A low-temperature laser sintering method for conductive slurry and its application

Abstract

The present invention discloses a low-temperature laser sintering method for a conductive paste and an application thereof, specifically comprising: applying the low-temperature laser sintering technology to the sintering process of a low-silver or silver-free conductive paste, and achieving efficient and uniform conductive layer forming at a relatively low temperature by controlling the frequency, power density and wavelength of the laser, thereby avoiding damage to the material structure caused by high-temperature sintering, effectively improving the conductive properties of the conductive paste, reducing the use of silver, and reducing costs; in addition, the conductive paste is modified by adding a modifier, and in actual applications, a photovoltaic conductive paste with a silver content of 8.5% exhibits excellent conductive properties after laser-assisted sintering.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a low-temperature laser sintering method of a conductive slurry and an application thereof. Background Art

[0002] Compared with TOPCon cells, heterojunction cells have shorter production steps and lower energy consumption, but higher non-silicon costs. Cost reduction and efficiency improvement have always been a focus of all companies in the entire industry chain. Conductive paste is a key material for the manufacture of photovoltaic cells. The quality of conductive paste is directly related to the performance of photovoltaic cells. Therefore, cost reduction and efficiency improvement of conductive paste plays a vital role in the entire photovoltaic industry.

[0003] Traditional silver paste is widely used in solar cells and electronic devices due to its superior conductivity and stability. However, due to the high price of silver, the industry has gradually turned to low-silver paste, silver-coated copper paste and pure copper paste to reduce costs. Despite this, the use of low-silver and silver-free conductive pastes faces problems such as insufficient sintering, unsatisfactory performance of conductive silver paste, large body resistance, reduced efficiency and interface oxidation. In particular, ultra-low silver conductive pastes and copper pastes with a silver content of less than 10% have high resistivity, and the problem of anti-oxidation after printing has not been solved, which has hindered the application of pure copper paste and ultra-low silver conductive paste in heterojunction battery cost reduction. Summary of the invention

[0004] The present invention provides a low-temperature laser sintering method for a conductive paste and an application thereof. The low-temperature laser sintering technology is applied to the sintering process of a low-silver or silver-free conductive paste, so that efficient and uniform conductive layer forming is achieved at a relatively low temperature, damage to the material structure caused by high-temperature sintering is avoided, and the conductive performance of the conductive paste is effectively improved. The modified conductive powder is used in combination with the laser-assisted sintering technology to effectively improve the problems of high resistivity and post-printing anti-oxidation of ultra-low silver-containing conductive paste and pure copper paste. The lower the silver content of the conductive paste, the more obvious the improvement in electrical performance. The efficiency of ultra-low silver-containing conductive paste with a silver content of less than 10% is also significantly improved, and the production cost is greatly reduced.

[0005] A low-temperature laser sintering method for conductive paste, wherein the laser is one of pulsed, continuous and specially modulated lasers, the laser waveband is infrared light wavelength, the silver content of the conductive paste is 0% - 30%; and the sintering temperature is 140 - 260°C.

[0006] Furthermore, the spot shape of the laser is one of circular, square, rectangular, ring, and strip.

[0007] Furthermore, the parameters of the laser include: a repetition frequency of 10 KHz - 5000 KHz, a power density of 0.1 W / μm² - 10 W / μm², a wavelength of 800 nm - 10.6 μm, and a spot size of 15 μm-250 mm.

[0008] Furthermore, a low temperature laser sintering method is used in the preparation of a battery conductive layer, comprising the following steps:

[0009] The conductive paste is printed on the screen and the battery cell is obtained after drying. The line width of the screen is 10 ~ 40 μm, the width of the gate line after printing is 18 ~ 90 μm, and the height of the gate line is 1.5 ~ 20 μm; the drying temperature is 100 ~ 180 ℃, and the time is 1 ~ 30 min.

[0010] The low-temperature laser sintering method sintered the cell, including a laser scanning process, using laser to scan along the printed grid lines, or using laser full coverage scanning, or full coverage direct irradiation; the order of drying and laser scanning can be reversed as needed; the cell is directly used as a finished cell for subsequent processes;

[0011] Optionally, after the treatment is completed, the cell is further cured in a curing oven;

[0012] Optionally, an inert gas or reducing gas atmosphere is used during the laser scanning process, which can improve the electrical performance more significantly.

[0013] Furthermore, the inert gas or reducing gas includes an inert gas or an inert gas-hydrogen mixed gas with an inert gas volume content of 0.5-3.9%; the inert gas includes nitrogen or argon.

[0014] Furthermore, the conductive paste is composed of the following components in weight percentage:

[0015] Conductive powder A 0%-40%, wherein the conductive powder A is spherical silver powder;

[0016] Conductive powder B 50%-90%, wherein the conductive powder B comprises modified silver-coated copper powder and / or modified copper powder with a silver content of 4%-30%;

[0017] Solvent 2%-9%;

[0018] Organic adhesive 2%-8%;

[0019] Additives 1%-7%;

[0020] Conductive powder B is prepared by modifying the powder surface with a modifier;

[0021] The modifier includes one or more of glycerides, fatty acids, amides, alcohols, thiols or esters.

[0022] Furthermore, the silver content of the modified silver-coated copper powder is 4%-25wt%.

[0023] Further, the glycerides include one or more of glyceryl monolaurate, glyceryl monostearate, glyceryl monooleate or glyceryl monocaprylate;

[0024] The fatty acids include one or more of formic acid, isostearic acid, oleic acid, stearic acid, palmitic acid or erucic acid;

[0025] The amides include one or more of N-lauroylsarcosine, erucamide, oleamide, stearamide or palmitamide;

[0026] The alcohols include one or more of oleyl alcohol, tetradecanol, dodecanol or octadecyl alcohol;

[0027] The thiols are one or more of dodecanethiol, dodecylthiophenol, and 2-mercaptobenzothiazole;

[0028] The esters include one or more of sodium formate, isopropyl palmitate, methyl oleate, butyl oleate or ethylhexyl palmitate.

[0029] Furthermore, the preparation method of the conductive powder B includes: dissolving the modifier in ethanol to obtain solution A, the concentration of the mixed solution is 0.05 ~ 0.3 g / mL, adding 10 ~ 40 mL of solution A to every 100 g of conductive powder B, stirring and mixing for 1 ~ 3 h, standing for 10 ~ 12 h, and drying at 80 ° C.

[0030] Furthermore, the specific surface area of ​​the conductive powder B is 0.15 to 3 m 2 / g, D50 is 0.2 ~ 7 μm.

[0031] Furthermore, the specific surface area of ​​the spherical silver powder is 1.5 to 3.0 m 2 / g, D50 is 0.3 ~ 2 μm.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) Compared with competing silver-coated copper powder and copper powder, the modified silver-coated copper powder and modified copper powder used in the present invention have better powder dispersibility, fluidity, stability and antioxidant ability. After the finished slurry is prepared, the slurry has lower fineness, better placement dispersibility and antioxidant ability, better printing fluidity and linearity, and good photoelectric conversion efficiency.

[0034] (2) Ultra-low silver-coated copper paste and pure copper paste with a silver content of 8.5% have greatly improved electrical properties and contact resistance through the assistance of laser sintering, significantly improved efficiency, and greatly reduced production costs. The photovoltaic conductive paste has good stability, printability and conductivity.

[0035] (3) Laser technology, due to its high energy density, rapid heating and precise control, can give the printed grid lines an instantaneous higher temperature, improving sintering without affecting the battery cells. During the sintering process, the order of drying and laser scanning can be reversed as needed.

[0036] (4) The present invention successfully applies laser technology to the low-temperature sintering of silver-coated copper paste and pure copper paste. The laser sintering scheme improves the efficiency of the conductive paste with a silver content of 0% to 93% when applied to heterojunction solar cells, and the bulk resistivity is significantly reduced. In addition, the lower the silver content, the worse the electrical performance and the more obvious the improvement. This scheme can greatly improve the efficiency of ultra-low silver conductive paste with a silver content of less than 10%, greatly reducing the cost of the paste. This scheme has a ten to twenty-fold gain in the electrical performance of pure copper paste.

[0037] (5) Laser scanning in an inert gas or reducing gas atmosphere can significantly improve the electrical properties of photovoltaic conductive pastes. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is an electron microscope image of the 5% silver-containing silver-coated copper powder described in Example 1;

[0039] Figure 2 This is an electron microscope image of a grid line cross section after printing with a silver-clad copper paste containing 8.5% silver as described in Example 1;

[0040] Figure 3 This is an electron microscope image of a grid line cross section after printing with a silver-clad copper paste containing 49.2% silver as described in Example 2;

[0041] Figure 4 is an electron microscope image of the modified spherical pure copper powder described in Example 5;

[0042] Figure 5 is an electron microscope image of the modified flaky pure copper powder described in Example 5;

[0043] Figure 6 This is an electron microscope image of the cross section of the gate line after printing with the pure copper paste system described in Example 5. DETAILED DESCRIPTION

[0044] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention. Example 1

[0045] An appropriate amount of glyceryl monostearate was dissolved in ethanol and stirred thoroughly to obtain a mixed solution with a concentration of 0.2 g / mL. 25 mL of the mixed solution was added to every 100 g of silver-coated copper powder, stirred for 3 h, allowed to stand for 12 h, and dried at 80 °C to obtain spherical modified silver-coated copper powder with a silver content of 5%. The scanning electron microscope image of the modified silver-coated copper powder is shown in FIG. Figure 1 shown.

[0046] A photovoltaic conductive paste, the composition of which, calculated by mass percentage, includes: a particle size D50 of 0.5 μm, a specific surface area of ​​2.3 m 2 / g of spherical silver powder 4%, particle size D50 is 3.8μm, specific surface area is 0.2 m 2 / g of spherical modified silver-coated copper powder is 86%, the solvent diethylene glycol butyl ether is used in an amount of 3.2%, the polyurethane oligomer is used in an amount of 2.5%, the polyester resin with an average molecular weight of 30,000 is used in an amount of 2.5%, the imidazole curing agent is used in an amount of 0.5%, the leveling agent polyamide wax is used in an amount of 0.5%, and the hydrogenated castor oil used as a dispersant is used in an amount of 0.8%; after the organic mixture is evenly mixed, silver powder and modified silver-coated copper powder are added, and the mixture is evenly dispersed by a homogenizer. The theoretical total silver content of the system is 8.3%, and the actual tested silver content is 8.5%.

[0047] The prepared photovoltaic conductive paste was screen printed with a line width of 20 μm. The printed cells were dried in a drying oven at 160 ℃ ~ 180 ℃ for 2 min. Secondly, the dried cells were scanned along the printed grid lines with a laser. Finally, the finished cells were cured in a curing oven. The cross-sectional electron microscope image of the grid lines after printing the silver-coated copper paste with an 8.5% silver content is shown in Figure 2 shown. Example 2

[0048] An appropriate amount of oleic acid amide was dissolved in ethanol and stirred thoroughly to obtain a mixed solution with a concentration of 0.2 g / mL. 30 mL of the mixed solution was added to every 100 g of silver-coated copper powder. The mixture was stirred for 3 h, allowed to stand for 12 h, and dried at 80 °C to obtain modified silver-coated copper powder. The silver content of the modified silver-coated copper powder was 18%.

[0049] A photovoltaic conductive paste, the composition of which, calculated by mass percentage, includes: a particle size D50 of 0.53 μm, a specific surface area of ​​2.1 m 2 / g of spherical silver powder 40%, particle size D50 is 3.7 μm, specific surface area is 0.26 m 2 / g of modified silver-coated copper powder 51%, solvent pineol dosage is 1.5%, diethylene glycol dibutyl ether dosage is 1.1%, epoxy resin with epoxy equivalent of 160 ~ 180 is 2.5%, polyurethane prepolymer dosage is 2%, imidazole curing agent dosage is 0.6%, leveling agent fumed silica dosage is 0.4%, oleic acid dosage as dispersant and defoaming agent is 0.5%, polyacrylic acid dosage is 0.4%; after organic mixing is uniform, modified silver-coated copper powder is subsequently added, and after uniform dispersion, silver powder is added and dispersed evenly by homogenizer. The theoretical total silver content of the system is 49.2%.

[0050] The prepared photovoltaic conductive paste was screen printed with a line width of 17 μm. The printed cells were dried in a drying oven at 150 ℃ ~ 170 ℃ for 3 min. Secondly, the dried cells were scanned along the printed grid lines with a laser. Finally, the finished cells were cured in a curing oven. The cross-sectional electron microscope image of the grid lines after printing the silver-coated copper paste with a silver content of 49.2% is shown in Figure 3 shown. Example 3

[0051] An appropriate amount of N-lauroylsarcosine was dissolved in ethanol and stirred thoroughly to obtain a mixed solution with a concentration of 0.3 g / mL. 25 mL of the mixed solution was added to every 100 g of silver-coated copper powder. The mixture was stirred for 3 h, allowed to stand for 12 h, and dried at 80 °C to obtain modified silver-coated copper powder. The silver content of the modified silver-coated copper powder was 5.5%.

[0052] A photovoltaic conductive paste, the composition of which, calculated by mass percentage, includes: a particle size D50 of 0.51 μm, a specific surface area of ​​2.7 m 2 / g of spherical silver powder 13%, particle size D50 is 5.3 μm, specific surface area is 0.15 m 2 / g modified silver-coated copper powder 77.5%, solvent diethylene glycol butyl ether acetate dosage is 1.9%, pine alcohol dosage is 2%, epoxy resin with epoxy equivalent of 160 ~ 180 dosage is 2.1%, modified acrylic resin with molecular weight of 5000 ~ 30000 dosage is 1.2%, boron amine curing agent dosage is 0.7%, leveling agent polydimethylsiloxane and polyamide wax are used 0.5% respectively, and hydrogenated castor oil as dispersant and defoamer dosage is 0.6%. After organic mixing, modified silver-coated copper powder is added, and after uniform dispersion, silver powder is added and uniformly dispersed by homogenizer. The theoretical total silver content of the system is 17.27%, and the actual tested silver content is 17.46%.

[0053] The prepared photovoltaic conductive paste is screen-printed with a line width of 20 μm. The printed cells are dried in a drying oven at 140°C to 170°C for 3 min. Secondly, the dried cells are scanned along the printed grid lines with a laser. Finally, the cells are cured in a curing oven to obtain the finished cells. Example 4

[0054] An appropriate amount of palmitamide was dissolved in ethanol and stirred thoroughly to obtain a mixed solution with a concentration of 0.2 g / mL. 25 mL of the mixed solution was added to every 100 g of silver-coated copper powder. The mixture was stirred for 3 h, allowed to stand for 12 h, and dried at 80 °C to obtain modified silver-coated copper powder. The silver content of the modified silver-coated copper powder was 14%.

[0055] A photovoltaic conductive paste, the composition of which, calculated by mass percentage, includes: a particle size D50 of 0.7 μm, a specific surface area of ​​1.8 m 2 / g of spherical silver powder 25%, particle size D50 is 4.9 μm, specific surface area is 0.23 m 2 / g of modified blocky silver-coated copper powder is 66%, solvent diethylene glycol butyl ether acetate is used in an amount of 1.5%, dibasic acid ester is used in an amount of 2%, epoxy resin with an epoxy equivalent of 160 to 180 is used in an amount of 2.9%, boron amine curing agent is used in an amount of 0.3%, polyurethane prepolymer is used in an amount of 2%, leveling agent polyether polyester modified organic siloxane is used in an amount of 0.5%, oleic acid as a dispersant and defoaming agent is used in an amount of 0.5%, and turpentine is used in an amount of 0.4%. After the organic mixture is evenly mixed, the modified silver-coated copper powder is subsequently added, and after it is evenly dispersed, the silver powder is added, and the mixture is evenly dispersed by a homogenizer. The theoretical total silver content of the system is 34.9%.

[0056] The prepared photovoltaic conductive paste was screen-printed using a 14 μm line width steel mesh. The printed cells were scanned along the printed grid lines using a laser. After scanning, the cells were dried in a drying oven at 150°C to 180°C for 3 minutes. Example 5

[0057] An appropriate amount of glycerol monolaurate was dissolved in ethanol and stirred thoroughly to obtain a mixed solution with a concentration of 0.2 g / mL. 25 mL of the mixed solution was added to every 100 g of spherical copper powder, stirred for 3 h, allowed to stand for 12 h, and dried at 80 °C to obtain modified spherical copper powder. The scanning electron microscope image of the modified spherical copper powder is shown in FIG. Figure 4 shown.

[0058] An appropriate amount of formic acid was dissolved in ethanol and stirred thoroughly to obtain a mixed solution with a concentration of 0.25 g / mL. 25 mL of the mixed solution was added to every 100 g of flaky copper powder, stirred for 3 h, allowed to stand for 12 h, and dried at 80 °C to obtain modified flaky copper powder. The scanning electron microscope image of the modified flaky copper powder is shown in FIG. Figure 5 shown.

[0059] A photovoltaic conductive paste, the composition of which, calculated by mass percentage, includes: a particle size D50 of 0.5 μm, a specific surface area of ​​2.7 m 2 / g modified spherical copper powder 53%, flake diameter D50 is 3.4 μm, specific surface area is 0.58 m 2 / g of modified flaky copper powder 33%, solvent diethylene glycol butyl ether acetate and pine alcohol (volume ratio of 1:1) usage 3.8%, average molecular weight of phenoxy resin about 50000 usage 3.5%, epoxy resin with epoxy equivalent of 160 ~ 180 usage 2.3%, polyurethane prepolymer usage 2.2%, dicyandiamide curing agent usage 0.8%, leveling agent polyamide wax usage 0.8%, oleic acid usage as dispersant usage 0.6%, organic mixing evenly, then add modified flaky copper powder and modified spherical copper powder, homogenizer dispersed evenly.

[0060] The prepared photovoltaic conductive paste was screen printed with a 30 μm line width. The printed cells were dried in a drying oven at 120 ℃ ~ 150 ℃ for 3 min. Secondly, the dried cells were scanned along the printed grid lines with a laser. The cross-sectional electron microscope image of the grid lines after the pure copper paste was printed is shown in Figure 2. Figure 6 shown. Example 6

[0061] An appropriate amount of erucic acid amide was dissolved in ethanol and stirred thoroughly to obtain a mixed solution with a concentration of 0.2 g / mL. 30 mL of the mixed solution was added to every 100 g of silver-coated copper powder. The mixture was stirred for 3 h, allowed to stand for 12 h, and dried at 80 °C to obtain spherical modified silver-coated copper powder.

[0062] A photovoltaic conductive paste, the composition of which, calculated by mass percentage, includes: a particle size D50 of 0.4 μm, a specific surface area of ​​2.5 m 2 / g of spherical silver powder 4%, particle size D50 is 4.8μm, specific surface area is 0.2 m 2 / g of spherical modified silver-coated copper powder is 86%, the solvent diethylene glycol butyl ether is used in an amount of 3.1%, the polyurethane oligomer is used in an amount of 2.8%, the polyester resin with an average molecular weight of 30,000 is used in an amount of 2.2%, the imidazole curing agent is used in an amount of 0.4%, the leveling agent polyamide wax is used in an amount of 0.7%, and the hydrogenated castor oil used as a dispersant is used in an amount of 0.8%; after the organic mixture is evenly mixed, silver powder and modified silver-coated copper powder are added, and the mixture is evenly dispersed by a homogenizer. The theoretical total silver content of the system is 8.3%, and the actual tested silver content is 8.4%.

[0063] This embodiment provides the application of the above-mentioned photovoltaic conductive paste in low-temperature sintering, and the operating steps are as follows: the prepared photovoltaic conductive paste is subjected to conventional screen printing with a line width of 20 μm, and the printed solar cell is dried in a drying furnace at 120°C~150°C for 3 min; secondly, the dried solar cell is directly irradiated with a laser for 1~2 seconds in a nitrogen atmosphere to obtain a finished solar cell.

[0064] Comparative Example 1

[0065] The silver-clad copper paste with 50%~54% silver content in the market is XHT-2AF-102TS01; through conventional screen printing with a line width of 20 μm, the printed battery cells are dried in a drying furnace at 120℃~150℃ for 3 minutes; secondly, the dried battery cells are directly irradiated with laser for 1~2 seconds in a nitrogen atmosphere to obtain the finished battery cells.

[0066] Comparative Example 2

[0067] The first-line silver-coated copper paste with a silver content of 38%~42% on the market is AC-101-A16F02; through conventional screen printing with a line width of 20 μm, the printed battery cells are dried in a drying furnace at 120℃~150℃ for 3 minutes; secondly, the dried battery cells are directly irradiated with laser for 1~2 seconds in a nitrogen atmosphere to obtain finished battery cells.

[0068] Comparative Example 3

[0069] Conductive silver paste, silver content 93%, Ag-101-A02B02; through 20 μm line width conventional screen printing, the printed battery cell is dried in a drying furnace at 120 ℃ ~ 150 ℃ for 3 min; secondly, the dried battery cell is directly irradiated with laser for 1~2 seconds in a nitrogen atmosphere to obtain a finished battery cell.

[0070] Comparative Example 4

[0071] A photovoltaic conductive paste, the composition of which, calculated by mass percentage, includes: a particle size D50 of 0.6 μm, a specific surface area of ​​2.1 m 2 / g of spherical silver powder 46%, flake diameter D50 is 2.9 μm, specific surface area is 0.45 m 2 / g of flaky silver powder is 45.5%, solvent diethylene glycol butyl ether and dimethyl adipate (1:1) is used in an amount of 3.4%, phenoxy resin with an average molecular weight of 30000 is used in an amount of 1.5%, epoxy resin with an epoxy equivalent of 160 to 180 is used in an amount of 1.8%, boron amine curing agent is used in an amount of 0.7%, leveling agent fumed silica is used in an amount of 0.5%, oleic acid and polyethylene glycol (1:1) as dispersants are used in an amount of 0.6%. After the organic mixture is evenly mixed, spherical silver powder and flaky silver powder are subsequently added and dispersed evenly by a homogenizer. The theoretical total silver content of the system is 91.5%.

[0072] The prepared photovoltaic conductive paste is screen-printed with a line width of 20 μm, and the printed cells are dried in a drying oven at 160 °C for 3 min. Secondly, the dried cells are scanned along the printed grid lines with a laser, and finally, the cells are cured in a curing oven to obtain the finished cells.

[0073] Performance Testing

[0074] The photovoltaic conductive pastes in Examples 1 to 6 and the conductive pastes in Comparative Examples 1 to 4 were subjected to performance tests. The silver content was detected by titration experiments to detect the silver content before and after laser-assisted sintering. The resistivity test was to test the resistivity change of the grid line before and after laser sintering using a resistivity tester. The total wet weight of the front and back auxiliary materials was detected by the difference method to detect the weight change of a single piece before and after printing, and 5 pieces were measured and the average value was taken. The photoelectric conversion efficiency was measured by Maxwell's heterojunction screen printing equipment to measure the photoelectric conversion efficiency, and 20 pieces were measured and the average value was taken. The test results are shown in Table 1.

[0075] Table 1

[0076]

[0077] The photovoltaic conductive pastes in Examples 1 to 6 and the pastes in Comparative Examples 1 to 4 were subjected to bare chip DH experiments and acid mist experiments. The bare chip DH experiment specifically involved taking the printed and cured sheets, placing them directly into a DH cabinet, monitoring the efficiency decay for 72 hours, measuring 5 sheets per group, and taking the average value. The acid mist experiment specifically involved taking the printed and cured sheets, placing them directly into an acid mist box, soaking them for 3 hours, testing the change values, measuring 5 sheets per group, and taking the average value. The test results are shown in Table 2.

[0078] analyze:

[0079] It can be seen from the table that, according to the comparison between the embodiments and the comparative examples, the laser-assisted sintering provided by the present invention improves the efficiency of the conductive paste with a silver content of 0% to 93% tested for application in heterojunction solar cells, and the volume resistivity is significantly reduced; in addition, the lower the silver content, the worse the electrical performance, and the more obvious the improvement; through this solution, the efficiency of the conductive paste with an ultra-low silver content of less than 10% can be greatly improved, greatly reducing the cost of the paste.

[0080] By comparing Example 1 with Example 6, it can be seen that the electrical performance of the heterojunction solar cell is further improved under the inert gas atmosphere. This solution has a ten- to twenty-fold gain in the electrical performance of the pure copper slurry, and the efficiency is significantly improved. In addition, the results of the acetic acid mist test and the bare chip DH test show that the power attenuation is basically the same before and after the laser is applied.

[0081] Table 2

[0082]

Claims

1. A method for low temperature laser sintering of conductive paste, characterized in that: The laser is one of a continuous laser and a modulated laser, the laser waveband is an infrared light wavelength, the silver content of the conductive paste is in the range of greater than 0% and less than or equal to 8.4%; the sintering temperature is 140-260°C, and the parameters of the laser include: a repetition frequency of 10 KHz-5000 KHz, a power density of 0.1 W / μm²-10 W / μm², a wavelength of 800 nm-10.6 μm, and a spot size of 15 μm-250 mm; The method comprises the following steps: printing a conductive paste on a screen, and obtaining a battery cell after drying, wherein the line width of the screen is 10 to 40 μm, the line width of the gate line after printing is 18 to 90 μm, and the line height of the gate line is 1.5 to 20 μm; The low-temperature laser sintering method for sintering the cell includes a laser scanning process, which uses a laser to scan along the printed grid lines, or uses a laser to scan the entire area, or directly irradiate the entire area; After the treatment, the cell is further cured in a curing oven; An inert gas or reducing gas atmosphere is used during laser scanning; The inert gas or reducing gas includes an inert gas or an inert gas-hydrogen mixed gas with an inert gas volume content of 0.5-3.9%; the inert gas includes nitrogen or argon; the conductive paste is composed of the following components in weight percentage: The conductive powder A is greater than 0% and less than or equal to 40%, and the conductive powder A is spherical silver powder; Conductive powder B 50%-90%, wherein the conductive powder B comprises modified silver-coated copper powder and / or modified copper powder with a silver content of 4%-30%; Solvent 2%-9%; Organic adhesive 2%-8%; Additives 1%-7%; Conductive powder B is prepared by modifying the powder surface with a modifier; The modifier includes one or more of glycerides, fatty acids, amides, alcohols, and thiols.

2. The method according to claim 1, characterized in that: The modified silver-coated copper powder has a silver content of 4%-25wt%.

3. The method according to claim 1, characterized in that The glycerides include one or more of glyceryl monolaurate, glyceryl monostearate, glyceryl monooleate or glyceryl monocaprylate; The fatty acids include one or more of formic acid, isostearic acid, oleic acid, stearic acid, palmitic acid or erucic acid; The amides include one or more of N-lauroylsarcosine, erucamide, oleamide, stearamide or palmitamide; The alcohols include one or more of oleyl alcohol, tetradecanol, dodecanol or octadecyl alcohol; The thiols are one or more of dodecanethiol, dodecylthiophenol and 2-mercaptobenzothiazole.

4. The method according to claim 1, characterized in that The preparation method of the conductive powder B comprises: dissolving a modifier in ethanol to obtain a solution A, wherein the concentration of the mixed solution is 0.05 to 0.3 g / mL, adding 10 to 40 mL of the solution A to every 100 g of the conductive powder B, stirring and mixing for 1 to 3 hours, allowing the mixture to stand for 10 to 12 hours, and drying at 80°C.

5. The method according to claim 1, characterized in that The specific surface area of ​​the conductive powder B is 0.15 ~ 3 m 2 / g, D50 is 0.2 ~ 7 μm.

6. The method according to claim 1, characterized in that The specific surface area of ​​the spherical silver powder is 1.5 to 3.0 m 2 / g, D50 is 0.3 ~ 2 μm.

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