the heat sink and the insulating sheet in a first mold and sealing them with a first sealing material to form the lower part of the module; A step of placing a frame portion on the upper surface of the heat sink exposed from the first sealing material; A step of mounting a semiconductor element on the upper surface of the frame portion; A step of placing the lower part of the module, the frame portion, and the semiconductor element in a second mold and sealing the frame portion and the semiconductor element with a second sealing material to form the upper part of the module, The method for manufacturing a semiconductor module, characterized in that the thickness of the heat sink is 50% or more of the total thickness of the lower part and the upper part of the module.

9. The method for manufacturing a semiconductor module according to claim 8, characterized in that the resin materials or mold molding conditions of the first sealing material and the second sealing material are different from each other.

10. The upper surface of the lower part of the module is flat, Place the frame portion and terminals on the upper surface of the lower part of the module, Wire-connect the terminals to the semiconductor element and seal with the second sealing material. The method for manufacturing a semiconductor module according to claim 8 or 9, characterized in that.

11. The method for manufacturing a semiconductor module according to claim 8 or 9, characterized in that the thickness of the heat sink is 75% or more of the total thickness of the lower part and the upper part of the module.

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