Lead frame wiring structure and semiconductor module

Abstract

The present invention reduces stress concentration on semiconductor elements. The lead frame wiring (7) has: a first joint (71) whose solder is joined to a semiconductor element arranged on one side; a joint (72) whose solder is joined to a connection object arranged on the other side; and a connecting portion (73) that connects the joint (71) and the joint (72), the connecting portion having: a connecting face portion (73a); a first leg portion (73b) extending from an end portion on one side of the connecting face portion to the first joint portion side; and a second leg portion (73c) extending from an end portion on the other side of the connecting face portion to the second joint portion side. The first leg portion is connected to a part of the outer edge portion of the first joint portion arranged between the end portion on one side and the end portion on the other side.

Description

Technical Field

[0001] The present invention relates to a lead frame wiring structure and a semiconductor module. Background Art

[0002] Semiconductor modules are equipped with semiconductor elements such as IGBT (Insulated Gate Bipolar Transistor), power MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and FWD (Free Wheeling Diode), and are used in industrial applications such as motor drive control converters in elevators. In recent years, they have also been widely used in automotive motor drive control converters. In automotive motor drive control converters, they are required to be small and lightweight in order to reduce fuel consumption, and they are required to have long-term reliability in high-temperature working environments in order to be placed in the engine room.

[0003] In the past, in order to meet the requirements of such small size and light weight and the requirements of long-term reliability in high temperature working environment, a semiconductor module that connects a semiconductor chip (semiconductor element) and an electrode pattern by using a lead frame wiring method has been proposed (for example, refer to Patent Document 1). The lead frame wiring method refers to a method of supporting and fixing a semiconductor chip and connecting the semiconductor chip and an electrode pattern by using a lead frame wiring formed by die processing of a metal plate.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-46164 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] Usually, an L-shaped bending portion is provided at both ends of the lead frame wiring, and the lower surface of the horizontal plane of the bending portion is joined to the upper surface of the semiconductor chip and the electrode pattern by solder. When solder is used to join to the semiconductor chip, etc., the solder may climb to the drooping surface of the bending portion. When the solder climbs to the drooping surface of the bending portion, the stress (strain) caused by thermal deformation will be concentrated on the upper surface of the semiconductor chip, and the semiconductor chip may be damaged.

[0009] The present invention has been made in view of the above-mentioned problems, and one object of the present invention is to provide a lead frame wiring structure and a semiconductor module capable of reducing stress concentration on a semiconductor element.

[0010] Solutions for solving problems

[0011] The present embodiment provides a lead frame wiring structure, which electrically connects a semiconductor element arranged on one side of the lead frame wiring and a connection object arranged on the other side of the lead frame wiring, and the lead frame wiring structure is characterized in that the lead frame wiring structure has: a first bonding portion, which is solder-bonded to the semiconductor element; a second bonding portion, which is separated from the first bonding portion and solder-bonded to the connection object; and a connecting portion, which connects the first bonding portion and the second bonding portion, and the connecting portion has: a connecting face portion, which is separated from the first bonding portion and the second bonding portion in the up and down directions; a first leg portion, which extends from the end of the one side of the connecting face portion to the first bonding portion side; and a second leg portion, which extends from the end of the other side of the connecting face portion to the second bonding portion side, and the first leg portion is connected to a part of the outer edge portion of the first bonding portion, which is arranged between the end of the one side and the end of the other side in the first bonding portion.

[0012] Effects of the Invention

[0013] According to the present invention, stress concentration on a semiconductor chip can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a cross-sectional view showing the structure of a semiconductor module to which the lead frame wiring structure of the present embodiment is applied.

[0015] Figure 2 It is a plan view of a lead frame wiring included in the semiconductor module of the present embodiment.

[0016] Figure 3 It is a perspective view of the lead frame wiring according to the present embodiment.

[0017] Figure 4 This is a development view of the lead frame wiring according to the present embodiment before processing.

[0018] Figure 5 It is a perspective view showing a state of the lead frame wiring process according to the present embodiment.

[0019] Figure 6 It is a perspective view showing a state of the lead frame wiring process according to the present embodiment.

[0020] Figure 7It is an explanatory diagram of the positional relationship between the lead frame wiring and the semiconductor chip according to the present embodiment.

[0021] Figure 8 It is a perspective view of a lead frame wiring according to a modification of the present embodiment and a development view before processing.

[0022] Fig. 9 It is a perspective view of a lead frame wiring according to a modification of the present embodiment and a development view before processing.

[0023] Fig.10 This is an enlarged schematic diagram of a junction portion of a conventional lead frame wiring with respect to a semiconductor element. DETAILED DESCRIPTION

[0024] In semiconductor modules used in automotive motor drive control converters, etc., in order to meet the requirements of small size and light weight, and the requirements of long-term reliability in high-temperature working environments, a lead frame wiring method is known that connects the semiconductor chip and the electrode pattern using lead frame wiring. Fig.10 The structure of a conventional lead frame wiring will be described. Fig.10 This is an enlarged schematic diagram of a junction portion of a conventional lead frame wiring with respect to a semiconductor element.

[0025] Usually, if Fig.10 As shown, the portion of the lead frame wiring connected to the semiconductor chip or the like is provided with a hanging portion 101 extending substantially vertically when viewed from the side, and a horizontal portion 102 bent in an L-shape and extending horizontally from the end of the hanging portion 101. The lower surface of the horizontal portion 102 of the lead frame wiring is bonded to the upper surface of the semiconductor chip 103 by solder 104.

[0026] The solder 104 disposed below the horizontal surface portion 102 is evenly spread out on the lower surface of the horizontal surface portion 102 to facilitate bonding. On the other hand, the solder 104 disposed below the drooping surface portion 101 may climb to the side surface 101a of the drooping surface portion 101 disposed on the side opposite to the horizontal surface portion 102. In the semiconductor chip 103, thermal deformation is repeatedly generated as the power is repeatedly turned on and off. The solder 104 is more concentrated in the portion where the climbing portion 104a of the solder 104 is generated than in other portions. Therefore, the stress (strain) caused by thermal deformation is concentrated on the upper surface of the semiconductor chip 103, which may cause damage to the semiconductor chip 103.

[0027] The inventors of the present invention have noticed that the rounded corner portion (Japanese: R-shaped portion) 101b formed by bending the lead frame wiring is the main cause of the solder climbing phenomenon. They have also found that reducing the surface area of ​​the rounded corner portion 101b formed by bending can suppress the occurrence of the solder climbing phenomenon and help reduce stress concentration on the semiconductor chip, thereby conceiving of the present invention.

[0028] That is, the gist of the present invention is a lead frame wiring structure, which comprises: a first joining portion, whose solder is joined to a semiconductor element arranged on one side of the lead frame wiring; a second joining portion, whose solder is joined to a connection object arranged on the other side of the lead frame wiring; and a connecting portion, which connects the first joining portion and the second joining portion, and a leg portion extending in the up-down direction and joined to the first joining portion is provided in the connecting portion, and the leg portion is connected to a part of the outer edge portion arranged between the end on one side and the end on the other side of the first joining portion.

[0029] According to the present invention, the leg is partially connected to the outer edge portion arranged between the end on one side and the end on the other side of the first joint. Therefore, the contact area between the leg and the solder for joining the first joint to the semiconductor element can be reduced. Thus, even in the case where the leg is formed by bending, the surface area of ​​the fillet-shaped portion formed by the bending process can be reduced, so that the occurrence of solder climbing phenomenon can be suppressed and the stress concentration relative to the semiconductor chip can be reduced.

[0030] Hereinafter, the structure of the semiconductor module according to the present embodiment will be described with reference to the drawings. Figure 1 1 is a cross-sectional view showing the structure of a semiconductor module 1 to which the lead frame wiring structure of the present embodiment is applied. Figure 1 The vertical direction and the horizontal direction shown are explained as the vertical direction and the horizontal direction of the semiconductor module 1, respectively. However, the vertical direction used in this specification is not necessarily limited to the gravity direction.

[0031] like Figure 1 As shown, the semiconductor module 1 includes an insulating substrate 3 having electrode patterns 2 (2a to 2c) on the upper and lower surfaces. Separately arranged electrode patterns 2a and 2b are provided on the upper surface of the insulating substrate 3. An electrode pattern 2c is provided on the lower surface of the insulating substrate 3, and the electrode pattern 2c is arranged on the entire surface of the insulating substrate 3. For example, the electrode patterns 2a to 2c are composed of metal foils such as copper (Cu) and aluminum (Al), metal plates, etc. A plating layer such as nickel (Ni) may also be provided on the electrode pattern 2. Hereinafter, for the convenience of explanation, the insulating substrate 3 having electrode patterns 2 on the upper and lower surfaces is referred to as a laminated substrate 4.

[0032] A semiconductor chip 6 is bonded to the upper surface of the electrode pattern 2a by means of a solder 5a. For example, the semiconductor chip 6 is composed of semiconductor elements such as switching elements such as IGBT (Insulated Gate Bipolar Transistor), power MOSFET (Metal Oxide Semiconductor Field Effect Transistor), diodes such as FWD (Free Wheeling Diode), etc. The semiconductor chip 6 can also be composed of semiconductor elements such as RC (Reverse Conducting: Reverse Conducting)-IGBT formed by integrating IGBT and FWD, and RB (Reverse Blocking: Reverse Blocking)-IGBT with sufficient withstand voltage against reverse bias. The semiconductor chip 6 can be formed using a semiconductor substrate such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), etc.

[0033] Lead frame wiring (hereinafter referred to as "lead frame") 7 is joined to the upper surface of the semiconductor chip 6 and the upper surface of the electrode pattern 2b as wiring for electrical connection. The lead frame 7 is formed by bending a metal plate, and has a shape extending roughly in the left-right direction and bent downward at both ends. A joining portion 71 of the lead frame 7 is joined to the upper surface of the semiconductor chip 6 by means of solder 5b. Another joining portion 72 of the lead frame 7 is joined to the upper surface of the electrode pattern 2b by means of solder 5c. These joining portions 71 and 72 are connected by a connecting portion 73. In addition, the structure of the lead frame 7 will be described later. The semiconductor chip 6 constitutes an example of a semiconductor element, and the electrode pattern 2b constitutes an example of a connection object. The connection object of the joining portion 72 is not limited to the electrode pattern 2b, but also includes a structure such as an external terminal of the semiconductor module 1. The lead frame 7 is configured on one side ( Figure 1 The semiconductor chip 6 is arranged on the left side (shown) and the other side ( Figure 1 The electrode pattern 2b on the right side of the diagram is electrically connected.

[0034] A metal substrate 8 is bonded to the lower surface of the electrode pattern 2c by means of a solder 5d. In other words, a laminated substrate 4 is bonded to the upper surface of the metal substrate 8 by means of a solder 5d. The metal substrate 8 serves to dissipate heat generated by the driving of the semiconductor module 1. The metal substrate 8 may also have a heat sink not shown. Hereinafter, for convenience of explanation, a component in which the metal substrate 8, the laminated substrate 4, and the semiconductor chip 6 are laminated is referred to as a laminated assembly 9. A resin case 10 is bonded to the laminated assembly 9. For example, the resin case 10 is bonded to the laminated assembly 9 by an adhesive such as silicon.

[0035] A metal terminal 11 is embedded in a part of the resin housing 10. The metal terminal 11 extends in the up-down direction and penetrates the resin housing 10. The lower end 11a of the metal terminal 11 is exposed in the resin housing 10. The upper end 11b of the metal terminal 11 protrudes to the outside of the resin housing 10. A metal lead 12 is connected between the part of the metal terminal 11 exposed in the resin housing 10 and the upper surface of the semiconductor chip 6. In the state where the components are arranged in this way, the inside of the resin housing 10 is filled with a sealing resin 13 composed of a hard resin such as epoxy resin or silicone gel, etc., in order to insulate and protect the semiconductor chip 6.

[0036] Here, refer to Figure 2 and Figure 3 The structure of the lead frame 7 included in the semiconductor module 1 of the present embodiment will be described. Figure 2 It is a plan view of the lead frame 7 included in the semiconductor module 1 according to the present embodiment. Figure 3 1 is a perspective view of the lead frame 7 of the present embodiment. The lead frame 7 is formed by bending (die processing) a metal plate having a uniform thickness dimension as a whole.

[0037] like Figure 2 and Figure 3 As shown, the lead frame 7 is constituted to include joints 71 and 72 constituted by substantially flat surfaces and a connecting portion 73 connecting these joints 71 and 72. The joint 71 constitutes an example of a first joint, and the joint 72 constitutes an example of a second joint. In addition, the connecting portion 73 constitutes an example of a connecting portion. The joint 71 and the joint 72 are arranged separately in the left-right direction. In addition, the joints 71, 72 and the connecting portion 73 can be substantially flat plate shapes. In addition, the corners of the joints 71 and 72 can be chamfered.

[0038] The joint portion 71 has a Figure 2 The narrow width portion 71b is arranged on the left side (shown in FIG. Figure 2 The wide portion 71a is located on the right side of the lead frame. The wide portion 71a is located on the right side of the lead frame. Figure 2 The narrow width portion 71b has a first width dimension X in the vertical direction (shown in FIG. 1 ). The narrow width portion 71b has a width dimension Y narrower than the wide width portion 71a, and is formed to protrude to the left from the side edge portion 71c of the wide width portion 71a.

[0039] The wide portion 71a and the narrow portion 71b both have a substantially rectangular shape when viewed from above. For example, the width dimensions of the wide portion 71a and the narrow portion 71b in the left-right direction are set to be the same. In this case, the side edge portion 71c is arranged at a middle position between the left end portion and the right end portion of the joint 71. The narrow portion 71b is arranged at the center portion ( Figure 2 The joint 72 is formed by Figure 2 The wide portion 71 a of the bonding portion 71 and the bonding portion 72 have the same width (width dimension X) as the metal plate constituting the lead frame 7 .

[0040] The connecting portion 73 includes a connecting surface 73a extending in the left-right direction at a position above the joints 71 and 72, and a leg portion 73b extending from one side of the connecting surface 73a ( Figure 2 The end portion (one end portion) of the left side shown in FIG. 1 extends toward the joint portion 71 (the lower side); and the leg portion 73c, which extends from the other side of the connecting surface 73a ( Figure 2 The end (the other end) of the leg 73b (shown on the right side) extends toward the side of the joint 72 (the lower side). The leg 73b constitutes an example of the first leg, and the leg 73c constitutes an example of the second leg. In this embodiment, the leg 73c has a dimension longer than the leg 73b in the up-down direction. Therefore, the joint 71 extends in the left-right direction at a position above the joint 72.

[0041] The leg portion 73b is provided with a pair of connecting leg portions 73b1 and 73b2. These connecting leg portions 73b1 and 73b2 are arranged at the side end portions ( Figure 2 These connecting legs 73b1, 73b2 are on one side of the joint 71 ( Figure 2 The end portion of the narrow width portion 71b (more specifically, the left end portion of the narrow width portion 71b) and the other side ( Figure 2 Here, the outer edge portion 71d disposed between the end portion on one side of the joint portion 71 and the end portion on the other side of the joint portion 71 refers to the outer edge portion of the joint portion 71 other than the left and right ends (i.e., Figure 2 More specifically, the connecting legs 73b1 and 73b2 are connected to the area where the narrow width portion 71b is not formed near the side edge portion 71c of the wide width portion 71a where the narrow width portion 71b protrudes. More specifically, the connecting legs 73b1 and 73b2 are connected to the outer side of the wide width portion 71a ( Figure 2 The upper side and the lower side shown in the figure are partially connected. An opening 74 is formed between a pair of connecting legs 73b1 and 73b2. The leg portion 73c is composed of a flat surface having the same width as the flat surface portion 73a.

[0042] Next, refer to Figures 4 to 6 The following describes the state of each process step of the lead frame 7 having the above-mentioned structure. Figure 4 It is a development view of the lead frame 7 of the present embodiment before processing. Figure 5 and Figure 6 1 is a perspective view of the lead frame 7 of the present embodiment during the processing process. Figures 4 to 6 In Figure 1 The semiconductor module 1 is shown in the up-down direction and the left-right direction. Figure 4 and Figure 5 As shown in A, the metal plate 70 constituting the lead frame 7 before processing has a substantially rectangular shape having a longitudinal direction in the left-right direction in a plan view.

[0043] In the vicinity of the metal plate 70 Figure 4 The slit SA is formed at the right end portion shown in FIG. The slit SA is formed by penetrating the metal plate 70 perpendicularly to the plate surface of the metal plate 70. The slit SA has a first slit S1 extending in a direction parallel to the end surface of the metal plate 70 ( Figure 4 and a pair of second slits S2, the pair of second slits S2 from both ends of the first slit S1 to Figure 4 The slit SA has an overall orientation when viewed from above. Figure 4 The first slit S1 is formed in the metal plate 70. Figure 4 The second slits S2 are formed at the end surfaces ( Figure 4 The metal plate 70 and the slit SA may be provided with chamfers at their corners.

[0044] In addition, Figures 4 to 6 In the figure, for convenience of explanation, the first processing line BL1 to the fourth processing line BL4 are shown at the position where the metal plate 70 is bent. The first processing line BL1 is arranged outside the second slit S2 near the right end of the second slit S2 ( Figure 4 The second processing line BL2 is arranged slightly to the left of the first slit S1. The third processing line BL3 is arranged slightly to the left of the center of the metal plate 70. The fourth processing line BL4 is arranged near the metal plate 70. Figure 4 The first processing line BL1 to the fourth processing line BL4 are all provided to extend parallel to the end surface of the metal plate 70 in the left-right direction.

[0045] In addition, Figure 4 and Figure 5 In A, for the convenience of explanation, the reference numerals of the structural parts of the lead frame 7 after bending are shown. Figure 4 and Figure 5As shown in FIG. 1A, the portion to the right of the slit SA and the first processing line BL1 constitutes the joint portion 71, and the portion between the first processing line BL1 and the slit SA and the second processing line BL2 constitutes the leg portion 73b of the connecting portion 73. In addition, the portion between the second processing line BL2 and the third processing line BL3 constitutes the connecting face portion 73a of the connecting portion 73, the portion between the third processing line BL3 and the fourth processing line BL4 constitutes the leg portion 73c of the connecting portion 73, and the portion to the left of the fourth processing line BL4 constitutes the joint portion 72.

[0046] When processing the lead frame 7, first, the metal plate 70 is bent along the first processing line BL1 so that the left side portion of the metal plate 70 on the left side of the slit SA stands upright. Figure 5 As shown in B, the metal plate 70 is bent to a position perpendicular to the non-processed portion. By bending the metal plate 70 in this way, the joint portion 71, the leg portion 73b of the connection portion 73, and the opening portion 74 are formed.

[0047] At this time, the portion of the metal plate 70 disposed inside the slit SA constitutes the narrow width portion 71b of the joint 71. The portion of the metal plate 70 on the right side of the first processing line BL1 constitutes the wide width portion 71a of the joint 71. In addition, the portion of the wide width portion 71a disposed along the first processing line BL1 constitutes the side edge portion 71c, and the narrow width portion 71b is formed protruding from the side edge portion 71c. The leg portion 73b of the connecting portion 73 opposite to the joint 71 is formed by bending in an area (non-formation area) near the side edge portion 71c where the narrow width portion 71b is not formed.

[0048] Next, the metal plate 70 is bent along the second processing line BL2 so that the upper side portion above the second processing line BL2 is tilted to the right. Figure 6 As shown in A, a portion of the metal plate 70 on the upper side of the second processing line BL2 is bent to a position parallel to the joining portion 71. By bending the metal plate 70 in this manner, the connecting surface portion 73a of the connecting portion 73 is formed.

[0049] Next, the metal plate 70 is bent along the third processing line BL3 so that the right side portion of the metal plate 70 that is closer to the right side than the third processing line BL3 is bent downward. Figure 6 As shown in B, the portion of the metal plate 70 on the right side of the third processing line BL3 is bent to a position parallel to the extending direction of the pair of leg portions 73b. By bending the metal plate 70 in this way, the leg portions 73c of the connection portion 73 are formed.

[0050] Finally, the metal plate 70 is bent along the fourth processing line BL4 so that the lower side portion below the fourth processing line BL4 is raised upward. Figure 3As shown in FIG. 1 , the portion of the metal plate 70 below the fourth processing line BL4 is bent to a position parallel to the joint portion 71. By bending the metal plate 70 in this way, the joint portion 72 is formed. Figure 3 The lead frame 7 is shown.

[0051] The lead frame 7 thus formed is solder-bonded to the upper surface of the semiconductor chip 6 and the upper surface of the electrode pattern 2b. Figure 7 The positional relationship of the lead frame 7 with respect to the semiconductor chip 6 will be described. Figure 7 1 is an explanatory diagram of the positional relationship between the lead frame 7 and the semiconductor chip 6 of the present embodiment. Figure 7 A. Figure 7 B shows a perspective view and a top view of the lead frame 7, respectively. Figure 7 In FIG. 1 , for convenience of explanation, the outer edge of the semiconductor chip 6 is indicated by a dashed line.

[0052] like Figure 7 A. Figure 7 As shown in FIG. 2B , in this embodiment, the bonding portion 71 of the lead frame 7 is solder-bonded to the upper surface of the semiconductor chip 6 in such a manner that the bonding portion 71 is arranged in the central region of the semiconductor chip 6. More specifically, the lead frame 7 is bonded to the semiconductor chip 6 in such a manner that a pair of connecting legs 73b1 and 73b2 are arranged at a position including a middle position 63 between the left end portion 61 and the right end portion 62 of the semiconductor chip 6 (see FIG. 2B ). Figure 7 B).

[0053] like Figure 7 As shown in FIG. 1A , in the lead frame 7, the leg portion 73b (a pair of connecting leg portions 73b1, 73b2) of the connecting portion 73 is partially connected to the outer edge portion 71d disposed between the left end portion and the right end portion of the bonding portion 71. Therefore, the contact area between the leg portion 73b (a pair of connecting leg portions 73b1, 73b2) and the solder for bonding the bonding portion 71 to the semiconductor chip 6 can be reduced. Thus, even in the case where the leg portion 73b is formed by bending, the surface area of ​​the rounded corner portion formed by the bending process can be reduced, so that the occurrence of the solder climbing phenomenon can be suppressed, and the stress concentration on the semiconductor chip can be reduced.

[0054] More specifically, in the lead frame 7, the rounded corners that are the main cause of the solder climbing phenomenon are limited to the lower end portions of the legs 73b (a pair of connecting legs 73b1, 73b2) of the connecting portion 73 (more specifically, the left side surfaces of the lower end portions of the pair of connecting legs 73b1, 73b2). As a result, compared with the case where the rounded corners are provided in the entire width direction of the bonding portion 71, the surface area of ​​the rounded corners can be greatly reduced, so that the solder climbing phenomenon can be suppressed and the stress concentration on the semiconductor chip 6 can be reduced.

[0055] In particular, in the lead frame 7 of the present embodiment, the leg portion 73b (a pair of connecting leg portions 73b1, 73b2) of the connecting portion 73 is arranged at a position including the middle position 63 between the left end portion 61 and the right end portion 62 of the semiconductor chip 6. Generally, the semiconductor chip 6 is easily damaged due to stress concentration relative to the portion near the outer peripheral edge. In contrast, according to the lead frame 7 of the present embodiment, since the leg portion 73b (a pair of connecting leg portions 73b1, 73b2) is arranged at a position including the middle position 63 in the left-right direction of the semiconductor chip 6, even when stress is concentrated around the pair of connecting leg portions 73b1, 73b2, the stress concentration portion can be arranged near the center of the semiconductor chip 6, so that the semiconductor chip 6 can be made less likely to be damaged.

[0056] In the lead frame 7 of the present embodiment, the pair of connecting legs 73b1 and 73b2 extend from the left end of the connecting surface 73a and are connected to the opposite outer edge 71d of the joint 71. Thus, even if stress is concentrated around the pair of connecting legs 73b1 and 73b2, the stress concentration portion can be arranged at a separate position ( Figure 7 B), thus, the influence of stress concentration on the semiconductor chip 6 can be reduced.

[0057] In the lead frame 7 of the present embodiment, the leg portion 73b (a pair of connecting leg portions 73b1, 73b2) is formed by bending the peripheral portion of the slit SA formed in the metal plate 70 (see FIG. Figure 5 A and Figure 5 B) Therefore, the surface area of ​​the rounded corner portion formed by the bending process can be easily reduced without requiring a complicated structure.

[0058] In the lead frame 7 of the present embodiment, the leg portion 73b (a pair of connecting leg portions 73b1, 73b2) is arranged at a position including a middle position between the left end portion and the right end portion of the bonding portion 71 (the side edge portion 71c of the wide portion 71a) (see Figure 7B) Therefore, since the load when joining the lead frame 7 can be received via the leg portion 73 b near the center of the joining portion 71 , the joining portion 71 can be joined to the semiconductor chip 6 in a well-balanced manner.

[0059] In addition, the present invention is not limited to the above-mentioned embodiments, and various changes can be made to implement. In the above-mentioned embodiments, the size, shape, function, etc. of the constituent elements shown in the drawings are not limited thereto, and can be appropriately changed within the scope of the effect of the present invention. In addition, as long as it does not depart from the scope of the purpose of the present invention, it can be appropriately changed and implemented.

[0060] For example, in the above-described embodiment, the case where the slit SA is provided in the metal plate 70 constituting the lead frame 7 and the pair of leg portions 73b is provided is described. However, the structure of the lead frame 7 is not limited to this, and can be modified as appropriate. Figure 8 7A is a perspective view of a lead frame 7A according to a modified example of the present embodiment ( Figure 8 A) and the unfolded view before processing ( Figure 8 B) In addition, Figure 8 In the present invention, the same structures as those in the above-mentioned embodiment are denoted by the same reference numerals and the description thereof is omitted.

[0061] like Figure 8 As shown in FIG. 1B , in the lead frame 7A of the modified example, the slit SB is formed in the metal plate 70, which is different from the lead frame 7. The slit SB is formed by penetrating the metal plate 70 perpendicularly to the plate surface. The slit SB has a third slit S3 parallel to the end surface of the metal plate 70 (along the lead frame 7). Figure 8 B) extending in the up-down direction; and a fourth slit S4, which extends from Figure 8 The lower end of the third slit S3 shown in B extends to the right. Figure 8 The upper end portion indicated by B extends downward to a position slightly below the center of the metal plate 70 . The fourth slit S4 extends along the longitudinal direction of the metal plate 70 .

[0062] By subjecting the metal plate 70 thus constructed to a bending process similar to that of the above-described embodiment, a Figure 8 A is a lead frame 7A shown in FIG. The lead frame 7A is different from the lead frame 7 of the above embodiment in that the leg portion 73b of the connecting portion 73 connected to the joint portion 71 has a single connecting leg portion 73b3. In addition, the connecting leg portion 73b3 is configured to have a width greater than the width of the connecting leg portion 73b1 or the connecting leg portion 73b2. Similar to the pair of connecting leg portions 73b1 and 73b2, the connecting leg portion 73b3 is connected to a portion of the outer edge portion 71d disposed between the left end portion and the right end portion of the joint portion 71.

[0063] In the lead frame 7A having such a structure, the rounded corner portion that is the main cause of the solder climbing phenomenon is also limited to the lower end portion of the leg portion 73b (connecting leg portion 73b3) of the connecting portion 73. Therefore, compared with the case where the rounded corner portion is provided in the entire width direction of the bonding portion 71, the surface area of ​​the rounded corner portion can be greatly reduced, so the occurrence of the solder climbing phenomenon can be suppressed, and the stress concentration on the semiconductor chip 6 can be reduced.

[0064] In addition, in the above-mentioned embodiment, the case where the slit SA is vertically provided on the plate surface of the metal plate 70 constituting the lead frame 7 is described. However, the structure of the lead frame 7 is not limited to this, and can be changed appropriately. Fig. 9 7B is a perspective view of a lead frame 7B according to a modified example of the present embodiment ( Fig. 9 A) and the unfolded view before processing ( Fig. 9 B) In addition, Fig. 9 In the present invention, the same structures as those in the above-mentioned embodiment are denoted by the same reference numerals and the description thereof is omitted.

[0065] like Fig. 9 As shown in FIG. 1B , in the lead frame 7B of the modified example, the slit SC is formed in the metal plate 70, which is different from the lead frame 7. The slit SC is different from the slit SA in that it has a fifth slit S5 formed obliquely from both ends of the first slit S1 so as not to be perpendicular to the plate surface of the metal plate 70. The fifth slit S5 of the slit SC is formed in a direction toward Fig. 9 The upper end and the lower end of the metal plate 70 shown in B are formed by cutting.

[0066] By subjecting the metal plate 70 thus constructed to a bending process similar to that of the above-described embodiment, a Fig. 9 The lead frame 7B shown in FIG. 1A is different from the lead frame 7 of the above embodiment in that an inclined surface 71e is formed at the side edge of the narrow width portion 71b of the joint portion 71. The inclined surface 71e is formed outside the narrow width portion 71b so that the dimension in the width direction becomes larger toward the lower side. The inclined surface 71e constitutes an example of a limiting portion that limits the contact between the pair of connecting legs 73b1, 73b2 and the solder used to join the joint portion 71.

[0067] In the lead frame 7B having such a structure, an inclined surface portion 71e whose width direction dimension increases toward the lower side outside the narrow width portion 71b is formed in the joint portion 71. Thus, the contact between the solder and the left side surface of the pair of connecting legs 73b1, 73b2 is restricted, so that the solder can be suppressed from climbing up with respect to the left side surface of the pair of connecting legs 73b1, 73b2, thereby effectively reducing the stress concentration on the semiconductor chip 6.

[0068] Here, the lower side end of the inclined surface portion 71e is arranged at the same angle as the end surface ( Fig. 9 However, the position of the lower side end of the inclined surface 71e is not limited to this. The position of the lower side end of the inclined surface 71e can be arranged outside the position of the upper end of the narrow width portion 71b ( Fig. 9 It can be configured at any position based on the position of the vertical direction side (shown in B).

[0069] The characteristic points of the above-mentioned embodiment are summarized below.

[0070] The above embodiment provides a lead frame wiring structure that electrically connects a semiconductor element and a connection object, and the lead frame wiring structure is characterized in that the lead frame wiring structure has: a first bonding portion, which is solder-bonded to the semiconductor element; a second bonding portion, which is arranged separately from the first bonding portion and solder-bonded to the connection object; and a connecting portion, which connects the first bonding portion and the second bonding portion, and the connecting portion has: a connecting face portion, which is arranged separately from the first bonding portion and the second bonding portion in the up-down direction; a first leg portion, which extends from an end portion on one side of the connecting face portion toward the first bonding portion; and a second leg portion, which extends from an end portion on the other side of the connecting face portion toward the second bonding portion, and the first leg portion is connected to a part of an outer edge portion of the first bonding portion, which is arranged between the end portion on the one side and the end portion on the other side. According to this structure, the first leg portion is connected to a part of an outer edge portion of the first bonding portion, which is arranged between the end portion on the one side and the end portion on the other side. Therefore, the contact area between the first leg and the solder for joining the first joint to the semiconductor element can be reduced. Thus, even when the first leg is formed by bending, the surface area of ​​the fillet portion formed by the bending process can be reduced, thereby suppressing the occurrence of solder climbing and reducing stress concentration relative to the semiconductor chip.

[0071] In the lead frame wiring structure of the above embodiment, the first leg portion is arranged at a position including a middle position between the end of the first bonding portion on one side and the end of the first bonding portion on the other side. According to this structure, the first leg portion is arranged at a position including a middle position between the end of the first bonding portion on one side and the end of the other side, so that the load when the lead frame wiring is bonded can be borne by the first leg portion near the center of the first bonding portion, so that the first bonding portion can be bonded to the semiconductor element in a well-balanced manner.

[0072] In the lead frame wiring structure of the above embodiment, the first leg portion is formed by bending the peripheral portion of the slit formed in the metal plate constituting the lead frame wiring. According to this structure, the first leg portion is formed by bending the peripheral portion of the slit formed in the metal plate, so that the surface area of ​​the rounded corner portion formed by the bending process can be simply reduced without a complicated structure.

[0073] In the lead frame wiring structure of the above embodiment, when the first bonding portion is bonded to the semiconductor element, the first leg portion is arranged at a position including a middle position between the end portion on one side and the end portion on the other side of the semiconductor element. According to this structure, since the first leg portion is arranged at a position including a middle position between the end portion on one side and the end portion on the other side of the semiconductor element, even when stress is concentrated on the periphery of the first leg portion, the stress concentration portion can be arranged near the center of the semiconductor element, rather than near the outer peripheral edge of the semiconductor element, so that the semiconductor element can be made less likely to be damaged.

[0074] In the lead frame wiring structure of the above embodiment, the pair of first legs extend from the end of the one side of the connecting surface portion toward the first joint portion and are connected to the opposite outer edge portions in the first joint portion. According to this structure, since the pair of first legs are connected to the opposite outer edge portions in the first joint portion, even if stress concentration occurs around the first leg portion, the stress concentration portion can be arranged at a separate position, thereby reducing the influence of stress concentration on the semiconductor element.

[0075] In the lead frame wiring structure of the above embodiment, the first joint portion has a limiting portion that limits the contact between the solder and the surface of the one side of the first leg portion. According to this structure, since the contact between the solder and the surface of the one side of the first leg portion is limited, the solder can be suppressed from climbing relative to the surface of the one side of the first leg portion, thereby effectively reducing the stress concentration on the semiconductor chip.

[0076] The semiconductor module of the above embodiment is characterized in that the semiconductor module has any one of the lead frame wiring structures described above. According to this structure, the effect of the lead frame wiring structure described above can be obtained in the semiconductor module.

[0077] Industrial Applicability

[0078] The semiconductor module of the present invention has the effect of reducing stress concentration on a semiconductor chip, and is suitable for semiconductor modules such as automotive motor drive control inverters that require small size, light weight, and long-term reliability in a high-temperature operating environment.

[0079] This application is based on Japanese Patent Application No. 2018-208087 filed on November 5, 2018, the entire contents of which are hereby incorporated by reference.

Claims

1. A lead frame wiring structure that electrically connects a semiconductor element disposed on one side of the lead frame wiring and a connection object disposed on the other side of the lead frame wiring, the lead frame wiring structure being characterized in that: The lead frame wiring structure has: A first joint portion, the solder of which is joined to the semiconductor element; a second joining portion which is disposed separately from the first joining portion and is joined to the connection object by solder; and a connecting portion connecting the first connecting portion and the second connecting portion, The connecting portion has: a connecting surface portion disposed apart from the first connecting portion and the second connecting portion in the up-down direction; a first leg portion extending from the end portion on the one side of the connecting surface portion toward the first joining portion; and a second leg portion extending from the other end of the connecting surface portion toward the second joining portion, The first joining portion includes a wide portion and a narrow portion protruding from a side edge of the wide portion. The first leg portion is connected to a part of the outer edge of the first joining portion, which is arranged between the end portion on one side and the end portion on the other side, and is a non-formed area of ​​the narrow width portion in the wide width portion. In a state where the first bonding portion is bonded to the semiconductor element, the first leg portion is arranged at a center between the one end portion and the other end portion of the semiconductor element.

2. The lead frame wiring structure according to claim 1, characterized in that: The first leg portion is disposed at a center between the one end portion and the other end portion of the first joining portion.

3. The lead frame wiring structure according to claim 1 or 2, characterized in that: The first leg portion is formed by bending a portion around a slit formed in a metal plate constituting the lead frame wiring.

4. The lead frame wiring structure according to claim 1 or 2, characterized in that: The pair of first leg portions extend from the one end portion of the connecting surface portion toward the first joining portion and are connected to opposing outer edge portions of the first joining portion.

5. A lead frame wiring structure that electrically connects a semiconductor element disposed on one side of the lead frame wiring and a connection object disposed on the other side of the lead frame wiring, the lead frame wiring structure being characterized in that: The lead frame wiring structure has: A first joint portion, the solder of which is joined to the semiconductor element; a second joining portion which is disposed separately from the first joining portion and is joined to the connection object by solder; and a connecting portion connecting the first connecting portion and the second connecting portion, The connecting portion has: a connecting surface portion disposed apart from the first connecting portion and the second connecting portion in the up-down direction; a first leg portion extending from the end portion on the one side of the connecting surface portion toward the first joining portion; and a second leg portion extending from the other end of the connecting surface portion toward the second joining portion, The first joining portion includes a wide portion and a narrow portion protruding from a side edge of the wide portion. The first leg portion is connected to a part of the outer edge of the first joining portion, which is arranged between the end portion on one side and the end portion on the other side, and is a non-formed area of ​​the narrow width portion in the wide width portion. The first joining portion includes a restriction portion which is formed outside the narrow width portion so that the dimension in the width direction increases toward the downward side and restricts contact between the first leg portion and the brazing material.

6. A semiconductor module, characterized in that: This semiconductor module has the lead frame wiring structure according to any one of claims 1 to 5.

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