Inductive module, inductor and method of manufacturing an inductor

Abstract

The application discloses an inductor module, an inductor and a manufacturing method thereof. The inductor module comprises at least one coil, the coil having two wire-out ends; a lead frame having a frame body, at least one electrode structure and a plurality of wrapping structures arranged oppositely; at least one magnetic core; the wrapping structure is wrapped outside the wire-out end in the circumferential direction of the wire-out end, and the wire-out end and the wrapping structure are welded to form a welding structure; a part of the wire-out end extends out of the wrapping structure to form a back-melting section for back-melting during welding; the welding structure comprises a welded wrapping part, the back-melting section is welded to form the welded wrapping part, and at least a part of the wrapping structure is wrapped by the welded wrapping part. The application utilizes the wrapping force of the wrapping structure to improve the connection stability between the wrapping structure and the wire-out end, and also improves the welding area between the wrapping structure and the wire-out end, thereby facilitating the improvement of the welding quality, so as to avoid the problem that the connection between the wire-out end of the coil and the lead frame is weak and prone to interruption / open circuit.

Description

Technical Field

[0001] This invention relates to the field of inductor manufacturing technology, and in particular, to an inductor module, an inductor, and a method for manufacturing the same. Background Technology

[0002] In industrial manufacturing, the process of inductor production begins with welding the lead frame and coil together. Next, magnetic powder is die-cast to form the core. Finally, the leads of the lead frame are bent to form the inductor pins. The quality of the connection between the coil and the lead frame is crucial to the quality of the inductor.

[0003] In existing technologies, interruptions / open circuit defects are frequently found due to weak connections between the coil and the lead frame. However, since the connection between the coil and the lead frame is embedded inside the magnetic core after the inductor is formed, the strength of the solder joint cannot be directly tested. When the inductor is soldered to the PCB, the weak connection points between the coil and the lead frame can separate due to thermal expansion and contraction of the materials, leading to interruption defects. However, any testing of connection strength before forming is destructive; therefore, currently, the reliability of the connection can only be determined by manually inspecting the appearance of the connection, which carries the risk of omissions. Summary of the Invention

[0004] The purpose of this invention is to provide an inductor module, an inductor, and a method for manufacturing the same, in order to solve the technical problem of weak connection between the coil and the lead frame in current inductors.

[0005] The above-mentioned objectives of the present invention can be achieved by the following technical solutions:

[0006] This invention provides an inductor module, comprising: at least one coil having two lead ends; a lead frame having a frame body, at least one electrode structure, and a plurality of wrapping structures arranged in pairs opposite each other, the electrode structure including two oppositely arranged electrode portions, one end of the electrode portion being connected to the frame body, and the other end of the electrode portion being connected to the wrapping structure; at least one magnetic core, the magnetic core being formed by powder die casting, and the coil and the wrapping structure being embedded in the magnetic core; wherein, the wrapping structure wraps around the lead ends in the circumferential direction, and the lead ends are welded to the wrapping structure to form a welding structure; a portion of the lead ends extends out of the wrapping structure to form a remelting section for remelting during welding, the welding structure including a welding wrapping portion, the remelting section being formed by welding the welding wrapping portion, and at least a portion of the wrapping structure being wrapped by the welding wrapping portion.

[0007] In an embodiment of the present invention, the wrapping structure includes a wrapping arm, which has a horizontal state and a wrapping state; in the horizontal state, the wrapping arm is arranged horizontally and the lead-out end is placed on the wrapping arm; in the wrapping state, the wrapping arm is bent to form a wrapping frame, the wrapping frame wraps around the lead-out end in the circumferential direction, and a portion of the lead-out end extends out from the wrapping frame to form the remelting section.

[0008] In an embodiment of the present invention, the welding structure includes a reinforcing welding part; wherein, in the wrapped state, the reinforcing welding part is formed by welding between the wire outlet end and the inner wall surface of the wrapping frame.

[0009] In an embodiment of the present invention, the reinforcing weld portion includes an axial weld portion and a circumferential weld portion; wherein, the axial weld portion is formed between the two ends of the wrapping arm and connected to the outlet end by axial welding along the outlet end, and the circumferential weld portion is formed between the wrapping arm and the outlet end by circumferential welding along the outlet end.

[0010] In an embodiment of the present invention, the wrapping arm also has a clamping state. In the clamping state, the two ends of the wrapping arm are bent to form two clamping portions, the wire outlet is clamped between the two clamping portions, and a portion of the wire outlet extends out from between the two clamping portions.

[0011] In an embodiment of the present invention, the welding structure includes an initial welding portion; wherein, in the clamping state, the initial welding portion is formed between the lead-out end and the inner wall surfaces of the two clamping portions by welding.

[0012] In an embodiment of the present invention, the wrapping arm includes a support portion, a first side portion, and a second side portion. The first side portion and the second side portion are connected to both ends of the support portion. The first side portion and the second side portion can be bent to cooperate with the support portion to wrap the cable outlet end.

[0013] In an embodiment of the present invention, the first side portion is bent to form a clamping portion, and the second side portion is bent to form another clamping portion and a pressing portion, wherein the pressing portion presses and fixes the cable outlet end to the support portion.

[0014] In embodiments of the present invention, the welded structure is formed by resistance welding and laser welding.

[0015] The present invention also provides an inductor, which is fabricated from the above-mentioned inductor module into at least one inductor. The inductor includes a coil, a magnetic core and two electrode plates. The two electrode portions of the electrode structure are cut and separated from the frame body to form two electrode plates, and the two electrode plates are bent and attached to the magnetic core.

[0016] The present invention also provides an inductor manufacturing method for manufacturing at least one of the above-mentioned inductors. The inductor manufacturing method includes the following steps: placing two lead-out ends of at least one coil on two opposing wrapping structures on a lead frame, and having the two wrapping structures wrap around the two lead-out ends in the circumferential direction, with a portion of the lead-out ends extending out of the wrapping structures to form a remelted section; wherein the remelted section is welded to form a welded wrapping portion to wrap at least a portion of the wrapping structure; welding the two wrapping structures to the two lead-out ends they wrap; forming at least one magnetic core by powder die casting, and embedding the coil and the corresponding two wrapping structures into the magnetic core; cutting and separating the two electrode portions connected by the two wrapping structures from the frame body of the lead frame, so that the two electrode portions form two electrode sheets; bending and attaching the two electrode sheets to the magnetic core.

[0017] The features and advantages of this invention are:

[0018] The inductor module, inductor, and manufacturing method of the present invention utilize a wrapping structure to wrap around the lead-out end in the circumferential direction and weld it to the lead-out end. This improves the connection stability between the wrapping structure and the lead-out end by utilizing the wrapping force of the wrapping structure, and also increases the welding area between the wrapping structure and the lead-out end, thereby improving the welding quality. Furthermore, by extending a portion of the lead-out end from the wrapping structure to form a remelting section, and then welding it to form a welded wrapping portion, at least a portion of the wrapping structure is wrapped by the welded wrapping portion, thereby further improving the welding area and welding quality between the wrapping structure and the lead-out end. Therefore, the present invention effectively avoids the problem of weak connection between the lead-out end of the coil and the lead frame, which can easily cause interruption / open circuit. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the lead frame in the present invention when the wrapping arm is in a wrapped state.

[0021] Figure 2This is a schematic diagram of the structure in this invention that wraps around the lead-out end of the coil.

[0022] Figure 3 This is a schematic diagram of the structure after the wrapping structure and the outlet end are welded together in this invention.

[0023] Figure 4 This is a schematic diagram of the inductor module in this invention.

[0024] Figure 5 This is a schematic diagram of the lead frame in the present invention when the wrapping arm is in a horizontal state.

[0025] Figure 6 This is a schematic diagram of the wrapping arm in a horizontal state in this invention.

[0026] Figure 7 This is a schematic diagram of the lead frame in the present invention when the wrapping arm is in a clamping state.

[0027] Figure 8 This is a schematic diagram of the wrapping arm in the clamping state of the present invention.

[0028] Figure 9 This is a schematic diagram of the structure after the electrode structure is separated from the main frame in this invention.

[0029] Figure 10 This is a schematic diagram of the inductor structure in this invention.

[0030] Figure 11 This is a perspective view of the inductor in this invention.

[0031] In the picture:

[0032] 1. Lead frame; 11. Frame body; 12. Electrode structure; 121. Electrode part; 13. Wrapping structure; 131. Wrapping arm; 1311. Wrapping frame; 1312. Clamping part; 1313. Support part; 1314. First side part; 1315. Second side part; 1316. Pressing part; 132. Connecting arm;

[0033] 2. Coil; 21. Lead-out terminal; 211. Re-fusion section;

[0034] 3. Magnetic core;

[0035] 4. Electrode plates;

[0036] 5. Welded structure; 51. Welded wrapping part. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Implementation Method 1

[0039] like Figure 1 , Figure 2 as well as Figure 3 As shown, the present invention provides an inductor module, comprising: at least one coil 2, the coil 2 having two lead ends 21; a lead frame 1, having a frame body 11, at least one electrode structure 12, and a plurality of wrapping structures 13 arranged opposite to each other, the electrode structure 12 including two oppositely arranged electrode portions 121, one end of the electrode portion 121 being connected to the frame body 11, and the other end of the electrode portion 121 being connected to the wrapping structure 13; at least one magnetic core 3 ( Figure 7 As shown in the figure, the magnetic core 3 is formed by powder die casting, and the coil 2 and the wrapping structure 13 are embedded in the magnetic core 3; wherein, the wrapping structure 13 wraps around the wire end 21 in the circumferential direction B, and the wire end 21 and the wrapping structure 13 are welded to form a welding structure 5; a part of the wire end 21 extends out of the wrapping structure 13 to form a remelting section 211 for remelting during welding, and the welding structure 5 includes a welding wrapping part 51, the remelting section 211 is formed by welding to form the welding wrapping part 51, and at least a part of the wrapping structure 13 is wrapped by the welding wrapping part 51.

[0040] In this case, the two output terminals 21 of a coil 2 correspond to the two electrode portions 121 of an electrode structure 12 and the two wrapping structures 13 arranged opposite to each other. That is, the number of coils 2 can be set to one, two, three or more, and the number of electrode structures 12 can be set to one, two, three or more, and the number of wrapping structures 13 can be set to two, four, six or more even numbers.

[0041] The inductor module of the present invention, by wrapping the lead-out end 21 circumferentially with the wrapping structure 13 and welding it to the lead-out end 21, can improve the connection stability between the wrapping structure 13 and the lead-out end 21 by utilizing the wrapping force of the wrapping structure 13, and also increases the welding area between the wrapping structure 13 and the lead-out end 21, thereby improving the welding quality. In addition, by extending a part of the lead-out end 21 from the wrapping structure 13 to form a remelting section 211, and then welding to form a welding wrapping part 51, the welding wrapping part 51 wraps at least a part of the wrapping structure 13, thereby further improving the welding area and welding quality between the wrapping structure 13 and the lead-out end 21. Therefore, the present invention can effectively avoid the problem of weak connection between the lead-out end 21 of the coil 2 and the lead frame 1, which is prone to interruption / open circuit.

[0042] Specifically, in combination Figure 2 and Figure 3 As shown, the length of the remelting section 211 is not specifically limited and can be selected as needed. During welding, at least part of the remelting section 211 is heated and melted, then solidifies with the solder to form a welded wrapping portion 51. The welded wrapping portion 51 is generally cap-shaped and welded onto the wrapping structure 13. The coil 2 can be made of copper wire. (Combined) Figure 4 As shown, after the two lead ends 21 of coil 2 are connected to the wrapping structure 13, they can be placed in the molding die of magnetic core 3. Powder is then placed in the molding die for die casting, thus forming magnetic core 3. Part of the two electrode portions 121 of electrode structure 12 is embedded in magnetic core 3, while the other part is located outside magnetic core 3. Combined with... Figure 4 and Figures 9 to 11 As shown, the inductor module can be further processed to obtain at least one inductor. Specifically, the two electrode portions 121 of the electrode structure 12, after being cut and separated from the frame body 11, form the two electrode plates 4 of the inductor. The portions of the two electrode plates 4 located outside the magnetic core 3 are bent to fit against the magnetic core 3, thereby obtaining the inductor. The two electrode plates 4 can be soldered and fixed to the circuit board, thus achieving electrical connection between the inductor and the circuit board.

[0043] like Figure 3 As shown, in an embodiment of the present invention, the welded structure 5 is formed by resistance welding and laser welding. This double welding method effectively avoids false welds. Specifically, the lead end 21 can be first welded to the wrapping structure 13 along a welding path using resistance welding, and then the lead end 21 can be welded to the wrapping structure 13 along the same welding path using laser welding to form the welded structure 5; or the lead end 21 can be first welded to the wrapping structure 13 along a welding path using laser welding, and then the lead end 21 can be welded to the wrapping structure 13 along the same welding path using resistance welding to form the welded structure 5.

[0044] like Figure 1 and Figure 2 As shown, the wrapping structure 13 includes a wrapping arm 131, which wraps around the lead-out end 21. Specifically, the wrapping arm 131 is generally a frame-shaped wrapping frame 1311. Preferably, the two ends of the wrapping arm 131 are butted together or overlapped, and the wrapping angle of the wrapping arm 131 around the lead-out end 21 in the circumferential direction B is 360 degrees. Optionally, the wrapping angle of the wrapping arm 131 around the lead-out end 21 in the circumferential direction B is less than 360 degrees, and there is a notch between the two ends of the wrapping arm 131. The width of this notch is smaller than the diameter of the lead-out end 21, thereby preventing the lead-out end 21 from coming out of the notch. Furthermore, the wrapping structure 13 also includes a connecting arm 132, one end of which is connected to the wrapping arm 131, and the other end of which is connected to the electrode portion 121.

[0045] In some embodiments of the present invention, the wrapping arm 131 has a horizontal state and a wrapping state; such as Figure 5 and Figure 6 As shown, in a horizontal position, the wrapping arm 131 is arranged horizontally, and the cable outlet 21 is placed on the wrapping arm 131; as Figure 1 and Figure 2 As shown, in the wrapped state, the wrapping arm 131 is bent to form a wrapping frame 1311. The wrapping frame 1311 wraps around the exit end 21 in the circumferential direction B, and a part of the exit end 21 extends out from the wrapping frame 1311 to form a remelting section 211. By first arranging the wrapping arm 131 horizontally and then bending it to wrap, assembly is more convenient, and the wrapping arm 131 can adaptively wrap according to the cross-sectional shape of the exit end 21, thereby wrapping the exit end 21 more tightly.

[0046] like Figure 1 and Figure 2 As shown, in some other embodiments of the present invention, the wrapping arm 131 can be directly bent to form a wrapping frame 1311, and then the lead end 21 of the coil 2 is inserted into the wrapping frame 1311, thereby realizing the assembly of the lead end 21 and the wrapping arm 131.

[0047] Combination Figure 2 As shown, in order to further improve the welding area and welding quality between the wrapping structure 13 and the outlet end 21, in the embodiment of the present invention, the welding structure 5 further includes a reinforcing welding part; wherein, in the wrapped state, the outlet end 21 and the inner wall surface of the wrapping frame 1311 are welded to form a reinforcing welding part, that is, after the outlet end 21 and the wrapping arm 131 are assembled, that is, after the outlet end 21 is wrapped by the wrapping arm 131, a reinforcing welding part can be formed by welding to weld the outlet end 21 to the inner wall surface of the wrapping frame 1311.

[0048] Specifically, such as Figure 2As shown, the reinforcing weld includes an axial weld and a circumferential weld. The axial weld is formed between the two ends of the wrapping arm 131 by welding along the axial direction A of the outlet end 21 and is in contact with the outlet end 21. The circumferential weld is formed between the wrapping arm 131 and the outlet end 21 by welding along the circumferential direction B of the outlet end 21. By welding the wrapping arm 131 and the outlet end 21 together along the axial direction A and the circumferential direction B of the outlet end 21, the reliability of the weld is improved.

[0049] like Figure 7 and Figure 8 As shown, in an embodiment of the present invention, the wrapping arm 131 also has a clamping state. In the clamping state, the two ends of the wrapping arm 131 are bent to form two clamping portions 1312, and the wire outlet end 21 is clamped between the two clamping portions 1312, with a portion of the wire outlet end 21 extending out from between the two clamping portions 1312. Before the wrapping arm 131 forms the wrapping state, the wire outlet end 21 is clamped by first bending the two ends of the wrapping arm 131 to form two clamping portions 1312. This facilitates the subsequent bending of the wrapping arm 131 to wrap the wire outlet end 21, and also further improves the wrapping force between the wrapping arm 131 and the wire outlet end 21, thereby improving the connection quality between the wrapping arm 131 and the wire outlet end 21. In addition, the welding structure 5 includes an initial welding portion; wherein, in the clamping state, an initial welding portion is formed between the wire outlet end 21 and the inner wall surface of the two clamping portions 1312 by welding. By first welding an initial welded section to connect the wrapping arm 131 to the outlet end 21 while in a clamped state, and then welding a reinforcing welded section to connect the wrapping arm 131 to the outlet end 21 while in a wrapped state, the connection quality between the wrapping arm 131 and the outlet end 21 is further improved. Finally, the remelting section 211 extending from the outlet end 21 is welded to form a welded wrapping section 51 and welded onto the wrapping frame 1311 to ensure reliable welding quality.

[0050] Specifically, in combination Figure 2 , Figure 6 as well as Figure 8As shown, the wrapping arm 131 includes a support portion 1313, a first side portion 1314, and a second side portion 1315. The first side portion 1314 and the second side portion 1315 are connected to both ends of the support portion 1313. The first side portion 1314 and the second side portion 1315 are bent to cooperate with the support portion 1313 to wrap the cable outlet 21. The first side portion 1314 is bent to form a clamping portion 1312, and the second side portion 1315 is bent to form another clamping portion 1312 and a pressing portion 1316. The pressing portion 1316 presses and fixes the cable outlet 21 to the support portion 1313. The length of the second side portion 1315 is greater than the length of the first side portion 1314. The first side portion 1314 only needs to be bent once to form a clamping portion 1312, while the second side portion 1315 needs to be bent once to form another clamping portion 1312, and then bent once to form a pressing portion 1316.

[0051] Implementation Method 2

[0052] like Figure 7 As shown, the present invention also provides an inductor, which is fabricated from an inductor module to form at least one inductor. The inductor includes a coil 2, a magnetic core 3, and two electrode plates 4. The two electrode portions 121 of the electrode structure 12 are cut and separated from the frame body 11 to form the two electrode plates 4, and the two electrode plates 4 are bent and attached to the magnetic core 3. The inductor module in this embodiment has the same specific structure, working principle, and beneficial effects as the inductor module in Embodiment 1, and will not be described again here.

[0053] Implementation Method 3

[0054] Combination Figure 1 , Figure 2 and Figure 7 As shown, the present invention also provides an inductor manufacturing method for manufacturing at least one inductor, the inductor manufacturing method comprising the following steps:

[0055] At least one coil 2 has two lead ends 21 placed on two wrapping structures 13 arranged opposite to each other on the lead frame 1, and the two wrapping structures 13 wrap the two lead ends 21 in the circumferential direction B of the lead ends 21, and a part of the lead ends 21 extends out of the wrapping structure 13 to form a remelting section 211.

[0056] The two wrapping structures 13 are welded together with the two outgoing ends 21 of their wrappings; wherein, the remelting section 211 forms a welded wrapping part 51 by welding, thereby wrapping at least a portion of the wrapping structure 13.

[0057] At least one magnetic core 3 is formed by powder die casting, and the coil 2 and the corresponding two wrapping structures 13 are embedded in the magnetic core 3 to obtain an inductor module; wherein the inductor module is the same as the inductor module in Embodiment 1 in terms of specific structure, working principle and beneficial effects, and will not be described in detail here.

[0058] The two electrode portions 121 connected by the two wrapping structures 13 are cut and separated from the frame body 11 of the lead frame 1, so that the two electrode portions 121 form two electrode sheets 4.

[0059] At least one inductor is made by bending and attaching two electrode sheets 4 to the magnetic core 3; wherein the inductor has the same specific structure, working principle and beneficial effects as the inductor in Embodiment 2, and will not be described again here.

[0060] The above descriptions are merely a few embodiments of the present invention. Those skilled in the art can make various modifications or variations to the embodiments of the present invention based on the content disclosed in the application documents without departing from the spirit and scope of the present invention.

Claims

1. An inductor module, characterized in that, include: At least one coil, the coil having two output terminals; A lead frame has a frame body, at least one electrode structure, and multiple wrapping structures arranged in pairs opposite each other. The electrode structure includes two electrode portions arranged opposite each other. One end of the electrode portion is connected to the frame body, and the other end of the electrode portion is connected to the wrapping structure. At least one magnetic core, the magnetic core being formed by powder die casting, and the coil and the encapsulation structure being embedded within the magnetic core; Wherein, the wrapping structure wraps around the wire outlet in the circumferential direction, and the wire outlet is welded to the wrapping structure to form a welded structure; A portion of the outlet end extends out of the wrapping structure to form a remelting section for remelting during welding. The welding structure includes a welding wrapping portion, and the remelting section is formed by welding the welding wrapping portion. At least a portion of the wrapping structure is wrapped by the welding wrapping portion.

2. The inductor module as described in claim 1, characterized in that, The wrapping structure includes a wrapping arm, which has a horizontal state and a wrapping state. In the horizontal state, the wrapping arm is arranged horizontally, and the cable outlet is placed on the wrapping arm; In the packaged state, the package arm is bent to form a package frame, the package frame wraps around the exit end in the circumferential direction, and a part of the exit end extends out from the package frame to form the remelting section.

3. The inductor module as described in claim 2, characterized in that, The welded structure also includes a reinforced weld section; In the packaged state, the lead-out end and the inner wall of the package frame are welded together to form the reinforced welded part.

4. The inductor module as described in claim 3, characterized in that, The reinforced welded part includes an axial welded part and a circumferential welded part; The axial weld portion is formed between the two ends of the wrapping arm and connected to the outlet end by axial welding along the outlet end, and the circumferential weld portion is formed between the wrapping arm and the outlet end by circumferential welding along the outlet end.

5. The inductor module as described in claim 2, characterized in that, The wrapping arm also has a clamping state. In the clamping state, the two ends of the wrapping arm are bent to form two clamping parts. The wire outlet is clamped between the two clamping parts, and a part of the wire outlet extends out from between the two clamping parts.

6. The inductor module as described in claim 5, characterized in that, The welded structure includes an initial weld section; In the clamping state, the lead-out end and the inner wall surfaces of the two clamping parts are welded together to form the initial welded part.

7. The inductor module as described in claim 5, characterized in that, The wrapping arm includes a support portion, a first side portion, and a second side portion. The first side portion and the second side portion are connected to both ends of the support portion. The first side portion and the second side portion can be bent to cooperate with the support portion to wrap the cable outlet end.

8. The inductor module as described in claim 7, characterized in that, The first side portion is bent to form a clamping portion, and the second side portion is bent to form another clamping portion and a pressing portion. The pressing portion presses and fixes the cable outlet end to the support portion.

9. The inductor module as described in any one of claims 1-8, characterized in that, The welded structure is formed by resistance welding and laser welding.

10. An inductor, characterized in that, At least one inductor is fabricated using the inductor module according to any one of claims 1-9. The inductor includes a coil, a magnetic core, and two electrode plates. The two electrode portions of the electrode structure are cut and separated from the frame body to form two electrode plates, and the two electrode plates are bent and attached to the magnetic core.

11. A method for manufacturing an inductor, characterized in that, The method for manufacturing at least one inductor as described in claim 10 includes the following steps: At least one coil has two lead ends placed on two wrapping structures arranged opposite each other on a lead frame, and the two wrapping structures wrap the two lead ends in the circumferential direction of the lead ends, with a portion of the lead ends extending out of the wrapping structures to form a remelting section. The two wrapping structures are welded together with the two outlet ends of the wrapping structure; wherein the remelting section forms a welded wrapping part by welding to wrap at least a portion of the wrapping structure; At least one magnetic core is formed by powder die casting, and the coil and the corresponding two encapsulation structures are embedded in the magnetic core. The two electrode portions connected by the two aforementioned wrapping structures are cut and separated from the frame body of the lead frame, so that the two electrode portions form two electrode sheets; The two electrode sheets are bent and attached to the magnetic core.

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