High-strength high-elongation SnPbSbInAu alloy solder and preparation method thereof

Abstract

The invention discloses a high-strength and high-elongation SnPbSbInAu alloy solder and a preparation method thereof. The alloy solder comprises the following components in percentage by weight: 33.0 to 36.5 percent of Pb, 2.0 to 4.0 percent of Sb, 1.5 to 3.5 percent of In, 2.0 to 3.5 percent of Au, 0.005 to 0.012 percent of P and the balance of Sn. The preparation method of the foil strip comprises the steps of vacuum pressure casting, strip cold extrusion and cold roller rolling, the wire preparation method comprises the steps of one-time extrusion forming and close-packed rewinding, and the powder paste preparation method comprises the steps of vacuum gas atomization powder preparation, airflow screening and planetary centrifugal degassing paste preparation. The solid-liquid phase temperature of the solder ranges from 180 DEG C to 185 DEG C, the solder has the advantages of being high in ductility, strength and creep resistance, excellent in low-temperature service performance and the like, and the tensile strength of a brazed joint of the solder is two times higher than that of a Sn-37Pb eutectic solder under the same welding process; and the gold etching risk is low, and a gold-plated piece can be directly welded (without tinning treatment).

Description

Technical Field

[0001] The invention relates to a high-strength and high-elongation SnPbSbInAu alloy solder and a preparation method thereof, and belongs to the field of advanced electronic packaging. Background Art

[0002] With the rapid development of the semiconductor and electronics industries, the performance competition of products such as photoelectric conversion modules, automotive radars for intelligent assisted driving, 5G communication equipment, medical devices, navigation satellites and terminals, and military microwave modules has become increasingly fierce. According to statistics, more than 70% of the failures of related electronic equipment are caused by the failure of packaging solder joints. Therefore, many of the above products have also put forward higher reliability requirements for the basic common microelectronic packaging technology. It is urgent to develop new high-strength solder alloys for microelectronic packaging.

[0003] At present, lead-free solder alloys still have a certain gap with Sn-Pb solder alloys in terms of comprehensive performance such as packaging strength, wettability, oxidation resistance, and tin whisker inhibition. Therefore, in electronic products under the above-mentioned high-reliability application scenarios, Sn-Pb solder alloys are still the main application. At the same time, in order to improve reliability and product life, gold plating is also mostly used for packaging interfaces. However, on the one hand, in order to avoid the "gold brittleness" phenomenon, electronic products with gold-plated surfaces must first be tin-plated to remove the gold. On the other hand, with the improvement of electronic product performance and the influence of harsh service environment conditions and other factors, the use of tin-lead eutectic solder often causes cracking of the metallurgical bonding layer at the packaging interface. The reasons for this are analyzed to be the cracking of solder joints caused by the poor strength and stress resistance of the tin-lead eutectic solder, and the cracking caused by the diffusion and migration of gold elements to the welding interface during the brazing process. Summary of the invention

[0004] In view of the problems of the prior art, the present invention provides a high-strength and high-elongation SnPbSbInAu alloy solder. The solder alloy is a multi-electrochemical near-eutectic melting point, the alloy melting temperature is 180°C to 185°C, and the recommended brazing temperature is 200°C to 210°C. It can replace Sn-37Pb eutectic solder, and has the advantages of high elongation, low temperature resistance, high creep resistance, and long service life in harsh and complex environments. It can directly weld gold-plated parts with a low risk of "gold corrosion" and no tinning treatment is required, thus meeting the needs of microelectronic packaging of electronic products in high-reliability application scenarios and high-strength and low-temperature brazing of lightweight alloys.

[0005] Another object of the present invention is to provide a method for preparing a SnPbSbInAu alloy solder with high elongation. The preparation method is used to obtain alloy foil strips, wires, and powder pastes to meet the requirements of microelectronic packaging of electronic products in high-reliability application scenarios and high-strength and low-temperature brazing of lightweight alloys.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A high-strength and high-elongation SnPbSbInAu alloy solder consists of the following components by weight percentage: Pb 33.0-36.5wt%, Sb 2.0-4.0wt%, In 1.5-3.5wt%, Au 2.0-3.5wt%, P 0.005-0.012wt%, and the balance is Sn, and the total amount of the above components is 100%.

[0008] Among them, the optimized weight percentage composition of each element is:

[0009] The added mass percentage of the Pb element is preferably 34.0 to 35.0 wt %;

[0010] The added mass percentage of the Sb element is preferably 2.8 to 3.5 wt %;

[0011] The added mass percentage of the In element is preferably 2.2 to 2.8 wt %;

[0012] The added mass percentage of the Au element is preferably 2.5 to 3.2 wt%;

[0013] The added mass percentage of the P element is preferably 0.008-0.01 wt %.

[0014] The present invention designs a eutectic solder to replace Sn-37Pb, which meets the microelectronic packaging of electronic products in high-reliability application scenarios, and has a melting point of about 180-185°C. The main design idea is to first select the alloy component as the Sn-Pb system, obtain the Sn-38.1Pb binary eutectic composition through design, and optimize it on this basis:

[0015] ① Adding a small amount of Sb element can inhibit the diffusion of Sn element, solve the corrosion of gold plating of gold-plated devices by solder, and adjust the melting point of alloy to improve the tensile strength of solder. The test found that when the Sb element content is less than 2.0wt%, it has little effect on the melting point and strength of solder. When the Sb element content is higher than 4wt%, it forms more Sn2Sb3 intermetallic compounds with Sn element, which affects the processing plasticity of solder.

[0016] ② Adding a small amount of In element can optimize the melting point of the alloy and can preferentially generate AuIn compound with the plating layer. Compared with AuSn compound, it has better toughness, improves the elongation performance of the solder, improves the wetting power of the solder in vacuum low-temperature brazing, and can further improve the mechanical properties of the solder under low-temperature environment. It can effectively inhibit the low-temperature phase change of tin-lead alloy, so that the solder still maintains excellent mechanical properties at extremely low temperatures. When the In element exceeds 3.5wt%, a lower melting point phase will precipitate.

[0017] ③ Adding a small amount of Au element can improve the strength of solder, optimize the melting point of alloy, avoid the phenomenon of "gold corrosion" of solder on gold-plated devices, and improve the strength of solder joints after welding. The experiment found that the Au element is controlled at 2.0-3.5wt%, which can optimize the performance and obtain a reasonable melting temperature without deteriorating the alloy processing performance.

[0018] ④ Adding trace amounts of P elements as antioxidant modifying elements can purify the melt. When the alloy is molten, the P element contacts the air to form a phosphorus oxide film, which covers the surface of the melt, hinders air from contacting the alloy melt, and avoids the melt from inhaling and oxidizing. If the P element content is lower than 0.008wt%, the effect is not obvious. If the P element content is higher than 0.01wt%, the plasticity of the alloy decreases and harmful impurities are generated, which in turn affects the solder forming and reduces the performance of the solder joint.

[0019] On the other hand, the present invention provides a method for preparing the above-mentioned high-strength and high-elongation SnPbSbInAu alloy solder, the method comprising the following steps:

[0020] (1) Raw material selection and master alloy preparation

[0021] According to the composition of the above-mentioned high-strength and high-elongation SnPbSbInAu alloy solder, high-purity Sn, Pb, Sb, In, Au and P are used as raw materials;

[0022] The Sn-Pb master alloy, Sn-Sb master alloy, Sn-In master alloy and Sn-Au master alloy were prepared by vacuum medium frequency induction melting method; the Sn-P master alloy was prepared by non-vacuum induction melting method;

[0023] (2) Non-vacuum resistance melting

[0024] The master alloy prepared in step (1) is subjected to the weight percentage of each element in the eutectic medium-temperature solder to calculate the weight of each element and the weight of the master alloy; a resistance melting furnace is used to place the Sn ingot into an alumina crucible of the resistance melting furnace, and the temperature is raised. After the Sn ingot is completely melted, SnP, SnPb, SnSb, SnAu, and SnIn master alloys are added in sequence. After the master alloy is completely melted, the temperature is lowered to the refining temperature, and after the temperature is kept, water-white hydrogenated rosin is added, the alloy melt is fully stirred, degassing is completed, and surface scum is removed, and the temperature is raised to the die-casting temperature and kept warm;

[0025] (3) Rapid cooling pressure casting

[0026] The molten alloy melt obtained in step (2) is subjected to vertical die casting. A high-purity inert gas is filled into the crucible. The melt flows into and fills the graphite casting mold under the gas pressure to quickly complete the alloy ingot molding, and an alloy ingot with uniform composition and fine IMC is obtained, with a diameter of 30 to 150 mm and a height of 100 to 500 mm.

[0027] (4) Solder forming

[0028] A. Foil Strip Preparation

[0029] The alloy ingot obtained in step (3) is subjected to a horizontal extruder to produce a defect-free slab with a thickness of 1 to 6 mm and a width of 10 to 120 mm. The slab is cold-rolled to produce a foil strip with a thickness of 0.03 to 0.1 mm and a width of 10 to 120 mm, which is then rolled into a coil.

[0030] B. Wire Preparation

[0031] The alloy ingot obtained in step (3) is used to prepare wires with a diameter of 0.3 to 2.0 mm using a horizontal extruder, and the wires are densely wound on a plastic I-shaped shaft.

[0032] C. Preparation of powder paste

[0033] The alloy ingot obtained in step (3) is subjected to vacuum gas atomization to prepare spherical powder with a particle size of 10 to 15 μm (D50), and a low-temperature soldering flux is added to prepare solder paste by planetary centrifugal degassing;

[0034] According to the preparation method described above, preferably, in terms of mass percentage, the purity of Sn is 99.999%, the purity of Pb is 99.999%, the purity of Sb is 99.999%, the purity of Au is 99.999%, the purity of In is 99.999%, and the purity of P is 99.99%.

[0035] According to the preparation method as described above, preferably, the Pb content in the Sn-Pb master alloy is 50wt%, and the balance is Sn; the Sb content in the Sn-Sb master alloy is 50wt%, and the balance is Sn; the In content in the Sn-In master alloy is 50wt%, and the balance is Sn; the Au content in the Sn-Au master alloy is 80wt%, and the balance is Sn; the P content in the Sn-P master alloy is 5wt%, and the balance is Sn.

[0036] In the preparation method as described above, preferably, the refining temperature in step (2) is 280-300° C., the holding time is 2-5 min, and the amount of hydrogenated rosin added is 0.05 wt % of the total amount of alloy feed.

[0037] In the preparation method as described above, preferably, the pressure casting temperature of step (3) is 220-250°C, the inert gas pressure is 5-8 MPa, the filling speed is 50-80 m / s, the solidification time is less than 1 s, the outside of the graphite mold is connected to a cooling pipe, and the cooling medium is ultrapure water.

[0038] In the preparation method as described above, preferably, the foil strip preparation process in step A adopts a horizontal extruder with an extrusion pressure of 0.5-5MPa, an extrusion speed of 200-600mm / min, an extrusion ratio of 30-100, and an extrusion temperature of 5-25°C; the cold rolling process uses a two-roll reversible cold rolling mill and a four-roll reversible cold rolling mill, the cold rolling temperature is 5°C-25°C, the cold rolling pass processing rate is 15%-20%, and the tension is 0-5kN.

[0039] In the preparation method as described above, preferably, the wire preparation process in step B adopts a horizontal extruder with an extrusion pressure of 4-10 MPa, an extrusion speed of 80-200 mm / min, an extrusion ratio of 45-2000, an extrusion temperature of 5-25°C, and 3-5 holes in the extrusion die.

[0040] According to the preparation method described above, preferably, in the step C of preparing the powder paste, the atomizer is an annular hole mode, the high-pressure gas is high-purity argon gas, the atomizing gas pressure is 8-9 MPa, the injection angle is 60°, the distance from the melt outlet to the atomization point is 2 mm, the flux is a rosin-based resin medium-activity flux, the alloy powder and the flux are in a ratio of (85-90): (10-15), and the solder paste is prepared by planetary centrifugal degassing, the centrifugal speed is 500-1500 rpm, and the vacuum in the tank is less than 10 - 1 Pa.

[0041] The beneficial effects of the present invention are as follows:

[0042] 1. The high-elongation SnPbSbInAu alloy solder manufactured by the method of the present invention is suitable for microelectronic packaging of electronic products in high-reliability application scenarios, and is used for brazing gold-plated devices, as an alternative to Sn-37Pb eutectic solder, to achieve low-temperature brazing packaging. It further improves the reliability of microelectronic packaging of photovoltaic, automotive electronics, medical equipment, aerospace, military electronics and other products.

[0043] 2. The high elongation SnPbSbInAu alloy solder manufactured by the method of the present invention has a moderate melting point of 180°C to 185°C. After further optimization of the components, a eutectic solder with a melting temperature of 182°C to 185°C can be obtained, which is equivalent to the Sn-37Pb eutectic solder (eutectic melting point 183°C).

[0044] 3. The SnPbSbInAu alloy solder manufactured by the method of the present invention has excellent brazing processability, high elongation, high strength, low temperature resistance, and high creep resistance. The tested elongation at room temperature exceeds 110%. It can adapt to the difference in linear expansion coefficient caused by different material properties of the packaging interface, and effectively solve the problem of cracking and peeling of the coating due to stress concentration, thereby ensuring the service reliability of electronic products in harsh environments. The brazed Au-plated devices can obtain continuous and dense welds, less IMC, and high reliability.

[0045] 4. The SnPbSbInAu alloy solder manufactured by the method of the present invention has excellent wettability to Au plating. No prior tinning treatment is required for brazing gold-plated devices. It can be used to directly weld gold-plated parts with basically no risk of "gold corrosion".

[0046] 5. The SnPbSbInAu alloy solder manufactured by the method of the present invention has a strong ability to resist extreme low temperature phase change, and its tensile shear strength increases with decreasing temperature. Its mechanical properties are even better in low temperature environments, and it can effectively meet the use requirements in harsh environments, thus ensuring the service life of electronic devices in extreme low temperature environments.

[0047] 6. The SnPbSbInAu alloy solder of the present invention is used to braze light alloys without the need for post-braze treatment. The strength after welding can reach 80 MPa, which is much higher than that of traditional tin-lead solders. The comprehensive use cost is close to that of traditional Al-based and Zn-based solders.

[0048] 7. The preparation method disclosed in the present invention covers the product specifications of SnPbSbInAu alloy solder, and has a short process, high efficiency, and is suitable for stable batch production. The finished product has very few internal pores, few defects, fine IMC, no cracks on the edges, high yield rate, high surface cleanliness, no oil, high flatness consistency, can process any preformed products, and is also suitable for stable batch production of soft solder.

[0049] 8. In addition to being used in high-performance and high-reliability electronic products, the SnPbSbInAu alloy solder of the present invention can also meet the high-strength and low-temperature brazing of light alloys (such as aluminum alloys, magnesium alloys, etc.). Traditional light alloy brazing generally uses A1-based and Zn-based solders to complete the package connection, but this type of package has a high temperature, requires a heat treatment, and the light alloy body is easily deformed. The SnPbSbInAu alloy solder of the present invention can reach a strength of 80MPa after one welding of the above-mentioned light alloys, which is much higher than traditional tin-lead and other solders; at the same time, the base material does not need to be heat treated after brazing, and the comprehensive use cost is close to that of traditional A1-based and Zn-based solders. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The differential thermal analysis spectrum of the high elongation SnPbSbInAu alloy solder foil solder prepared in Example 1 of the present invention;

[0051] Figure 2 This is the differential thermal analysis spectrum of the high elongation SnPbSbInAu alloy solder alloy-state filament solder prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0052] The SnPbSbInAu alloy solder with high elongation and the preparation method thereof of the present invention will be further described below in conjunction with an example of specific ingredient calculation.

[0053] Table 1 Ratio of each element in the alloy in Examples 1 to 6

[0054]

[0055] Table 2 Weight of each element and master alloy in Examples 1 to 6

[0056]

[0057] Embodiment 1:

[0058] Step 1: Raw material preparation and master alloy preparation

[0059] According to the alloy composition in Table 1, the raw materials were prepared and weighed according to the designed component ratio. The total feed amount of a single furnace was 100 kg. The vacuum medium frequency induction melting method was selected to prepare Sn-Pb master alloy, Sn-Sb master alloy, Sn-In master alloy, Sn-Au master alloy respectively; the non-vacuum induction melting method was used to prepare Sn-5P master alloy;

[0060] Step (2) Non-vacuum resistance melting

[0061] The weight of each element and the weight of the master alloy prepared in step (1) are calculated according to the weight percentage of each element in the eutectic medium-temperature solder, as shown in Table 2; a non-vacuum resistance melting furnace is used, a high-purity Sn ingot is placed in an alumina crucible of the resistance furnace, and the temperature is raised. After the high-purity Sn ingot is completely melted, SnP5, Sn-In, Sn-Pb, SnSn50, and SnAu50 master alloys are added in sequence. After the master alloy is completely melted, the temperature is lowered to 300° C. (refining), kept warm for 2 minutes, 50 g of water-white rosin is added, the alloy melt is fully stirred, degassing is completed, and surface scum is removed, and the temperature is lowered to 250° C. (die casting);

[0062] Step (3) Rapid cooling pressure casting

[0063] The molten alloy melt obtained in step (2) is subjected to vertical die casting, and a high-purity inert gas is filled into the crucible. The melt flows into and fills the graphite casting mold under the gas pressure, and the alloy ingot is quickly formed. The die casting process maintains the alloy melt temperature at 220°C, the pressure casting temperature at 220°C, the inert gas pressure at 8MPa, the filling speed at 80m / s, the solidification time at less than 1s, and the cooling pipe is connected to the outside of the graphite mold. The cooling medium is ultrapure water, and an alloy ingot with uniform composition and fine IMC is obtained, with a diameter of 30mm and a height of 100mm.

[0064] Step (4) Foil Strip Preparation

[0065] The alloy ingot obtained in step (3) is subjected to a horizontal extruder with an extrusion pressure of 0.8 MPa, an extrusion speed of 200 mm / min, an extrusion ratio of 70, and an extrusion temperature of 5°C to prepare a defect-free slab with a thickness of 1 mm and a width of 10 mm. A 250 two-roller reversible cold rolling mill and a 40 four-roller reversible cold rolling mill are selected, the cold rolling temperature is 25°C, the cold rolling pass processing rate is 15%, and the tension is 5 kN to prepare a foil strip with a thickness of 0.05 mm and a width of 10 mm, which is rolled.

[0066] Step (5) Wire preparation

[0067] The alloy ingot obtained in step (3) is extruded by a horizontal extruder with an extrusion pressure of 10 MPa, an extrusion speed of 100 mm / min, an extrusion ratio of 2000, an extrusion temperature of 5°C, and 5 holes in the extrusion die to produce a wire with a diameter of 0.3 mm, which is then densely wound on a plastic I-shaped shaft.

[0068] Step (6) Preparation of powder paste

[0069] The alloy ingot obtained in step (3) is powdered by vacuum gas atomization, the atomizer is annular, the high-pressure gas is high-purity argon, the atomizing gas pressure is 8 MPa, the injection angle is 60°, the distance from the melt outlet to the atomization point is 2 mm, and a spherical powder with a particle size of 15 μm (D50) is prepared; the flux is a rosin-based resin medium-activity flux, the alloy powder and the flux are in a ratio of 88:12, and a planetary centrifugal degassing is adopted, the centrifugal speed is 800 rpm, and the vacuum in the tank is less than 10 - 1 Pa, to prepare solder paste with no powder separation and moderate viscosity.

[0070] Figure 1The differential thermal curve of SnPbSbInAu alloy solder prepared in Example 1 shows that the melting temperature of the Sn-Pb-Sb-In-Au alloy obtained by the alloy proportion and preparation method designed in the present invention is 182.88-184.83°C, the melting range is 1.95°C, the endothermic peak and exothermic peak curves are smooth and obvious, there is no low-melting point phase precipitation and phase change, and considering the equipment testing accuracy, the alloy melting point can be regarded as 183°C eutectic temperature, which is consistent with Sn-37Pb solder (melting temperature: 183°C), meeting the design requirements of the invention.

[0071] Embodiment 2:

[0072] Step 1: Raw material preparation and master alloy preparation

[0073] According to the alloy composition in Table 1, the raw materials were prepared and weighed according to the designed component ratio. The total feed amount of a single furnace was 100 kg. The vacuum medium frequency induction melting method was selected to prepare Sn-Pb master alloy, Sn-Sb master alloy, Sn-In master alloy, Sn-Au master alloy respectively; the non-vacuum induction melting method was used to prepare Sn-5P master alloy;

[0074] Step (2) Non-vacuum resistance melting

[0075] The weight of each element and the weight of the master alloy prepared in step (1) are calculated according to the weight percentage of each element in the eutectic medium-temperature solder, as shown in Table 2; a non-vacuum resistance melting furnace is used, a high-purity Sn ingot is placed in an alumina crucible of the resistance furnace, and the temperature is raised. After the high-purity Sn ingot is completely melted, SnP5, Sn-In, Sn-Pb, SnSn50, and SnAu50 master alloys are added in sequence. After the master alloy is completely melted, the temperature is lowered to 300° C. (refining), kept warm for 2 minutes, 50 g of water-white rosin is added, the alloy melt is fully stirred, degassing is completed, and surface scum is removed, and the temperature is lowered to 250° C. (die casting);

[0076] Step (3) Rapid cooling pressure casting

[0077] The molten alloy melt obtained in step (2) is subjected to vertical die casting, and a high-purity inert gas is filled into the crucible. The melt flows into and fills the graphite casting mold under the gas pressure, and the alloy ingot is quickly formed. The die casting process maintains the alloy melt temperature at 250°C, the pressure casting temperature at 250°C, the inert gas pressure at 5MPa, the filling speed at 50m / s, the solidification time at less than 1s, and the cooling pipe is connected to the outside of the graphite mold. The cooling medium is ultrapure water, and an alloy ingot with uniform composition and fine IMC is obtained, with a diameter of 150mm and a height of 500mm.

[0078] Step (4) Foil Strip Preparation

[0079] The alloy ingot obtained in step (3) is subjected to a horizontal extruder with an extrusion pressure of 5 MPa, an extrusion speed of 600 mm / min, an extrusion ratio of 30, and an extrusion temperature of 10°C to prepare a defect-free slab with a thickness of 6 mm and a width of 120 mm. A 250 two-roller reversible cold rolling mill and a 40 four-roller reversible cold rolling mill are selected, the cold rolling temperature is 5°C, the cold rolling pass processing rate is 20%, and the tension is 5 kN to prepare a foil strip with a thickness of 0.1 mm and a width of 120 mm, which is rolled.

[0080] Step (5) Wire preparation

[0081] The alloy ingot obtained in step (3) is extruded by a horizontal extruder with an extrusion pressure of 8 MPa, an extrusion speed of 80 mm / min, an extrusion ratio of 1800, an extrusion temperature of 25°C, and a die hole number of 3 to produce a wire with a diameter of 2.0 mm, which is then densely wound on a plastic I-shaped shaft.

[0082] Step (6) Preparation of powder paste

[0083] The alloy ingot obtained in step (3) is powdered by vacuum gas atomization. The atomizer is annular hole type, high-purity argon is selected as the high-pressure gas, the atomizing gas pressure is 9 MPa, the injection angle is 60°, and the distance from the melt outlet to the atomization point is 2 mm. Spherical powder with a particle size of 10 μm (D50) is prepared; the flux is a rosin-based resin medium-activity flux, the alloy powder and the flux are in a ratio of 85:15, and planetary centrifugal degassing is adopted. The centrifugal speed is 500 rpm, and the vacuum in the tank is less than 10 - 1 Pa, to prepare solder paste with no powder separation and moderate viscosity.

[0084] Embodiment 3:

[0085] Step 1: Raw material preparation and master alloy preparation

[0086] According to the alloy composition in Table 1, the raw materials were prepared and weighed according to the designed component ratio. The total feed amount of a single furnace was 100 kg. The vacuum medium frequency induction melting method was selected to prepare Sn-Pb master alloy, Sn-Sb master alloy, Sn-In master alloy, Sn-Au master alloy respectively; the non-vacuum induction melting method was used to prepare Sn-5P master alloy;

[0087] Step (2) Non-vacuum resistance melting

[0088] The weight of each element and the weight of the master alloy prepared in step (1) are calculated according to the weight percentage of each element in the eutectic medium-temperature solder, as shown in Table 2; a non-vacuum resistance melting furnace is used, a high-purity Sn ingot is placed in an alumina crucible of the resistance furnace, and the temperature is raised. After the high-purity Sn ingot is completely melted, SnP5, Sn-In, Sn-Pb, SnSn50, and SnAu50 master alloys are added in sequence. After the master alloy is completely melted, the temperature is lowered to 300° C. (refining), kept warm for 2 minutes, 50 g of water-white rosin is added, the alloy melt is fully stirred, degassing is completed, and surface scum is removed, and the temperature is lowered to 250° C. (die casting);

[0089] Step (3) Rapid cooling pressure casting

[0090] The molten alloy melt obtained in step (2) is subjected to vertical die casting, and a high-purity inert gas is filled into the crucible. The melt flows into and fills the graphite casting mold under the gas pressure, and the alloy ingot is quickly formed. The die casting process maintains the alloy melt temperature at 230°C, the pressure casting temperature at 230°C, the inert gas pressure at 7MPa, the filling speed at 60m / s, the solidification time at less than 1s, and the cooling pipe is connected to the outside of the graphite mold. The cooling medium is ultrapure water, and an alloy ingot with uniform composition and fine IMC is obtained, with a diameter of 60mm and a height of 120mm.

[0091] Step (4) Foil Strip Preparation

[0092] The alloy ingot obtained in step (3) is subjected to a horizontal extruder with an extrusion pressure of 4 MPa, an extrusion speed of 300 mm / min, an extrusion ratio of 35, and an extrusion temperature of 25°C to prepare a defect-free slab with a thickness of 2 mm and a width of 40 mm. A 250 two-roller reversible cold rolling mill and a 40 four-roller reversible cold rolling mill are selected, the cold rolling temperature is 20°C, the cold rolling pass processing rate is 15%, and the tension is 0 kN to prepare a foil strip with a thickness of 0.05 mm and a width of 40 mm, which is rolled.

[0093] Step (5) Wire preparation

[0094] The alloy ingot obtained in step (3) is subjected to a horizontal extruder with an extrusion pressure of 8 MPa, an extrusion speed of 150 mm / min, an extrusion ratio of 300, an extrusion temperature of 25°C, and a die hole number of 3 to prepare a wire with a diameter of 1.0 mm, which is then closely wound on a plastic I-shaped shaft.

[0095] Step (6) Preparation of powder paste

[0096] The alloy ingot obtained in step (3) is powdered by vacuum gas atomization, the atomizer is annular, the high-pressure gas is high-purity argon, the atomizing gas pressure is 8.5 MPa, the injection angle is 60°, the distance from the melt outlet to the atomization point is 2 mm, and a spherical powder with a particle size of 12 μm (D50) is prepared; the flux is a rosin-based resin medium-activity flux, the alloy powder and the flux are in a ratio of 90:10, and planetary centrifugal degassing is adopted, the centrifugal speed is 1500 rpm, and the vacuum in the tank is less than 10 -1 Pa, to prepare solder paste with no powder separation and moderate viscosity.

[0097] Embodiment 4:

[0098] Step 1: Raw material preparation and master alloy preparation

[0099] According to the alloy composition in Table 1, the raw materials were prepared and weighed according to the designed component ratio. The total feed amount of a single furnace was 100 kg. The vacuum medium frequency induction melting method was selected to prepare Sn-Pb master alloy, Sn-Sb master alloy, Sn-In master alloy, Sn-Au master alloy respectively; the non-vacuum induction melting method was used to prepare Sn-5P master alloy;

[0100] Step (2) Non-vacuum resistance melting

[0101] The weight of each element and the weight of the master alloy prepared in step (1) are calculated according to the weight percentage of each element in the eutectic medium-temperature solder, as shown in Table 2; a non-vacuum resistance melting furnace is used, a high-purity Sn ingot is placed in an alumina crucible of the resistance furnace, and the temperature is raised. After the high-purity Sn ingot is completely melted, SnP5, Sn-In, Sn-Pb, SnSn50, and SnAu50 master alloys are added in sequence. After the master alloy is completely melted, the temperature is lowered to 300° C. (refining), kept warm for 2 minutes, 50 g of water-white rosin is added, the alloy melt is fully stirred, degassing is completed, and surface scum is removed, and the temperature is lowered to 250° C. (die casting);

[0102] Step (3) Rapid cooling pressure casting

[0103] The molten alloy melt obtained in step (2) is subjected to vertical die casting. A high-purity inert gas is filled into the crucible. The melt flows into and fills the graphite casting mold under the gas pressure to quickly complete the alloy ingot molding. The die casting process maintains the alloy melt temperature at 250°C, the pressure casting temperature at 250°C, the inert gas pressure at 8MPa, the filling speed at 80m / s, the solidification time at less than 1s, and the cooling pipe is connected to the outside of the graphite mold. The cooling medium is ultrapure water. An alloy ingot with uniform composition and fine IMC is obtained, with a diameter of 80mm and a height of 250mm.

[0104] Step (4) Foil Strip Preparation

[0105] The alloy ingot obtained in step (3) is subjected to a horizontal extruder with an extrusion pressure of 4 MPa, an extrusion speed of 500 mm / min, an extrusion ratio of 33, and an extrusion temperature of 15°C to prepare a defect-free slab with a thickness of 2 mm and a width of 75 mm. A 250 two-roller reversible cold rolling mill and a 40 four-roller reversible cold rolling mill are selected, the cold rolling temperature is 5°C, the cold rolling pass processing rate is 15%, and the tension is 5 kN to prepare a foil strip with a thickness of 0.08 mm and a width of 70 mm, which is rolled.

[0106] Step (5) Wire preparation

[0107] The alloy ingot obtained in step (3) is extruded by a horizontal extruder with an extrusion pressure of 9 MPa, an extrusion speed of 120 mm / min, an extrusion ratio of 2000, an extrusion temperature of 15°C, and 5 holes in the extrusion die to produce a wire with a diameter of 0.8 mm, which is then densely wound on a plastic I-shaped shaft.

[0108] Step (6) Preparation of powder paste

[0109] The alloy ingot obtained in step (3) is powdered by vacuum gas atomization. The atomizer is annular hole type, high-purity argon is selected as the high-pressure gas, the atomizing gas pressure is 9 MPa, the injection angle is 60°, and the distance from the melt outlet to the atomization point is 2 mm. Spherical powder with a particle size of 10 μm (D50) is prepared; the flux is a rosin-based resin medium-activity flux, the alloy powder and the flux are in a ratio of 85:15, and planetary centrifugal degassing is adopted. The centrifugal speed is 500 rpm, and the vacuum in the tank is less than 10 - 1 Pa, to prepare solder paste with no powder separation and moderate viscosity.

[0110] Figure 2 The differential thermal curve of SnPbSbInAu alloy solder prepared in Example 4 shows that the melting temperature of the Sn-Pb-Sb-In-Au alloy obtained by the alloy proportion and preparation method designed in the present invention is 180.27-182.82°C, the melting range is 2.55°C, the endothermic peak and exothermic peak curves are smooth and obvious, there is no low-melting point phase precipitation and phase change, and considering the equipment testing accuracy, the alloy melting point can be regarded as 181°C eutectic temperature, which is 2°C lower than the Sn-37Pb solder (melting temperature: 183°C), meeting the design requirements of the invention.

[0111] Embodiment 5:

[0112] Step 1: Raw material preparation and master alloy preparation

[0113] According to the alloy composition in Table 1, the raw materials were prepared and weighed according to the designed component ratio. The total feed amount of a single furnace was 100 kg. The vacuum medium frequency induction melting method was selected to prepare Sn-Pb master alloy, Sn-Sb master alloy, Sn-In master alloy, Sn-Au master alloy respectively; the non-vacuum induction melting method was used to prepare Sn-5P master alloy;

[0114] Step (2) Non-vacuum resistance melting

[0115] The weight of each element and the weight of the master alloy prepared in step (1) are calculated according to the weight percentage of each element in the eutectic medium-temperature solder, as shown in Table 2; a non-vacuum resistance melting furnace is used, a high-purity Sn ingot is placed in an alumina crucible of the resistance furnace, and the temperature is raised. After the high-purity Sn ingot is completely melted, SnP5, Sn-In, Sn-Pb, SnSn50, and SnAu50 master alloys are added in sequence. After the master alloy is completely melted, the temperature is lowered to 300° C. (refining), kept warm for 2 minutes, 50 g of water-white rosin is added, the alloy melt is fully stirred, degassing is completed, and surface scum is removed, and the temperature is lowered to 250° C. (die casting);

[0116] Step (3) Rapid cooling pressure casting

[0117] The molten alloy melt obtained in step (2) is subjected to vertical die casting. A high-purity inert gas is filled into the crucible. The melt flows into and fills the graphite casting mold under the gas pressure to quickly complete the alloy ingot molding. The die casting process maintains the alloy melt temperature at 220°C, the pressure casting temperature at 220°C, the inert gas pressure at 5MPa, the filling speed at 50m / s, the solidification time at less than 1s, and the cooling pipe is connected to the outside of the graphite mold. The cooling medium is ultrapure water, and an alloy ingot with uniform composition and fine IMC is obtained, with a diameter of 50mm and a height of 120mm.

[0118] Step (4) Foil Strip Preparation

[0119] The alloy ingot obtained in step (3) is subjected to a horizontal extruder with an extrusion pressure of 3 MPa, an extrusion speed of 300 mm / min, an extrusion ratio of 50, and an extrusion temperature of 25°C to prepare a defect-free slab with a thickness of 1 mm and a width of 40 mm. A 250 two-roller reversible cold rolling mill and a 40 four-roller reversible cold rolling mill are selected, the cold rolling temperature is 15°C, the cold rolling pass processing rate is 18%, and the tension is 2.5 kN to prepare a foil strip with a thickness of 0.05 mm and a width of 40 mm, which is rolled.

[0120] Step (5) Wire preparation

[0121] The alloy ingot obtained in step (3) is extruded by a horizontal extruder with an extrusion pressure of 5 MPa, an extrusion speed of 100 mm / min, an extrusion ratio of 400, an extrusion temperature of 10°C, and 5 holes in the extrusion die to produce a wire with a diameter of 1.2 mm, which is then densely wound on a plastic I-shaped shaft.

[0122] Step (6) Preparation of powder paste

[0123] The alloy ingot obtained in step (3) is powdered by vacuum gas atomization, the atomizer is annular, the high-pressure gas is high-purity argon, the atomizing gas pressure is 8 MPa, the injection angle is 60°, the distance from the melt outlet to the atomization point is 2 mm, and a spherical powder with a particle size of 15 μm (D50) is prepared; the flux is a rosin-based resin medium-activity flux, the alloy powder and the flux are in a ratio of 87:13, and a planetary centrifugal degassing is adopted, the centrifugal speed is 800 rpm, and the vacuum in the tank is less than 10 - 1 Pa, to prepare solder paste with no powder separation and moderate viscosity.

[0124] Embodiment 6:

[0125] Step 1: Raw material preparation and master alloy preparation

[0126] According to the alloy composition in Table 1, the raw materials were prepared and weighed according to the designed component ratio. The total feed amount of a single furnace was 100 kg. The vacuum medium frequency induction melting method was selected to prepare Sn-Pb master alloy, Sn-Sb master alloy, Sn-In master alloy, Sn-Au master alloy respectively; the non-vacuum induction melting method was used to prepare Sn-5P master alloy;

[0127] Step (2) Non-vacuum resistance melting

[0128] The weight of each element and the weight of the master alloy prepared in step (1) are calculated according to the weight percentage of each element in the eutectic medium-temperature solder, as shown in Table 2; a non-vacuum resistance melting furnace is used, a high-purity Sn ingot is placed in an alumina crucible of the resistance furnace, and the temperature is raised. After the high-purity Sn ingot is completely melted, SnP5, Sn-In, Sn-Pb, SnSn50, and SnAu50 master alloys are added in sequence. After the master alloy is completely melted, the temperature is lowered to 300° C. (refining), kept warm for 2 minutes, 50 g of water-white rosin is added, the alloy melt is fully stirred, degassing is completed, and surface scum is removed, and the temperature is lowered to 250° C. (die casting);

[0129] Step (3) Rapid cooling pressure casting

[0130] The molten alloy melt obtained in step (2) is subjected to vertical die casting. A high-purity inert gas is filled into the crucible. The melt flows into and fills the graphite casting mold under the gas pressure to quickly complete the alloy ingot molding. The die casting process maintains the alloy melt temperature at 240°C, the pressure casting temperature at 240°C, the inert gas pressure at 6MPa, the filling speed at 60m / s, the solidification time at less than 1s, and the cooling pipe is connected to the outside of the graphite mold. The cooling medium is ultrapure water. An alloy ingot with uniform composition and fine IMC is obtained, with a diameter of 30mm and a height of 500mm.

[0131] Step (4) Foil Strip Preparation

[0132] The alloy ingot obtained in step (3) is subjected to a horizontal extruder with an extrusion pressure of 5 MPa, an extrusion speed of 300 mm / min, an extrusion ratio of 35, and an extrusion temperature of 20°C to prepare a defect-free slab with a thickness of 1 mm and a width of 20 mm. A 250 two-roller reversible cold rolling mill and a 40 four-roller reversible cold rolling mill are selected, the cold rolling temperature is 20°C, the cold rolling pass processing rate is 20, and the tension is 5 kN to prepare a foil strip with a thickness of 0.03 mm and a width of 20 mm, which is rolled.

[0133] Step (5) Wire preparation

[0134] The alloy ingot obtained in step (3) is extruded by a horizontal extruder with an extrusion pressure of 4 MPa, an extrusion speed of 80 mm / min, an extrusion ratio of 1200, an extrusion temperature of 20°C, and 5 holes in the extrusion die to produce a wire with a diameter of 0.5 mm, which is then densely wound on a plastic I-shaped shaft.

[0135] Step (6) Preparation of powder paste

[0136] The alloy ingot obtained in step (3) is powdered by vacuum gas atomization, the atomizer is annular, the high-pressure gas is high-purity argon, the atomizing gas pressure is 9 MPa, the injection angle is 60°, the distance from the melt outlet to the atomization point is 2 mm, and a spherical powder with a particle size of 11 μm (D50) is prepared; the flux is a rosin-based resin medium-activity flux, the alloy powder and the flux are in a ratio of 90:10, and planetary centrifugal degassing is adopted, the centrifugal speed is 1000 rpm, and the vacuum in the tank is less than 10 - 1 Pa, to prepare solder paste with no powder separation and moderate viscosity.

[0137] Experimental Example 1

[0138] The high-strength and high-elongation SnPbSbInAu alloy solders prepared in Examples 1-6 were tested for melting point, wettability (gold-plated layer), elongation, shear strength (oxygen-free copper substrate), etc. The test data obtained are shown in Table 3.

[0139] Table 3 Performance of high elongation SnPbSbInAu alloy solders of Examples 1 to 6

[0140] Example Melting temperature Brazing temperature Wetting Angle Elongation Tensile shear strength 1 182.88～184.83℃ 205℃ 15.2° 110％ 89MPa 2 182.01～183.98℃ 205℃ 15.5° 110％ 86MPa 3 180.75～183.14℃ 205℃ 16.8° 110％ 81MPa 4 180.27～182.82℃ 205℃ 15.2° 110％ 85MPa 5 180.65～184.86℃ 205℃ 19.2° 110％ 78MPa 6 181.31～184.09℃ 205℃ 16.7° 110％ 83MPa

[0141] The results in Table 3 show that the SnPbSbInAu alloy solders of Examples 1-6 have low melting temperatures and short melting ranges, which are close to those of Sn-37Pb solder (melting temperature: 183°C), high elongation, good wettability to Au-plated and oxygen-free copper, high tensile shear strength, good brazing processability, and long service life, and are particularly suitable for microelectronic packaging of electronic products in high-reliability application scenarios and high-strength and low-temperature brazing requirements of lightweight alloys.

[0142] The above embodiments only illustrate the embodiments of the high-strength and high-elongation SnPbSbInAu alloy solder part of the present invention. In the above technical scheme of the present invention: the content of metal elements in the solder alloy can be freely selected within the prescribed range, and they are no longer listed here one by one. Therefore, the technical scheme contained in the above description should be regarded as illustrative rather than used to limit the scope of protection of the present invention.

Claims

1. A high-strength and high-elongation SnPbSbInAu alloy solder, characterized in that: The invention is composed of the following components: Pb 33.0-36.5wt%, Sb 2.0-4.0wt%, In 1.5-3.5wt%, Au 2.0-3.5wt%, P 0.005-0.012wt%, and the balance is Sn.

2. The high-strength and high-elongation SnPbSbInAu alloy solder according to claim 1, characterized in that: The content of Pb is 34.0-35.0wt%, the content of Sb is 2.8-3.5wt%, the content of In is 2.2-2.8wt%, the content of Au is 2.5-3.2wt%, the content of P is 0.008-0.01wt%, and the balance is Sn.

3. The method for preparing the high-strength and high-elongation SnPbSbInAu alloy solder according to claim 1 or 2, characterized in that: The method comprises the following steps: I. Raw material selection and master alloy preparation According to the composition of the high-strength and high-elongation SnPbSbInAu alloy solder, high-purity Sn, Pb, Sb, In, Au and P are used as raw materials; The Sn-Pb master alloy, Sn-Sb master alloy, Sn-In master alloy and Sn-Au master alloy were prepared by vacuum medium frequency induction melting method; the Sn-P master alloy was prepared by non-vacuum induction melting method; II. Non-vacuum resistance melting The master alloy prepared in step I is used to calculate the weight of each element and the weight of the master alloy according to the weight percentage of each element in the eutectic medium-temperature solder; a resistance melting furnace is used to put the Sn ingot into the alumina crucible of the resistance melting furnace, and the temperature is raised. After the Sn ingot is completely melted, SnP, SnPb, SnSb, SnAu, and SnIn master alloys are added in sequence. After the master alloy is completely melted, the temperature is lowered to the refining temperature, and after the temperature is kept, water-white hydrogenated rosin is added, the alloy melt is fully stirred, degassing is completed, and surface scum is removed, and the temperature is raised to the die-casting temperature and kept warm; III. Rapid Cooling Pressure Casting The molten alloy melt obtained in step II is subjected to vertical die casting. A high-purity inert gas is filled into the crucible. The melt flows into and fills the graphite casting mold under the gas pressure to quickly complete the alloy ingot molding to obtain an alloy ingot with uniform composition and fine IMC, with a size of 30 to 150 mm in diameter and 100 to 500 mm in height; IV. Solder Forming A. Foil Strip Preparation The alloy ingot obtained in step III is subjected to a horizontal extruder to prepare a defect-free slab with a thickness of 1 to 6 mm and a width of 10 to 120 mm; the slab is subjected to cold rolling to prepare a foil strip with a thickness of 0.03 to 0.1 mm and a width of 10 to 120 mm, which is rolled into a coil; B. Wire Preparation The alloy ingot obtained in step III is formed in one step by a horizontal extruder to prepare a wire with a diameter of 0.3 to 2.0 mm, which is densely wound on a plastic I-shaped shaft; C. Preparation of powder paste The alloy ingot obtained in step III is subjected to vacuum gas atomization to prepare spherical powder with a particle size of 10-15 μm (D50), and is combined with low-temperature flux and planetary centrifugal degassing to prepare a solder paste with no powder separation and moderate viscosity.

4. The preparation method according to claim 3, characterized in that: According to mass percentage, the purity of Sn is 99.999%, the purity of Pb is 99.999%, the purity of Sb is 99.999%, the purity of Au is 99.999%, the purity of In is 99.999%, and the purity of P is 99.99%.

5. The preparation method according to claim 3, characterized in that: The content of Pb in the Sn-Pb master alloy is 50wt%, and the balance is Sn; the content of Sb in the Sn-Sb master alloy is 50wt%, and the balance is Sn; the content of In in the Sn-In master alloy is 50wt%, and the balance is Sn; the content of Au in the Sn-Au master alloy is 80wt%, and the balance is Sn; the content of P in the Sn-P master alloy is 5wt%, and the balance is Sn.

6. The preparation method according to claim 3, characterized in that: The refining temperature of step II is 280-300° C., the holding time is 2-5 min, and the amount of hydrogenated rosin added is 0.05 wt % of the total amount of alloy feed.

7. The preparation method according to claim 3, characterized in that: The pressure casting temperature of step III is 220-250° C., the inert gas pressure is 5-8 MPa, the filling speed is 50-80 m / s, the solidification time is less than 1 s, the outside of the graphite mold is connected with a cooling pipe, and the cooling medium is ultrapure water.

8. The preparation method according to claim 3, characterized in that: The foil strip preparation process in step A adopts a horizontal extruder with an extrusion pressure of 0.5-5MPa, an extrusion speed of 200-600mm / min, an extrusion ratio of 30-100, and an extrusion temperature of 5-25°C; the cold rolling process uses a two-roll reversible cold rolling mill and a four-roll reversible cold rolling mill, the cold rolling temperature is 5°C-25°C, the cold rolling pass processing rate is 15%-20%, and the tension is 0-5kN.

9. The preparation method according to claim 3, characterized in that: The wire material preparation process in step B adopts a horizontal extruder with an extrusion force of 4-10 MPa, an extrusion speed of 80-200 mm / min, an extrusion ratio of 45-2000, an extrusion temperature of 5-25° C., and 3-5 holes in the extrusion die.

10. The preparation method according to claim 3, characterized in that: In the step C of preparing the powder paste, the atomizer is an annular hole type, the high-pressure gas is high-purity argon gas, the atomizing gas pressure is 8-9 MPa, the injection angle is 60°, the distance from the melt outlet to the atomization point is 2 mm, the flux is a rosin-based resin medium-activity flux, the alloy powder and the flux are in a ratio of (85-90): (10-15), the solder paste is prepared by planetary centrifugal degassing, the centrifugal speed is 500-1500 rpm, and the vacuum in the tank is less than 10 -1 Pa.

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