Protection circuit unit and method for joining lead unit and protection circuit unit

Abstract

An embodiment of the present invention is a protection circuit unit provided with a printed circuit board connected to a positive electrode lead portion and a negative electrode lead portion that are connected to a battery cell, and the printed circuit board may include an upper layer joined to the positive electrode lead portion and the negative electrode lead portion so as to be electrically connected, and an intermediate layer including a first insulating layer formed from a material containing epoxy resin, the intermediate layer being provided below the upper layer, and a laser reflective layer being provided between the upper layer and the first insulating layer, the laser reflective layer reflecting a laser. According to the embodiment of the present invention, it is possible to suppress or prevent the laser irradiated for bonding the lead portion and the protection circuit portion from being incident on the intermediate layer of the protection circuit portion, thereby preventing the intermediate layer of the protection circuit portion from being damaged by the laser, and thereby preventing damage to the protection circuit portion by the laser.

Description

[Technical field]

[0001] The present invention relates to a protection circuit unit and a method for joining a lead part and a protection circuit unit, and more particularly to a protection circuit unit and a method for joining a lead part and a protection circuit unit that can prevent damage to the protection circuit unit by a laser when a laser is used to connect a battery cell and a protection circuit unit. [Background technology]

[0002] A protection circuit module (PCM) is connected to the battery cell to prevent overcharging, over-discharging, and overcurrent. The protection circuit module continuously detects the voltage, current, temperature, etc. of the battery cell, and uses the detected values ​​to determine the state (status) of the battery cell. If overcharging, over-discharging, over-current, etc. is detected and the battery cell is determined to be in an abnormal state, the protection circuit module controls the operation of the battery cell. That is, the protection circuit module stops charging or discharging the battery cell, or cuts off the electric circuit.

[0003] A laser bonding method is used to connect such a protection circuit module to a battery cell. That is, the protection circuit module is placed under the positive and negative lead parts connected to the battery cell, and then a laser is irradiated from above. Then, the positive and negative lead parts are welded and bonded to the top of the protection circuit module by the heat of the laser.

[0004] Meanwhile, the protection circuit module includes a copper foil connected or joined to the positive and negative electrode lead parts, a plurality of prepreg layers and a plurality of copper layers laminated under the copper foil, where the prepreg layers and the copper layers are alternately laminated.

[0005] However, the prepreg layer has a high transmittance to lasers. Therefore, when a laser is applied for bonding, the laser passes through the prepreg layer located under the copper foil and then enters the other layers laminated below it. As a result, the prepreg layer located under the copper foil and the layers located below it are damaged by the laser, which causes a problem in that the protection circuit module is damaged. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Republic of Korea Publication Patent No. 10-2016-0094623 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention provides a protection circuit unit and a method for bonding a lead unit and the protection circuit unit, which can prevent a laser irradiated from above from penetrating to the underside of an insulating layer. [Means for solving the problem]

[0008] An embodiment of the present invention may be a protection circuit unit provided with a printed circuit board connected to a positive electrode lead portion and a negative electrode lead portion that are connected to a battery cell, the printed circuit board including an upper layer joined to the positive electrode lead portion and the negative electrode lead portion so as to be electrically connected, an intermediate layer including a first insulating layer formed from a material containing epoxy resin, the intermediate layer being provided below the upper layer, and a laser reflective layer provided between the upper layer and the first insulating layer, the laser reflective layer reflecting a laser.

[0009] The laser reflective layer may have a reflectance of 95% or more to a laser having a wavelength of 1000 nm to 1100 nm.

[0010] The laser reflective layer may have a reflectance of 95% or more to a laser having a wavelength of 1060 nm to 1080 nm.

[0011] The laser reflective layer may be formed from silver (Ag).

[0012] The laser reflective layer may have a smaller thickness than the upper layer and the intermediate layer.

[0013] The top layer may be formed from copper (Cu) and the first insulating layer may be formed from a material including the epoxy resin and fiberglass.

[0014] The intermediate layer may include a second insulating layer and a third insulating layer provided below the first insulating layer, a first metal layer provided between the first insulating layer and the second insulating layer, and a second metal layer provided between the second insulating layer and the third insulating layer.

[0015] The second insulating layer and the third insulating layer may be formed from a material including epoxy resin and glass fiber, and the first metal layer and the second metal layer may be formed from copper (Cu).

[0016] A method for joining a lead portion and a protection circuit portion according to an embodiment of the present invention may include the steps of providing a printed circuit board having a laser reflective layer with a reflectance of 95% or more for lasers with wavelengths of 1000 nm to 1100 nm, mounting a protection circuit element on the printed circuit board to provide a protection circuit portion, positioning the protection circuit portion below a lead portion connected to an electrode of a battery cell, and irradiating a laser from above the lead portion to join the lead portion and the printed circuit board.

[0017] The step of providing the printed circuit board may include the steps of providing a top layer using copper (Cu), providing a first insulating layer using a material including an epoxy resin, and providing the laser reflective layer between the top layer and the first insulating layer.

[0018] The step of providing the printed circuit board may include the steps of providing a second insulating layer and a third insulating layer below the first insulating layer, providing a first metal layer between the first insulating layer and the second insulating layer, and providing a second metal layer between the second insulating layer and the third insulating layer, wherein the first insulating layer, the second insulating layer, and the third insulating layer are formed from a material including epoxy resin and glass fiber, and the first metal layer and the second metal layer are formed from copper (Cu).

[0019] The laser reflective layer may be formed using silver (Ag). Effect of the Invention

[0020] According to the embodiment of the present invention, it is possible to suppress or prevent the laser irradiated for bonding the lead portion and the protection circuit portion from being incident on the intermediate layer of the protection circuit portion, thereby preventing the intermediate layer of the protection circuit portion from being damaged by the laser, and thereby preventing damage to the protection circuit portion by the laser. [Brief description of the drawings]

[0021] [Figure 1] 1 is a diagram showing a battery pack including a protection circuit unit according to an embodiment of the present invention; [Diagram 2] 13 is a diagram conceptually showing a state in which a laser is irradiated from above a lead portion in order to connect the lead portion to a printed circuit board of a protection circuit portion. FIG. [Diagram 3] 1A and 1B are diagrams showing a configuration of a printed circuit board according to an embodiment of the present invention and a state in which a laser is irradiated from above a lead portion in order to connect the printed circuit board to the lead portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, the embodiments of the present invention will be described in more detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be embodied in various different forms. These embodiments are merely provided to complete the disclosure of the present invention and to fully inform those skilled in the art of the scope of the invention. In order to describe the embodiments of the present invention, the drawings may be exaggerated, and the same reference numerals in the drawings refer to the same components.

[0023] Fig. 1 is a diagram showing a battery pack including a protection circuit unit according to an embodiment of the present invention. Fig. 2 is a diagram conceptually showing a state in which a laser is irradiated from above a lead part in order to connect the lead part to a printed circuit board of the protection circuit unit. Fig. 3 is a diagram showing the configuration of a printed circuit board according to an embodiment of the present invention and a state in which a laser is irradiated from above the lead part in order to connect the printed circuit board to the lead part.

[0024] Here, FIG. 2 and FIG. 3 are diagrams showing a state in which a laser is irradiated from above the lead portion in order to connect the positive electrode lead portion of the lead portion to a printed circuit board.

[0025] Referring to FIG. 1, a battery pack 1000 according to an embodiment of the present invention includes a case 1100 having an internal space, a battery cell 1200 accommodated inside the case 1100 and configured to charge and discharge electricity, a lead portion 1300 having a positive electrode lead portion 1300a and a negative electrode lead portion 1300b connected to the battery cell 1200, and a protection circuit portion 1400 connected to the positive and negative electrode lead portions 1300a, 1300b.

[0026] The case 1100 has an internal space capable of housing the battery cell 1200, the positive and negative electrode lead parts 1300a, 1300b, and the protection circuit part 1400. The shape of the case 1100 is not particularly limited, and the case 1100 may have any shape as long as it has an internal space capable of housing the battery cell 1200, the positive and negative electrode lead parts 1300a, 1300b, and the protection circuit part 1400.

[0027] The battery cell 1200 is a means for charging and discharging current and may be a secondary battery. Such a battery cell may be a means including a positive electrode, a negative electrode, an electrolyte, and a separator sandwiched between the positive and negative electrodes.

[0028] The lead portion 1300 is a means for electrically connecting the battery cell 1200 and the protection circuit portion 1400, and includes a positive electrode lead portion 1300a and a negative electrode lead portion 1300b. The positive electrode lead portion 1300a electrically connects the positive electrode of the battery cell 1200 and the protection circuit portion 1400, and the negative electrode lead portion 1300b electrically connects the negative electrode of the battery cell 1200 and the protection circuit portion. Such positive and negative electrode lead portions 1300a, 1300b may be made of, for example, nickel (Ni).

[0029] The protection circuit unit 1400 is a means generally called a protection circuit module (PCM). The protection circuit unit 1400 continuously detects the voltage, current, temperature, etc. of the battery cell 1200, and judges the state of the battery cell 1200 using the detected values. If the protection circuit unit 1400 detects overcharge, overdischarge, overcurrent, etc. and judges that the battery cell 1200 is in an abnormal state, the protection circuit unit 1400 controls the operation of the battery cell 1200. For example, the protection circuit unit 1400 stops charging or discharging the battery cell 1200 or cuts off the electric path. The operation of the protection circuit unit 1400 can prevent the battery cell 1200 from overheating or deteriorating due to overcharge or overdischarge, and can prevent the occurrence of a fire.

[0030] As shown in FIG. 1, the protection circuit unit 1400 includes a printed circuit board (PCB) 1410 connected to the positive and negative lead portions 1300a, 1300b, and at least one protection circuit element 1420 mounted on the printed circuit board 1410.

[0031] The protection circuit element 1420 may be a passive or active element having a protection circuit, and may be mounted on the upper or lower part of the printed circuit board 1410. Note that a plurality of protection circuit elements 1420 may be provided. Such protection circuit elements 1420 are provided to play a role in protecting the battery pack from the risk of fire or explosion due to heat generation caused by overcharging, overdischarging, overcurrent, etc.

[0032] The printed circuit board 1410 is electrically connected to the positive and negative electrode lead parts 1300a, 1300b, and is connected by a welding method using a laser. This will be described in more detail with reference to FIG. 2. After the positive and negative electrode lead parts 1300a, 1300b are arranged on the upper part of the printed circuit board 1410, a laser L is irradiated from above the positive and negative electrode lead parts 1300a, 1300b. At this time, a laser having a wavelength of 1000 nm to 1100 nm, more specifically, 1060 nm to 1080 nm, and even more specifically, 1070 nm, is used as the laser L. The positive and negative electrode lead parts 1300a, 1300b are welded, that is, joined, to the upper part of the printed circuit board 1410 by the thermal energy of the laser L irradiated here.

[0033] Hereinafter, the printed circuit board 1410 of the protection circuit unit 1400 according to an embodiment of the present invention will be described with reference to Fig. 3. At this time, the positive electrode lead part 1300a and the negative electrode lead part 1300b connected to the printed circuit board 1410 will be collectively referred to as the lead part 1300 for ease of description.

[0034] As shown in FIG. 3, a printed circuit board 1410 according to an embodiment of the present invention comprises an upper layer 1411 and a lower layer 1413, each made of metal and arranged vertically apart, an intermediate layer 1412 provided between the upper layer 1411 and the lower layer 1413 and comprising a light-transmitting insulating layer, and a laser reflective layer 1414 located between the upper layer 1411 and the intermediate layer 1412 and reflecting light.

[0035] The upper layer 1411 may be a layer that is electrically connected, i.e., joined, to the lead portion 1300 (1300a, 1300b) and forms a circuit. Such an upper layer 1411 is formed of a metal having conductivity so as to be electrically connected to the lead portion 1300. For example, the upper layer 1411 may be made of copper (Cu), and therefore the upper layer 1411 made of copper (Cu) can be named a copper foil layer. In addition, a protection circuit element 1420 may be mounted on the upper layer 1411, and therefore the protection circuit element 1420 can be electrically connected to the circuit, i.e., the battery cell 1200 via the upper layer 1411 and the lead portion 1300. The thickness of the upper layer 1411 may be set to 0.6 mm or more, more specifically, to 0.6 mm or more and 0.8 mm or less.

[0036] On the other hand, if the thickness of upper layer 1411 is less than 0.6 mm, the conductivity of upper layer 1411 is low, which may result in an unstable electrical connection with lead portion 1300. The reason for making the thickness of upper layer 1411 0.8 mm or less is that sufficient conductivity can be ensured even with a thickness of 0.8 mm or less, so there is no need to make it thicker than 0.8 mm.

[0037] The lower layer 1413 is a layer provided below the intermediate layer 1412, and may be provided in the same manner as the above-mentioned upper layer 1411, or may be a layer that constitutes a circuit. That is, the lower layer 1413 may be a copper foil layer made of copper (Cu), and may be provided with a thickness of 0.6 mm or more, more specifically, a thickness of 0.6 mm or more and 0.8 mm or less.

[0038] The intermediate layer 1412 includes a plurality of insulating layers and at least one metal layer. The insulating layers and the metal layers are arranged alternately or staggered. At this time, the insulating layers are arranged at the top and bottom, and the metal layer is arranged between them. The insulating layer is formed from a material containing an epoxy resin. Therefore, the insulating layer has a characteristic that light, that is, the laser L that bonds the lead portion 1300 and the printed circuit board 1410, is transmitted through the insulating layer. More specifically, the laser L having a wavelength that bonds the lead portion 1300 and the printed circuit board 1410 can transmit through the insulating layer. That is, the insulating layer can transmit a laser of 1000 nm to 1100 nm, more specifically, a laser of 1060 nm to 1080 nm, and even more specifically, a laser of 1070 nm.

[0039] The intermediate layer 1412 will be described in more detail below. Referring to Fig. 3, the intermediate layer 1412 includes a first insulating layer 1412a-1, which is the top layer, a first metal layer 1412b-1, a second insulating layer 1412a-2, a second metal layer 1412b-2, and a third insulating layer 1412a-3, which are stacked in this order from the first insulating layer 1412a-1 to the top of the lower layer 1413. Therefore, the first metal layer 1412b-1 is located between the first insulating layer 1412a-1 and the second insulating layer 1412a-2, and the second metal layer 1412b-2 is provided between the second insulating layer 1412a-2 and the third insulating layer 1412a-3.

[0040] The first and third insulating layers 1412a-1 and 1412a-3 may be prepregs made of fiber reinforced material impregnated with epoxy resin. In this case, the fiber reinforced material may be, for example, glass fiber. The second insulating layer 1412a-2 may be a material made of multiple layers of glass fiber impregnated with epoxy resin, that is, FR-4 (Flame retardant-4, a heat-resistant glass cloth-based epoxy resin copper-clad laminate).

[0041] The first and second metal layers 1412b-1 and 1412b-2 may be made of copper (Cu), and may have a thickness of 0.3 mm to 0.4 mm.

[0042] On the other hand, the first to third insulating layers 1412a-1, 1412a-2, 1412a-3 are made of a material containing epoxy resin and glass fiber as described above, and such a material has high transmittance for the laser L. That is, the transmittance is high for the wavelength band of 1000 nm to 1100 nm of the laser L irradiated for joining the lead portion 1300 and the printed circuit board 1410.

[0043] Therefore, when a laser of 1000 nm to 1100 nm is irradiated from the upper side of the lead portion 1300 for bonding, the laser L that has passed through the upper layer 1411 can pass through the first insulating layer 1412a-1 and then pass through the lower side thereof. In such a case, the first insulating layer 1412a-1 and the multiple layers laminated thereunder, that is, the first metal layer 1412b-1, the second insulating layer 1412a-2, the second metal layer 1412b-2, and the third insulating layer 1412a-3, may be damaged, which may damage the printed circuit board 1410.

[0044] Therefore, it is necessary to prevent the laser L irradiated to the printed circuit board 1410 from entering the intermediate layer 1412. That is, it is necessary to prevent the laser L from entering the lower side of the first insulating layer 1412a-1. In other words, it is necessary to prevent the laser L from entering or penetrating the inside of the first insulating layer 1412a-1. More specifically, it is necessary to prevent the laser L from penetrating the lower side of the upper surface of the first insulating layer 1412a-1.

[0045] Therefore, in the embodiment of the present invention, a laser reflecting layer 1414 capable of reflecting the laser beam L is provided between the upper layer 1411 and the intermediate layer 1412. That is, a laser reflecting layer 1414 that reflects the laser beam L is provided between the upper layer 1411 and the first insulating layer 1412a-1.

[0046] The laser reflective layer 1414 may be provided so as to have a reflectance of 95% or more for the laser L irradiated for bonding the lead portion 1300 and the printed circuit board 1410. In other words, the laser reflective layer 1414 is provided so as to have a reflectance of 95% or more for the laser L having a wavelength of 1000 nm to 1100 nm.

[0047] Such a laser reflecting layer 1414h is formed of a material containing a metal, and may be formed of silver (Ag). The laser reflecting layer 1414 may have any thickness as long as the reflectance is 95% or more. In this case, the thickness of the laser reflecting layer 1414 is preferably thinner than the upper layer 1411, the lower layer 1413, and the intermediate layer 1412.

[0048] A method for joining a lead portion to a protection circuit portion according to an embodiment of the present invention will be described below with reference to FIGS.

[0049] First, a protection circuit unit 1400 including a printed circuit board 1410 according to an embodiment of the present invention is provided. That is, the protection circuit unit 1400 includes the printed circuit board 1410 including an upper layer 1411, an intermediate layer 1412, and a lower layer 1413, and a laser reflecting layer 1414 having a laser reflectance of 95% or more is provided between the upper layer 1411 and the intermediate layer 1412, and a protection circuit element 1420 mounted on the printed circuit board 1410.

[0050] As shown in FIGS. 1 to 3, the protection circuit unit 1400 is located below the lead units 1300 connected to the positive and negative electrodes of the battery cell 1200, that is, the positive and negative lead units 1300a and 1300b.

[0051] 2 and 3, a laser L is applied from above the positive electrode and negative electrode lead portions 1300a and 1300b. At this time, the laser L has a wavelength of 1000 nm to 1100 nm, more specifically, a wavelength of 1060 nm to 1080 nm. As a more specific example, the laser L is applied at 1070 nm.

[0052] For this reason, the laser L is irradiated onto the lead portion 1300 and the printed circuit board 1410 of the protection circuit portion 1400, and at least a portion of each of the lead portion 1300 and the printed circuit board 1410 is melted and bonded to each other by the heat of the laser L. That is, at least a portion of the upper layer 1411 of the printed circuit board 1410 and the lead portion 1300 are melted and bonded to each other.

[0053] At this time, the laser L irradiated toward the lead portion 1300 and the printed circuit board 1410 may pass through the lead portion 1300 and the upper layer 1411 of the printed circuit board 1410. That is, the laser L may be incident on the inside of the lead portion 1300 and the upper layer 1411. However, the laser L that passes through the upper layer 1411 is reflected by the laser reflecting layer 1414 located thereunder, as shown in FIG. 3. Therefore, the laser L does not pass through the first insulating layer 1412a-1 located under the laser reflecting layer 1414, and therefore does not enter the lower side of the first insulating layer 1412a-1.

[0054] More specifically, 95% or more of the laser L that has passed through the upper layer 1411 is reflected by the laser reflecting layer 1414 and travels again to the upper side of the upper layer 1411. Therefore, of the laser L that has passed through the upper layer 1411, an extremely small amount of the laser L, less than 5%, can pass through the laser reflecting layer 1414 and then enter the first insulating layer 1412a-1.

[0055] In this manner, in the embodiment of the present invention, it is possible to suppress or prevent the laser L irradiated for bonding from being incident on the intermediate layer 1412. In other words, it is possible to suppress or prevent the laser L from being incident on or passing through the first insulating layer 1412a-1. Therefore, it is possible to prevent the intermediate layer 1412 provided below the upper layer 1411 from being damaged by the laser L, and thus it is possible to prevent damage to the printed circuit board 1410 or the protection circuit unit 1400 by the laser L. [Industrial Applicability]

[0056] According to the embodiment of the present invention, it is possible to suppress or prevent the laser irradiated for bonding the lead portion and the protection circuit portion from being incident on the intermediate layer of the protection circuit portion, thereby preventing the intermediate layer of the protection circuit portion from being damaged by the laser, and thereby preventing damage to the protection circuit portion by the laser.

Claims

1. A protection circuit unit including a printed circuit board connected to a positive electrode lead portion and a negative electrode lead portion connected to the battery cell, The printed circuit board comprises: an upper layer joined to the positive electrode lead portion and the negative electrode lead portion so as to be electrically connected; an intermediate layer comprising a first insulating layer formed from a material including an epoxy resin, the intermediate layer being disposed below the upper layer; a laser reflective layer provided between the upper layer and the first insulating layer, the laser reflective layer reflecting a laser; Equipped with The protective circuit portion, wherein the laser reflective layer has a reflectance of 95% or more for a laser having a wavelength of 1000 nm to 1100 nm.

2. A protection circuit unit including a printed circuit board connected to a positive electrode lead portion and a negative electrode lead portion connected to the battery cell, The printed circuit board comprises: an upper layer joined to the positive electrode lead portion and the negative electrode lead portion so as to be electrically connected; an intermediate layer comprising a first insulating layer formed from a material including an epoxy resin, the intermediate layer being disposed below the upper layer; a laser reflective layer provided between the upper layer and the first insulating layer, the laser reflective layer reflecting a laser; Equipped with The protective circuit portion, wherein the laser reflective layer has a reflectance of 95% or more for a laser having a wavelength of 1060 nm to 1080 nm.

3. A protection circuit unit including a printed circuit board connected to a positive electrode lead portion and a negative electrode lead portion connected to the battery cell, The printed circuit board comprises: an upper layer joined to the positive electrode lead portion and the negative electrode lead portion so as to be electrically connected; an intermediate layer comprising a first insulating layer formed from a material including an epoxy resin, the intermediate layer being disposed below the upper layer; a laser reflective layer provided between the upper layer and the first insulating layer, the laser reflective layer reflecting a laser; Equipped with The laser reflective layer is a protection circuit portion formed from silver (Ag).

4. 4. The protection circuit section according to claim 1, wherein the laser reflective layer is thinner than the upper layer and the intermediate layer.

5. the top layer is formed from copper (Cu); 5. The protection circuit section according to claim 1, wherein the first insulating layer is made of a material containing the epoxy resin and glass fiber.

6. The intermediate layer is a second insulating layer and a third insulating layer provided below the first insulating layer; a first metal layer provided between the first insulating layer and the second insulating layer; a second metal layer provided between the second insulating layer and the third insulating layer; The protection circuit unit according to any one of claims 1 to 5, comprising:

7. the second insulating layer and the third insulating layer are formed from a material including an epoxy resin and a glass fiber; The protection circuit portion of claim 6 , wherein the first metal layer and the second metal layer are formed from copper (Cu).

8. Providing a printed circuit board having a laser reflective layer with a reflectance of 95% or more for a laser having a wavelength of 1000 nm to 1100 nm; providing a protection circuit section by mounting a protection circuit element on the printed circuit board; Positioning the protection circuit unit below a lead portion connected to an electrode of a battery cell; irradiating a laser from above the lead portion to bond the lead portion to the printed circuit board; The method for joining a lead portion and a protection circuit portion includes the steps of:

9. A step of providing a printed circuit board having a laser reflective layer having a reflectance of 95% or more for a laser having a wavelength of 1060 nm to 1080 nm; providing a protection circuit section by mounting a protection circuit element on the printed circuit board; Positioning the protection circuit unit below a lead portion connected to an electrode of a battery cell; irradiating a laser from above the lead portion to bond the lead portion to the printed circuit board; The method for joining a lead portion and a protection circuit portion includes the steps of:

10. The method of claim 1, further comprising the steps of: providing a printed circuit board having a laser reflective layer formed from silver (Ag); providing a protection circuit section by mounting a protection circuit element on the printed circuit board; Positioning the protection circuit unit below a lead portion connected to an electrode of a battery cell; irradiating a laser from above the lead portion to bond the lead portion to the printed circuit board; The method for joining a lead portion and a protection circuit portion includes the steps of:

11. The step of providing a printed circuit board includes: providing a top layer using copper (Cu); providing a first insulating layer using a material including an epoxy resin; providing the laser reflective layer between the top layer and the first insulating layer; The method for joining the lead portion and the protection circuit portion according to any one of claims 8 to 10, comprising:

12. The step of providing a printed circuit board includes: providing a second insulating layer and a third insulating layer below the first insulating layer; providing a first metal layer between the first insulating layer and the second insulating layer; providing a second metal layer between the second insulating layer and the third insulating layer; Including, the first insulating layer, the second insulating layer, and the third insulating layer are formed from a material including an epoxy resin and a glass fiber; 12. The method for joining a lead portion and a protection circuit portion according to claim 11, wherein the first metal layer and the second metal layer are made of copper (Cu).

13. The method for bonding a lead portion and a protection circuit portion according to any one of claims 8 to 12, wherein the laser reflective layer is formed using silver (Ag).

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