JP2019161084A - Lead frame - Google Patents

Abstract

To provide a lead frame joining two kinds of frame of different thickness, in which the part to be truncated later is reduced.SOLUTION: A lead frame 40 is used for manufacturing a semiconductor device 2 where semiconductor chips 3-6 fixed to heat slingers 12, 22 are encapsulated in a resin package 9, a power terminal 14 conducting with the semiconductor chip is extending from one face of the resin package 9, and a control terminal 15 conducting with the semiconductor chip is extending from the opposite face. The lead frame 40 includes first and second frames 42, 43 thinner than the heat slingers 12, 22. The first frame 42 is supporting the power terminal 14 and joined to the heat slingers 12, 22. The second frame 43 is supporting the control terminal 15, and located on the opposite side to the first frame 42, when viewing from the normal direction to the heat slingers 12, 22, and bonded thereto.SELECTED DRAWING: Figure 5

Description

  The technology disclosed in this specification relates to a lead frame used for manufacturing a semiconductor device.

  A semiconductor device in which a semiconductor element bonded to a metal plate is sealed in a resin package is disclosed in Patent Document 1. A power terminal extends from one surface of the resin package, and a control terminal extends from the opposite surface. When manufacturing such a semiconductor device, a lead frame in which a metal plate, a power terminal, and a control terminal are connected by a metal piece is used.

  Patent Document 2 discloses a lead frame including metal plates and terminals having different thicknesses. Making parts with different thicknesses from a single metal plate is expensive. Patent Document 3 discloses a technique in which a first frame that supports an island (metal plate) that bonds semiconductor elements and a second frame that supports terminals are bonded to form one lead frame. ing. The second frame is thinner than the first frame (including the island). That is, in the technique of Patent Document 3, a thick portion and a thin portion of the lead frame are separately formed and joined. In that case, the cost may be lower than preparing a single metal plate having portions with different thicknesses to make a lead frame.

Japanese Patent Laid-Open No. 2006-92166 JP 2013-135100 A Japanese Patent Laid-Open No. 11-97600

  The lead frame disclosed in Patent Document 3 includes a rectangular frame that surrounds the island when the second frame supporting the terminals overlaps with the first frame in plan view, and the parallel frame 2 A terminal extends from the side toward the island. That is, the second frame has a structure in which the terminal extending from the surface opposite to the terminal extending from one surface of the resin package is supported by the frame. The frame of the second frame is cut and discarded. The present specification provides a lead frame in which two types of frames having different thicknesses are joined, and the number of parts to be discarded later is reduced.

  In the lead frame disclosed in this specification, a semiconductor chip fixed to a metal plate is sealed in a resin package, and a first terminal electrically connected to the semiconductor chip extends from one surface of the resin package. This is used for manufacturing a semiconductor device in which a second terminal connected to a semiconductor chip extends from the opposite surface. The lead frame includes a first frame and a second frame that are thinner than the metal plate. The first frame supports the first terminal and is joined to the metal plate. The second frame supports the second terminal, is located on the side opposite to the first frame when viewed from the normal direction of the metal plate, and is joined to the metal plate. The lead frame disclosed in this specification separately manufactures a frame (second frame) that supports terminals located on the opposite side of the frame (first frame) that supports terminals located on one side of the resin package, They are joined to a metal plate sealed in a resin package. Therefore, a frame-like frame is not necessary, and a portion that is cut off later can be reduced.

  The resin package is made by injection molding. The metal plate to which the semiconductor element is fixed is placed in the mold cavity. In that case, the first frame and the second frame are sandwiched between the upper mold and the lower mold, and the metal plate is held in the cavity. Therefore, at least one of the first frame and the second frame may be bonded to the metal plate so as to include three bonding points that define a plane. By joining so as to include three points that define a plane (that is, three points that are not aligned on a straight line), the torsional deformation of the metal plate with respect to the first frame (or the second frame) can be suppressed. As a result, the displacement of the metal plate in the mold can be suppressed. Note that it is not necessary to be separated from the three points that define the plane. For example, the first frame (or the second frame) and the metal plate may have an L-shaped joint surface. A plane is defined at three places, both ends and corners of the L-shape.

  In the lead frame disclosed in this specification, a joint portion of the first frame or the second frame with the metal plate may extend between the edge of the metal plate and the semiconductor chip. Since the joining portion blocks moisture entering from the edge of the metal plate, the water resistance of the semiconductor device is improved.

  Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a perspective view of the semiconductor device made using the lead frame of an Example. It is sectional drawing along the II-II line of FIG. It is a disassembled perspective view of the lead frame of an Example. It is a perspective view of the lead frame of an Example. It is a perspective view of the lead frame with which the semiconductor chip was joined. FIG. 6 is a plan view of the lead frame of FIG. 5. It is a perspective view of the semiconductor device before forming a resin package. It is a perspective view of the semiconductor device after a semiconductor package formation (before a connection part removal).

  First, a semiconductor device manufactured using the lead frame of the embodiment will be described. FIG. 1 is a perspective view of the semiconductor device 2, and FIG. 2 is a sectional view taken along the line II-II in FIG. The semiconductor device 2 is a power module in which four semiconductor chips (transistors 3 and 5, diodes 4 and 6) are sealed in a resin package 9. The resin package 9 is a flat card type, and the heat sinks 15 and 25 are exposed on one wide surface, and the heat sinks 12 and 22 are exposed on the opposite wide surface. The heat dissipation plates 12, 15, 22, and 25 are embedded in the resin package 9 except for the exposed surfaces. The heat sinks 12, 15, 22, and 25 have a role of releasing heat of the semiconductor chip and a conductive path connecting the semiconductor chip electrode and the power terminal 14 (positive terminal 14a, negative terminal 14b, midpoint terminal 14c). Have a role. The transistors 3 and 5 are npn IGBTs (Insulated Gate Bipolar Transistors).

  The two transistors 3 and 5 are connected in series in the resin package 9. The transistor 5 is located on the high potential side. That is, the emitter electrode of the transistor 5 is connected to the collector electrode of the transistor 3. The diode 4 is connected in antiparallel with the transistor 3 in the resin package 9, and the diode 6 is connected in antiparallel with the transistor 5 in the resin package 9.

  Three power terminals (a positive terminal 14a, a negative terminal 14b, and a midpoint terminal 14c) extend from one narrow surface of the resin package 9, and a plurality of control terminals 15a and 15b extend from the opposite surface. Yes. The positive terminal 14 a is electrically connected to the high potential side of the series connection of the transistors 3 and 5. That is, the positive electrode terminal 14a is connected to the collector electrode of the transistor 5 on the high potential side. The negative terminal 14 b is electrically connected to the low potential side of the series connection of the transistors 3 and 5. That is, the negative terminal 14b is connected to the emitter electrode of the transistor 3 on the low potential side. The midpoint terminal 14 c is connected to the midpoint of the series connection of the transistors 3 and 5. Hereinafter, the positive terminal 14a, the negative terminal 14b, and the midpoint terminal 14c may be collectively referred to as a power terminal 14.

  The control terminal 15 a is connected to the gate electrode of the transistor 5, the sense emitter, a temperature sensor arranged in the vicinity of the transistor 5, and the like. The control terminal 15b is connected to a gate electrode of the transistor 3, a sense emitter, a temperature sensor disposed in the vicinity of the transistor 3, and the like.

  FIG. 2 shows a cross section taken along line II-II in FIG. For convenience of explanation, the + X direction of the coordinate system in FIG. 2 is expressed as “up” and the −X direction is expressed as “down”.

  The heat sinks 12 and 22 are exposed on the lower surface of the resin package 9. The heat sinks 12 and 22 are embedded in the resin package 9 except for one exposed surface. The heat sinks 15 and 25 are exposed on the upper surface of the resin package 9. The heat sinks 15 and 25 are embedded in the resin package 9 except for one exposed surface.

  The transistor 5 is joined on the heat sink 22 via the solder 8. A collector electrode 5 a is disposed on the lower surface of the transistor 5, and the collector electrode 5 a is electrically connected to the heat sink 22 via the solder 8. A copper block 7 c is joined to the upper surface of the transistor 5 via solder 8. An emitter electrode 5 b is disposed on the upper surface of the transistor 5 and is electrically connected to the copper block 7 c through the solder 8. A heat radiating plate 25 is joined to the upper surface of the copper block 7 c via solder 8. The emitter electrode 5b of the transistor 5 is electrically connected to the heat sink 25 through the solder 8 and the copper block 7c.

  The transistor 3 is joined to the heat sink 12 via the solder 8. A collector electrode 3 a is disposed on the lower surface of the transistor 3, and the collector electrode 3 a is electrically connected to the heat sink 12 via the solder 8. A copper block 7 a is joined to the upper surface of the transistor 3 via solder 8. An emitter electrode 3 b is disposed on the upper surface of the transistor 3 and is electrically connected to the copper block 7 a through the solder 8. The copper blocks 7 a and 7 c are provided for the purpose of ensuring the thickness of the resin package 9. A heat radiating plate 15 is joined to the upper surface of the copper block 7 a via solder 8. The emitter electrode 3b of the transistor 3 is electrically connected to the heat sink 15 via the solder 8 and the copper block 7a.

  Inside the resin package 9, the joint 13 extends from the edge of the heat sink 12, and the joint 26 extends from the edge of the heat sink 25. The joint 13 and the joint 26 are joined via the solder 8 and are electrically connected. The transistors 3 and 5 are electrically connected via the heat sinks 12 and 25, the joints 13 and 26, the copper block 7 c, and the solder 8. By this conduction, the transistor 3 and the transistor 5 are connected in series.

  Although not visible in FIG. 2, the diode 6 and the copper block 7 d are sandwiched between the heat sinks 22 and 25, and the diode 4 and the copper block 7 b are sandwiched between the heat sinks 12 and 15. . The transistor 5 and the diode 6 are connected in antiparallel by the heat sinks 22 and 25. The transistor 3 and the diode 4 are connected in antiparallel by the heat sinks 12 and 15.

  A junction 43 s 1 is located between the transistor 5 and the edge of the heat sink 22. As will be described in detail later, the joint 43s1 is formed on the lead frame 40 that connects the heat sinks 12 and 22 to the control terminals 15a and 15b and the power terminals 14 before the resin package 9 is formed in the manufacturing process. It is a part. The joint portion 43 s 1 extends in parallel between the edges of the transistor 5 and the heat sink 22 along the edge, and is joined to the heat sink 22 by the solder 8. An enlarged view of the range surrounded by the broken line rectangle A is shown in the lower left of FIG. An arrow B indicates a path of moisture entering from the boundary between the resin and the heat sink 22 on the outer surface of the resin package 9. As indicated by the arrow B, the joint 43s1 plays a role of lengthening the path of moisture that enters from the boundary between the resin and the heat sink 22 and approaches the transistor 5. Since the moisture intrusion path becomes longer, deterioration of the transistor 5 is suppressed. A joint 43s2 is disposed on the opposite side of the joint 43s1 in the left-right direction in the figure. The junction 43s2 also has the same effect as the junction 43s1, and suppresses the deterioration of the transistor 3.

  In the manufacturing process of the semiconductor device 2, the resin package 9 is made by injection molding. Before forming the resin package 9, as described above, the control terminals 15 a and 15 b, the power terminal 14, and the heat sinks 12 and 22 are combined into one lead frame. The lead frame will be described.

  3 is an exploded perspective view of the lead frame 40, and FIG. 4 is a perspective view of the lead frame 40. As shown in FIG. As shown in FIG. 3, the heat sinks 12 and 22, the first frame 42, and the second frame 43 are made separately in the lead frame 40. Three power terminals 14 are connected to the first frame 42. A portion connecting the adjacent power terminals 14 in the first frame 42 is referred to as a connecting portion 42a. In the positive electrode terminal 14a, the part joined to the heat sink 22 is referred to as a joint part 14s1. A portion of the midpoint terminal 14c that is joined to the heat sink 12 is referred to as a joint portion 14s2.

  The first frame 42 and the second frame 43 are thinner than the heat sinks 12 and 22. The thickness of the heat sinks 12 and 22 is defined by the function as a heat sink. On the other hand, the thickness of the first frame 42 and the second frame 43 is defined by the functions of the power terminal 14 and the control terminals 15a and 15b. Since the requirements are different from each other, the radiator plates 12 and 22 and the first frame 42 / second frame 43 have different thicknesses.

  A plurality of control terminals 15 a and 15 b are connected to the second frame 43. In the second frame 43, a portion connecting the individual control terminals 15a and 15b is referred to as a connecting portion 43a. A portion extending from one end of the connecting portion 43a and joined to the heat sink 12 is referred to as a joint portion 43s2, and a portion extending from the other end of the connecting portion 43a and joined to the heat sink 22 is referred to as 43s1.

  The first frame 42 is joined to the heat sinks 12 and 22 with solder. The second frame 43 is also joined to the heat sinks 12 and 22 with solder. As shown in FIG. 1, the power terminal 14 and the control terminals 15 a and 15 b are located on each of a pair of narrow surfaces of the resin package 9 that face each other. Therefore, the second frame 43 is located on the opposite side of the first frame 42 with the heat sinks 12 and 22 in between, as viewed from the normal direction of the heat sinks 12 and 22 (X direction in the coordinate system in the drawing). .

  The heat sinks 12 and 22 are joined to the first frame 42 and the second frame 43, and they constitute a lead frame 40 together. The lead frame 40 has portions with different thicknesses (the heat radiation plates 12 and 22 and the frames 42 and 43), which are joined after being made separately.

  A manufacturing process of the semiconductor device 2 after the lead frame 40 is manufactured is shown in FIG. After the lead frame 40 is formed, the transistor 3 and the diode 4 are joined to the heat sink 12, and the transistor 5 and the diode 6 are joined to the heat sink 22. Copper blocks 7a-7d are joined on the respective semiconductor chips.

  FIG. 6 is a plan view of a lead frame 40 in which a semiconductor chip (transistors 3 and 5 and diodes 4 and 6) and a copper block 7a-7d are joined. In FIG. 6, the resin package 9 is drawn with a virtual line. In FIG. 6, a portion painted in gray indicates a joining range S <b> 1 to S <b> 4 between the joining portion and the heat sink. The joining range S1 between the first frame 42 and the heat radiating plate 12 and the joining range S2 between the first frame 42 and the heat radiating plate 22 are expanded in an L shape. The joining ranges S1 and S2 extending in the L-shape include three points that define the plane (both ends of the L-shape and the corners of the L-shape), and thus the heat sink 12 (22) and the first frame 42 The twist between them is suppressed.

  The resin package 9 is formed by sandwiching the lead frame 40 with a mold, fixing the heat radiation plates 12 and 22 and the like in the cavity, and pouring molten resin into the cavity. When the resin package 9 is formed, the first frame 42 and the second frame 43 are sandwiched between the upper mold and the lower mold, and the heat sinks 12 and 22 are fixed. The first frame 42 and the heat radiating plates 12 and 22 are joined in the L-shaped joining ranges S1 and S2, so that the displacement of the heat radiating plates 12 and 22 in the cavity can be suppressed.

  The joining range S3 between the second frame 43 and the heat sink 12 and the joining range S4 between the second frame 43 and the heat sink 22 are both in a straight line. A plane for fixing the second frame 43 is determined by the joining ranges S3 and S4. Further, at least one of the first frame 42 and the second frame 43 is joined to each of the heat radiating plates 12 and 22 so as to include three joints that define a plane, thereby forming the resin package 9. In the cavity, it is possible to suppress the displacement (displacement in the X direction in the figure) of the heat sinks 12 and 22. Moreover, by joining so as to include three joints that define the plane, the plane of the first frame 42 (or the second frame 43) and the plane of the heat sinks 12 and 22 can be maintained in parallel. The joining range of the frame and the heat sink is not limited to the L shape, and may be three discrete points forming a triangle. When there are three terminals that are independently connected to the heat sink 12 (22), the junction between each terminal and the heat sink may form a triangle that defines a plane. Further, the number of joints may be four or more.

  On the other hand, the joint portion 43 s 2 of the second frame 43 extends along the edge of the heat sink 12 between the transistor 3 and the edge of the heat sink 12. The junction 43s2 is located between the edge of the heat sink 12 in the entire range of one side of the transistor 3. The junction range S3 between the junction 43s2 and the heat sink 12 is also along one side in the entire range of one side of the transistor 3. As described above, the joint 43 s 2 extends between the edge of the heat sink 12 and the transistor 3, thereby extending the moisture intrusion path from the boundary between the resin of the resin package 9 and the heat sink 12 to the transistor 5. This can suppress deterioration of the transistor 5. The junction 43s1 also extends between the transistor 3 and the edge of the heat sink 22 and has the same effect.

  After joining the transistors 3 and 5 and the diodes 4 and 6 to the lead frame 40, the control electrodes provided on one surface of the transistors 3 and 5 and the control terminals 15a and 15b are connected by bonding wires 51 (see FIG. 6). The positive electrode terminal 14a is joined to the heat radiating plate 22 via the joint 14s1. As described above, since the heat sink 22 is electrically connected to the collector electrode 5a of the transistor 5, the positive terminal 14a is electrically connected to the collector electrode 5a of the transistor 5. The midpoint terminal 14c is joined to the heat sink 12 via the joint 14s2. As described above, the heat sink 12 is electrically connected to the collector electrode 3 a of the transistor 3. The collector electrode 3a of the transistor 3 is electrically connected to the emitter electrode 5b of the transistor 5 through the heat sink 12 and the heat sink 25 (see FIG. 2). Therefore, the midpoint terminal 14 c is connected to the midpoint of the series connection of the transistors 3 and 5. As will be described later, the negative electrode terminal 14 b is electrically connected to the emitter electrode 3 b of the transistor 3.

  In the next manufacturing process, the heat sink 15 is joined on the copper blocks 7a and 7b, and the heat sink 25 is joined on the copper blocks 7c and 7d (see FIG. 7). As shown in FIG. 7, the joint 26 extends from the edge of the heat sink 25, and the joint 26 is joined to the joint 13 extending from the edge of the heat sink 12. In addition, a joint 16 extends from the edge of the heat radiating plate 15, and the joint 16 is joined to the end portion 14b1 of the negative electrode terminal 14b. The heat sink 15 is electrically connected to the emitter electrode 3b of the transistor 3 (see FIG. 2). Therefore, the negative electrode terminal 14 b is electrically connected to the emitter electrode 3 b of the transistor 3, that is, the negative electrode side of the series connection of the transistors 3 and 5.

  FIG. 7 corresponds to the assembly of the semiconductor device before the resin package 9 is formed. In the next manufacturing process, the assembly is put in a mold and the resin package 9 is injection-molded. As described above, the first frame 42 and the second frame 43 are sandwiched between the upper mold and the lower mold. And the heat sinks 12 and 22 are hold | maintained in a cavity. Since the first frame 42 and the heat radiating plate 12 (22) are joined in a region including three points that define a plane, the heat radiating plate 12 (22) is not easily twisted with respect to the first frame 42. Therefore, the positional deviation (the positional deviation in the X direction in the figure) of the heat sinks 12 and 22 in the cavity is suppressed. Similarly, the heat sink 12 (22) is not easily twisted with respect to the second frame 43.

  FIG. 8 shows the semiconductor device 2 after the molten resin is injected and the resin package 9 is formed. The semiconductor device 2 of FIG. 8 is a view before removing unnecessary portions (that is, the connecting portions 42a and 43a) of the lead frame 40. When the lead frame 40 is cut along the broken line CL in FIG. 8 and the connecting portions 42a and 43a are removed, the semiconductor device 2 in FIG. 1 is completed.

  The advantages of the lead frame 40 will be described. The semiconductor device 2 includes a power terminal 14 on one surface of the resin package 9, and includes control terminals 15a and 15b on the opposite surface. Therefore, the first frame 42 that supports the power terminal 14 and the second frame 43 that supports the control terminals 15a and 15b are located on the heat sinks 12 and 22 with the heat sinks 12 and 22 interposed therebetween. Located on the opposite side.

  The first frame 42 and the second frame 43 are integrated via the heat sinks 12 and 22. If a frame-shaped lead frame is formed and the power terminals 14, the control terminals 15a and 15b, and the heat sinks 12 and 22 are supported inside the frame, the entire frame is discarded as an unnecessary portion after the resin package 9 is formed. become. Since the lead frame 40 joins the first frame 42 and the second frame 43 to the heat sinks 12 and 22 remaining in the resin package 9, the portion to be cut off can be reduced. As shown in FIG. 8, only the connecting portions 42a and 43a are portions to be deleted.

  The first frame 42 is joined to the heat sink 12 (22) within a range including three points that define a plane (joining ranges S1 and S2 in FIG. 6). Therefore, the heat sink 12 (22) is less likely to twist with respect to the first frame 42. When the resin package 9 is injection molded, the first frame 42 is sandwiched between an upper mold and a lower mold for injection molding, and the heat sinks 12 and 22 are fixed in the cavity. Since the heat sinks 12 and 22 are not easily twisted with respect to the first frame 42, the positional deviation of the heat sinks 12 and 22 in the cavity can be suppressed.

  The joint portions 43s1 and 43s2 not only join the second frame 43 to the heat sinks 12 and 22, but also increase the distance until moisture entering from the boundary between the heat sinks 12 and 22 and the resin package 9 reaches the transistors 3 and 5. Also plays the role of lengthening. Therefore, deterioration over time of the transistors 3 and 5 can be suppressed. Similar to the first frame 42, the second frame 43 not only makes it difficult to twist the heat sinks 12 and 22, but also has an effect of preventing moisture from entering.

  Points to be noted regarding the technology described in the embodiments will be described. The heat sinks 12 and 22 correspond to an example of a metal plate. The power terminal 14 corresponds to an example of a first terminal. The control terminals 15a and 15b correspond to an example of a second terminal. The transistors 3 and 5 and the diodes 4 and 6 correspond to an example of a semiconductor chip.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Semiconductor device 3, 5: Transistor 4, 6: Diode 7a-7d: Copper block 8: Solder 9: Resin package 12, 15, 22, 25: Heat sink 13, 16, 26: Fitting 14: Power terminal 15a, 15b: control terminals 14s1, 14s2, 43s1, 43s2: joint 40: lead frame 42: first frame 42a, 43a: connecting part 43: second frame 51: bonding wire

Claims (3)

The semiconductor chip fixed to the metal plate is sealed in the resin package, and the first terminal connected to the semiconductor chip extends from one surface of the resin package and is connected to the semiconductor chip. A lead frame used for manufacturing a semiconductor device in which a second terminal extends from a surface opposite to the one surface;
A first frame that is thinner than the metal plate, supports the first terminal, and is joined to the metal plate;
The second plate is thinner than the metal plate, supports the second terminal, is located on the side opposite to the first frame when viewed from the normal direction of the metal plate, and is joined to the metal plate. Frame,
A lead frame for manufacturing a semiconductor device.   2. The lead frame according to claim 1, wherein at least one of the first frame and the second frame is joined to the metal plate so as to include three joints that define a plane.   The lead frame according to claim 1 or 2, wherein a joint portion of the first frame or the second frame with the metal plate extends between an edge of the metal plate and the semiconductor chip.

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