Semiconductor device and method for manufacturing semiconductor device

Abstract

A semiconductor device according to the present application includes a substrate, a semiconductor chip provided on the substrate, a nut, a lead frame provided on the semiconductor chip and the nut, screw-fastened to the nut, a nut box that houses the nut, an opening formed in a bottom of the nut box to expose the nut downward, and a solder provided at least between the semiconductor chip and the substrate or the lead frame.

Description

TECHNICAL FIELD

[0001] The present application relates to a semiconductor device and a manufacturing method of a semiconductor device. BACKGROUND

[0002] A manufacturing method of a power semiconductor device is disclosed in Patent Literature 1. In the manufacturing method, an insulating layer and a metal circuit layer are bonded on a metal substrate, a heat sink is disposed on an upper surface of the metal circuit layer with a solder sheet interposed therebetween, and a silicon semiconductor chip is disposed on an upper surface of the heat sink with a solder sheet interposed therebetween. In addition, a side terminal portion of a lead frame is disposed on an upper surface of the silicon semiconductor chip with a solder sheet interposed therebetween. All of them are heated to melt all of the solder sheets. Thus, the metal circuit layer and the heat sink, the heat sink and the silicon semiconductor chip, and the silicon semiconductor chip and the side terminal portion of the lead frame are joined at one time.

[0003] Patent Literature 1: Japanese Patent Application Laid-Open No. 2007-157863 SUMMARY

[0004] In the solder joining process like that of Patent Literature 1, it is considered that the solder is heated from the substrate side to be melted. In this case, the melting of the solder can take time.

[0005] An object of the present application is to obtain a semiconductor device and a manufacturing method of a semiconductor device capable of melting a solder in a short time.

[0006] A semiconductor device according to a first aspect includes a substrate, a semiconductor chip provided on the substrate, a nut, a lead frame provided on the semiconductor chip and the nut, screw-fastened with the nut, a nut box housing the nut, an opening formed in a bottom portion of the nut box to expose the nut downward, and a solder provided at least between the semiconductor chip and the substrate or the lead frame.

[0007] A manufacturing method of a semiconductor device according to a second aspect includes mounting a semiconductor device having a substrate, a semiconductor chip provided on the substrate, a nut, a lead frame provided on the semiconductor chip and the nut, a nut box housing the nut, an opening formed in a bottom portion of the nut box to expose the nut downward, and a solder provided at least between the semiconductor chip and the substrate or the lead frame, on a lower jig having a protrusion on an upper surface, bringing the protrusion into contact with the nut via the opening, and heating the lower jig in a state where the protrusion is in contact with the nut to join the semiconductor chip and the substrate or the lead frame by the solder.

[0008] In the method for manufacturing a semiconductor device according to the third aspect, the semiconductor device having a substrate, a semiconductor chip, a lead frame, a solder, and a case is mounted on a lower jig having a protrusion formed of a metal on an upper surface, the protrusion is brought into contact with the lead frame, wherein the semiconductor chip is provided on the substrate, the lead frame is provided on the semiconductor chip, the solder is provided at least between the semiconductor chip and the substrate or the lead frame, and the case surrounds the semiconductor chip. The lower jig is heated in a state where the protrusion is brought into contact with the lead frame, and the semiconductor chip and the substrate or the lead frame are joined by the solder.

[0009] Effects of the Invention

[0010] In the semiconductor device and the method for manufacturing a semiconductor device according to the present invention, heat can be transferred to the solder via the lead frame. Thus, the solder can be melted in a short time. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a sectional view of a semiconductor device according to Embodiment 1.

[0012] Figure 2 is a flowchart showing a method for manufacturing a semiconductor device according to Embodiment 1.

[0013] Figure 3 is a sectional view of a semiconductor device according to Comparative Example.

[0014] Figure 4 is a sectional view of a semiconductor device according to Embodiment 2.

[0015] Figure 5 is a sectional view of a semiconductor device according to Embodiment 3.

[0016] Figure 6 is a sectional view of a semiconductor device according to Embodiment 4.

[0017] Figure 7 is a sectional view of a semiconductor device according to Embodiment 5. DETAILED DESCRIPTION

[0018] The semiconductor device and the method for manufacturing a semiconductor device according to each of the embodiments will be described with reference to the drawings. The same reference numerals are assigned to the same or corresponding structural elements, and repeated description will be omitted in some cases.

[0019] Embodiment 1

[0020] Figure 1is a sectional view of the semiconductor device 100 according to Embodiment 1. The semiconductor device 100 has a DLB (Direct Lead Bonding) configuration in which the lead frame 8 is directly soldered to the semiconductor chip 10. The semiconductor device 100 has a base plate 2 and an insulating circuit substrate 4 that is bonded to the central portion of the upper surface of the base plate 2 by solder 3. The housing 5 is fixed to the outer peripheral portion of the upper surface of the base plate 2 by an adhesive or the like. The base plate 2 is formed of, for example, Cu, Al, or AlSiC.

[0021] The insulating circuit substrate 4 has an insulating substrate 6 and a circuit pattern 7 that is provided on the upper surface and the back surface of the insulating substrate 6. The circuit pattern 7 provided on the back surface of the insulating substrate 6 is fixed to the base plate 2 via the solder 3. The circuit pattern 7 provided on the upper surface of the insulating substrate 6 constitutes an electric circuit. Therefore, the circuit pattern 7 provided on the upper surface of the insulating substrate 6 has a lower coverage of the insulating substrate 6 than the circuit pattern 7 provided on the back surface. The insulating substrate 6 is formed of, for example, AI2O3, AIN, or Si3N4. The circuit pattern 7 is formed of, for example, Al or Cu.

[0022] A plurality of semiconductor chips 10 is provided on the insulating circuit substrate 4. The back surfaces of the plurality of semiconductor chips 10 are fixed to the circuit pattern 7 provided on the upper surface of the insulating substrate 6 via solder 9. The solder 9 is formed of, for example, paste solder or sheet solder. The semiconductor chip 10 is formed of, for example, Si. The semiconductor chip 10 can also be formed of a wide band gap semiconductor. The wide band gap semiconductor is, for example, silicon carbide, gallium nitride-based material, or diamond.

[0023] The lead frame 8 is provided on the plurality of semiconductor chips 10 and a nut 12 described later. The lead frame 8 is bonded to the upper surfaces of the plurality of semiconductor chips 10 via solder 11. The solder 11 is formed of, for example, paste solder or sheet solder. The lead frame 8 is formed of, for example, Cu or Al. The lead frame 8 is fixed to the housing 5. The housing 5 encloses the insulating circuit substrate 4 and the plurality of semiconductor chips 10. The housing 5 is formed of, for example, PPS (Poly Phenylene Sulfide).

[0024] A screw hole 12a is formed in the nut 12. The screw hole 12a overlaps a through-hole 8a formed in the lead frame 8 when viewed from above. The nut 12 and the lead frame 8 are screw-fastened by a screw 20 via the through-hole 8a and the screw hole 12a. The nut 12 is formed of, for example, aluminum, stainless steel, or titanium.

[0025] A nut box 13 accommodates the nut 12. The nut box 13 is open on the side on which the lead frame 8 is provided. The nut 12 is in contact with the lead frame 8 in a state of being accommodated in the nut box 13. In addition, the nut box 13 is formed with an opening 13a in the bottom portion that exposes the nut 12 downward.

[0026] The nut box 13 is provided outside a region in which the semiconductor chip 10 is housed in the housing 5. The nut box 13 is fixed to the housing 5. The nut box 13 can also be a part of the housing 5. The nut box 13 is formed of PPS, for example.

[0027] The lower jig 50 is used in a manufacturing process of the semiconductor device 100. The lower jig 50 has a protrusion 51 on an upper surface. The lower jig 50 is arranged in contact with the base plate 2. The protrusion 51 is arranged in contact with the nut 12 via the opening 13a. The lower jig 50, the protrusion 51 are formed of metal such as stainless steel, for example.

[0028] Figure 2 is a flowchart showing a manufacturing method of the semiconductor device 100 according to Embodiment 1. First, in step SI, as shown in Figure 1 the base plate 2, the insulating circuit substrate 4, the semiconductor chip 10, the solder 3, 9, 11, the lead frame 8, the housing 5, the nut 12, and the nut box 13 are arranged toward a mounting position. That is, the insulating circuit substrate 4 is arranged above the base plate 2 with the solder 3 interposed therebetween, and the semiconductor chip 10 is arranged above the insulating circuit substrate 4 with the solder 9 interposed therebetween. In addition, the nut 12 is housed in the nut box 13. In addition, the lead frame 8 is arranged above the semiconductor chip 10 with the solder 11 interposed therebetween. In addition, the housing 5 is arranged above the base plate 2. The end portion of the lead frame 8 is arranged above the nut 12.

[0029] Next, in step S2, the semiconductor device 100 is arranged on the lower jig 50. At this time, the protrusion 51 is in contact with the nut 12 via the opening 13a of the nut box 13. Next, in step S3, the lower jig 50 is heated in a state in which the protrusion 51 is in contact with the nut 12. Thereby, the solder 3, 9, 11 is heated via the base plate 2. Further, the solder 3, 9, 11 is heated via the nut 12 and the lead frame 8. As a result, the solder 3, 9, 11 is melted. Thus, the base plate 2 and the insulating circuit substrate 4, the semiconductor chip 10 and the insulating circuit substrate 4, and the semiconductor chip 10 and the lead frame 8 are joined by the solder 3, 9, 11.

[0030] Figure 3 is a sectional view of a semiconductor device 800 according to a comparative example. The semiconductor device 800 according to the comparative example differs from the semiconductor device 100 in that an opening is not formed in a bottom portion of a nut box 813. In the case of the semiconductor device 800 according to the comparative example, if the lower jig 850 is heated, the solder 3, 9, 11 is heated to be melted via the base plate 2. At this time, the melting of the solder 3, 9, 11 can take time.

[0031] In contrast, in the present embodiment, by bringing the protrusion 51 of the lower jig 50 into contact with the nut 12, it is possible to transmit heat to the solders 3, 9, 11 via the lead frame 8. Thus, it is possible to melt the solders 3, 9, 11 in a short time. Thereby, it is possible to improve the tact time of the solder joining process.

[0032] In addition, by efficiently transmitting heat from the base plate 2 and the lead frame 8 to the solders 3, 9, 11, it is possible to reliably melt the solders 3, 9, 11. Thus, it is possible to improve the reliability of the semiconductor device 100.

[0033] As a modification of the present embodiment, the protrusion 51 can have a higher thermal conductivity than the portions of the lower jig 50 other than the protrusion 51. The protrusion 51 is formed of Cu, for example. Thereby, it is possible to efficiently transmit heat to the lead frame 8, and heat is easily transmitted to the solders 3, 9, 11.

[0034] In addition, in step S3, as shown by an arrow 80 in FIG. 8, the lower jig 50 can be heated while the lead frame 8 is pressed against the protrusion 51. The pressing is performed using a plunger, for example. Thereby, it is possible to reduce the contact thermal resistance between the lower jig 50 and the lead frame 8. Thus, heat is easily transmitted to the solders 3, 9, 11. Figure 1

[0035] The structure of the semiconductor device 100 is not limited to the structure shown in FIG. 1. Although three semiconductor chips 10 are shown in FIG. 1, the number of semiconductor chips 10 provided in the semiconductor device 100 can be greater than or equal to one. In addition, the housing 5 can be fixed to the insulating circuit board 4. In addition, the solders can be provided at least between the semiconductor chips 10 and the insulating circuit board 4 or the lead frame 8. Figure 1 Figure 1

[0036] These modifications can be appropriately applied to the semiconductor device and the method of manufacturing a semiconductor device according to the following embodiments. Furthermore, regarding the semiconductor device and the method of manufacturing a semiconductor device according to the following embodiments, since there are many commonalities with Embodiment 1, the differences from Embodiment 1 will be mainly described.

[0037] Embodiment 2

[0038] Figure 4 ​​​is a sectional view of the semiconductor device 200 to which Embodiment 2 is applied. The structure of the lead frame 208 of the semiconductor device 200 is different from that of the semiconductor device 100. The other structures are the same as those of Embodiment 1. The lead frame 208 has a main body portion 208a and an external connection terminal portion 208b. The main body portion 208a is provided directly above the semiconductor chip 10. The external connection terminal portion 208b is joined to the main body portion 208a by solder 216 and is provided directly above the nut 12. The main body portion 208a and the external connection terminal portion 208b are formed of, for example, Cu or Al. The external connection terminal portion 208b is fixed by the case 5.

[0039] In the present embodiment, heat can be transferred from the lower jig 50 to the solder 216 via the nut 12 and the external connection terminal portion 208b. Thus, even in the case where the lead frame 208 has a solder joint portion, the solder 216 can be melted in a short time.

[0040] Embodiment 3

[0041] Figure 5 is a sectional view of the semiconductor device 300 to which Embodiment 3 is applied. In the manufacturing process of the semiconductor device 300, the protrusion 351 of the lower jig 350 is inserted into the screw hole 12a of the nut 12. The protrusion 351 is cut so as to be screwed with the nut 12. In addition, the lead frame 8 and the nut 12 are screwed by the screw 20. The lower jig 350 is heated in a state where the protrusion 351 and the nut 12 and the lead frame 8 and the nut 12 are screwed, respectively.

[0042] Thus, the contact thermal resistance between the protrusion 351 and the nut 12 and between the nut 12 and the lead frame 8 can be reduced. Thus, heat is easily transferred to the solders 3, 9, and 11. Further, the lower jig 350 can be heated in a state where only one of the protrusion 351 and the nut 12 and the nut 12 and the lead frame 8 is screwed.

[0043] Embodiment 4

[0044] Figure 6 is a sectional view of the semiconductor device 400 to which Embodiment 4 is applied. The semiconductor device 400 is different from the semiconductor device 100 in that a fin 417 is provided under the insulating circuit board 4. The other structures are the same as those of Embodiment 1. The fin 417 is provided to the back surface of the base plate 2. The fin 417 is, for example, a needle-shaped fin. Thus, the cooling performance of the semiconductor device 400 can be improved. The fin 417 can be a part of the base plate 2 or a member different from the base plate 2.

[0045] Embodiment 5

[0046] Figure 7is a sectional view of the semiconductor device 500 according to Embodiment 5. The semiconductor device 500 differs from the semiconductor device 100 in that the nut 12 and the nut box 13 are not provided. The other structures are the same as those of Embodiment 1.

[0047] Next, a manufacturing method of the semiconductor device 500 will be described. First, the insulating circuit substrate 4 is arranged on the base plate 2 with the solder 3 interposed therebetween, and the semiconductor chip 10 is arranged on the insulating circuit substrate 4 with the solder 9 interposed therebetween. In addition, the lead frame 8 is arranged on the semiconductor chip 10 with the solder 11 interposed therebetween. Further, the housing 5 is arranged on the base plate 2.

[0048] Next, the semiconductor device 500 is mounted on the lower jig 50 so that the protrusions 51 come into contact with the lead frame 8. Next, the lower jig 50 is heated while the protrusions 51 are in contact with the lead frame 8. The protrusions 51 of the lower jig 50 are formed of metal. Thus, the solders 3, 9, and 11 are heated via the base plate 2. Further, the solders 3, 9, and 11 are heated via the lead frame 8. As a result, the solders 3, 9, and 11 are melted. Thus, the base plate 2 and the insulating circuit substrate 4, the semiconductor chip 10 and the insulating circuit substrate 4, and the semiconductor chip 10 and the lead frame 8 are joined by the solders 3, 9, and 11.

[0049] In the present embodiment, by bringing the protrusions 51 of the lower jig 50 into contact with the lead frame 8, heat can be transferred to the solders 3, 9, and 11 via the lead frame 8. Thus, the solders 3, 9, and 11 can be melted in a short time. Therefore, the tact time of the solder joining process can be improved.

[0050] The technical features described in each of the embodiments can be used in appropriate combination.

[0051] Explanation of Reference Numerals

[0052] 2 base plate, 4 insulating circuit substrate, 5 housing, 6 insulating substrate, 7 circuit pattern, 8 lead frame, 8a through-hole, 10 semiconductor chip, 12 nut, 12a screw hole, 13 nut box, 13a opening, 20 screw, 50 lower jig, 51 protrusion, 100, 200 semiconductor device, 208 lead frame, 208a main body portion, 208b external connection terminal portion, 300 semiconductor device, 350 lower jig, 351 protrusion, 400 semiconductor device, 417 fin, 500, 800 semiconductor device, 813 nut box, 850 lower jig.

Claims

1. A semiconductor device, characterized in that, have: substrate; A semiconductor chip disposed on the substrate; Nut; A lead frame is disposed on the semiconductor chip and the nut, and is fastened to the nut with screws; A nut box that houses the nut, with an opening formed at the bottom of the nut box that exposes the nut downwards; as well as Solder, which is disposed at least between the semiconductor chip and the substrate or the lead frame. The lead frame has a main body portion disposed directly above the semiconductor chip and an external connection terminal portion that is joined to the main body portion by solder and disposed directly above the nut. The opening is configured such that the protrusion of the lower clamp, which has a protrusion on its upper surface, contacts the nut via the opening.

2. The semiconductor device according to claim 1, characterized in that, The lead frame is in contact with the nut.

3. The semiconductor device according to claim 1 or 2, characterized in that, The semiconductor device has a housing surrounding the semiconductor chip. The nut box is disposed on the housing.

4. The semiconductor device according to claim 1 or 2, characterized in that, The semiconductor device has fins disposed beneath the substrate.

5. The semiconductor device according to claim 1 or 2, characterized in that, The semiconductor chip is formed from a wide-bandgap semiconductor.

6. The semiconductor device according to claim 5, characterized in that, The wide-bandgap semiconductor is silicon carbide, gallium nitride, or diamond.

7. A method for manufacturing a semiconductor device, characterized in that, A semiconductor device comprising a substrate, a semiconductor chip, a nut, a lead frame, a nut box, and solder is mounted on a lower clamp having a protrusion on its upper surface, such that the protrusion contacts the nut through an opening. The semiconductor chip is disposed on the substrate, the lead frame is disposed on the semiconductor chip and the nut, and the nut box houses the nut. An opening is formed at the bottom of the nut box, allowing the nut to protrude downwards. Solder is disposed at least between the semiconductor chip and either the substrate or the lead frame. The lower clamp is heated while the nut is in contact with the lead frame and the protrusion is in contact with the nut, so that the semiconductor chip is bonded to the substrate or the lead frame by the solder.

8. A method for manufacturing a semiconductor device, characterized in that, A semiconductor device comprising a substrate, a semiconductor chip, a lead frame, solder, and a housing is mounted on a lower clamp having a metal protrusion on its upper surface, such that the protrusion contacts the lead frame. The semiconductor chip is disposed on the substrate, the lead frame is disposed on the semiconductor chip, the solder is disposed at least between the semiconductor chip and the substrate or the lead frame, and the housing surrounds the semiconductor chip. The lower clamp is heated while the protrusion is in contact with the lead frame, and the semiconductor chip is bonded to the substrate or the lead frame by the solder.

9. The method for manufacturing a semiconductor device according to claim 7 or 8, characterized in that, The protrusion has a higher thermal conductivity than the portion of the lower clamp excluding the protrusion.

10. The method of manufacturing a semiconductor device according to claim 7 or 8, characterized in that, The lower clamp is heated while the lead frame is pressed against the protrusion.

11. The method for manufacturing a semiconductor device according to claim 7, characterized in that, The protrusion is threaded and fastened to the nut with a screw.

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