Preparation method of crystalline silicon heterojunction solar cell surface metal grid line
By constructing a non-conductive anti-reflection armor layer with open grooves on the surface of the TCO layer of crystalline silicon heterojunction solar cells, the problem of weak bonding strength of electroplated metal electrodes is solved, the process flow is simplified, costs are reduced and cell efficiency is improved.
Patent Information
- Application Number
- CN202511252634.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-03
- Publication Date
- 2025-10-03
AI Technical Summary
The existing crystalline silicon heterojunction solar cells have weak bonding between the electroplated metal electrodes and the transparent conductive oxide layer, making them easily peeled off. In addition, the seed layer etching process is complex, which increases the difficulty of mass production and the cost of waste liquid treatment.
A non-conductive anti-reflective armor layer with open grooves is constructed on the surface of the TCO layer. Metal electrodes are prepared by combining magnetron sputtering and photolithography technology, eliminating the seed layer etching step, improving bonding strength and reducing costs.
It improves the bonding strength between the electroplated metal electrode and the TCO layer, reduces the risk of peeling, simplifies the process flow, reduces waste liquid discharge, and improves light utilization and battery efficiency.
Smart Images
Figure CN120751818A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of solar cells, and in particular relates to a method for preparing metal grid lines on the surface of a crystalline silicon heterojunction solar cell. Background Art
[0002] Crystalline silicon heterojunction (HJT) cells are highly efficient solar cells with a long passivation life, high open-circuit voltage, low process temperature (typically below 250°C), and fewer process steps compared to other N-type cells, resulting in a higher yield limit. These advantages have made them a hot topic in solar cell development. However, unlike other cells, HJT cells can typically only use low-temperature silver paste (sintering temperature below 250°C), which is more expensive than high-temperature silver paste. Furthermore, HJT cells require double-sided silver plating, consuming twice as much silver paste as PERC cells. Silver paste costs account for over 13% of the total cost of silicon heterojunction cells and over 51% of non-silicon costs. Electroplated copper electrodes offer advantages such as lower line resistance and lower process costs, and are considered the ultimate alternative to screen-printed silver metallization technology.
[0003] In existing electroplated copper metal electrode technology, to improve the contact and adhesion between the electroplated metal electrode layer and the transparent conductive oxide (TCO), a full-surface "seed layer" is typically deposited between the electroplated metal and the TCO layer using physical deposition methods such as magnetron sputtering and thermal evaporation. After masked electroplating, the mask is removed and the unplated portion of the seed layer is etched. This physical deposition of the seed layer can improve the adhesion between the copper and the cell surface, enhancing electrode performance. However, this not only adds the seed layer preparation step but also the seed layer etching process. Because the seed layer etching process also etches the TCO layer to some extent, not only must uniformity be ensured across the entire solar cell, but the concentration and process of the etching solution components must be strictly monitored and controlled during continuous production, significantly increasing the complexity of mass production. Furthermore, for large-scale production, the etching solution contains waste liquid containing metal ions dissolved in the seed layer and etching waste, resulting in additional costs and environmental impacts.
[0004] Selective or seedless electroplating processes, by directly electroplating metal electrodes on the cell surface, are expected to reduce costs and simplify the process. However, this still presents the problem of weak bonding between the electroplated metal electrodes and the TCO on the heterojunction cell surface, which can easily lead to delamination of the electroplated metal electrodes from the TCO surface. Therefore, a process is needed that eliminates the seed layer etching step while achieving sufficient bonding between the electroplated metal and the TCO layer. Summary of the Invention
[0005] In order to overcome the shortcomings of the existing technology, the present invention provides a method for preparing metal grid lines on the surface of crystalline silicon heterojunction solar cells. While ensuring strong bonding between the electroplated metal and the TCO layer, the seed layer etching step is omitted, the process difficulty of mass production of solar cells is reduced, and waste liquid discharge is reduced, making it suitable for large-scale production applications.
[0006] The present invention is specifically implemented through the following technical solutions.
[0007] The present invention provides a method for preparing metal grid lines on the surface of a crystalline silicon heterojunction solar cell, comprising the following steps: Preparation of crystalline silicon heterojunction solar cells without transparent conductive oxide (TCO) front electrode layer.
[0008] A TCO layer of a certain thickness (the thickness matches the thickness of the subsequent anti-reflection armor layer to achieve anti-reflection effect) is magnetron sputtered on the light-incoming side of the cell.
[0009] A photolithography pattern mask is prepared on the surface of the TCO layer to obtain a mask-patterned surface.
[0010] On the patterned surface of the mask, a non-conductive anti-reflection armor layer of a certain thickness (the thickness matches the aforementioned TCO layer to achieve the anti-reflection effect) is prepared and then cured.
[0011] The pattern mask is removed, leaving an anti-reflection armor structure with open grooves.
[0012] A metal electrode is deposited at the opening groove of the anti-reflection armor structure.
[0013] Finally annealing treatment.
[0014] Preferably, the thickness of the TCO layer is 50 nm to 100 nm, more preferably 60 nm to 80 nm.
[0015] Preferably, the thickness of the non-conductive anti-reflective armor layer is 80 nm to 120 nm, more preferably 90 nm to 110 nm.
[0016] Preferably, the width of the groove is 5 microns to 50 microns, more preferably 5 microns to 20 microns.
[0017] Preferably, the material of the non-conductive anti-reflection armor layer is nano-SiO2.
[0018] Preferably, the preparation process of the non-conductive anti-reflective armor layer is specifically as follows: A nano-SiO2 aqueous sol with a particle size of 5 nm to 50 nm (preferably 10-30 nm) and a mass concentration of 5% to 10% is selected, and hydrochloric acid or acetic acid is added to adjust the pH value to 2-6 (preferably 3-4) to obtain a first sol.
[0019] Anhydrous ethanol: ethyl orthosilicate: methyltriethoxysilane: HCl are stirred and uniformly mixed in a molar ratio of 10:3:1 to 3:0.001 (preferably 10:3:1 to 2:0.001) to obtain a mixed system, and KH570 silane coupling agent is added. The mass concentration of KH570 silane coupling agent in the mixed system is 0.1% to 1% (preferably 0.3% to 0.6%). The mixture is further stirred and aged for 3 to 7 days to obtain a second sol.
[0020] The first sol and the second sol are mixed in a mass ratio of 10-20:1 (preferably 12-15:1), and stirred to obtain a third sol.
[0021] The third sol is used to prepare a nano-SiO2 anti-reflective armor layer by a pulling method with a pulling speed controlled at 50 mm / min to 100 mm / min (preferably 60-80 mm / min).
[0022] Preferably, when preparing the TCO layer, the process parameters of magnetron sputtering are: using a transparent conductive material target In2O3:SnO2 of 90~99:~10 (preferably 95~99:1~5); the sputtering gas is a mixture of Ar gas and O2 gas, wherein the volume proportion of O2 gas is 1%~5% (preferably 2%-4%); the magnetron sputtering power density is 10W / cm²~20W / cm², the substrate temperature is 150℃~250℃ (preferably 150℃~200℃); the gas pressure is controlled at 0.5Pa~1.5Pa (preferably 0.5Pa~1Pa); the sputtering time is 3 minutes-20 minutes (preferably 5-15 minutes).
[0023] Preferably, the curing condition is 100° C. to 230° C. (preferably 150° C. to 200° C.) for 10 min to 60 min (preferably 30 min to 60 min).
[0024] Preferably, the preparation process of the electroplated metal electrode is: using a bright nickel electroplating solution, a current density of 0.5ASD~5ASD, and a nickel plating time of 0.5min~5min; using an acid copper electroplating solution, a current density of 0.5ASD~5ASD, and a copper plating time of 5min~20min; using an electroless tin plating solution for chemical tin plating, and reacting at room temperature for 1min~3min.
[0025] Preferably, the annealing treatment parameters are: N2 atmosphere, 150°C~230°C, and insulation for 10min~30min.
[0026] Compared with the prior art, the present invention has the following beneficial effects: The present invention addresses a common problem in selective seed layer or seedless electroplating processes: weak bonding between the plated metal electrode and the TCO surface of the heterojunction cell, which easily leads to peeling between the plated metal electrode and the TCO surface. The present invention proposes a novel structure to enhance the bonding and peeling strength between the plated metal electrode and the heterojunction cell surface. Specifically, the present invention constructs a non-conductive anti-reflection armor layer with open grooves on the TCO surface layer of the heterojunction cell. This structure not only forms a double-layer anti-reflection film with the TCO layer, achieving a transmittance-enhancing and anti-reflection effect, further improving light utilization and thereby enhancing the efficiency of silicon heterojunction solar cells, but also the open grooves provide a certain degree of armor protection for the plated metal electrode, to a certain extent reducing peeling and debonding of the plated metal electrode caused by external forces. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 The present invention is a process flow chart of the method for preparing metal grid lines on the surface of crystalline silicon heterojunction solar cells. DETAILED DESCRIPTION
[0028] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples and accompanying drawings. However, the examples are not intended to limit the present invention. The experimental methods and detection methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.
[0029] The present invention provides a method for preparing metal grid lines on the surface of crystalline silicon heterojunction solar cells. Figure 1 As shown, the following steps are included: S1. Prepare a crystalline silicon heterojunction solar cell without a transparent conductive oxide (TCO) front electrode layer.
[0030] S2. On the light-incoming side of the cell, a transparent conductive oxide layer, namely the TCO layer, is magnetron sputtered to a certain thickness (the thickness matches the thickness of the subsequent anti-reflection armor layer to achieve the anti-reflection effect).
[0031] S3. Prepare a photolithography pattern mask on the surface of the TCO layer to obtain a mask-patterned surface.
[0032] S4. On the patterned surface of the mask, a non-conductive anti-reflection armor layer of a certain thickness (the thickness matches the aforementioned TCO layer to achieve anti-reflection and anti-transmission effects) is prepared, and then cured and post-processed.
[0033] S5. Remove the pattern mask, leaving an anti-reflection armor structure with open grooves.
[0034] S6. Depositing metal electrodes at the opening grooves of the anti-reflective armor structure.
[0035] S7: Final annealing treatment.
[0036] The present invention constructs a non-conductive anti-reflection armor layer with open grooves on the TCO surface layer of the heterojunction cell. This structure not only forms a double-layer anti-reflection film with the TCO layer to achieve the effects of increasing transmittance and reducing reflection, but also reduces the absolute value of the surface reflectivity by 1% to 2%, further improving the utilization rate of light, and thus improving the efficiency of silicon heterojunction solar cells by 0.3% to 1%. At the same time, the open groove structure can provide a certain degree of armor protection for the electroplated metal electrodes, to a certain extent reducing the peeling and debonding of the electroplated metal electrodes caused by external forces.
[0037] The present invention will be specifically described below through the following examples.
[0038] Example 1 A method for preparing metal grid lines on the surface of a crystalline silicon heterojunction solar cell comprises the following steps: S1. Prepare a crystalline silicon heterojunction solar cell without a transparent conductive oxide (TCO) front electrode layer.
[0039] S2. A 60nm thick TCO layer (matching the thickness of the subsequent anti-reflection armor layer to achieve anti-reflection and anti-transmission effects) is magnetron sputtered on the light-incoming side of the cell. The magnetron sputtering process parameters are: a transparent conductive target material (In2O3:SnO2) with a ratio of 95:5; a sputtering gas mixture of Ar and O2, with O2 accounting for 3% by volume; a magnetron sputtering power density of 15W / cm², a substrate temperature of 150°C, a pressure of 1 Pa, and a sputtering time of 10 minutes.
[0040] S3. Prepare a photolithography pattern mask on the TCO layer.
[0041] S4. Based on the graphic mask, a 100-nanometer-thick nano-SiO2 non-conductive anti-reflection armor layer is prepared, and then cured and post-processed.
[0042] Specifically, a nano-SiO2 aqueous sol with a particle size of 30 nanometers and a mass concentration of 5% was selected and hydrochloric acid was added to adjust the pH to 3 to obtain the first sol. Anhydrous ethanol: ethyl orthosilicate: methyltriethoxysilane: HCl were mixed at a molar ratio of 10:3:1:0.001. KH570 silane coupling agent was added at a mass concentration of 0.5% (this concentration refers to the concentration in the above mixture) and stirred continuously for 3 days to obtain the second sol. The first and second sols were mixed at a mass ratio of 15:1 and stirred to obtain the third sol. Using the third sol, a 100-nanometer-thick SiO2 anti-reflective armor layer was prepared by Czochralski method at a controlled pulling speed of 50 mm / min. The layer was then cured at 200°C for 30 minutes.
[0043] S5. Remove the pattern mask, leaving an anti-reflection armor structure with an open groove, where the width of the groove is 20 microns.
[0044] S6. Deposit metal electrodes in the open grooves of the anti-reflective armor structure. Specifically, a bright nickel electroplating solution (Spherolyte Ni, Atotech) was used at a current density of 1 ASD for 2 minutes. Next, an acid copper electroplating solution (Cuplate 850X, Zhangzhou Debaoli Chemical Co., Ltd.) was used at a current density of 2 ASD for 10 minutes. Finally, an electroless tin plating solution (Q / YS.402, Guangzhou Yishun Chemical Co., Ltd.) was used for chemical tin plating at room temperature for 2 minutes.
[0045] S7. Finally, annealing treatment was performed at 200°C for 20 min under N2 atmosphere protection.
[0046] Example 2 A method for preparing metal grid lines on the surface of a crystalline silicon heterojunction solar cell comprises the following steps: S1. Prepare a crystalline silicon heterojunction solar cell without a transparent conductive oxide (TCO) front electrode layer.
[0047] S2. On the light-entering side of the cell, a 100-nanometer-thick TCO layer (this thickness matches the thickness of the subsequent anti-reflection armor layer to achieve the desired anti-reflection and anti-transmission effect) is magnetron sputtered. The magnetron sputtering process parameters are: a transparent conductive target material (In2O3:SnO2) with a ratio of 99:1; a sputtering gas mixture of Ar and O2, with O2 accounting for 5% by volume; a magnetron sputtering power density of 10 W / cm², a substrate temperature of 200°C, a pressure of 0.5 Pa, and a sputtering time of 20 minutes.
[0048] S3. Prepare a photolithography pattern mask on the TCO layer.
[0049] S4. Based on the graphic mask, a nano-SiO2 non-conductive anti-reflective armor layer with a thickness of 110 nanometers is prepared, and then cured and post-treated.
[0050] Specifically, a nano-SiO2 aqueous sol with a particle size of 10 nanometers and a mass concentration of 10% was prepared by adding hydrochloric acid to adjust the pH to 4 to obtain the first sol. Anhydrous ethanol, ethyl orthosilicate, methyltriethoxysilane, and HCl were mixed at a molar ratio of 10:3:2:0.001. A silane coupling agent, KH570, was added at a mass concentration of 0.3%. Stirring was continued and the mixture was aged for 7 days to obtain the second sol. The first and second sols were mixed at a mass ratio of 10:1 and stirred to obtain the third sol. Using the third sol, a 110 nanometer thick SiO2 anti-reflective armor layer was prepared using the Czochralski method at a controlled pulling speed of 100 mm / min. The mixture was then cured at 150°C for 30 minutes.
[0051] S5. Remove the pattern mask, leaving an anti-reflection armor structure with an open groove, where the width of the groove is 30 microns.
[0052] S6. Deposit metal electrodes in the open grooves of the anti-reflective armor structure. Specifically, first use a bright nickel electroplating solution (DuPont NIKAL™ BP / BAF) at a current density of 3 ASD for 1 minute. Then use an acid copper electroplating solution (Cuplate 650X, Zhangzhou Debaoli Chemical Co., Ltd.) at a current density of 5 ASD for 5 minutes. Finally, perform chemical tin plating using an electroless tin plating solution (Beichen Hardware Technology Chemical Tin Plating Solution) at room temperature for 1 minute.
[0053] S7. Finally, annealing treatment is performed at 150°C in a H2 atmosphere for 10 min.
[0054] Comparative Example 1 S1. Prepare a crystalline silicon heterojunction solar cell without a transparent conductive oxide (TCO) front electrode layer.
[0055] S2. On the light-incoming side of the cell, a TCO layer with a thickness of 100 nm is magnetron sputtered. The process parameters of magnetron sputtering are: a transparent conductive material target material In2O3:SnO2 with a ratio of 99:1 is used; the sputtering gas is a mixture of Ar gas and O2 gas, of which the volume proportion of O2 gas is 5%; the magnetron sputtering power density is 10W / cm², the substrate temperature is 200°C; the gas pressure is controlled at 0.5Pa; and the sputtering time is 20 minutes.
[0056] S3. Prepare a photolithography pattern mask on the TCO layer.
[0057] S4. Based on the graphic mask, a nano-SiO2 non-conductive anti-reflective armor layer with a thickness of 30 nanometers is prepared, and then cured and post-treated.
[0058] Specifically, a 10-nanometer-sized, 5%-mass concentration aqueous SiO₂ sol was prepared by adding hydrochloric acid to adjust the pH to 4 to obtain the first sol. Anhydrous ethanol, ethyl orthosilicate, methyltriethoxysilane, and HCl were mixed at a molar ratio of 10:3:2:0.001. A 0.3%-mass concentration of KH570 silane coupling agent was added, stirred, and aged for 7 days to obtain the second sol. The first and second sols were mixed at a mass ratio of 10:1 and stirred to obtain the third sol. Using the third sol, a 30-nanometer-thick SiO₂ anti-reflective armor layer was prepared using the Czochralski method at a controlled pulling speed of 50 mm / min. The layer was then cured at 150°C for 30 minutes.
[0059] S5. Remove the pattern mask, leaving an anti-reflection armor structure with an open groove; the width of the groove is 30 microns.
[0060] S6. Deposit metal electrodes in the open grooves of the anti-reflective armor structure. Specifically, a bright nickel electroplating solution (Atotech Spherolyte Ni) was used at a current density of 3 ASD for 1 minute. Next, an acid copper electroplating solution (Cuplate 850X, produced by Zhangzhou Debaoli Chemical Co., Ltd.) was used at a current density of 5 ASD for 5 minutes. Finally, an electroless tin plating solution (produced by Beichen Hardware Technology) was used for chemical tin plating at room temperature for 1 minute.
[0061] S7. Annealing treatment is performed at 150°C for 10 min under N2 atmosphere.
[0062] Comparative Example 2 The metal electrodes are deposited directly on the TCO layer by electroplating (without armor layer).
[0063] S1. Prepare a crystalline silicon heterojunction solar cell without a transparent conductive oxide (TCO) front electrode layer.
[0064] S2. On the light-incoming side of the cell, a TCO layer with a thickness of 100 nm is magnetron sputtered. The process parameters of magnetron sputtering are as follows: a transparent conductive material target material In2O3:SnO2 with a ratio of 99:1 is used; the sputtering gas is a mixture of Ar gas and O2 gas, of which the volume proportion of O2 gas is 5%; the magnetron sputtering power density is 10W / cm², the substrate temperature is 200°C; the gas pressure is controlled at 0.5Pa; and the sputtering time is 20 minutes.
[0065] S3. Prepare a photolithography pattern mask on the TCO layer, with a pattern opening width of 30 microns.
[0066] S4. Deposit metal electrodes at the openings of the patterned mask using the patterned mask. Specifically, a bright nickel electroplating solution (Spherolyte Ni, Atotech) is used at a current density of 3 ASD for 1 minute. Next, an acid copper electroplating solution (Cuplate 850X, produced by Zhangzhou Debaoli Chemical Co., Ltd.) is used at a current density of 5 ASD for 5 minutes. Finally, an electroless tin plating solution (Electroless Tin Plating Solution from Beichen Hardware Technology) is used for chemical tin plating at room temperature for 1 minute.
[0067] S5. Remove the graphic mask to prepare an electroplated metal gate line crystalline silicon heterojunction battery without anti-reflection armor structure.
[0068] S6. Annealing treatment is performed at 200°C for 20 min under N2 atmosphere.
[0069] The batteries prepared in Example 1, Example 2, Comparative Example 1 and Comparative Example 2 were tested using the following test methods: Average surface reflectivity: A UV-Vis-NIR spectrometer with an integrating sphere accessory was used to test the reflectivity in the range of 380-780 nm and calculate the average reflectivity in the range.
[0070] Metal grid peeling force: A horizontal solder strip peeling force testing machine was used to perform a 180° peeling test on the samples. Under the same test conditions for the same samples, each group of samples contained 5 identical samples, and each sample tested 5 grid lines. The average peeling force of the 5 grid lines was taken as the peeling force of the sample, and the average peeling force of the 5 samples was taken as the peeling force of the metal grid line prepared under these conditions.
[0071] The results are shown in Table 1.
[0072] Table 1 Performance data of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 It can be seen that compared with Comparative Example 2 in which the metal electrode is directly deposited on the TCO layer by electroplating, the performance of Example 1, Example 2 and Comparative Example 1 are all improved. Compared with Example 1 and Example 2, the thickness of the non-conductive anti-reflective armor layer in Comparative Example 1 is smaller, its average surface reflectivity is improved, and the metal grid line peeling force is reduced, which shows that the thickness of the non-conductive anti-reflective armor layer has an important influence on the average surface reflectivity and the metal peeling force.
[0073] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications of the present invention fall within the scope of the claims and their equivalents, such changes and modifications are intended to be included.
Claims
1. A method for preparing metal grid lines on the surface of crystalline silicon heterojunction solar cells, characterized in that: The following steps are involved: Magnetron sputtering of a transparent conductive oxide layer on the light-incoming side of the crystalline silicon heterojunction cell; preparing a photolithography pattern mask on the surface of the transparent conductive oxide layer to obtain a mask-patterned surface; On the patterned surface of the mask, a non-conductive anti-reflection armor layer is prepared. The non-conductive anti-reflection armor layer and the transparent conductive oxide layer are combined to increase transmittance and reduce reflection, and then a curing post-treatment is performed; Removing the pattern mask to obtain an anti-reflection armor structure with open grooves; Depositing metal electrodes at the opening grooves of the anti-reflective armor structure; Finally annealing treatment.
2. The preparation method according to claim 1, characterized in that The thickness of the transparent conductive oxide layer is 50 nanometers to 100 nanometers.
3. The preparation method according to claim 1, characterized in that The thickness of the non-conductive anti-reflection armor layer is 80 nanometers to 120 nanometers.
4. The preparation method according to claim 1, characterized in that The width of the opening groove is 5 microns to 50 microns.
5. The preparation method according to claim 1, characterized in that The material of the non-conductive anti-reflection armor layer is nano-SiO2.
6. The preparation method according to claim 5, characterized in that The preparation process of the non-conductive anti-reflective armor layer comprises the following steps: A nano-SiO2 aqueous sol with a particle size of 5 nm to 50 nm and a mass concentration of 5% to 10% is selected, and hydrochloric acid or acetic acid is added to adjust the pH value to 2 to 6 to obtain a first sol; Ethanol, ethyl orthosilicate, methyltriethoxysilane, and HCl were stirred and uniformly mixed in a molar ratio of 10:3:1 to 3:0.001, and a silane coupling agent was added. The mixture was stirred and aged for 3 to 7 days to obtain a second sol. Mix the first sol and the second sol in a mass ratio of 10 to 20:1, and stir and mix them evenly to obtain a third sol; The third sol was used to prepare an anti-reflective armor layer by a Czochralski method with a pulling speed controlled at 50 mm / min to 100 mm / min.
7. The preparation method according to claim 1, characterized in that When preparing the transparent conductive oxide layer, the process parameters of magnetron sputtering are: Transparent conductive material target: In2O3:SnO2 mass ratio is 90~99:1~10; the sputtering gas is a mixture of Ar gas and O2, of which O2 accounts for 1%~5% by volume; the magnetron sputtering power density is 10W / cm²~20W / cm², the substrate temperature is 150℃~250℃; the gas pressure is 0.5Pa~1.5Pa; the sputtering time is 3 minutes~20 minutes.
8. The preparation method according to claim 1, characterized in that The post-curing treatment conditions are curing at 100℃~230℃ for 10min~60min.
9. The preparation method according to claim 1, characterized in that The preparation process of the metal electrode is: first use a bright nickel electroplating solution with a current density of 0.5ASD~5ASD and a nickel plating time of 0.5min~5min; then use an acid copper electroplating solution with a current density of 0.5ASD~5ASD and a copper plating time of 5min~20min; then use a chemical tin plating solution for chemical tin plating, and react at room temperature for 1min~3min.
10. The preparation method according to claim 1, characterized in that The parameters of the annealing treatment are: in N2 and / or H2 atmosphere, at 150℃~230℃, and keeping warm for 10min~30min.