Semiconductor modules and power converters

Abstract

To suppress peeling between a resin filling the periphery of a heat dissipation member and the heat dissipation member, even if the structure in the periphery of a semiconductor element is difficult to be filled with a resin.SOLUTION: A semiconductor module 1 includes a semiconductor element 3, a first lead frame 5 connected to the semiconductor element 3, a first bonding member 17 for bonding the semiconductor element 3 and the first lead frame 5, a second lead frame 7 connected to the semiconductor element 3, a second bonding member 19 for bonding the semiconductor element 3 and the second lead frame 7, a heat dissipation member 9, a first sealing material 11 which is provided so as to cover the periphery of the semiconductor element 3, a region between the first lead frame 5 and the second lead frame 7, the first bonding member 17, and the second bonding member 19, and a second sealing material 13 which is provided so as to cover the periphery of the first sealing material 11 and the whole heat dissipation member 9, wherein a coefficient of linear expansion of the second sealing material 13 has a value closer to a coefficient of linear expansion of the heat dissipation member 9 than a coefficient of linear expansion of the first sealing material 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a semiconductor module and a power conversion device.

Background Art

[0002] Conventionally, a semiconductor device using a horizontal semiconductor chip is disclosed in Patent Document 1. In the semiconductor device disclosed in Patent Document 1, two bus bars are joined to the upper surface of the semiconductor chip, and a heat dissipation member is disposed on the lower surface. Thus, in a horizontal semiconductor chip, since two metal plates having different potentials are mounted on the same surface of the chip, it is necessary to fill the resin between the metal plates and around the semiconductor chip in order to prevent discharge between the metal plates.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described conventional semiconductor device, since the structure around the semiconductor chip is a structure in which it is difficult to fill the resin, it is necessary to use a resin having a low viscosity in order to improve the filling property. However, when a resin having a low viscosity is used, the linear expansion coefficient generally becomes high, so that there is a problem that peeling occurs between the heat dissipation member disposed on the lower surface of the semiconductor chip and the resin.

[0005] Therefore, the present invention has been proposed in view of the above circumstances, and an object thereof is to provide a semiconductor module capable of suppressing peeling between the resin filled around the heat dissipation member and the heat dissipation member even when the structure around the semiconductor element is a structure in which it is difficult to fill the resin.

Means for Solving the Problems

[0006] To solve the above-mentioned problems, a semiconductor module according to one aspect of the present invention comprises a semiconductor element, a first lead frame and a second lead frame connected to the semiconductor element, and a heat dissipation member. Furthermore, it comprises a first bonding member for joining the semiconductor element and the first lead frame, a second bonding member for joining the semiconductor element and the second lead frame, a first encapsulant, and a second encapsulant. The first encapsulant is provided to cover the periphery of the semiconductor element, the region between the first lead frame and the second lead frame, the first bonding member, and the second bonding member, while the second encapsulant is provided to cover the periphery of the first encapsulant and the entire heat dissipation member. The coefficient of thermal expansion of the second encapsulant is closer to the coefficient of thermal expansion of the heat dissipation member than the coefficient of thermal expansion of the first encapsulant. [Effects of the Invention]

[0007] According to the present invention, even if the structure surrounding the semiconductor element is such that it is difficult to fill with resin, it is possible to suppress the occurrence of delamination between the resin filled around the heat dissipation member and the heat dissipation member. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view along line BB in Figure 2, showing the structure of a semiconductor module according to the first embodiment. [Figure 2] Figure 2 is a cross-sectional view taken along line AA in Figure 1, showing the structure of a semiconductor module according to the first embodiment. [Figure 3] Figure 3 is a side view illustrating the manufacturing method of a semiconductor module according to the first embodiment. [Figure 4] Figure 4 is a top view illustrating the manufacturing method of a semiconductor module according to the first embodiment. [Figure 5] Figure 5 is a side view illustrating the manufacturing method of a semiconductor module according to the first embodiment. [Figure 6] Figure 6 is a top view illustrating the manufacturing method of a semiconductor module according to the first embodiment. [Figure 7]Figure 7 is a top view illustrating the manufacturing method of a semiconductor module according to the first embodiment. [Figure 8] Figure 8 is a cross-sectional view showing the structure of a semiconductor module according to the second embodiment. [Figure 9] Figure 9 is a cross-sectional view showing the structure of a semiconductor module according to the third embodiment. [Modes for carrying out the invention]

[0009] [First Embodiment] A first embodiment to which the present invention is applied will be described below with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals, and detailed descriptions are omitted.

[0010] [Structure of a semiconductor module] The structure of the semiconductor module according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view along line BB in Figure 2 showing the structure of the semiconductor module according to this embodiment, and Figure 2 is a cross-sectional view along line AA in Figure 1 showing the structure of the semiconductor module according to this embodiment. The semiconductor module 1 is a power semiconductor used in power conversion devices such as inverters and converters. As shown in Figures 1 and 2, the semiconductor module 1 comprises a semiconductor element 3, a first lead frame 5, a second lead frame 7, a heat dissipation member 9, a first encapsulating material 11, a second encapsulating material 13, and a frame 15. The semiconductor element 3 and the first lead frame 5 are joined by a first bonding member 17, the semiconductor element 3 and the second lead frame 7 are joined by a second bonding member 19, and the semiconductor element 3 and the heat dissipation member 9 are joined by a third bonding member 21.

[0011] The semiconductor element 3 is a semiconductor chip that functions as a power switching semiconductor element such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or a power rectifier semiconductor element such as a freewheeling diode. The device structure of the semiconductor element 3 is a so-called lateral semiconductor device, and it has multiple electrodes with different potentials on the top surface of the chip. For example, in the case of a MOSFET, it has a drain electrode, a source electrode, and a gate electrode, and in the case of a diode, it has an anode electrode and a cathode electrode. In addition, it may also have a source electrode for control, an electrode for temperature detection, and an electrode for current detection. The electrodes are mainly made of metallic materials such as aluminum and copper, but their surfaces may have a metal such as nickel formed on them by plating for soldering. In this embodiment, the case where the semiconductor element 3 is a MOSFET will be described as an example.

[0012] Furthermore, while silicon is commonly used as the material for semiconductor element 3, in order to realize a higher-performance semiconductor chip, semiconductor element 3 may also be a wide-bandgap semiconductor such as silicon carbide or gallium nitride.

[0013] The first lead frame 5 is a wiring of metal plates connected to the drain electrode, and the second lead frame 7 is a wiring of metal plates connected to the source electrode. Metal materials such as copper, aluminum, and copper cladding are used. The first lead frame 5 is joined to the semiconductor element 3 by a first bonding member 17, and the second lead frame 7 is joined to the semiconductor element 3 by a second bonding member 19. The first bonding member 17 and the second bonding member 19 are formed from metals such as solder and sintered silver. Furthermore, the first lead frame 5 and the second lead frame 7 are provided with recesses 25 and 27, respectively, for passing through the frame 15.

[0014] Furthermore, a metal plate material made of copper, copper molybdenum, or the like for stress relaxation may be provided between the first lead frame 5, the second lead frame 7, and the semiconductor element 3, and the top and bottom thereof may be joined with solder or sintered silver. The first lead frame 5 and the second lead frame 7 may be plated with nickel or the like on the surface for soldering. Further, processing such as providing a resist to prevent the solder from spreading too much, making holes for adjusting the thickness of the solder, or making holes for facilitating resin filling may be performed.

[0015] The heat radiating member 9 is a metal plate formed of a metal material having a high thermal conductivity mainly composed of copper. The heat radiating member 9 is disposed on the lower surface of the semiconductor element 3 and has a function of radiating the heat generated by the semiconductor element 3 to a cooler (not shown). However, in addition to copper, it may be formed of a metal material having a high thermal conductivity such as aluminum or copper molybdenum. The heat radiating member 9 is joined to the semiconductor element 3 by a third joining member 21. The third joining member 21 is formed of a metal such as solder or sintered silver.

[0016] Furthermore, when the semiconductor element 3 is a vertical semiconductor element, it is necessary to use a material having an insulating function such as a ceramic substrate as the heat radiating member 9. However, in this embodiment, since the semiconductor element 3 employs a horizontal semiconductor element, it is not necessary to use a material having an insulating function for the heat radiating member 9, and high heat radiating performance can be achieved. In particular, in order to enhance the heat radiating effect of the heat radiating member 9, the heat radiating performance can be further improved by using a material with a thickness of 1 mm or more. In this embodiment, the case where copper is used for the heat radiating member 9 will be described as an example.

[0017] The first encapsulant 11 is a resin filled around the semiconductor element 3. Specifically, the first encapsulant 11 is provided to cover the periphery of the semiconductor element 3, the region between the first lead frame 5 and the second lead frame 7, the first bonding member 17, and the second bonding member 19. The range filled with the first encapsulant 11 is limited by the frame 15, and is filled in a range narrower than the upper surface of the heat dissipation member 9, and the entire heat dissipation member 9 is not covered. However, by using transfer molding or the like, the first encapsulant 11 may be used for encapsulation without using the frame 15.

[0018] For the first encapsulant 11, for example, a resin potting material is used, and it is mainly composed of additives such as epoxy resin, ceramic filler, and flame retardant. In this embodiment, since the semiconductor element 3 is horizontal, the region between the lead frames is narrow, and the structure is such that it is difficult to fill the encapsulant. Therefore, the first encapsulant 11 needs to be a resin having a lower viscosity value before curing than the second encapsulant 13 and is easy to fill.

[0019] Here, as characteristics of a general resin, the viscosity and the linear expansion coefficient change according to the addition amount of the ceramic filler. When the addition amount of the ceramic filler is reduced, the viscosity becomes low and the linear expansion coefficient becomes high. Therefore, the addition amount of the ceramic filler may be adjusted so that the viscosity of the first encapsulant 11 becomes low.

[0020] However, when the addition amount of the ceramic filler is adjusted so that the viscosity becomes low, the linear expansion coefficient becomes high. Therefore, if the entire semiconductor module 1 is encapsulated only with the first encapsulant 11, the first encapsulant 11 is likely to peel off around the heat dissipation member 9 having a low linear expansion coefficient. Therefore, in this embodiment, a second encapsulant 13 having a low linear expansion coefficient is separately prepared, and the periphery of the heat dissipation member 9 is encapsulated with this second encapsulant 13 to suppress such peeling.

[0021] The second encapsulant 13 is a resin filled outside the area sealed by the first encapsulant 11. Specifically, the second encapsulant 13 is provided to cover the periphery of the first encapsulant 11 and the entire heat dissipation member 9. Furthermore, the second encapsulant 13 covers not only the periphery of the semiconductor element 3 and the entire heat dissipation member 9, but also the upper surfaces of the first and second lead frames 5 and 7, thereby covering the entire semiconductor module 1. In Figure 1, the upper and side surfaces of the heat dissipation member 9 are covered with the second encapsulant 13, but the lower surface of the heat dissipation member 9 may also be covered with the second encapsulant 13.

[0022] The second sealant 13 is made of, for example, a resin potting material and is mainly composed of epoxy resin, ceramic filler, and additives such as flame retardant. By adjusting the amount of ceramic filler added, the viscosity of the second sealant 13 before curing increases, but its coefficient of thermal expansion becomes lower than that of the first sealant 11, and is close to that of copper, which is the material of the heat dissipation member 9. However, even if the viscosity of the second sealant 13 is high, it is still possible to fill the area outside the frame 15 with the second sealant 13 because the structure is not complex.

[0023] As a result of these adjustments, in this embodiment, the coefficient of thermal expansion of the second encapsulant 13 is closer to the coefficient of thermal expansion of the heat dissipation member 9 than the coefficient of thermal expansion of the first encapsulant 11. This allows the second encapsulant 13 to suppress delamination around the heat dissipation member 9, and the first encapsulant 11 to improve the filling properties around the semiconductor element 3, even if the structure is difficult to fill with resin.

[0024] Specifically, by setting the coefficient of thermal expansion of the second encapsulant 13 to a value within a predetermined range of the coefficient of thermal expansion of the heat dissipation member 9, delamination occurring around the heat dissipation member 9 can be suppressed. This predetermined range should be set to a range that can suppress delamination. Furthermore, by setting the viscosity of the first encapsulant 11 to a predetermined value lower than the viscosity of the second encapsulant 13, the first encapsulant 11 can be filled even if the structure around the semiconductor element 3 is difficult to fill with resin. This predetermined value should be set to a viscosity that can achieve sufficient filling.

[0025] Furthermore, since the first encapsulating material 11 seals the area around the semiconductor element 3, it will be affected by the heat generated by the semiconductor element 3. Therefore, it is necessary to improve the heat dissipation performance, and it is desirable that the first encapsulating material 11 has a higher thermal conductivity than the second encapsulating material 13.

[0026] Furthermore, since the first encapsulant 11 reaches a higher temperature, using a material with a high glass transition temperature can prevent fluctuations in its properties. Therefore, it is desirable that the first encapsulant 11 has a higher glass transition temperature than the second encapsulant 13.

[0027] Furthermore, by using a resin with high moisture resistance that is less permeable to moisture for the second sealing material 13, it becomes possible to prevent moisture from entering even if a resin with low moisture resistance is used for the first sealing material 11. Therefore, it is desirable that the second sealing material 13 has higher moisture resistance than the first sealing material 11.

[0028] Furthermore, since the first encapsulant 11 covers the first and second lead frames 5 and 7 and the semiconductor element 3, the electric field strength increases when a high voltage is applied. For this reason, the first encapsulant 11 needs to be made of a resin with higher dielectric strength. Therefore, it is desirable that the first encapsulant 11 has higher dielectric strength than the second encapsulant 13.

[0029] The frame 15 is provided to fill the semiconductor element 3 with the first encapsulant 11 and is made of a resin material such as PPS (Poly Phenylene Sulfide) resin. The frame 15 is a plate-shaped member provided to surround the semiconductor element 3 on all four sides and is installed on the heat dissipation member 9. Its height from the heat dissipation member 9 is higher than the joint surface between the first lead frame 5 and the first bonding member 17 and the joint surface between the second lead frame 7 and the second bonding member 19. Therefore, when the first encapsulant 11 is filled into the frame 15, the area around the semiconductor element 3, the first bonding member 17, the second bonding member 19, and the third bonding member 21 are covered by the first encapsulant 11. Furthermore, the area between the first lead frame 5 and the second lead frame 7 is also covered by the first encapsulant 11.

[0030] [Manufacturing method for semiconductor modules] Next, the manufacturing method of the semiconductor module according to this embodiment will be described with reference to Figures 3 to 7. First, as shown in Figures 3 and 4, the semiconductor element 3 and the heat dissipation member 9 are joined by the third joining member 21, the first lead frame 5 and the semiconductor element 3 are joined by the first joining member 17, and the second lead frame 7 and the semiconductor element 3 are joined by the second joining member 19. Figure 3 is a side view showing the state after joining, and Figure 4 is a top view. The first lead frame 5 and the second lead frame 7 are provided with recesses 25 and 27, respectively.

[0031] In this process, the first to third bonding members 17, 19, and 21 are all soldered and joined together by reflow soldering. At this time, in order to prevent tilting of the semiconductor element 3, the third bonding member 21 uses a bonding material that can maintain a predetermined constant thickness when bonding. For example, solder containing nickel balls can be used. Alternatively, a wire may be used to prevent tilting of the semiconductor element 3, or copper protrusions may be provided on the heat dissipation member 9.

[0032] Furthermore, the third joining member 21 may be joined separately from the first joining member 17 and the second joining member 19 using a different material. For example, if a joining material such as sintered silver that does not melt when joining the first joining member 17 and the second joining member 19 is used as the third joining member 21, the semiconductor element 3 and the heat dissipation member 9 are first joined with the third joining member 21. After that, even if reflow soldering is performed to join the first and second lead frames 5 and 7 to the semiconductor element 3, the third joining member 21 will not melt, so its thickness can be kept constant, and tilting of the semiconductor element 3 can be prevented. Also, even if a high-melting-point solder is used as the third joining member 21, the thickness of the third joining member 21 can be kept constant by reflow soldering the first joining member 17 and the second joining member 19 separately from the third joining member 21.

[0033] Once the first and second lead frames 5 and 7 and the heat dissipation member 9 are joined to the semiconductor element 3, the frame 15 is then installed. First, as shown in Figures 5 and 6, a frame component 50, which is part of the frame 15, is attached to the heat dissipation member 9 with adhesive or the like. The frame component 50 is a plate-shaped member formed to surround three sides of the semiconductor element 3. Figure 5 is a side view showing the frame component 50 attached, and Figure 6 is a top view.

[0034] At this time, the first lead frame 5 and the second lead frame 7 are provided with recesses 25 and 27, respectively, so the frame component 50 is attached so that it fits into the recesses 25 and 27. Then, as shown in Figure 7, the frame component 52 that makes up the remaining part of the frame 15 is attached to the heat dissipation member 9 with adhesive or the like to complete the frame 15. Through these steps, it is possible to create a frame 15 that has no gaps that would cause leakage even when the first sealing material 11 is filled in.

[0035] Next, the first encapsulant 11 is injected into the frame 15 by potting. At this time, the first encapsulant 11 is filled to the height of the frame 15. In this embodiment, since the semiconductor element 3 is a horizontal element, the gap between the first lead frame 5 and the second lead frame 7 is narrow, making it difficult to fill with encapsulant. However, since the viscosity of the first encapsulant 11 is adjusted to a sufficiently low value below a predetermined value, the first encapsulant 11 can be filled into the frame 15 without any gaps. As a result, discharge can be prevented even when a high voltage is applied between the first lead frame 5 and the second lead frame 7.

[0036] Furthermore, the frame 15 can be made higher by the amount by which recesses 25 and 27 are provided in the first and second lead frames 5 and 7. Therefore, the first sealing material 11 can cover not only the area around the semiconductor element 3, but also the region between the first lead frame 5 and the second lead frame 7, the first bonding member 17, and the second bonding member 19.

[0037] After this, a frame (not shown) is provided as needed, and the second encapsulant 13 is injected into the frame by potting. As a result, the second encapsulant 13 is formed to cover the periphery of the first encapsulant 11 and the entire heat dissipation member 9, completing the semiconductor module 1. The coefficient of linear expansion of the second encapsulant 13 is close to the predetermined range of the coefficient of linear expansion of the heat dissipation member 9, so peeling can be suppressed, and defects such as discharge due to peeling can be prevented even when temperature changes occur.

[0038] After this, the semiconductor module 1 may be attached to the cooler with grease or the like, or it may be bonded to the cooler using a bonding material. Although not shown in the diagram, if the semiconductor element 3 has a gate electrode or a source electrode for control, these may be taken out with aluminum wire and connected to the external terminals of the semiconductor module 1.

[0039] [Effects of the First Embodiment] As described in detail above, the semiconductor module 1 according to this embodiment includes a first encapsulant 11 that covers the area around the semiconductor element 3, the region between the first lead frame 5 and the second lead frame 7, the first bonding member 17, and the second bonding member 19. Furthermore, it includes a second encapsulant 13 that covers the area around the first encapsulant 11 and the entire heat dissipation member 9, and the coefficient of thermal expansion of the second encapsulant 13 is closer to the coefficient of thermal expansion of the heat dissipation member 9 than the coefficient of thermal expansion of the first encapsulant 11. As a result, even if the structure around the semiconductor element 3 is such that it is difficult to fill with resin, delamination around the heat dissipation member 9 can be suppressed.

[0040] In particular, in this embodiment, the second encapsulant 13 can suppress the occurrence of delamination around the heat dissipation member 9, and even if the structure around the semiconductor element 3 is difficult to fill with resin, the first encapsulant 11 can improve the filling properties. Therefore, it is possible to realize a semiconductor module 1 that has high reliability and good manufacturing yield while taking advantage of the benefits of high heat dissipation performance and the ability to conduct large currents.

[0041] Furthermore, in the semiconductor module 1 according to this embodiment, the first encapsulant 11 has a lower viscosity before curing than the second encapsulant 13. As a result, even if the structure surrounding the semiconductor element 3 is such that it is difficult to fill with resin, the first encapsulant 11 can be filled around the semiconductor element 3.

[0042] Furthermore, in the semiconductor module 1 according to this embodiment, the first encapsulant 11 has a higher glass transition temperature than the second encapsulant 13. This prevents the resin properties from changing even if the first encapsulant 11 becomes hot due to the heat generated by the semiconductor element 3.

[0043] Furthermore, in the semiconductor module 1 according to this embodiment, the first encapsulant 11 has a higher thermal conductivity than the second encapsulant 13. This allows heat generated in the semiconductor element 3 to be dissipated through the first encapsulant 11, thereby improving cooling performance.

[0044] Furthermore, in the semiconductor module 1 according to this embodiment, the first encapsulant 11 has a higher dielectric strength than the second encapsulant 13. As a result, a high electric field is applied to the semiconductor element 3 and the first and second lead frames 5 and 7, and discharge can be suppressed even when the distance between the first and second lead frames 5 and 7 is short.

[0045] Furthermore, in the semiconductor module 1 according to this embodiment, the second encapsulant 13 has higher moisture resistance than the first encapsulant 11. As a result, the second encapsulant 13, which is placed on the outside, can prevent humidity from entering the module.

[0046] Furthermore, in the semiconductor module 1 according to this embodiment, the heat dissipation member 9 is made of a material mainly composed of copper. This improves heat dissipation performance.

[0047] Furthermore, in the semiconductor module 1 according to this embodiment, the first bonding member 17 and the second bonding member 19 are made of metal. This allows for a longer bonding life and reduces the resistance and inductance of the wiring.

[0048] Furthermore, in the semiconductor module 1 according to this embodiment, the third bonding member 21 is a bonding material that does not melt when bonding the first bonding member 17 and the second bonding member 19. This makes it possible to control the thickness of the bonding material to a constant value and suppress the tilt of the semiconductor element 3.

[0049] Furthermore, in the semiconductor module 1 according to this embodiment, the third bonding member 21 is a bonding material that can maintain a predetermined constant thickness when bonding the first bonding member 17 and the second bonding member 19. This makes it possible to control the thickness of the bonding material to a constant value and suppress the tilt of the semiconductor element 3.

[0050] Furthermore, the semiconductor module 1 according to this embodiment is provided with a frame 15 for filling the semiconductor element 3 with the first encapsulating material 11. The height of the frame 15 is higher than the joint surface between the first lead frame 5 and the first bonding member 17 and the joint surface between the second lead frame 7 and the second bonding member 19. As a result, the first and second bonding members 17 and 19 can be covered with the first encapsulating material 11, thereby extending the lifespan of the joint.

[0051] Furthermore, in the semiconductor module 1 according to this embodiment, the semiconductor element 3 is made of a wide-bandgap semiconductor. With a wide-bandgap semiconductor, the chip area is smaller, making it more difficult to fill the structure around the semiconductor element 3 with resin. Therefore, by using a wide-bandgap semiconductor for the semiconductor element 3 in this embodiment, the filling performance can be more effectively improved and delamination can be prevented around the heat dissipation member 9.

[0052] Furthermore, in this embodiment, a power conversion device equipped with a semiconductor module 1 is configured. This makes it possible to realize a power conversion device with high heat dissipation performance and high reliability.

[0053] [Second Embodiment] A second embodiment to which the present invention is applied will be described below with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals, and detailed descriptions are omitted.

[0054] Figure 8 is a cross-sectional view showing the structure of the semiconductor module 1 according to this embodiment. As shown in Figure 8, the semiconductor module 1 according to this embodiment differs from the first embodiment in that the first lead frame 5 is bent in the opposite direction to the semiconductor element 3 outside the position where it is joined to the first bonding member 17. Similarly, the second lead frame 7 is bent in the opposite direction to the semiconductor element 3 outside the position where it is joined to the second bonding member 19. That is, the first and second lead frames 5 and 7 are bent at the position of the frame 15 so that the distance from the heat dissipation member 9 is increased.

[0055] In the first embodiment, since the first lead frame 5 and the second lead frame 7 are flat metal plates, recesses 25 and 27 were provided to increase the height of the frame 15. However, even with the recesses 25 and 27 provided, there is a limit to the height of the frame 15.

[0056] Therefore, in this embodiment, the distance between the first and second lead frames 5 and 7 and the heat dissipation member 9 at the position of the frame 15 is increased by bending the first lead frame 5 and the second lead frame 7 in the height direction of the frame 15. As a result, the frame 15 can be raised to the desired height, which not only eliminates the need to process the first and second lead frames 5 and 7 to provide recesses 25 and 27, but also increases the height of the area sealed by the first sealing material 11, as shown in Figure 8. Consequently, the area between the first lead frame 5 and the second lead frame 7 can be sealed with only the first sealing material 11. Furthermore, by making the dielectric strength of the first sealing material 11 higher than that of the second sealing material 13, the insulation performance of the semiconductor module 1 can be improved.

[0057] Furthermore, since the distance between the first and second lead frames 5 and 7 and the heat dissipation member 9 can be increased, it becomes easier to fill the first sealing material 11 and the possibility of discharge can be reduced.

[0058] [Effects of the second embodiment] As described in detail above, in the semiconductor module 1 according to this embodiment, the first lead frame 5 is bent in the opposite direction to the semiconductor element 3 outside the position where it is joined to the first bonding member 17. Similarly, the second lead frame 7 is bent in the opposite direction to the semiconductor element 3 outside the position where it is joined to the second bonding member 19. This allows the frame 15 to be made higher, eliminating the need for processing to provide the recesses 25 and 27, and also improving the insulation performance of the semiconductor module 1.

[0059] [Third Embodiment] A third embodiment to which the present invention is applied will be described below with reference to the drawings. In the drawings, the same parts are denoted by the same reference numerals, and detailed descriptions are omitted.

[0060] Figure 9 is a cross-sectional view showing the structure of the semiconductor module 1 according to this embodiment. As shown in Figure 9, the semiconductor module 1 according to this embodiment differs from the first embodiment in that it is further provided with a cooling plate 60. Specifically, the semiconductor module 1 of this embodiment further includes a cooling plate 60 provided on the side of the heat dissipation member 9 opposite to the side on which the semiconductor elements 3 are arranged, and a fourth bonding member 62 that joins the heat dissipation member 9 and the cooling plate 60. The fourth bonding member 62 is covered with a second sealing material 13.

[0061] The cooling plate 60 is made of a metal material with high thermal conductivity, such as copper, aluminum, or a composite material thereof. Heat is dissipated from the underside of the cooling plate 60 using a coolant such as water or by using forced air. Alternatively, fins may be directly provided on the underside of the cooling plate 60.

[0062] The fourth joining member 62 is formed of a metal such as solder, sintered silver, or copper. When using solder, the fourth joining member 62 can be joined by reflow at the same time as the first and second lead frames 5 and 7 are joined to the semiconductor element 3, or when the semiconductor element 3 is joined to the heat dissipation member 9. When joining with sintered or paste-formed silver or copper material, the heat dissipation member 9 and the cooling plate 60 may be joined before the reflow that joins the semiconductor element 3 to the heat dissipation member 9, or the heat dissipation member 9 and the cooling plate 60 may be joined after all reflows are completed.

[0063] The second sealing material 13 covers the periphery of the first sealing material 11 and the entire heat dissipation member 9, as well as the upper surface of the cooling plate 60, so that it covers the fourth joining member 62. This reduces the stress on the fourth joining member 62, thereby improving the joining life of the fourth joining member 62.

[0064] [Effects of the third embodiment] As described in detail above, the semiconductor module 1 according to this embodiment further includes a cooling plate 60 provided on the side of the heat dissipation member 9 opposite to the side on which the semiconductor element 3 is arranged, and a fourth bonding member 62 that joins the heat dissipation member 9 and the cooling plate 60. The fourth bonding member 62 is covered with a second sealing material 13. This makes it possible to realize a semiconductor module 1 with even higher heat dissipation performance and higher reliability. In addition, by covering the fourth bonding member 62 with the second sealing material 13, the stress on the fourth bonding member 62 can be reduced, thereby improving the bonding life of the fourth bonding member 62.

[0065] Furthermore, in the semiconductor module 1 according to this embodiment, the fourth bonding member 62 is made of metal. This improves heat dissipation performance.

[0066] The embodiments described above are merely examples of the present invention. Therefore, the present invention is not limited to the embodiments described above, and various modifications can be made to forms other than those described above, as long as they do not depart from the technical spirit of the present invention, depending on the design and other factors. [Explanation of symbols]

[0067] 1. Semiconductor module 3 Semiconductor elements 5. First lead frame 7. Second Lead Frame 9 Heat dissipation component 11. First sealing material 13. Second sealing material 15th slot 17. First Joining Member 19. Second Joining Member 21 Third Joining Member 25, 27 recesses 50, 52 Frame parts 60 Cooling Plates 62 Fourth Joining Member

Claims

1. A semiconductor element having multiple electrodes on one side, A first lead frame connected to a first electrode among a plurality of electrodes of the semiconductor element, A first joining member that joins the semiconductor element and the first lead frame, A second lead frame connected to the second electrode among the plurality of electrodes of the semiconductor element, A second joining member that joins the semiconductor element and the second lead frame, A heat dissipation member disposed on the other side of the semiconductor element, A third bonding member is disposed on the upper surface of the heat dissipation member and joins the semiconductor element and the heat dissipation member, A first sealing material is provided covering the area around the semiconductor element, the region between the first lead frame and the second lead frame, the first bonding member, and the second bonding member. The periphery of the first sealing material and the second sealing material provided to cover at least the upper surface and side surface of the heat dissipation member Equipped with, A semiconductor module in which the coefficient of thermal expansion of the second encapsulating material is closer to the coefficient of thermal expansion of the heat dissipation member than the coefficient of thermal expansion of the first encapsulating material.

2. The semiconductor module according to claim 1, wherein the first encapsulant has a lower viscosity before curing than the second encapsulant.

3. The semiconductor module according to claim 1, wherein the first encapsulant has a higher glass transition temperature than the second encapsulant.

4. The semiconductor module according to claim 1, wherein the first encapsulant has a higher thermal conductivity than the second encapsulant.

5. The semiconductor module according to claim 1, wherein the first encapsulant has a higher dielectric strength than the second encapsulant.

6. The semiconductor module according to claim 1, wherein the second encapsulant has higher moisture resistance than the first encapsulant.

7. The semiconductor module according to claim 1, wherein the heat dissipation member is formed of a material mainly composed of copper.

8. The semiconductor module according to claim 1, wherein the first bonding member and the second bonding member are formed of metal.

9. The semiconductor module according to claim 8, wherein the third joining member is a non-melting joining material when joining the first joining member and the second joining member.

10. The semiconductor module according to claim 8, wherein the third joining member is a joining material capable of maintaining a predetermined constant thickness when joining the first joining member and the second joining member.

11. The semiconductor element is provided with a frame for filling it with the first sealing material. The semiconductor module according to any one of claims 1 to 10, wherein the height of the frame is higher than the bonding surface between the first lead frame and the first bonding member and the bonding surface between the second lead frame and the second bonding member.

12. The first lead frame is bent in the opposite direction to the semiconductor element outside the position where it is joined to the first bonding member. The semiconductor module according to claim 11, wherein the second lead frame is bent in the opposite direction to the semiconductor element outside the position where it is joined to the second bonding member.

13. A cooling plate provided on the side of the heat dissipation member opposite to the side on which the semiconductor element is arranged, The system further comprises a fourth joining member that joins the heat dissipation member and the cooling plate, The semiconductor module according to any one of claims 1 to 10, wherein the fourth bonding member is covered with the second sealing material.

14. The semiconductor module according to claim 13, wherein the fourth bonding member is made of metal.

15. The semiconductor module according to any one of claims 1 to 10, wherein the semiconductor element is a wide-bandgap semiconductor.

16. A power conversion device comprising a semiconductor module according to any one of claims 1 to 10.

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