Corrosion-resistant tin-based alloy solder and method of making same

Abstract

This invention discloses a corrosion-resistant tin-based alloy solder and its preparation method, belonging to the field of alloy solder technology. The tin-based alloy solder of this invention comprises, by mass percentage: Cu: 0.7%, Ni: 0.05-0.21%, Zn or Al, where Zn is 0.05-0.15%, Al is 0.02-0.1%, and the balance is Sn. This invention, through optimizing the alloy solder formulation and combining it with the preparation method, prepares a tin-based alloy solder containing intermetallic compounds such as strip-shaped Cu6Sn5, needle-shaped (Cu,Ni)6Sn5, needle-shaped Cu6(Sn,Zn)5, needle-shaped Cu6(Sn,Al)5, and sheet-shaped (Cu,Ni)6(Sn,Al)5, effectively improving the thermodynamic stability and corrosion resistance of the tin-based alloy solder.

Description

Technical Field

[0001] This invention belongs to the field of alloy solder technology, and relates to a corrosion-resistant tin-based alloy solder and its preparation method. Background Technology

[0002] Solder is an important industrial raw material for connecting electronic components in soldering circuits. It is a type of solder with a low melting point, mainly referring to solder made of tin-based alloys.

[0003] Sn-0.7Cu type lead-free solder is considered one of the important development directions of new solders in recent years due to its economic efficiency. The comprehensive performance of solder directly affects whether electronic products can maintain normal use for a long period of time. As one of the factors to consider in the comprehensive performance of solder, the corrosion resistance of solder is also a key factor in the reliability of electronic products. Therefore, improving the corrosion resistance of Sn-0.7Cu type lead-free solder, extending the service life of electronic products, and improving the reliability of electronic products are of great significance.

[0004] Therefore, it is necessary to provide a corrosion-resistant tin-based alloy solder and its preparation method to effectively improve the corrosion resistance of tin-based lead-free solder, thereby enabling electronic products to maintain high long-term reliability. Summary of the Invention

[0005] To overcome the problems in the prior art, this invention optimizes the alloy composition and combines it with the preparation method to prepare tin-based alloy solders containing intermetallic compounds such as strip-shaped Cu6Sn5, needle-shaped (Cu,Ni)6Sn5, needle-shaped Cu6(Sn,Zn)5, needle-shaped Cu6(Sn,Al)5, flake-shaped (Cu,Ni)6(Sn,Al)5, and flake-shaped (Cu,Ni)6(Sn,Zn)5, thereby effectively improving the corrosion resistance of tin-based alloy solders.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] One aspect of this invention is a corrosion-resistant tin-based alloy solder, wherein the tin-based alloy solder comprises, by mass percentage: Cu: 0.7%, Ni: 0.05-0.21%, Zn or Al, wherein Zn is 0.05-0.15%, Al is 0.02-0.1%, and the balance is Sn.

[0008] Preferably, the tin-based alloy solder contains intermetallic compounds, which include one or more of the following: strip-shaped Cu6Sn5, needle-shaped (Cu,Ni)6Sn5, needle-shaped Cu6(Sn,Zn)5, needle-shaped Cu6(Sn,Al)5, flake-shaped (Cu,Ni)6(Sn,Al)5, and flake-shaped (Cu,Ni)6(Sn,Zn)5.

[0009] In another aspect, the present invention provides a method for preparing the above-mentioned corrosion-resistant tin-based alloy solder, the method comprising the following steps:

[0010] (1) Weigh the alloy raw materials according to the mass percentage and vacuum melt the alloy raw materials to obtain the molten alloy;

[0011] (2) Cool the molten alloy obtained in step (1) to the holding temperature and hold it. During the holding process, the alloy is turned over.

[0012] (3) After the alloy in step (2) is kept warm, it is cooled in the furnace and then air cooled to obtain corrosion-resistant tin-based alloy solder.

[0013] Preferably, in step (1), the melting temperature is 800°C and the melting time is 20 min.

[0014] Preferably, in step (2), the heat preservation temperature is 350°C and the heat preservation time is 2 hours. During the heat preservation process, the alloy is flipped every 20 minutes.

[0015] Preferably, in step (3), the alloy after heat preservation is first cooled to 250°C in the furnace and then air-cooled.

[0016] The beneficial effects of this invention are:

[0017] 1. This invention optimizes the tin-based alloy solder formulation and preparation method to prepare tin-based alloy solders containing intermetallic compounds such as strip-shaped Cu6Sn5, needle-shaped (Cu,Ni)6Sn5, needle-shaped Cu6(Sn,Zn)5, needle-shaped Cu6(Sn,Al)5, flake-shaped (Cu,Ni)6(Sn,Al)5, and flake-shaped (Cu,Ni)6(Sn,Zn)5. This effectively enhances the chemical inertness of the alloy surface and improves the electron binding capacity, thereby making the alloy solder less prone to electrochemical interaction with the external environment and improving the corrosion resistance of the alloy solder.

[0018] 2. This invention can effectively suppress the phase transformation of Cu6Sn5, thereby alleviating the problem of deteriorated corrosion performance caused by stress concentration at the phase interface and increased strain energy at the phase interface due to the phase transformation.

[0019] 3. The addition of metal elements in this invention has a low cost, which helps to reduce the overall cost of tin-based alloy solder. This allows for improved corrosion resistance of tin-based alloy solder at a lower cost, which is beneficial for the industrial application of this invention. Attached Figure Description

[0020] Figure 1 SEM image of the corrosion-resistant tin-based alloy solder prepared in Example 1.

[0021] Figure 2SEM image of the corrosion-resistant tin-based alloy solder prepared in Example 2.

[0022] Figure 3 The image shows a SEM image of the corrosion-resistant tin-based alloy solder prepared in Example 3.

[0023] Figure 4 The image shows a SEM image of the corrosion-resistant tin-based alloy solder prepared in Example 4.

[0024] Figure 5 Comparison of the corrosion microstructure of the corrosion-resistant tin-based alloy solders prepared in Examples 1-4 and Comparative Example 1. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments.

[0026] In the embodiments and comparative examples of this invention, all chemical reagents not specifically mentioned were commercially available analytical grade reagents used in the experiments.

[0027] In the embodiments and comparative examples of this invention, the composition of the tin-based solder is shown in Table 1.

[0028] Table 1

[0029]

[0030] Example 1

[0031] This embodiment prepares tin-based solder according to the following method:

[0032] (1) Weigh the required Sn, Cu, Ni and Zn alloy raw materials according to the composition in Table 1, and put the weighed raw materials into a glass tube for vacuum sealing, maintaining a vacuum degree of 10 in the glass tube. -4 Pa, the sealed glass tube is placed in a muffle furnace for melting at a temperature of 800℃, and held for 20 minutes to ensure that the alloy is completely melted.

[0033] (2) Then set the furnace temperature to 350°C, cool the molten alloy to 350°C, and keep it at that temperature for 2 hours. During the holding period, the glass tube is turned over every 20 minutes.

[0034] (3) After cooling and heat preservation, turn off the muffle furnace heating and let the alloy cool down to 250°C with the furnace. Then take out the alloy and air cool it to room temperature to obtain corrosion-resistant tin-based alloy solder.

[0035] Scanning electron microscopy (SEM) experiments were performed on the tin-based alloy solder prepared in this embodiment, and the results are as follows: Figure 1 As shown, through Figure 1It can be seen that the tin-based alloy solder prepared in this embodiment mainly contains lamellar (Cu,Ni)6(Sn,Zn)5 solid solution and Sn matrix. The heat of formation of IMCs (intermetallic compounds), corrosion potential, and corrosion current density of the tin-based alloy solder were tested, and the results are shown in Table 2. Microscopic morphology scanning experiments were performed on the tin-based alloy of this embodiment after corrosion, and the results are as follows: Figure 5 As shown.

[0036] Example 2

[0037] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0038] Scanning electron microscopy (SEM) experiments were performed on the tin-based alloy solder prepared in this embodiment, and the results are as follows: Figure 2 As shown, through Figure 2 It can be seen that the tin-based alloy solder prepared in this embodiment mainly contains needle-like (Cu,Ni)6Sn5, Cu6(Sn,Zn)5, plate-like (Cu,Ni)6(Sn,Zn)5 solid solutions, and a Sn matrix. The heat of formation of IMCs, corrosion potential, and corrosion current density of the tin-based alloy solder were tested, and the results are shown in Table 2. Microscopic morphology scanning experiments were performed on the tin-based alloy of this embodiment after corrosion, and the results are as follows: Figure 5 As shown.

[0039] Example 3

[0040] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0041] Scanning electron microscopy (SEM) experiments were performed on the tin-based alloy solder prepared in this embodiment, and the results are as follows: Figure 3 As shown, through Figure 3 It can be seen that the tin-based alloy solder prepared in this embodiment mainly contains needle-like (Cu,Ni)6Sn5, Cu6(Sn,Al)5, plate-like (Cu,Ni)6(Sn,Al)5 solid solutions, and a Sn matrix. The heat of formation of IMCs, corrosion potential, and corrosion current density of the tin-based alloy solder were tested, and the results are shown in Table 2. Microscopic morphology scanning experiments were performed on the tin-based alloy of this embodiment after corrosion, and the results are as follows: Figure 5 As shown.

[0042] Example 4

[0043] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0044] Scanning electron microscopy (SEM) experiments were performed on the tin-based alloy solder prepared in this embodiment, and the results are as follows: Figure 4 As shown, through Figure 4It can be seen that the tin-based alloy solder prepared in this embodiment mainly contains strip-shaped Cu6Sn5, needle-shaped (Cu,Ni)6Sn5, Cu6(Sn,Al)5, plate-shaped (Cu,Ni)6(Sn,Al)5 solid solutions, and a Sn matrix. The heat of formation of IMCs, corrosion potential, and corrosion current density of the tin-based alloy solder were tested, and the results are shown in Table 2. Microscopic morphology scanning experiments were performed on the tin-based alloy of this embodiment after corrosion, and the results are as follows: Figure 5 As shown.

[0045] Example 5

[0046] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0047] The microstructure of the tin-based alloy solder prepared in this embodiment is similar to that of the tin-based alloy solder in Example 2, and its properties are shown in Table 2.

[0048] Example 6

[0049] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0050] The microstructure of the tin-based alloy solder prepared in this embodiment is similar to that of the tin-based alloy solder in Example 3, and its properties are shown in Table 2.

[0051] Example 7

[0052] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0053] The microstructure of the tin-based alloy solder prepared in this embodiment is similar to that of the tin-based alloy solder in Example 4, and its properties are shown in Table 2.

[0054] Comparative Example 1

[0055] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0056] The tin-based alloy solder prepared in this embodiment mainly comprises strip-shaped Cu6Sn5 and a Sn matrix. The heat of formation of IMCs, corrosion potential, and corrosion current density of the tin-based alloy solder were tested, and the results are shown in Table 2. Microscopic morphology scanning experiments were performed on the tin-based alloy of this embodiment after corrosion, and the results are as follows: Figure 5 As shown.

[0057] Comparative Example 2

[0058] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0059] The tin-based alloy solder prepared in this embodiment mainly contains acicular (Cu,Ni)6Sn5 and a Sn matrix. The heat of formation of IMCs, corrosion potential, and corrosion current density of the tin-based alloy solder were tested, and the results are shown in Table 2.

[0060] Comparative Example 3

[0061] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0062] The tin-based alloy solder prepared in this embodiment mainly comprises strip-shaped Cu6Sn5, needle-shaped Cu6(Sn,Al)5, and a Sn matrix. The heat of formation of IMCs, corrosion potential, and corrosion current density of the tin-based alloy solder were tested, and the results are shown in Table 2.

[0063] Comparative Example 4

[0064] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0065] The tin-based alloy solder prepared in this embodiment mainly comprises strip-shaped Cu6Sn5, needle-shaped Cu6(Sn,Zn)5, and a Sn matrix. The heat of formation of IMCs, corrosion potential, and corrosion current density of the tin-based alloy solder were tested, and the results are shown in Table 2.

[0066] Comparative Example 5

[0067] In this embodiment, the tin-based alloy solder was prepared using the same method as in Example 1, and its composition is shown in Table 1.

[0068] Table 2

[0069]

[0070] As can be seen from the results in Table 2, the heat of formation of IMCs in the tin-based alloy solder prepared in the embodiments of the present invention is smaller than that in the tin-based alloy solder prepared in the comparative example, indicating that the tin-based alloy solder prepared in the present invention has high thermodynamic stability.

[0071] As can be seen from the results in Table 2, the tin-based alloy solder prepared in the embodiments of the present invention has a high corrosion potential and a low corrosion current density, indicating that the tin-based alloy solder of the present invention has a low corrosion rate and good corrosion resistance.

[0072] The results in Table 2 also show that when only one of Ni, Zn, or Al was added to Comparative Examples 2-4, although the thermodynamic stability and corrosion resistance were improved to some extent compared to Comparative Example 1, the improvement effect was limited and could not achieve the performance of the tin-based alloy solder of the present invention. This indicates that the chemical inertness of the alloy solder surface is enhanced under the synergistic influence of the bimetallic elements, and the corrosion resistance is improved more significantly. The intermetallic compounds (Cu,Ni)6(Sn,Zn)5 and (Cu,Ni)6(Sn,Al)5 play a more significant role in improving the thermodynamic stability and corrosion resistance of the tin-based alloy solder.

[0073] As can be seen from the results in Table 2, the performance of the tin-based alloy solder in Comparative Example 5 is significantly lower than that of the tin-based alloy solder in the embodiments of the present invention. The performance of the tin-based alloy solder in Comparative Example 5 is close to that in Comparative Example 1, indicating that Zn and Al cannot be added at the same time. Since both Zn and Al are easily corroded elements, when two elements are present in the alloy at the same time, on the one hand, the elements are prone to combine to form new compounds, reducing the content of alloy elements that can be dissolved in IMCs and weakening the modification of the chemical properties of IMCs; on the other hand, the addition of multiple easily corroded elements will inevitably lead to an increase in the chemical activity of the alloy surface, making it more susceptible to external corrosion.

[0074] pass Figure 5 It can be seen that the tin-based alloy solder in Comparative Example 1 is significantly more corroded than the tin-based alloy solder in the embodiment of the present invention, proving that the tin-based alloy solder prepared by the present invention does indeed have high corrosion resistance in actual corrosion processes.

[0075] In summary, the tin-based alloy solder prepared by this invention has excellent thermodynamic stability and corrosion resistance. Using it for soldering electronic components helps to improve the long-term reliability of electronic products.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a corrosion-resistant tin-based alloy solder, wherein the corrosion-resistant tin-based alloy solder comprises, by weight percentage: Cu: 0.7%, Ni: 0.05-0.21%, one of Zn or Al, Zn being 0.05-0.15%, Al being 0.02-0.1%, and the balance being Sn; The tin-based alloy solder contains intermetallic compounds, which include one or more of the following: acicular Cu6(Sn,Zn)5, acicular Cu6(Sn,Al)5, plate-like (Cu,Ni)6(Sn,Al)5, and plate-like (Cu,Ni)6(Sn,Zn)5. The preparation method comprises the following steps: (1) Weigh the alloy raw materials according to the mass percentage and vacuum melt the alloy raw materials to obtain the molten alloy; (2) Cool the molten alloy obtained in step (1) to the holding temperature and hold it there. During the holding process, the alloy... Flip it; (3) After the heat preservation in step (2) is completed, the alloy is cooled in the furnace and then air-cooled to obtain a corrosion-resistant tin-based alloy. Gold solder; In step (1), the melting temperature is 800℃ and the melting time is 20min; In step (2), the heat preservation temperature is 350℃ and the heat preservation time is 2h. During the heat preservation process, the alloy is flipped every 20min. In step (3), the alloy after heat preservation is first cooled to 250°C in the furnace and then air-cooled.

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