CN110549030A - low-temperature solder for photovoltaic solder strip of HIT heterojunction and preparation method - Google Patents
low-temperature solder for photovoltaic solder strip of HIT heterojunction and preparation method Download PDFInfo
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- CN110549030A CN110549030A CN201910781856.XA CN201910781856A CN110549030A CN 110549030 A CN110549030 A CN 110549030A CN 201910781856 A CN201910781856 A CN 201910781856A CN 110549030 A CN110549030 A CN 110549030A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
- B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering, brazing
- B23K35/0227—Rods, wires
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/26—Selection of soldering or welding materials proper with the principal constituent melting at less than 400 degrees C
- B23K35/262—Sn as the principal constituent
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/40—Making wire or rods for soldering or welding
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Abstract
The invention relates to a low-temperature solder for a photovoltaic solder strip of an HIT heterojunction and a preparation method thereof, wherein the low-temperature solder comprises the following steps: the method comprises the following steps: the solder is prepared from the following raw materials in percentage by mass: 35 to 40 percent of bismuth, 1.5 to 2.5 percent of silver powder, 0.01 to 0.02 percent of copper and the balance of tin. According to the invention, the conductive materials such as spherical silver powder and the like are adopted to be the same as the silver paste of the grid line of the battery piece, and the components and the grade size of the particles are within a specification range, so that eutectic transformation is promoted even under the condition of low-temperature welding, the intermediate compound of the metal at the electrode interface is formed more uniformly and compactly, and the network contact of the conductive phase is more perfect, so that the conductivity, the adhesive force (namely the welding tension) and the reliability (namely TC200 and DH1000) of the silver electrode are effectively improved, and the solder does not use harmful elements such as lead and cadmium, and completely meets the requirement of environmental.
Description
Technical Field
The invention relates to the field of solder and a preparation method thereof, in particular to low-temperature solder for a photovoltaic solder strip of an HIT heterojunction and a preparation method thereof.
Background
The total world power consumption has been kept increasing about 1-fold every 10 years, i.e. an average annual growth rate of about 7.2%. In 1975, the world's total primary energy consumption was 87.5 billion tons of standard coal, which was used as about 25% of electricity generation; the coal-fired power generation is stopped, the dust pollution is firstly reduced, the current haze, the greenhouse effect and the like are decisive, and the green economy is taken as the core competitiveness of the national development strategy and the global position at present and even in the future. In 2018, the global hydroelectric power generation capacity is about 16%, the nuclear power generation capacity is about 10%, the wind power generation capacity is about 5%, and the solar photovoltaic power generation capacity is only about 2%; it is expected that solar photovoltaic power generation will exceed coal as the primary power supply by 2034 and will cover 52% of the power demand in the region by 2050.
Under the stimulation of the Chinese '531' policy, China has rapidly led global technical progress and industry cost reduction, efficiency improvement and healthy development, and all countries are promoted to gradually enter the 'solar photovoltaic power generation flat time'. Particularly, in recent years, the application of technologies such as diamond wire cutting and the like and the large-scale mass production of PERC batteries promote the rapid improvement of the product performance and the rapid reduction of the cost in 2017 to 2018, the rapid development of assembly technologies such as double-sided, half-sheet, MBB, lamination and the like is expected, the development of photovoltaic battery technologies will be led by battery technologies such as N-type batteries, PERC batteries, Topcon, HIT (heterojunction) and the like, and the PERC batteries, Topcon, HIT (heterojunction) and the like are the main development directions of the future battery technologies. In 2011-2018, the prices of the photovoltaic module and the inverter are reduced by over 75%, and the cost of the system is reduced by about 72% under the promotion of the reduction. In general, the annual system cost in 2019 has a reduction space of about 0.5 yuan/W; in 2018, the price of the photovoltaic module is reduced by about 0.8 yuan/W. The cost of the cell is more than 60% of the cost of the assembly, the yield of 1kg of silicon material of the single crystal assembly is increased from 58 pieces to 64 pieces, and the cost of a single silicon wafer can be reduced, so that the cell or the silicon wafer becomes the largest space for reducing the cost, the links of the silicon wafer or the cell (the cost of the silicon wafer material is reduced, namely the thickness of the cell is 230um to the current 180um and 150um, and even is less than 100um in the future, and the cost of the silver paste of the cell is reduced, namely the silver content is reduced or the component range is enlarged) are adopted, the technical progress and the cost reduction trend of the thinning and the rough components of the grid line of the cell are obvious, and further technical innovation and urgent needs of the photovoltaic solder are brought.
In fact, in combination with international recognition of environmental protection and flaking, the "heterojunction" flaking soldering process which goes on in the front has no soldering tension or no lead-free environmental protection low temperature photovoltaic solder strip solder with mature reliability, wherein the tin-lead Sn-Pb solder series of several years ago is still used, resulting in a series of problems occurring during the component production process or after the system installation: the welding tension is less than 0.5N, the welding temperature is too high, the subfissure is high, the thermal cycle test TC200 and the damp-heat test DH1000 are attenuated by more than 5%, and the like. Patent numbers: 201910252298.8 discloses a low temperature lead-free alloy solder and its preparation method, the low temperature lead-free alloy solder comprises the following raw materials by weight: in 18-24%, Bi 2-5%, Sb0.1-0.4%, Cu0.1-0.7%, Ce0.02-0.06% and the balance Sn. Although the technical requirement of using the low-temperature lead-free alloy solder in the lead-free manufacturing process in the electronic industry is met to a certain extent and relevant regulations on energy conservation, emission reduction and environmental protection are practiced, the specific performance of the solder is not improved in a large range. Therefore, there is a need for a low temperature solder that has good performance and meets the requirements of work and use.
Disclosure of Invention
The invention aims to provide the low-temperature solder for the photovoltaic solder strip of the HIT heterojunction, which has the advantages of low welding melting point, welding tension of more than 1.5N/mm, thermal cycle test TC200 and damp-heat test DH1000 attenuation of less than 5%, and the like.
In order to overcome the problems of poor performance and the like in the existing solder, the invention relates to a low-temperature solder for a photovoltaic solder strip of an HIT heterojunction and a preparation method thereof, wherein the low-temperature solder comprises the following steps: the solder is prepared from the following raw materials in percentage by mass: 35 to 40 percent of bismuth, 1.5 to 2.5 percent of silver powder, 0.01 to 0.02 percent of copper and the balance of tin.
the invention has the beneficial effects that the conductive materials such as spherical silver powder and the like are adopted to be the same as the silver paste of the grid line of the battery piece, the components and the grade size of the particles are adopted to be within a specification range, eutectic transformation is promoted even under the condition of low-temperature welding, so that the metal intermediate compound at the electrode interface is formed more uniformly and compactly, and the network contact of the conductive phase is more perfect, thereby effectively improving the conductive performance, the adhesive force (namely welding pull force) and the reliable performance (namely TC200 and DH1000) of the silver electrode, and the solder completely meets the requirement of environmental protection because the solder does not use harmful elements such as lead, cadmium and the like.
Furthermore, the solder is prepared from the following raw materials, by mass, 37-39% of bismuth, 1.5-2.5% of silver powder, 0.01-0.02% of copper and the balance of tin. The amount of bismuth added during the synthesis is limited because it has a very damaging effect on fatigue life and plasticity, and therefore, the content thereof is controlled.
Further, the silver powder is spherical silver powder; the purity of the silver powder is more than 99.90%, and the D50 is 0.8-2.0 μm.
Further, the purity of the copper is more than 99.97%.
Further, the purity of the bismuth is more than 99.95%.
further, the tin comprises tin ingots and tin particles; the purity of the tin is greater than 99.95%.
A low-temperature solder preparation method for a photovoltaic solder strip of an HIT heterojunction comprises the following sequential steps:
S1, accurately weighing the tin particles and the silver powder according to the weight ratio of the formula, uniformly mixing the materials in a planetary high-speed stirrer with rotation and revolution functions, uniformly ball-milling, pouring out, suction-filtering, drying in vacuum at low temperature, forming intermediate alloy tin-silver-copper Sn-Ag with required appearance quality by high-temperature diffusion sintering and isostatic pressing, and storing at 10-20 ℃ and 45 +/-5% humidity for later use
S2, adding tin ingots with the purity of more than 99.95 percent and bismuth according to the required alloy proportion into a vacuum melting furnace under the protection of nitrogen, heating to the temperature of 280-plus-340 ℃ for melting, adding a hook-type copper plate with the purity of more than 99.95 percent for hot-melting tin, preserving the heat for 40-60 minutes, removing surface tin slag, taking out a copper strip, cooling to the temperature of 220-plus-230 ℃ for stirring for 15-30 minutes, removing the surface tin slag again to obtain the Sn-Bi-Cu leadless low-temperature basic solder mixed solution
S3: and adding the Sn-Ag-Cu Sn-Ag intermediate alloy prepared in the step S1 into the mixed solution in the step S2 according to the required proportion, heating to 400-plus-460 ℃ under the protection of nitrogen, preserving heat and stirring for 30 minutes, removing surface tin slag, cooling to 220 ℃, preserving heat and stirring for 10 minutes, cooling to 170-180 ℃, preserving heat and stirring for 10 minutes, and filtering into a tin bar grinding tool through a honeycomb carbon net to finish casting.
In practice, in the present solution, the three-layer weld face composition description, which is basically involved in the reaction of the components, is defined as follows:
Weld face (inlayer), the grid line silver thick liquid face of welding that needs to be by welded heterojunction HIT class ultra-thin battery piece contains: additives such as silver powder, glass powder and organic carriers;
the solder (the middle layer) is the solder researched by the invention (the red copper wrapping the following outer layer is the photovoltaic solder strip);
copper base (outer layer): heat treated red copper of 99.95% purity.
In the technical scheme, the research mechanism of the solder is combined with the three-layer welding layer structure and the component research: the brazing process is a diffusion reaction process of metal elements of a solder matrix to gaps of a welding surface, and intermetallic compound particles formed among three layers of welding surfaces form an intercrystalline metal bond energy equilibrium state; based on the binary phase diagram of Sn/Ag and Sn/Cu, the interaction between silver and tin forms an intermetallic compound of Ag3Sn, copper reacts with tin to form an intermetallic compound of Cu6Sn5, and bismuth plays a major role in further reducing the melting temperature. However, the amount of bismuth which can be added is limited because the bismuth has great destructive effect on fatigue life and plasticity, and the addition of silver can reduce the melting temperature and simultaneously improve the wettability and plasticity of the solder, so that the fatigue life of the solder for welding three-layer welding surfaces is improved (representing reliability aging tests: TC200, DH1000 and the like) by preparing eutectic alloy for Ag, Cu, Sn and Bi according to the solid-liquid phase temperature formed by the balanced preparation of quaternary systems of various element proportions, and the temperature range of the welding melting point of the heterojunction HIT type ultrathin battery piece required by matching is reached.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a statistical table of experimental data of solder alloy implementation of a control group and an experimental group of a solder preparation method for a photovoltaic solder strip of an HIT heterojunction according to the present invention;
FIG. 2 is a data statistical table of EL test experiment data of solder alloys of a control group and an experimental group of the solder preparation method of the photovoltaic solder strip for the HIT heterojunction according to the invention;
FIG. 3 is a melting point test chart of a solder alloy prepared by the solder preparation method for the photovoltaic solder strip of the HIT heterojunction.
Detailed Description
The present invention will be further described in detail with reference to the following specific examples:
The invention aims to provide the low-temperature solder for the photovoltaic solder strip of the HIT heterojunction, which has the advantages of low welding melting point, welding tension of more than 1.5N/mm, thermal cycle test TC200 and damp-heat test DH1000 attenuation of less than 5%, and the like.
In order to overcome the problems of poor performance and the like in the existing solder, the invention relates to a low-temperature solder for a photovoltaic solder strip of an HIT heterojunction and a preparation method thereof, wherein the low-temperature solder comprises the following steps: the solder is prepared from the following raw materials in percentage by mass: 35 to 40 percent of bismuth, 1.5 to 2.5 percent of silver powder, 0.01 to 0.02 percent of copper and the balance of tin.
The invention has the beneficial effects that the conductive materials such as spherical silver powder and the like are adopted to be the same as the silver paste of the grid line of the battery piece, the components and the grade size of the particles are adopted to be within a specification range, eutectic transformation is promoted even under the condition of low-temperature welding, so that the metal intermediate compound at the electrode interface is formed more uniformly and compactly, and the network contact of the conductive phase is more perfect, thereby effectively improving the conductive performance, the adhesive force (namely welding pull force) and the reliable performance (namely TC200 and DH1000) of the silver electrode, and the solder completely meets the requirement of environmental protection because the solder does not use harmful elements such as lead, cadmium and the like.
Furthermore, the solder is prepared from the following raw materials, by mass, 37-39% of bismuth, 1.5-2.5% of silver powder, 0.01-0.02% of copper and the balance of tin. The amount of bismuth added during the synthesis is limited because it has a very damaging effect on fatigue life and plasticity, and therefore, the content thereof is controlled.
Further, the silver powder is spherical silver powder; the purity of the silver powder is more than 99.90%, and the D50 is 0.8-2.0 μm.
Further, the purity of the copper is more than 99.97%.
Further, the purity of the bismuth is more than 99.95%.
Further, the tin comprises tin ingots and tin particles; the purity of the tin is greater than 99.95%.
A low-temperature solder preparation method for a photovoltaic solder strip of an HIT heterojunction comprises the following sequential steps:
S1, accurately weighing the tin particles and the silver powder according to the weight ratio of the formula, uniformly mixing the materials in a planetary high-speed stirrer with rotation and revolution functions, uniformly ball-milling, pouring out, suction-filtering, drying in vacuum at low temperature, forming intermediate alloy tin-silver-copper Sn-Ag with required appearance quality by high-temperature diffusion sintering and isostatic pressing, and storing at 10-20 ℃ and 45 +/-5% humidity for later use
S2, adding tin ingots with the purity of more than 99.95 percent and bismuth according to the required alloy proportion into a vacuum melting furnace under the protection of nitrogen, heating to the temperature of 280-plus-340 ℃ for melting, adding a hook-type copper plate with the purity of more than 99.95 percent for hot-melting tin, preserving the heat for 40-60 minutes, removing surface tin slag, taking out a copper strip, cooling to the temperature of 220-plus-230 ℃ for stirring for 15-30 minutes, removing the surface tin slag again to obtain the Sn-Bi-Cu leadless low-temperature basic solder mixed solution
S3: and adding the Sn-Ag-Cu Sn-Ag intermediate alloy prepared in the step S1 into the mixed solution in the step S2 according to the required proportion, heating to 400-plus-460 ℃ under the protection of nitrogen, preserving heat and stirring for 30 minutes, removing surface tin slag, cooling to 220 ℃, preserving heat and stirring for 10 minutes, cooling to 170-180 ℃, preserving heat and stirring for 10 minutes, and filtering into a tin bar grinding tool through a honeycomb carbon net to finish casting.
In practice, in the present solution, the three-layer weld face composition description, which is basically involved in the reaction of the components, is defined as follows:
Weld face (inlayer), the grid line silver thick liquid face of welding that needs to be by welded heterojunction HIT class ultra-thin battery piece contains: additives such as silver powder, glass powder and organic carriers;
The solder (the middle layer) is the solder researched by the invention (the red copper wrapping the following outer layer is the photovoltaic solder strip);
Copper base (outer layer): heat treated red copper of 99.95% purity.
In the technical scheme, the research mechanism of the solder is combined with the three-layer welding layer structure and the component research: the brazing process is a diffusion reaction process of metal elements of a solder matrix to gaps of a welding surface, and intermetallic compound particles formed among three layers of welding surfaces form an intercrystalline metal bond energy equilibrium state; based on the binary phase diagram of Sn/Ag and Sn/Cu, the interaction between silver and tin forms an intermetallic compound of Ag3Sn, copper reacts with tin to form an intermetallic compound of Cu6Sn5, and bismuth plays a major role in further reducing the melting temperature. However, the amount of bismuth which can be added is limited because the bismuth has great destructive effect on fatigue life and plasticity, and the addition of silver can reduce the melting temperature and simultaneously improve the wettability and plasticity of the solder, so that the fatigue life of the solder for welding three-layer welding surfaces is improved (representing reliability aging tests: TC200, DH1000 and the like) by preparing eutectic alloy for Ag, Cu, Sn and Bi according to the solid-liquid phase temperature formed by the balanced preparation of quaternary systems of various element proportions, and the temperature range of the welding melting point of the heterojunction HIT type ultrathin battery piece required by matching is reached.
the following is an analytical comparison by way of examples and comparative examples.
Example 1
Firstly, 1) preparing an added Sn-Ag-Cu Sn-Ag intermediate alloy by adopting a powder metallurgy method: and (3) mixing the tin particles Sn: adding ceramic balls and 1 liter of alcohol into a planetary high-speed ball milling tank according to the weight ratio of 19.5:1.5, sealing, mixing, ball milling for 3 hours, pouring out, filtering, vacuum drying at low temperature, and then performing diffusion sintering at 215 ℃ and isostatic pressing to obtain the required Sn-Ag-Cu Sn-Ag intermediate alloy; secondly, 2) preparing the Sn-Bi-Cu alloy Sn-Bi-Cu lead-free low-temperature basic solder: and (3) mixing tin ingots with the purity of more than 99.95% Sn: adding bismuth Bi into a vacuum melting furnace under the protection of nitrogen according to the mass ratio of 40:39, heating to 280 ℃ to completely melt, adding a hook-type copper plate with the purity of more than 99.95% to heat and burn tin, preserving heat for 60 minutes, removing surface tin slag, taking out a copper strip, cooling to 230 ℃, stirring for 15-30 minutes, and removing the surface tin slag again to obtain a tin-bismuth-copper alloy Sn-Bi-Cu lead-free low-temperature basic solder mixed solution; and then, 3) adding the Sn-Ag-Cu Sn-Ag intermediate alloy prepared in the step 1) into the mixed solution in the step 2) (Sn-Ag intermediate alloy: the addition ratio of Sn-Bi-Cu of the Sn-Bi-Cu alloy is 21: 79), heating to 400 ℃ under the protection of nitrogen, preserving heat and stirring for 30 minutes, removing tin slag on the surface, then cooling to 220 ℃, preserving heat and stirring for 10 minutes, then cooling to 170 ℃, preserving heat and stirring for 10 minutes, and filtering through a honeycomb carbon net into a tin bar grinding tool to finish casting.
The solder prepared in this example was tested for melting point and fabricated into solder ribbons (i.e., photovoltaic solder ribbons for heterojunction HIT ultra-thin cells) and used for solder assembly and reliability testing, with the results shown in fig. 1 below. (this experiment is illustrated but not limited to ottv infrared heat welding heterojunction testing).
Example 2
First, the procedure was the same as in example 1, step 1), except that the tin particles Sn: the silver powder Ag is mixed according to the weight ratio of 32.5:2.5 to obtain Sn-Ag-Cu Sn-Ag intermediate alloy; next, the procedure is the same as in step 2) of example 1, except that the purity of the tin ingot Sn is greater than 99.95%: obtaining a Sn-Bi-Cu alloy Sn-Bi-Cu lead-free low-temperature basic solder mixed solution by bismuth Bi according to the mass ratio of 26: 39; then, the procedure was the same as in example 1, step 3) Sn-Ag intermediate bonding: the Sn-Bi-Cu alloy Sn-Bi-Cu is added in a ratio of 35:65, and is filtered into a tin bar grinding tool through a honeycomb carbon net by the same process to be cast.
The solder prepared in this example was tested for melting point and fabricated into solder ribbons (i.e., photovoltaic solder ribbons for heterojunction HIT ultra-thin cells) and used for solder assembly and reliability testing, with the results shown in fig. 1 below. (this experiment is illustrated but not limited to ottv infrared heat welding heterojunction testing).
Example 3
First, the procedure was the same as in example 1, step 1), and tin particles Sn: the silver powder Ag is prepared into the required Sn-Ag-Cu Sn-Ag intermediate alloy by diffusion sintering at 215 ℃ and isostatic pressing according to the weight ratio of 19.5: 1.5; secondly, the procedure is the same as that of step 2) of example 1, and the tin ingot Sn with the purity of more than 99.95 percent: adding bismuth Bi into a vacuum melting furnace under the protection of nitrogen according to the mass ratio of 42:37, heating to 340 ℃ to completely melt, adding a hook-type copper plate with the purity of more than 99.95% to heat and burn tin, preserving heat for 60 minutes, removing surface tin slag, taking out a copper strip, cooling to 220 ℃, stirring for 15-30 minutes, and removing the surface tin slag again to obtain a tin-bismuth-copper alloy Sn-Bi-Cu lead-free low-temperature basic solder mixed solution; then, the procedure was the same as in example 1, step 3) Sn-Ag intermediate bonding: the tin-bismuth-copper alloy Sn-Bi-Cu is added in a proportion of 21:79, is heated to 460 ℃ under the protection of nitrogen, is kept warm and is stirred for 30 minutes, tin slag on the surface is removed, then is cooled to 220 ℃ and is kept warm and is stirred for 10 minutes, is cooled to 180 ℃ and is kept warm and is stirred for 10 minutes, and then is filtered into a tin bar grinding tool through a honeycomb carbon net to be cast.
The solder prepared in this example was tested for melting point and fabricated into solder ribbons (i.e., photovoltaic solder ribbons for heterojunction HIT ultra-thin cells) and used for solder assembly and reliability testing, with the results shown in fig. 1 below. (this experiment is illustrated but not limited to ottv infrared heat welding heterojunction testing).
Example 4
First, the procedure was the same as in example 1, step 1), except that the tin particles Sn: the silver powder Ag is mixed according to the weight ratio of 26:2 to obtain Sn-Ag-Cu Sn-Ag intermediate alloy; next, the procedure is the same as in step 2) of example 1, except that the purity of the tin ingot Sn is greater than 99.95%: bismuth Bi is mixed according to the mass ratio of 34:38 to obtain a Sn-Bi-Cu lead-free low-temperature basic solder mixed solution; then, the procedure was the same as in example 1, step 3) Sn-Ag intermediate bonding: the Sn-Bi-Cu alloy Sn-Bi-Cu is added in a proportion of 28:72, and is filtered into a tin bar grinding tool through a honeycomb carbon net by the same process to be cast.
the solder prepared in this example was tested for melting point and fabricated into solder ribbons (i.e., photovoltaic solder ribbons for heterojunction HIT ultra-thin cells) and used for solder assembly and reliability testing, with the results shown in fig. 1 below. (this experiment is illustrated but not limited to ottv infrared heat welding heterojunction testing).
Example 5
First, the procedure was the same as in example 3, step 1), except that the tin particles Sn: the silver powder Ag is mixed according to the weight ratio of 32.5:2.5 to obtain Sn-Ag-Cu Sn-Ag intermediate alloy; next, the procedure is the same as example 3, step 2), except that the purity of the tin ingot Sn is greater than 99.95%: bismuth Bi is mixed according to the mass ratio of 27.9:37 to obtain a Sn-Bi-Cu alloy Sn-Bi-Cu lead-free low-temperature basic solder mixed solution; then, the procedure was the same as example 3, step 3) Sn-Ag intermediate bonding: the Sn-Bi-Cu alloy Sn-Bi-Cu is added in a ratio of 35:65, and is filtered into a tin bar grinding tool through a honeycomb carbon net by the same process to be cast.
The solder prepared in this example was tested for melting point and fabricated into solder ribbons (i.e., photovoltaic solder ribbons for heterojunction HIT ultra-thin cells) and used for solder assembly and reliability testing, with the results shown in fig. 1 below. (this experiment is illustrated but not limited to ottv infrared heat welding heterojunction testing).
Example 6
First, the procedure was the same as in example 3, step 1), except that the tin particles Sn: the silver powder Ag is mixed according to the weight ratio of 19.5:1.5 to obtain Sn-Ag-Cu Sn-Ag intermediate alloy; next, the procedure is the same as example 3, step 2), except that the purity of the tin ingot Sn is greater than 99.95%: bismuth Bi is mixed according to the mass ratio of 41.8:37 to obtain a Sn-Bi-Cu alloy Sn-Bi-Cu lead-free low-temperature basic solder mixed solution; then, the procedure was the same as example 3, step 3) Sn-Ag intermediate bonding: the Sn-Bi-Cu alloy Sn-Bi-Cu is added in a ratio of 21:79, and is filtered into a tin bar grinding tool through a honeycomb carbon net by the same process to be cast.
The solder prepared in this example was tested for melting point and fabricated into solder ribbons (i.e., photovoltaic solder ribbons for heterojunction HIT ultra-thin cells) and used for solder assembly and reliability testing, with the results shown in fig. 1 below. (this experiment is illustrated but not limited to ottv infrared heat welding heterojunction testing).
Comparative example 1
Casting tin-lead solder GB/T8012 according to the national standard, taking the normal used tin cloud sold in the market: the designation ZHLSn60PbA (i.e., Sn60Pb40), was also fabricated into photovoltaic solder ribbons and used for solder assembly and reliability testing, the results of which are shown in fig. 1 below. (this experiment is illustrated but not limited to ottv infrared heat welding heterojunction testing).
comparative example 2
Casting tin-lead solder GB/T8012 according to the national standard, taking the normal used tin cloud sold in the market: the same model of ZHLSN62PbAg (i.e., Sn62Pb36Ag2) was also fabricated into photovoltaic solder ribbons and used for solder assembly and reliability testing, the results of which are shown in FIG. 1 below. (this experiment is illustrated but not limited to ottv infrared heat welding heterojunction testing).
Comparative example 3
According to the national standard lead-free solder GB/T20422, the conventional commercially available tin powder is taken as follows: the brand S-Bi58Sn42 (namely Bi58Sn42) is also manufactured into a photovoltaic solder strip and is used for welding components and reliability test, and the test result is shown in the following figure 1. (this experiment is illustrated but not limited to ottv infrared heat welding heterojunction testing).
as shown in fig. 1, fig. 2 and fig. 3, it can be seen from the experimental data in the table above that: the traditional lead-containing solder has good tensile force, high melting point and high welding temperature, and has sheet and linear hidden cracks from EL test, thus causing large power attenuation; the bismuth is added to reduce the welding temperature and improve the wettability of the solder, and the silver is added to improve the fatigue life of the solder, so the invention mechanism of the solder comprises the following starting points: the silver paste property of the battery grid line slurry and the eutectic transformation of the intermediate compound of the photovoltaic copper strip are matched, and the characteristics are as follows: the welding adhesion and the aging reliability of the material completely meet the use requirements of products
the previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (7)
1. the low-temperature solder for the photovoltaic solder strip of the HIT heterojunction is characterized by being prepared from the following raw materials in percentage by mass: 35 to 40 percent of bismuth, 1.5 to 2.5 percent of silver powder, 0.01 to 0.02 percent of copper and the balance of tin.
2. The low temperature solder for photovoltaic solder ribbons of HIT heterojunctions as claimed in claim 1 wherein: the solder is prepared from the following raw materials, by mass, 37-39% of bismuth, 1.5-2.5% of silver powder, 0.01-0.02% of copper and the balance of tin.
3. The low temperature solder for photovoltaic solder ribbons of HIT heterojunctions as claimed in claim 2 wherein: the silver powder is spherical silver powder; the purity of the silver powder is more than 99.90%, and the D50 is 0.8-2.0 μm.
4. The low temperature solder for photovoltaic solder ribbons of HIT heterojunctions as claimed in claim 2 wherein: the purity of the copper is greater than 99.97%.
5. The low temperature solder for photovoltaic solder ribbons of HIT heterojunctions as claimed in claim 2 wherein: the purity of the bismuth is more than 99.95%.
6. The low temperature solder for photovoltaic solder ribbons of HIT heterojunctions as claimed in claim 2 wherein: the tin comprises tin ingots and tin particles; the purity of the tin is greater than 99.95%.
7. A preparation method of a low-temperature solder for a photovoltaic solder strip of an HIT heterojunction is characterized by comprising the following sequential steps:
S1, accurately weighing the tin particles and the silver powder according to the weight ratio of the formula, uniformly mixing the materials in a planetary high-speed stirrer with rotation and revolution functions, uniformly ball-milling, pouring out, suction-filtering, drying in vacuum at low temperature, forming intermediate alloy tin-silver-copper Sn-Ag with required appearance quality by high-temperature diffusion sintering and isostatic pressing, and storing at 10-20 ℃ and 45 +/-5% humidity for later use
S2, adding tin ingots with the purity of more than 99.95 percent and bismuth according to the required alloy proportion into a vacuum melting furnace under the protection of nitrogen, heating to the temperature of 280-plus-340 ℃ for melting, adding a hook-type copper plate with the purity of more than 99.95 percent for hot-melting tin, preserving the heat for 40-60 minutes, removing surface tin slag, taking out a copper strip, cooling to the temperature of 220-plus-230 ℃ for stirring for 15-30 minutes, removing the surface tin slag again to obtain the Sn-Bi-Cu leadless low-temperature basic solder mixed solution
S3: and adding the Sn-Ag-Cu Sn-Ag intermediate alloy prepared in the step S1 into the mixed solution in the step S2 according to the required proportion, heating to 400-plus-460 ℃ under the protection of nitrogen, preserving heat and stirring for 30 minutes, removing surface tin slag, cooling to 220 ℃, preserving heat and stirring for 10 minutes, cooling to 170-180 ℃, preserving heat and stirring for 10 minutes, and filtering into a tin bar grinding tool through a honeycomb carbon net to finish casting.
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