Semiconductor device, electric appliance, and determination method for bonding state

Abstract

To provide a semiconductor device that can secure easily the quality of a bonding state between a metal pattern of a circuit board and a lead frame (inner lead), and provide a determination method for a bonding state, in which the quality of the bonding state between the metal pattern of the circuit board and the lead frame (inner lead) can be easily secured.SOLUTION: A semiconductor device includes a circuit board having a metal pattern on a surface, a semiconductor chip mounted on the circuit board, a lead frame including an inner lead having an end part connected to the circuit board, and a mold resin that seals with resin the semiconductor chip and the lead frame. The inner lead and the circuit board are bonded together by laser welding with an upper surface of the metal pattern and a lower surface of the end part of the inner lead facing each other. On the metal pattern, a bonding state determination unit is formed of a material with a melting point lower than those of the materials of the inner lead and the metal pattern.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor device, an electric device, and a method for determining a bonding state. [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 performing bonding using the bonding method described in Patent Document 1 as above, as shown in Fig. 6, the lead frame is arranged so that the underside 14B of the end 14A of the inner lead 14 of the lead frame contacts the circuit pattern (metal pattern 11 on ceramic substrate 12) of the circuit board 13 on which the semiconductor chip 10 is mounted, and the inner lead 14 and the circuit pattern are laminated and then irradiated with a laser L through the inner lead 14 to bond them together. For this reason, the area of ​​the actual laser welded portion 18 is smaller than the melted area of ​​the laser irradiated portion 19 on the lead frame surface, and there is a risk that the actual bonding strength will be smaller than designed. However, the bonding portion is located in a position that cannot be seen with the naked eye, and it is impossible to inspect the bonding portion itself by appearance.

[0005] Fig. 7 shows an actual image of the surface of the end 14A of the inner lead 14 bonded as shown in Fig. 6. As shown in Fig. 7, it can be seen that the inner lead has melted at the laser irradiated portion 19 where the laser L has been irradiated, but it is impossible to tell from the outside what the state of the laser welded portion 18 at the bonding interface between the underside of the end 14A of the inner lead 14 and the metal pattern 11 is. Therefore, there was a problem in that it was not easy to guarantee the quality of the bonding state.

[0006] The present invention has been made to solve the above problems, and aims to provide a semiconductor device that can easily ensure the quality of the bonding state between a metal pattern of a circuit board and a lead frame (inner lead), and a method for determining the bonding state that can easily ensure the quality of the bonding state between a metal pattern of a circuit board and a lead frame (inner lead). [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 molded resin that resin-seals the semiconductor chip and the lead frame, wherein the inner lead and the circuit board are joined by laser welding such that an upper surface of the metal pattern faces a lower surface of the end of the inner lead, and the semiconductor device is provided with a bonding condition determination portion on the metal pattern, the bonding condition determination portion being made of a material having a lower melting point than the material of the inner lead and the metal pattern.

[0008] Such a semiconductor device makes it possible to easily determine the bonding condition between the metal pattern of the circuit board and the lead frame (inner lead), and makes it easy to ensure the quality of the bonding portion (laser welded portion).

[0009] In this case, the metal pattern can be a semiconductor device having an extension portion that extends outward from the joint between the end of the inner lead and the metal pattern when viewed from above, and the extension portion is provided with the joint condition determination portion.

[0010] This allows the extension portion and the bonded state determination portion to be disposed at desired positions, resulting in a semiconductor device with high design freedom.

[0011] In this case, the semiconductor device may be such that the bond condition determining portion is disposed so as to protrude outward from the end portion of the inner lead when viewed from above.

[0012] Such a bonding condition determination portion can be easily placed on the metal pattern, making it possible to more stably and easily determine the bonding condition between the metal pattern of the circuit board and the lead frame (inner lead).

[0013] In this case, the semiconductor device may be configured such that the joint condition determining section is made of solder material.

[0014] This makes it possible to more stably and easily determine the bonding state between the metal pattern of the circuit board and the lead frame (inner lead).

[0015] In this case, the semiconductor device can be included in an electrical device.

[0016] This makes it possible to provide an electric device with improved reliability.

[0017] The present invention has been made to achieve the above-mentioned object, and provides a method for determining a bonding condition when a metal pattern provided on the surface of a circuit board on which a semiconductor chip is mounted and an end of an inner lead of a lead frame are joined by laser welding, the method comprising the steps of: providing a bonding condition determination section on the metal pattern of the circuit board, the bonding condition determination section being made of a material having a lower melting point than the material of the inner lead and the metal pattern; a bonding section aligning process in which the upper surface of the metal pattern and the lower surface of the end of the inner lead are brought into contact with each other and stacked; a bonding process in which a laser is irradiated from the upper surface side of the end of the inner lead to laser weld the metal pattern and the inner lead; and a step of determining whether the bonding condition between the metal pattern and the inner lead is good or bad from a change in the melting state of the bonding condition determination section before and after the bonding process.

[0018] According to such a method for determining the bonding condition, it is possible to easily determine the bonding condition between the metal pattern of the circuit board and the lead frame (inner lead), and the quality of the bonding condition can be easily guaranteed. Effect of the Invention

[0019] As described above, according to the semiconductor device of the present invention, it is possible to easily judge the bonding state between the metal pattern of the circuit board and the lead frame (inner lead), and the quality of the bonding portion (laser welded portion) can be easily guaranteed. According to the bonding state judgment method of the present invention, it is possible to easily judge the bonding state between the metal pattern of the circuit board and the lead frame (inner lead), and the quality of the bonding state can be easily guaranteed. [Brief description of the drawings]

[0020] [Figure 1] 1 shows an example (cross-sectional view) of a semiconductor device according to the present invention. [Diagram 2] 1 shows another example (top view) of a semiconductor device according to the present invention. [Diagram 3] 1 shows an example (top view) of a joint condition determination section provided near the joint between a metal pattern and an inner lead. [Figure 4] 1A to 1C are views (sectional views) for explaining a method for determining a bonding state according to the present invention. [Diagram 5] 11 is a diagram (top view) for explaining an example of a method for installing a joint condition determining unit. FIG. [Figure 6] 1 is a diagram (cross-sectional view) for explaining a conventional method (joint structure) for joining an inner lead and a circuit pattern. [Figure 7] 1 shows the results of observing the surface of a laser welded portion of a conventional inner lead. [Figure 8] FIG. 1 is a diagram illustrating an air conditioner as an embodiment of an electrical device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The present invention will be described in detail below, but the present invention is not limited thereto.

[0022] As described above, there was a need for a semiconductor device that can easily ensure the quality of the bonding state between a metal pattern of a circuit board and a lead frame (inner lead), and a method for determining the bonding state that can easily ensure the quality of the bonding state between a metal pattern of a circuit board and a lead frame (inner lead).

[0023] As a result of extensive investigations 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 inner lead and the circuit board are joined by laser welding such that an upper surface of the metal pattern faces a lower surface of the end of the inner lead, and the metal pattern is provided with a joint condition determination section made of a material having a lower melting point than the material of the inner lead and the metal pattern, making it possible to easily determine the joint condition between the metal pattern of the circuit board and the lead frame (inner lead) and to easily ensure the quality of the joint (laser welded section), and have completed the present invention.

[0024] The inventors have also discovered that a method for judging a bonding condition when a metal pattern provided on the surface of a circuit board on which a semiconductor chip is mounted and an end of an inner lead of a lead frame are joined by laser welding, the method comprising the steps of: providing a bonding condition judging portion on the metal pattern of the circuit board, the bonding condition judging portion being made of a material having a lower melting point than the material of the inner lead and the metal pattern; a bonding portion aligning step of bringing an upper surface of the metal pattern into contact with a lower surface of the end of the inner lead and stacking them together; a bonding step of irradiating a laser from the upper surface side of the end of the inner lead to laser weld the metal pattern and the inner lead together; and a step of judging whether the bonding condition between the metal pattern and the inner lead is good or bad from a change in the melting state of the bonding condition judging portion before and after the bonding step, thereby making it possible to easily judge the bonding condition between the metal pattern of a circuit board and a lead frame (inner lead) and easily guarantee the quality of the bonding condition, and have completed the present invention.

[0025] The following description will be given with reference to the drawings.

[0026] [Semiconductor Devices] FIG. 1 shows an example of a semiconductor device according to the present invention. As shown in FIG. 1, the semiconductor device 100 according to the present invention includes a circuit board 13 having a metal pattern 11 on its surface, a semiconductor chip 10 mounted on the circuit board 13, a lead frame 15 including an inner lead 14 whose end 14A is connected to the circuit board 13, and a molded resin 16 that resin-seals the semiconductor chip 10 and the lead frame 15. The semiconductor device 100 according to the present invention also includes a laser welded portion 18 in which the upper surface of the metal pattern 11 and the lower surface of the end 14A of the inner lead 14 face each other and are joined by laser welding. The semiconductor device 100 according to the present invention includes a bonded state determination portion 17 on the metal pattern 11, the bonded state determination portion 17 being made of a material having a lower melting point than the materials of the inner lead 14 and the metal pattern 11. With a semiconductor device including such a bonded state determination portion 17, it is possible to easily grasp the welding state of the laser welded portion 18 from the appearance of the bonded state determination portion 17. Therefore, the quality of the joint (laser welded portion 18) can be easily guaranteed.

[0027] There are no particular limitations on the circuit board 13 as long as it has a metal pattern 11 on its surface. For example, a DBC board (Direct Bonded Copper board) in which copper material is directly bonded as the metal pattern 11 to both sides of an insulating ceramic board 12 can be used.

[0028] Fig. 2 shows an example of an intelligent power module (IPM) 200, which is a specific example of a semiconductor device. The IPM 200 in Fig. 2 is a semiconductor device that includes a plurality of semiconductor chips 10 on a DBC substrate (circuit substrate 13) and has bonding state determination units 17A to 17D in the vicinity of ends of inner leads 14.

[0029] The materials of the inner lead (lead frame) and the metal pattern are not limited, and they may be the same or different materials. The relationship between the thickness of the inner lead and the thickness of the metal pattern is also not particularly limited, and they may be the same thickness or different thicknesses.

[0030] The material of the bonding state determination portion is not particularly limited as long as it has a lower melting point than the material of the inner lead and the metal pattern. When such a bonding state determination portion is provided on the metal pattern, the heat generated when the inner lead and the metal pattern are laser-welded is transmitted through the metal pattern, melting the material constituting the bonding state determination portion. From the change in the melting state at this time, the quality of the bonding state of the inner lead and the metal pattern can be easily determined. The change in the melting state can be grasped by observing the appearance. For example, it is observed as a change in the gloss of the bonding state determination portion or a change in the shape of the bonding state determination portion. In other words, by observing the bonding state determination portion, the bonding quality can be indirectly monitored.

[0031] As a result of extensive research into the above-mentioned joint condition judgment part, the inventors have found that even when a solder material with a relatively low melting point (lead-free solder material) is used, if there is a change in the appearance (gloss) of the solder material before and after laser welding, the joint condition is good.

[0032] Since the melting point of copper used as the metal pattern on the DBC board is 1085°C, and the melting point of the lead-free solder material is about 210°C, it is considered that the laser joint generates heat of 1085°C or more, and the temperature on the metal pattern is higher than 210°C due to heat transfer. Even with solder materials other than lead-free solder materials, those that showed a change in the appearance (gloss) of the solder material before and after laser welding had a good joint condition. Based on these study results, it is preferable for the material used for the joint condition judgment part to have a melting point of 150°C or more. In addition, the upper limit of the melting point of the material used for the joint condition judgment part should be lower than the melting point of the material of the metal pattern, but considering the ease of material procurement and the arrangement of the joint condition judgment part, it can be preferably 500°C or less, more preferably 400°C or less.

[0033] In particular, solder material is used when bonding a semiconductor chip onto a metal pattern, and is used in ordinary semiconductor devices, so that when it is used as the bonding state determination part, it does not adversely affect the semiconductor device. Therefore, it is preferable that the material of the bonding state determination part is solder material. When solder material is used as the material of the bonding state determination part, the semiconductor device can be easily determined the bonding state between the metal pattern of the circuit board and the lead frame (inner lead) more stably. In addition, when the material of the bonding state determination part is solder material, the bonding state determination part can be provided at the same time as the solder material for bonding the semiconductor chip is provided, so there is no decrease in productivity due to the provision of the bonding state determination part.

[0034] Examples of solder materials include eutectic solder and lead-free solder. Eutectic solder contains lead, is 63% tin (Sn) and 37% lead (Pb), and has a melting point of approximately 180°C. Lead-free solder is 96.5% tin (Sn), 3.0% silver (Ag), and 0.5% copper (Cu), and has a melting point of approximately 210°C. In addition to these, various general solder alloys and only tin (Sn) (melting point approximately 230°C) can also be used.

[0035] Next, various arrangements of the bonded state determining section will be described with reference to examples. Fig. 3 is a diagram showing various embodiments of the bonded state determining section in the semiconductor device according to the present invention.

[0036] The bonding condition determination portion according to the present invention may be provided at a position spaced apart from the inner lead 14, such as bonding condition determination portion 17A in Figures 2 and 3(A) and bonding condition determination portion 17B in Figures 2 and 3(B), or may be provided along the end (edge) of the inner lead 14, such as bonding condition determination portion 17C in Figures 2 and 3(C).

[0037] 2 and 3(D), it may be arranged so as to protrude outward from the end (edge) of the inner lead 14. Such a bonding condition determining portion can be easily arranged on the metal pattern, resulting in a semiconductor device that can more stably and easily determine the bonding condition between the metal pattern of the circuit board and the lead frame (inner lead).

[0038] 2 and 3(A), the bonding condition determination portion 17A is provided with an extension portion 20 on the metal pattern 11, which extends outward from the bond between the end of the inner lead 14 and the metal pattern 11, and the bonding condition determination portion 17A is provided on this extension portion 20. This type of semiconductor device is preferable because it allows the extension portion and the bonding condition determination portion to be disposed at desired positions, allowing for high design freedom.

[0039] Since the metal pattern has a very high thermal conductivity, heat from the welded portion during laser welding is easily transferred. Therefore, the bonding state determination unit of the semiconductor device according to the present invention only needs to be provided on the metal pattern formed on the circuit board, and the position on the metal pattern is not particularly limited. The installation position of the bonding state determination unit can be appropriately set depending on the design of the metal pattern, etc., but it is preferable to place it at a position where the shortest distance from the end of the inner lead is 0.3 mm or less, because this allows for more stable determination of the bonding state.

[0040] [Electrical Equipment] The above-mentioned semiconductor device can be applied to electrical equipment. The use of a semiconductor device in electrical equipment, which can easily ensure the quality of the joints (laser welded parts) and has improved reliability, contributes to improving the reliability of the electrical equipment. The electrical equipment is not particularly limited, but in particular, the above-mentioned example of the semiconductor device (IPM) 200 can be suitably applied as a small high-voltage three-phase motor driver to electrical equipment for driving compressors in air conditioners, refrigerators, etc.

[0041] 8 is a diagram illustrating an air conditioner 300 as one embodiment of an electrical device. The air conditioner 300 is composed of an indoor unit 310 and an outdoor unit 320, each of which is equipped with fan motors 311, 321, a compressor 322, and an electrical device, an IPM 200. It is preferable to use IPM 200 with specifications suitable for driving the respective motors and compressors.

[0042] [Method of determining bonding condition] Next, a method for determining the joining condition when joining a metal pattern provided on the surface of a circuit board on which a semiconductor chip is mounted and an end of an inner lead of a lead frame by laser welding will be described with reference to FIG.

[0043] (Step of Providing a Joint State Determination Unit) As shown in Fig. 4(A), first, a bonding state determination section 17 made of a material having a lower melting point than the material of the inner lead 14 and the metal pattern 11 is provided on the metal pattern 11 of the circuit board 13. Fig. 4(A) shows an embodiment in which the bonding state determination section 17 is provided on the metal pattern 11 where the semiconductor chip 10 has already been provided, but as described above, when a solder material is used as the bonding state determination section 17, the solder material for bonding the semiconductor chip 10 can be used, and the solder material for the bonding state determination section 17 and the solder material for bonding the semiconductor chip 10 can be arranged in the same process. In this case, a decrease in productivity due to the provision of the bonding state determination section 17 can be suppressed.

[0044] (Joint fitting process) Next, as shown in FIG. 4(B), the upper surface of the metal pattern 11 and the lower surface of the end 14A of the inner lead 14 of the lead frame 15 are placed in a laminated manner so as to be in contact with each other.

[0045] (Joining process) Next, as shown in Fig. 4(C), a laser L is irradiated from the upper surface side of the end portion 14A of the inner lead 14 to laser weld the metal pattern 11 and the inner lead 14. At this time, the laser L may be scanned and irradiated. The scanning direction of the laser L can be appropriately set according to the shape of the object to be welded, and for example, scanning and irradiating can be performed as shown in the laser irradiation section 19 in Fig. 3 etc.

[0046] (Process for determining whether the bonding state is good or bad) 4(D), the quality of the bonded state between the metal pattern 11 and the end 14A of the inner lead is judged from the change in the melting state of the bonded state judging portion 17 before and after the bonding process. If the bonded state judging portion 17 is provided on the metal pattern 11, the heat generated when the end 14A of the inner lead and the metal pattern 11 are laser-welded is transmitted through the metal pattern, melting the material that constitutes the bonded state judging portion 17. From the change in the melting state at this time, the quality of the bonded state between the end 14A of the inner lead and the metal pattern 11 can be easily judged.

[0047] The change in the melting state can be grasped by observing the appearance. Specifically, it is observed as a change in gloss or shape of the joint state judgment part. For example, when a solder material is used as the material of the joint state judgment part 17, the change in the melting state can be seen by the fact that the glossiness becomes higher after melting by the heat of laser welding compared to before melting. It is also possible to judge the change in the melting state from the change in the shape of the solder material. When it is confirmed that the melting state of the joint state judgment part has changed, it can be judged that the joint state of the end part 14A of the inner lead and the metal pattern 11 is good. On the other hand, when it is not confirmed that the melting state of the joint state judgment part has changed, it can be judged that the joint state of the end part 14A of the inner lead and the metal pattern 11 is poor.

[0048] In addition, when the bonding state determination portion is arranged so as to protrude outward from the end 14A of the inner lead 14 as seen from above, as in the bonding state determination portion 17D in Fig. 2 and Fig. 3(D), a material to become the bonding state determination portion 17D may be arranged on the metal pattern 11 as shown in Fig. 5(A), the end 14A of the inner lead may be arranged so as to overlap the material as shown in Fig. 5(B), and laser irradiation may be performed as shown in Fig. 5(C). When the bonding state determination portion 17D is arranged in this manner, the positioning accuracy does not need to be high, so the bonding state determination portion can be easily arranged on the metal pattern, and since the bonding state determination portion and the inner lead are in contact with each other, the bonding state between the metal pattern of the circuit board and the lead frame (inner lead) can be more stably and more easily determined.

[0049] In this way, it is possible to easily determine the bonding condition between the metal pattern of the circuit board and the lead frame (inner lead), and a method for judging the bonding condition that can easily ensure the quality of the bonding condition has been provided.

[0050] As described above, according to the semiconductor device of the present invention, it is possible to easily judge the bonding state between the metal pattern of the circuit board and the lead frame (inner lead), and the quality of the bonding portion (laser welded portion) can be easily guaranteed. According to the bonding state judgment method of the present invention, it is possible to easily judge the bonding state between the metal pattern of the circuit board and the lead frame (inner lead), and the quality of the bonding state can be easily guaranteed.

[0051] 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 with resin, wherein the inner lead and the circuit board are joined by laser welding such that an upper surface of the metal pattern faces a lower surface of the end of the inner lead, and the semiconductor device comprises a joining condition determination portion on the metal pattern, the joining condition determination portion being made of a material having a lower melting point than the material of the inner lead and the metal pattern. [2]: The semiconductor device of [1] above, wherein the metal pattern has an extension portion that extends outward from a joint between the end of the inner lead and the metal pattern when viewed from above, and the extension portion is provided with the joint condition determination portion. [3]: The semiconductor device according to [1] above, wherein the bonding condition determining portion is disposed so as to protrude outward from the end of the inner lead when viewed from above. [4]: The semiconductor device according to [1], [2] or [3] above, wherein the joint condition determining portion is made of a solder material. [5]: An electric device including the semiconductor device according to [1], [2], [3] or [4] above. [6]: A method for determining a bonding condition when a metal pattern provided on a surface of a circuit board on which a semiconductor chip is mounted and an end of an inner lead of a lead frame are joined by laser welding, the method comprising the steps of: providing a bonding condition determination portion on the metal pattern of the circuit board, the bonding condition determination portion being made of a material having a lower melting point than the material of the inner lead and the metal pattern; a bonding portion aligning step of contacting an upper surface of the metal pattern with a lower surface of the end of the inner lead and stacking them; a bonding step of irradiating a laser from the upper surface side of the end of the inner lead to laser weld the metal pattern and the inner lead; and a step of determining whether the bonding condition between the metal pattern and the inner lead is good or bad based on a change in the melting state of the bonding condition determination portion before and after the bonding step.

[0052] 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]

[0053] 10...semiconductor chip, 11...metal pattern, 12...ceramic substrate, 13...circuit board; 14...inner lead; 14A...end of inner lead; 14B: lower surface of end of inner lead; 15: lead frame; 16...molding resin; 17, 17A, 17B, 17C, 17D...bonding state determination unit; 18... laser welded portion, 19... laser irradiated portion, 20... extension portion, 100...semiconductor device, 200...intelligent power module (IPM), 300...Air conditioner, 310...Indoor unit, 320...Outdoor unit, 311, 321...fan motors, 322...compressor. L...Laser.

Claims

1. A circuit board having a metal pattern on its surface, a semiconductor chip mounted on the circuit board, a lead frame including inner leads whose ends are connected to the circuit board, and a mold resin for resin-sealing the semiconductor chip and the lead frame, the semiconductor device comprising: the inner lead and the circuit board are joined by laser welding with the upper surface of the metal pattern and the lower surface of the end portion of the inner lead facing each other, a semiconductor device characterized in that a joint state determination portion made of a material having a melting point lower than that of the inner lead and the material of the metal pattern is provided on the metal pattern.

2. The semiconductor device according to claim 1, wherein the metal pattern includes an extending portion that extends outward from a joint portion between the end portion of the inner lead and the metal pattern in a top view, and the joint state determination portion is provided on the extending portion.

3. The semiconductor device according to claim 1, wherein the joint state determination portion is arranged to protrude outward from the end portion of the inner lead in a top view.

4. The semiconductor device according to claim 1, wherein the joint state determination portion is made of a solder material.

5. An electrical device characterized by including the semiconductor device according to any one of claims 1 to 4.

6. A method for determining a joint state when joining an end portion of an inner lead of a lead frame and a metal pattern provided on a surface of a circuit board on which a semiconductor chip is mounted by laser welding, the method comprising: a step of providing a joint state determination portion made of a material having a melting point lower than that of the inner lead and the material of the metal pattern on the metal pattern of the circuit board; a joint portion alignment step of bringing the upper surface of the metal pattern and the lower surface of the end portion of the inner lead into contact with each other and stacking them; a joining step of irradiating a laser from the upper surface side of the end portion of the inner lead to laser-weld the metal pattern and the inner lead; and a step of determining whether the joint state between the metal pattern and the inner lead is good or bad based on a change in the melting state of the joint state determination portion before and after the joining step.

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