CN118002978A - Method for obtaining high-reliability lead-free tin-bismuth-silver solder through multi-element alloying - Google Patents
Method for obtaining high-reliability lead-free tin-bismuth-silver solder through multi-element alloying Download PDFInfo
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Abstract
A method for preparing high-reliability lead-free tin-bismuth-silver solder by multi-element alloying is to prepare intermediate alloy from refractory elements based on SnBi36Ag0.5 solder, and to add 5 alloy elements In the form of pure metals of the intermediate alloy according to a certain sequence and smelting temperature, wherein the alloy elements are Ce, in, cu, sb and Ni. In mass%, the content of Ce was 0.01%,0.05% and 0.1%, the content of In was 0.1%,0.3% and 0.5%, the content of Cu was 0.2%,0.3% and 0.4%, the content of Sb was 0.3%,0.6% and 1.0%, and the content of Ni was 0.01%,0.02% and 0.03%. The 8-element lead-free tin-bismuth-silver solder prepared by the invention has high alloying degree, uniform and refined solder structure, obviously improved creep resistance and thermal fatigue performance, effectively solves the problem of insufficient reliability of the existing Sn-Bi-Ag solder, and can meet the use scene with strict requirements on reliability in the field of low-temperature welding. Meanwhile, the Ag content is reduced, so that the product cost is controlled, and the popularization and the application of the solder are facilitated.
Description
Technical Field
The invention relates to a method for obtaining high-reliability lead-free tin-bismuth-silver solder by multi-element alloying, belonging to the technical field of electronic welding.
Background
Lead-free solders have become a trend to replace conventional Sn-Pb solders due to the toxicity of lead. Sn-Ag-Cu based solders have been widely used in the electronics industry as the most reliable and mature solders among lead-free solders. However, the melting point of Sn-Ag-Cu-based solders is usually 217 ℃ or higher. With the miniaturization, high integration and portable development of electronic products, many products such as lightning protection equipment, temperature sensitive device equipment, LED lighting equipment, photovoltaic solder strips and the like need to be welded at low temperature. Therefore, lead-free low-temperature welding becomes a new field with market demands. The Sn-Bi solder is used as an important component of low-temperature lead-free solder, has the advantages of low cost, good wettability, high welding spot strength, good thermal fatigue performance and the like, sn can be infinitely dissolved with Bi element within a certain range, no new compound is formed, therefore, the melting point of the solder can be changed by adjusting the Bi content, for example, the melting point of SnBi58 eutectic component is at least 138 ℃, the melting point is increased along with the decrease of the Bi content, the melting range is increased, the welding is not facilitated, and the brittleness of the alloy is improved to a certain extent. The Bi content of the Sn-Bi alloy used in the current market is mostly between 35% and 58%, so that the low-temperature welding requirements of different temperatures can be met. The Sn-In products which are also low-temperature solders are not suitable for large addition due to the high price of In, and new compounds can be formed along with the increase of the content of In, so that uncertainty is brought to the performance of the alloy. The lead-free low temperature solder currently used is mainly Sn-Bi solder. The Sn-Bi solder has the defects that the brittleness and low ductility caused by Bi element make the deformation processing of the Sn-Bi solder difficult, such as popularization of products of Sn-Bi tin wires, BGA balls, soldering lugs and the like. In addition, bi enrichment is easy to form near the Sn-Bi/Cu welding spot IMC layer in long-term service, some Bi-rich phases distributed on the solder matrix intersect with the IMC layer, a Cu6Sn5 layer near one side of the solder in the IMC layer extends upwards along the Bi-rich phases, so that the interface layer is obviously thickened, and the upwards extending part of Cu6Sn5 contains some Bi elements, so that the composition is different from that of the Cu6Sn5 layer below, and the distribution of phases around the Cu6Sn5 is complex: there is a Bi-rich phase, a Sn-rich matrix phase and an underlying Cu6Sn5 layer. When the temperature of the welding point changes, the welding point is easy to generate stress concentration and form cracks at the position due to mutual extrusion of the welding points caused by expansion and contraction, so that the welding point is invalid or is directly peeled off. The addition of Ag can form Ag3Sn compounds to improve the brittleness of the alloy, and the aggregation near IMC suppresses the diffusion of Sn to the Cu substrate side, thereby improving the solder joint reliability. The Sn-Bi alloy with better performance in the market at present comprises SnBi35Ag1 and SnBi57Ag1, and certain Ag element is added on the basis of Sn-Bi. However, the addition of 1% Ag increases the cost and the performance of the alloy is significantly reduced as the Ag content is reduced. In addition, the alloy with 2 components can only improve brittleness and reliability to a certain extent, and can not completely solve the reliability problem caused by the segregation of Bi elements.
Disclosure of Invention
The invention aims to provide a method for obtaining high-reliability lead-free tin-bismuth-silver solder by multi-element alloying, which aims to solve the problem of insufficient reliability of the prior Sn-Bi-Ag solder alloy.
The technical scheme adopted by the invention is as follows:
A method for preparing high-reliability lead-free tin-bismuth-silver solder by multi-element alloying is to prepare intermediate alloy from refractory elements based on SnBi36Ag0.5 solder, and to add 5 alloy elements In the form of pure metals of the intermediate alloy according to a certain sequence and smelting temperature, wherein the alloy elements are Ce, in, cu, sb and Ni. In mass%, the content of Ce was 0.01%,0.05% and 0.1%, the content of In was 0.1%,0.3% and 0.5%, the content of Cu was 0.2%,0.3% and 0.4%, the content of Sb was 0.3%,0.6% and 1.0%, and the content of Ni was 0.01%,0.02% and 0.03%.
The method for obtaining the high-reliability lead-free tin-bismuth-silver solder through multi-element alloying comprises the following steps:
(1) In the solder preparation process, cu, ni and Ce are added in the form of master alloys SnCu10, snNi4 and SnCe1.8 respectively, and the rest elements are added by pure metals. Calculating and weighing the required SnCu10, snNi4, snCe1.8, pure In, pure Sb, pure Bi, pure Ag and pure Sn according to the mass percentage composition of the high-reliability lead-free tin-bismuth-silver solder alloy;
(2) Firstly, putting pure Sn and pure Bi into a batching furnace for smelting, wherein the smelting temperature is set to 300+/-10 ℃;
(3) After the metal materials in the step (2) are melted, pure Ag and pure Sb are put into a smelting furnace, and the smelting temperature is increased to 400+/-10 ℃; continuously stirring the metal materials in the melting process to uniformly mix the materials;
(4) When the metal materials In the step (3) are completely melted, slag is removed, the melting temperature is reduced to 300+/-10 ℃, and then pure In, snNi4, snCe1.8 and SnCu10 alloy are put into a melting furnace, and a layer of anti-oxidation solvent is covered on the surface of the metal solution to prevent oxidation burning loss. Because of more types of the added intermediate alloy, the heat preservation is needed for a long time, and the heat preservation is carried out for at least 60 minutes when each element is uniformly diffused in the solution;
(5) After all metal materials in a smelting furnace are fully and uniformly smelted, slagging off, cooling the metal liquid to 240+/-10 ℃, pouring into a mould, and casting into ingots to obtain the high-reliability lead-free tin-bismuth-silver solder; because the Cu element is contained, the Cu6Sn5 phase can be firstly precipitated In the alloy In the cooling process, and a large amount of additive elements (In, sb, ce and Ni) can be dissolved In the Cu6Sn5 compound In a solid manner, so that the distribution of the elements and the content of the elements In the matrix Sn phase are influenced, the cooling speed is increased by putting a die into circulating cooling water In the ingot casting process, the solid solution amount of the additive elements In the Cu6Sn5 compound is reduced, and the effects of inhibiting segregation and refining grains can be further achieved;
Further, the preparation method of the SnCu10 master alloy in the step (1) comprises the following steps: adding Sn and Cu with the purity of 99.99 percent into a vacuum smelting furnace according to the mass percentage of 90:10, vacuumizing to below 5 multiplied by 10 < -3 > Pa, filling protective gas, heating to 1100 ℃, preserving heat for 30min, fully mixing the melt by using a stirring device in the heat preservation process, and finally carrying out vacuum casting to obtain the SnCu10 intermediate alloy.
The preparation method of the SnNi4 intermediate alloy comprises the following steps: adding Sn and Ni with the purity of 99.99 percent into a vacuum melting furnace according to the mass percentage of 96:4, vacuumizing to below 5 multiplied by 10 < -3 > Pa, charging protective gas, heating to 1450 ℃ and preserving heat for 30min, fully mixing the melt by using a stirring device in the heat preservation process, and finally performing vacuum casting to obtain the SnNi4 intermediate alloy.
The preparation method of the SnCe1.8 intermediate alloy comprises the following steps: adding Sn and Ce with the purity of 99.99 percent into a vacuum smelting furnace according to the mass percentage of 98.2:1.8, vacuumizing to below 5 multiplied by 10 < -3 > Pa, charging protective gas, heating to 900 ℃, preserving heat for 30min, fully mixing the melt by using a stirring device in the heat preservation process, and finally carrying out vacuum casting to obtain the SnCe1.8 intermediate alloy.
And (3) the antioxidant solvent in the step (4) is rosin or KCL-LiCl molten salt.
The invention has the following advantages;
(1) The high-reliability lead-free tin-bismuth-silver solder alloy of the invention is subjected to component adjustment and supplement perfection on the basis of the Sn-Bi-Ag solder widely applied at present, trace elements Cu, sb, ni, ce, in are added for compounding, the addition amount of Ag is reduced, and space is provided for the addition of other elements. The micro Ni is added into the solder to refine grains, so as to play a role in inhibiting the growth of the grains. Refinement of the Bi-rich phase can suppress thickening of the interface layer caused by the Bi-rich phase to some extent. In addition, the Ni element can also inhibit the growth of a Cu3Sn layer on the side close to the Cu substrate in the IMC layer, but the addition of excessive Ni element can cause the Cu6Sn5 layer to be obviously thickened, so that the Ni content needs to be controlled within 0.03 percent. Ce is a surface active element that is easily aggregated at grain boundaries, producing pinning effects, preventing grain growth. On the one hand, by refining the Bi-rich phase, the thickening of the interface layer caused by the Bi-rich phase is suppressed. On the other hand, since grain boundaries play a role of a fast channel for diffusion, the aggregation of Ce at the grain boundaries can close the fast channel, and prevent Sn from diffusing to one side of the Cu substrate. However, excessive addition of Ce element generates CeSn compound and affects distribution, so that the addition amount of Ce needs to be controlled and is generally not more than 0.1%. The addition of Sb can replace Sn in Cu6Sn5 to form Cu6 (Sn, sb) 5 compounds, thereby playing a role similar to solid solution strengthening and improving the strength of Cu6Sn 5. The addition of the Sb element can suppress the occurrence of cracks in the interface layer to some extent. However, since excessive Sb causes thickening of the interface layer, the addition amount of Sb element is not excessive, and the addition amount of Sb element in the present invention is controlled to be within 1%. The addition of Cu element forms a small amount of solid solution in the matrix Sn-rich phase in addition to Cu6Sn5, and reduces the Cu concentration gradient at the interface between the solder and the Cu substrate, thereby reducing the diffusion flux and suppressing thickening of the interface layer. The In element tends to aggregate at the grain boundary, so that the growth of crystal grains is suppressed, similar to the addition effect of Ce. Besides this effect, it also has the effect of softening the solder matrix and improving brittleness. In conclusion, the comprehensive performance, particularly the reliability, of the alloy is obviously improved through the addition of various elements.
(2) The high-reliability lead-free tin-bismuth-silver solder alloy has high alloying degree, uniform and refined solder structure, obviously improved creep resistance and thermal fatigue performance, effectively solves the problem of insufficient reliability of the conventional Sn-Bi-Ag solder, and can meet the use scene with strict requirements on reliability in the field of low-temperature welding.
(3) Compared with SnBi35Ag1 with better performance In the market, the high-reliability lead-free tin-bismuth-silver solder alloy has the advantages that the Ag content is reduced by 0.5%, the Bi content is improved by 1%, the added Ce content is 0.1% at most, the In content is 0.5% at most, the Cu content is 0.4% at most, the Sb content is 1.0% at most and the Ni content is 0.03% at most. The cost is lower after comprehensive calculation, and the popularization and the application of the solder are more facilitated.
(4) The preparation method disclosed by the invention is simple in process and high in feasibility. The obtained 8-element high-reliability lead-free tin-bismuth-silver solder has uniform components and no segregation.
Drawings
FIG. 1 is a DSC graph of the alloy of example 1;
FIG. 2 is a DSC graph of the alloy of example 2;
FIG. 3 is a DSC graph of the alloy of example 3;
FIG. 4 is a DSC graph of the alloy of example 4;
FIG. 5 is a DSC graph of the alloy of example 5;
FIG. 6 is a metallographic structure diagram of the solder alloy of example 1;
FIG. 7 is a metallographic structure diagram of the solder alloy of example 2;
FIG. 8 is a metallographic structure diagram of the solder alloy of example 3;
FIG. 9 is a metallographic structure diagram of the solder alloy of example 4;
FIG. 10 is a metallographic structure diagram of the solder alloy of example 5;
FIG. 11 is a metallographic structure diagram of the solder alloy of comparative example 1;
FIG. 12 is a metallographic structure diagram of the solder alloy of comparative example 2;
FIG. 13 is a microstructure view of a solder joint of example 1 isothermally aged at 120℃for 2000 hours;
FIG. 14 is a microstructure view of a solder joint of example 2 isothermally aged at 120℃for 2000 hours;
FIG. 15 is a microstructure view of a solder joint of example 3 with isothermal aging at 120℃for 2000 hours;
FIG. 16 is a microstructure view of a solder joint of example 4 isothermally aged at 120℃for 2000 hours;
FIG. 17 is a microstructure view of a solder joint of example 5 isothermally aged at 120℃for 2000 hours;
FIG. 18 is a microstructure view of a solder joint of comparative example 1 after isothermal aging at 120℃for 2000 hours;
FIG. 19 is a microstructure graph of a solder joint of comparative example 2 isothermally aged at 120℃for 2000 hours.
Detailed Description
The technology of the present invention is further illustrated by the following examples.
Example 1
A highly reliable Pb-free Sn-Bi-Ag solder alloy is prepared, wherein the Pb-free solder comprises, by mass, 36.0% of Bi, 0.5% of Ag, 0.01% of Ce, 0.1% of In, 0.2% of Cu, 0.3% of Sb, 0.01% of Ni, and the balance of Sn and unavoidable impurities. The melting point of the lead-free solder is 141.1-177.9 ℃, the tensile strength is 98.5Mpa, the elongation is 30.8%, the wetting time is 0.647s, the maximum wetting force is 5.288mN, and the solder joint spreading rate is 79.1%.
Example 2
A highly reliable Pb-free Sn-Bi-Ag solder alloy is prepared, wherein the Pb-free solder comprises, by mass, 36.0% of Bi, 0.5% of Ag, 0.1% of Ce, 0.5% of In, 0.4% of Cu, 1.0% of Sb, 0.03% of Ni, and the balance of Sn and unavoidable impurities. The melting point of the lead-free solder is 140.6-176.0 ℃, the tensile strength is 100.5Mpa, the elongation is 29.8%, the wetting time is 0.635s, the maximum wetting force is 4.775mN, and the solder joint spreading rate is 79.4%.
Example 3
A highly reliable Pb-free Sn-Bi-Ag solder alloy is prepared, wherein the Pb-free solder comprises, by mass, 36.0% of Bi, 0.5% of Ag, 0.05% of Ce, 0.3% of In, 0.3% of Cu, 0.6% of Sb, 0.02% of Ni, and the balance of Sn and unavoidable impurities. The melting point of the lead-free solder is 140.6-175.9 ℃, the tensile strength is 99.4Mpa, the elongation is 31.9%, the wetting time is 0.637s, the maximum wetting force is 4.873mN, and the solder joint spreading rate is 78.3%.
Example 4
A highly reliable Pb-free Sn-Bi-Ag solder alloy is prepared, wherein the Pb-free solder comprises, by mass, 36.0% of Bi, 0.5% of Ag, 0.01% of Ce, 0.1% of In, 0.4% of Cu, 1.0% of Sb, 0.01% of Ni, and the balance of Sn and unavoidable impurities. The melting point of the lead-free solder is 141.4-178.3 ℃, the tensile strength is 99.1Mpa, the elongation is 24.4%, the wetting time is 0.604s, the maximum wetting force is 4.823mN, and the solder joint spreading rate is 77.6%.
Example 5
A highly reliable Pb-free Sn-Bi-Ag solder alloy is prepared, wherein the Pb-free solder comprises, by mass, 36.0% of Bi, 0.5% of Ag, 0.1% of Ce, 0.5% of In, 0.2% of Cu, 0.3% of Sb, 0.03% of Ni, and the balance of Sn and unavoidable impurities. The melting point of the lead-free solder is 140.0-175.1 ℃, the tensile strength is 96.9Mpa, the elongation is 32.3%, the wetting time is 0.677s, the maximum wetting force is 4.940mN, and the solder joint spreading rate is 77.9%.
In the preparation process of the high-reliability lead-free tin-bismuth-silver solder alloys of the above examples 1 to 5, cu, ni and Ce are respectively added in the form of intermediate alloys SnCu10, snNi4 and SnCe1.8, and the rest elements are added by pure metals. The preparation method comprises the following steps:
(1) Calculating and weighing SnCu10, snNi4, snCe1.8, pure In, pure Sb, pure Bi, pure Ag and pure Sn which are required according to the mass percentage composition of the embodiment;
(2) Firstly, putting pure Sn and pure Bi into a batching furnace for smelting, wherein the smelting temperature is set to 300+/-10 ℃;
(3) After the metal materials in the step (2) are melted, pure Ag and pure Sb are put into a smelting furnace, and the smelting temperature is increased to 400+/-10 ℃; continuously stirring the metal materials in the melting process to uniformly mix the materials;
(4) When the metal materials In the step (3) are completely melted, slag skimming is carried out, the melting temperature is reduced to 300+/-10 ℃, then pure In, snNi4, snCe1.8 and SnCu10 alloy are put into a melting furnace, and then a layer of anti-oxidation solvent is covered on the surface of the metal solution, and the temperature is kept for at least 60 minutes;
(5) After all metal materials in a smelting furnace are fully and uniformly smelted, slagging off, cooling the metal liquid to 240+/-10 ℃, pouring into a mould, and casting into ingots to obtain the high-reliability lead-free tin-bismuth-silver solder; in the ingot casting process, the mould is put into circulating cooling water to increase the cooling speed.
The equipment used in the method, such as a smelting furnace, a stirring device, a casting mould of an ingot casting and the like, are all prior art equipment.
Comparative example 1
A low-temperature lead-free solder alloy comprises, by mass, 36.0% of Bi, 0.5% of Ag, and the balance of Sn and unavoidable impurities. The melting point of the lead-free solder is 141.1-175.5 ℃, the tensile strength is 82.1Mpa, the elongation is 32.4%, the wetting time is 0.627s, the maximum wetting force is 5.278mN, and the solder joint spreading rate is 77.2%.
Comparative example 2
A low-temperature lead-free solder alloy comprises, by mass, 35.0% of Bi, 1.0% of Ag, and the balance of Sn and unavoidable impurities. The melting point of the lead-free solder is 141.2-176.6 ℃, the tensile strength is 90.0Mpa, the elongation is 36.8%, the wetting time is 0.635s, the maximum wetting force is 5.345mN, and the solder joint spreading rate is 78.4%.
The melting point of the solder is measured by a DSC131evo type differential scanning calorimeter, the protective atmosphere is nitrogen, the alloy mass is 20mg, and the heating rate is 5K/min. As shown in fig. 1-5, the addition of 5 elements for multiple alloying did not significantly increase the melting point and melting range of the solder. The liquidus temperatures of the 5 examples were all less than 180 ℃.
The mechanical properties of the solder are measured by adopting think carefully longitudinal and transverse UTM4104X type electronic universal material testing machine, the solder is cast into a standard stretching test bar at 320 ℃ for stretching experiments, the stretching speed is 7.2mm/min, and the gauge length is 50mm. The results obtained are shown in Table 1, and the tensile strength of the solder after multi-element alloying is significantly increased.
The solderability of the solder was measured by using Must SYSTEM III type solderability tester, the base material was a 30X 10X 0.3mm phosphor-deoxidized copper sheet, and the test standard was JIS Z3198-4:2003 (wetting balance method A). The results obtained are shown in Table 1, with a slight drop in the maximum wetting force of the solder after multi-alloying, but still far above the customer's use standard, which is negligible.
Cutting the solder alloy into 0.3g of pellets, preparing a copper sheet with the specification of 30 multiplied by 0.3mm (the copper sheet is soaked in 5% dilute hydrochloric acid and then is cleaned by absolute ethyl alcohol), coating 0.06g of Sn-Bi series soldering paste on the copper sheet, placing the cut solder pellets on the soldering paste, placing the copper sheet loaded with the soldering paste and the solder pellets on a heating plate, and melting to prepare a welding spot sample, wherein the melting temperature is 250 ℃ and the melting time is 30s. The solder joint height was measured with a micrometer to calculate the spreading rate of the solder. The results obtained are shown in Table 1, and the spreading rate of the solder after the multi-alloying is higher than that of comparative example 1.
In conclusion, the basic performance of the solder after the multi-element alloying is not obviously fluctuated or reduced, and the solder still has the advantages of low melting point, good wettability and high tensile strength of the Sn-Bi-Ag solder.
FIGS. 6 to 10 are diagrams showing metallographic structures of the solder alloys of examples 1 to 5, and FIGS. 11 to 12 are diagrams showing metallographic structures of the solder alloys of comparative examples 1 to 2. The metallographic structure diagram is obtained by casting a solder alloy into small round blocks, embedding the central part of the round blocks with AB glue, grinding and polishing after the glue is solidified, corroding a sample by using 93% methanol+5% nitric acid+2% hydrochloric acid corrosive liquid, and observing under a Zeiss Scope A1 optical microscope. As can be seen from comparison, the Bi-rich phase of the examples is significantly finer, distributed more uniformly and dispersed than that of the comparative examples. The Bi-rich phases of comparative examples 1-2 exhibited a remarkable coarsening phenomenon.
FIGS. 13-19 are isothermal aging diagrams of welds. The isothermal aging chart is that the prepared welding spot sample is placed in a high-low temperature test box (model EG-02 KA) of Guangzhou five environmental instruments Co., ltd for isothermal aging test at 120 ℃. And taking out the sample after 2000 hours, embedding the sample with AB glue, grinding and polishing the sample after the glue is solidified, corroding the sample by using 93% methanol, 5% nitric acid and 2% hydrochloric acid corrosive liquid, and observing the sample under a Zeiss Scope A1 optical microscope. The isothermal aging map interface contains 3 phases, from top to bottom, bi-rich phases, cu6Sn5 and Cu3Sn, respectively, intersecting the IMC layer. The IMC thickness was measured only in the regions not intersecting the Bi-rich phase, regardless of the thickening caused by the Cu6Sn5 layer extending upward along the Bi-rich phase. The Cu3Sn layer of examples 1-5 was less than 1 μm at its thickest and the overall IMC layer thickness was in the range of 3.1-7.7 μm. From fig. 18, it is understood that the IMC layer of comparative example 1 has developed a remarkable cracking phenomenon after isothermal aging for 2000 hours. As is clear from FIG. 19, the IMC layer thickness of comparative example 2 is in the range of 4.2-9.2. Mu.m, and the Cu3Sn layer is at a maximum thickness of about 2. Mu.m, which is significantly higher than that of examples 1-5.Cu3Sn is more brittle and harder than Cu6Sn5, and cracks are more likely to occur near the Cu3Sn layer, so the thinner the Cu3Sn layer, the better the solder joint reliability. The weld interface IMC layers of comparative examples 1-5 were thinner after prolonged isothermal aging, particularly the Cu3Sn layer was significantly thinner, and no cracking occurred, thus the reliability was higher than that of comparative examples 1 and 2.
Table 1 experimental data for all examples and comparative examples
The high-reliability lead-free tin-bismuth-silver solder alloy prepared by the invention greatly improves the reliability on the premise of ensuring the excellent characteristics of Sn-Bi-Ag solder alloy by the composite addition of a plurality of elements. The Ag content is reduced, and the cost is controlled. The melting point of the solder is 140-179 ℃, the tensile strength is above 90Mpa, the elongation is within 24-33%, the wetting time is 0.6-0.7s, the maximum wetting force is 4.7-5.3mN, the spreading rate is above 77%, and various performance indexes show that the high-reliability Sn-Bi-Ag series low-temperature lead-free solder alloy can be widely applied to the field of electronic welding.
The above embodiments are only some, but not all, embodiments of the present invention. On the basis of SnBi36Ag0.5 solder, refractory elements are prepared into intermediate alloy, 5 alloy elements are added In the form of adding pure metal into the intermediate alloy according to a certain sequence and smelting temperature, and the alloy elements are Ce, in, cu, sb and Ni. In mass%, the content of Ce was 0.01%,0.05% and 0.1%, the content of In was 0.1%,0.3% and 0.5%, the content of Cu was 0.2%,0.3% and 0.4%, the content of Sb was 0.3%,0.6% and 1.0%, and the content of Ni was 0.01%,0.02% and 0.03%. These are all within the scope of the present invention.
Claims (3)
1. A method for obtaining high-reliability lead-free tin-bismuth-silver solder by multi-element alloying is characterized In that on the basis of SnBi36Ag0.5 solder, refractory elements are prepared into intermediate alloy, 5 alloy elements are added In the form of adding pure metals into the intermediate alloy according to a certain sequence and smelting temperature, and the alloy elements are Ce, in, cu, sb and Ni. In mass%, the content of Ce was 0.01%,0.05% and 0.1%, the content of In was 0.1%,0.3% and 0.5%, the content of Cu was 0.2%,0.3% and 0.4%, the content of Sb was 0.3%,0.6% and 1.0%, and the content of Ni was 0.01%,0.02% and 0.03%.
2. A method of obtaining a highly reliable lead-free tin bismuth silver solder by multiple alloying according to claim 1, comprising the steps of:
(1) Calculating and weighing the required SnCu10, snNi4, snCe1.8, pure In, pure Sb, pure Bi, pure Ag and pure Sn according to the mass percentage composition of the high-reliability lead-free tin-bismuth-silver solder alloy;
(2) Firstly, putting pure Sn and pure Bi into a batching furnace for smelting, wherein the smelting temperature is set to 300+/-10 ℃;
(3) After the metal materials in the step (2) are melted, pure Ag and pure Sb are put into a smelting furnace, and the smelting temperature is increased to 400+/-10 ℃; continuously stirring the metal materials in the melting process to uniformly mix the materials;
(4) When the metal materials In the step (3) are completely melted, slag skimming is carried out, the melting temperature is reduced to 300+/-10 ℃, then pure In, snNi4, snCe1.8 and SnCu10 alloy are put into a melting furnace, and then a layer of anti-oxidation solvent is covered on the surface of the metal solution, and the temperature is kept for at least 60 minutes;
(5) After all metal materials in a smelting furnace are fully and uniformly smelted, slagging off, cooling the metal liquid to 240+/-10 ℃, pouring into a mould, and casting into ingots to obtain the high-reliability lead-free tin-bismuth-silver solder; in the ingot casting process, the mould is put into circulating cooling water to increase the cooling speed.
3. The method for obtaining the high-reliability lead-free tin-bismuth-silver solder by multi-element alloying according to claim 2, wherein the preparation method of the SnCu10 master alloy in the step (1) is as follows: adding Sn and Cu with the purity of 99.99 percent into a vacuum smelting furnace according to the mass percentage of 90:10, vacuumizing to below 5 multiplied by 10 -3 Pa, filling protective gas, heating to 1100 ℃, preserving heat for 30min, fully mixing the melt by using a stirring device in the heat preservation process, and finally performing vacuum casting to obtain the SnCu10 intermediate alloy;
The preparation method of the SnNi4 intermediate alloy comprises the following steps: adding Sn and Ni with the purity of 99.99 percent into a vacuum smelting furnace according to the mass percentage of 96:4, vacuumizing to below 5 multiplied by 10 -3 Pa, charging protective gas, heating to 1450 ℃, preserving heat for 30min, fully mixing the melt by using a stirring device in the heat preservation process, and finally performing vacuum casting to obtain SnNi4 intermediate alloy;
The preparation method of the SnCe1.8 intermediate alloy comprises the following steps: adding Sn and Ce with the purity of 99.99 percent into a vacuum smelting furnace according to the mass percentage of 98.2:1.8, vacuumizing to below 5 multiplied by 10 -3 Pa, charging protective gas, heating to 900 ℃, preserving heat for 30min, fully mixing the melt by using a stirring device in the heat preservation process, and finally performing vacuum casting to obtain SnCe1.8 intermediate alloy;
The method for obtaining a high-reliability lead-free tin-bismuth-silver solder by multi-element alloying according to claim 2, wherein the antioxidation solvent in the step (4) is rosin or KCL-LiCl molten salt.
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