A battery pack in which the circuit board and electrode leads are directly joined using laser welding

Abstract

The present invention relates to a battery pack including a battery cell including a pair of electrode leads consisting of a positive electrode lead and a negative electrode lead, a pack housing that houses the battery cell, and a protection circuit module in which a protection circuit that controls the operation of the battery cell is formed on a PCB, wherein the electrode leads are directly joined to a surface copper foil layer of the PCB by laser welding.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2020-0149131, filed on November 10, 2020, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a battery pack in which a substrate of a protection circuit module and an electrode lead are directly joined using a continuous wave laser welding method. [Background technology]

[0003] As technological developments and demand for mobile devices such as smartphones, notebook PCs, and digital cameras increase, technologies related to rechargeable secondary batteries are being actively developed. Secondary batteries are an alternative energy source to fossil fuels, which generate air pollutants, and are used in electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (P-HEVs), energy storage devices (ESSs), and other vehicles.

[0004] Currently, the types of secondary batteries that are widely used include lithium secondary batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and nickel-zinc batteries. In particular, research and development of lithium secondary batteries, which have the advantages of high operating voltage and high energy density per unit weight, is being actively carried out.

[0005] However, lithium secondary batteries have the risk of overheating and explosion due to overcharging, overcurrent, or external impact.

[0006] Therefore, lithium secondary batteries are generally housed in a housing to protect the secondary batteries from external impacts, and battery packs are generally manufactured by incorporating a Protection Circuit Module (PCM) that can control overcharging, overcurrent, etc.

[0007] In order to electrically connect the protection circuit module to the secondary battery, it is necessary to join the electrode leads to the protection circuit module.

[0008] Although various known welding methods can be used for this joining method, laser welding, particularly pulsed laser welding using an Nd:YAG laser with an oscillation wavelength of about 0.5 to 1.1 μm, has been mainly used recently in view of increasing productivity.

[0009] However, when the electrode lead is made of aluminum or an aluminum alloy, conventional laser welding has problems such as high-temperature cracking of aluminum, low absorption rate, and a decrease in electrical conductivity due to an aluminum-copper intermetallic compound formed at the junction with the surface copper foil layer of the protection circuit module substrate, which are dissimilar metals. This makes it difficult to directly weld the electrode lead to the protection circuit module substrate.

[0010] Therefore, in order to overcome this problem, a method of welding using a metal pad made of nickel or the like as a connecting member has been conventionally applied.

[0011] FIG. 1 is a perspective view showing a battery pack in which electrode leads and a protection circuit module are welded with metal pads according to the prior art, and FIG. 2 is a perspective view showing a battery pack in which the metal pads are bent after the electrode leads and a protection circuit module are welded with the prior art.

[0012] Referring to Figures 1 and 2, a method of joining an electrode lead and a protection circuit module in a conventional battery pack will be described. First, a metal pad 3 is soldered to a surface copper foil layer of a PCB (Printed Circuit Board), which is the substrate of the protection circuit module 2. Then, an electrode lead 1 is further welded to the metal pad, and the metal pad 3 is bent to join the electrode lead 1 and the protection circuit module 2.

[0013] However, this method has the problem that the use of metal pads makes the process complicated and increases the manufacturing cost. Summary of the Invention [Problem to be solved by the invention]

[0014] In order to solve the above problems, an object of the present invention is to provide a battery pack in which a substrate of a protection circuit module and an electrode lead are directly joined using a continuous wave laser welding method. [Means for solving the problem]

[0015] To achieve the above object, a battery pack according to the present invention includes a battery cell including a pair of electrode leads consisting of a positive electrode lead and a negative electrode lead, a pack housing that houses the battery cell, and a protection circuit module in which a protection circuit that controls the operation of the battery cell is formed on a PCB, and is characterized in that the electrode leads are directly joined to a surface copper foil layer of the PCB by laser welding.

[0016] Also, the battery pack according to the present invention is characterized in that the battery cells are pouch-type battery cells.

[0017] In addition, the battery pack according to the present invention is characterized in that the PCB is a double-sided PCB in which a prepreg layer is located between two copper foil layers.

[0018] In addition, the battery pack according to the present invention is characterized in that the PCB is a multi-layer PCB in which copper foil layers and prepreg layers are alternately laminated.

[0019] In addition, the battery pack according to the present invention is characterized in that the laser welding is a continuous wave type laser welding.

[0020] In addition, the battery pack according to the present invention is characterized in that the laser welding is a continuous wave type laser welding using a fiber laser.

[0021] In addition, the battery pack according to the present invention is characterized in that the positive electrode lead is made of any one of aluminum, aluminum alloy, copper, copper alloy, nickel, and nickel alloy.

[0022] In addition, the battery pack according to the present invention is characterized in that the negative electrode lead is made of any one of copper, copper alloy, nickel, and nickel alloy.

[0023] The battery pack according to the present invention is characterized in that the positive electrode lead is made of aluminum or an aluminum alloy.

[0024] A device according to the invention is also characterized in that it includes a battery pack according to the invention.

[0025] The device according to the present invention is characterized in that it is any one of a mobile phone, a portable computer, or a tablet PC. [Effects of the Invention]

[0026] The battery pack of the present invention has the advantage of simplifying the manufacturing process of the battery pack by directly welding the electrode leads to the copper foil layer of the PCB of the protection circuit module without using a separate connecting member such as a metal pad.

[0027] Furthermore, the battery pack of the present invention has the advantage of simplifying the manufacturing process and reducing manufacturing costs because it does not require a separate connecting member. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a perspective view showing a battery pack in a state where electrode leads and a protection circuit module according to the prior art are welded together using metal pads. [Figure 2] FIG. 1 is a perspective view showing a battery pack in which the electrode leads and the protection circuit module are welded together and the metal pads are bent. [Figure 3] 1 is a perspective view showing a battery pack in which electrode leads and a protection circuit module are directly welded together according to an embodiment of the present invention; [Figure 4] 4 is a cross-sectional view showing a cross section of a portion where an electrode lead and a protection circuit module are welded together according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0029] In this application, the terms "comprises," "has," or "has" are intended to specify the presence of features, numbers, steps, components, parts, or combinations thereof described in the specification, but should be understood as not precluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0030] Furthermore, 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 a direct connection but also an indirect connection via another element therebetween. Furthermore, unless otherwise specified, "including a certain element" does not mean that other elements are excluded, but that other elements may also be included.

[0031] Hereinafter, a battery pack according to the present invention will be described with reference to the accompanying drawings.

[0032] FIG. 3 is a perspective view showing a battery pack in which an electrode lead and a protection circuit module are directly welded together according to an embodiment of the present invention, and FIG. 4 is a cross-sectional view showing the welded portion of an electrode lead and a protection circuit module according to an embodiment of the present invention.

[0033] Referring to FIGS. 3 and 4, the battery pack 1000 of the present invention will be described. The battery pack 1000 of the present invention includes a battery cell, a protection circuit module, and a pack housing 300.

[0034] First, the battery cell includes an electrode assembly, a case for accommodating the electrode assembly, and a pair of electrode leads 110, 120 consisting of a positive electrode lead and a negative electrode lead. In particular, the battery cell of the present invention is preferably a pouch-type battery cell.

[0035] Here, the electrode assembly may be a jelly roll type assembly in which a separator is interposed between long sheet-shaped positive and negative electrodes and then wound up, a stack type assembly in which rectangular positive and negative electrodes are stacked with a separator sandwiched between them, a stack folding type assembly in which unit cells are wound up with a long separator film, or a lamination stack type assembly in which battery cells are stacked with a separator sandwiched between them and attached to each other, but is not limited to these.

[0036] In addition to the commonly used liquid electrolyte, it goes without saying that the electrolyte may be replaced with a solid electrolyte or a gel-like quasi-solid electrolyte having an intermediate form between a liquid and a solid by adding an additive to the solid electrolyte.

[0037] The electrode assembly is housed in a battery case, which is typically constructed with an inner layer / metal layer / outer layer laminate sheet structure. The inner layer is in direct contact with the electrode assembly and must therefore be insulating and electrolyte-resistant. Furthermore, the inner layers must have excellent sealing properties, i.e., excellent thermal adhesive strength at the sealing portions where the inner layers are thermally bonded together, to seal the electrode assembly from the outside.

[0038] The material for such an inner layer may be selected from polyolefin resins such as polypropylene, polyethylene, polyethylene acetate, and polybutylene, which have excellent chemical resistance and sealing properties, polyurethane resins, and polyimide resins, but is not limited to these. Polypropylene, which has excellent mechanical properties such as tensile strength, rigidity, surface hardness, and impact resistance, and excellent chemical resistance, is most preferred.

[0039] The metal layer in contact with the internal layer corresponds to a barrier layer that prevents moisture and various gases from penetrating into the battery from the outside, and a suitable material for such a metal layer is an aluminum thin film, which is lightweight yet has excellent formability.

[0040] An outer layer is provided on the other side of the metal layer, and the outer layer may be made of a heat-resistant polymer having excellent tensile strength, moisture barrier properties, and air barrier properties to protect the electrode assembly and ensure heat resistance and chemical resistance, such as, but not limited to, nylon or polyethylene terephthalate.

[0041] Meanwhile, the pair of electrode leads 110 and 120 consists of a positive electrode lead and a negative electrode lead, and may be exposed to the outside of the battery case after the positive electrode tab and the negative electrode tab of the electrode assembly are electrically connected, respectively, or may be directly connected to the electrode assembly without tabs.

[0042] The electrode leads 110 and 120 are generally made of metal materials with excellent electrical conductivity. For example, the positive electrode lead is preferably made of aluminum, copper, nickel, stainless steel, or an alloy thereof, and the negative electrode lead is preferably made of copper, nickel, stainless steel, or an alloy thereof, but is not limited to these.

[0043] Next, the protection circuit module is configured to have a form in which various elements for protecting the battery cells from abnormal conditions such as overcharging and overcurrent are mounted on a PCB (Printed circuit board) 200 to form a protection circuit.

[0044] PCBs come in various forms depending on the laminate structure, which can be roughly classified into single-sided PCBs, which are made up of a single layer of copper foil and a single layer of prepreg laminated together, double-sided PCBs, which have a prepreg layer 220 between copper foil layers 210 on both surfaces, and multi-layer PCBs, which have copper foil layers and prepreg layers laminated alternately.

[0045] That is, the PCB 200 has a structure in which at least one copper foil layer 210 is formed on the surface, and in order to electrically connect the protection circuit module and the electrode leads 110, 120, a process of joining the copper foil layer 210 of the PCB 200 to the electrode leads 110, 120 is required.

[0046] Meanwhile, although FIG. 4 shows the PCB 200 as being a double-sided PCB, the present invention is not limited to this and various other PCBs may be used.

[0047] The battery pack 1000 of the present invention can directly weld the copper foil layer 210 of the PCB 200 and the electrode leads 110, 120 by applying a laser welding method, particularly a continuous wave laser welding method, without using a connecting member such as a metal pad.

[0048] Here, the continuous wave laser welding method is a welding method using a laser that continuously generates laser light, unlike pulse wave laser welding.

[0049] Typical continuous wave lasers are CO2 lasers and fiber lasers that use optical fibers. CO2 lasers emit infrared light at 10.6 μm and are highly efficient, making it easy to obtain high output.

[0050] Compared to the Nd:YAG laser, which is mainly used in pulsed wave laser welding, this continuous wave laser has the advantage of being able to weld dissimilar metals such as Al and Cu, which have a small beam size and high energy density, and has low absorption, so it is possible to directly weld the electrode lead and the copper foil layer 210 of the PCB 200 without a separate connecting member such as a metal pad.

[0051] In particular, fiber lasers can easily produce high-power lasers of several kW by amplifying light of a specific wavelength using optical fibers, and also have the advantage of consuming less power than existing lasers.

[0052] Meanwhile, the pack housing 300 accommodates the battery cells and protects them from external impacts, and may be made of various shapes and materials depending on the application of the battery pack 1000.

[0053] Next, to briefly explain a method for manufacturing a battery pack of the present invention, first, a pouch-type battery cell including a pair of electrode leads 110, 120 is manufactured, and then, in a separate process, various components for protecting the battery cell are mounted on PCB 200 to manufacture a protection circuit module.

[0054] Next, the electrode leads 110, 120 and the copper foil layer 210 of the PCB 200 are directly joined by continuous wave laser welding, and then the assembly is housed in the pack housing 300, followed by packaging, to manufacture the battery pack 1000.

[0055] Alternatively, after the battery cell is housed in the pack housing 300, the electrode leads 110, 120 and the copper foil layer 210 of the PCB 200 can be welded together.

[0056] The battery pack 1000 manufactured in this manner can be used as a power source for various devices.

[0057] In particular, the battery pack 1000 of the present invention can be used in devices such as, but not limited to, a mobile phone, a portable computer, or a tablet PC.

[0058] Although specific portions of the contents of the present invention have been described in detail above, it will be apparent to those skilled in the art that such specific techniques are merely preferred embodiments and do not limit the scope of the present invention. It is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of the present invention, and it goes without saying that such changes and modifications also fall within the scope of the accompanying claims. [Explanation of symbols]

[0059] 1000 battery pack 110, 120 electrode leads 200 PCB 210 Copper foil layer 220 prepreg layers 300 pack housing

Claims

1. A method for manufacturing a battery pack (1000), comprising: The battery pack (1000) a battery cell including a pair of electrode leads (110, 120) consisting of a positive electrode lead and a negative electrode lead; a pack housing (300) that houses the battery cells; a protection circuit module on a PCB (200) that controls the operation of the battery cell; Including, The PCB (200) is a multi-layer PCB (200) in which copper foil layers (210) and prepreg layers (220) are alternately laminated and a copper foil layer is formed on the surface, the positive electrode lead is made of any one of aluminum, an aluminum alloy, nickel, and a nickel alloy; the negative electrode lead is made of one of nickel and a nickel alloy; After the battery cell is housed in the pack housing, the electrode leads (110, 120) are directly joined to the surface copper foil layer (210) of the PCB (200) by laser welding; The method for manufacturing a battery pack (1000), wherein the laser welding is continuous wave laser welding using a fiber laser.

2. The method for manufacturing a battery pack (1000) according to claim 1, wherein the battery cells are pouch-type battery cells.

3. The method for manufacturing a battery pack (1000) according to claim 1, wherein the positive electrode lead is made of aluminum or an aluminum alloy.

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