Electroplating solution for battery piece and preparation method of electroplating solution

Abstract

The invention discloses an electroplating solution for a battery piece and a preparation method of the electroplating solution, the electroplating solution comprises electrolyte copper salt, organic acid, chloride ions, a brightening agent, a leveling agent and a carrier, and when the electroplating solution is used for electroplating a photovoltaic battery, an obtained plating layer is good in ductility, high in tensile strength, uniform, fine and glossy.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon wafer surface treatment, and particularly to an electroplating solution for battery wafers and a preparation method thereof. Background Art

[0002] Photovoltaic power generation is a new type of power generation technology that directly converts sunlight radiation into electrical energy using the photovoltaic effect. Because of its advantages such as abundant resources, cleanliness, safety, and long lifespan, it is considered to be one of the most promising renewable energy technologies and is currently widely used.

[0003] Structurally, photovoltaic power generation is a technology that directly converts light energy into electrical energy using the photovoltaic effect at the semiconductor interface. Photovoltaic power generation components mainly include three major parts: solar panels (components), controllers, and inverters, and the main components are composed of electronic components. Photovoltaic cells can be connected in series and then encapsulated and protected to form large-area solar cell components, and together with components such as power controllers, a photovoltaic power generation device is formed.

[0004] In the current manufacturing process, metallization is one of the key processes for photovoltaic battery wafers. It is mainly used to manufacture the electrodes of photovoltaic batteries, form Ohmic contacts at both ends of the PN junction, and achieve current output. The metallization process has a great influence on the reliability, cost, conversion efficiency, and process route of the battery.

[0005] Metallization techniques can be roughly divided into two types: contact and non-contact. In the current manufacturing process, most contact metallization techniques still apply the most mature screen printing silver paste process, and more efforts are made to optimize the design of the main grid and fine grid, but the cost of screen printing silver paste is high. Non-contact metallization techniques are no longer limited to the screen printing process, and through various innovative electrode manufacturing methods, further optimization of electroplated copper, grid line morphology, etc. is achieved. Specifically, it is mainly manifested in electroplating, transfer printing, inkjet printing technologies, etc. Currently, there are also leading equipment manufacturers and downstream parties attempting to replace the screen printing technology with electroplating because the cost of electroplating is relatively low. However, the electroplating effect of the electroplating solutions on the market is not good at present, specifically manifested as: low current density, high stress of the electroplated layer, low ductility of the coating, and easy appearance of cracks. Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned drawbacks and provide an electroplating solution for battery wafers and a preparation method thereof. When electroplating using this electroplating solution, the obtained coating has good ductility, high tensile strength, and is uniform, delicate, and shiny.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is:

[0008] An electroplating solution for battery wafers includes electrolyte copper salt, organic acid, chloride ion, brightener, leveling agent, and carrier.

[0009] In the electroplating solution, the content of copper ions is 30 - 50 g / L, the content of organic acid is 15 - 25 g / L, the content of chloride ions is 60 - 100 ppm, the content of brightener is 3 - 5 g / L, the content of leveling agent is 8 - 12 g / L, and the content of carrier is 1 - 3 g / L.

[0010] The content of the copper ions is 35, 38, 40, 42, 45 or 48 g / L, the content of the organic acid is 18, 20, 22 or 24 g / L, the content of the chloride ions is 70, 75, 80, 85, 90 or 95 ppm, the content of the brightener is 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.6 or 4.8 g / L, the content of the leveling agent is 9, 9.5, 10, 10.5, 11 or 11.5 g / L, and the content of the carrier is 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.6 or 2.8 g / L.

[0011] The electrolyte copper salt is copper chloride, copper sulfate, copper citrate or copper methyl sulfonate.

[0012] The organic acid is one or a mixture of more than one of citric acid, tartaric acid, potassium citrate, methyl sulfonic acid and potassium tartrate.

[0013] The brightener includes sulfuric acid, disodium 3,3'-dithiobis-1-propanesulfonate, copper sulfate.

[0014] The leveling agent includes Guanidine, N,N′-bis[3-(dimethylamino)propyl]-, polymer with 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyl)]dimethansulfonate.

[0015] The carrier includes sulfuric acid, polyethylene glycol with a PEG molecular weight of 500 - 20000.

[0016] The chloride ions are provided by hydrogen chloride.

[0017] A preparation method of an electroplating solution for battery wafers, comprising the following steps:

[0018] S1. Directly obtain a prepared electrolyte copper salt solution, add an organic acid, and stir until completely dissolved to obtain solution A;

[0019] S2. Under stirring conditions, add hydrogen chloride to the solution A obtained in step S1, and stir until completely dissolved to obtain solution B;

[0020] S3. Under stirring conditions, a brightener, a leveling agent, and a leveling agent are added to the solution B obtained in step S2, and stirred until completely dissolved to obtain the electroplating solution for the battery chip.

[0021] Since the present invention adopts the above technical solution, it has the following beneficial effects:

[0022] 1. When using the electroplating solution of the present invention for electroplating photovoltaic battery chips, the deposition stress is very low, so that the obtained copper coating has good ductility and high tensile strength, thereby greatly improving the toughness of the coating and further greatly enhancing the reliability of the coating;

[0023] 2. When using the electroplating solution of the present invention for electroplating photovoltaic battery chips, it can prevent cracks caused by too thin coating, and can also make the obtained coating more uniform, delicate and shiny;

[0024] 3. When the electrolyte copper salt is selected from copper sulfate or copper citrate and copper methanesulfonate, it can be applicable to a high current density above 30 ASD. Compared with the traditional current density of 2 ASD, the production capacity can be increased by dozens of times. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the appearance of the coating obtained after electroplating with the copper electroplating solution of the first embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of the appearance of the coating obtained after electroplating with the copper electroplating solution of the second embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the appearance of the coating obtained after electroplating with the copper electroplating solution of the third embodiment of the present invention;

[0028] Figure 4 It is a schematic diagram of the appearance of the coating obtained after electroplating with other copper electroplating solutions;

[0029] Figure 5 It is a schematic diagram of the appearance of the coating obtained after electroplating with other copper electroplating solutions. Detailed Embodiments

[0030] The following describes the preferred embodiments of the present invention with reference to the drawings. Among them, the experimental methods for which the operation steps are not specifically described are all carried out according to the corresponding product specifications. The instruments, reagents, and consumables used in the embodiments can be obtained from commercial companies without special instructions.

[0031] The present invention discloses an electroplating solution for battery chips, and the electroplating solution includes an electrolyte copper salt, an organic acid, chloride ions, a brightener, a leveling agent, and a carrier.

[0032] In the electroplating solution, the content of copper ions is 30-50 g / L, the content of organic acid is 15-25 g / L, the content of chloride ions is 60-100 ppm, the content of brightener is 3-5 g / L, the content of leveling agent is 8-12 g / L, and the content of carrier is 1-3 g / L. The copper ions are provided by an electrolyte copper salt. Preferably, the content of copper ions is 35, 38, 40, 42, 45 or 48 g / L, the content of organic acid is 18, 20, 22 or 24 g / L, the content of chloride ions is 70, 75, 80, 85, 90 or 95 ppm, the content of brightener is 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.6 or 4.8 g / L, the content of leveling agent is 9, 9.5, 10, 10.5, 11 or 11.5 g / L, and the content of carrier is 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.6 or 2.8 g / L.

[0033] The electrolyte copper salt is copper chloride, copper sulfate, copper citrate or copper methyl sulfonate.

[0034] The organic acid is one or a mixture of more of citric acid, tartaric acid, potassium citrate, methyl sulfonic acid and potassium tartrate.

[0035] The brightener includes sulfuric acid, disodium 3,3'-dithiobis-1-propanesulfonate and copper sulfate.

[0036] The leveling agent includes Guanidine, N,N′-bis[3-(dimethylamino)propyl]-, polymer with 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyl)]dimethansulfonate.

[0037] The carrier includes sulfuric acid and polyethylene glycol. Preferably, the PEG molecular weight of the polyethylene glycol is 500-20000.

[0038] The chloride ions are provided by hydrogen chloride.

[0039] The present invention also discloses a preparation method of the electroplating solution for the battery cells, including the following steps:

[0040] S1. Directly obtain a prepared electrolyte copper salt solution, add an organic acid, and stir until completely dissolved to obtain solution A;

[0041] S2. Under stirring conditions, add hydrogen chloride to the solution A obtained in step S1, and stir until completely dissolved to obtain solution B;

[0042] S3. Under stirring conditions, a brightener, a leveling agent, and a leveling agent are added to the solution B obtained in step S2, and stirred until completely dissolved to obtain the electroplating solution for the above-mentioned solar cell.

[0043] Preferably, the addition order of the brightener, the leveling agent, and the leveling agent can be changed, and each is added until completely dissolved before adding another one.

[0044] By adopting the above configuration method, side reactions of each component can be avoided, and thus the required electroplating solution can be obtained.

[0045] The brightener is an accelerator, which can accelerate the reduction of copper ions. The leveling agent and the carrier are both inhibitors, which can slow down the deposition of copper ions in the high-current area. Because of the above settings, the carrier forms a "sponge" - like composite carrier layer, and this kind of carrier layer can form a diffusion interface between the electrolyte and the copper surface, playing a wetting role. Therefore, the electroplating solution of the present invention obtained by combining these three components with copper electrolyte salts, organic acids, and chloride ions has a very high quality of the copper coating obtained after electroplating the solar cell. Specifically, the brightener in the electroplating solution of this aspect can reduce the coating stress in the physical properties of the deposited copper, thereby increasing the ductility and tensile strength of the copper-deposited metal, that is, improving the toughness of the coating, and further enhancing the reliability of the coating; because the leveling agent contains short - molecule (monomer) dye compounds with nitrogen (amine) functional groups, it can prevent the local reduction of copper ions in the high - current density area. Only at the exposed cathode position (higher potential), the leveling agent will be attracted and inhibit copper deposition. In this way, not only can it prevent cracks caused by too thin coating, but also make the obtained coating more uniform, delicate and shiny.

[0046] In addition, since copper sulfate or copper citrate, copper methanesulfonate can accommodate more copper ions, when the copper electrolyte salt is selected as copper sulfate or copper citrate, copper methanesulfonate, it can be applicable to a high current density above 30 ASD. Compared with the traditional current density of 2 ASD, the production capacity can be increased by dozens of times.

[0047] When the copper electrolyte salt is selected as copper methanesulfonate, due to the good high efficiency, dispersibility and surface smoothness of copper methanesulfonate, it can provide an efficient electroplating process, quickly form a uniform and dense copper electroplating layer; and it helps to maintain a uniform electroplating solution concentration, thereby obtaining a uniform electroplating effect; furthermore, it can produce a smooth and pore - free electroplating layer, thereby further improving the surface quality and appearance of the object to be plated.

[0048] When the electrolyte copper salt is copper chloride, copper chloride has good electrical conductivity, which helps the conduction of current during electroplating, and has strong uniformity. Therefore, when it is used as the electrolyte copper salt, it can also produce a uniform and smooth electroplated layer, making the surface of the object to be plated have a high gloss; in addition, copper chloride electroplating usually has high efficiency and can complete the electroplating process faster, thus improving production efficiency; furthermore, compared with other electrolyte copper salts, the cost of copper chloride is relatively low, so the electroplating cost can be reduced.

[0049] Moreover, copper chloride, copper sulfate, copper citrate or copper methanesulfonate all have controllability. When they are selected as the electrolyte copper salt, it is relatively easy to control electroplating parameters such as temperature, concentration, pH value and current density, so as to obtain the required electroplating effect.

[0050] The following is an electroplating experiment using the electroplating solution of the present invention.

[0051] In the first embodiment, in the electroplating solution, the content of copper ions is 40 g / L, the content of the organic acid is 20 g / L, the content of chloride ions is 80 ppm, the content of the brightener is 4 ml / L, the content of the leveling agent is 10 ml / L, and the content of the carrier is 2 ml / L.

[0052] The electrolyte copper salt is copper methanesulfonate, the organic acid is potassium citrate, and the chloride ions are provided by hydrogen chloride; the brightener includes sulfuric acid, 3,3'-dithiobis-1-propane sulfonic acid disodium salt, copper sulfate; the leveling agent includes Guanidine,N,N′-bis[3-(dimethylamino)propyl]-,polymer with 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyl)]dimethansulfonate; the carrier includes sulfuric acid, polyethylene glycol with a PEG molecular weight of 500 to 20,000.

[0053] In the second embodiment, in the electroplating solution, the content of copper ions is 40 g / L, the content of the organic acid is 20 g / L, the content of chloride ions is 80 ppm, the content of the brightener is 1 ml / L, the content of the leveling agent is 6 ml / L, and the content of the carrier is 1 ml / L.

[0054] The electrolyte copper salt is copper methyl sulfonate, the organic acid is potassium citrate, and the chloride ions are provided by hydrogen chloride; the brightener includes sulfuric acid, disodium 3,3'-dithiobis-1-propanesulfonate, and copper sulfate; the leveling agent includes Guanidine,N,N′-bis[3-(dimethylamino)propyl]-, polymer with 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyl)]dimethansulfonate; the carrier includes sulfuric acid and polyethylene glycol with a PEG molecular weight of 500 to 20,000.

[0055] In the third embodiment, in the electroplating solution, the content of copper ions is 40 g / L, the content of the organic acid is 20 g / L, the content of chloride ions is 80 ppm, the content of the brightener is 7 ml / L, the content of the de-leveling agent is 6 ml / L, and the content of the carrier is 3 ml / L.

[0056] The electrolyte copper salt is copper methyl sulfonate, the organic acid is potassium citrate, and the chloride ions are provided by hydrogen chloride; the brightener includes sulfuric acid, disodium 3,3'-dithiobis-1-propanesulfonate, and copper sulfate; the leveling agent includes Guanidine,N,N′-bis[3-(dimethylamino)propyl]-, polymer with 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyl)]dimethansulfonate; the carrier includes sulfuric acid and polyethylene glycol with a PEG molecular weight of 500 to 20,000.

[0057] Using the electroplating solutions in the above first embodiment, second embodiment, and third embodiment, and using a HULL CELL, with an insoluble anode (such as an insoluble titanium mesh), and using the battery slice to be electroplated after cleaning (such as a heterojunction photovoltaic cell slice) as the cathode, electroplating is carried out. The electroplating conditions are: temperature 30°C, current density 6.0 A / dm 2 , and the electroplating time is 2 min. The electroplating method is a conventional method, so it will not be elaborated in detail here. After electroplating, the appearances of the coatings are as shown in Figure 1 , 2 , and 3.

[0058] Observing the appearance of the coating and evaluating the quality of the coating, the observation and evaluation results are as follows:

[0059]

[0060]

[0061] From the observation of the appearance of the above-mentioned coatings, it can be seen that when using the copper electroplating solution of the present invention, even though the component ratios are different, resulting in different areas of available current density for the coatings obtained after electroplating, there are still areas of available current density, and the coatings in these areas are uniform, delicate and shiny.

[0062] Figure 1 、 2 In FIGS. 1, 2, and 3, taking the two vertical lines in the figures as the demarcation lines, from left to right are the high-current region, the medium-current region, and the low-current region, which are basically divided into three equal parts. This is the basic regional division method in the art, so it will not be elaborated here.

[0063] Perform stress testing, that is, test the deposition stress of the coating obtained after electroplating. The specific operation can be as follows: Deposit a 100-nm-thick copper layer on a silicon wafer by PVD deposition. After pickling and cleaning it to the state to be electroplated, use the Hulling Cell electroplating method to electroplate the copper electroplating solutions in the first embodiment, the second embodiment, and the third embodiment on the copper layer respectively to obtain copper films. The electroplating conditions are: the temperature is 35 °C, the cathode current density is 20 A / dm 2 and the anode current density is 10 A / dm 2 , and the electroplating time is 6 min.

[0064] After electroplating is completed, the thickness of the copper film is expected to be 25 μm. Use a spiral stress tester to measure the deposition stress of the electroplated copper film. A spiral stress tester is usually an instrument used to measure the stress of materials, thin films or coatings. It is mainly based on the principle of a spiral spring, and calculates the stress of the material by measuring the deformation of the spiral. This type of testing instrument can be used for different types of materials and applications, including metals, plastics, coatings, etc. Its testing method is a well-known technology and not an innovation point of the present invention, so it will not be elaborated here.

[0065] The test results of the coating stress are as follows:

[0066] Project Example 1 Example 2 Example 3 <![CDATA[Deposition stress (Kg / mm 2 )]]> 0.47 0.95 0.89

[0067] According to the above test results, it can be seen that the deposition stress of the electroplated copper film corresponding to the copper electroplating solution of Example 1 is the lowest. The deposition stress of the electroplated copper films corresponding to Example 2 and Example 2 is relatively higher. However, although the different component ratios result in different test results of the deposition stress of the finally obtained coatings, they do not exceed 1 Kg / mm 2 , and they are all very low. Such a low deposition stress can completely increase the ductility and tensile strength of the copper-deposited metal, improve the toughness of the coating, and thus enhance the reliability of the coating.

[0068] Electroplating can be carried out using other copper electroplating solutions, and then the appearance of the coatings can be observed for comparison. The specific operation is as follows:

[0069] Comparative Example 1

[0070] The copper electroplating solution includes an electrolyte copper salt, an organic acid, and hydrogen chloride. The content of copper ions is 40 g / L, the content of the organic acid is 20 g / L, and the chloride ion content is 80 ppm. The electrolyte copper salt is copper sulfate, the organic acid is potassium citrate, and the chloride ions are provided by hydrogen chloride. When preparing, the above steps S1 and S2 are carried out in sequence.

[0071] Comparative Example 2

[0072] The copper electroplating solution includes an electrolyte copper salt, an organic acid, and hydrogen chloride; the content of copper ions is 50 g / L, the content of the organic acid is 25 g / L, and the chloride ion content is 100 ppm; and the electrolyte copper salt is copper sulfate; the organic acid is potassium citrate, and the chloride ions are provided by hydrogen chloride. When preparing, the above steps S1 and S2 are also carried out in sequence.

[0073] Electroplating is carried out using the copper electroplating solutions of Comparative Example 1 and Comparative Example 2. The electroplating method is the same as that of the above Examples 1 - 3. The appearances of the obtained coatings are respectively as Figure 4 、 5 shown. The appearance observation and evaluation of the coatings are as follows:

[0074]

[0075] It can be seen from the above observation results that when electroplating using the copper electroplating solutions of the above non-invention, the appearance of the obtained coatings is extremely poor, and there is no available current density region at all, which is a complete failure.

[0076] When performing stress tests in the same manner as in Examples 1 to 3 above, that is, depositing a 100-nm-thick copper layer on the surface of a silicon wafer by PVD, and then electroplating on the copper layer using the copper electroplating solutions of Comparative Example 1 and Comparative Example 2, the result is either failure to electroplate or the silicon wafer with the deposited copper layer being burned. Thus, it further shows that the deposition stress of the electroplating solutions of Comparative Example 1 and Comparative Example 2 is completely unacceptable.

[0077] The above has described the embodiments of the present invention in detail, but the above content is only the preferred embodiments of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. An electroplating solution for battery chips, characterized in that: It includes an electrolyte copper salt, an organic acid, chloride ions, a brightening agent, a leveling agent, and a carrier agent.

2. The electroplating solution for battery wafers according to claim 1, characterized in that: In the electroplating solution, the content of copper ions is 30 - 50 g / L, the content of the organic acid is 15 - 25 g / L, the content of chloride ions is 60 - 100 ppm, the content of the brightening agent is 3 - 5 g / L, the content of the leveling agent is 8 - 12 g / L, and the content of the carrier agent is 1 - 3 g / L.

3. The electroplating solution for battery wafers according to claim 2, characterized in that: The content of the copper ions is 35, 38, 40, 42, 45, or 48 g / L, the content of the organic acid is 18, 20, 22, or 24 g / L, the content of chloride ions is 70, 75, 80, 85, 90, or 95 ppm, the content of the brightening agent is 3.2, 3.5, 3.8, 4, 4.2, 4.5, 4.6, or 4.8 g / L, the content of the leveling agent is 9, 9.5, 10, 10.5, 11, or 11.5 g / L, and the content of the carrier agent is 1.2, 1.5, 1.8, 2, 2.2, 2.5, 2.6, or 2.8 g / L.

4. The electroplating solution for battery wafers according to any one of claims 1 to 3, characterized in that: The electrolyte copper salt is copper chloride, copper sulfate, copper citrate, or copper methyl sulfonate.

5. The electroplating solution for battery wafers according to claim 4, wherein: The organic acid is one or a mixture of more of citric acid, tartaric acid, potassium citrate, methyl sulfonic acid, and potassium tartrate.

6. The electroplating solution for battery wafers according to any one of claims 1 to 5, characterized in that: The brightening agent includes sulfuric acid, disodium 3,3'-dithiobis-1-propanesulfonate, and copper sulfate.

7. The electroplating solution for battery wafers according to any one of claims 1 to 6, characterized in that: The leveling agent includes Guanidine, N,N′-bis[3-(dimethylamino)propyl]-, polymer with 1,1′-[1,2-ethanediylbis(oxy-2,1-ethanediyl)]dimethansulfonate.

8. The electroplating solution for battery wafers according to any one of claims 1 to 7, characterized in that: The carrier agent includes sulfuric acid and polyethylene glycol with a PEG molecular weight of 500 - 20000.

9. The electroplating solution for battery wafers according to any one of claims 1 to 8, characterized in that: The chloride ions are provided by hydrogen chloride.

10. A preparation method of an electroplating solution for battery wafers, characterized in that: It includes the following steps: S1. Directly obtain the configured electrolyte copper salt solution, add the organic acid, and stir until completely dissolved to obtain solution A; S2. Under stirring conditions, add hydrogen chloride to the solution A obtained in step S1, and stir until completely dissolved to obtain solution B; S3. Under stirring conditions, add the brightening agent, the leveling agent, and the leveling agent to the solution B obtained in step S2, and stir until completely dissolved to obtain the electroplating solution for battery wafers as described in any one of claims 1 to 9.

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