Metallization of low-melting-point slurry based on groove capping plate structure

Abstract

The invention discloses metallization of low-melting-point slurry based on a groove capping plate structure, and relates to the field of solar photovoltaic cell manufacturing. According to the metallization method of the low-melting-point slurry based on the groove capping plate structure, firstly, an insulating material is used on the surface of a battery silicon wafer, a groove structure with a preset pattern is formed through silk-screen printing, and then after a groove is solidified, the bottom and the side wall of the groove are covered with low-melting-point alloy slurry. And covering the surface of the low-melting-point slurry with a layer of insulating material, pre-curing, completely coating the slurry, providing physical constraint, and finally carrying out heating curing treatment, so that the low-melting-point slurry forms a continuous dense conductive layer. According to the method, through groove physical confinement and cover plate coating, melting flow of the low-melting-point slurry is restrained, electrode continuity and conductive uniformity are ensured, the problems of oxidation and agglomeration are solved, the low-cost low-melting-point slurry is used for replacing precious metal slurry, the cost of an electrode material is remarkably reduced, and therefore the manufacturing cost of a photovoltaic cell is further reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of solar photovoltaic cell manufacturing, and specifically to the metallization of a low-melting-point paste based on a trench capping structure. Background Art

[0002] Solar cells have been widely used due to their advantages such as environmental friendliness, simple structure, and stable operation, and their proportion in the global energy mix is on the rise. Currently, the electrodes of crystalline silicon solar cells are usually prepared using high-melting-point pastes with relatively high costs, such as silver paste and aluminum paste. Grid lines are directly formed on the silicon substrate through screen printing and can maintain electrical conductivity continuity after curing.

[0003] Traditional high-melting-point pastes have relatively high costs. For example, silver paste accounts for 15%-20% of the total cost of the battery, thus restricting the cost reduction requirements of the photovoltaic industry. For low-cost low-melting-point pastes, due to their low melting points, they are prone to oxidation and molten agglomeration during the curing process, resulting in discontinuous electrodes and decreased electrical conductivity, reducing the conversion efficiency and reliability of the battery. In existing technologies, low-melting-point pastes need to rely on complex processes, such as mask deposition and laser etching, to achieve patterning, so there are problems of high cost, low efficiency, and poor compatibility. In view of the above situation, the present invention provides a metallization of a low-melting-point paste based on a trench capping structure to solve the above problems. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a metallization of a low-melting-point paste based on a trench capping structure, which solves the problem that traditional high-melting-point pastes have relatively high costs. For example, silver paste accounts for 15%-20% of the total cost of the battery, thus restricting the cost reduction requirements of the photovoltaic industry. For low-cost low-melting-point pastes, due to their low melting points, they are prone to oxidation and molten agglomeration during the curing process, resulting in discontinuous electrodes and decreased electrical conductivity, reducing the conversion efficiency and reliability of the battery. In existing technologies, low-melting-point pastes need to rely on complex processes, such as mask deposition and laser etching, to achieve patterning, so there are problems of high cost, low efficiency, and poor compatibility.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A metallization of a low-melting-point paste based on a trench capping structure, and the method steps are as follows;

[0006] Step 1: Select a substrate, and select a crystalline silicon cell required for electrode preparation for processing;

[0007] Step 2: Print trenches, use an epoxy resin insulating glue on the back or front electrode area of the battery silicon wafer, and form a trench structure with a preset pattern through screen printing;

[0008] Step 3: Groove curing. After the printing of the grooves is completed, wait for the epoxy resin insulating glue to solidify to form a physical isolation area;

[0009] Step 4: Printing the paste. Print the low-melting-point copper alloy paste in the grooves, and cover the bottom and side walls of the grooves with the low-melting-point copper alloy paste. The thickness of the paste is the same as the depth of the grooves;

[0010] Step 5: Cover plate printing. Cover a layer of insulating material on the surface of the low-melting-point paste to completely cover the paste and provide physical restraint;

[0011] Step 6: Cover plate curing. The cover plate is pre-cured at 80 - 130 °C for 10 minutes;

[0012] Step 7: Curing treatment. Let the low-melting-point paste melt through the heat treatment curing method, and finally make the low-melting-point paste form a continuous and dense conductive layer.

[0013] Preferably, the process of screen printing the groove structure on the battery silicon wafer in Step 2 is as follows;

[0014] I. Silicon wafer pretreatment. Use plasma cleaning or chemical cleaning to remove the contaminants on the surface of the silicon wafer, and then dry the silicon wafer in a dust-free environment to ensure that there is no moisture residue on the surface;

[0015] II. Screen preparation. The material for making the screen plate is selected as stainless steel or nylon mesh. Apply photosensitive glue on the screen plate, and form a preset groove pattern through UV exposure and development;

[0016] III. Insulating glue preparation. Select the insulating glue material, adjust the viscosity with a solvent, and then remove the particulate impurities through a filter screen;

[0017] IV. Screen printing. Fix the silicon wafer on the vacuum adsorption platform to prevent displacement. Adjust the angle of the squeegee that affects the glue transfer amount to 60 - 75 °. When printing, the squeegee pushes the glue through the openings of the screen plate to form a groove pattern on the surface of the silicon wafer.

[0018] Preferably, the process of groove curing in Step 3 is as follows;

[0019] I. Pre-curing. Use infrared drying to pre-cure at 80 - 160 °C for 10 - 20 minutes to initially fix the shape of the glue;

[0020] II. Post-edge treatment. Remove the overflow glue at the edge of the groove through laser or mechanical means.

[0021] Preferably, the insulating glue material used in Step 2 can select an insulating material with a curing temperature range of 80 °C to 160 °C, high temperature resistance and strong adhesion to solar cell wafers, such as epoxy phenolic resin and ceramic glue.

[0022] Preferably, the width and depth of the groove in the second step are adjusted according to the physical properties of the slurry and the electrode requirements, and the set width range is 25 - 300 μm, and the depth range is 10 - 20 μm.

[0023] Preferably, the selected low melting point alloy slurry in the fourth step is copper alloy, tin alloy and indium alloy slurries with a melting point below 300 °C. The selected low melting point alloy slurry has controllable fluidity and is suitable for screen printing process.

[0024] Preferably, for the selected insulating material in the fifth step, its curing temperature is lower than that of the low melting point alloy slurry, and it has good adhesion to the groove insulating glue material.

[0025] Preferably, in the sixth step, epoxy resin insulating glue is covered by screen printing as the cover plate, and then pre-cured at 130 °C for 10 minutes to complete the curing of the cover plate, so as to ensure that the slurry can maintain continuity and graphic accuracy during curing.

[0026] Preferably, the specific steps of the curing treatment are to heat the groove cover plate structure that has completed the cover plate printing in the atmosphere at 230 °C for 30 s to melt the slurry to form a continuous electrode.

[0027] The present invention discloses a metallization of a low melting point slurry based on a groove cover plate structure, and its beneficial effects are as follows:

[0028] 1. For the metallization of the low melting point slurry based on the groove cover plate structure, through the physical confinement of the groove and the covering of the cover plate, the melting flow of the low melting point slurry is restricted to ensure the continuity of the electrode and the conductivity uniformity, and solve the agglomeration problem.

[0029] 2. For the metallization of the low melting point slurry based on the groove cover plate structure, using low cost low melting point slurry to replace precious metal slurry can significantly reduce the cost of electrode materials.

[0030] 3. For the metallization of the low melting point slurry based on the groove cover plate structure, it is compatible with existing screen printing equipment, does not require complex modification, is suitable for large-scale production, and has process compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained according to these drawings.

[0032] Figure 1 It is a schematic structural diagram of the present invention;

[0033] Figure 2 Schematic diagram of the overall process structure of the present invention;

[0034] Figure 3 Schematic diagram of the screen printing process of the present invention;

[0035] Figure 4 Schematic diagram of the curing of the printed groove of the present invention. Specific embodiments

[0036] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] By providing a metallization of a low-melting-point paste based on a trench capping structure in the embodiments of the present application, the problem that the cost of traditional high-melting-point pastes is relatively high is solved. For example, silver paste accounts for 15%-20% of the total cost of the battery, thus restricting the cost reduction demand of the photovoltaic industry. For low-cost low-melting-point pastes, due to their low melting points, they are prone to oxidation and molten agglomeration during the curing process, resulting in discontinuous electrodes and decreased conductivity, reducing the battery conversion efficiency and reliability. In the existing technology, low-melting-point pastes need to rely on complex process procedures, such as mask deposition, laser etching, etc. to achieve patterning, so there are problems of high cost, low efficiency and poor compatibility.

[0038] To better understand the above technical solutions, the above technical solutions will be described in detail below in conjunction with the accompanying drawings of the specification and specific embodiments.

[0039] The embodiments of the present invention disclose a metallization of a low-melting-point paste based on a trench capping structure.

[0040] According to the attached Figures 1-4 as shown

[0041] The method steps are as follows;

[0042] Step 1: Select a substrate, and select a crystalline silicon cell required for electrode preparation for processing;

[0043] Step 2: Print trenches, use an insulating glue on the back or front electrode area of the battery silicon wafer, and form a trench structure with a preset pattern through screen printing;

[0044] The process of forming a trench structure by screen printing on the battery silicon wafer is as follows;

[0045] I. Wafer pretreatment: Use plasma cleaning or chemical cleaning to remove contaminants on the wafer surface, and then dry the wafer in a dust-free environment to ensure no moisture residue on the surface;

[0046] II. Screen preparation: The material for screen plate production is selected as stainless steel or nylon mesh. Apply photosensitive glue on the screen plate and form a preset groove pattern through UV exposure and development;

[0047] III. Insulating glue preparation: Select insulating glue materials and adjust the viscosity with solvents, and then remove particulate impurities through a filter screen;

[0048] IV. Screen printing: Fix the wafer on a vacuum adsorption platform to prevent displacement. Adjust the angle of the squeegee that affects the glue transfer amount to 60 - 75°. When printing, the squeegee pushes the glue through the openings of the screen plate to form a groove pattern on the wafer surface;

[0049] The insulating glue materials used in the process can select insulating materials with a curing temperature range of 80°C to 160°C, high temperature resistance and strong adhesion to solar cell wafers, such as epoxy phenolic resin and ceramic glue. At the same time, the width and depth of the grooves are adjusted according to the physical properties of the paste and the electrode requirements. The set width range is 25 - 300μm, and the depth range is 10 - 20μm;

[0050] Step III. Groove curing: After the groove printing is completed, wait for the insulating glue to solidify to form a physical isolation area;

[0051] The process of groove curing is as follows;

[0052] I. Pre-curing: Use infrared drying to pre-cure at 80 - 160°C for 10 - 20 minutes to initially fix the groove shape;

[0053] II. Edge trimming post-treatment: Remove the overflow glue at the groove edges through laser or mechanical means;

[0054] Step IV. Printing paste: Print a low-melting-point copper alloy paste in the grooves and cover the bottom and side walls of the grooves with the low-melting-point copper alloy paste. The thickness of the paste is the same as the depth of the grooves. Among them, the selected low-melting-point copper alloy paste has a melting point lower than 300°C, the selected low-melting-point copper alloy paste has controllable fluidity, and is suitable for the screen printing process;

[0055] Step V and Step VI. Cover plate printing and pre-curing of the cover plate: Cover a layer of insulating glue on the surface of the low-melting-point paste to completely cover the paste and provide physical restraint. The selected insulating material has a curing temperature lower than that of the low-melting-point copper alloy paste and has good adhesion to the groove insulating glue material. After covering the insulating material on the epoxy resin insulating glue as the cover plate through the screen printing step, pre-cure the cover plate at 130°C for 10 minutes to ensure that the paste can maintain continuity and pattern accuracy during curing;

[0056] Step 7: Curing treatment. The low-melting-point slurry is melted through a heat treatment curing method, and finally the low-melting-point slurry forms a continuous and dense conductive layer. The specific steps of the curing treatment are to heat the groove cover plate structure that has been completed with cover plate printing in an atmospheric environment at 230°C for 30 s to melt the slurry and form a continuous electrode.

[0057] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A metallization method based on a low melting point slurry with a groove and cover plate structure, characterized in that: The method steps are as follows: Step 1: Select the substrate and the crystalline silicon cell required for electrode preparation for processing; Step 2: Printing grooves: Use insulating glue on the back and front electrode areas of the battery silicon wafer and form a groove structure with a preset pattern by screen printing; Step 3: Groove curing: after the groove is printed, the insulating glue is solidified by heating or ultraviolet irradiation to form a physical isolation area; Step 4: Printing slurry: Printing low melting point alloy slurry in the groove, and covering the bottom and side wall of the groove with the low melting point alloy slurry, and the slurry thickness is consistent with the groove depth; Step 5: Cover plate printing, covering the surface of the low melting point slurry with a layer of insulating glue to completely cover the slurry; Step 6: Curing the cover plate: pre-curing the cover plate at 80-130°C for 10 minutes; Step seven, curing treatment, melting the low melting point slurry through heat treatment curing, and finally forming a continuous and dense conductive layer of the low melting point slurry.

2. The metallization of a low melting point slurry based on a groove and cover plate structure according to claim 1, characterized in that: The process of screen printing the battery silicon wafer to form the groove structure in step 2 is as follows:

1. Pre-treatment of silicon wafers: use plasma cleaning to remove pollutants on the surface of silicon wafers, and then dry the silicon wafers in a dust-free environment to ensure that there is no moisture remaining on the surface; 2. Screen preparation: the screen is made of stainless steel, photosensitive glue is coated on the screen, and a preset groove pattern is formed through UV exposure and development; 3. Preparation of insulating glue: Select the insulating glue material and adjust the viscosity with solvent, then remove the particulate impurities through the filter; 4. Screen printing: fix the silicon wafer on the vacuum adsorption platform to prevent displacement, adjust the scraper angle that affects the amount of glue transfer to 60-75 degrees, and during printing, the scraper pushes the glue through the screen opening to form a preset groove pattern on the surface of the silicon wafer.

3. The metallization of a low melting point slurry based on a groove and cover plate structure according to claim 1, characterized in that: The process of curing the groove in step 3 is as follows:

1. Pre-curing: use infrared drying at 80-160℃ for 10-20 minutes to initially fix the shape of the insulating material; 2. After edge removal, use laser to remove the overflow glue at the edge of the groove.

4. The metallization of a low melting point slurry based on a groove and cover plate structure according to claim 1, characterized in that: The insulating adhesive material used in the step 2 is selected to have a curing temperature range of 100° C. to 160° C., is heat-resistant and has strong adhesion to the solar cell, and the insulating material is epoxy phenolic resin and ceramic adhesive.

5. The metallization of a low melting point slurry based on a groove and cover plate structure according to claim 1, characterized in that: The width and depth of the groove in step 2 are adjusted according to the physical properties of the slurry and the requirements of the electrode, and the width range is set to be 25-300 μm, and the depth range is set to be 10-30 μm.

6. The metallization of a low melting point slurry based on a groove and cover plate structure according to claim 1, characterized in that: The melting point of the low melting point alloy paste selected in the step 4 is lower than 300° C. The fluidity of the selected low melting point alloy paste is controllable and is suitable for screen printing process.

7. The metallization of a low melting point slurry based on a groove and cover plate structure according to claim 1, characterized in that: The insulating material selected in step 5 has a curing temperature lower than that of the low melting point alloy slurry and has good adhesion to the groove insulating material.

8. The metallization of a low melting point slurry based on a groove and cover plate structure according to claim 1, characterized in that: In step six, the cover plate is solidified to ensure that the slurry can maintain continuity and pattern accuracy during solidification.

9. The metallization of a low melting point slurry based on a groove and cover plate structure according to claim 1, characterized in that: The specific step of the curing treatment is to heat the groove cover plate structure after the cover plate printing for 20-50s in an atmosphere of 130-260°C to melt the slurry to form a continuous electrode.

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