An apparatus and method for copper foil residual stress release

Abstract

The present application relates to the field of electrolytic copper foil manufacturing method, and discloses a kind of equipment and method for copper foil residual stress release, the annealing furnace of the equipment of the present application adopts integral structure, and is divided into preheating, soaking and cooling three regions, adopts the heating mode of combination of heat conduction, heat radiation and heat convection, guarantees the continuity of heating and cooling, so that copper foil is heated more evenly, guarantees the stability of heating speed and sufficient heating time, reduces the residual stress of copper foil, stabilizes the size of copper foil, reduces the deformation and crack tendency of copper foil, can obtain the copper foil of uniform fine recrystallization structure, guarantees the warping degree of copper foil, through automatic feeding and discharging, copper foil is promptly packaged, and the processing effect is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of electrolytic copper foil manufacturing methods, and more specifically to an apparatus and method for releasing residual stress in copper foil. Background Technology

[0002] Electrolytic copper foil is one of the essential basic materials in the electronics industry and is widely used. With the rapid development of the electric vehicle industry, the demand for copper foil as a special material for the negative electrode of new energy power lithium batteries is increasing, and the requirements for its quality are also becoming more and more stringent. Since the heat treatment process directly affects the quality of copper foil products, the annealing process is particularly important in the preparation of copper foil.

[0003] Chinese patent CN111793779 B discloses a stress-relief annealing process and verification method for reducing the warpage of 4.5-micron copper foil, comprising three steps: (1) heating: placing the 4.5-micron copper foil in an annealing furnace and heating it to 80°C within 3 hours; (2) heat preservation: keeping the 4.5-micron copper foil in the annealing furnace for 4 hours; (3) slow cooling: slowly cooling the 4.5-micron copper foil in the furnace for 2 hours and then taking it out. Chinese Patent CN 215251101 U discloses a heat treatment device for electrolytic copper foil, comprising a housing, a controller, and a heating mechanism. The heating mechanism is disposed within the housing and connected to the controller. The device is characterized in that: the heating mechanism is installed at the lower part of the housing; a support frame is provided within the housing, and several copper foil roll placement positions are provided on the support frame, supporting each copper foil roll to provide a space for heat diffusion between the copper foil roll and the heating mechanism; a double sliding cover with an upper and lower structure is provided at the top of the housing, allowing the upper or lower cover to overlap and expose an opening for suspending the copper foil rolls. The controller provides power to the heating mechanism and controls the temperature using a temperature control instrument. When the heating temperature reaches a certain level, the power is automatically cut off, maintaining the processing temperature inside the housing between 80-120℃. According to the two published patents mentioned above, the annealing process of copper foil: using a bell-type annealing furnace cannot guarantee the uniformity and stability of the annealing performance of the soft finished product, and it is difficult to obtain a uniform and fine recrystallized crystal structure. At present, the bell-type annealing furnace cannot effectively solve the problem of scratches on the surface of copper foil. In the prior art, when annealing copper foil, the warpage of lithium battery copper foil often does not reach the ideal range due to the difference in baking time and baking temperature. At the same time, the surface of lithium battery copper foil is not packaged before processing, which affects the baking effect. Summary of the Invention

[0004] This invention provides a chain annealing equipment and method for releasing residual stress in copper foil, which reduces residual stress in copper foil, avoids unsatisfactory warping of copper foil caused by uneven heating, prevents scratches on the surface of copper foil, stabilizes copper foil dimensions, reduces deformation and cracking tendency, and can obtain copper foil with uniform and fine recrystallized structure.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a chain annealing equipment for releasing residual stress in copper foil, comprising a transmission device, an annealing furnace, and a loading and unloading device. The annealing furnace is an integral structure, with three zones arranged sequentially inside: preheating, homogenization, and cooling. A heating device is provided inside the annealing furnace.

[0006] Preferably, the heat transfer method of the heating device is one or more of the following: heat conduction, heat radiation and heat convection.

[0007] Preferably, the homogenization zone inside the annealing furnace is equipped with a heat circulation system and a fan to ensure uniform temperature inside the furnace.

[0008] Preferably, the annealing furnace adopts a tunnel-type far-infrared radiation drying structure.

[0009] Preferably, the heating tube of the tunnel-type far-infrared radiation drying structure is a far-infrared radiation heating tube with a gold-plated reflective layer on the back of a quartz tube, and the heating tube is evenly distributed in the upper and lower parts of the annealing furnace.

[0010] Preferably, the transmission device includes a conveyor belt and a support at the feed end of the conveyor belt, and a slot for holding a take-up roller for holding copper foil is provided on the upper part of the support.

[0011] Preferably, the loading and unloading device is an AGV trolley, which can automatically place the winding roller of the copper foil into the slot on the bracket, and can automatically wind up the annealed copper foil.

[0012] Preferably, the loading and unloading areas of the AGV trolley and the connection points of the transmission device are equipped with protective covers.

[0013] Preferably, the annealing furnace is equipped with a suction hood in the foil feeding section, the exhaust pipe of the suction hood is located outside the factory building, and the suction hood is equipped with an independent motor.

[0014] Preferably, the upper and lower parts of the foil exit section of the annealing furnace are provided with air knives for cooling and drying the copper foil, and the air knives are equipped with independent motors.

[0015] Preferably, a safety interlock device is provided on the mechanical equipment of the equipment.

[0016] Preferably, temperature sensors are installed in the three zones inside the annealing furnace: preheating, homogenization, and cooling.

[0017] The present invention also provides a method for releasing residual stress in copper foil, wherein the copper foil is automatically fed and continuously passes through three stages: preheating, homogenization and cooling, and the copper foil is automatically unloaded and wound up after heat treatment.

[0018] The present invention has the following beneficial effects:

[0019] This invention provides equipment and a method for releasing residual stress in copper foil. The equipment and method employ temperature-zoned heating of the copper foil, dividing it into a preheating zone, a homogenizing zone, and a cooling zone. The heating method combines heat conduction, heat radiation, and heat convection to ensure continuous heating and cooling, resulting in more uniform heating of the copper foil during annealing. This ensures stable heating rate and sufficient heating time, reduces residual stress in the copper foil, stabilizes its dimensions, and reduces deformation and cracking tendency. The resulting copper foil exhibits a uniform and fine recrystallized structure. A temperature sensor in the annealing furnace monitors the temperature in real time to prevent overheating. An alarm automatically sounds when the temperature exceeds a set threshold. The invention also utilizes AGV (Automated Guided Vehicle) trolleys for automatic loading and unloading, automating and promptly winding up the annealed copper foil to ensure optimal baking results. Attached Figure Description

[0020] Figure 1 This is a front view of the equipment for residual stress relief of copper foil according to the present invention.

[0021] Figure 2 This is a side view of the equipment for residual stress relief of copper foil according to the present invention.

[0022] Figure 3 This is a graph showing the temperature change of copper foil in an annealing furnace over time in an embodiment of the present invention.

[0023] In the diagram: 1. AGV trolley; 2. Support frame; 3. Winding roller; 4. Copper foil; 5. Temperature sensor; 6. Alarm; 7. Heating tube; 8. Annealing furnace; 9. Conveyor belt; 10. Fan. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings. The present invention provides a technical solution: a chain-type annealing apparatus for releasing residual stress in copper foil, such as... Figure 1As shown, the system includes a transmission device, an annealing furnace 8, and a loading and unloading device. The annealing furnace 8 is an integral structure, with a preheating zone, a homogenizing zone, and a cooling zone arranged sequentially inside. A heating device is installed inside the annealing furnace 8. The heat transfer method of the heating device is one or more of heat conduction, heat radiation, and heat convection. The advantage of heat conduction is its high efficiency, but the disadvantage is that it may cause uneven heating of the copper foil 4 and local overheating. Heat radiation requires adjusting the distance between the heat source and the workpiece to improve heat treatment efficiency. If the heat source is too far from the workpiece, the heat transfer efficiency may be low. The advantage of heat convection is that it can improve efficiency, accelerate the rate of heat conduction, and provide uniform heating temperature, avoiding local overheating. The disadvantage is that heat may be lost due to airflow, increasing energy waste and consumption. In actual heating, a combination of heat transfer methods is preferred, such as heat conduction + heat radiation, or heat conduction + heat convection, to improve heating efficiency. To improve the heat treatment efficiency of the copper foil 4, the winding roller 3 of the copper foil 4 can also be used as a heating source, and the heating efficiency can be improved by combining radiation and conduction.

[0025] The annealing furnace 8 has a preheating zone, a soaking zone, and a cooling zone arranged sequentially inside. The preheating zone is adjacent to the soaking zone. The highest temperature reached by the preheating zone is the holding temperature set by the soaking zone. When the copper foil 4 is preheated to the holding temperature set by the soaking zone, the copper foil 4 just enters the soaking zone for holding. When the holding time of the copper foil 4 in the soaking zone meets the requirements, the copper foil 4 just enters the cooling zone for cooling. First, the highest temperature to be heated in the soaking zone is set. The preheating zone is the growth area where the copper foil 4 is heated from room temperature to the holding temperature set by the soaking zone. According to the length of the preheating zone, the heating rate and transmission speed are controlled to ensure that the copper foil 4 enters the soaking zone for holding just as it is heated to the highest temperature set by the soaking zone in the preheating zone. The holding time of the copper foil 4 in the soaking zone is controlled by controlling the transmission speed. The heating and cooling rates of the preheating zone and the cooling zone are determined according to the transmission speed. The copper foil 4 is held at a certain temperature in the soaking zone for several hours. Finally, the copper foil 4 is annealed and cooled in the furnace cooling zone.

[0026] The annealing furnace 8 requires good heat preservation to ensure stable temperature inside the furnace. In this embodiment, a tunnel-type far-infrared radiation drying structure is adopted inside the furnace. The heating tubes 7 are far-infrared radiation heating tubes with a gold-plated reflective layer on the back. Each heating tube 7 has a power of 3 kW, and 18 tubes are arranged at the top and bottom inside the annealing furnace 8. The heating tubes 7 provide both heat conduction and heat radiation heating functions. According to the actual heating needs, each heating tube can be independently switched on and off to meet different heating rate requirements. A fan and a heat circulation system are also set in the heat spreader zone inside the annealing furnace 8 to enhance heat convection inside the annealing furnace 8, make the temperature inside the chamber uniform, and avoid local overheating, which would lead to poor annealing performance of copper foil 4. Temperature sensors 5 are respectively set in the preheating zone, heat spreader zone and cooling zone inside the annealing furnace 8. The temperature sensors 5 are all connected to an external alarm 6. When the temperature inside the chamber exceeds the set threshold, the alarm 6 will automatically sound an alarm. The real-time monitoring of the temperature sensors 5 also prevents the copper foil 4 from being overheated.

[0027] The transmission device includes a conveyor belt 9 and a support 2 at the feed end of the conveyor belt 9. A slot for holding the winding roller 3 of copper foil 4 is provided on the upper part of the support 2. The loading and unloading device is an AGV trolley 1. The AGV trolley 1 automatically puts the winding roller 3 of copper foil 4 into the slot on the support 2. The copper foil 4 is conveyed into the annealing furnace 8 by the conveyor belt 9 for annealing treatment. It is also unloaded at the discharge port of the annealing furnace 8 by the AGV trolley 1. The AGV trolley 1 can automatically wind up the annealed copper foil 4. The loading and unloading of the AGV trolley 1 realizes automated production. A protective cover is provided at the connection between the loading and unloading position of the AGV trolley 1 and the transmission device. At the same time, a safety interlock device is installed on the mechanical equipment to protect the operators. The machine can only operate normally when the safety interlock device is activated.

[0028] A fan 10 is installed in the foil inlet section 8 of the annealing furnace, such as Figure 2 As shown, the blower 10 can discharge water vapor to the outside of the factory through the pipe via the suction hood. An air knife is installed in the foil outlet section of the annealing furnace 8 to cool and dry the copper foil 4. The blower 10 and the air knife are each equipped with an independent motor.

[0029] The present invention also provides a method for releasing residual stress in copper foil. The copper foil 4 is automatically fed by an AGV trolley 1. The length of the annealing furnace and the required annealing time of the copper foil 4 are controlled by adjusting the transmission speed of the transmission device and the heating rate of the annealing furnace, so that the copper foil 4 passes through the preheating zone, the homogenizing zone and the cooling zone in sequence. The copper foil 4 is automatically unloaded and wound up by the AGV trolley to ensure the baking effect.

[0030] A specific embodiment of the method for relieving residual stress in copper foil is as follows:

[0031] First, copper foil 4 is automatically fed by AGV trolley 1, with the winding roller 3 of copper foil 4 placed on the support 2 of conveyor belt 9. Conveyor belt 9 then feeds copper foil 4 into annealing furnace 8. Annealing furnace 8 has a preheating zone length of 1m, a homogenizing zone length of 5m, and a cooling zone length of 2m. The homogenizing zone holding temperature of annealing furnace 8 is set to 65℃. The total length of the annealing furnace is 8m, ensuring the entire annealing time for copper foil 4 is 8 hours. Therefore, the conveyor belt 9 speed is set to 1m / h. The ambient temperature is 25℃, so the preheating zone heating rate is set to 40℃ / h, and the cooling rate is -20℃ / h. This allows copper foil 4 to undergo three stages: preheating, homogenizing, and cooling. The temperature change of copper foil 4 in the annealing furnace over time is shown in the figure below. Figure 3 As shown, the copper foil 4 that has undergone heat treatment is automatically unloaded and wound by the AGV trolley 1, thus realizing an automated production line. Finally, X-ray diffraction was used to analyze the copper foil 4 before and after annealing. The annealing treatment had little impact on the microstructure of the copper foil 4. The grain size of the copper foil 4 sample increased, and the size uniformity decreased.

[0032] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be construed that the specific implementation of the present invention is limited to these descriptions. It should be understood that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

Claims

1. A chain annealing apparatus for residual stress release of copper foil, characterized by, The chain annealing equipment comprises a transmission device, an annealing furnace and an up-and-down feeding device, the annealing furnace is of an integral structure, the annealing furnace adopts a tunnel type far infrared radiation drying structure, three areas of preheating, heat soaking and cooling are sequentially and continuously arranged inside, the annealing furnace is provided with a heating device inside, the heating pipe of the tunnel type far infrared radiation drying structure adopts a far infrared radiation heating pipe with a gold-plated reflecting layer on the back of a quartz pipe, the heat transfer mode of the heating device is a combination of heat conduction, heat radiation and heat convection, the heat soaking area inside the annealing furnace is provided with a heat circulation system and a fan for making the temperature in the furnace uniform, the feeding end of the transmission device is provided with a winding roller for feeding by an AGV trolley, and the winding roller serves as a heating source.

2. The chain annealing apparatus for residual stress release of copper foil according to claim 1, characterized by, The heating pipes are arranged on the upper and lower parts of the annealing furnace.

3. The chain annealing apparatus for residual stress release of copper foil according to claim 1, characterized by, The transmission device comprises a conveying belt, and the feeding end of the conveying belt is provided with a support, and the upper part of the support is provided with a clamping groove of a winding roller for clamping copper foil.

4. The chain annealing apparatus for residual stress release of copper foil according to claim 3, characterized by, The up-and-down feeding device is an AGV trolley, the AGV trolley can automatically place the winding roller of the copper foil into the clamping groove on the support, and the AGV trolley can automatically wind the copper foil after annealing treatment.

5. The chain annealing apparatus for residual stress release of copper foil according to claim 4, characterized by, The area of the AGV trolley for feeding and discharging and the connection part of the transmission device are provided with a protective cover.

6. The chain annealing apparatus for residual stress release of copper foil according to claim 1, wherein, The annealing furnace is provided with a suction hood at the copper foil feeding section, the exhaust pipe of the suction hood is arranged outside the factory building, and the suction hood is provided with an independent motor.

7. The chain annealing apparatus for residual stress release of copper foil according to claim 1, characterized by, The upper and lower parts of the copper foil discharging section of the annealing furnace are provided with air knives for blowing and drying the copper foil, and the air knives are provided with independent motors.

8. The chain annealing apparatus for residual stress release of copper foil according to claim 1, characterized by, A safety interlocking device is arranged on the mechanical equipment.

9. The chain annealing apparatus for residual stress release of copper foil according to claim 1, characterized by, Temperature sensors are arranged in the preheating, heat soaking and cooling areas inside the annealing furnace.

10. A method for residual stress release of copper foil, characterized by, The chain annealing equipment is used for annealing, and the steps are as follows: automatically feeding the copper foil, making the copper foil sequentially and continuously pass through the preheating, heat soaking and cooling stages, and automatically discharging and winding the copper foil after heat treatment.

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