Semiconductor device and method for manufacturing the same

Abstract

To provide a semiconductor device capable of suppressing deterioration of reliability and an insulation failure, and provide a manufacturing method for the semiconductor device.SOLUTION: A lead frame 8 connects a metal wiring of an insulation substrate 1 and an electrode 5 of a case 4. A sealing material 9 is filled into the case 4, and seals an upper surface of the insulation substrate 1, a semiconductor chip 6, and the lead frame 8. The lead frame 8 includes: a first bonding part 8a bonded to a metal wiring 3; a second bonding part 8b bonded to the electrode 5; and a connection part 8c connecting the first bonding part 8a and the second bonding part 8b. The connection part 8c includes: an inclination part 8ca that is inclined to an upper surface of the insulation substrate 1 in a cross section crossed to an extension direction of the lead frame 8; a first non-inclination part 8cb provided to between the inclination part 8ca and the first bonding part 8a; and a second non-inclination part 8cc provided to between the inclination part 8ca and the second bonding part 8b. In a boundary of the first non-inclination part 8cb and the inclination part 8ca and a boundary of the second non-inclination part 8cc and the inclination part 8ca, a slit 10 is provided to both sides of the lead frame 8.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a semiconductor device and a method for manufacturing the same.

Background Art

[0002] When bubbles remain under the lead frame during encapsulant injection, the insulation distance decreases and dielectric breakdown occurs. Also, due to the difference in the expansion rates of the bubbles and the encapsulant, the lead frame peels off during temperature cycling and the lifetime decreases. In contrast, a configuration has been proposed in which through-holes are provided in the lead frame to remove bubbles (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, if the distance that the bubbles trapped under the lead frame move to the through-holes is long, it is difficult for the bubbles to escape. For this reason, there has been a problem that it leads to a decrease in the reliability of the power module or insulation failure.

[0005] The present disclosure has been made to solve the above-described problems, and an object thereof is to obtain a semiconductor device and a method for manufacturing the same that can suppress a decrease in reliability and insulation failure.

Means for Solving the Problems

[0006] The first semiconductor device according to this disclosure comprises an insulating substrate, metal wiring provided on the upper surface of the insulating substrate, a case bonded to the outer periphery of the upper surface of the insulating substrate, a semiconductor chip mounted on the upper surface of the insulating substrate inside the case and connected to the metal wiring, electrodes provided on the case, a lead frame connecting the metal wiring and the electrodes, and a sealing material filled inside the case to seal the upper surface of the insulating substrate, the semiconductor chip and the lead frame, wherein the lead frame comprises a first bonding portion bonded to the metal wiring and the The lead frame has a second joint joined to a pole and a connecting portion that connects the first joint and the second joint, wherein the connecting portion has an inclined portion that is inclined with respect to the upper surface of the insulating substrate in a cross section that crosses the extension direction of the lead frame, a first non-inclined portion provided between the inclined portion and the first joint, and a second non-inclined portion provided between the inclined portion and the second joint, and slits are provided on both sides of the lead frame at the boundary between the first non-inclined portion and the inclined portion and the boundary between the second non-inclined portion and the inclined portion.

[0007] The second semiconductor device according to this disclosure comprises an insulating substrate, metal wiring provided on the upper surface of the insulating substrate, a case joined to the outer periphery of the upper surface of the insulating substrate, a semiconductor chip mounted on the upper surface of the insulating substrate inside the case and connected to the metal wiring, electrodes provided on the case, a lead frame connecting the metal wiring and the electrodes, and a sealing material filled inside the case to seal the upper surface of the insulating substrate, the semiconductor chip and the lead frame, wherein the lead frame has a first joint joined to the metal wiring, a second joint joined to the electrodes, and a connecting portion connecting the first joint and the second joint, and the connecting portion has an inclined portion in which the thickness changes in the width direction of the lead frame and the lower surface is inclined with respect to the upper surface of the insulating substrate in a cross section that crosses the extension direction of the lead frame. [Effects of the Invention]

[0008] In this disclosure, the lead frame is provided with an inclined portion. Therefore, when the sealing material is injected, the air below the inclined portion of the lead frame is easily pushed upward. Consequently, air bubbles are less likely to be trapped below the lead frame, thus suppressing a decrease in reliability and insulation failure. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a semiconductor device according to Embodiment 1. [Figure 2] This is a perspective view showing a lead frame according to Embodiment 1. [Figure 3] This is a plan view showing the connection portion of the lead frame according to Embodiment 1. [Figure 4] This is a cross-sectional view along line a-b in Figure 2. [Figure 5] This is a cross-sectional view showing the sealing process of a semiconductor device according to Embodiment 1. [Figure 6] This is a cross-sectional view showing a semiconductor device according to a comparative example. [Figure 7] This is a plan view showing a modified example of the connection portion of the lead frame according to Embodiment 1. [Figure 8] This is a perspective view showing a lead frame according to Embodiment 2. [Figure 9] This is a plan view showing the connection portion of the lead frame according to Embodiment 2. [Figure 10] This is a cross-sectional view along line a-b in Figure 8. [Figure 11] This is a perspective view showing a lead frame according to Embodiment 3. [Figure 12] This is a cross-sectional view along line a-b in Figure 11. [Figure 13] This is a perspective view showing a modified example of the lead frame according to Embodiment 3. [Figure 14] This is a cross-sectional view along line a-b in Figure 13. [Modes for carrying out the invention]

[0010] A semiconductor device and a method for manufacturing the same according to an embodiment will be described with reference to the drawings. The same or corresponding components may be denoted by the same reference numerals, and repeated explanations may be omitted.

[0011] Embodiment 1. FIG. 1 is a cross-sectional view showing a semiconductor device according to Embodiment 1. A heat sink 2 is provided on the lower surface of an insulating substrate 1. A metal wiring 3 is provided at the center of the upper surface of the insulating substrate 1. A case 4 is joined to the outer peripheral portion of the upper surface of the insulating substrate 1 so as to surround the metal wiring 3.

[0012] A step is provided on the upper surface of the case 4, and the upper surface on the inner peripheral side of the case 4 is lower than the upper surface on the outer peripheral side of the case 4. An electrode 5 is provided inside the case 4. The electrode 5 is drawn out from the upper surface on the inner peripheral side of the case 4 above the case 4.

[0013] A semiconductor chip 6 is mounted on the insulating substrate 1 inside the case 4. The lower surface electrode of the semiconductor chip 6 is joined to the metal wiring 3 by solder 7 and is electrically connected to the metal wiring 3. The upper surface electrode of the semiconductor chip 6 is wire-connected to another metal wiring (not shown). A lead frame 8 connects the metal wiring 3 and the electrode 5 of the case 4.

[0014] An encapsulant 9 is filled in the case 4 to encapsulate the upper surface of the insulating substrate 1, the semiconductor chip 6, the lead frame 8, etc. The lead frame 8 is not exposed from the encapsulant 9. The encapsulant 9 is a fluid gel or resin. Although the resin is cured in the completed device, it is fluid before curing during manufacturing.

[0015] FIG. 2 is a perspective view showing a lead frame according to Embodiment 1. The lead frame 8 is formed by bending a flat plate having a constant thickness. The lead frame 8 has a first joint portion 8a soldered to the metal wiring 3, a second joint portion 8b soldered to an electrode 5 provided on the upper surface on the inner peripheral side of the case 4, and a connection portion 8c connecting the first joint portion 8a and the second joint portion 8b. The first joint portion 8a and the second joint portion 8b are parallel to the upper surface of the insulating substrate 1. Since the height of the upper surface of the electrode 5 is higher than the height of the upper surface of the metal wiring 3, the connection portion 8c rises obliquely from the metal wiring 3 side toward the electrode 5 side. In other words, the connection portion 8c is inclined with respect to the upper surface of the insulating substrate 1 in a cross section along the extending direction of the lead frame 8.

[0016] FIG. 3 is a plan view showing a connection portion of the lead frame according to Embodiment 1. The connection portion 8c has an inclined portion 8ca, a first non-inclined portion 8cb provided between the inclined portion 8ca and the first joint portion 8a, and a second non-inclined portion 8cc provided between the inclined portion 8ca and the second joint portion 8b. Slits 10 are provided on both sides of the lead frame 8 at the boundary between the first non-inclined portion 8cb and the inclined portion 8ca and at the boundary between the second non-inclined portion 8cc and the inclined portion 8ca.

[0017] FIG. 4 is a cross-sectional view taken along the line a-b of FIG. 2. This cross section is a cross section cutting across the extending direction of the lead frame 8 and is perpendicular to the upper surface of the insulating substrate 1. The extending direction of the lead frame 8 is the direction from the metal wiring 3 side toward the electrode 5 side or the reverse direction, and is also the direction in which current flows through the lead frame 8. The inclined portion 8ca is twisted with respect to the first non-inclined portion 8cb and the second non-inclined portion 8cc and is inclined with respect to the upper surface of the insulating substrate 1 in a cross section cutting across the extending direction of the lead frame 8. On the other hand, the first non-inclined portion 8cb and the second non-inclined portion 8cc are not inclined in this cross section.

[0018] Figure 5 is a cross-sectional view showing the sealing process of a semiconductor device according to Embodiment 1. Because the inclined portion 8ca of the lead frame 8 is inclined, the height of the lower surface of the inclined portion 8ca on side a is lower than the height of side b, with respect to the upper surface of the insulating substrate 1. Therefore, the sealing material 9 is injected below the inclined portion 8ca of the lead frame 8, from side a to side b. This makes it easier to push air bubbles 11 below the lead frame 8 upward.

[0019] Next, the effects of this embodiment will be explained in comparison with a comparative example. Figure 6 is a cross-sectional view showing a semiconductor device according to a comparative example. In the comparative example, the lead frame 8 is not provided with an inclined portion 8ca. Therefore, when the sealing material 9 is injected, it is difficult for the air below the lead frame 8 to escape upward. Consequently, the sealing material 9 may harden with air bubbles 11 trapped in a narrow area surrounded by the inner surface of the case 4, the side surface of the metal wiring 3, the upper surface of the insulating substrate 1, and the lower surface of the lead frame 8.

[0020] On the other hand, in this embodiment, the lead frame 8 is provided with an inclined portion 8ca. Therefore, when the sealing material 9 is injected, the air below the inclined portion 8ca of the lead frame 8 is easily pushed upward. Consequently, air bubbles 11 are less likely to be trapped below the lead frame 8, thus suppressing a decrease in reliability and insulation failure.

[0021] Furthermore, in order to provide the inclined portion 8ca on the lead frame 8, it is necessary to twist the lead frame 8. However, when a normal lead frame is twisted, the inclination angle at the beginning of the twist is low, making it difficult for air bubbles 11 to escape. Therefore, in this embodiment, a slit 10 is provided in the lead frame 8 to create a twist. This allows the inclination angle θ of the inclined portion 8ca to be increased, making it easier to push the air below the lead frame 8 upwards. In addition, since the first joint portion 8a of the lead frame 8 that is joined to the metal wiring 3 of the insulating substrate 1 is kept parallel to the upper surface of the insulating substrate 1, poor contact between the lead frame 8 and the metal wiring 3 can be suppressed.

[0022] Figure 7 is a plan view showing a modified example of the connection part of the lead frame according to Embodiment 1. Since the current flows in the extension direction (Y direction) of the lead frame 8, the inductance increases as the minimum width (X direction) of the lead frame 8 narrows. Therefore, the positions of the left and right slits 10 of the lead frame 8 are shifted by a distance d1 in the extension direction (Y direction) of the lead frame 8. This makes it possible to widen the minimum width of the lead frame 8, and thus reduce the inductance.

[0023] Embodiment 2. Figure 8 is a perspective view showing a lead frame according to Embodiment 2. Figure 9 is a plan view showing the connection portion of the lead frame according to Embodiment 2. Figure 10 is a cross-sectional view along line a-b in Figure 8.

[0024] The first non-sloping portion 8cb and the second non-sloping portion 8cc are bent perpendicularly to the first joint portion 8a and the second joint portion 8b, respectively, and extend perpendicularly to the upper surface of the insulating substrate 1. The sloped portion 8ca is formed by bending the lead frame 8 at an angle θ relative to the first non-sloping portion 8cb and the second non-sloping portion 8cc, respectively. This makes it possible to easily form the sloped portion 8ca by bending the lead frame 8 alone. The other configurations of the semiconductor device are the same as in Embodiment 1. Similar to Embodiment 1, air bubbles 11 are less likely to be trapped under the sloped portion 8ca of the lead frame 8, thus suppressing a decrease in reliability and insulation failure.

[0025] Embodiment 3 Figure 11 is a perspective view showing a lead frame according to Embodiment 3. Figure 12 is a cross-sectional view taken along line a-b in Figure 11. The upper surface of the inclined portion 8ca of the lead frame 8 is parallel to the upper surface of the insulating substrate 1 in a cross-section that crosses the extension direction of the lead frame 8. On the other hand, the thickness of the inclined portion 8ca of the lead frame 8 changes in the width direction, and the lower surface of the inclined portion 8ca is inclined with respect to the upper surface of the insulating substrate 1 in that cross-section. The other configurations of the semiconductor device are the same as in Embodiment 1. Similar to Embodiment 1, air bubbles 11 are less likely to be trapped under the inclined portion 8ca of the lead frame 8, thus suppressing a decrease in reliability and insulation failure.

[0026] Figure 13 is a perspective view showing a modified example of the lead frame according to Embodiment 3. Figure 14 is a cross-sectional view taken along line a-b in Figure 13. The lower surface of the inclined portion 8ca is an inclined curved surface. This makes it easier for the air below the inclined portion 8ca to be pushed upward.

[0027] Furthermore, the semiconductor chip 6 is not limited to being made of silicon; it may also be made of a wide-bandgap semiconductor with a larger bandgap than silicon. Examples of wide-bandgap semiconductors include silicon carbide, gallium nitride-based materials, or diamond. Semiconductor chips made of such wide-bandgap semiconductors can be miniaturized because they have high voltage resistance and current density. By using these miniaturized semiconductor chips, semiconductor devices incorporating these chips can also be miniaturized and highly integrated. In addition, because semiconductor chips have high heat resistance, the heat sink fins can be miniaturized and the water-cooled section can be air-cooled, allowing for further miniaturization of the semiconductor device. Moreover, because semiconductor chips have low power loss and high efficiency, the semiconductor device can be made more efficient.

[0028] Furthermore, because the wide-bandgap semiconductor chip 6 generates a large amount of heat, it is necessary to use a encapsulating material 9 that contains a large amount of heat-resistant additives. Since a large amount of heat-resistant additives makes it easier for bubbles to form, the above embodiment is particularly effective.

[0029] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims. Various aspects of this disclosure are described below as appendices. (Note 1) Insulating substrate and A metal wiring provided on the upper surface of the insulating substrate, A case bonded to the outer periphery of the upper surface of the insulating substrate, A semiconductor chip is mounted on the upper surface of the insulating substrate inside the case and connected to the metal wiring, The electrode provided in the case, A lead frame connecting the aforementioned metal wiring and the aforementioned electrodes, The case is filled with a sealing material that seals the upper surface of the insulating substrate, the semiconductor chip, and the lead frame, The lead frame has a first joint joined to the metal wiring, a second joint joined to the electrode, and a connecting portion that connects the first joint and the second joint. The connecting portion has an inclined portion that is inclined with respect to the upper surface of the insulating substrate in a cross section that transverses the extension direction of the lead frame, a first non-inclined portion provided between the inclined portion and the first joint portion, and a second non-inclined portion provided between the inclined portion and the second joint portion. A semiconductor device characterized in that slits are provided on both sides of the lead frame at the boundary between the first non-sloping portion and the sloping portion, and at the boundary between the second non-sloping portion and the sloping portion. (Note 2) The semiconductor device according to Appendix 1, characterized in that the positions of the left and right slits of the lead frame are offset in the direction of extension of the lead frame. (Note 3) The semiconductor device according to Appendix 1 or 2, characterized in that the first non-sloping portion and the second non-sloping portion extend perpendicularly to the upper surface of the insulating substrate. (Note 4) Insulating substrate and A metal wiring provided on the upper surface of the insulating substrate, A case bonded to the outer periphery of the upper surface of the insulating substrate, A semiconductor chip is mounted on the upper surface of the insulating substrate inside the case and connected to the metal wiring, The electrode provided in the case, A lead frame connecting the aforementioned metal wiring and the aforementioned electrodes, The case is filled with a sealing material that seals the upper surface of the insulating substrate, the semiconductor chip, and the lead frame, The lead frame has a first joint joined to the metal wiring, a second joint joined to the electrode, and a connecting portion that connects the first joint and the second joint. The semiconductor device is characterized in that the connecting portion has a thickness that changes in the width direction of the lead frame, and in a cross section that crosses the extension direction of the lead frame, the lower surface is inclined with respect to the upper surface of the insulating substrate. (Note 5) The semiconductor device according to Appendix 4, characterized in that the lower surface of the inclined portion is an inclined curved surface. (Note 6) The semiconductor device according to any one of the appendices 1 to 5, characterized in that the semiconductor chip is formed of a wide-bandgap semiconductor. (Note 7) A method for manufacturing a semiconductor device as described in any one of the appendices 1 to 6, With respect to the upper surface of the insulating substrate, the height of the first side of the lower surface of the inclined portion is lower than the height of the second side. A method for manufacturing a semiconductor device, characterized by injecting the sealing material into the inclined portion below the first side and toward the second side. [Explanation of Symbols]

[0030] 1 Insulating substrate, 3 Metal wiring, 4 Case, 5 Electrode, 6 Semiconductor chip, 8 Lead frame, 9 Encapsulating material, 8a First joint, 8b Second joint, 8c Connection part, 8ca Inclined part, 8cb First non-inclined part, 8cc Second non-inclined part, 10 Slit

Claims

1. Insulating substrate and A metal wiring provided on the upper surface of the insulating substrate, A case bonded to the outer periphery of the upper surface of the insulating substrate, A semiconductor chip is mounted on the upper surface of the insulating substrate inside the case and connected to the metal wiring, The electrode provided in the case, A lead frame connecting the aforementioned metal wiring and the aforementioned electrodes, The case is filled with a sealing material that seals the upper surface of the insulating substrate, the semiconductor chip, and the lead frame, The lead frame has a first joint joined to the metal wiring, a second joint joined to the electrode, and a connecting portion that connects the first joint and the second joint. The connecting portion has an inclined portion that is inclined with respect to the upper surface of the insulating substrate in a cross section that crosses the extension direction of the lead frame, a first non-inclined portion provided between the inclined portion and the first joint portion, and a second non-inclined portion provided between the inclined portion and the second joint portion. A semiconductor device characterized in that slits are provided on both sides of the lead frame at the boundary between the first non-sloping portion and the sloping portion, and at the boundary between the second non-sloping portion and the sloping portion.

2. The semiconductor device according to claim 1, characterized in that the positions of the left and right slits of the lead frame are offset in the direction of extension of the lead frame.

3. The semiconductor device according to claim 1 or 2, characterized in that the first non-sloping portion and the second non-sloping portion extend perpendicularly to the upper surface of the insulating substrate.

4. Insulating substrate and A metal wiring provided on the upper surface of the insulating substrate, A case bonded to the outer periphery of the upper surface of the insulating substrate, A semiconductor chip is mounted on the upper surface of the insulating substrate inside the case and connected to the metal wiring, The electrode provided in the case, A lead frame connecting the aforementioned metal wiring and the aforementioned electrodes, The case is filled with a sealing material that seals the upper surface of the insulating substrate, the semiconductor chip, and the lead frame, The lead frame has a first joint joined to the metal wiring, a second joint joined to the electrode, and a connecting portion that connects the first joint and the second joint. The semiconductor device is characterized in that the connecting portion has a thickness that changes in the width direction of the lead frame, and in a cross section that crosses the extension direction of the lead frame, the lower surface is inclined with respect to the upper surface of the insulating substrate.

5. The semiconductor device according to claim 4, characterized in that the lower surface of the inclined portion is an inclined curved surface.

6. The semiconductor device according to any one of claims 1, 2, 4, or 5, characterized in that the semiconductor chip is formed of a wide-bandgap semiconductor.

7. A method for manufacturing a semiconductor device according to any one of claims 1, 2, 4, or 5, With respect to the upper surface of the insulating substrate, the height of the first side of the lower surface of the inclined portion is lower than the height of the second side. A method for manufacturing a semiconductor device, characterized by injecting the sealing material into the inclined portion below the first side and toward the second side.

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