Semiconductor device and method for connecting inner lead

Abstract

To provide a semiconductor device with a junction part that can easily guarantee the quality of the junction state by making the junction part between a metal pattern of a circuit board and a lead frame (inner lead) visible, and a method for connecting inner leads that can form such junction part.SOLUTION: In a semiconductor device having a circuit board having a metal pattern on its surface, a semiconductor chip mounted on the circuit board, a lead frame containing inner leads whose ends are connected to the circuit board, and a molding resin for resin-encapsulating semiconductor chips and lead frames, the end of the inner lead has a top surface, a side surface, and a bottom surface that contacts the circuit board, and the side of the metal pattern and the side of the end of the inner lead are joined opposite each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor device and a method for connecting inner leads. [Background technology]

[0002] Conventionally, there is known a semiconductor module in which a semiconductor chip is mounted on an insulating circuit board on which a circuit pattern is formed, and the circuit pattern on the insulating circuit board to which the semiconductor chip is bonded is connected by a wiring part such as a lead frame. Fig. 6 of Patent Document 1 and its related description describe that, with the lead frame placed on the circuit pattern of the insulating circuit board, a laser beam is irradiated from above onto a bonding part to weld and bond the lead frame. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-235651 A Summary of the Invention [Problem to be solved by the invention]

[0004] When bonding is performed using the bonding method described in Patent Document 1 as above, as shown in Fig. 11, the bottom surface 4D of the end portion 4A of the inner lead 4 of the lead frame is arranged to contact the circuit pattern (metal pattern 1) of the circuit board 2, and the inner lead 4 and the circuit pattern are laminated and then irradiated with a laser L through the inner lead 4 to bond them. This means that the actual area of ​​the bonded portion is smaller than the melted area on the lead frame surface, and there is a risk that the actual bond strength will be smaller than designed. However, the bonded portion is located in a position that cannot be seen with the naked eye, and it is therefore impossible to inspect the bonded portion itself by appearance.

[0005] Fig. 12 shows the results of observing a conventional joint 10 (welded part) joined as shown in Fig. 11. Fig. 12(A) is an actual image of the inner lead joint observed from above, and Fig. 12(B) is an actual image of the circuit pattern side of the inner lead (corresponding to bottom surface 4D in Fig. 11) after the inner lead has been peeled off. It can be seen that the actual joint area at the joint (welded part) is smaller than the melted area on the surface. Since the actual joint (joint interface) itself cannot be inspected from the outside, there was a problem in that it was not easy to guarantee the quality of the joint.

[0006] The present invention has been made to solve the above problems, and aims to provide a semiconductor device having a joint that makes it possible to visually observe the joint between a metal pattern of a circuit board and a lead frame (inner lead), thereby easily ensuring the quality of the joint, and a method for connecting inner leads that can form such a joint. [Means for solving the problem]

[0007] The present invention has been made to achieve the above-mentioned object, and provides a semiconductor device comprising a circuit board having a metal pattern on its surface, a semiconductor chip mounted on the circuit board, a lead frame including an inner lead whose end is connected to the circuit board, and a molding resin that resin-seals the semiconductor chip and the lead frame, wherein the end of the inner lead has a top surface, a side surface, and a bottom surface that contacts the circuit board, and the side surface of the metal pattern and the side surface of the end of the inner lead are joined opposite each other.

[0008] According to such a semiconductor device, the joint between the metal pattern of the circuit board and the lead frame (inner lead) can be visually confirmed, so that the quality of the joint can be easily guaranteed.

[0009] In this case, the semiconductor device can be one in which the side surface of the metal pattern and the side surface of the inner lead are butt-welded.

[0010] This makes it possible to easily ensure the quality of the joint while providing a stable joint.

[0011] In this case, the metal pattern can be thinner than the inner lead, the side of the end of the inner lead is perpendicular to the surface of the circuit board, and the angle of the side of the metal pattern at the joint side with the inner lead with respect to the surface of the circuit board is less than 90 degrees.

[0012] Even for such objects, the quality of the joint can be easily ensured while providing a stable joint.

[0013] In this case, when viewed from above, at least one of the metal pattern and the end of the inner lead has at least one concave and / or convex shape, and the metal pattern and the inner lead are arranged so as to interlock with each other at the at least one concave and / or convex shape, and the side of the metal pattern and the side of the end of the inner lead are joined to form a semiconductor device.

[0014] This makes it easy to ensure the quality of the joint while also making the electrical contact and joint strength more stable.

[0015] In this case, when viewed from above, the metal pattern and the end of the inner lead each have a comb-tooth-shaped portion with a plurality of protrusions, the comb-tooth-shaped portion of the metal pattern and the comb-tooth-shaped portion of the inner lead are fitted together, and the side of the metal pattern and the side of the inner lead are joined across the respective plurality of protrusions of the metal pattern and the inner lead to form a semiconductor device.

[0016] This makes it possible to provide a more stable joint while easily ensuring the quality of the joint, and to suppress a decrease in throughput during joining.

[0017] The present invention also provides a method for connecting an inner lead to a lead frame having an inner lead with an end having a top surface, a side surface, and a bottom surface in contact with the circuit board, the method including arranging the side surface of the end of the inner lead opposite a side surface of the metal pattern and joining the side surface of the end of the inner lead arranged opposite to the side surface of the metal pattern.

[0018] According to this method of connecting the inner lead, the joint between the metal pattern of the circuit board and the lead frame (inner lead) can be visually confirmed, etc., providing a connection structure that can easily ensure the quality of the joint.

[0019] In this case, the inner lead can be connected by butt-jointing the side surface of the metal pattern and the side surface of the inner lead with laser welding.

[0020] This makes it possible to easily ensure the quality of the joint while forming a stable joint. Effect of the Invention

[0021] As described above, according to the semiconductor device of the present invention, the quality of the joint can be easily ensured. According to the method for connecting inner leads of the present invention, it is possible to provide a connection structure that can easily ensure the quality of the joint. [Brief description of the drawings]

[0022] [Figure 1] 1 shows an example (cross-sectional view) of a semiconductor device according to the present invention. [Diagram 2] FIG. 2 is a diagram (cross-sectional view) for explaining an example when a side surface of a metal pattern and an end portion of an inner lead are joined together as in the semiconductor device according to the present invention. [Diagram 3] FIG. 11 is a diagram (cross-sectional view) for explaining another example when the side surface of the metal pattern and the end portion of the inner lead are joined as in the semiconductor device according to the present invention. [Figure 4] 1 shows a state (cross-sectional view) in which a side surface of a metal pattern according to the present invention faces a side surface of an end portion of an inner lead. [Diagram 5] FIG. 2 is a cross-sectional view illustrating a bonding portion between a metal pattern and an inner lead according to the present invention. [Figure 6] 1 shows an example (top view) of a joint between a metal pattern and an inner lead according to the present invention. [Figure 7] 13 shows another example (top view) of the bonding portion between the metal pattern and the inner lead according to the present invention. FIG. [Figure 8] 13 shows another example (top view) of the bonding portion between the metal pattern and the inner lead according to the present invention. FIG. [Figure 9] An example of the bonding interface at the joint (enlarged top view) is shown. [Figure 10] 13 shows another example (top view) of the bonding portion between the metal pattern and the inner lead according to the present invention. FIG. [Figure 11] 1 is a diagram (cross-sectional view) for explaining a conventional method (joint structure) for joining an inner lead and a circuit pattern. [Figure 12] FIG. 11 shows the results of observing the bonding interface of the bonding portion (welded portion) of a conventional inner lead bonded in the manner described above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be described in detail below, but the present invention is not limited thereto.

[0024] As described above, there has been a demand for a semiconductor device having a joint that makes it possible to visually observe the joint between the metal pattern of a circuit board and a lead frame (inner lead) so that the quality of the joint can be easily guaranteed, and a method for connecting inner leads that can form such a joint.

[0025] As a result of extensive research into the above-mentioned problems, the inventors have discovered that a semiconductor device comprising a circuit board having a metal pattern on its surface, a semiconductor chip mounted on the circuit board, a lead frame including an inner lead whose end is connected to the circuit board, and a molded resin that resin-seals the semiconductor chip and the lead frame, wherein the end of the inner lead has a top surface, a side surface, and a bottom surface in contact with the circuit board, and the side surface of the metal pattern and the side surface of the end of the inner lead are joined opposite each other, thereby allowing the joint between the metal pattern of the circuit board and the lead frame (inner lead) to be confirmed visually, etc., and therefore making it easy to ensure the quality of the joint, and have completed the present invention.

[0026] The inventors have also discovered that a method of connecting an inner lead to a lead frame having an inner lead with an end having a top surface, a side surface, and a bottom surface in contact with the circuit board, in which the side surface of the end of the inner lead is arranged opposite the side surface of the metal pattern and the side surface of the metal pattern is joined to the side surface of the end of the inner lead arranged opposite the side surface of the metal pattern, allows the joint between the metal pattern of the circuit board and the lead frame (inner lead) to be visually confirmed, etc., and provides a connection structure in which the quality of the joint can be easily ensured, and thus the present invention has been completed.

[0027] The following description will be given with reference to the drawings.

[0028] [Semiconductor Devices] First, the semiconductor device according to the present invention will be described. FIG. 1 shows an example of the semiconductor device according to the present invention. FIGS. 2 and 3 are diagrams for explaining an example of bonding the side surface 1A of the metal pattern 1 and the end portion 4A of the inner lead 4 as in the semiconductor device according to the present invention, and show a state in which the circuit board 2 is placed on a jig 11. As shown in FIGS. 1 to 3, the semiconductor device 100 according to the present invention is a semiconductor device including a circuit board 2 having a metal pattern 1 on its surface, a semiconductor chip 3 mounted on the circuit board 2, a lead frame 5 including an inner lead 4 whose end portion 4A is connected to the circuit board 2, and a molded resin 6 for resin-sealing the semiconductor chip 3 and the lead frame 5. The end portion 4A of the inner lead 4 connected to the circuit board 2 has a top surface 4B, a side surface 4C, and a bottom surface 4D in contact with the circuit board 2. The side surface 1A of the metal pattern 1 and the side surface 4C of the end portion 4A of the inner lead 4 are bonded to each other in an opposed manner. If such a bonding portion 10 between the inner lead 4 and the metal pattern 1 is provided, it is possible to visually check the appearance of the bonding portion between the circuit pattern of the circuit board and the lead frame (inner lead). Therefore, the quality of the joint can be easily guaranteed.

[0029] The semiconductor device according to the present invention may be any semiconductor device in which the side surface 1A of the metal pattern 1 and the side surface 4C of the end portion 4A of the inner lead 4 are joined facing each other, and the base of the inner lead 4 may be a surface of the circuit board 2 from which the metal pattern has been removed as shown in Fig. 2, or a metal pattern as shown in Fig. 3. The circuit board 2 is not particularly limited as long as it has a metal pattern on its surface, and for example, a DBC board (Direct Bonded Copper board) in which a copper material is directly bonded to a ceramic insulating board may be used.

[0030] The joint (connection structure) between the inner lead 4 and the metal pattern 1 will be described in more detail. The side surface 1A of the metal pattern 1 and the side surface 4C of the end portion 4A of the inner lead 4 are preferably butt-welded. By providing such a connection structure, a semiconductor device having a stable joint can be obtained while easily ensuring the quality of the joint.

[0031] The materials of the inner lead 4 (lead frame 5) and the metal pattern 1 are not limited, and they may be the same material or different materials. The relationship between the thickness of the inner lead 4 and the thickness of the metal pattern 1 is also not particularly limited, and they may be the same thickness or different thicknesses. Furthermore, the side surface 4C of the end portion 4A of the inner lead 4 and the side surface 1A of the metal pattern 1 may both be perpendicular to the bottom surface (FIG. 4(A)), or at least one of them may be inclined with respect to the bottom surface (FIGS. 4(B) to (E)).

[0032] FIG. 5 shows an example of the joint between the metal pattern and the inner lead according to the present invention. As shown in FIG. 5, the metal pattern 1 can be thinner than the inner lead 4. The side surface 4C of the end portion 4A of the inner lead 4 can be perpendicular to the surface of the circuit board 2, and the angle θ of the side surface 1A of the metal pattern 1 with respect to the surface of the circuit board 2 can be less than 90 degrees. For example, the inner lead may be formed by mechanical cutting, so that the side surface of the end portion may be perpendicular to the surface of the circuit board. The metal pattern may be formed by etching, in which case the side surface 1A of the metal pattern 1 may not be perpendicular to the surface of the circuit board 2. The connection structure according to the present invention can provide a stable joint while easily ensuring the quality of the joint even in such cases. It is considered that the cross-sectional contour of the joint 10 will be as shown by the dashed line in FIG. 5 as a result of the inner frame and / or the metal pattern melting. It is also effective to apply metal powder 9 before joining by welding or the like, as shown in FIG. 4(F), to increase the contact area between the metal pattern and the inner lead.

[0033] Next, various embodiments of the joint will be described with reference to examples. In the semiconductor device according to the present invention, it is sufficient that the side surface 1A of the metal pattern 1 formed on the circuit board 2 and the side surface 4C of the end portion 4A of the inner lead 4 are joined facing each other. For example, the inner lead 4 can be disposed relative to the metal pattern 1 as shown in Figures 6(A1) and 6(A2), and the side surfaces can be joined together as shown in Figures 6(B1) and 6(B2).

[0034] Also preferred is a structure in which at least one of the metal pattern 1 and the end 4A of the inner lead 4 is provided with at least one concave and / or convex shape in a top view, and the metal pattern 1 and the inner lead 4 are arranged so as to mesh with each other at at least one concave and / or convex shape, thereby joining the side surface 1A of the metal pattern 1 and the side surface 4C of the end 4A of the inner lead 4. In this way, the joining strength of the joint can be made higher, and a more stable joint can be provided while easily ensuring quality.

[0035] Specific examples of this are shown in Figures 7 and 8. In Figure 7, one apex of the metal pattern 1 is cut away to form a recess, and the corner (protrusion) of the end of the inner lead is positioned so as to engage with the recess formed in the metal pattern 1 (Figure 7(A)), and then bonded (Figures 7(B1) and (B2)). With this type of structure, the electrical contact and bonding strength become more stable.

[0036] In FIG. 8, a recess is formed on a part of one side of the metal pattern 1, and a protrusion corresponding to the recess formed on the metal pattern 1 is provided on one side of the inner lead, and these are arranged so that the corners (protrusions) of the ends engage with the recesses formed on the metal pattern 1 (FIG. 8(A)), and then bonded (FIGS. 8(B1)-(B6)). The bonding length can be adjusted by appropriately selecting from the forms shown in FIG. 8(B1)-(B6). The longer the bonding length, the higher the bonding strength, but the longer the time required for the bonding process. Therefore, the length of the bonding region can be appropriately set within a range that ensures the bonding strength. With the structure shown in FIG. 8, it is possible to further increase the bonding strength compared to those shown in FIG. 6 and FIG. 7.

[0037] FIG. 9 is a diagram (top view) showing a preferred example of the bonding interface at the bonding portion, in which the bonding region is further enlarged. By forming minute irregularities on the side surface 1A of the metal pattern 1 and the side surface 4C of the end portion 4A of the inner lead 4 and bonding them facing each other, the contact area can be increased, and the bonding strength can be further increased. The minute irregularities may be of a regular or irregular shape. They may be corrugated with rounded corners, as in the example shown in FIG. 9. Also, linear shapes and minutely uneven shapes may be mixed. Such minute irregularities can be applied to the bonding portions of FIGS. 6 to 8 and FIG. 10 described later.

[0038] 10, it is also preferable that the end 4A of the metal pattern 1 and the inner lead 4 each have a comb-tooth-shaped portion with a plurality of protrusions when viewed from above, the comb-tooth-shaped portion 7 of the metal pattern 1 and the comb-tooth-shaped portion 8 of the inner lead 4 are engaged, and the side of the metal pattern 1 and the side of the inner lead 4 are joined across the plurality of protrusions of the metal pattern 1 and the inner lead 4. In this way, it is not necessary to join across the entire side of the opposing metal pattern 1 and the side of the inner lead 4, so that the time required for the joining process can be reduced. Therefore, it is possible to provide a stable joint with higher joining strength while easily ensuring the quality of the joint, and also to suppress a decrease in throughput in joining.

[0039] [How to connect the inner lead] Next, a method for connecting inner leads according to the present invention will be described. The method for connecting inner leads according to the present invention is a method for connecting a metal pattern of a circuit board having a semiconductor chip mounted thereon and a metal pattern on its surface to a lead frame having inner leads each having an end with a top surface, a side surface, and a bottom surface that contacts the circuit board.

[0040] As shown in Figures 6(A1), (A2), 7(A), and 8(A), a side surface 4C of an end portion 4A of an inner lead 4 is disposed opposite a side surface 1A of a metal pattern 1. Then, the side surface 4C of an end portion 4A of an inner lead 4 and the side surface 1A of a metal pattern 1 disposed opposite each other are joined. With such a method of connecting an inner lead, it is possible to visually check the joint between a circuit pattern of a circuit board and a lead frame (inner lead), and it is possible to provide a connection structure that can easily ensure the quality of the joint.

[0041] The method of joining the side 1A of the metal pattern 1 and the side 4C of the end 4A of the inner lead 4 is not particularly limited, and general welding methods such as fusion welding and brazing can be adopted. In the case of fusion welding, high energy beam welding such as laser welding and electron beam welding, gas welding, arc welding, etc. may be used. Among them, joining by laser welding is preferable. In particular, butt laser welding is preferable. A stable joint can be formed while easily ensuring the quality of the joint. In this case, it is preferable to select a wavelength of the laser that has a good absorption rate of the metal pattern and / or the inner lead. Also, welding can be performed using a laser with two wavelengths as necessary. The laser irradiation profile should be sloped to increase / decrease in consideration of reducing the variation in the melting depth. It is also effective to change the scan speed.

[0042] 5, if there is a gap between the side of the inner lead and the side of the metal pattern, stable bonding can be achieved by melting the inner lead 4 and / or the metal pattern 1 with the center of the laser L1 on the inner lead 4 side, thereby filling the gap between the inner lead 4 and the metal pattern 1. It is also effective to increase the contact area between the metal pattern and the inner lead by applying metal powder 9 before bonding by welding or the like, as shown in FIG. 4(F).

[0043] More specific aspects of the joints are as explained in the semiconductor device above.

[0044] As described above, according to the semiconductor device of the present invention, the quality of the joint can be easily ensured. According to the method for connecting inner leads of the present invention, it is possible to provide a connection structure that can easily ensure the quality of the joint.

[0045] The present specification includes the following aspects. [1]: A semiconductor device comprising: a circuit board having a metal pattern on its surface; a semiconductor chip mounted on the circuit board; a lead frame including an inner lead whose end is connected to the circuit board; and a molding resin that seals the semiconductor chip and the lead frame, wherein the end of the inner lead has a top surface, a side surface, and a bottom surface that contacts the circuit board, and the side surface of the metal pattern and the side surface of the end of the inner lead are joined facing each other. [2]: The semiconductor device of [1] above, wherein the side of the metal pattern and the side of the inner lead are butt-welded. [3]: The semiconductor device of [1] or [2] above, wherein the metal pattern is thinner than the inner lead, the side of the end of the inner lead is perpendicular to the surface of the circuit board, and the angle of the side of the metal pattern at the joint with the inner lead with respect to the surface of the circuit board is less than 90 degrees. [4]: The semiconductor device of [1], [2] or [3] above, in which, when viewed from above, at least one of the metal pattern and the end of the inner lead has at least one concave and / or convex shape, the metal pattern and the inner lead are arranged so as to interdigitate with each other at the at least one concave and / or convex shape, and a side of the metal pattern and a side of the end of the inner lead are joined. [5]: The semiconductor device of [1], [2], [3] or [4] above, in which, when viewed from above, the metal pattern and the end of the inner lead each have a comb-tooth-shaped portion with a plurality of protrusions, the comb-tooth-shaped portion of the metal pattern and the comb-tooth-shaped portion of the inner lead are fitted together, and the side of the metal pattern and the side of the inner lead are joined across the plurality of protrusions of the metal pattern and the inner lead, respectively. [6]: A method for connecting an inner lead to a lead frame having an inner lead with an end having a metal pattern on a surface of a circuit board on which a semiconductor chip is mounted and a top surface, a side surface, and a bottom surface in contact with the circuit board, the method comprising: arranging the side surface of the end of the inner lead opposite a side surface of the metal pattern; and joining the side surface of the end of the inner lead arranged opposite to the side surface of the metal pattern. [7]: The method for connecting an inner lead according to [6] above, in which a side surface of the metal pattern and a side surface of the inner lead are butt-welded by laser.

[0046] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention. [Explanation of symbols]

[0047] 1...metal pattern; 1A...side surface of metal pattern; 2...circuit board; 3...semiconductor chip; 4...inner lead; 4A...end of inner lead; 4C: Side surface of the end of the inner lead; 4D: Bottom surface of the end of the inner lead; 5...lead frame; 6...mold resin; 7... Comb-like portion (metal pattern), 8... Comb-like portion (inner lead), 9...metal powder, 10...joint, 11...jig, 100...semiconductor device. L, L1...Laser.

Claims

1. A semiconductor device comprising: a circuit board having a metal pattern on a surface thereof; a semiconductor chip mounted on the circuit board; a lead frame including inner leads whose ends are connected to the circuit board; and a molding resin for resin-sealing the semiconductor chip and the lead frame, the end of the inner lead has a top surface, a side surface, and a bottom surface that contacts the circuit board; a side surface of the metal pattern and a side surface of the end portion of the inner lead are joined to face each other.

2. 2. The semiconductor device according to claim 1, wherein a side surface of said metal pattern and a side surface of said inner lead are butt-welded.

3. the metal pattern is thinner than the inner lead; the side surface of the end portion of the inner lead is perpendicular to the surface of the circuit board; 2. The semiconductor device according to claim 1, wherein an angle of the side surface of the metal pattern, which is bonded to the inner lead, with respect to the surface of the circuit board is less than 90 degrees.

4. The semiconductor device according to claim 1, characterized in that, when viewed from above, at least one of the metal pattern and the end of the inner lead has at least one concave and / or convex shape, the metal pattern and the inner lead are arranged so as to interdigitate with each other at the at least one concave and / or convex shape, and a side of the metal pattern and the side of the end of the inner lead are joined.

5. A semiconductor device as described in any one of claims 1 to 4, characterized in that, when viewed from above, the metal pattern and the end of the inner lead each have a comb-tooth-shaped portion with a plurality of protrusions, the comb-tooth-shaped portion of the metal pattern and the comb-tooth-shaped portion of the inner lead are engaged with each other, and the side of the metal pattern and the side of the inner lead are joined across the plurality of protrusions of the metal pattern and the inner lead, respectively.

6. 1. A method for connecting an inner lead to a lead frame having an inner lead with an end portion including a top surface, a side surface, and a bottom surface that contacts the circuit board, the method comprising the steps of: A method for connecting an inner lead, characterized in that the side of the end of the inner lead and the side of the metal pattern are arranged opposite each other, and the side of the end of the inner lead arranged opposite each other and the side of the metal pattern are joined.

7. 7. The method for connecting an inner lead according to claim 6, wherein a side surface of the metal pattern and a side surface of the inner lead are butt-welded with a laser.

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