Semiconductor devices and manufacturing methods thereof

Abstract

A semiconductor device capable of preventing crack defects and a method for manufacturing the same are obtained. The third side surface (17c) of the molding part (17) has inclined surfaces (18, 19) that are inclined in a direction that causes the central portion in the vertical direction to bulge out. The molding resin (14) also has a residual portion (20) provided at the central portion of the third side surface (17c) and a tenon (21) provided between the inclined surface (18) and the residual portion (20). The tenon (21) protrudes laterally relative to the inclined surface (18). The residual portion (20) protrudes laterally relative to the tenon (21) and has a fracture surface that is perpendicular in the vertical direction.

Description

Technical Field

[0001] This invention relates to semiconductor devices and methods for manufacturing the same. Background Technology

[0002] Semiconductor devices designed to handle high voltage and high current power control, with the power path positioned vertically, are typically called power semiconductor devices. Examples of power semiconductor devices include IGBTs (Insulated Gate Bipolar Transistors), MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), bipolar transistors, and diodes.

[0003] Semiconductor devices, which mount power semiconductor components onto a circuit board and encapsulate them with encapsulating resin, are widely used in industrial equipment, automobiles, railways, and other fields. In recent years, with the increasing demand for high-performance devices equipped with semiconductor devices, requirements for performance enhancement, such as increased rated voltage and current, and miniaturization, are rising.

[0004] As a package structure for semiconductor devices, there is a molded package type. In a molded package type, a semiconductor element is mounted on a lead frame, and the semiconductor element is bonded to the lead frame terminals by wire bonding and encapsulated with epoxy resin. As a method of manufacturing semiconductor devices, transfer molding is generally used, in which the lead frame is clamped by an upper mold and a lower mold, and epoxy resin is injected into the cavity. After molding, the leads extending from the side of the package are cut by a punch (for example, see Patent Document 1), and the cut leads are bent to form electrodes.

[0005] As a highly productive molding method, a multi-row molding resin injection process is generally known, in which molding resin is sequentially injected into multiple cavities connected to each other by runners. Since the resin in the runners is unusable, it is punched out and removed by resin cutting. After resin cutting, a residue with a vertical fracture surface remains on the side of the molding resin.

[0006] Patent Document 1: Japanese Utility Model Application Publication No. 5-5220

[0007] At the flow channel where semiconductor devices are connected to both ends, shear stress is applied to both ends of the resin in the flow channel portion during resin cutting. Therefore, only half of the resin cutting and stamping capacity can be applied at one end. Consequently, a problem arises where cracks occur in the molding section starting from the root of the resin residue after cutting. Summary of the Invention

[0008] The present invention was proposed to solve the above-mentioned problems, and its purpose is to obtain a semiconductor device and a method for manufacturing the same that can prevent crack defects.

[0009] The semiconductor device of the present invention is characterized by having: a semiconductor chip; lead terminals connected to the semiconductor chip; and an insulating molding resin that encapsulates a portion of the semiconductor chip and the lead terminals, the molding resin having a molding portion comprising first and second sides opposite to each other, and a third side different from the first and second sides, the lead terminals protruding from the first and second sides, the third side having an inclined surface inclined in a direction such that a central portion of the third side protrudes in the vertical direction, the molding resin further having a residual portion disposed at the central portion of the third side and a tenon disposed between the inclined surface and the residual portion, the tenon protruding laterally relative to the inclined surface, the residual portion protruding laterally relative to the tenon, and having a fracture surface perpendicular in the vertical direction.

[0010] The effects of the invention

[0011] In this invention, a tenon is provided on the third side of the molding resin, between the inclined surface and the residual portion. Therefore, even when the punch contacts the tenon during resin cutting, only the tenon is destroyed as a dummy component, and no cracks are generated in the molded portion of the molding resin. Furthermore, by using the tenon as a marker for resin cutting, the positional accuracy of the punch is improved.

[0012] As a result, crack defects can be prevented. Attached Figure Description

[0013] Figure 1 This is a cross-sectional view of the semiconductor device involved in Embodiment 1.

[0014] Figure 2 This is a side view of the semiconductor device involved in Embodiment 1.

[0015] Figure 3 This is a side view of the semiconductor device involved in Embodiment 1.

[0016] Figure 4 This is a flowchart of the manufacturing method of the semiconductor device according to Embodiment 1.

[0017] Figure 5 This is a cross-sectional view showing the manufacturing method of the semiconductor device according to Embodiment 1.

[0018] Figure 6 This is a top view showing the manufacturing method of the semiconductor device according to Embodiment 1.

[0019] Figure 7 This is a cross-sectional view showing the manufacturing method of the semiconductor device according to Embodiment 1.

[0020] Figure 8 This is a cross-sectional view showing the manufacturing method of the semiconductor device according to Embodiment 1.

[0021] Figure 9 It is a side view showing the manufacturing method of the semiconductor device involved in the comparison.

[0022] Figure 10 This is a side view of the semiconductor device involved in Embodiment 2.

[0023] Figure 11 This is a side view showing the resin cutting of the semiconductor device according to Embodiment 2.

[0024] Figure 12 This is a side view showing the manufacturing method of the semiconductor device according to Embodiment 3.

[0025] Figure 13 This is a side view showing the manufacturing method of the semiconductor device according to Embodiment 3.

[0026] Figure 14 This is a side view showing the manufacturing method of the semiconductor device according to Embodiment 3.

[0027] Figure 15 This is a side view showing the manufacturing method of the semiconductor device according to Embodiment 3.

[0028] Figure 16 This is a side view showing the manufacturing method of the semiconductor device according to Embodiment 3.

[0029] Figure 17 This is a side view showing the manufacturing method of the semiconductor device according to Embodiment 4.

[0030] Figure 18 This is a side view showing the manufacturing method of the semiconductor device according to Embodiment 4.

[0031] Figure 19 This is a side view showing the manufacturing method of the semiconductor device according to Embodiment 4. Detailed Implementation

[0032] Referring to the accompanying drawings, the semiconductor device and its manufacturing method according to the embodiments are described. The same or corresponding structural elements are labeled with the same reference numerals, and sometimes repeated descriptions are omitted.

[0033] Implementation Method 1

[0034] Figure 1This is a cross-sectional view of the semiconductor device according to Embodiment 1. Die pads 1 and 2, power terminals 3 and IC terminals 4 are formed of copper or copper alloy lead frames and are separated from each other. The height of die pad 2 is the same as the height of the frame surrounding the device. Through a bending process, die pad 1 is positioned lower than die pad 2. The thickness of the lead frame is set to match the current flowing through the terminals during actual use, but is set to 0.1 mm to 1 mm for stable manufacturing via stamping.

[0035] The lower surface electrodes of semiconductor chips 5 and 6 are bonded to die pad 1 via solder 7. Semiconductor chip 5 is an IGBT, but it can also be a MOSFET. Semiconductor chip 6 is a diode, but it can also be a Schottky barrier diode.

[0036] The upper surface electrodes of semiconductor chips 5 and 6 are connected to each other via power wire 8. The upper surface electrode of semiconductor chip 6 is connected to power terminal 3 via power wire 9. Power wires 8 and 9 are bonded to power terminal 3 and the upper surface electrodes of semiconductor chips 5 and 6 using an ultrasonic bonding device. As the material for power wires 8 and 9, which carry large currents, Al, which has a lower conductivity than Ag but is less expensive, is chosen. The diameter of power wires 8 and 9 is 0.1 to 0.5 mm.

[0037] An IC (Integrated Circuit) component 10 is bonded to the die pad 2 using Ag paste 11, and the Ag paste 11 is cured in an oven. The gate electrode on the upper surface of the semiconductor chip 5 is connected to the IC component 10 via IC wires 12. The IC component 10 is connected to the IC terminal 4 via IC wires 13. The IC component 10 controls the semiconductor chip 5 based on signals input from the IC terminal 4. Highly conductive materials such as gold, silver, and copper are selected for the IC wires 12 and 13. The IC wires 12 and 13 are processed to a diameter of less than or equal to 0.05 mm, formed into spheres through spark bonding, and then bonded to the small pads of the IC component 10.

[0038] Semiconductor chips 5 and 6, die pads 1 and 2, power terminals 3, and a portion of IC terminals 4 are encapsulated by insulating molding resin 14. Molding resin 14 is a thermosetting epoxy resin filled with silicon dioxide (SiO2) as a filler, resulting in a coefficient of linear expansion close to that of copper.

[0039] On the lower surface of the die pad 1, an insulating film 15 and a metal foil 16 are provided as insulating and heat-dissipating materials. The metal foil 16 protrudes from the lower surface of the molding resin 14. However, the insulating and heat-dissipating material can also be the molding resin 14. Alternatively, it can be a 0.1 mm to 0.3 mm thick sheet material filled with epoxy resin containing aluminum nitride (AlN), boron nitride (BN), or silicon dioxide (SiO2) as high heat-dissipating fillers. Alternatively, it can be a DBC (Direct Bonded Copper) substrate, an AMB (Active Metal Brazing) substrate, or a DBA (Direct Bonded Aluminum) substrate, which combines high heat-dissipating insulating materials such as aluminum nitride, silicon nitride (Si3N4), and silicon dioxide. This allows for further improvement in heat dissipation while maintaining insulation.

[0040] Figure 2 and Figure 3 This is a side view showing the semiconductor device according to Embodiment 1. The molding resin 14 has a molding section 17 in which semiconductor chips 5, 6, etc. are built in. The molding section 17 includes a first side surface 17a and a second side surface 17b opposite to each other, and a third side surface 17c different from the first and second side surfaces. Figure 2 This is a side view of the third side 17c viewed from a vertical direction. In order to connect the semiconductor device to an external power source, power terminal 3 and IC terminal 4 protrude from the first side 17a and the second side 17b, respectively.

[0041] Figure 3 This is a side view of the first side surface 17a as viewed from a vertical direction. Furthermore, for the sake of simplicity, in... Figure 3 The diagram of the lead terminals is omitted. The third side 17c has inclined surfaces 18 and 19 that are inclined in a direction that causes the central portion of the third side 17c to bulge in the vertical direction. The molding resin 14 also has a residual portion 20 provided at the central portion of the third side 17c and a tenon portion 21 provided between the inclined surface 18 and the residual portion 20. The residual portion 20 is the cutting residue after resin cutting, which will be described later. The tenon portion 21 protrudes laterally relative to the inclined surface 18 and is inclined in a direction that protrudes toward the residual portion 20. The residual portion 20 protrudes further laterally relative to the tenon portion 21 and has a fracture surface that is perpendicular in the vertical direction. The fracture surface of the residual portion 20 is a quadrilateral with a side length of a few μm to several hundred μm.

[0042] Next, the method for manufacturing the semiconductor device according to this embodiment will be described. Figure 4 This is a flowchart of the manufacturing method of the semiconductor device according to Embodiment 1. Figure 5 , Figure 7 and Figure 8This is a cross-sectional view showing the manufacturing method of the semiconductor device according to Embodiment 1. Figure 6 This is a top view illustrating the manufacturing method of the semiconductor device according to Embodiment 1. Furthermore, for the sake of simplicity, in... Figure 8 and Figure 9 The internal structure of the semiconductor device is omitted from the illustration.

[0043] First, as a preliminary step, semiconductor chips 5 and 6 are mounted on a lead frame connected to die pads 1 and 2, power terminals 3, and IC terminals 4, and wire bonding is performed (step S1). Next, the lead frame is preheated on a heating plate to expand it, and positioned in the frame positioning holes of the lower molds 22 on the left and right sides of the pot row. Next, thermosetting resin, i.e., flat molding resin 14, is placed into the pot portion of the lower mold 22. The upper mold 23 is then clamped to the lower mold 22. Thus, as Figure 5 As shown, semiconductor chips 5 and 6, power terminals 3, and IC terminals 4 are respectively arranged in multiple cavities 24 formed between the upper mold 23 and the lower mold 22. The gates of adjacent cavities 24 are connected to each other through runners 25. A resin storage section 26 is provided below the runners 25. The runners 25 are gaps formed between the upper mold 23 and the lower mold 22 and serve as channels for the resin. The resin storage section 26 is provided to increase the strength of the molding resin and prevent it from adhering to the mold during demolding.

[0044] The punch inside the vessel is raised to melt the molding resin 14 to its minimum melt viscosity. A high hydrostatic pressure of 5-15 MPa is applied through the punch, injecting the molding resin 14 from the cull portion of the mold into the cavity 24. Molding resin 14 is sequentially supplied to multiple cavities 24 via the runner 25 to encapsulate the semiconductor chip 5 and lead frames (step S2). This allows for the transfer molding of two or more lead frames in a single mold. This continuous molding of multiple semiconductor devices is called multi-row molding. This encapsulation method is characterized by low risk of forming holes in the molding section 17, high quality, and high productivity.

[0045] Next, heating is performed in this state to cure the molding resin 14. The previously clamped upper mold 23 and lower mold 22 are opened, and simultaneously, the ejector pins and punches of the upper mold 23 and lower mold 22 protrude, causing the molded part 17 to be demolded from the upper mold 23 and lower mold 22. The lead frame containing the semiconductor device and the residual material is removed from the lower mold 22. The residual material is separated from the lead frame 28 containing the semiconductor device by gate disconnection (cutting).

[0046] During this stage, such as Figure 6As shown, the molding sections 17 of multiple semiconductor devices are connected via molding resin 27 in portions of flow channels 25 and resin storage sections 26. The lead frames 28 of adjacent semiconductor devices are connected via frames 29. Furthermore, the lead frames 28 are structures that connect die pads 1 and 2, power terminals 3, IC terminals 4, and leads 30 via frames 29.

[0047] Next, in order to fully cure the molded part 17 that did not completely cure in the mold, post-curing is performed by baking in an oven (step S3). The power supply to the oven heater is turned off, and the lead frame 28 containing the semiconductor device is cooled to atmospheric temperature to increase the elastic modulus of the molded part 17.

[0048] Next, in order to remove the excess portion of the molding part 17, such as Figure 7 and Figure 8 As shown, the molding resin 27 of the flow channel 25 and the resin storage section 26 is punched from the upper surface side by the punch 31. By cutting the resin, the residue 20 remains on the third side surface 17c of the molding section 17. In order to remove the connecting rod that is formed on the lead frame 28 to prevent burrs from the molding section 17, the connecting rod is punched by the connecting rod cutting die (step S4).

[0049] Next, tin or tin-copper plating is performed on the surface of the lead frame 28, or benzotriazole (1,2,3-benzotriazole, BTA, etc.) is electroplated as an antioxidant film (step S5). This prevents the surface of the lead frame 28 from deteriorating, allowing it to be stored for a long time in high temperature and high humidity environments.

[0050] To remove excess frame material from the lead frame 28 containing the semiconductor device, the frame 29 is punched using a lead cutting die. The power terminals 3 and IC terminals 4, which are led to the outside, are bent in the direction of the upper surface of the package using a lead forming die (step S6). Electrical characteristics and appearance of the semiconductor device are tested (step S7). The completed semiconductor device is packaged and shipped (step S8).

[0051] Next, the effects of this embodiment will be explained by comparing it with a comparative example. Figure 9 This is a side view illustrating a manufacturing method of a semiconductor device involved in the comparative example. The tenon 21 is not shown in the comparative example.

[0052] Here, the molding section 17 is not completely clamped between the upper mold 23 and the lower mold 22, resulting in burrs. Additionally, the lack of clamping by the upper mold 23 and the lower mold 22 also creates thick burrs equal to the thickness of the lead frame 28. These resin burrs are removed during normal resin cutting. The width and thickness of the molding resin 27 in the flow channel 25 and the resin storage section 26 are wider and thicker than these resin burrs. Therefore, a high load-bearing capacity is required for the punch 31 of the resin cutting device.

[0053] However, the load capacity of the punch 31 is insufficient, and sometimes the load capacity of the device is insufficient due to the design of the molding die. In addition, sometimes the punch 31 contacts both ends of the molding resin 27 to be cut simultaneously, and the load from the punch 31 is not sufficiently applied. In these cases, cracks 32 may be generated from the root of the cutting residue 20 after resin cutting towards the molding part 17, causing damage to the semiconductor device. In addition, there may be a problem that the residue 20 cannot be completely cut off from the molding part 17. Furthermore, if the runner 25 is lengthened to prevent cracks 32 caused by the punching process, the residue 20 remaining on the side of the molding part 17 becomes longer, thus exceeding the product size specifications. Therefore, it is necessary to perform a punching process near the molding part 17 to shorten the residue 20.

[0054] In contrast, in this embodiment, a tenon 21 is provided at the third side 17c of the molding resin 14, between the inclined surface 18 and the residual portion 20. Therefore, even if the punch 31 contacts the tenon 21 during resin cutting, only the tenon 21 is damaged as a dead component, and no crack 32 is generated in the molding portion 17 of the molding resin 14. Furthermore, by using the tenon 21 as a marker for resin cutting, the positional accuracy of the punch 31 is improved. As a result, crack defects can be prevented.

[0055] Furthermore, the tenon 21 is inclined in the direction of protruding toward the residual portion 20. Therefore, even if the punch 31 comes into contact with the tenon 21, it will slide down along the inclined surface of the tenon 21, thereby enabling the positioning of the punch 31.

[0056] Implementation Method 2

[0057] Figure 10 This is a side view showing the semiconductor device according to Embodiment 2. In Embodiment 1, the tenon 21 is inclined, but in this embodiment, the tenon 21 has a plane that is vertical in the vertical direction. Figure 11This is a side view showing the resin cutting process of the semiconductor device according to Embodiment 2. After resin encapsulation, the molding resin 14 of the flow channel 25 is punched by a punch 31. Even when the punch 31 contacts the tenon 21 during resin cutting, only the tenon 21 is broken as a dead member, and no cracks are generated in the molding portion 17 of the molding resin 14. In addition, by cutting the resin with the tenon 21 as a marker, the positional accuracy of the punch 31 is improved. As a result, crack defects can be prevented.

[0058] Implementation Method 3

[0059] Figures 12 to 16 This is a side view illustrating a method for manufacturing a semiconductor device according to Embodiment 3. During the resin encapsulation stage, the die pads 1 and 2, power terminals 3, IC terminals 4, and leads 30 are connected as a single lead frame via frame 29 and are not separated from each other. The power terminals 3, IC terminals 4, and leads 30 are cut from frame 29 by punch 31.

[0060] At this time, as Figure 12 As shown, the lead wire 30 is punched from the lower surface of the molding resin 14 using a punch 31. Thus, as... Figure 13 As shown, the lead 30 has a fracture surface, which has a return surface on its upper side. Furthermore, the cut lead 30 is not used for electrical connection to the outside, therefore, its protrusion from the molding resin 14 is smaller compared to the power terminals 3 and IC terminals 4. The lead 30 is disposed on at least one of the first side surface 17a and the second side surface 17b where the power terminals 3 and IC terminals 4 are disposed, the third side surface where the residual portion 20 and the tenon portion 21 are disposed, and the fourth side surface opposite to the third side surface.

[0061] In addition, regarding resin cutting, as well as... Figure 14 and Figure 15 As shown, the molding resin 14 is punched from the lower surface side of the molding resin 14 through the punch 31 into a portion of the flow channel 25. In this case, the tenon 21 is provided on the lower side of the residual portion 20. This prevents crack defects. Alternatively, it can be done as follows: Figure 16 As shown, a tenon 21 with a plane perpendicular to the vertical direction is used.

[0062] like Figure 1As shown, the insulating film 15 and metal foil 16, serving as insulating and heat-dissipating materials, are disposed on the lower surfaces of the die pads 1 and 2 on which semiconductor chips 5 and 6 are mounted, and protrude from the lower surface of the molding resin 14. The semiconductor device is mounted on a heat sink, and the heat generated by the semiconductor chips 5 and 6 is dissipated to the heat sink via the insulating and heat-dissipating materials. In this embodiment, the fracture surface of the frame 29 has a rolled-back surface on the upper side, thus ensuring the distance between the front end of the frame 29 and the heat sink. As a result, high insulation can be achieved.

[0063] Implementation Method 4

[0064] Figures 17 to 19 This is a side view illustrating the manufacturing method of the semiconductor device according to Embodiment 4. Figure 17 As shown, a frame 29 supporting the die pads 1 and 2, power terminals 3, and IC terminals 4 is positioned between two adjacent cavities 24. Since the molding resin 14 is highly filled with filler, if the frame 29 is positioned in the runner 25 or resin storage section 26, the filler may become stuck in narrow gaps, potentially causing slow filling of the molding resin 14 or product defects due to insufficient filling. Therefore, in this embodiment, the frame 29 is placed inside the recess 33 provided in the lower mold 22, outside the runner 25 and resin storage section 26. This eliminates obstruction to resin flow, thus ensuring stable resin flowability.

[0065] After resin encapsulation, such as Figure 18 As shown, the molding resin 14 and frame 29 of the flow channel 25 are punched from the lower surface side of the molding resin 14 using a punch 31. By providing the tenon 21 on the lower side of the residual portion 20, crack defects can be prevented. Alternatively, it can be done as follows... Figure 19 As shown, a tenon 21 with a plane perpendicular to the vertical direction is used.

[0066] Furthermore, semiconductor chips 5 and 6 are not limited to being formed of silicon; they can also be formed of wide-bandgap semiconductors with larger band gaps compared to silicon. Examples of wide-bandgap semiconductors include silicon carbide, gallium nitride-based materials, or diamond. Semiconductor chips formed from such wide-bandgap semiconductors can be miniaturized due to their high voltage withstand capability and allowable current density. By using these miniaturized semiconductor chips, semiconductor devices assembled with them can also be miniaturized and highly integrated. Additionally, because semiconductor chips have high heat resistance, heat sink fins can be miniaturized, allowing for air cooling of water-cooled components, thus further miniaturizing semiconductor devices. Furthermore, because semiconductor chips have low power loss and high efficiency, semiconductor devices can be made more efficient.

[0067] Explanation of the label

[0068] 1. Die pad, 3. Power terminal (lead terminal), 4. IC terminal (lead terminal), 5, 6. Semiconductor chip, 14. Molding resin, 15. Insulating film (insulating and heat dissipation material), 16. Metal foil (insulating and heat dissipation material), 17. Molded part, 17a. First side, 17b. Second side, 17c. Third side, 18, 19. Inclined surface, 20. Residual part, 21. Tenon, 22. Lower mold, 23. Upper mold, 24. Cavity, 25. Runner, 29. Frame, 30. Lead wire, 31. Punch

Claims

1. A semiconductor device, characterized by comprising: have: Semiconductor chips; Lead terminals, which are connected to the semiconductor chip; and An insulating molding resin that encapsulates the semiconductor chip and a portion of the lead terminals. The molding resin has a molding portion comprising first and second side surfaces opposite to each other, and a third side surface different from the first and second side surfaces. The lead terminals protrude from the first and second sides. The third side has an inclined surface that is inclined in a direction that causes the central portion of the third side to bulge out in the vertical direction. The molding resin also has a residual portion provided at the center of the third side surface and a tenon provided between the inclined surface and the residual portion. The tenon protrudes laterally relative to the inclined surface. The residual portion protrudes laterally compared to the tenon and has a fracture surface that is perpendicular in the vertical direction.

2. The semiconductor device according to claim 1, characterized in that, The tenon is inclined in a direction that protrudes toward the remaining portion.

3. The semiconductor device according to claim 1, characterized in that, The tenon has a plane that is perpendicular in the vertical direction.

4. The semiconductor device according to any one of claims 1 to 3, characterized in that, It also has a lead wire that protrudes from at least one side of the molded portion, and the amount of protrusion from the molded portion is smaller than that of the lead wire terminal. The lead wire has a fracture surface with a rewinding surface on the upper side.

5. The semiconductor device according to claim 4, wherein It also has: A die pad on which the semiconductor chip is mounted; and An insulating and heat-dissipating material is disposed on the lower surface of the die pad.

6. The semiconductor device according to any one of claims 1 to 5, characterized in that, The semiconductor chip is formed from a wide-bandgap semiconductor.

7. A method for manufacturing a semiconductor device, comprising the method for manufacturing the semiconductor device according to any one of claims 1 to 6. The manufacturing method of this semiconductor device is characterized by having the following steps: The semiconductor chip and the lead terminal are disposed in each of the multiple cavities of the mold that are connected to each other by flow channels; The molding resin is sequentially supplied to the plurality of cavities via the flow channel to encapsulate the semiconductor chip and the lead terminals; and The molding resin in the flow channel is punched out by a punch, leaving the residue.

8. The method for manufacturing a semiconductor device according to claim 7, characterized in that, A frame, positioned between adjacent cavities and supporting the lead terminals, is disposed outside the flow channel.

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