Semiconductor device and manufacturing method of semiconductor device

Abstract

To provide a semiconductor device in which a fillet shape of a solder bonding between a semiconductor element and a metal member is controlled even without providing a solder shape control member in the semiconductor element, and a manufacturing method thereof.SOLUTION: A solder 42 is arranged on a semiconductor element 3, and a metal member 5 that has a top surface 5a, a bottom surface 5b and a side surface 5c is mounted to cause the bottom surface 5b to contact on the solder 42. A distance between the semiconductor element 3 and the metal member 5 in a state where the solder 42 is melted is made larger than that before melting of the solder 42, and the solder 42 is solidified by maintaining the state. This permits a semiconductor device, in which stress applied to the semiconductor element 3 is mitigated, to be manufactured, since the solder 42 has an arc shape which is concaved toward a center in a thickness direction and a fillet angle of a part contacting with the semiconductor element 3 of the solder 42 is less than a predetermined angle.SELECTED DRAWING: Figure 4C

Description

[Technical field]

[0001] The present disclosure relates to a semiconductor device having a configuration in which a metal member is joined to a semiconductor element via solder, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, in this type of semiconductor device, it is known that the shape of the bulge of the solder that joins the metal member and the semiconductor element in contact with the semiconductor element, i.e., the fillet shape, affects the reliability of the semiconductor element. Specifically, for example, the solder may protrude from the surface of the metal member that faces the surface of the semiconductor element and creep up the side, resulting in a fillet shape that connects the surface of the semiconductor element and the side of the metal member in a substantially straight line. When the solder fillet shape is in such a state, the stress applied to the semiconductor element increases, and the reliability decreases. For example, the semiconductor device described in Patent Document 1 is known as a semiconductor device that suppresses such a decrease in reliability.

[0003] The semiconductor device described in Patent Document 1 is provided with a solder shape control member made of an insulating material that surrounds the region of a semiconductor element where solder bonding is to be performed, and the solder fillet shape is controlled. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2012-164880 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the semiconductor device described in Patent Document 1 requires that the solder shape control member be formed in advance on the semiconductor element, which raises concerns about increased manufacturing costs. For this reason, there is a demand for a simpler method of controlling the solder fillet shape.

[0006] In view of the above, the present disclosure aims to provide a semiconductor device and a manufacturing method thereof in which a semiconductor element and a metal member are solder-joined without providing a solder shape control member on the semiconductor element, and the solder is controlled to have a fillet shape that relieves the stress applied to the semiconductor element. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, a method for manufacturing a semiconductor device includes preparing a semiconductor element (3) and a metal member (5) having an upper surface (5a), a lower surface (5b), and a side surface (5c) between the upper and lower surfaces, the metal member having a planar size of a portion facing the semiconductor element smaller than that of the semiconductor element; placing solder (41) on the semiconductor element, placing the metal member inside the outer periphery of the surface of the semiconductor element on which the solder will be placed, and placing the metal member so that its underside is in contact with the solder; making the distance between the metal member and the semiconductor element in a molten state larger than that before the solder was melted; and solidifying the solder while maintaining the distance larger than that before the solder was melted.

[0008] According to this, the method for manufacturing a semiconductor device includes disposing solder between two members, a semiconductor element and a metal member, and solidifying the solder while maintaining a relatively large distance between the two members in a molten state. As a result, a part of the outer periphery of the molten solder is recessed inward from the side surface of the metal member due to surface tension, and the solder solidifies in this state, making it easy to control the fillet shape of the solder to one that rises gently toward the metal member. Therefore, a semiconductor device in which the fillet shape of the solder is controlled can be manufactured more simply without providing a solder shape control member on the semiconductor element.

[0009] According to another aspect of the present disclosure, a semiconductor device comprises a semiconductor element (3), a metal member (5) having an upper surface (5a), a lower surface (5b), and a side surface (5c) between the upper surface and the lower surface, the metal member having a planar size of a portion facing the semiconductor element smaller than that of the semiconductor element, and solder (4) joining the semiconductor element and the lower surface of the metal member, the metal member being arranged inside the periphery of the surface of the semiconductor element on which the solder is arranged, and a part of the periphery of the solder extends inside the metal member further than the side surface and covers at least a part of the side surface.

[0010] In this semiconductor device, the amount of solder between the semiconductor element and the metal member is adjusted by the excess solder adhering to the side of the metal member, so that part of the outer periphery of the solder is located inside the side of the metal member. As a result, this semiconductor device has a solder fillet shape that rises gently toward the metal member, and the stress on the semiconductor element is mitigated.

[0011] Note that the reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view illustrating an example of a semiconductor device according to a first embodiment. [Diagram 2] 2 is an enlarged cross-sectional view showing an area of ​​line II in FIG. 1. [Diagram 3] FIG. 3 is a view corresponding to FIG. 2 and is an enlarged cross-sectional view showing a crack caused by a fillet shape in the semiconductor device of the comparative example. [Figure 4A] 4 is a cross-sectional view showing a first step in soldering between a semiconductor element and a metal member in the semiconductor device of the first embodiment, when the amount of solder is equal to or less than a predetermined amount. FIG. [Figure 4B] 4B is a cross-sectional view showing a second step of soldering following FIG. 4A. [Figure 4C] FIG. 4C is a cross-sectional view showing a third step of soldering following FIG. 4B. [Figure 5A] 4 is a cross-sectional view showing a first step in soldering between a semiconductor element and a metal member in the semiconductor device of the first embodiment when a large amount of solder is used. FIG. [Figure 5B] FIG. 5B is a cross-sectional view showing a second step of soldering following FIG. 5A. [Figure 5C] FIG. 5C is a cross-sectional view showing a third step of soldering following FIG. 5B. [Figure 5D] FIG. 5D is a cross-sectional view showing a fourth step of soldering following FIG. 5C. [Figure 6] 10 is a cross-sectional view showing a soldering process when a high-temperature solder is used as the second solder. FIG. [Figure 7] 10A to 10C are cross-sectional views showing a soldering process in which the same material is used for the first to third solders. [Figure 8A] 8 is a cross-sectional view showing an example of a jig used in the soldering step of FIG. 7. [Figure 8B] 8B is a cross-sectional view showing a solder solidification step using the jig of FIG. 8A. [Figure 9A] 8 is a cross-sectional view showing another example of the jig used in the soldering step of FIG. 7. [Figure 9B] 9B is a cross-sectional view showing a solder solidification step using the jig of FIG. 9A. [Figure 10] 10 is an enlarged cross-sectional view showing a semiconductor device according to a second embodiment, the view corresponding to FIG. 2. FIG. [Figure 11] 4 is a cross-sectional view showing another example of the shape of the metal member, which corresponds to FIG. 2. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be denoted by the same reference numerals.

[0014] (First embodiment) A semiconductor device 1 according to a first embodiment will be described with reference to the drawings.

[0015] [Basic configuration example] 1, the semiconductor device 1 of this embodiment includes a semiconductor element 3, a metal member 5, and solder 4 that bonds them together. The semiconductor device 1 is preferably applied to a power semiconductor device such as a double-sided heat dissipation module having a power semiconductor element as the semiconductor element 3 and heat dissipation members connected to both sides of the semiconductor element 3 via the solder 4, but may of course be configured as other devices. In this specification, a case in which the semiconductor device 1 is configured as a double-sided heat dissipation module will be described as a representative example, although this is not intended to be limiting.

[0016] When the semiconductor device 1 is, for example, a double-sided heat dissipation module, it has a configuration including a first lead frame 2, a wire 6, a second lead frame 7, and a molded resin 8 in addition to the above-mentioned components. In the semiconductor device 1, the lead frames 2 and 7 are arranged on both sides of the semiconductor element 3 and the metal member 5, and the first lead frame 2 is connected to the back surface 3b of the semiconductor element 3, and the second lead frame 7 is connected to the front surface 3a of the semiconductor element 3 via the metal member 5. The semiconductor device 1 has a double-sided heat dissipation structure in which parts of the lead frames 2 and 7, the semiconductor element 3, the solder 4, the metal member 5, and the wire 6 are sealed in the molded resin 8, and the surfaces of the lead frames 2 and 7 opposite to the semiconductor element 3 are exposed from the molded resin 8.

[0017] The first lead frame 2 is made of a conductive material such as a metal such as Cu (copper) or Fe (iron) or an alloy thereof, and is formed by press punching or the like. The first lead frame 2 includes, for example, a heat sink 21, a first terminal 22 extending from the heat sink 21, and a second terminal 23 independent from the heat sink 21. In the first lead frame 2, the semiconductor element 3 is joined to one surface 21a of the heat sink 21 via solder 4, and the other surface 21b of the heat sink 21 is exposed from the molded resin 8. The first lead frame 2 has the first terminal 22 and the second terminal 23 protruding from the side surface of the molded resin 8, and can be electrically connected to the semiconductor element 3 via the terminals 22 and 23.

[0018] The semiconductor element 3 is, for example, in the form of a plate having a front surface 3a and a back surface 3b, and is mainly made of semiconductor materials such as Si (silicon) and SiC (silicon carbide). The semiconductor element 3 is, for example, a power semiconductor element such as an IGBT or a power MOSFET, and is manufactured by a known semiconductor process. IGBT is an abbreviation for Insulated Gate Bipolar Transistor, and MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. The semiconductor element 3 is configured such that, for example, a gate electrode and an emitter electrode or a source electrode (not shown) are formed on the front surface 3a, and a collector electrode or a drain electrode (not shown) are formed on the back surface 3b. The front surface 3a side of the semiconductor element 3 is connected to the metal member 5 via the solder 4, the second terminal 23 via the wire 6, and the back surface 3b side is connected to the heat sink 21 via the solder 4.

[0019] 2, the semiconductor element 3 includes a semiconductor substrate 31, an insulating film 32 made of an insulating material such as polyimide, an electrode film 33 made of a conductive material such as Al (aluminum), and a plating film 34 made of a conductive material such as Ni (nickel). The semiconductor element 3 is configured such that the electrode film 33 is exposed from the insulating film 32 at openings of the insulating film 32 having a predetermined pattern shape, and the plating film 34 is laminated on the electrode film 33. In the semiconductor element 3, the plating film 34 is bonded to a metal member 5 via solder 4, for example.

[0020] The solder 4 is made of a bonding material mainly composed of Sn (tin) and is used to bond the components of the semiconductor device 1. Hereinafter, for convenience of explanation, the solder 4 that bonds the first lead frame 2 and the semiconductor element 3 is referred to as the "first solder 41", and the solder that bonds the semiconductor element 3 and the metal member 5 is referred to as the "second solder 42". In addition, the solder 4 that bonds the metal member 5 and the second lead frame 7 is referred to as the "third solder 43". The first solder 41 to the third solder 43 may be made of the same material or different materials. At least the second solder 42 has an end that is narrowed toward the center in the thickness direction by a bonding process of the semiconductor element 3 and the metal member 5 described later, as shown in FIG. 2, for example, in order to reduce stress concentration on the semiconductor element 3 and improve reliability. Hereinafter, as shown in FIG. 2, the end of the outer periphery of the second solder 42 that contacts the semiconductor element 3 will be referred to simply as the "fillet," and the angle between the fillet and the bonding surface of the semiconductor element 3 (e.g., the plating film 34) will be referred to as the "fillet angle α."

[0021] The metal member 5 is made of a conductive material such as metal such as Cu or its alloy, and is disposed between the semiconductor element 3 and the second lead frame 7 and joined to each of them via the solder 4. The metal member 5 electrically connects the semiconductor element 3 and the second lead frame 7, and serves to secure a predetermined gap between the semiconductor element 3 and the second lead frame 7 or more, thereby preventing the wire 6 from contacting the second lead frame 7. The metal member 5 may also be called a "metal block" or a "terminal". The metal member 5 has a planar size that fits within the outer periphery of the surface 3a of the semiconductor element 3 on which the second solder 42 is disposed. In other words, when viewed from the normal direction to the surface 3a, the metal member 5 has a planar size smaller than that of the semiconductor element 3, and is disposed so that the entire area of ​​the metal member 5 fits within the surface 3a of the semiconductor element 3.

[0022] 1 and 2 show a typical example in which the entire planar size of the metal member 5 is smaller than that of the semiconductor element 3, but the present invention is not limited to this. For example, the metal member 5 may have a configuration in which at least the portion facing the semiconductor element 3, i.e., the connection portion, has a planar size smaller than that of the semiconductor element 3, and the portion other than the connection portion has a planar size larger than that of the semiconductor element 3. Specifically, for example, the metal member 5 may have a protruding connection portion that is larger in planar size than the semiconductor element 3 like a lead frame, and be joined in a state in which the connection portion is disposed inside the outer periphery of the semiconductor element 3.

[0023] The metal member 5 is, for example, a rectangular plate-like member. For convenience of explanation, the surface of the metal member 5 on the second lead frame 7 side will be referred to as the "upper surface 5a", the opposite surface will be referred to as the "lower surface 5b", and the surface between the upper surface 5a and the lower surface 5b will be referred to as the "side surface 5c". At least a portion of the side surface 5c of the metal member 5, including the end portion on the lower surface 5b side, is covered with the second solder 42 by a manufacturing process described later.

[0024] The wires 6 are made of a conductive material such as Au (gold), etc. The wires 6 are connected to electrode portions (not shown) and terminals 22 formed on the front surface 3a of the semiconductor element 3 by wire bonding, and electrically connect them.

[0025] The second lead frame 7 is made of the same conductive material as the first lead frame 2, and is formed by press punching or the like. The second lead frame 7 is disposed on the opposite side of the first lead frame 2, with the semiconductor element 3 and the metal member 5 sandwiched between them. The second lead frame 7 has one surface 7a opposite the semiconductor element 3 exposed from the molded resin 8, and the other surface 7b opposite the one surface 7a joined to the upper surface 5a of the metal member 5 via the solder 4. The second lead frame 7 is configured such that, for example, a portion soldered to the metal member 5 serves as a heat sink, and has a terminal (not shown).

[0026] The mold resin 8 is made of a thermosetting resin material such as epoxy resin, and is formed by any resin molding method such as compression molding using a mold (not shown).

[0027] The above is the basic configuration of the semiconductor device 1 when it is used as a double-sided heat dissipation module. The semiconductor device 1 has a structure in which the fillet angle α of the second solder 42 is controlled by a simple process of adjusting the distance between the semiconductor element 3 and the metal member 5 when they are joined by the solder 4.

[0028] [Solder fillet angle control] Next, a description will be given of the process of joining the semiconductor element 3 and the metal member 5 in the manufacture of the semiconductor device 1 of this embodiment, and the control of the fillet angle α in this process.

[0029] First, a comparative semiconductor device in which a semiconductor element 3 and a metal member 10 are obtained by a conventional solder bonding process and the problem therewith will be described.

[0030] In conventional soldering, solder 4 is applied to plating film 34 surrounded by insulating film 32 of semiconductor element 3, and then a rectangular metal block is mounted as metal member 10, for example, on the solder 4, and the solder 4 is heated and solidified to bond the semiconductor element 3 and metal member 10. Metal member 10 has a smaller planar size than plating film 34 of semiconductor element 3, and is disposed so as to be entirely contained within the outer periphery of plating film 34, and is bonded and fixed by solder 4. In the semiconductor device of the comparative example, as shown in FIG. 3, the entire area of ​​lower surface 10a of metal member 10 facing plating film 34 is bonded to plating film 34 by solder 4.

[0031] In the semiconductor device of the comparative example, the solder 4 has an outer surface that connects the end of the side wall surface 10b of the metal member 10 adjacent to the lower surface 10a and the surface of the semiconductor element 3 in a substantially straight line, and the fillet angle α is large. In this case, as shown by the white arrow in FIG. 3, the stress F1 caused by the solder 4 acts on the plating film 34 of the semiconductor element 3, and since the fillet angle α is large, the direction of the stress F1 is more upward. According to the experiments of the present inventors, it was found that in the semiconductor device of the comparative example, the stress F1 caused by the solder 4 is concentrated particularly at the point where the boundaries of the insulating film 32, the electrode film 33, and the plating film 34 overlap (hereinafter referred to as the "triple point"), and a crack C originating from the triple point occurs. When this crack C occurs, the crack C progresses to the semiconductor element 3, and the reliability of the semiconductor device decreases.

[0032] In order to suppress the occurrence of such cracks C originating from the triple junction, it is effective to reduce the fillet angle α of the solder 4, that is, to make the shape of the end portion, which is the outer surface of the solder 4, narrow toward the center in the thickness direction. As a result, as shown in FIG. 2, for example, the direction of the stress F1 acting on the triple junction is more downward than in the comparative example, and the occurrence of cracks C can be suppressed. Therefore, in the semiconductor device 1 of this embodiment, the semiconductor element 3 and the metal member 5 are joined by the process described below, and the shape of the second solder 42 is controlled so that the fillet angle α is small.

[0033] Next, a first bonding method between semiconductor element 3 and metal member 5 will be described with reference to FIGS. 4A to 4C.

[0034] In Fig. 4B, the outlines of the metal member 5 and the second solder 42 before the metal member 5 is lifted are shown by dashed lines, and the direction of change in position due to lifting is shown by a hollow arrow. In Fig. 4C, the outline of the second solder 42 before solidification is shown by dashed lines, and the direction of change in the outline is shown by a hollow arrow. In Figs. 4A to 4C, for ease of viewing, members connected to the back surface 3b side of the semiconductor element 3 are omitted. This also applies to Figs. 5A to 5D described below.

[0035] First, as shown in Fig. 4A, for example, the second solder 42 is applied to the plating film 34 of the semiconductor element 3, and the metal member 5 is placed on the second solder 42. The second solder 42 is not melted at this point, and the fillet angle of the portion in contact with the semiconductor element 3 is set to α0, where α0 is larger than α. For convenience of explanation, the distance between the semiconductor element 3 and the metal member 5 before the second solder 42 melts is set to D0 below. The distance D0 can also be said to be the distance between the semiconductor element 3 and the metal member 5 along the thickness direction of the semiconductor element 3, i.e., the normal direction to the surface of the semiconductor element 3.

[0036] 4B, the second solder 42 is melted and the metal member 5 is lifted using a jig (not shown) or the like, thereby setting the distance between the semiconductor element 3 and the metal member 5 to D1, which is larger than D0. As a result, the second solder 42 is pulled from the semiconductor element 3 side to the metal member 5 side. The jig may be, for example, a suction jig having a suction mechanism that vacuum-sucks the upper surface 5a of the metal member 5, or may be one that indirectly lifts the metal member 5 using a jig 100 (described later) that lifts the lead frame 7 connected to the upper surface 5a of the metal member 5.

[0037] Next, as shown in Fig. 4C, for example, the second solder 42 is solidified while maintaining the state of Fig. 4B, that is, the distance between the semiconductor element 3 and the metal member 5 at D1. As a result, the second solder 42 is recessed toward the center in the thickness direction due to surface tension and contraction during solidification, and solidifies in a constricted state like a roughly circular arc. As a result, the end of the second solder 42 in contact with the semiconductor element 3 is shaped so that it gently rises toward the metal member 5, and the fillet angle α becomes smaller than α0.

[0038] When the amount of the second solder 42 is equal to or less than a predetermined amount, for example, it is possible to control the fillet shape of the second solder 42 by the above-mentioned process.

[0039] Next, a second bonding method for bonding semiconductor element 3 and metal member 5 will be described with reference to FIGS. 5A to 5D. Here, the differences from the first bonding method will be mainly described.

[0040] The amount of second solder 42 may vary due to factors such as unavoidable errors in the manufacturing process of a semiconductor device. When the amount of solder is large, the fillet shape of second solder 42 can be controlled more stably by inserting a process of pressing metal member 5 once toward semiconductor element 3 before lifting it.

[0041] First, for example, as shown in FIG. 5A, a second solder 42 is applied to the plating film 34 of the semiconductor element 3, and then a metal member 5 is placed on the second solder 42. If the amount of solder is large, the distance between the semiconductor element 3 and the metal member 5 becomes D2, which is larger than D0.

[0042] 5B, the second solder 42 is heated and melted, and the metal member 5 is pressed toward the semiconductor element 3 by a jig (not shown). At this time, the distance between the semiconductor element 3 and the metal member 5 becomes D3, which is smaller than D2. As a result, the second solder 42 is pressed outward from the lower surface 5b, and an excess portion adheres to the side surface 5c, while the amount of the portion located between the lower surface 5b and the plating film 34 is optimized.

[0043] 5C, for example, the metal member 5 is lifted by a jig (not shown) to set the distance between the semiconductor element 3 and the metal member 5 to D4, which is larger than D3. As a result, the portion of the second solder 42 located between the lower surface 5b and the plating film 34 is pulled from the semiconductor element 3 side toward the metal member 5, with the excess portion remaining attached to the side surface 5c of the metal member 5.

[0044] 5D, for example, the second solder 42 is solidified while maintaining the state of FIG. 5C, that is, the distance between the semiconductor element 3 and the metal member 5 at D4. As a result, the second solder 42 becomes recessed toward the center in the thickness direction due to surface tension and contraction during solidification, and solidifies in a constricted state in a substantially arc shape.

[0045] When the amount of the second solder 42 exceeds a predetermined amount, for example, as in the above-mentioned process, it is possible to more stably control the fillet shape of the second solder 42 by once attaching the excess portion of the second solder 42 to the side surface 5c of the metal member 5. Note that D1 and D4 are, for example, but not limited to, about 50 μm to 150 μm.

[0046] [Manufacturing method including first joining step] When a high-temperature solder having a higher melting point than the third solder 43 is used for the first solder 41 and the second solder 42, the shape of the second solder 42 can be controlled, for example, by a joining process shown in Fig. 6. In Fig. 6, for ease of viewing, the first lead frame 2 and the semiconductor element 3 are shown in a simplified manner, and the lifting direction of the metal member 5 is indicated by a thick arrow.

[0047] The first lead frame 2 is fixed by suction using a mounter device (not shown), the first solder 41 is applied, and the semiconductor element 3 is placed on the first solder 41. After that, the second solder 42 is applied to the front surface 3a side of the semiconductor element 3, and the metal member 5 is placed on the second solder 42. The first solder 41 and the second solder 42 may be arranged by placing a solder foil. Next, as shown in FIG. 6, for example, the work is heated to melt the first solder 41 and the second solder 42, and the metal member 5 is pushed toward the semiconductor element 3 side, and then the metal member 5 is lifted by a suction jig (not shown). By solidifying the melted first solder 41 and the second solder 42 in this state, the first solder 41 and the second solder 42 are formed into a constricted shape that is recessed toward the center in the thickness direction compared to other parts, and are fixed in a state in which the fillet angle α is controlled.

[0048] Next, the wire 6 is connected to the semiconductor element 3, a third solder 43 composed of a solder having a lower melting point than the first solder 41 and the second solder 42 is applied to the upper surface 5a of the metal member 5, and the second lead frame 7 is placed on it. The third solder 43 is then heated to a temperature lower than the melting points of the first solder 41 and the second solder 42, melted, and then solidified. This prevents the first solder 41 and the second solder 42 from remelting, and maintains their fillet shapes. Finally, resin sealing is performed to manufacture the semiconductor device 1.

[0049] [Manufacturing method including second joining step] When the solders 41 to 43 are made of the same material, the shape of the second solder 42 can be controlled by, for example, a bonding process shown in Fig. 7. For ease of viewing, the lead frames 2, 7 and semiconductor element 3 are shown in a simplified manner and the wire 6 is omitted in Fig. 7. The positions of the second lead frame 7 and metal member 5 before being pressed in are also shown by dashed lines in Fig. 7.

[0050] First, the first lead frame 2 is fixed by suction using a mounter device (not shown), the first solder 41 is applied, the semiconductor element 3 is placed on the first solder 41, and the first solder 41 is heated to melt and then solidified to bond the first lead frame 2 and the semiconductor element 3. Next, for example, after bonding the wire 6 to the semiconductor element 3, the second solder 42 is applied to the front surface 3a of the semiconductor element 3, and the metal member 5 is placed on the second solder 42. Next, the third solder 43 is applied to the upper surface 5a of the metal member 5, and the second lead frame 7 is placed on the third solder 43. The first solder 41, the second solder 42, and the third solder 43 may be arranged by a method of placing solder foil. 7, the work is heated to melt the solders 41-43, and the metal member 5 is pressed into the semiconductor element 3 via the second lead frame 7 by a weight or the like (not shown), and then the distance between the semiconductor element 3 and the metal member 5 is increased by using a jig 100 (described later). The solders 41-43 are then solidified while keeping the distance between the semiconductor element 3 and the metal member 5 large, so that the solders 41-43 are constricted toward the center in the thickness direction, more recessed than other portions, and are fixed in a state in which the fillet angle α is controlled. Finally, the semiconductor device 1 is manufactured by performing resin sealing.

[0051] Next, a first example of the jig 100 will be described with reference to Figures 8A and 8B. Note that in Figures 8A and 8B, similar to Figure 7, the lead frames 2, 7 and the semiconductor element 3 are simplified, and the wires 6 are omitted. Also, in Figures 8A and 8B, the direction of force acting on the workpiece due to pressing or the like is indicated by white arrows. The same applies to Figures 9A and 9B described below.

[0052] As shown in FIG. 8A, the jig 100 includes a base 101 on which a workpiece in the middle of manufacturing the semiconductor device 1 is placed, and a number of supports 102 arranged around an area of ​​the base 101 on which the workpiece is placed. In the jig 100, for example, the heights of the parts of the supports 102 protruding from the base 101, i.e., the support heights, are made substantially uniform. In the jig 100, for example, the second lead frame 7 is placed on the tip surfaces of the multiple supports 102, and the multiple supports 102 function as supports that support the second lead frame 7. The jig 100 is configured such that the support heights can be adjusted by, for example, pushing up the multiple supports 102 from the base 101. In the jig 100, for example, at the time when the second lead frame 7 is placed, the support heights of the multiple supports 102 are fixed at a predetermined height. At this time, the work is stacked in the following order from the base 101 side: first lead frame 2, first solder 41, semiconductor element 3, second solder 42, metal member 5, third solder 43, and second lead frame 7. Then, by placing a weight (not shown) on one surface 7a of the second lead frame 7, the metal member 5 is pressed towards the semiconductor element 3 via the second lead frame 7, and the distance between the metal member 5 and the semiconductor element 3 is reduced.

[0053] As shown in FIG. 8B, the jig 100 heats the workpiece, melts the solders 41 to 43, and then pushes up the multiple support posts 102 to make the support post height larger than the initial height. As a result, the second lead frame 7 of the workpiece is lifted and the metal member 5 is also lifted, so that the distance between the semiconductor element 3 and the metal member 5 is larger than before the second solder 42 melts. Then, the jig 100 is maintained in a state in which the multiple support posts 102 are pushed up and the support post height is increased, and the solders 41 to 43 are solidified, so that the fillet shape of the solders 41 to 43 is fixed in an approximately arc shape. By using such a jig 100, it is possible to control the fillet shape of the second solder 42 that joins the semiconductor element 3 and the metal member 5 without performing a pretreatment or the like on the semiconductor element 3 in advance.

[0054] Next, a second example of the jig 100 will be described with reference to Figures 9A and 9B. Here, differences from the second example will be mainly described.

[0055] In the second example, the jig 100 is completely fixed in a state in which the support height of the multiple supports 102 is higher than in the first example, and the support height does not fluctuate during the process of joining the semiconductor element 3 and the metal member 5. The jig 100 further includes a thermally elastic member 110 that expands when the solders 41-43 melt, and the workpiece is placed on the thermally elastic member 110.

[0056] The thermally elastic member 110 is made of a predetermined material that thermally expands when heated to melt the solders 41 to 43, and thermally contracts when cooled to solidify the solders 41 to 43, returning to its original size. The thermally elastic member 110 is made of any material that has a large thermal expansion coefficient and does not change state at least at the melting point of the solders 41 to 43, that is, has higher heat resistance than the solders 41 to 43, such as a metal material such as zinc or aluminum or an alloy material thereof. As shown in FIG. 9A, for example, in the heating process to melt the solders 41 to 43, the thermally elastic member 110 pushes the first lead frame 2 toward the second lead frame 7 by thermal expansion, thereby reducing the distance between the semiconductor element 3 and the metal member 5. At this time, the second lead frame 7 placed on the tip surface of the multiple supports 102 has a weight (not shown) or the like placed on one surface 7a, so that the position of the thermally elastic member 110 does not change when the thermally elastic member 110 is thermally expanded.

[0057] 9B, in the cooling step of solidifying the solders 41-43, the thermally elastic member 110 thermally contracts, causing the first lead frame 2 to move away from the second lead frame 7 under its own weight. That is, in the step of solidifying the solders 41-43, the thermally elastic member 110 plays a role in increasing the distance between the semiconductor element 3 and the metal member 5 via the first lead frame 2. As a result, in the workpiece, the distance between the semiconductor element 3 and the metal member 5 is reduced when the solders 41-43 are melted, and the distance increases when the solders 41-43 are subsequently solidified, so that the fillets of the solders 41-43 have an approximately arc shape.

[0058] The thermally elastic member 110 is, for example, rectangular plate-like, but its shape and dimensions are arbitrary and are appropriately changed depending on the heating temperature when the solders 41-43 are melted and the thermal expansion coefficient at that temperature, etc. Also, the thermally elastic member 110 is not limited to the above-mentioned material examples, and may be composed of other metal materials having higher heat resistance than the solders 41-43.

[0059] According to this embodiment, in the soldering of the semiconductor element 3 and the metal member 5, the distance between the metal member 5 and the semiconductor element 3 is increased while the second solder 42 is molten, and the second solder 42 is solidified, thereby forming a semiconductor device 1 in which the fillet shape of the second solder 42 is controlled. That is, by controlling the distance between the semiconductor element 3 and the metal member 5 during soldering, the second solder 42 solidifies and shrinks, forming a constricted arc shape recessed toward the center in the thickness direction, and the fillet angle α on the semiconductor element 3 side is controlled to a small shape less than a predetermined value. In addition, the distance between the semiconductor element 3 and the metal member 5 is once reduced according to the amount of the second solder 42 during the soldering of the semiconductor element 3 and the metal member 5, so that the excess portion of the second solder 42 is attached to the side surface 5c of the metal member 5. This allows the amount of solder between the semiconductor element 3 and the metal member 5 to be optimized, and ensures the accuracy of the shape control of the second solder 42. Therefore, even without providing a solder shape control member on the semiconductor element 3, the fillet angle α of the portion of the second solder 42 that contacts the semiconductor element 3 is controlled to be less than a predetermined value, resulting in a semiconductor device 1 having a configuration in which the stress applied to the semiconductor element 3 is alleviated.

[0060] Second embodiment The semiconductor device 1 of the second embodiment will be described with reference to the drawings.

[0061] 10, the semiconductor device 1 of this embodiment differs from the first embodiment in that the metal member 5 has a solder leading portion 51. In this embodiment, this difference will be mainly described.

[0062] In this embodiment, the solder guide portion 51 is a portion of the metal member 5 that connects the side surface 5c and the lower surface 5b. The solder guide portion 51 is, for example, a surface different from the lower surface 5b and the side surface 5c, and is a region that has a planar shape, but is not limited thereto, and may be a curved surface having a curved shape or may be composed of multiple surfaces, and the shape is appropriately changed. The solder guide portion 51 becomes a space into which the excess portion of the solder 4 flows when the metal member 5 is joined to the semiconductor element 3 with the solder 4, and plays a role in enhancing the effect of making the fillet angle α equal to or smaller than a predetermined value. The solder guide portion 51 is formed by any method, such as cutting.

[0063] In addition, the solder guide portion 51 may be processed by Au flash or pre-soldering to make the solder 4 more wettable than the underside 5b, or no special processing to improve the wettability of the solder 4 may be performed, and the wettability of the solder 4 may be about the same as that of the underside 5b.

[0064] The inclination angle, height, and width of the solder guiding portion 51 can be appropriately changed depending on the volume of the excess portion of the solder 4. The "inclination angle" here refers to the angle between the plane of the solder guiding portion 51 and the lower surface 5b, the "height" refers to the width of the solder guiding portion 51 along the thickness direction of the metal member 5, and the "width" refers to the width of the solder guiding portion 51 along the planar direction of the metal member 5. The thickness direction of the metal member 5 refers to the direction connecting the upper surface 5a and the lower surface 5b, and the planar direction refers to the direction parallel to the plane formed by the lower surface 5b.

[0065] The present embodiment also provides a semiconductor device 1 and a manufacturing method thereof that can obtain the same effects as those of the first embodiment. In addition, since the metal member 5 has the solder guide portion 51, a space is created into which the excess portion of the second solder 42 flows when the semiconductor element 3 and the metal member 5 are joined, making it easier for the second solder 42 to have a constricted shape, and improving the control effect of reducing the fillet angle α.

[0066] (Modification of the second embodiment) The solder guide portion 51 may not have a planar shape connecting the lower surface 5b and the side surface 5c, but may be a recess provided in the side surface 5c near the end of the lower surface 5b side and at a position away from the end, as shown in FIG. 11. In this case, the solder guide portion 51 functions as a groove-like space into which a part of the surplus portion of the second solder 42 flows when the surplus portion of the second solder 42 wets and spreads on the side surface 5c of the metal member 5 during bonding between the semiconductor element 3 and the metal member 5. The solder guide portion 51 functions as an adjustment structure for the surplus portion of the second solder 42, and plays a role in making the second solder 42 more likely to have a constricted shape. When the solder guide portion 51 is a recess provided on the side surface 5c, the shape and size of the recess are arbitrary and can be changed as appropriate. The solder guide portion 51 is provided at least in a range of the side surface 5c where the molten second solder 42 creeps up when the metal member 5 is pressed into the semiconductor element 3 side.

[0067] This modification also provides the semiconductor device 1 and the manufacturing method thereof that can provide the same effects as those of the second embodiment.

[0068] (Other embodiments) (1) Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element thereof, more than one, or less than one, are also within the scope and concept of the present disclosure.

[0069] (2) In the above first embodiment, when the solders 41 to 43 are made of the same material, an example has been described in which the second lead frame 7 is lifted or the first lead frame 2 is separated from the second lead frame 7 by its own weight in the process of solidifying the solders 41 to 43, but the reverse may also be true. For example, the second lead frame 7, the third solder 43, the metal member 5, the second solder 42, the semiconductor element 3, the first solder 41, and the first lead frame 2 are stacked in this order from the base 101 side of the jig 100. Then, in the process of solidifying the solders 41 to 43, the first lead frame 2 is lifted by the multiple supports 102, or the second lead frame 7 is separated from the first lead frame 2 by its own weight due to the contraction of the thermal expansion and contraction member 110. This also increases the distance between the semiconductor element 3 and the metal member 5 in the process of solidifying the solders 41 to 43, makes the second solder 42 into a substantially arcuate shape, controls the fillet shape, and relieves the stress on the semiconductor element 3.

[0070] (3) It goes without saying that in each of the above embodiments, the elements constituting the embodiment are not necessarily essential, except when expressly stated as essential or when it is clearly considered essential in principle. In addition, in each of the above embodiments, when the numbers, values, amounts, ranges, etc. of the components of the embodiment are mentioned, they are not limited to the specific numbers, except when expressly stated as essential or when it is clearly limited to a specific number in principle. In addition, in each of the above embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc., except when expressly stated as essential or when it is clearly limited to a specific shape, positional relationship, etc. in principle. [Explanation of symbols]

[0071] 3...semiconductor element, 4...solder, 42...second solder, 43...third solder, 5...metal member 5a...upper surface 5a...lower surface 5c...side surface 51...solder guide portion 7...lead frame 100: jig, 101: base, 102: support

Claims

1. preparing a semiconductor element (3) and a metal member (5) having an upper surface (5a), a lower surface (5b) and a side surface (5c) between the upper surface and the lower surface, the planar size of a portion facing the semiconductor element being smaller than that of the semiconductor element; Placing solder (42) on the semiconductor element, placing the metal member on the inner periphery of the surface of the semiconductor element on which the solder is to be placed, and placing the metal member so that the lower surface of the metal member is in contact with the solder; a distance between the metal member and the semiconductor element in a state in which the solder is melted is made larger than a distance between the metal member and the semiconductor element before the solder is melted; and solidifying the solder while maintaining the distance greater than before the solder was melted.

2. Providing a lead frame (7); placing the metal member on the lead frame so that the upper surface of the metal member is in contact with the lead frame via solder (43); preparing a jig (100) having a base (101) on which a workpiece having the semiconductor element, the metal member, and the lead frame connected via solder is placed, and a plurality of supports (102) for supporting the lead frame; 2. The method for manufacturing a semiconductor device according to claim 1, wherein the increasing of the distance is performed by setting the workpiece on the jig and extending the plurality of supports to lift up the lead frame.

3. Providing a lead frame (7); placing the metal member on the lead frame so that the upper surface of the metal member is in contact with the lead frame via solder (43); preparing a jig (100) having a base (101) on which a workpiece having the semiconductor element, the metal member, and the lead frame connected via solder is placed, and a plurality of supports (102) for supporting the lead frame; The method further includes disposing a thermal expansion member (110) on the base, the thermal expansion member expanding when the solder is melted and contracting when the solder is solidified, and placing the work on the thermal expansion member; 2. The method for manufacturing a semiconductor device according to claim 1, wherein the step of increasing the distance is performed by contracting the thermally expandable member while the lead frame is supported by the plurality of supports.

4. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the step of increasing the distance is performed by directly lifting up the metal member.

5. 2. The method for manufacturing a semiconductor device according to claim 1, further comprising the steps of: before increasing the distance, making the distance smaller than before the solder melts, and attaching the solder to the side surface.

6. A method for manufacturing a semiconductor device according to any one of claims 1 to 5, wherein in preparing the metal member, a solder guide portion (51) is formed at a portion connecting the side surface and the bottom surface, the solder guide portion being a flat or curved surface different from the side surface and the bottom surface.

7. 6. The method for manufacturing a semiconductor device according to claim 1, wherein the metal member is prepared by forming a solder guide portion (51) recessed on the end side of the lower surface of the side surface.

8. A semiconductor device comprising: A semiconductor element (3); a metal member (5) having an upper surface (5a), a lower surface (5b), and a side surface (5c) between the upper surface and the lower surface, the metal member having a planar size smaller than that of the semiconductor element; and solder (4) for joining the semiconductor element and the lower surface of the metal member, the metal member is disposed on an inner side of an outer periphery of a surface of the semiconductor element on which the solder is disposed, A semiconductor device, wherein a portion of the solder extends into the metal member further inside than the side surface and covers at least a portion of the side surface.

9. 9. The semiconductor device according to claim 8, wherein the metal member has a solder guide portion (51) formed at a portion connecting the side surface and the bottom surface, the solder guide portion having a flat or curved surface different from the side surface and the bottom surface.

10. 9. The semiconductor device according to claim 8, wherein said metal member has a solder guide portion (51) formed as a recess on an end side of said lower surface of said side surface.

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