A battery pack including a protection circuit module (PCM) having a connection structure that is directly connected to a battery cell

Abstract

The present invention discloses a connection structure between a battery cell and a protection circuit module (PCM) in a battery pack in which the battery cell and the PCM are connected, the battery cell includes a battery cell body and an electrode lead tab electrically connected to the battery cell body, the printed circuit board (PCB) constituting the PCM includes an insulating substrate, a second copper foil layer formed in contact with an upper surface of the insulating substrate, a first copper foil layer formed on the upper surface of the second copper foil layer, and a first prepreg layer interposed between the first copper foil layer and the second copper foil layer, and the electrode lead tab is directly bonded to the first copper foil layer. According to the present invention, a simple connection structure can be provided by directly bonding the battery cell and the PCM without a separate connection member, and process efficiency can be improved.

Description

[Technical field]

[0001] The present invention relates to a protection circuit module (PCM) having a connection structure that is directly bonded to an electrode lead tab of a battery cell, and a battery pack including the same. More specifically, the present invention relates to a PCB connection structure that is directly bonded to an electrode lead tab of a battery cell without a connecting member, by mixing carbon black having a high absorptivity in the wavelength band of a laser used in a bonding process with a prepreg layer of a printed circuit board (PCB) that constitutes the PCM, and a battery pack including the same. [Background technology]

[0002] The recent increase in demand for mobile electronic devices and environmentally friendly automobiles has been remarkable, and the need for secondary batteries to be used as energy sources has also increased rapidly. For this reason, research and development into high-performance, high-efficiency and high-stability secondary batteries has been actively carried out. Recently, lithium secondary batteries, which are lightweight, have high energy density, and have excellent storage and life characteristics, have been widely used.

[0003] Such secondary batteries contain various flammable materials, and thus have safety problems such as overcharging, over-discharging, overcurrent, heat generation, and fire or explosion due to chain reaction during use. Therefore, secondary batteries are protected by safety elements such as PTC (Positive Temperature Coefficient) elements, Protection Circuit Modules (PCM), and TCO (Thermal Cut-out), which can continuously detect and control the voltage, current, and temperature of a unit cell. Such safety elements, for example, elements constituting a PCM, are present on a Printed Circuit Board (PCB) on which a circuit electrically connected to the electrode terminals is provided, and the PCB is mounted or attached to the outside of the battery cell body to be electrically connected to the battery cell body. Therefore, in order to connect the PCB to the battery cell body, a method of welding and joining the electrode lead tab of the battery body to one side of the PCB is widely used.

[0004] The PCB has a first copper foil layer made of copper, which is a conductive material that allows electrical connection with the protection circuit and the battery cell, on one side. In the conventional connection structure between the battery cell and the PCB, when the first copper foil layer of the PCB and the electrode lead tab of the battery cell are directly welded to each other, the laser used passes through the PCB and damages the inside of the PCB. Therefore, a bent connection member made of a metal material is separately surface-mounted on the first copper foil layer of the PCB, and the lead tab of the battery cell is welded onto the connection member to join the electrode lead tab of the battery cell to the PCB so that the laser is blocked by the metal member or the laser is not directly irradiated from the top surface of the PCB to the PCB. For this reason, there is a problem that the number of joining steps increases due to the formation of a separate connection member, and the welded part becomes thicker.

[0005] The background art of the present invention is described in the following patent documents: [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2014-050896 Brochure [Patent Document 2] Republic of Korea Publication Patent No. 2009-0039053 [Patent Document 3] Japanese Patent Publication No. 8-34864 [Patent Document 4] Republic of Korea Publication Patent No. 2018-0084462 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide a connection structure between a PCM and a PCB that enables a PCB to be directly connected to an electrode lead tab of a battery cell without using a connecting member, and a battery pack in which a battery cell and a PCM are connected in this manner. [Means for solving the problem]

[0008] In a battery pack in which a battery cell and a PCM are connected according to an embodiment of the present invention, the battery cell includes a battery cell body and an electrode lead tab electrically connected to the battery cell body, and a PCB constituting the PCM includes an insulating substrate, a second copper foil layer formed in contact with an upper surface of the insulating substrate, a first copper foil layer formed on an upper surface of the second copper foil layer, and a first prepreg layer interposed between the first copper foil layer and the second copper foil layer, and the electrode lead tab is directly bonded to the first copper foil layer.

[0009] The direct joining is performed by laser welding.

[0010] The first prepreg layer is characterized in that it is formed containing a material that has a high absorptance in the wavelength band of the laser used for the laser welding.

[0011] The material contained in the first prepreg layer and having a high absorptivity at the wavelength of the laser used for the laser welding is characterized in that it is carbon black.

[0012] The PCB further includes a third copper foil layer formed in contact with the lower surface of the insulating substrate, a fourth copper foil layer formed below the third copper foil layer, and a second prepreg layer interposed between the third copper foil layer and the fourth copper foil layer, and the second prepreg layer contains carbon black.

[0013] The present invention also provides a battery pack including the above-mentioned connection structure between a battery cell and a PCM. Effect of the Invention

[0014] A battery pack according to an embodiment of the present invention includes a battery cell, an electrode lead tab electrically connected to the battery cell, a PCM bonded to the battery cell, and a PCB included in the PCM, and the PCB includes a first prepreg layer having carbon black mixed between a first copper foil layer and a second copper foil layer, so that a laser irradiated in a process of bonding the electrode lead tab of the battery cell and the first copper foil layer of the PCB is absorbed by the carbon black without being transmitted through the lower surface of the first prepreg layer, thereby preventing damage to the inner layer or protective circuit element of the PCB by the laser. As a result, a bonding process in which a laser is directly irradiated to the electrode lead tab of the battery cell and the first copper foil layer of the PCB can be performed without a separate connecting member used in the conventional technology, and therefore, the process efficiency can be improved by a simple bonding process, and a connection structure between a battery cell and a PCB with a simple structure can be formed. [Brief description of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view of a PCM including a connection member according to a prior art of the present invention. [Diagram 2] 1 is a perspective view of a battery pack having a connection structure including a connection member according to a conventional technique of the present invention; [Diagram 3] 1 is a cross-sectional view of a battery pack including a connecting member according to a prior art of the present invention; [Figure 4] 1 is a perspective view of a battery pack having a connection structure according to an embodiment of the present invention; FIG. [Diagram 5] 1 is a cross-sectional view of a battery pack having a connection structure according to an embodiment of the present invention. [Figure 6] 2 is a cross-sectional view of a PCM excluding a connecting member according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 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. The embodiments of the present invention 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 explain the embodiments of the present invention, the drawings may be exaggerated, and parts that are not related to the description may be omitted from the drawings, and the same reference numerals in the drawings indicate the same components.

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0018] Referring to FIG. 4, the battery pack according to the present invention includes a battery cell 100, an electrode lead tab 120 electrically connected to the battery cell 100, a PCM 200, and a PCB 210 included in the PCM, the PCB 210 including a prepreg layer mixed with carbon black.

[0019] 1. Configuration of the battery pack of the present invention

[0020] A. 100 battery cells

[0021] (1) Battery cell body 110

[0022] The battery cell body 110 is generally configured by disposing a positive electrode plate and a negative electrode plate, to which a positive electrode active material and a negative electrode active material are respectively applied, with a separator between them, and sealing the plates together with an electrolyte in a battery case.

[0023] (2) Electrode lead tab 120

[0024] The electrode lead tabs 120 are formed on one side of the battery case, and more specifically, are configured as electrode lead tabs 120 electrically connected to the positive and negative electrode plates and protruding to the outside of the battery case, and the battery cell body 110 can be electrically connected to the PCM 200 through the electrode lead tabs 120. The electrode lead tabs 120 connected to the positive and negative electrode plates may protrude in a line from one side of the battery case or may be disposed on both sides, which can be applied depending on the shape of the battery case and the structure of the battery.

[0025] B. Battery Protection Module (PCM: Protection Circuit Module) 200

[0026] The PCM 200 is a type of safety element constituting the secondary battery pack, and performs a function of continuously detecting and controlling the voltage, current, temperature, etc. of the battery cell 100, thereby protecting the secondary battery pack from the risk of fire or explosion due to overcharge, overdischarge, overcurrent, heat generation, and chain reaction of the battery cell 100. The PCM 200 is mounted with a PCB 210 on which a circuit electrically connected to the electrode terminals of the PCM 200 is printed, and is electrically connected to the battery cell 100 through the electrode lead tab 120 of the battery cell joined to the PCB 210.

[0027] (1) Printed Circuit Board (PCB) 210

[0028] The PCB 210 refers to a board in which a circuit including a conductive material such as copper is printed on the surface of a board made of an electrically insulating material. A protection circuit element used in a secondary battery may be mounted on the PCB 210, and the mounted element is electrically connected to the battery cell 100 via the electrode lead tab 120 of the battery cell 100 connected to the PCB 210 circuit.

[0029] This will be described with reference to Figures 1 and 6. Figure 1 is a cross-sectional view of a PCM 200 including a connecting member 300 according to the prior art.

[0030] 6 is a cross-sectional view of a PCB 210 according to an embodiment of the present invention. The PCM 200 of the present invention is configured excluding the connection member 300, and is formed by including carbon black in the first prepreg layer, as described below.

[0031] Such a PCB 210 can be formed into a single-sided PCB, a double-sided PCB, or a single-layer / multi-layer PCB structure depending on the arrangement of the copper foil layers and the number of copper foil layers stacked.

[0032] 2.1.1 Insulating Substrate 211 The insulating substrate 211 is a substrate that exhibits insulating properties and is made of thermosetting resin such as CEM-1 (Composite epoxy material-1, paper, glass cloth, epoxy resin copper-clad laminate), CEM-3 (Composite epoxy material-3, glass cloth, glass nonwoven fabric composite substrate epoxy resin copper-clad laminate), or FR-4 (Flame retardant-4, heat-resistant glass cloth substrate epoxy resin copper-clad laminate) made of glass fiber impregnated with epoxy resin, and constitutes the PCB 210. In general, the PCB 210 is a single- or double-sided single-layer PCB formed by forming wiring circuits on one or both sides of the insulating substrate 211, and when two or more copper foil layers are formed on one side, it is called a multi-layer PCB. Although FIGS. 1 and 6 show an example of a double-sided multi-layer PCB, the technical idea of ​​the present invention is not limited thereto.

[0033] 2.1.2 First Copper Foil Layer 212

[0034] The copper foil layer is formed on the upper side of the copper foil layer formed on one side of the insulating substrate 211 to form a circuit, and components mounted on the PCB 210 are connected via the printed circuit and electrically connected to the battery cell 100 via the electrode lead tab 120. In the connection structure of the present invention, the first copper foil layer 212 forms a connection structure directly joined to the electrode lead tab 120 of the battery cell 100 without a separate connection member 300, and is formed on the upper side of a second copper foil layer 312 described below.

[0035] 2.1.3 Second copper layer 213

[0036] This is a copper foil layer formed on the upper surface of insulating substrate 211 to form a circuit. In the case of the conventional technology, during laser welding in the assembly process for joining first copper foil layer 212 and electrode lead tab 120, there is a possibility that the laser directly irradiated to PCB 210 will penetrate into the inner layer of PCB 210 after forming a joint, damaging second copper foil layer 213. It is disposed below first copper foil layer 212 in contact with insulating substrate 211.

[0037] 2.1.4 Third Copper Layer 214

[0038] This is a copper foil layer that constitutes a circuit and is formed in contact with the lower surface of the insulating substrate 211. In the case of the conventional technology, during laser welding in the assembly process of joining the first copper foil layer 212 and the electrode lead tab 120, the laser that is directly irradiated to the PCB 210 may penetrate into the inner layer of the PCB 210 after forming the joint, and may damage the second copper foil layer 213 and the third copper foil layer.

[0039] 2.1.5 Fourth Copper Layer 215

[0040] A copper foil layer that is formed under the third copper foil layer 214 on the bottom surface of the insulating substrate 211 and constitutes a circuit, is connected via a printed circuit, and has a protective circuit element 220 disposed thereon. In the case of a single-sided PCB, the third and fourth copper foil layers can be omitted.

[0041] 2.1.6 First Prepreg Layer 216

[0042] (i) Prior Art

[0043] The prepreg is formed in a semi-cured state by impregnating glass fiber with epoxy resin to form the insulating substrate 211 of the PCB 210, and is used as an insulating adhesive for laminating a copper foil layer on a single-layer PCB in a multi-layer PCB structure. When welding the electrode lead tab 120 of the battery cell 100 and the first copper foil layer 212 of the PCB 210, a laser with a wavelength band of 1070 μm is used, and the prepreg made of glass fiber and epoxy resin shows optical characteristics of high transmittance in the laser wavelength band. Therefore, when attempting to join the electrode lead tab 120 of the battery cell to the first copper foil layer 212, if a laser is directly irradiated from the upper surface of the joining portion, the first copper foil layer 212 and the inner layer of the PCB 210 including the second and third copper foil layers, and the protection circuit element 220 mounted under the insulating substrate 211 may be damaged by the transmitted laser.

[0044] Therefore, in the past, in order to prevent damage to the inner layer of the PCB 210 by the laser, a separate metallic connection member 300 such as nickel was further used to connect the PCB 210 to prevent the laser from being directly irradiated onto the top surface of the PCB 210. However, the addition of the connection member 300 complicates the process and causes problems such as thickening of the joint.

[0045] (ii) First prepreg layer 216 of the present invention

[0046] The first prepreg layer 216 is interposed between the first copper foil layer 212 and the second copper foil layer 213 .

[0047] In the process of manufacturing the PCB 210, the prepreg of the present invention further mixes carbon black into epoxy to form an insulating substrate 211, and a copper foil layer is formed on one or both sides of the formed insulating substrate 211 to manufacture a single-layer PCB. A multi-layer PCB can be manufactured by further laminating a copper foil layer on the formed single-layer PCB using the prepreg as an insulating adhesive, and the prepreg of the present invention is used by mixing carbon black. In the bonding process, the laser irradiated to the PCB 210 bonds the electrode lead tab 120 and the first copper foil layer 212, and the excess laser is transmitted to the first prepreg layer. The carbon black mixed in the prepreg layer of the present invention has a characteristic of exhibiting a high absorption rate in the wavelength band of the laser used in the bonding process of the electrode lead tab 120 of the battery cell 100, so that the excess laser irradiated to the PCB 210 is absorbed by the carbon black of the first prepreg layer 216. Therefore, the laser does not penetrate to the lower part of the first prepreg layer 216, so that damage to the inner layers of the PCB 210 by the laser can be prevented.

[0048] Carbon black has low electrical conductivity and high light absorbance, and therefore can be mixed into the insulating substrate 211 of the PCB 210 or the prepreg layer used in laminating the copper foil layer to maintain insulating properties, and absorbs the laser used in the welding process between the electrode lead tab 120 and the first copper foil layer 212. Therefore, in the case of the PCB 210 having carbon black mixed into the first prepreg layer 216, the inner layer of the PCB 210 is not damaged by the laser even without a separate connection member 300, so that a joining process can be performed in which a laser is directly irradiated onto the joint between the electrode lead tab 120 of the battery cell 100 and the first copper foil layer of the PCB 210, and as a result, a connection structure between the battery cell 100 and the PCB 210 can be formed with a simple process and structure.

[0049] (iii) Second prepreg layer 217 of the present invention

[0050] If a multi-layer PCB is applied to the bottom side of the double-sided PCB, a second prepreg layer 217 is interposed between the third and fourth copper foil layers.

[0051] The second prepreg layer 217, like the first prepreg layer 216, may be formed containing carbon black, which can more efficiently prevent laser damage to the protection circuit element 220 mounted on the underside of the PCB 210.

[0052] (2) Protection circuit element (PCM element) 220

[0053] The protection circuit element 220 is a passive or active element including a protection circuit, and may be mounted on the upper or lower part of the PCB 210, and may be laminated in a plurality of layers. The protection circuit element 220 protects the secondary battery pack from the risk of fire or explosion due to overcharge, overdischarge, overcurrent, heat generation, and chain reaction of the battery cell. When the protection circuit element 220 is mounted on the lower part of the PCB 210, it may be damaged by a laser that penetrates the PCB 210 during laser welding according to the conventional technology. However, in the PCB 210 of the present invention, the laser is absorbed / blocked by the first prepreg layer 216 mixed with the carbon black and the second prepreg layer 217 mixed with carbon black, so that the protection circuit element 220 can be prevented from being damaged by the laser.

[0054] 2. Battery pack connection structure of the present invention

[0055] As shown in Figures 4 and 5, a connection structure of a battery pack in which a battery cell 100 and a PCM 200 are directly bonded according to a preferred embodiment of the present invention includes a battery cell 100, an electrode lead tab 120 protruding from the battery cell 100, a PCB 210 and a protection circuit element that constitute the PCM 200.

[0056] Fig. 6 is an exploded cross-sectional view of Fig. 5. As shown in Fig. 6, in a PCB 210 according to a preferred embodiment of the present invention, a second copper foil layer 213 and a third copper foil layer 214 are formed on the upper and lower surfaces of an insulating substrate 211, and a first copper foil layer 212 and a fourth copper foil layer 215 are formed on the upper part of the second copper foil layer 213 and the lower part of the third copper foil layer 214, respectively. In addition, a first prepreg layer 216 containing carbon black is interposed between the first copper foil layer 212 and the second copper foil layer 213, and a second prepreg layer 217 is also formed between the third copper foil layer 214 and the fourth copper foil layer 215.

[0057] A laser-based joining method is used to join the electrode lead tab 120 of the battery cell 100 and the first copper foil layer 212 of the PCB 210, and the laser wavelength is in the 1070 μm wavelength band. Since the prepreg layer of the present invention is formed containing carbon black that has the property of absorbing lasers in the above wavelength band, the laser irradiated to the PCB 210 during laser welding is absorbed by the first prepreg layer 216 and does not penetrate to the lower surface of the first prepreg layer. Therefore, the inner layer of the PCB 210 including the second copper foil layer 213 and the protection circuit element 220 mounted on the PCB 210 are not damaged.

[0058] The connection structure of the battery pack in which the battery cell 100 and the PCM 200 are directly bonded to each other according to the present invention does not include a separate connection member 300 described in the Background of the Invention section, and the electrode lead tab 120 of the battery cell 100 is directly bonded and connected to the first copper foil layer 212 of the PCB 210. Therefore, the connection member 300 and the process of mounting the connection member 300 on the first copper foil layer 212 are not required, and the thickness and structure of the connection part are simplified by an amount corresponding to the volume of the connection member 300 removed in the bonding process, so that the volume of the entire battery pack can be reduced and the entire assembly process of the battery pack in which the battery cell and the PCM 200 are bonded to each other can be simplified.

[0059] The main symbols and their names used in the drawings of the present invention are as follows: [Explanation of symbols]

[0060] 10 Battery Pack 100 Battery Cells 110 Battery cell body 120 Electrode lead tab 200 PCM 210 PCB 211 Insulating substrate 212 1st copper foil layer 213 2nd copper layer 214 3rd copper layer 215 4th copper layer 216 First prepreg layer 217 Second prepreg layer 220 Protection circuit element 300 Connection member

Claims

1. A connection structure between a battery cell and a protection circuit module (PCM) in a battery pack in which the battery cell and the protection circuit module (PCM) are connected, The battery cell includes: A battery cell body; an electrode lead tab electrically connected to the battery cell body; comprising The printed circuit board (PCB) constituting the protection circuit module (PCM) is An insulating substrate; a second copper foil layer formed in contact with an upper surface of the insulating substrate; a first copper foil layer formed on the second copper foil layer; a first prepreg layer interposed between the first copper foil layer and the second copper foil layer; comprising The electrode lead tabs of the battery cells are directly joined to the first copper foil layer of the protection circuit module (PCM) by laser welding; A connection structure between a battery cell and a protection circuit module (PCM), wherein the first prepreg layer is formed including a material having a high absorption rate in the wavelength band of a laser used for the laser welding.

2. 2. The connection structure between a battery cell and a protection circuit module (PCM) according to claim 1, wherein the material contained in the first prepreg layer and having a high absorption rate at the wavelength of the laser used for the laser welding is carbon black.

3. The printed circuit board (PCB) includes: a third copper foil layer formed in contact with the lower surface of the insulating substrate; a fourth copper foil layer formed under the third copper foil layer; a second prepreg layer interposed between the third copper foil layer and the fourth copper foil layer; Further comprising: The connection structure between a battery cell and a protection circuit module (PCM) according to claim 1 or 2, wherein the second prepreg layer contains carbon black.

4. A battery pack comprising the connection structure between the battery cell according to any one of claims 1 to 3 and a protection circuit module (PCM).

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