JP2019009280A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent solder from being connected from an upper surface to a lower surface of a conductor spacer via a side surface in a semiconductor device. A semiconductor device (10) includes a semiconductor element (12) having an upper surface electrode (14) and a lower surface electrode (16), a conductor spacer (18) joined to the upper surface electrode (14) of the semiconductor element (12) via a solder (30), and an upper surface (18a) of the conductor spacer (18). The upper surface side conductor plate 20 is joined via the solder 28, and the lower surface electrode 16 of the semiconductor element 12 and the lower surface side conductor plate 22 are joined via the solder 32. On the side surface 18c of the conductor spacer 18, a blocking portion 24 projecting laterally is provided so as to go around the conductor spacer 18. [Selection diagram] Fig. 1

Description

  The technology disclosed in this specification relates to a semiconductor device.

  Patent Document 1 discloses a semiconductor device. The semiconductor device includes a semiconductor element having an upper surface electrode and a lower surface electrode, a conductor spacer bonded to the upper surface electrode via solder, an upper surface side conductor plate bonded to the upper surface of the conductor spacer via solder, and a lower surface electrode And a lower surface side conductor plate joined via solder.

JP 2016-46497 A

  In the manufacturing process of the semiconductor device described above, the semiconductor element and the conductor spacer or the conductor spacer and the upper surface side conductor plate are joined to each other by soldering. In soldering these components, the solder located on the upper and lower surfaces of the conductor spacers may spread to the side surfaces of the conductor spacers, and in some cases, solder from the upper surface of the conductor spacers to the lower surface via the side surfaces. May be connected in a series. Here, the linear expansion coefficient differs between the solder and the conductor spacer. Therefore, if the solder is connected from the upper surface to the lower surface of the conductor spacer, the thermal expansion amount of the conductor spacer may be non-uniform when the semiconductor device is used. As a result, a large stress locally acts on the semiconductor element from the conductor spacer via the solder, and there is a possibility that, for example, a top electrode of the semiconductor element may crack. In view of such circumstances, the present specification provides a technique that can prevent solder from being connected from the upper surface of the conductor spacer to the lower surface via the side surface.

  A semiconductor device disclosed in this specification includes a semiconductor element having an upper surface electrode and a lower surface electrode, a conductor spacer that is bonded to the upper surface electrode of the semiconductor element via solder, and an upper surface of the conductor spacer that is bonded to solder. And a lower surface side conductor plate joined to the lower surface electrode of the semiconductor element via solder. On the side surface of the conductor spacer, a blocking portion protruding laterally is provided so as to go around the conductor spacer.

  In the semiconductor device described above, a blocking portion is provided on the side surface of the conductor spacer. The blocking portion protrudes laterally from the side surface of the conductor spacer and is provided so as to go around the conductor spacer. According to such a configuration, even if the solder disposed on the upper and lower surfaces of the conductor spacer wets and spreads to the side surface of the conductor spacer, the wet spread is blocked by the blocking portion. Thereby, it is suppressed that a solder is connected from the upper surface of a conductor spacer to a lower surface via a side surface.

1 is a cross-sectional view of a semiconductor device 10. It is a top view which shows the conductor spacer 18 alone. It is the figure which expanded the III section in FIG. It is a modification of the conductor spacer 18 and the blocking portion 24, (A) shows a plan view, (B) shows a cross-sectional view. It is another deformation | transformation of the conductor spacer 18 and the blocking part 24, Comprising: (A) shows a top view, (B) shows sectional drawing.

  The semiconductor device 10 will be described with reference to the drawings. FIG. 1 is a cross-sectional view of the semiconductor device 10. As shown in FIG. 1, the semiconductor device 10 includes a semiconductor element 12, a conductor spacer 18, an upper surface side conductor plate 20, a lower surface side conductor plate 22, and a mold resin 26. The semiconductor element 12 is sealed in the mold resin 26. The mold resin 26 is made of an insulating material. Although not particularly limited, the material constituting the mold resin 26 may be a thermosetting resin material such as an epoxy resin.

  The semiconductor element 12 includes an upper surface electrode 14 and a lower surface electrode 16. The upper surface electrode 14 is located on the upper surface 12 a of the semiconductor element 12 and is joined to the lower surface 18 b of the conductor spacer 18 via the solder 30. The lower surface electrode 16 is located on the lower surface 12 b of the semiconductor element 12 and is joined to the upper surface 22 a of the lower surface side conductor plate 22 via the solder 32. The semiconductor element 12 is a power semiconductor element such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor). The semiconductor element 12 can be configured using various semiconductor materials such as silicon (Si), silicon carbide (SiC), or gallium nitride (GaN).

  The conductor spacer 18 is made of a conductive material such as copper or other metal. The conductor spacer 18 is generally a plate-shaped or block-shaped member, and has an upper surface 18a, a lower surface 18b located on the opposite side of the upper surface 18a, and four side surfaces 18c extending between the upper surface 18a and the lower surface 18b. The conductor spacer 18 is located in the mold resin 26. The upper surface 18 a of the conductor spacer 18 is connected to the lower surface 20 b of the upper surface side conductor plate 20 via the solder 28. As described above, the lower surface 18 b of the conductor spacer 18 is joined to the upper surface electrode 14 of the semiconductor element 12 via the solder 30. Thereby, the upper surface electrode 14 of the semiconductor element 12 is electrically connected to the upper surface side conductor plate 20 via the conductor spacer 18.

  The upper surface side conductor plate 20 and the lower surface side conductor plate 22 are configured using a conductive material such as copper or other metals. The upper surface side conductor plate 20 is a generally plate-shaped member, and has an upper surface 20a and a lower surface 20b located on the opposite side of the upper surface 20a. As described above, the lower surface 20 b of the upper surface side conductor plate 20 is joined to the upper surface 18 a of the conductor spacer 18 via the solder 28 inside the mold resin 26. On the other hand, the upper surface 20 a of the upper surface side conductor plate 20 is exposed to the outside of the mold resin 26. The upper surface side conductor plate 20 is also thermally connected to the semiconductor element 12 via the conductor spacer 18 and functions as a heat radiating plate that releases heat generated in the semiconductor element 12 to the outside.

  Similarly, the lower surface side conductor plate 22 is also a generally plate-shaped member, and has an upper surface 22a and a lower surface 22b located on the opposite side of the upper surface 22a. The upper surface 22 a of the lower surface side conductor plate 22 is joined to the lower surface electrode 16 of the semiconductor element 12 via the solder 32 inside the mold resin 26. Thereby, the lower surface side conductor plate 22 is electrically connected to the semiconductor element 12. On the other hand, the lower surface 22 b of the lower surface side conductor plate 22 is exposed to the outside of the mold resin 26. The lower surface side conductor plate 22 is also thermally connected to the semiconductor element 12 and functions as a heat radiating plate that releases heat generated in the semiconductor element 12 to the outside. That is, the semiconductor device 10 of this embodiment has a double-sided cooling structure in which the heat sink is exposed on both sides of the mold resin 26.

  As shown in FIGS. 1 to 3, the semiconductor device 10 of this example further includes a blocking unit 24. The blocking portion 24 is provided on the side surface 18c of the conductor spacer 18, and protrudes from the side surface 18c of the conductor spacer 18 to the side (direction perpendicular to the side surface 18c). Further, the blocking portion 24 makes a round of the conductor spacer 18 along the side surface 18 c of the conductor spacer 18. The blocking portion 24 is thinner than the conductor spacer 18 and is disposed near the center of the conductor spacer 18 in the thickness direction. As described above, the blocking portion 24 is a frame-like member that surrounds the conductor spacer 18 from the side. Although it is an example, the outer dimension of the blocking portion 24 when viewed in plan is preferably larger by about 1 mm to 3 mm than the outer dimension of the conductor spacer 18.

  In the manufacturing process of the semiconductor device 10, the semiconductor element 12 and the conductor spacer 18 and the conductor spacer 18 and the upper surface side conductor plate 20 are joined to each other by soldering. In the soldering of these components, the solders 28 and 30 located on the upper surface 18a and the lower surface 18b of the conductor spacer 18 may spread to the side surface 18c of the conductor spacer 18, and in some cases, the upper surface of the conductor spacer 18 Solders 28 and 30 may be connected in series from 18a to the lower surface 18b through the side surface 18c. Here, the linear expansion coefficients differ between the solders 28 and 30 and the conductor spacer 18. Therefore, if the solders 28 and 30 are connected from the upper surface 18 a to the lower surface 18 b of the conductor spacer 18, the amount of thermal expansion of the conductor spacer 18 may be uneven when the semiconductor device 10 is used. As a result, a large stress locally acts on the semiconductor element 12 from the conductor spacer 18 through the solder 30, and for example, there is a possibility that a crack is generated in the upper surface electrode 14 of the semiconductor element 12.

  Regarding the above problem, in the semiconductor device 10 of the present embodiment, the blocking portion 24 is provided on the side surface 18 c of the conductor spacer 18. The blocking portion 24 protrudes laterally from the side surface 18c of the conductor spacer 18, and is provided so as to go around the conductor spacer 18 along the side surface 18c. According to such a configuration, even if the solders 28 and 30 disposed on the upper surface 18 a and the lower surface 18 b of the conductor spacer 18 wet and spread to the side surface 18 c of the conductor spacer 18, the wet spread at the blocking portion 24. Can be blocked. Thereby, it is suppressed that the solders 28 and 30 are connected from the upper surface 18a of the conductor spacer 18 to the lower surface 18b through the side surface 18c.

  The blocking portion 24 can be formed on the conductor spacer 18 by primary insert molding, for example. Alternatively, a separately prepared frame-shaped blocking portion 24 may be fixed to the conductor spacer 18 by press-fitting. The blocking portion 24 may be formed of a material having at least a surface 24a having low affinity with the solders 28 and 30, for example, a resin. When the affinity of the blocking portion 24 with respect to the solders 28 and 30 is low, the surface tension of the solder 28 and 30 on the blocking portion 24 increases, and the solder wetting spread is effectively suppressed in the blocking portion 24. Is done. Further, at least the surface 24a of the blocking portion 24 may be made of the same material as the mold resin 26 or a material having high affinity. For example, the durability of the semiconductor device 10 is improved by chemically bonding or integrating the surface 24 a of the blocking portion 24 and the mold resin 26. Further, the blocking portion 24 is made of a material having heat resistance that is not thermally decomposed in the solder reflow process and strength that is not broken by the stress generated when the mold resin 26 is molded in the mold forming process. Good.

  As shown in FIG. 3, in the semiconductor device 10 of this example, the upper surface electrode 14 of the semiconductor element 12 has a two-layer structure. That is, the upper surface electrode 14 includes a first electrode layer 34 and a second electrode layer 36 stacked on the first electrode layer 34. In addition, the semiconductor element 12 includes a protective film 38 on the upper surface 12a. The protective film 38 extends in a frame shape along the outer peripheral edge of the upper surface 12 a of the semiconductor element 12 and covers the outer peripheral portion of the first electrode layer 34. The protective film 38 extending in a frame shape defines an opening for exposing the first electrode layer 34 by an inner peripheral edge 38a thereof. The protective film 38 is a resin material having an insulating property, and is made of, for example, polyimide. The protective film 38 has a function of maintaining the breakdown voltage of the semiconductor element 12 and a function of preventing foreign matter from coming into contact with the semiconductor element 12.

  The first electrode layer 34 is formed along the upper surface 12 a of the semiconductor element 12 and is electrically connected to the semiconductor element 12. As the material of the first electrode layer 34, for example, aluminum (Al), an aluminum alloy containing aluminum and silicon (Si), or the like can be used. The second electrode layer 36 is stacked on the first electrode layer 34 exposed from the opening of the protective film 38, and an outer peripheral portion of the second electrode layer 36 extends on the protective film 38. For example, nickel (Ni) can be used as the material of the second electrode layer 36. The solder 30 is provided on the second electrode layer 36. Three members of the first electrode layer 34, the second electrode layer 36, and the protective film 38 are gathered on the inner peripheral edge 38 a of the protective film 38. That is, the inner peripheral edge 38a of the protective film 38 has a portion where three different kinds of materials are in contact with each other. Hereinafter, the portion where these three materials are in contact with each other is referred to as a triple point 38a.

  As described above, at the triple point 38a formed in the semiconductor device 10, three types of materials are gathered. Since the three types of materials have different linear expansion coefficients, when the semiconductor device 10 operates and generates heat, the amounts of thermal expansion that occur between them also differ. As a result, a large stress acts locally at the triple point 38a, and for example, a crack may be generated in the first electrode layer 34 of the semiconductor element 12. If the local stress resulting from the wetting and spreading of the solders 28 and 30 described above further acts on the semiconductor element 12 in which such a triple point 38a exists, the generation of cracks is further promoted. In particular, if the solder 28 and 30 are thickly placed on the triple point 38a due to the wetting and spreading of the solder 28 on the conductor spacer 18, thermal stress due to thermal deformation of the conductor spacer 18 is likely to concentrate on the triple point 38a. With respect to these points, when the semiconductor element 12 has the triple point 38a, the technique disclosed in this specification, that is, the technique of preventing the connection of the solders 28 and 30 by the blocking portion 24 is more effectively adopted. can do.

  With reference to FIG. 4, a modified example of the conductor spacer 18 and the blocking portion 24 will be described. 4A and 4B show the conductor spacer 118 and the blocking portion 124 of this modification example, where FIG. 4A shows a plan view and FIG. 4B shows a cross-sectional view thereof. A concave portion 118 d is formed on the side surface 118 c of the conductor spacer 118. The blocking portion 124 is partially embedded in the recess 118 d of the conductor spacer 118. Also in this modification, the blocking portion 124 protrudes laterally (perpendicular to the side surface 118c) from the side surface 118c of the conductor spacer 118, and makes a round along the side surface 118c of the conductor spacer 118. Is provided. Further, the blocking portion 124 is thinner than the conductor spacer 118 and is disposed around the central portion in the thickness direction. According to such a configuration, the position of the blocking portion 124 is more reliably fixed on the side surface 118 c of the conductor spacer 118. Thereby, for example, in the molding process of the mold resin 26, it is possible to suppress the displacement of the blocking portion 124. The blocking portion 124 is a material having low affinity with the solders 28 and 30 and can be made of, for example, a resin.

  With reference to FIG. 5, another modified example of the conductor spacer 18 and the blocking portion 24 will be described. 5A and 5B show the conductor spacer 218 and the blocking portion 224 according to this modification, in which FIG. 5A shows a plan view and FIG. 5B shows a cross-sectional view thereof. Similar to the modification shown in FIG. 4, the conductor spacer 218 of this modification also has a recess 118d on its side surface 218c, and the blocking portion 224 is partially embedded in the recess 218d of the conductor spacer 218. ing. Also in this modification, the blocking portion 224 protrudes from the side surface 218c of the conductor spacer 218 to the side (perpendicular to the side surface 218c) and makes a round along the side surface 218c of the conductor spacer 218. Is provided. The blocking portion 224 is thinner than the conductor spacer 218 and is disposed around the central portion in the thickness direction.

  The blocking part 224 of this modification has a main body 224a and a coating layer 224b that covers the surface of the main body 224a. The main body 224a may be made of a material having a low linear expansion coefficient, such as metal, so that the apparent amount of thermal expansion of the conductor spacer 218 can be suppressed. When the apparent amount of thermal expansion of the conductor spacer 218 is suppressed, the stress acting on the solder 30 and the semiconductor element 12 is reduced, and for example, the durability of the semiconductor device 10 is improved. On the other hand, the coating layer 224b can be made of a material having the same or high affinity as the mold resin 26, such as a resin. When such a material is used, the affinity between the coating layer 224b and the solder is also reduced, and wetting and spreading of the solder can be suppressed. Alternatively, the coating layer 224b may be an oxide film obtained by oxidizing a metal constituting the main body 224a. According to such a configuration, the covering layer 224b can be formed by oxidizing the surface of the main body 224a, and the blocking portion 224 having a two-layer structure can be easily manufactured.

  Several specific examples 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 the present specification or drawings exhibit technical usefulness alone or in various combinations.

10: Semiconductor device 12: Semiconductor element 12a: Upper surface 12b of semiconductor element: Lower surface 14 of semiconductor element: Upper surface electrode 16: Lower surface electrodes 18, 118, 218: Conductor spacer 18a: Upper surface 18b of conductor spacer: Lower surface 18c of conductor spacer 118c, 218c: Side surface 20 of conductor spacer: Upper surface side conductor plate 20a: Upper surface 20b of upper surface side conductor plate: Lower surface 22 of upper surface side conductor plate: Lower surface side conductor plate 22a: Upper surface 22b of lower surface side conductor plate: Lower surface side conductor plate Lower surface 24, 124, 224: blocking portion 24a: surface of blocking portion 26: mold resin 28, 30, 32: solder 34: first electrode layer 36: second electrode layer 38: protective film 38a: protection Inner edge of membrane (triple point)
118d, 218d: Conductor spacer recess 224a: Blocking body 224b: Blocking coating layer

Claims (1)

A semiconductor element having a top electrode and a bottom electrode;
A conductor spacer bonded to the upper surface electrode via solder;
An upper surface side conductor plate joined via solder to the upper surface of the conductor spacer;
A lower-surface-side conductor plate joined to the lower-surface electrode via solder;
With
A semiconductor device, wherein a blocking portion protruding laterally is provided on a side surface of the conductor spacer so as to go around the conductor spacer.

Images