A low-melting-point soldering filler metal and its preparation method

Abstract

The present invention provides a soldering filler metal with a low melting point and a preparation method thereof, belonging to the technical field of welding materials. A preparation method of a soldering filler metal with a low melting point comprises the following steps: Sn particles and Zn particles are cooled after being subjected to a first melting heat treatment in an inert gas protection environment to obtain intermediate 1, Sn particles and Mn particles are cooled after being subjected to a second melting heat treatment in an inert gas protection environment to obtain intermediate 2, Sn particles and Hf particles are cooled after being subjected to a third melting heat treatment in an inert gas protection environment to obtain intermediate 3, and the welding filler metal is obtained by subjecting intermediate 1, intermediate 2, intermediate 3 and Bi particles to ball milling and mixing, and then performing high-pressure sintering and quenching and unloading pressing. The present invention ingeniously incorporates three elements, Bi, Mn and Hf, into the soldering filler metal with a low melting point. These three elements cooperate with each other, complement each other and work together to improve the wettability and corrosion resistance of the soldering filler metal with a low melting point.

Description

Technical Field

[0001] The invention belongs to the technical field of welding materials, and in particular relates to a low melting point welding brazing filler metal and a preparation method thereof. Background Art

[0002] Among the various types of lead-free solders, Sn-Zn solders have gradually emerged with their significant advantages and have become a potential competitor in the field of lead-free solders. They are relatively low-cost, effectively reducing production inputs, and meeting the cost control needs of large-scale industrial applications; their melting point is very close to that of traditional Sn-Pb solders, and in practical applications, there is no need to make major adjustments to existing welding processes and equipment, greatly reducing the cost of process changes and technical difficulties; at the same time, Sn-Zn solders also have excellent mechanical properties and can meet the requirements for welding strength and stability under various complex working conditions.

[0003] However, Sn-Zn solder also has obvious shortcomings. It has poor wettability with the copper surface, which makes it difficult to spread evenly on the copper surface during welding, seriously affecting the firmness and quality stability of welding; Zn element is chemically active and easily oxidized, resulting in reduced solder performance; and Sn-Zn solder has poor corrosion resistance and is easily corroded in complex working environments, greatly shortening the service life of the welded joint. These shortcomings are like insurmountable obstacles, which seriously restrict the further development and widespread application of Sn-Zn lead-free solder.

[0004] Therefore, providing a welding brazing material with good corrosion resistance and low melting point is an important problem to be solved in the art. Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a low melting point solder and a preparation method thereof. Specifically, the technical solution of the present invention includes the following contents:

[0006] A method for preparing a low melting point solder, the method comprising the following steps:

[0007] Sn particles and Zn particles are subjected to a first smelting heat treatment in an inert gas protective environment and then cooled to obtain intermediate 1, Sn particles and Mn particles are subjected to a second smelting heat treatment in an inert gas protective environment and then cooled to obtain intermediate 2, Sn particles and Hf particles are subjected to a third smelting heat treatment in an inert gas protective environment and then cooled to obtain intermediate 3, intermediate 1, intermediate 2, intermediate 3 and Bi particles are mixed by ball milling, and then sintered under high pressure and quenched to release the pressure to obtain the welding brazing material.

[0008] Furthermore, the purity of the Zn particles is 99.9%.

[0009] Further, the purity of the Sn particles is 99.99%.

[0010] Further, the inert gas includes nitrogen or argon.

[0011] Further, the melting temperature of the first melting is 450 - 550 °C, and the melting time is 30 - 60 min.

[0012] Further, the melting temperature of the second melting is 1300 - 1500 °C, and the melting time is 40 - 60 min.

[0013] Further, the melting temperature of the third melting is 2300 - 2500 °C, and the melting time is 80 - 100 min.

[0014] Further, the environment for ball milling is an argon or nitrogen protection environment.

[0015] Further, the ball - to - material ratio for ball milling is 10:1 - 2.

[0016] Further, the rotation speed of ball milling is 100 - 200 r / min

[0017] Further, the time for ball milling is 8 - 10 h.

[0018] Further, the temperature for high - pressure sintering is 900 - 1200 °C.

[0019] Further, the pressure for high - pressure sintering is 3 - 4 GPa.

[0020] Further, the time for high - pressure sintering is 45 - 70 min.

[0021] Further, the soldering filler metal, by weight percentage, comprises the following components: 9.0% Zn, 2.5 - 3.5% Mn, 1.8 - 2.6% Bi, 0.01 - 0.5% Hf, and the balance Sn.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) In the present invention, Bi can effectively reduce the melting point of the solder and improve the wettability of the solder; the addition of Hf has a significant effect on improving the corrosion resistance of the solder. On the one hand, Hf can enhance the stability of Zn and effectively reduce the dissolution rate of Zn in the corrosive medium; on the other hand, the addition of Hf increases the content of the oxide film and enhances the stability of the oxide film, thereby improving the stability of the solder and thus enhancing the corrosion resistance of the solder; Mn can effectively reduce the surface tension of the solder, while Hf can refine the grains and homogenize the microstructure. Under the synergistic effect of the two, the solder can be spread more quickly and evenly on the surface of the base material, thereby improving the welding quality; the present invention ingeniously integrates the three elements of Bi, Mn and Hf into the solder with a low melting point. These three elements cooperate with each other, complement each other, and work together to improve the wettability and corrosion resistance of the solder with a low melting point, making the welding joint more firm and reliable, and significantly improving the welding quality.

[0024] (2) The preparation method provided by the present invention has an exquisite process design. In the preparation process, Zn, Mn, and Hf are first placed in a high-temperature environment to react with Sn respectively, thereby obtaining intermediates 1, 2, and 3. This step promotes the full fusion of the elements and lays the foundation for subsequent performance improvement; then the intermediates 1, 2, and 3 are subjected to high-pressure sintering with Bi. In the high-pressure environment, the substances are in close contact, and the atoms diffuse and recombine with each other, making the structure of the prepared welding brazing material more compact, greatly reducing internal defects, and enhancing the intermolecular force, thereby further enhancing its corrosion resistance. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0026] Unless otherwise specified, the raw materials and reagents used in the present invention are commercially available or can be prepared by known methods.

[0027] Example 1: A low melting point solder comprises the following components by weight percentage: 9.0% Zn, 3.5% Mn, 1.8% Bi, 0.01% Hf and the balance Sn. The specific preparation method comprises the following steps:

[0028] Weigh Sn particles with a purity of 99.99% and Zn particles with a purity of 99.9% according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 3×10 -2After reaching 0.1 Pa, nitrogen is filled until the pressure reaches 0.1 MPa, and the first melting heat treatment is carried out at a temperature of 450 °C for 30 min in a nitrogen protection environment, and then cooled to obtain intermediate 1; Weigh Sn particles and Mn particles with a purity of 99.99% according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 3×10 -2 After reaching 0.1 Pa, nitrogen is filled until the pressure reaches 0.1 MPa, and the second melting heat treatment is carried out at a temperature of 1300 °C for 40 min in a nitrogen protection environment, and then cooled to obtain intermediate 2; Weigh Sn particles and Hf particles with a purity of 99.99% according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 3×10 -2 After reaching 0.1 Pa, nitrogen is filled until the pressure reaches 0.1 MPa, and the third melting heat treatment is carried out at a temperature of 2300 °C for 60 min in a nitrogen protection environment, and then cooled to obtain intermediate 3; In a nitrogen protection environment, intermediate 1, intermediate 2, intermediate 3 and Bi particles are ball-milled and mixed at a ball-to-material ratio of 10:1 at a rotation speed of 100 r / min for 8 h to obtain a mixture. The mixture is molded by a press in a mold at a pressure of 400 MPa to obtain a green compact. In a nitrogen protection environment, the temperature is raised at a heating rate of 100 °C / min. When the temperature rises to 500 °C, it is maintained at a pressure of 200 MPa for 30 min, then the pressure is increased to 3 GPa, and the temperature is further raised to 1000 °C. After holding for 15 min, it is quenched and depressurized to obtain a welding filler metal.

[0029] Example 2: A low-melting-point welding filler metal, comprising the following components by weight percentage: 9.0% of Zn, 2.5% of Mn, 2.2% of Bi, 0.1% of Hf, and the balance of Sn. The specific preparation method includes the following steps:

[0030] Weigh Sn particles with a purity of 99.99% and Zn particles with a purity of 99.9% according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 3.2×10 -2 After reaching 0.1 Pa, argon is filled until the pressure reaches 0.18 MPa, and the first melting heat treatment is carried out at a temperature of 480 °C for 40 min in an argon protection environment, and then cooled to obtain intermediate 1; Weigh Sn particles and Mn particles with a purity of 99.99% according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 3.3×10 -2 After reaching 0.1 Pa, argon is filled until the pressure reaches 0.17 MPa, and the second melting heat treatment is carried out at a temperature of 1400 °C for 45 min in an argon protection environment, and then cooled to obtain intermediate 2; Weigh Sn particles and Hf particles with a purity of 99.99% according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 3.4×10 -2After reaching 3.8×10

[0031] Example 3: A low-melting soldering filler metal, comprising the following components by weight percentage: 9.0% Zn, 3.0% Mn, 2.2% Bi, 0.3% Hf, and the balance Sn. The specific preparation method comprises the following steps:

[0032] Weigh Sn particles with a purity of 99.99% and Zn particles with a purity of 99.9% according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 3.8×10 -2 Pa, then fill it with argon until the pressure reaches 0.25 MPa, and perform the first melting heat treatment at a temperature of 520 °C for 50 min in an argon protection environment, and then cool to obtain intermediate 1; Weigh Sn particles with a purity of 99.99% and Mn particles according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 3.7×10 -2 Pa, then fill it with argon until the pressure reaches 0.2 MPa, and perform the second melting heat treatment at a temperature of 1450 °C for 50 min in an argon protection environment, and then cool to obtain intermediate 2; Weigh Sn particles with a purity of 99.99% and Hf particles according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 3.5×10 -2 Pa, then fill it with argon until the pressure reaches 0.2 MPa, and perform the third melting heat treatment at a temperature of 2400 °C for 80 min in an argon protection environment, and then cool to obtain intermediate 3; In an argon protection environment, mix intermediate 1, intermediate 2, intermediate 3 and Bi particles according to a ball-to-material ratio of 10:1.8 and ball-mill and mix them at a rotation speed of 180 r / min for 9 h to obtain a mixture. Use a tablet press to press the mixture into a compact in a mold at a pressure of 400 MPa. In an argon protection environment, heat it up at a heating rate of 100-120 °C / min. When the temperature rises to 500 °C, maintain it at a pressure of 270 MPa for 50 min, then pressurize it to 3.5 GPa, and then raise the temperature to 1200 °C, keep it warm for 12 min, and then quench and release the pressure to obtain the soldering filler metal.

[0033] Example 4: A low-melting soldering filler metal, comprising the following components by weight percentage: 9.0% Zn, 3.0% Mn, 2.6% Bi, 0.5% Hf, and the balance Sn. The specific preparation method includes the following steps:

[0034] Weigh Sn particles with a purity of 99.99% and Zn particles with a purity of 99.9% according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 4×10 -2 Pa, then fill it with nitrogen until the pressure reaches 0.3 MPa. Conduct the first melting heat treatment at a temperature of 550 °C for 60 min in a nitrogen protection environment and then cool to obtain intermediate 1. Weigh Sn particles with a purity of 99.99% and Mn particles according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 4×10 -2 Pa, then fill it with nitrogen until the pressure reaches 0.3 MPa. Conduct the second melting heat treatment at a temperature of 1500 °C for 60 min in a nitrogen protection environment and then cool to obtain intermediate 2. Weigh Sn particles with a purity of 99.99% and Hf particles according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 4×10 -2 Pa, then fill it with nitrogen until the pressure reaches 0.3 MPa. Conduct the third melting heat treatment at a temperature of 2500 °C for 90 min in a nitrogen protection environment and then cool to obtain intermediate 3. In a nitrogen protection environment, mix intermediate 1, intermediate 2, intermediate 3, and Bi particles according to a ball-to-material ratio of 10:2 and ball-mill and mix them at a rotation speed of 200 r / min for 10 h to obtain a mixture. Use a tablet press to mold the mixture in a mold at a pressure of 400 MPa to obtain a green compact. In a nitrogen protection environment, heat it up at a heating rate of 120 °C / min. When the temperature rises to 500 °C, maintain the pressure at 300 MPa for 60 min, then increase the pressure to 4 GPa, and then raise the temperature to 1300 °C, keep it warm for 10 min, and then quench and release the pressure to obtain the soldering filler metal.

[0035] Comparative Example 1: A low-melting soldering filler metal, comprising the following components by weight percentage: 9.0% Zn, 2.6% Bi, 0.5% Hf, and the balance Sn. The specific preparation method includes the following steps:

[0036] Weigh Sn particles with a purity of 99.99% and Zn particles with a purity of 99.9% according to a certain weight percentage and put them into a quartz tube. Reduce the vacuum degree in the quartz tube to 4×10 -2After reaching -2 Pa, nitrogen is filled until the pressure reaches 0.3 MPa, and the first melting heat treatment is carried out at a temperature of 550 °C for 60 min in a nitrogen protection environment, and then cooled to obtain intermediate 1; Weigh Sn particles and Hf particles with a purity of 99.99% according to a certain weight percentage and put them into a quartz tube, and reduce the vacuum degree in the quartz tube to 4×10

[0037] Comparative Example 2: A low-melting soldering filler metal, which comprises the following components by weight percentage: 9.0% of Zn, 3.0% of Mn, 0.5% of Hf and the balance of Sn. The specific preparation method comprises the following steps:

[0038] Weigh Sn particles with a purity of 99.99% and Zn particles with a purity of 99.9% according to a certain weight percentage and put them into a quartz tube, and reduce the vacuum degree in the quartz tube to 4×10 -2 Pa, nitrogen is filled until the pressure reaches 0.3 MPa, and the first melting heat treatment is carried out at a temperature of 550 °C for 60 min in a nitrogen protection environment, and then cooled to obtain intermediate 1; Weigh Sn particles and Mn particles with a purity of 99.99% according to a certain weight percentage and put them into a quartz tube, and reduce the vacuum degree in the quartz tube to 4×10 -2 Pa, nitrogen is filled until the pressure reaches 0.3 MPa, and the second melting heat treatment is carried out at a temperature of 1500 °C for 60 min in a nitrogen protection environment, and then cooled to obtain intermediate 2; Weigh Sn particles and Hf particles with a purity of 99.99% according to a certain weight percentage and put them into a quartz tube, and reduce the vacuum degree in the quartz tube to 4×10 -2After reaching 0.3 MPa, nitrogen gas was filled until the pressure reached 0.3 MPa, and the third melting heat treatment was carried out at a temperature of 2500 °C for 90 min in a nitrogen gas protection environment, and then cooled to obtain intermediate 3; in a nitrogen gas protection environment, intermediate 1, intermediate 2 and intermediate 3 were ball-milled and mixed at a ball-to-material ratio of 10:2 at a rotation speed of 200 r / min for 10 h to obtain a mixture, and the mixture was molded by a tablet press in a mold at a pressure of 400 MPa to obtain a green compact. In a nitrogen gas protection environment, the temperature was raised at a heating rate of 120 °C / min. When the temperature reached 500 °C, it was maintained at a pressure of 300 MPa for 60 min, then the pressure was increased to 4 GPa, and the temperature was further raised to 1300 °C. After holding for 10 min, it was quenched and depressurized to obtain the welding filler metal.

[0039] Comparative Example 3: A low-melting-point welding filler metal, comprising the following components by weight percentage: 9.0% of Zn, 3.0% of Mn, 2.6% of Bi and the balance of Sn. The specific preparation method comprises the following steps:

[0040] Weigh Sn particles with a purity of 99.99% and Zn particles with a purity of 99.9% according to a certain weight percentage and put them into a quartz tube. The vacuum degree in the quartz tube was reduced to 4×10 -2 After reaching 0.3 MPa, nitrogen gas was filled until the pressure reached 0.3 MPa, and the first melting heat treatment was carried out at a temperature of 550 °C for 60 min in a nitrogen gas protection environment, and then cooled to obtain intermediate 1; weigh Sn particles with a purity of 99.99% and Mn particles according to a certain weight percentage and put them into a quartz tube. The vacuum degree in the quartz tube was reduced to 4×10 -2 After reaching 0.3 MPa, nitrogen gas was filled until the pressure reached 0.3 MPa, and the second melting heat treatment was carried out at a temperature of 1500 °C for 60 min in a nitrogen gas protection environment, and then cooled to obtain intermediate 2; in a nitrogen gas protection environment, intermediate 1, intermediate 2 and Bi particles were ball-milled and mixed at a ball-to-material ratio of 10:2 at a rotation speed of 200 r / min for 10 h to obtain a mixture, and the mixture was molded by a tablet press in a mold at a pressure of 400 MPa to obtain a green compact. In a nitrogen gas protection environment, the temperature was raised at a heating rate of 120 °C / min. When the temperature reached 500 °C, it was maintained at a pressure of 300 MPa for 60 min, then the pressure was increased to 4 GPa, and the temperature was further raised to 1300 °C. After holding for 10 min, it was quenched and depressurized to obtain the welding filler metal.

[0041] Comparative Example 4: A low-melting-point welding filler metal, comprising the following components by weight percentage: 9.0% of Zn and the balance of Sn. The specific preparation method comprises the following steps:

[0042] Weigh Sn particles with a purity of 99.99% and Zn particles with a purity of 99.9% according to a certain weight percentage and put them into a quartz tube. The vacuum degree in the quartz tube was reduced to 4×10-2 After reaching 1×10⁻² Pa, nitrogen gas was filled until the pressure reached 0.3 MPa, and then melting heat treatment was carried out at a temperature of 550 °C for 60 min in a nitrogen gas protection environment, followed by cooling to obtain the welding filler metal.

[0043] Comparative Example 5: A low-melting-point welding filler metal, comprising the following components by weight percentage: 9.0% Zn, 3.0% Mn, 2.6% Bi, 0.5% Hf, and the balance Sn. The specific preparation method includes the following steps:

[0044] Sn particles with a purity of 99.99%, Zn particles with a purity of 99.9%, Bi particles, Mn particles, and Hf particles were weighed according to a certain weight percentage and placed into a quartz tube. The vacuum degree inside the quartz tube was reduced to 4×10 -2 Pa, then nitrogen gas was filled until the pressure reached 0.3 MPa, and melting heat treatment was carried out at a temperature of 1500 °C for 2 h in a nitrogen gas protection environment, followed by cooling to obtain the welding filler metal.

[0045] Test Example: Under the same experimental conditions, the melting temperature, wetting angle, and self-corrosion potential of the welding filler metals prepared in Examples 1 to 4 and Comparative Examples 1 to 5 of the present invention were measured, and the results are shown in Table 1.

[0046]

[0047] As can be seen from Table 1, compared with the pure Sn-Zn filler metal of Comparative Example 4, the melting points of the welding filler metals prepared in Examples 1 to 4 of the present invention are further reduced, and the melting temperature range is similar to that of Sn-Pb filler metals, which can well adapt to the parameter setting and debugging of the current traditional soldering process. At the same time, the wetting angles of the welding filler metals prepared in Examples 1 to 4 of the present invention are lower than those of Comparative Examples 1 to 5, indicating the importance of the synergistic effect of Hf and Mn in improving the wettability of the welding filler metal. In addition, compared with Comparative Examples 1 to 5, the welding filler metals prepared in Examples 1 to 4 have a higher self-corrosion potential. In the corrosion principle of welding filler metals, the higher the self-corrosion potential, the more difficult it is for electron transfer to occur on its surface in a humid environment, and thus it is less likely to be oxidized or corroded. The preparation method of the welding filler metal provided by the present invention first reacts Zn, Mn, and Hf with Sn at high temperature to prepare intermediates 1, 2, and 3, and then performs high-pressure sintering on intermediates 1, 2, 3, and Bi particles to obtain the welding filler metal. Through the above steps, the structure of the prepared welding filler metal is more dense, further enhancing its corrosion resistance. In summary, the welding filler metal provided by the present invention has good wetting performance and corrosion resistance while maintaining the low melting point characteristic, showing excellent comprehensive performance.

[0048] The embodiments described above have elaborated in detail the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A method for preparing a low melting point solder, characterized in that: The preparation method comprises the following steps: Sn particles and Zn particles are subjected to a first smelting heat treatment in an inert gas protection environment and then cooled to obtain an intermediate 1, Sn particles and Mn particles are subjected to a second smelting heat treatment in an inert gas protection environment and then cooled to obtain an intermediate 2, Sn particles and Hf particles are subjected to a third smelting heat treatment in an inert gas protection environment and then cooled to obtain an intermediate 3, intermediate 1, intermediate 2, intermediate 3 and Bi particles are mixed by ball milling, and then sintered under high pressure and then quenched and depressurized to obtain the welding brazing material; The high pressure sintering temperature is 900-1200°C; The pressure of the high pressure sintering is 3~4GPa; The solder comprises the following components by weight percentage: 9.0% Zn, 2.5-3.5% Mn, 1.8-2.6% Bi, 0.01-0.5% Hf and the balance Sn.

2. The method for preparing a low melting point solder according to claim 1, characterized in that: The purity of the Zn particles is 99.9%.

3. The method for preparing a low melting point solder according to claim 1, characterized in that: The purity of the Sn particles is 99.99%.

4. The method for preparing a low melting point solder according to claim 1, characterized in that: The first smelting has a smelting temperature of 450-550° C. and a smelting time of 30-60 min.

5. The method for preparing a low melting point solder according to claim 1, characterized in that: The smelting temperature of the second smelting is 1300-1500° C., and the smelting time is 40-60 min.

6. The method for preparing a low melting point solder according to claim 1, characterized in that: The smelting temperature of the third smelting is 2300-2500° C., and the smelting time is 80-100 min.

7. A welding brazing filler metal prepared by the method for preparing a low melting point welding brazing filler metal as claimed in any one of claims 1 to 6.

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