PCB including laser blocking portion and battery cell assembly including such PCB

Abstract

The present invention relates to a PCB that includes a first layer including a welding spot for laser welding, and a laser blocking portion that is included in a second layer that is a layer below the first layer and is located at the same position as the welding spot based on the stacking direction of the first and second layers, wherein the laser blocking portion includes a material that reflects a laser irradiated for welding at the welding spot or that does not allow the laser to pass through while the welding spot is being welded.

Description

[Technical field]

[0001] (Reference to Related Application) This application claims the benefit of priority to Korean Patent Application No. 10-2022-0105080 filed on August 22, 2022, and all contents disclosed in the Korean Patent Application are incorporated herein by reference.

[0002] (Technical field) The present invention relates to a PCB including a laser blocking portion, and more particularly to a PCB including a laser blocking portion for preventing a laser irradiated to a welding spot of the PCB from damaging a circuit on a layer below the welding spot, and a battery cell assembly including such a PCB. [Background technology]

[0003] Lithium secondary batteries measure and monitor the temperature and voltage of battery cells for safety. For this purpose, a PCB manufactured for this purpose is often electrically connected to the battery cell, and the electrode leads of the battery cell are welded to the welding spots of the PCB. In the past, welding was performed using a soldering station or a soldering iron, but recently laser welding is often used.

[0004] Laser welding can be applied to small areas, the physical properties of the material are the same before and after welding, and the mechanical properties after welding are excellent. Laser welding is highly efficient, so it is often used in large-scale processes equipped with automated systems.

[0005] When using a laser to weld an electrode lead to a PCB welding spot, problems occur if the laser is not precisely focused on the PCB welding spot. Even if the laser is irradiated to the correct position, if the DOF (Depth of Focus) of the laser is greater than the sum of the thickness of the PCB welding spot and the electrode lead, the laser will affect other layers inside the PCB. This can be especially problematic when the thickness between layers of the PCB is thin.

[0006] For example, if the DOF of the laser is formed between the top layer of a PCB and a lower layer below it, the laser may affect the lower layer, or the top layer and the lower layer may be welded together, thus damaging the circuit formed on the lower layer.

[0007] Fig. 1 shows an exploded perspective view of a conventional PCB. Fig. 1 shows, as an example, a first layer 100 at the top of the PCB and a second layer 200 located below it. Although not shown in Fig. 1, an adhesive layer may be added between the first layer 100 and the second layer 200.

[0008] The first layer 100 includes two welding spots 110 for respectively bonding the positive and negative leads of a pouch-type battery cell.

[0009] Although the second layer 200 is generally printed with a circuit pattern, it may be configured such that the circuit pattern is not printed at positions corresponding to the two welding spots 110 in the vertical direction. In Fig. 1, spaces 210 are formed at positions corresponding to the two welding spots 110 in the vertical direction. The second layer 200 has a circuit pattern formed in the remaining portion excluding the empty spaces 210.

[0010] Even if no circuit pattern is formed or a simple space is formed below the topmost layer where the welding spot is located, if the laser is not focused on the welding spot or if the laser DOF is formed up to an adhesive layer such as a prepreg between the first layer and the second layer below it, there is a problem that the topmost layer and the layer below it may be welded to each other.

[0011] Such problems are not limited to the topmost layer, the first layer, and the second layer below it, but can also occur between the layers in between.

[0012] Such poor welding problems are directly related to the safety of battery cells, battery modules, and battery packs, and since batteries use thin PCBs, a fundamental solution to such problems is needed. In PCB laser welding, a technology is needed that can prevent internal circuits from being damaged even if the laser is out of focus or the DOF of the laser is large.

[0013] In Patent Document 1, a deep cavity is formed in a PCB in order to insert various components into the PCB. A metal pattern is formed to act as a laser stopper when irradiating a laser for cavity processing, but the patent does not recognize any technology for preventing the laser from unnecessarily affecting other layers when welding electrode leads to the PCB.

[0014] Patent Documents 2 to 5 do not specifically disclose means for blocking the laser so that it does not affect other layers.

[0015] As described above, in laser welding of PCBs, no clear solution has been presented that can prevent damage to internal circuits even when the laser is out of focus or the DOF of the laser is large. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Korean Patent Publication No. 10-2017-0067472 [Patent Document 2] Korean Patent Publication No. 10-2018-0036404 [Patent Document 3] Korean Patent Publication No. 10-2016-0055539 [Patent Document 4] Korean Patent Publication No. 10-2018-0013669 [Patent Document 5] JP 1996-304668 A Summary of the Invention [Problem to be solved by the invention]

[0017] The present invention has been made to solve the above problems, and aims to provide a PCB that can prevent damage to the internal circuit of the PCB even when the laser is out of focus or the DOF of the laser is large, and a laser welding method using such a PCB. [Means for solving the problem]

[0018] To achieve this object, the PCB according to the present invention includes a first layer including a welding spot for laser welding, and a laser blocking portion included in a second layer, which is a layer below the first layer, and located at the same position as the welding spot based on the stacking direction of the first and second layers, and the laser blocking portion may include a material that reflects a laser irradiated for welding at the welding spot or that does not allow the laser to pass through while the welding spot is being welded.

[0019] The laser blocking portion may have a size sufficient to include the entire welding spot area based on the stacking direction of the first layer and the second layer.

[0020] The laser block may be made of a non-conductive or conductive material and may not be electrically connected to any circuitry on the PCB.

[0021] The laser blocking portion may include at least one of a metal, a ceramic, and a polymer.

[0022] The laser blocking portion may include at least one of silver, copper, aluminum, iron, and nickel.

[0023] The laser block can be a metal foil of the same material as the metal foil used for the circuit traces on the PCB.

[0024] The laser block can be located on top of the second layer.

[0025] An adhesive layer may be added between the first and second layers.

[0026] The present invention provides a battery cell assembly that includes a PCB.

[0027] The battery cell assembly may have electrode leads of the battery cells welded to the welding spots of the first layer.

[0028] The present invention provides a method for welding, and more particularly, a method for laser welding, using a PCB.

[0029] Furthermore, the present invention can also be provided in the form of a combination of various means for solving the above problems. Effect of the Invention

[0030] As described above, the PCB according to the present invention can prevent the laser from penetrating into the inside of the PCB, and therefore can prevent unwanted welding from being performed inside the PCB.

[0031] In addition, it is possible to prevent the circuit pattern formed on the PCB from being damaged by the laser that has penetrated into the PCB.

[0032] In addition, since the laser blocking portion is not electrically connected to the circuit patterns constituting the PCB, even if the DOF of the laser includes the second layer, it does not affect other circuit patterns formed on the PCB. [Brief description of the drawings]

[0033] [Figure 1] FIG. 1 is an exploded perspective view of a conventional PCB. [Diagram 2] FIG. 2 is an exploded perspective view of a PCB according to the present invention. [Diagram 3] 3 is a partial plan view of a battery cell assembly in which electrode leads of a pouch-type battery cell are coupled to the PCB of FIG. 2. [Figure 4]1 is a vertical cross-sectional view of a conventional PCB and a PCB according to the present invention when electrode leads are bonded to the PCB. [Diagram 5] 13 is a photograph showing a welding result according to a comparative example. [Figure 6] 11 is a photograph showing a welding result according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings, in which a person having ordinary skill in the art to which the present invention pertains can easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, detailed description of related well-known functions or configurations will be omitted if it is determined that such detailed description may unnecessarily obscure the gist of the present invention.

[0035] In addition, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes not only the case where the part is directly connected to another part, but also the case where the part is indirectly connected via another element between the two parts. In addition, when a part includes a certain component, it does not mean that the other component is excluded, but that the part may further include the other component, unless otherwise specified.

[0036] Furthermore, descriptions that specify or limit components are applicable to all inventions and are not limited to a particular invention unless otherwise specified.

[0037] Furthermore, throughout the description of the present invention and the claims, the singular includes the plural unless otherwise stated.

[0038] In addition, throughout the description of the present invention and the claims, unless otherwise stated, "or" includes "and." Therefore, "including A or B" means three cases: including A, including B, or including both A and B.

[0039] The invention will now be explained with reference to the drawings and in conjunction with detailed embodiments.

[0040] Fig. 2 is an exploded perspective view of the PCB according to the present invention. PCB is an abbreviation of Printed Circuit Board, which means a printed circuit board. In general, FR-4, a material made of glass fiber and epoxy, is used, and components can be electrically connected to each other through the copper plates attached to both sides of the FR-4.

[0041] 2, the PCB according to the present invention includes a first layer 100 located at the top outermost layer and including a welding spot 110 for laser welding, and a second layer 200 which is a layer below the first layer 100. The second layer 200 includes a laser blocking portion 220 located at the same position as the welding spot 110 based on the stacking direction of the first layer 100 and the second layer 200. The laser blocking portion 220 is configured to completely overlap the welding spot 110 below the welding spot 110 based on the stacking direction of the first layer 100 and the second layer 200, or to have a size that includes the entire area of ​​the welding spot 110.

[0042] The first layer 100 includes welding spots 110 for connecting an external device, such as an electrode lead of a pouch-type battery cell, to the PCB, and a circuit pattern may be formed on the remaining portion excluding the welding spots. The circuit pattern is a conductive pattern formed on the board from a conductive material such as copper, and may include a signal circuit pattern for signal transmission, a power layer for power supply, and a ground layer for power supply cutoff.

[0043] The second layer 200 may be configured in a two or more layer structure such as a circuit pattern layer and a base layer, and in order to prevent the laser from reaching the second layer 200, the laser blocking portion 220 may be disposed at the top end of the second layer 200. Even if the laser reaches a depth of the second layer 200, it is reflected or blocked by the laser blocking portion 220 at the top end of the second layer 200.

[0044] The laser blocking portion 220 may include a material that reflects a laser irradiated to the welding spot 110 for welding or prevents the laser from passing through the welding spot 110 while the welding spot 110 is being welded.

[0045] The laser blocking portion 220 may be made of a non-conductive or conductive material and may not be electrically connected to any circuitry on the PCB.

[0046] Therefore, since the DOF of the laser includes the second layer, even if the first layer and the second layer are bonded together, the circuit pattern formed on the second layer is not affected.

[0047] Specifically, the laser blocking portion 220 may include at least one of metal, ceramic, and polymer, for example, the laser blocking portion may include at least one of silver, copper, aluminum, iron, and nickel.

[0048] In one embodiment, the laser blocking portion 220 can use a metal foil made of the same material as the metal foil used for the circuit pattern of the PCB.

[0049] When a green laser is used for laser welding, copper can be used as the laser blocking portion, taking into consideration that copper has the property of reflecting the green laser.

[0050] FIG. 3 is a partial plan view of a battery cell assembly in which electrode leads of a pouch-type battery cell are coupled to the PCB of FIG.

[0051] Referring to FIG. 3, the pouch-type battery cell 20 is manufactured by housing an electrode assembly in a pouch-type battery case made of a laminate sheet including an outer coating layer, a metal layer, and an inner adhesive layer, and then sealing the case.

[0052] The electrode assembly may be a stack-type electrode assembly in which a positive electrode and a negative electrode are stacked with a separator interposed between them. The positive electrode and the negative electrode each include a positive electrode tab and a negative electrode tab protruding to one side to serve as a current transfer path, the positive electrode tab being connected to a positive electrode lead, and the negative electrode tab being connected to a negative electrode lead.

[0053] The electrode leads 10 including the positive and negative leads protrude outward from one side of the outer periphery of the pouch-type battery case. The electrode leads 10 are connected to welding spots of the PCB by laser welding, thereby assembling the battery cell assembly 1000 including the PCB.

[0054] FIG. 4 is a vertical cross-sectional view of a conventional PCB and a PCB according to the present invention when electrode leads are bonded to the PCB.

[0055] FIG. 4(a) is a vertical sectional view of a conventional PCB to which an electrode lead is coupled, and FIG. 4(b) is a vertical sectional view of a PCB to which an electrode lead is coupled according to the present invention.

[0056] Referring to FIG. 4, an electrode lead 10 is placed on top of the copper plating as a welding spot on the top surface of the first layer 100 of the PCB, and a bond between the electrode lead 10 and the PCB is formed by laser welding in which a laser is irradiated from above the electrode lead 10.

[0057] The first layer 100 of the PCB includes not only welding spots but also a circuit pattern printed with an electrically conductive material on a base layer. The base layer may be made of a flexible and insulating film, for example, a polyimide material. In particular, transparent polyester or polypropylene may be used in addition to the polyimide to maximize light transmittance.

[0058] The circuit pattern is for transmitting a predetermined electrical signal, and is formed to a thickness of about 5 μm to 20 μm and may be made of a metal material such as copper foil (Cu). The surface of the copper foil may be plated with a metal such as tin, gold, or nickel.

[0059] The PCB shown in FIG. 4(a) includes a prepreg layer 500 for insulation and adhesion located under the first layer 100, a third layer 300 having copper foil only on the underside of the FR-4 301, and a fourth layer 400 located at the bottom of the PCB and including copper plating and copper foil.

[0060] FR-4 stands for "copper-clad laminate," a type of board made of a material bonded together with epoxy resin and glass fiber, with copper foil applied to one or both sides.

[0061] A prepreg layer 500 is further provided between the third layer 300 and the fourth layer 400 for bonding them together.

[0062] A space 201 is located between the prepreg layer 500 below the first layer 100 and the FR-4, and a DOF is formed from the electrode lead 10 to the prepreg layer 500 below the first layer 100.

[0063] If the DOF is out of focus, there is a problem that the laser can penetrate to the third layer 300 or the first layer and the third layer 300 including the FR-4 301 may be welded through the prepreg layer 500 .

[0064] The PCB shown in FIG. 4(b) differs from that in FIG. 4(a) in that a second layer 200 has been added.

[0065] Specifically, the electrode lead 10 is placed on top of the copper plating as a welding spot on the top surface of the first layer 100, and a bond between the electrode lead 10 and the PCB is formed by laser welding in which a laser is irradiated from above the electrode lead 10.

[0066] 4(b), the third layer 300 has a form in which copper foil is applied to both sides of FR-4 301, and the second layer 200 formed on the upper surface functions as a laser blocking layer that reflects or blocks laser when the DOF extends to the depth of the second layer 200. The second layer 200 is configured not to be electrically connected to the circuit patterns formed on the first layer 100, the third layer 300, and the fourth layer 400, so that the circuit patterns formed on the first layer 100, the third layer 300, and the fourth layer 400 can be prevented from being affected by laser welding.

[0067] However, the circuit patterns formed on the first layer 100, the third layer 300 and the fourth layer 400 may form electrical connections with each other.

[0068] In the PCB shown in (b) of Fig. 4, a prepreg layer 500 is interposed between the first layer 100 and the second layer 200 as an adhesive layer for bonding them. The prepreg layer 500 has insulating properties as well as adhesive properties. Therefore, even if the third layer 300 and the fourth layer 400 are bonded via the prepreg layer 500 therebetween, the third layer 300 and the fourth layer 400 are not connected via the prepreg layer 500 unless a configuration for connecting the third layer 300 and the fourth layer 400 is included.

[0069] As such, the PCB and battery cell assembly including the same according to the present invention includes a laser blocking portion in the second layer 200 below the first layer of the PCB, so that even if the DOF of the laser becomes deep or the focus is shifted, the laser can be reflected or blocked by the laser blocking portion, thereby preventing the occurrence of laser welding defects.

[0070] The present invention will be described below with reference to examples, which are provided for easier understanding of the present invention and are not intended to limit the scope of the present invention.

[0071] <Comparative Example> A nickel plate was placed on a PCB including a second layer that had no laser blocking portion below the first layer of the PCB, and laser welding was performed from the nickel plate to the PCB.

[0072] Here, the DOF of the laser was set to reach the first layer of the PCB and the second layer where there was no laser blocking portion, and welding was performed.

[0073] FIG. 5 is a photograph showing the welding result according to the comparative example.

[0074] FIG. 5(a) is a photograph of the laser welding result of the nickel plate, FIG. 5(b) is an X-ray photograph of the first layer of the PCB after the nickel plate has been removed, and FIG. 5(c) is a photograph of the second layer of the PCB.

[0075] The upper surface of the nickel plate in Fig. 5(a) shows a continuous circular laser weld formed in the horizontal direction. Referring to the X-ray photograph of the first layer of the PCB in Fig. 5(b), it can be seen that a hole with the same shape as the laser weld shown in Fig. 5(a) was formed in the first layer of the PCB, and in Fig. 5(c), it can be seen that the circuit pattern formed in the second layer of the PCB has been burned by the laser.

[0076] Therefore, if the PCB does not include a structure for blocking the laser beam of laser welding, the laser beam will penetrate not only the first layer of the PCB but also the second layer, damaging the circuit pattern.

[0077] <Example> A nickel plate was placed on a PCB with a second layer containing a laser blocking portion below the first layer of the PCB, and laser welding was performed with the nickel plate toward the PCB.

[0078] FIG. 6 is a photograph showing the welding result according to the embodiment.

[0079] FIG. 6(a) is a photograph of the laser welding result of the nickel plate, FIG. 6(b) is an X-ray photograph of the first layer of the PCB after the nickel plate has been removed, and FIG. 6(c) is a photograph of the second layer of the PCB.

[0080] On the top surface of the nickel plate in Fig. 6(a), two continuous linear laser welds are formed in the horizontal direction. Referring to the X-ray photograph of the first layer of the PCB in Fig. 6(b), it can be seen that there are no hole traces corresponding to the laser welds in the first layer of the PCB, unlike Fig. 5(b). Also, in Fig. 6(c), it can be seen that there is no damage to the circuit pattern of the second layer of the PCB, unlike Fig. 5(c).

[0081] Therefore, when laser welding is performed using a PCB including a laser blocking portion as in the present invention, the laser beam can be blocked at the lower part of the first surface that is joined to the nickel plate, thereby ensuring weldability between the nickel plate and the PCB and preventing damage to the internal circuitry of the PCB.

[0082] Those skilled in the art will appreciate that various applications and modifications within the scope of the present invention will be possible based on the above content. [Explanation of symbols]

[0083] 10 Electrode Lead 20 Pouch-type battery cells 100 1st layer 110 Welding Spot 200 2nd layer 201, 210 space 220 Laser cutoff section 300 3rd layer 301 FR-4 400 4th layer 500 prepreg layers 1000 Battery Cell Assembly

Claims

1. a first layer including weld spots for laser welding; a laser blocking portion included in a second layer that is a lower layer of the first layer, the laser blocking portion being located at the same position as the welding spot based on a stacking direction of the first layer and the second layer. A PCB comprising: The laser blocking portion includes a material that reflects a laser irradiated for welding at the welding spot or prevents the laser from passing through the welding spot while the welding spot is being welded. PCB.

2. The PCB of claim 1 , wherein the laser blocking portion has a size sufficient to include the entire welding spot in a stacking direction of the first and second layers.

3. The PCB of claim 1 , wherein the laser blocking portion is made of a non-conductive or conductive material and is not electrically connected to any circuit of the PCB.

4. The PCB of claim 3 , wherein the laser blocking portion comprises at least one of a metal, a ceramic, and a polymer.

5. The PCB of claim 4 , wherein the laser blocking portion comprises at least one of silver, copper, aluminum, iron, and nickel.

6. The PCB of claim 1 , wherein the laser blocking portion is a metal foil made of the same material as the metal foil used for the circuit pattern of the PCB.

7. The PCB of claim 1 , wherein the laser blocking portion is located at a top edge of the second layer.

8. The PCB of claim 1 , further comprising an adhesive layer between the first layer and the second layer.

9. A battery cell assembly comprising a PCB according to any one of claims 1 to 8.

10. 10. The battery cell assembly according to claim 9, wherein an electrode lead of a battery cell is welded to a welding spot of the first layer.

11. A method of welding using a PCB according to any one of claims 1 to 8.

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