Semiconductor unit and semiconductor module

Abstract

To provide a semiconductor unit and a semiconductor module that can suppress costs.SOLUTION: A semiconductor unit of the embodiment has a semiconductor chip, a first conductive member, a second conductive member, a first insulating member, a case, and a second insulating member. The first insulating member encapsulates the semiconductor chip, the first conductive member and the second conductive member. The case is arranged around a semiconductor package that includes the semiconductor chip, the first conductive member, the second conductive member, and the first insulating member. In the case, a first portion located on a first side of the first conductive member and a second portion located on a second side of the second conductive member are one piece. The second insulating member encapsulates the semiconductor package. The strength of the case is greater than that of the first and second insulating members.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] An embodiment of the present invention relates to a semiconductor unit and a semiconductor module. [Background technology]

[0002] A power conversion device is formed by connecting a plurality of semiconductor modules in series. A semiconductor module is formed by connecting a plurality of semiconductor units in parallel. It is required to reduce the cost of the semiconductor units. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3258200 [Patent Document 2] Patent No. 4385324 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a semiconductor unit and a semiconductor module that can reduce costs. [Means for solving the problem]

[0005] A semiconductor unit according to a first aspect of the embodiment includes a semiconductor chip, a first conductive member, a second conductive member, a first insulating member, a case, and a second insulating member. The first conductive member is disposed on a first side of the semiconductor chip and is electrically connected to the semiconductor chip. The opposite side of the first side is a second side. The second conductive member is disposed on a second side of the semiconductor chip and is electrically connected to the semiconductor chip. The first insulating member seals the semiconductor chip, the first conductive member, and the second conductive member, except for a part of the first conductive member and a part of the second conductive member. The case is disposed around a semiconductor package including the semiconductor chip, the first conductive member, the second conductive member, and the first insulating member. In the case, a first portion disposed on the first side of the first conductive member and a second portion disposed on the second side of the second conductive member are integrated. The second insulating member is disposed inside the case and seals the semiconductor package, except for a part of the semiconductor package. The strength of the case is greater than the strength of the first insulating member and the strength of the second insulating member.

[0006] A second aspect of the embodiment is the semiconductor unit of the first aspect, further comprising a third conductive member and a fourth conductive member. The third conductive member is disposed between the first conductive member and a first portion of the case and is electrically connected to the first conductive member. The fourth conductive member is disposed between the second conductive member and a second portion of the case and is electrically connected to the second conductive member. The second insulating member seals the semiconductor package, the third conductive member, and the fourth conductive member, except for a portion of the third conductive member and a portion of the fourth conductive member.

[0007] In a third aspect of the embodiment, in the semiconductor unit of the first or second aspect, the first insulating member and the second insulating member are mainly composed of the same type of material.

[0008] In a fourth embodiment, in the semiconductor unit according to any one of the first to third embodiments, the larger of the linear expansion coefficients of the first insulating member and the second insulating member is referred to as the large coefficient and the smaller of the linear expansion coefficients is referred to as the small coefficient, and the difference between the large coefficient and the small coefficient is less than 50% of the large coefficient.

[0009] A fifth aspect of the embodiment is the semiconductor unit of the second aspect, further comprising a first bonding material and a second bonding material. The first bonding material electrically connects components of the semiconductor package. The second bonding material electrically connects the semiconductor package to the third conductive member and the fourth conductive member. The melting point of the first bonding material is higher than the melting point of the second bonding material.

[0010] A sixth aspect of the embodiment is the semiconductor unit of the fifth aspect, wherein the difference between the melting point of the first bonding material and the melting point of the second bonding material is 30K or more.

[0011] In the semiconductor module of aspect 7 of the embodiment, a plurality of semiconductor units of any one of aspects 1 to 6 are electrically connected in parallel. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a front cross-sectional view of the semiconductor module according to the embodiment. [Diagram 2] FIG. 2 is a side cross-sectional view of the semiconductor module according to the embodiment. [Diagram 3] FIG. 2 is a side cross-sectional view of the semiconductor unit according to the embodiment. [Figure 4] FIG. 1 is a side cross-sectional view of a semiconductor package. [Diagram 5] FIG. 5 is a plan cross-sectional view taken along line VV in FIG. 4 . [Figure 6] FIG. 1 is an explanatory diagram of a short circuit failure in a semiconductor chip. [Figure 7] FIG. [Figure 8] FIG. 4 is an explanatory diagram of a first bonding material and a second bonding material. [Figure 9] FIG. 11 is a front cross-sectional view of a semiconductor module according to a first modified example of the embodiment. [Figure 10] FIG. 11 is a front cross-sectional view of a semiconductor package according to a first modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a semiconductor unit and a semiconductor module according to embodiments will be described with reference to the drawings. Fig. 1 is a front cross-sectional view of a semiconductor module 50 of an embodiment. Fig. 1 is a cross-sectional view taken along line II in Fig. 2. Fig. 2 is a side cross-sectional view of a semiconductor module 50 of an embodiment. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. The semiconductor module 50 includes a plurality of semiconductor units 20.

[0014] 3 is a side cross-sectional view of the semiconductor unit 20 according to the embodiment. The semiconductor unit 20 includes a semiconductor package 10. Fig. 4 is a side cross-sectional view of the semiconductor package 10. Fig. 5 is a plan cross-sectional view taken along line VV in Fig. 4. As shown in Fig. 4, the semiconductor package 10 has a semiconductor chip 15, a first conductive member 11, a second conductive member 12, an intermediate member 16, and a first insulating member 18.

[0015] In the present application, the Z direction, X direction, and Y direction of the Cartesian coordinate system are defined as follows. The Z direction is the direction in which the first conductive member 11, the semiconductor chip 15, and the second conductive member 12 are aligned. The -Z side (first side) is the first conductive member 11 side of the semiconductor chip 15. The +Z side (second side) is the opposite side to the -Z side, which is the second conductive member 12 side of the semiconductor chip 15. The X direction is the direction in which the pair of semiconductor chips 15 are aligned. The Y direction is a direction perpendicular to the Z direction and the X direction. For example, the Z direction is the vertical direction, the -Z side is the lower side, and the +Z side is the upper side. For example, the X direction and the Y direction are horizontal directions.

[0016] The semiconductor chip 15 is formed in a rectangular plate shape with the thickness direction being in the Z direction. The semiconductor chip 15 is, for example, a transistor element such as an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), or a diode element such as an FRD (Fast Recovery Diode). A single semiconductor package 10 may include a plurality of semiconductor chips 15. The semiconductor package 10 shown in FIG. 4 includes a pair of semiconductor chips 15. The pair of semiconductor chips 15 may be either a transistor element or a diode element, or both.

[0017] For example, the semiconductor chip 15 is an IGBT. As shown in Fig. 5, an emitter electrode E and a gate electrode G are formed on the surface on the +Z side of the semiconductor chip 15. Although not shown in Fig. 5, a collector electrode is formed on the surface on the -Z side of the semiconductor chip 15. When the semiconductor chip 15 is a MOSFET, a source electrode and a gate electrode are formed on the surface on the +Z side, and a drain electrode is formed on the surface on the -Z side.

[0018] A signal terminal 17 is connected to the gate electrode G. The signal terminal 17 is drawn out to the outside of the semiconductor package 10. If the semiconductor chip 15 is a diode element and does not have a gate electrode G, the signal terminal 17 does not need to be provided.

[0019] The first conductive member 11, the second conductive member 12, and the intermediate member 16 are formed of a metal material (e.g., copper or aluminum) having high electrical conductivity and thermal conductivity. As shown in Fig. 4, the first conductive member 11 and the second conductive member 12 are formed in a rectangular plate shape with the Z direction as the thickness direction. The first conductive member 11 and the second conductive member 12 are formed to have the same size in the Z direction, the X direction, and the Y direction.

[0020] The first conductive member 11 is disposed on the −Z side of the pair of semiconductor chips 15. The first conductive member 11 is connected to the collector electrode of the semiconductor chip 15 and is electrically connected to the semiconductor chip 15. The second conductive member 12 is disposed on the +Z side of the pair of semiconductor chips 15. A pair of intermediate members 16 are disposed between the second conductive member 12 and the pair of semiconductor chips 15. The intermediate members 16 are connected to the second conductive member 12 and the emitter electrodes E of the semiconductor chips 15. The second conductive member 12 is electrically connected to the semiconductor chips 15 via the intermediate members 16. The second conductive member 12 and the intermediate members 16 may be formed integrally. The semiconductor package 10 does not need to include the intermediate member 16. In this case, the second conductive member 12 is connected to the emitter electrode E of the semiconductor chip 15 and is electrically connected to the semiconductor chip 15.

[0021] The first insulating member 18 is formed of a material having electrical insulation properties (for example, a thermosetting resin such as an epoxy resin). The first insulating member 18 is formed by vacuum molding or the like. The first insulating member 18 seals the semiconductor chip 15, the first conductive member 11, the second conductive member 12, and the intermediate member 16, except for a part of the first conductive member 11 and a part of the second conductive member 12. A part of the first conductive member 11 is a surface on the -Z side of the first conductive member 11. A part of the second conductive member 12 is a surface on the +Z side of the second conductive member 12. The first insulating member 18 seals the side surfaces of the semiconductor chip 15, the first conductive member 11, the second conductive member 12, and the intermediate member 16 in the X direction and the Y direction. The first insulating member 18 is filled between the first conductive member 11 and the second conductive member 12 in the Z direction. The first insulating member 18 ensures an insulation potential between the first conductive member 11 and the second conductive member 12.

[0022] 3, the semiconductor unit 20 has, in addition to the above-described semiconductor package 10, a third conductive member 23, a fourth conductive member 24, a case 30, and a second insulating member 28. As shown in FIG. 1, the fourth conductive member 24 has a main body portion 24a and a terminal portion 25.

[0023] The third conductive member 23 and the fourth conductive member 24 are formed of a metal material (e.g., copper or aluminum) having high electrical conductivity and thermal conductivity. As shown in FIG. 3, the main body 24a of the third conductive member 23 and the fourth conductive member 24 is formed in a rectangular plate shape with the Z direction as the thickness direction. The main body 24a of the third conductive member 23 and the fourth conductive member 24 is formed to have the same size in the Z direction, the X direction, and the Y direction. The main body 24a of the third conductive member 23 and the fourth conductive member 24 is larger than the first conductive member 11 and the second conductive member 12 in the Z direction, the X direction, and the Y direction. The first insulating member 18 of the semiconductor package 10 is disposed between the third conductive member 23 protruding from the first conductive member 11 in the X direction and the Y direction and the fourth conductive member 24 protruding from the second conductive member 12 in the X direction and the Y direction.

[0024] The third conductive member 23 is disposed on the −Z side of the first conductive member 11. The third conductive member 23 is conductively connected to the first conductive member 11. The body portion 24a of the fourth conductive member 24 is disposed on the +Z side of the second conductive member 12. The body portion 24a of the fourth conductive member 24 is conductively connected to the second conductive member 12. As shown in Fig. 1, the terminal portion 25 of the fourth conductive member 24 extends from the body portion 24a to one side in the Y direction, then extends to the +Z side, and further extends to one side in the Y direction.

[0025] The case 30 is made of a high-strength metal material (such as stainless steel, iron, or aluminum). The case 30 is formed in a rectangular box shape. The case 30 accommodates the semiconductor package 10, the third conductive member 23, and the main body portion 24a of the fourth conductive member 24 inside and is disposed around these. An opening is formed in a part of the case 30. As shown in FIG. 1, a side opening 35 is formed on one side of the case 30 in the Y direction. A bottom opening 33 is formed on the -Z side of the case 30.

[0026] 3, a bottom plate (first portion) 31 is disposed on the -Z side of the case 30. A bottom opening 33 is formed in the center of the bottom plate 31 in the X and Y directions. The peripheral portions of the bottom plate 31 in the X and Y directions are disposed on the -Z side of the first conductive member 11. A third conductive member 23 is disposed between the first conductive member 11 and the bottom plate 31.

[0027] A top plate (second portion) 32 is disposed on the +Z side of the case 30. The top plate 32 is disposed on the +Z side of the second conductive member 12. The main body portion 24a of the fourth conductive member 24 is disposed between the second conductive member 12 and the top plate 32.

[0028] The case 30 is integrally formed. That is, the bottom plate 31 on the -Z side and the top plate 32 on the +Z side of the case 30 are integrally formed together with the side plates in the X and Y directions. Note that a part of the case 30 may be formed separately and then connected together.

[0029] The second insulating member 28 is formed of a material having electrical insulation properties (for example, a thermosetting resin such as an epoxy resin). The second insulating member 28 is formed by vacuum molding or the like. The second insulating member 28 seals the semiconductor package 10 except for a part of the semiconductor package 10. The part of the semiconductor package 10 is the surface on the -Z side covered by the third conductive member 23 and the surface on the +Z side covered by the fourth conductive member 24. The part of the semiconductor package 10 may be a part used for conductive connection with the cooling member 52 and the top plate 55 (see FIG. 1) described later. The second insulating member 28 seals the semiconductor package 10, the third conductive member 23, and the fourth conductive member 24 except for a part of the third conductive member 23 and a part of the fourth conductive member 24. The part of the third conductive member 23 is the center part of the surface on the -Z side of the third conductive member 23. The part of the fourth conductive member 24 is a terminal part 25 (see FIG. 1). The center of the surface on the -Z side of the third conductive member 23 is exposed to the outside of the semiconductor unit 20 through the opening in the second insulating member 28 and the bottom opening 33 of the case 30 (see FIG. 1). The second insulating member 28 seals the side surfaces in the X direction and Y direction of the semiconductor package 10, the third conductive member 23, and the fourth conductive member 24. The first insulating member 18 and the second insulating member 28 ensure an insulation potential between the third conductive member 23 and the fourth conductive member 24.

[0030] The second insulating member 28 is disposed at least inside the case 30. That is, the second insulating member 28 is disposed between the semiconductor package 10, the third conductive member 23, and the fourth conductive member 24, and the case 30. This ensures an insulation potential between the third conductive member 23 and the fourth conductive member 24, and the case 30. In addition, the second insulating member 28 is also disposed on the outer surface of the case 30. This ensures an insulation potential between objects around the semiconductor unit 20 and the case 30.

[0031] 1 and 2, the semiconductor module 50 has, in addition to the above-described semiconductor unit 20, a cooling member 52, a top plate 55, a substrate 57, and a side wall 58 around the semiconductor unit 20. The semiconductor unit 20 is housed inside a container formed by the cooling member 52, the top plate 55, and the side wall 58.

[0032] The cooling member 52 is formed of a metal material (e.g., copper or aluminum) having high electrical and thermal conductivity. The cooling member 52 is disposed at the end of the semiconductor module 50 on the -Z side. The cooling member 52 has a protrusion 53 and a coolant flow path 54.

[0033] The protrusion 53 protrudes from the surface on the +Z side of the cooling member 52 to the +Z side. The tip of the protrusion 53 is conductively connected to the center of the surface on the -Z side of the third conductive member 23 in the semiconductor unit 20. A bonding material such as solder or a mechanical fastening member such as a bolt is used to connect the protrusion 53 and the third conductive member 23. The cooling member 52 is conductive to the collector electrode of the semiconductor chip 15 via the protrusion 53, the third conductive member 23, and the first conductive member 11 (see FIG. 4). As a result, the cooling member 52 functions as an electrode of the collector potential.

[0034] The coolant flow path 54 is formed inside the cooling member 52. A coolant such as pure water can flow through the coolant flow path 54. As a result, the cooling member 52 cools the semiconductor unit 20 as a whole.

[0035] The top plate 55 is formed of a metal material (e.g., copper or aluminum) having high electrical conductivity and thermal conductivity. The top plate 55 is disposed at the end of the semiconductor module 50 on the +Z side. As shown in FIG. 1, the terminal portion 25 of the fourth conductive member 24 of the semiconductor unit 20 passes through the side opening 35 of the case 30 and extends to the outside of the second insulating member 28. The tip of the terminal portion 25 is electrically connected to the surface of the -Z side of the top plate 55. A joining material such as solder or a mechanical fastening member such as a bolt is used to connect the terminal portion 25 to the top plate 55. The top plate 55 is electrically connected to the emitter electrode of the semiconductor chip 15 via the fourth conductive member 24, the second conductive member 12 (see FIG. 4), and the intermediate member 16. As a result, the top plate 55 functions as an electrode of the emitter potential.

[0036] The semiconductor module 50 has a plurality of semiconductor units 20. As described above, the plurality of semiconductor units 20 are conductively connected to the cooling member 52 and the top plate 55. As a result, the plurality of semiconductor units 20 are electrically connected in parallel in the semiconductor module 50. The cooling member 52 and the top plate 55 function as a common electrode for the plurality of semiconductor units 20.

[0037] The substrate 57 is disposed between the semiconductor unit 20 and the top plate 55. The signal terminal 17 connected to the gate electrode of the semiconductor chip 15 passes through the side opening 35 of the case 30 and extends to the outside of the second insulating member 28. The tip of the signal terminal 17 is connected to the substrate 57. This controls the switching of the semiconductor chip 15. The side walls 58 are disposed at the ends of the semiconductor module 50 in the X and Y directions. The side walls 58 connect the cooling member 52 and the top plate 55 together.

[0038] It is necessary to carry out tests on the semiconductor chip 15 that conform to the operating conditions, such as conduction and switching, as well as performance tests on the withstand voltage and maximum current. However, the withstand voltage performance of the semiconductor chip 15 varies greatly depending on the sealing state between the electrodes. For this reason, it is conceivable to carry out performance tests on the semiconductor chip 15, such as withstand voltage, using the completed semiconductor module 50 or semiconductor unit 20. However, if a performance defect is detected in the semiconductor chip 15 in these completed products, the components other than the semiconductor chip 15 included in the completed product and the manufacturing process up to completion will be wasted.

[0039] The semiconductor unit 20 of the embodiment includes a semiconductor package 10. The semiconductor package 10 has a first conductive member 11, a second conductive member 12, and a first insulating member 18 in addition to a semiconductor chip 15. The first conductive member 11 and the second conductive member 12 allow current to flow to the semiconductor chip 15. The first insulating member 18 ensures an insulating potential between the first conductive member 11 and the second conductive member 12. Therefore, before entering the manufacturing process of the semiconductor unit 20, a performance test such as a withstand voltage test of the semiconductor chip 15 can be performed using the semiconductor package 10. The semiconductor package 10 has a small number of components and a simple manufacturing process. Therefore, even if a performance defect of the semiconductor chip 15 is detected in the semiconductor package 10, there is little waste of the components and manufacturing process. Therefore, the yield of the semiconductor unit 20 is improved, and the cost of the semiconductor unit 20 can be reduced.

[0040] FIG. 6 is an explanatory diagram of a short circuit failure of the semiconductor chip 15. One of the multiple semiconductor chips 15 included in the semiconductor module 50 may short circuit. The current flowing through the semiconductor module 50 is concentrated on the semiconductor chip 15 that has the short circuit failure. When an overcurrent flows through the semiconductor chip 15, a part of the semiconductor chip 15 melts and vaporizes due to Joule heat. In addition, the bonding material (solder, etc.) that bonds the semiconductor chip 15 to the first conductive member 11 and the intermediate member 16 melts and vaporizes. This causes the pressure in the vicinity of the semiconductor chip 15 to increase. Then, as shown in FIG. 6, a crack C along the XY plane occurs in the semiconductor chip 15 and the first insulating member 18, and the semiconductor package 10 breaks in the Z direction.

[0041] If the entire semiconductor unit 20 breaks due to the breakage of the semiconductor package 10, the conduction of the short-circuited semiconductor chip 15 is interrupted. If one of the multiple semiconductor units 20 included in the semiconductor module 50 breaks explosively, there is a possibility that the other semiconductor units 20 will break in conjunction. If all the semiconductor units 20 included in the semiconductor module 50 break, the conduction of the semiconductor module 50 is interrupted. Even if all the semiconductor units 20 do not break, the semiconductor module 50 including the short-circuited semiconductor chip 15 cannot perform switching, so if the conductive members of the short-circuited semiconductor unit 20 are separated in the Z direction and a conduction path is not formed, the conduction of the semiconductor module 50 is interrupted. As a result, the operation of the power conversion device in which multiple semiconductor modules 50 are connected in series cannot be continued.

[0042] The semiconductor unit 20 of the embodiment has a case 30 that houses the semiconductor package 10. A bottom plate 31 of the case 30 is disposed on the -Z side of the first conductive member 11. A top plate 32 of the case 30 is disposed on the +Z side of the second conductive member 12. The bottom plate 31 and the top plate 32 of the case 30 are integrally formed. The strength of the constituent material of the case 30 is greater than the strength of the constituent material of the first insulating member 18 and the strength of the constituent material of the second insulating member 28.

[0043] When the semiconductor package 10 breaks, the first conductive member 11 and the second conductive member 12 move apart in the Z direction. The bottom plate 31 and the top plate 32 of the case 30, which are integrally formed, prevent the first conductive member 11 and the second conductive member 12 from moving apart in the Z direction. Even if the first insulating member 18 and the second insulating member 28 break, the case 30 is unlikely to break. This prevents the entire semiconductor unit 20 from breaking, and maintains the continuity of the short-circuited semiconductor chip 15. The semiconductor module 50 including the short-circuited semiconductor chip 15 cannot perform switching. However, if the continuity of the semiconductor module 50 is maintained, the operation of the power conversion device can be continued by performing switching in the other semiconductor modules 50 connected in series.

[0044] In this way, the case 30 prevents breakage of the semiconductor unit 20. Therefore, it is not necessary to constantly apply pressure in the Z direction to the semiconductor unit 20 to prevent breakage of the semiconductor unit 20. Therefore, a structure that constantly applies pressure in the Z direction to the semiconductor unit 20 is not necessary, and the cost of the semiconductor unit 20 can be reduced.

[0045] In the semiconductor unit 20 of the embodiment, the first insulating member 18 constituting the semiconductor package 10 and the second insulating member 28 sealing the semiconductor package 10 are separate members. If the bonding strength of the interface between the first insulating member 18 and the second insulating member 28 is small, the deformation suppression effect of the case 30 may not be sufficient for the first insulating member 18 and the semiconductor package 10.

[0046] In the semiconductor unit 20 of the embodiment, the first insulating member 18 and the second insulating member 28 are mainly made of the same material. For example, the main component of the first insulating member 18 and the second insulating member 28 is epoxy resin. This increases the bonding strength of the interface between the first insulating member 18 and the second insulating member 28.

[0047] FIG. 7 is an explanatory diagram of the interface bonding strength test. The first test piece 18t was molded from the same material as the first insulating member 18, and the third test piece mt was made from the same material as the conductive member. The second test piece 28t was molded between the two from the same material as the second insulating member 28. A load was applied to the first test piece 18t and the third test piece mt so that a shear force acts on the interface between the adjacent test pieces. As a result, peeling occurred at the interface between the second test piece 28t and the third test piece mt. This confirmed that the bonding strength of the interface between the first insulating member 18 and the second insulating member 28 is greater than the bonding strength of the interface between each of them and the conductive member. This allows the first insulating member 18 and the second insulating member 28 to deform together even if a crack occurs during a short circuit failure of the semiconductor chip 15. The deformation suppression effect of the case 30 can be fully applied to the first insulating member 18 and the semiconductor package 10.

[0048] As described above, the first insulating member 18 and the second insulating member 28 are separate members. As the temperature of the semiconductor unit 20 changes, stress occurs at the interface between the first insulating member 18 and the second insulating member 28 due to the difference in linear expansion coefficient between the two. If the interface stress becomes large, peeling may occur at the interface between the two. The limit of the difference in linear expansion coefficient between the first insulating member 18 and the second insulating member 28 will be considered below.

[0049] The relevant physical quantities are defined as follows: Linear expansion coefficient of the first insulating member 18: α1 Linear expansion coefficient of the second insulating member 28: α2 Difference in linear expansion coefficient between the first insulating member 18 and the second insulating member 28: Δα=α1-α2 Elastic modulus of the first insulating member 18 and the second insulating member 28: E Temperature change: ΔT Elongation rate of the first insulating member 18: ΔL1=α1×ΔT Elongation rate of the second insulating member 28: ΔL2=α2×ΔT The difference in elongation rate between the first insulating member 18 and the second insulating member 28: ΔL1-ΔL2=Δα×ΔT Interface strain between the first insulating member 18 and the second insulating member 28: Δα×ΔT Interface stress between the first insulating member 18 and the second insulating member 28: Δα×ΔT×E

[0050] If the temperature change range is -40 to 150°C, then ΔT = 190K. The elastic modulus E of the epoxy resin material constituting the first insulating member 18 and the second insulating member 28 is about 15 GPa. The rupture stress of the epoxy resin material is assumed to be about 100 MPa. The allowable value σa of the interface stress of the epoxy resin material is set to 20 MPa, which is 20% of the rupture stress. The interface stress Δα × ΔT × E between the first insulating member 18 and the second insulating member 28 needs to be smaller than the allowable value σa. At this time, the linear expansion coefficient difference Δα between the first insulating member 18 and the second insulating member 28 satisfies the following mathematical formula (1). Δα<σa / (ΔT×E) <20MPa / (190K×15GPa) <7.0×10 -6 (1)

[0051] The linear expansion coefficient of the resin material constituting the first insulating member 18 and the second insulating member 28 is assumed to be designed to be equivalent to that of the metals copper or aluminum. The linear expansion coefficient αCu of the resin material equivalent to that of copper is 15×10 at room temperature. -6 The linear expansion coefficient αAl of resin materials equivalent to aluminum is about 23×10 -6 The linear expansion coefficient α1 of the first insulating member 18 and the linear expansion coefficient α2 of the second insulating member 28, whichever is larger, is referred to as the large coefficient, and the smaller is referred to as the small coefficient. When the large coefficient is αCu, the linear expansion coefficient difference Δα that satisfies the formula (1) is about 47% of the large coefficient αCu. When the large coefficient is αAl, the linear expansion coefficient difference Δα that satisfies the formula (1) is about 30% of the large coefficient αAl. Therefore, if the linear expansion coefficient difference Δα is kept below 50% of the large coefficient, it is possible to suppress the interface peeling between the first insulating member 18 and the second insulating member 28 due to temperature change. It is particularly preferable to keep the linear expansion coefficient difference Δα below 30% of the large coefficient.

[0052] 8 is an explanatory diagram of the first bonding material A and the second bonding material B. The first bonding material A is used for conductive connection of the components of the semiconductor package 10. That is, the first bonding material A is used for conductive connection between the collector electrode of the semiconductor chip 15 and the first conductive member 11, between the emitter electrode of the semiconductor chip 15 and the intermediate member 16, and between the intermediate member 16 and the second conductive member 12.

[0053] The second bonding material B is used for conductive connection of the components of the semiconductor unit 20. That is, the second bonding material B is used for conductive connection between the third conductive member 23 and the first conductive member 11 of the semiconductor package 10, and for conductive connection between the fourth conductive member 24 and the second conductive member 12 of the semiconductor package 10.

[0054] The first bonding material A and the second bonding material B are materials such as solder that are bonded by thermal melting. After the first bonding material A is thermally melted to form the semiconductor package 10, the second bonding material B is thermally melted to form the semiconductor unit 20 including the semiconductor package 10. The melting point of the first bonding material A is higher than the melting point of the second bonding material B. As a result, when the second bonding material B is thermally melted to form the semiconductor unit 20, the first bonding material A is not thermally melted. Therefore, the conductive connection between the components of the semiconductor package 10 can be maintained.

[0055] For example, a lead-based solder having a relatively high melting point can be used as the first bonding material A. A tin-based solder having a relatively low melting point can be used as the second bonding material B. The difference between the melting point of the first bonding material A and the melting point of the second bonding material B is preferably 30K or more. This makes it possible to avoid temperature interference between the bonding process of the semiconductor package 10 and the bonding process of the semiconductor unit 20.

[0056] As described above in detail, the semiconductor unit 20 of the embodiment includes the semiconductor chip 15, the first conductive member 11, the second conductive member 12, the first insulating member 18, the case 30, and the second insulating member 28. The first conductive member 11 is disposed on the -Z side of the semiconductor chip 15 and is electrically connected to the semiconductor chip 15. The opposite side of the -Z side is the +Z side. The second conductive member 12 is disposed on the +Z side of the semiconductor chip 15 and is electrically connected to the semiconductor chip 15. The first insulating member 18 seals the semiconductor chip 15, the first conductive member 11, and the second conductive member 12, except for a part of the first conductive member 11 and a part of the second conductive member 12. The case 30 is disposed around the semiconductor package 10 including the semiconductor chip 15, the first conductive member 11, the second conductive member 12, and the first insulating member 18. In the case 30, a bottom plate 31 disposed on the -Z side of the first conductive member 11 and a top plate 32 disposed on the +Z side of the second conductive member 12 are integral with each other. The second insulating member 28 is disposed inside the case 30 and seals the semiconductor package 10 except for a portion of the semiconductor package 10. The strength of the case 30 is greater than the strength of the first insulating member 18 and the strength of the second insulating member 28.

[0057] The semiconductor unit 20 further has a third conductive member 23 and a fourth conductive member 24. The third conductive member 23 is disposed between the first conductive member 11 and the bottom plate 31 of the case 30, and is electrically connected to the first conductive member 11. The fourth conductive member 24 is disposed between the second conductive member 12 and the top plate 32 of the case 30, and is electrically connected to the second conductive member 12. The second insulating member 28 seals the semiconductor package 10, the third conductive member 23, and the fourth conductive member 24, except for a portion of the third conductive member 23 and a portion of the fourth conductive member 24.

[0058] According to this configuration, before constructing the entire semiconductor unit 20, it is possible to perform performance tests such as voltage resistance tests of the semiconductor chip 15 using the semiconductor package 10. Even if a performance defect of the semiconductor chip 15 is detected in the semiconductor package 10, there is little waste of components and manufacturing processes. Therefore, the yield of the semiconductor unit 20 is improved, and the cost of the semiconductor unit 20 can be reduced.

[0059] A short circuit failure of the semiconductor chip 15 may cause the semiconductor package 10 to break. Even in this case, the case 30 prevents the semiconductor unit 20 from breaking. Therefore, it is not necessary to constantly apply pressure in the Z direction to the semiconductor unit 20 to prevent the semiconductor unit 20 from breaking. Therefore, a structure that constantly applies pressure in the Z direction to the semiconductor unit 20 is not necessary, and the cost of the semiconductor unit 20 can be reduced.

[0060] The first insulating member 18 and the second insulating member 28 are mainly made of the same material. This increases the bonding strength at the interface between the first insulating member 18 and the second insulating member 28. The deformation suppression effect of the case 30 can be made to act sufficiently on the first insulating member 18 and the semiconductor package 10.

[0061] The larger of the linear expansion coefficient α1 of the first insulating member 18 and the linear expansion coefficient α2 of the second insulating member 28 is referred to as the large coefficient, and the smaller of the linear expansion coefficient α2 is referred to as the small coefficient. The difference between the large coefficient and the small coefficient is less than 50% of the large coefficient. This suppresses peeling at the interface between the first insulating member 18 and the second insulating member 28 due to the difference in linear expansion coefficient between the two.

[0062] The semiconductor unit 20 further includes a first bonding material A and a second bonding material B. The first bonding material A provides conductive connection between the components of the semiconductor package 10. The second bonding material B provides conductive connection between the semiconductor package 10 and the third conductive member 23 and the fourth conductive member 24. The melting point of the first bonding material A is higher than the melting point of the second bonding material B. As a result, when the second bonding material B is thermally melted to form the semiconductor unit 20, the first bonding material A included in the semiconductor package 10 is not thermally melted. Therefore, the conductive connection between the components of the semiconductor package 10 can be maintained.

[0063] The difference between the melting point of the first bonding material A and the melting point of the second bonding material B is 30K or more. This makes it possible to avoid temperature interference between the bonding process of the semiconductor package 10 and the bonding process of the semiconductor unit 20.

[0064] In the semiconductor module 50 of the embodiment, the above-described multiple semiconductor units 20 are electrically connected in parallel. This makes it possible to configure the semiconductor module 50 capable of switching a large current. By including the above-described semiconductor unit 20, the cost of the semiconductor module 50 can be reduced.

[0065] A first modified example of the embodiment will be described. Fig. 9 is a front cross-sectional view of a semiconductor module 50 according to a first modified example of the embodiment. The semiconductor unit 20 according to the embodiment shown in Fig. 1 has a third conductive member 23 and a fourth conductive member 24. In contrast, the semiconductor unit 20 according to the first modified example shown in Fig. 9 does not have the third conductive member 23 and the fourth conductive member 24. Descriptions of the first modified example that are similar to the embodiment may be omitted.

[0066] The semiconductor unit 20 of the first modified example includes a semiconductor package 10, a conductive terminal 26, a case 30, and a second insulating member . 10 is a front cross-sectional view of a semiconductor package 10 of a first modified example. The second conductive member 12 of the semiconductor package 10 has an extension portion 12a extending to one side in the Y direction from the first conductive member 11. The first insulating member 18 of the semiconductor package 10 encapsulates the semiconductor chip 15, the first conductive member 11, the second conductive member 12, and the intermediate member 16, except for a part of the first conductive member 11 and a part of the second conductive member 12. The part of the second conductive member 12 is the surface on the +Z side of the second conductive member 12 and the extension portion 12a.

[0067] As shown in FIG. 9, the second insulating member 28 of the semiconductor unit 20 seals the semiconductor package 10 except for a part of the semiconductor package 10. The part of the semiconductor package 10 is a central portion of the surface on the -Z side of the first conductive member 11 and an extension portion 12a of the second conductive member 12. The central portion of the surface on the -Z side of the first conductive member 11 is exposed to the outside of the semiconductor unit 20 through an opening of the second insulating member 28 and a bottom opening 33 of the case 30. The central portion of the surface on the -Z side of the first conductive member 11 is conductively connected to a protrusion 53 of a cooling member 52 of the semiconductor module 50. The extension portion 12a of the second conductive member 12 passes through a side opening 35 of the case 30 and extends to the outside of the second insulating member 28.

[0068] The conductive terminal 26 is formed of a metal material (e.g., copper or aluminum) having high electrical conductivity and thermal conductivity. The conductive terminal 26 is formed by bending a metal plate. The center of the conductive terminal 26 is parallel to the XZ plane. The +Z end and the -Z end of the conductive terminal 26 are parallel to the XY plane. The +Z end of the conductive terminal 26 is connected to the top plate 55 of the semiconductor module 50. The -Z end of the conductive terminal 26 is conductively connected to the extension portion 12a of the second conductive member 12. A bonding material such as solder or a mechanical fastening member such as a bolt is used to connect the conductive terminal 26 to the top plate 55 and the extension portion 12a.

[0069] The semiconductor unit 20 and the semiconductor module 50 of the first modified example have the same effects as those of the above-described embodiment. As described above, the semiconductor unit 20 and the semiconductor module 50 of the first modification example do not have the third conductive member 23 and the fourth conductive member 24. This reduces the number of components in the semiconductor unit 20 and the semiconductor module 50, thereby suppressing costs. In addition, the semiconductor unit 20 and the semiconductor module 50 are made smaller in size in the Z direction.

[0070] According to at least one of the embodiments described above, the semiconductor package 10 includes the semiconductor chip 15, the first conductive member 11, the second conductive member 12, and the first insulating member 18. This improves the yield of the semiconductor unit 20 even if a performance defect of the semiconductor chip 15 is detected. Therefore, the cost of the semiconductor unit 20 can be reduced.

[0071] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0072] A...first bonding material, B...second bonding material, 10...semiconductor package, 11...first conductive member, 12...second conductive member, 15...semiconductor chip, 18...first insulating member, 20...semiconductor unit, 23...third conductive member, 24...fourth conductive member, 28...second insulating member, 30...case, 31...bottom plate (first part), 32...top plate (second part), 50...semiconductor module.

Claims

1. A semiconductor chip; a first conductive member disposed on a first side of the semiconductor chip and electrically connected to the semiconductor chip; a second conductive member that is disposed on the second side of the semiconductor chip and is electrically connected to the semiconductor chip, when the side opposite the first side is defined as a second side; a first insulating member that seals the semiconductor chip, the first conductive member, and the second conductive member except for a portion of the first conductive member and a portion of the second conductive member; a case disposed around a semiconductor package including the semiconductor chip, the first conductive member, the second conductive member, and the first insulating member, the case being integrated with a first portion disposed on the first side of the first conductive member and a second portion disposed on the second side of the second conductive member; a second insulating member disposed inside the case and sealing the semiconductor package except for a portion of the semiconductor package; The strength of the case is greater than the strength of the first insulating member and the strength of the second insulating member. Semiconductor unit.

2. a third conductive member disposed between the first conductive member and the first portion of the case and electrically connected to the first conductive member; a fourth conductive member disposed between the second conductive member and the second portion of the case and electrically connected to the second conductive member; the second insulating member seals the semiconductor package, the third conductive member, and the fourth conductive member except for a portion of the third conductive member and a portion of the fourth conductive member; The semiconductor unit according to claim 1 .

3. The first insulating member and the second insulating member are mainly composed of the same material. The semiconductor unit according to claim 1 .

4. a larger linear expansion coefficient of the first insulating member and a smaller linear expansion coefficient of the second insulating member are defined as a large coefficient and a small coefficient, respectively, and a difference between the large coefficient and the small coefficient is smaller than 50% of the large coefficient. The semiconductor unit according to claim 1 .

5. a first bonding material that electrically connects components of the semiconductor package; a second bonding material that electrically connects the semiconductor package to the third conductive member and the fourth conductive member, The melting point of the first bonding material is higher than the melting point of the second bonding material. The semiconductor unit according to claim 2 .

6. The difference between the melting point of the first bonding material and the melting point of the second bonding material is 30K or more. The semiconductor unit according to claim 5 .

7. A plurality of semiconductor units according to claim 1 or 2 are electrically connected in parallel. Semiconductor module.

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