Processing method of composite conductor based on polymeric membrane

Abstract

The invention relates to a processing method of a composite conductor based on a polymeric membrane, which comprises the following steps of: 1, bombarding a target material by using a pulsed electron beam gun, and depositing on a first surface of a base material to form a first conductive layer; 2, on the second face of the base layer material, part of the base layer material is removed through laser, and a plurality of micro blind holes are formed; 3, bombarding the target material by using a plurality of pulse electron beam guns, and depositing on the second surface of the base layer material to form a second conductive layer; 4, conducting the first conductive layer and the second conductive layer at the micro blind hole; the base material is divided into a tab part and a base material part in the width direction, and the thickness of the conductive layer at the tab part is greater than that of the base material part. Due to the adoption of the pulsed electron beam deposition technology in the field of semiconductors, the thickness of the conducting layer can be regulated and controlled at will, the tab part can be formed at a time, traditional production methods of evaporation, electroplating, sputtering and mixing of evaporation, electroplating and sputtering can be completely replaced, and the method has the advantages of high production efficiency, cost reduction, energy conservation, environmental protection and the like.

Description

Technical Field

[0001] The invention relates to a processing method based on a polymer film composite conductor. Background Art

[0002] Compared with ultra-thinning and surface modification, the composite current collector has been innovated at the material level, adopting a "sandwich" structure. The middle layer is a polymer organic film, and the upper and lower layers are copper / aluminum metal. Taking composite copper foil as an example, lithium battery composite copper foil is used as the negative electrode current collector of lithium batteries, which has a "polymer substrate + thin conductive layer (copper)" structure.

[0003] After the existing composite current collector is processed, it is still necessary to weld the pole ears. The reason is that the existing composite current collector production process cannot form the pole ears in one go. The following is an introduction to the processes currently used by leading companies in this field.

[0004] Judging from the plans of composite current collector material manufacturers, most manufacturers represented by Baoming Technology adopt the two-step process of "magnetron sputtering + water electroplating", Jinmei New Materials adopts the three-step process of "magnetron sputtering + evaporation + water electroplating", Putailai adopts a unique bonding process, and Nord shares cooperates with Dawson shares to adopt a one-step dry process.

[0005] One-step method (wet method): First, the base film is cleaned, roughened and other surface treatments are carried out, and then the copper layer is covered on the surface of the base film by chemical deposition (chemical plating). The advantage is that the film after the roughening treatment has a fast coating formation speed and a uniform coating, which can increase the adhesion of the coating and withstand the high current during the electroplating process. The disadvantage is that it is necessary to select precious metals as catalysts, the equipment is expensive, the cost is high (the value of the solution is 2.0-2.5 yuan per square meter), and the base film is required to have good high temperature resistance.

[0006] One-step method (dry method): Copper is plated through a vacuum magnetron sputtering machine or a vacuum magnetron sputtering evaporation machine, and efficiency is improved through multiple chambers and multiple targets. The advantages are simple operation, low labor cost, and high yield rate. The disadvantages are high equipment price, high technical requirements, low efficiency (magnetron sputtering single coating thickness is nanometer level, and multiple sputtering is required to reach micrometer level, and the efficiency is lower than electroplating), high temperature, difficult to control thermal deformation of the base film, and poor coating uniformity.

[0007] Two-step method: "magnetron sputtering + water electroplating", first use high-energy argon atoms to ionize and then impact the target material, sputter copper ions to deposit on the base film to form a copper seed layer with a thickness of about 30-80nm, improve the conductivity of the polymer material, and then use water electroplating to thicken the copper layer to about 1μm to achieve better conductivity. The advantages are improved efficiency and relatively low equipment cost. The disadvantages are low yield rate, poor coating uniformity compared to the one-step method, difficult control, and high environmental pressure.

[0008] Three-step method: "magnetron sputtering + evaporation + water electroplating", that is, adding evaporation process as a transition after magnetron sputtering step, to increase deposition rate, thicken copper layer, and reduce the difficulty of electroplating in the latter half. The advantage is that the rate of electroplating part is increased and production efficiency is the highest. The disadvantage is that the process is complicated and not conducive to control. The high temperature environment of vacuum evaporation process can easily cause perforation of polymer base film, the yield rate is not high, and the environmental pressure is high. In addition, the evaporation process requires regular cleaning of equipment, and the maintenance cost is high.

[0009] Putailai bonding method: The rolled copper foil is laminated on both sides of the substrate with adhesive, and then the copper foil is thinned to the required thickness with an alkaline solution. According to Putailai's announcement, the investment amount of the 16,000-ton composite copper foil project is 2 billion yuan, corresponding to an investment of about 2.9 yuan per square meter, which is lower than the equipment investment of the two-step method and the three-step method. The disadvantage is that the process is in its early stages and is not yet mature. Summary of the invention

[0010] In view of the above situation, it is necessary to provide a method for processing a polymer film composite conductor that solves at least one of the above problems.

[0011] A processing method based on a polymer film composite conductor comprises the following steps:

[0012] Step 1, using a plurality of pulsed electron beam guns to bombard the target material to generate a plasma plume, wherein the plasma plume flows toward the first surface of the base material, and is deposited on the first surface of the base material to form a first conductive layer;

[0013] Step 2: On the second side of the base material, use a laser to peel off the base material to form a plurality of micro blind holes, wherein the depth of the micro blind holes is not less than the thickness of the base material;

[0014] Step 3, using a plurality of pulsed electron beam guns to bombard the target material to generate a plasma plume, wherein the plasma plume flows toward the second surface of the base material, and is deposited on the second surface of the base material to form a second conductive layer;

[0015] Step 4: at the micro blind hole, the coating on the second surface of the base material penetrates into the micro blind hole to make the first conductive layer and the second conductive layer conductive;

[0016] The base material is divided into a pole ear portion and a base material portion in the width direction, and the thickness of the conductive layer of the pole ear portion is greater than that of the conductive layer of the base material portion.

[0017] As a further solution of the present invention: the plurality of pulse electron beam guns are divided into two groups, the pulse electron beam guns in the first group are used to form the conductive layer of the pole ear portion, and the pulse electron beam guns in the second group are used to form the conductive layer of the substrate portion.

[0018] As a further solution of the present invention: the number of the pulsed electron beam guns in the first group is greater than that of the pulsed electron beam guns in the second group.

[0019] As a further solution of the present invention: the output power of the first group of pulsed electron beam guns is greater than that of the second group of pulsed electron beam guns.

[0020] As a further solution of the present invention: the micro blind hole is located at the pole ear portion.

[0021] As a further solution of the present invention: the pulse frequency of the pulse electron beam guns of the first group is 5≤X≤200; the pulse frequency of the pulse electron beam guns of the second group is 5≤X≤200.

[0022] As a further solution of the present invention: the wavelength of the laser for stripping the base material is 192nm≤X≤1064nm, the pulse width of the laser is 1fs≤X≤1ns, and the laser power is 0.001J / cm^2≤X≤10J / cm^2.

[0023] As a further solution of the present invention: the thickness of the conductive layer on the pole ear is H1, the thickness of the conductive layer deposited on the substrate is H2, the ratio of H1 to H2 is X, and 1<X<5.

[0024] As a further solution of the present invention: there are at least two targets for depositing the first conductive layer or the second conductive layer, and the materials of the different targets are different.

[0025] The above processing method based on polymer film composite conductor adopts the pulse electron beam deposition technology in the semiconductor field to achieve arbitrary control of the thickness of the conductive layer and can form the pole ear part in one go. It can completely replace the traditional production methods of evaporation, electroplating, sputtering and their mixtures, and has the advantages of high production efficiency, saving and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart of an embodiment of the present invention;

[0027] Figure 2 is a simplified structural diagram of the pulse electron deposition equipment used in Example 1;

[0028] Figure 3 is a simplified structural diagram of the pulse electron deposition equipment used in Example 2;

[0029] Figure 4 It is a schematic diagram of the deposition scheme of the composite current collector ear. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0031] In the description of the present invention, unless otherwise specified, "multiple" means two or more; the terms "center", "longitudinal", "lateral", "up", "down", "left", "right", "inside", "outside", "front end", "rear end", "head", "tail", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third" and the like are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0032] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0033] The present invention provides a processing method based on a polymer film composite conductor, such as Figure 1 As shown, the following steps are included:

[0034] S100, installing a rolled polymer base material on a reel-up and reel-down mechanism of a pulse electron beam deposition device, so that the base material moves at a certain speed in the pulse electron beam deposition device;

[0035] Regarding pulsed electron beam deposition technology, it is often used in the semiconductor field.

[0036] S200, using the pulse electron beam gun array on the pulse electron beam deposition equipment to bombard the target material, vaporize the target material and generate a plasma plume, the plasma sub-plume flows to the base material, and deposits the first conductive layer on the first surface of the base material. Wherein, the two sides of the unwinding direction of the base material are defined as the pole ear parts, and the middle is defined as the base part, and the thickness of the conductive layer of the pole ear part is greater than that of the conductive layer of the base part. If the base material does not move, the coating deposited on the base material by a single pulse electron beam gun is circular, and the thickness is Gaussian distribution; based on the movement of the base material, the conductive layer deposited by a single pulse electron beam gun is strip-shaped, and its cross section (perpendicular to the moving direction of the base material) is Gaussian distribution. Use a number of pulse electron beam guns arranged side by side, control the spacing or output power between each pulse electron beam gun, that is, a uniform conductive layer can be deposited on the base material.

[0037] S300, on the second side of the base material, that is, the side that has not yet been coated with a conductive layer, a laser scanning galvanometer is used to punch holes in the ear portion to produce a number of micro blind holes. The punching process can also be understood as scraping the base material, also known as laser milling (LASER Milling), the purpose of which is to remove the polymer material at the predetermined position and expose the side of the first conductive layer that is in contact with the base material, as a basis for conduction with the second conductive layer (the conductive layer on the other side of the base material). In this embodiment, taking the base material as PET and the conductive layer as copper as an example, the effect to be achieved is to peel off the PET material without affecting the conductive layer material, so it is necessary to make a choice on the wavelength of the laser, and use the different absorption rates of different materials to the same wavelength laser to achieve the effect of surface material stripping (laser milling).

[0038] Under the premise of selecting a laser of a certain wavelength, the difference in the absorption rate of light between PET and copper material reaches the maximum (based on the large reflection of copper and the large absorption of PET), and the PET material can be ablated without damaging the copper metal plating layer, thereby stably generating micro blind holes with the first conductive layer at the bottom. In addition, in this embodiment, it is preferred to use a picosecond laser (10E-12 seconds) or a femtosecond laser (10E-15 seconds), which has a short single pulse output time and high energy, and can further reduce the thermal effect on the conductive layer on the basis of the selected wavelength, thereby improving the quality of the micro blind holes.

[0039] At the same time, a femtosecond laser or picosecond laser is combined with a scanning galvanometer to achieve scanning milling of a fixed area, and continuous laser milling is achieved based on the synchronously reeled and unwound base material.

[0040] The wavelength of the laser for stripping the base material is 192nm≤X≤1064nm, the pulse width of the laser is 1fs≤X≤1ns, the laser power is 0.001J / cm^2≤X≤10J / cm^2, and the pulse overlap range is 5%≤X≤90%.

[0041] S400, after completing the micro blind hole processing on the second side of the base material, the conductive layer is deposited on the second side of the base material. In this step, the specific method is consistent with step S200. Since in step S300, a micro blind hole with the first conductive layer at the bottom is processed, during the deposition of the second conductive layer, the second conductive layer at the micro blind hole will directly contact and conduct with the first conductive layer. Compared with the traditional composite current collector production process that requires additional welding of the pole ear or the conduction of the two conductive layers by edge welding, the process provided in this embodiment deposits conductive layers of different thicknesses (pole ear part and base part) by pulse electron beam deposition on both sides of the base material, combined with the laser forming micro blind hole solution, the pole ear can be formed at one time, greatly improving production efficiency. At the same time, the pulse electron beam deposition process used has many advantages over traditional hybrid processes such as evaporation and electroplating, such as improved efficiency, greatly reduced energy consumption, environmental friendliness, and low equipment maintenance costs.

[0042] Furthermore, compared with evaporation, sputtering or electroplating, the high-energy plasma generated by pulsed electron beam deposition has an impact on the base material, and the ultra-short pulse avoids excessive temperature rise. Therefore, the use of pulsed electron beam deposition for the production of composite current collectors also has the advantages of strong interface bonding and amorphous deposition, forming a more stable coating, making the electrical properties of the composite current collector closer to pure metal foil.

[0043] Furthermore, in the process of depositing the first conductive layer and the second conductive layer, targets of different materials can be used to achieve special properties of the conductive layer. Some targets are made of copper to form a basic copper plating layer, and other alloy materials are used for targets at downstream positions. For example, targets made of copper-nickel alloy are used at the corresponding ear parts to enhance the mechanical strength of the plating at the ear parts and achieve performance improvement during ultrasonic welding. For example, special alloys (using alloy properties, which are not described in detail here) are used to improve conductivity. Based on this solution, the comprehensive performance of the composite current collector can be improved.

[0044] In the first embodiment of the present invention, based on the above foundation, step S200 also includes winding up the material, that is, directly winding up after the first conductive layer is formed by deposition on the first surface. It should be noted that the winding and unwinding process is synchronized with the deposition process. The winding and unwinding process allows the base material to pass through the pulsed electron beam gun module at a uniform speed in the pulsed electron beam deposition device. The pulsed electron beam gun continuously bombards the target material, and the generated plasma plume is also continuously transferred to the base material.

[0045] After the first conductive layer of the base material is deposited and rolled up, the semi-finished roll is taken out from the pulse electron beam deposition device, and laser drilling in step S300 is performed. The laser drilling method is similar to the conductive layer deposition method. During the process of winding and unwinding, the laser drilling device is set on the side without the conductive layer, and the base material is ablated and peeled off to form micro blind holes with the first conductive layer as the base. After the winding is completed, the roll is put into the pulse electron beam deposition device to deposit the second conductive layer on the second surface. The deposition process is the same as the deposition process of the first conductive layer.

[0046] In summary, in the above embodiment, a pulse electron beam deposition device and a laser drilling device are used, and a segmented processing method is adopted to gradually form the conductive layers on both sides of the polymer film material, and finally form a composite current collector material. The advantage of this solution is that the pulse electron beam deposition device used only needs to have the ability of single-sided deposition, so only a pulse electron beam gun array needs to be set in a single-side direction, reducing equipment investment; and it can avoid cross-contamination of the electron beam process chamber and the product caused by the volatilized organic materials due to laser ablation, thereby saving the energy consumption of vacuum maintenance and further reducing product costs.

[0047] Embodiment 2 of the present invention is different from the segmented processing method in embodiment 1. A one-time molding processing method is used to prepare a composite current collector material, which is more efficient than the solution in embodiment 1; that is, the first conductive layer and the second conductive layer are deposited at one time in a pulse electron beam deposition device. It should be noted that between the process of depositing the first conductive layer and the process of depositing the second conductive layer, laser drilling is required on the second surface, that is, a group of pulse electron beam gun arrays need to be set on the opposite sides of the pulse electron beam deposition device, and the pulse electron beam gun array used to deposit the second conductive layer should be set at a position closer to the downstream (according to the winding and unwinding direction of the base material). At the same time, a laser drilling device needs to be set at the upstream position of the pulse electron beam gun array used to deposit the second conductive layer. Compared with embodiment 1, the overall processing steps are consistent, and there is a slight difference in the selection of equipment. Compared with the solution in embodiment 1, this embodiment can process the composite current collector faster, and the efficiency is about twice that of the former, but the equipment investment cost and process operation cost are increased, which is more suitable for areas with higher labor costs.

[0048] As a supplementary explanation, the pulse electron beam deposition equipment mentioned in the above two embodiments includes a vacuum deposition chamber 100, a pulse electron beam gun array 200 (200A, 200B, 210, 220) disposed on the deposition chamber 100, and a laser drilling device 300 disposed on the deposition chamber 100 or separately disposed. Figure 2 and Figure 3As shown, the pulse electron beam gun array can be arranged on a single side of the deposition chamber (for a segmented process) or on the opposite side (for a one-shot process). Furthermore, on the basis of the one-shot process, the laser generator and modulator of the laser drilling equipment are arranged outside the deposition chamber, and the modulated laser is introduced into the scanning galvanometer in the cavity by an optical fiber to perform drilling (laser milling) processing on the base material inside the deposition chamber.

[0049] Furthermore, whether a segmented or one-time forming process is used, the pole ear can be formed at one time when the conductive layer is deposited. It should be noted that in lithium batteries, the metal conductive layer of the pole ear part on the composite current collector is thicker than the substrate part where the positive or negative electrode material is laid. In traditional processes, the pole ear is either added to the substrate part by welding, or the coating is locally thickened by secondary electroplating, sputtering and other processes. In this application, based on the pulsed electron beam deposition process, the local thickness of the coating is arbitrarily controlled, including three schemes, the specific schemes are as follows:

[0050] Solution 1: Control thickness by setting the number of pulsed electron beam guns.

[0051] Based on the premise that all pulse electron beam guns use the same output power, the thickness of the local coating can be controlled by setting different numbers of pulse electron beam guns. Figure 4 As shown, the pole ear portion is located on both sides of the substrate portion, so the number of pulse electron beam guns (210, 220) set at the position corresponding to the pole ear portion on the deposition chamber is greater than that of the substrate portion. Assuming that the thickness of the conductive layer of the substrate portion is 0.8 μm and the thickness of the conductive layer of the pole ear portion is 1.6 μm, the number of pulse electron beam guns used for depositing the pole ear portion can be set to twice that of the corresponding substrate portion.

[0052] Based on this solution, the step of welding the external tabs in the traditional process can be reduced, which can greatly improve the production process of the composite current collector; on the other hand, the metal plating of the tabs and the substrate has good integrity, which can effectively reduce the internal resistance of the finished battery and improve the battery performance. Compared with the traditional method, in addition to the advantage of being able to form alloy plating with different local thicknesses or even different mechanical strengths at one time, its production efficiency, energy consumption performance and environmental friendliness have been greatly improved.

[0053] Option 2: Thickness control can be achieved by modulating the output power of the pulsed electron beam gun.

[0054] Different from the first scheme, in this scheme, the number of pulsed electron beam guns for the lug and substrate is the same, but the output power, pulse frequency and other parameters are different, resulting in a difference in the thickness of the conductive layer deposited. In theory, the output power and pulse frequency are proportional to the thickness of the conductive layer deposited per unit time. The following table compares the thickness of the conductive layer deposited per unit time by a single pulsed electron beam gun under different parameters:

[0055] Pulse frequency (Hz) 5 20 50 80 100 200 Output power(W) 10 20 40 60 80 150 Voltage(kV) 15 15 15 15 15 15 Conductive film thickness (nm) 50 200 500 800 1000 2000

[0056] Based on the above principles, in addition to the solution of local thickening of the pole ear used in this application, the thickness of the coating can also be arbitrarily controlled by modulating the working parameters of any pulse electron beam gun, so that it can be applied to any scenario requiring planar coating to replace evaporation, sputtering, electroplating and their mixed processes.

[0057] On the premise that the thickness of the conductive layer deposited per unit time is fixed, by further adjusting the winding and unwinding speed of the base material, a composite current collector material with a clear and uniform conductive layer thickness can be obtained.

[0058] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A processing method based on a polymer film composite conductor, characterized in that: The following steps are involved: Step 1, using a plurality of pulsed electron beam guns to bombard the target material to generate a plasma plume, wherein the plasma plume flows toward the first surface of the base material, and is deposited on the first surface of the base material to form a first conductive layer; Step 2: On the second side of the base material, use a laser to peel off the base material to form a plurality of micro blind holes, wherein the depth of the micro blind holes is not less than the thickness of the base material; Step 3, using a plurality of pulsed electron beam guns to bombard the target material to generate a plasma plume, wherein the plasma plume flows toward the second surface of the base material, and is deposited on the second surface of the base material to form a second conductive layer; Step 4: at the micro blind hole, the coating on the second surface of the base material penetrates into the micro blind hole to make the first conductive layer and the second conductive layer conductive; The base material is divided into a pole ear portion and a base material portion in the width direction, and the thickness of the conductive layer of the pole ear portion is greater than that of the conductive layer of the base material portion.

2. The processing method according to claim 1, characterized in that: The plurality of pulse electron beam guns are divided into two groups. The pulse electron beam guns in the first group are used to form the conductive layer of the lug portion, and the pulse electron beam guns in the second group are used to form the conductive layer of the substrate portion.

3. The processing method according to claim 2, characterized in that: The number of the pulsed electron beam guns in the first group is greater than that of the pulsed electron beam guns in the second group.

4. The processing method according to claim 2, characterized in that: The output power of the first group of pulsed electron beam guns is greater than that of the second group of pulsed electron beam guns.

5. The processing method according to claim 1, characterized in that: The micro blind hole is located at the pole ear portion.

6. The processing method according to claim 4, characterized in that: The pulse frequency of the pulse electron beam guns of the first group is 5 Hz≤X≤200 Hz; the pulse frequency of the pulse electron beam guns of the second group is 5 Hz≤X≤200 Hz.

7. The processing method according to claim 1, characterized in that: The wavelength of the laser for stripping the base material is 192nm≤X≤1064nm, the pulse width of the laser is 1fs≤X≤1ns, the laser power is 0.001J / cm^2≤X≤10J / cm^2, and the pulse overlap range is 5%≤X≤90%.

8. The processing method according to claim 1, characterized in that: The thickness of the conductive layer on the pole ear is H1, the thickness of the conductive layer deposited on the substrate is H2, the ratio of H1 to H2 is X, and 1<X<5.

9. The processing method according to claim 1, characterized in that: There are at least two targets for depositing the first conductive layer or the second conductive layer, and the different targets are made of different materials.

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