Tin-copper series high-temperature anti-oxidation solder with low copper corrosion rate

Abstract

The invention discloses a tin-copper series high-temperature antioxidant solder with low copper corrosion rate, which comprises the following components in percentage by mass: 1.2-2.5% of Cu, 0.1-1.2% of Bi, 0.03-0.15% of alloy element X and the balance of Sn, X is one or more of Ni, Nd, As, P and Ga, and in the alloy element X, the content of Ni is 0.02-0.1%, the total content of Nd and As is 0.01-0.02%, and the total content of P and Ga is 0.005-0.025%. The solder has low copper corrosion rate, high oxidation resistance and high strength, and the copper corrosion rate at 360 DEG C is reduced by 26.4%-58.7% compared with SnCu 0.7; the liquid surface is kept bright for 40-70 seconds at the temperature of 400 DEG C, and the oxidizing slag rate is only 1%-2.5%; the Brinell hardness is improved by 4.8%-65.3% at the room temperature, the tensile strength is improved by 8.5%-59.4%, and the alloy is particularly suitable for dip soldering and wave soldering scenes with the high welding temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of microelectronic interconnect solders, and specifically relates to a tin-copper high-temperature anti-oxidation solder with a low copper dissolution rate, which is particularly suitable for dip soldering and wave soldering scenarios where the soldering temperature is relatively high. Background Art

[0002] In high-temperature dip soldering and wave soldering processes in electronic packaging and heat sink assembly, traditional Sn-0.7Cu eutectic solder has the following problems: 1) The copper substrate corrosion rate is too high at high temperatures, which leads to an increase in the number of intermetallic compounds (IMCs), resulting in poor solder fluidity, which seriously affects the welding effect. After the solder joint is formed, the IMC layer will be too thick, which will weaken the reliability of the solder joint; 2) The surface of molten solder is easily oxidized, generating a large amount of slag, which increases production costs and reduces welding quality; 3) The mechanical strength of the solder is insufficient to meet the requirements of high reliability applications.

[0003] Currently, while the addition of elements such as Ag, Sb, and In can improve some properties to a certain extent, the addition of a single or a few elements makes it difficult to simultaneously achieve low copper dissolution, high oxidation resistance, and high strength, and may even have negative effects. For example, the addition of Ag improves the strength and wettability of the solder, but this significantly increases the cost. The addition of Sb and In can, to a certain extent, strengthen the alloy by dissolving into the tin matrix, improving the strength and ductility of the alloy. However, excessive Sb may cause coarse SnSb intermetallic compounds to precipitate at grain boundaries, becoming a source of fracture. The addition of In significantly lowers the alloy's melting point. The addition of Ga or P can improve high-temperature oxidation resistance, but improperly controlling the addition of Ga and P may reduce the solder's fluidity.

[0004] To address the copper corrosion rate, existing techniques primarily increase the initial Cu content in the solder to reduce the concentration gradient between Cu atoms in the base material and within the solder, thereby inhibiting the diffusion of Cu atoms into the solder. However, excessive Cu content in the solder can exacerbate excessive IMC formation, reducing the solder's fluidity and wettability, ultimately impacting solder quality. Conventional methods also attempt to reduce the copper corrosion rate by optimizing soldering process parameters, such as lowering the soldering temperature, shortening the soldering time, and optimizing fixture design. However, these methods have limitations. For example, while lowering the soldering temperature can slow copper corrosion to a certain extent, it can increase the viscosity of the molten solder, reduce its fluidity, and decrease its wettability, thereby impacting soldering reliability. Optimizing fixture design, on the other hand, increases equipment complexity and production costs. While these process optimization measures can alleviate copper corrosion to a certain extent, their effectiveness is limited and often comes at the expense of other key process performance factors, making it difficult to simultaneously achieve both copper corrosion suppression and excellent solder quality. Summary of the Invention

[0005] The object of the present invention is to address the deficiencies of the above-mentioned prior art and provide a tin-copper high-temperature antioxidant solder that has a low copper dissolution rate, high oxidation resistance and high strength through the synergistic effects of concentration gradient suppression, IMC interface diffusion barrier and dissolution kinetic restriction, and is suitable for high-temperature dip soldering for high-end electronics. The solder effectively inhibits copper dissolution while avoiding the problem of excessive IMC growth caused by simply increasing the copper content, thereby providing the solder with excellent process performance.

[0006] The purpose of the present invention is achieved through the following technical solutions: A tin-copper high-temperature antioxidant solder with a low copper dissolution rate comprises, by mass percentage, 1.2-2.5% Cu, 0.1-1.2% Bi, 0.04-0.15% alloying element X, where X is one or more of Ni, Nd, As, P and Ga, and the balance is Sn.

[0007] Furthermore, in the alloy element X of the present invention, the Ni content is 0.02-0.1%, the total content of Nd and As is 0.01-0.02%, and the total content of P and Ga is 0.005-0.025%.

[0008] Furthermore, in the solder of the present invention, 1.42%≤(Cu+Ni)≤2.5%, and at a temperature of 360°C, the copper dissolution rate is reduced by 26.4% to 58.7% compared with SnCu0.7.

[0009] Furthermore, in the solder described in the present invention, 0.5≤(P+Ga) / (Nd+As)≤1.2, the liquid surface remains bright for 40-70s at a temperature of 400°C, and the jet oxidation slag rate is 1%-2.5%.

[0010] Furthermore, in the solder described in the present invention, 0.001≤(Nd+As)×Bi≤0.02, the Brinell hardness at room temperature is increased by 4.8% to 65.3% compared with SnCu0.7, and the tensile strength is increased by 8.5% to 59.4% compared with SnCu0.7.

[0011] Furthermore, the tin-copper high-temperature antioxidant solder with a low copper dissolution rate described in the present invention is characterized in that the purity of Sn, Bi and Ga are all 99.99%.

[0012] The method for preparing the explosive alloy of the present invention comprises the following steps: 1) Melt Sn, Bi, Ga with a purity of 99.99% and SnCu0.7, SnNi2, SnP4, SnNd3, SnAs5 master alloy according to the ratio; 2) Heat to 400℃, keep warm for 120 minutes, and cast into alloy ingots.

[0013] The present invention has the following advantages: 1) The solder of the present invention strictly controls the addition amounts of Cu, Bi, Ni, Nd, As, P, and Ga alloy elements, preferably adding 1.2-2.5% Cu. Furthermore, considering the optimization of Cu substrate corrosion and IMC layer, a slight addition of Ni is further preferred. This improves the problems of excessively rapid IMC growth in solder joints and excessively rapid Cu corrosion in substrates, and is beneficial for maintaining the stability of chemical composition, melting point, fluidity, and welding performance with solder.

[0014] 2) The present invention optimizes the total content of P and Ga elements to 0.005-0.025%, effectively improving the high-temperature oxidation resistance of the alloy, reducing the generation of oxidation slag, and improving the welding yield.

[0015] 3) The Bi content of the present invention is 0.1-1.2%, and the total content of Nd and As is 0.01-0.02%, which can introduce solid solution and precipitation strengthening. The composite strengthening can effectively improve the hardness and strength of the alloy matrix and enhance the reliability of the solder joint.

[0016] 4) The solder alloy of the present invention is prepared using an intermediate alloy preparation process. Compared with the preparation method of adding high-melting-point metal elements such as Cu, Nd, As, Ni, and P separately multiple times, the process of the present invention is simple, the metal utilization rate is high, the alloy composition is uniform, and the performance is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A comparison chart of copper corrosion rates of Examples 1 to 6 and Comparative Example 1; Figures 2 to 8 The liquid surface state diagrams of Examples 1 to 6 and Comparative Example 1 are shown in order; Figure 9 This is a comparison chart of the amount of oxidation slag in Examples 1 to 6 and Comparative Example 1; Figures 10 to 16 The tensile curves of Examples 1 to 6 and Comparative Example 1 are shown in sequence; Figure 17 1 is a comparison chart of tensile strength of Examples 1 to 6 and Comparative Example 1; Figure 18 The figure is a comparison chart of the Brinell hardness of Examples 1 to 6 and Comparative Example 1. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below through examples, but the protection scope of the present invention is not limited to the contents described in the examples.

[0019] The following Examples 1 to 6 provide a method for preparing a tin-copper high-temperature, antioxidant solder with a low copper dissolution rate, comprising: melting 99.99% pure Sn, Bi, and Ga metals and a master alloy of SnCu0.7, SnNi2, SnP4, SnNd3, and SnAs5 in a resistance furnace, heating the alloy to 400°C, holding the temperature for 120 minutes, and then casting the resulting alloy into a mold to form an alloy ingot.

[0020] The copper corrosion rate, oxidation resistance, Brinell hardness, and tensile test methods of the tin-copper high-temperature antioxidant solders with low copper corrosion rates of Examples 1 to 6 and the commercial solder of Comparative Example 1 are as follows: Weigh 650g of solder alloy and place it in a resistance furnace. Heat it to 360℃ until the alloy is completely melted. Then place sandpaper on the melt surface to polish the surface with an area of ​​50 cm. 2 The copper sheet was taken out after 1 hour of heat preservation, 150g of the melt was cast into a mold to make an alloy ingot, and the copper content before and after dissolution was tested by X-ray fluorescence spectrometer. The calculation is performed using the formula, where C1 and C2 are the copper concentrations before and after dissolution, M is the mass of the added solder alloy, A is the area of ​​the copper sheet, and T is the melting temperature.

[0021] 3000g of material was placed in a resistance furnace for melting and then subjected to a static oxidation test. After reaching the target temperature, the surface oxide slag was scraped off and the liquid level change time was recorded with a stopwatch.

[0022] The test was carried out using a jet tin furnace with a test material of 3000 g, a test temperature of 400°C, a test time of 30 min, and a frequency of 30 Hz. After the test, the slag was skimmed and weighed, and the slag rate was calculated.

[0023] The above alloy ingots were cut into tensile specimens with a length of 15 mm, a thickness of 1 mm, and a gauge length of 5 mm. After being sandpaper polished, cleaned, and dried, they were placed on a homemade high-throughput tensile equipment for room temperature uniaxial tensile testing at a tensile rate of 3 mm / min.

[0024] The above alloy ingots were polished with sandpaper of different mesh sizes to make the surface flat and smooth. The Brinell hardness of the alloy was tested on a Brinell hardness testing machine with an indenter diameter of 10 mm, a pressure of 125 kg, and a holding pressure of 30 s. At least three positions were tested. Example 1

[0025] A tin-copper high-temperature anti-oxidation solder with a low copper dissolution rate is disclosed. The solder alloy comprises, by mass percentage, 98.47% Sn, 1.4% Cu, 0.1% Bi, 0.02% Ni, 0.01% As, and 0.005% P.

[0026] The solder alloy is prepared as follows: According to the alloy ratio, 99.99% pure Sn metal, 99.99% Bi metal, 99.99% P metal and SnCu0.7, SnNi2, and SnAs5 master alloys are mixed and placed in a resistance melting furnace. The mixture is heated to 400°C, kept warm for 120 minutes, and then cast into a mold to form a SnCu1.4Bi0.1Ni0.02As0.01P0.005 alloy ingot. The copper dissolution rate tested by the above method is 152.75 mg / (min·cm 2 ),like Figure 1 As shown; Liquid surface state Figure 2 As shown in Figure 2, when the temperature is raised to 400°C and maintained for 60 seconds, the melt surface becomes dark and oxidation stripes appear. The oxidation slag rate after jet slagging is 2.21%, see Table 2. The tensile strength of the tensile test was 39.84 MPa as measured by the above test method. Figure 10 As shown; Brinell hardness is 11.78 ± 0.77 N / mm 2 ,like Figure 18 shown. Example 2

[0027] A tin-copper high-temperature anti-oxidation solder with a low copper dissolution rate is disclosed. The solder alloy comprises, by mass percentage, 98.15% Sn, 1.6% Cu, 0.2% Bi, 0.03% Ni, 0.012% As, and 0.007% Ga.

[0028] The preparation method of the solder is the same as that of Example 1. The copper dissolution rate measured by the above test method is 136.78 mg / (min·cm 2 ),like Figure 1 As shown; Liquid surface state Figure 3 As shown in Figure 2, the surface of the melt was slightly darkened and a few oxidation streaks appeared when the temperature was raised to 400°C and maintained for 60 seconds. The oxidation slag rate after jet slagging was 1.68%, see Table 2. The tensile test and Brinell hardness test of the solder alloy are the same as those in Example 1. Figure 11 As shown, the tensile strength of the alloy is measured to be 43.19 MPa; the Brinell hardness is 12.91 ± 0.24 N / mm 2 ,like Figure 18 shown. Example 3

[0029] A tin-copper high-temperature oxidation-resistant solder with a low copper dissolution rate is disclosed. The solder alloy comprises, by mass percentage, 97.43% Sn, 2.0% Cu, 0.5% Bi, 0.05% Ni, 0.01% Nd, and 0.008% P.

[0030] The preparation method of the solder is the same as that of Example 1. The copper dissolution rate tested by the above method is 124.43 mg / (min·cm 2 ),like Figure 1 As shown; The liquid surface state test method of the solder alloy is the same as that of Example 1. Figure 4 As shown in Table 2, the surface of the melt becomes dark and pale yellow, and basically loses its metallic luster. The oxidation slag rate after jet slagging is 2.35%, see Table 2. The tensile test and Brinell hardness test of the solder alloy are the same as those in Example 1. Figure 12 As shown, the tensile strength of the alloy is measured to be 46.28 MPa; the Brinell hardness is 13.81 ± 0.53 N / mm 2 ,like Figure 18 shown. Example 4

[0031] A tin-copper high-temperature oxidation-resistant solder with a low copper dissolution rate. The solder alloy comprises 96.9% Sn, 2.2% Cu, 0.8% Bi, 0.08% Ni, 0.015% As, and 0.01% Ga in weight percentage.

[0032] The preparation method of the solder is the same as that of Example 1. The copper dissolution rate measured by the above test method is 101.16 mg / (min·cm 2 ),like Figure 1 As shown; The liquid surface state test method of the solder alloy is the same as that of Example 1. Figure 5 As shown in Table 2, the melt surface remains basically bright, and the oxidation slag rate after jet slagging is 1.46%. The tensile test and Brinell hardness test of the solder alloy are the same as those in Example 1. Figure 13 As shown, the tensile strength of the alloy is measured to be 55.82 MPa; the Brinell hardness is 16.81 ± 0.54 N / mm 2 ,like Figure 18 shown. Example 5

[0033] A tin-copper high-temperature anti-oxidation solder with a low copper dissolution rate is disclosed. The solder alloy comprises 96.46% Sn, 2.4% Cu, 1.0% Bi, 0.1% Ni, 0.02% Nd, 0.012% P, and 0.013% Ga in weight percentage.

[0034] The preparation method of the solder is the same as that of Example 1. The copper dissolution rate measured by the above test method is 85.63 mg / (min·cm 2 ),like Figure 1 As shown; The liquid surface state test method of the solder alloy is the same as that of Example 1. Figure 6 As shown in Table 2, the melt surface is bright and the oxidation slag rate after jet slag removal is 1.03%; The tensile test and Brinell hardness test of the solder alloy are the same as those in Example 1. Figure 14 As shown, the tensile strength of the alloy is measured to be 58.51 MPa; the Brinell hardness is 18.58 ± 0.69 N / mm 2 ,like Figure 18 shown. Example 6

[0035] A tin-copper high-temperature oxidation-resistant solder with a low copper dissolution rate. The solder alloy comprises 96.27% Sn, 2.5% Cu, 1.2% Bi, 0.015% Nd, 0.01% P, and 0.005% Ga in weight percentage.

[0036] The preparation method of the solder alloy is the same as that of Example 1. The copper dissolution rate measured by the above test method is 94.68 mg / (min·cm 2 ),like Figure 1 As shown; The liquid surface state test method of the solder alloy is the same as that of Example 1. Figure 7 As shown, the melt surface is similar to that of Example 5, also a bright mirror surface, maintaining metallic luster; the oxidation slag rate after jet slagging is 1.25%, see Table 2; The tensile test and Brinell hardness test of the solder alloy are the same as those in Example 1. Figure 15 As shown, the tensile strength of the alloy is 57.45 MP; the Brinell hardness is 18.29 ± 0.47 N / mm 2 ,like Figure 18 shown. Comparative Example 1

[0037] A commercial binary tin-copper eutectic solder alloy, wherein the weight percentage composition of the solder alloy is 99.3% Sn and 0.7% Cu. The preparation method of the solder alloy is the same as that of Example 1.

[0038] The copper dissolution rate tested by the above method is 207.57 mg / (min·cm 2 ),like Figure 1 As shown, it is significantly higher than the solder alloys of Examples 1 to 6.

[0039] The liquid surface state test method of the solder alloy is the same as that of Example 1. Figure 8 As shown in Table 2, the liquid surface of the commercial alloy turned dark yellow as a whole, completely lost its metallic luster, and the oxidation slag rate was 3.52%. Its oxidation resistance was significantly lower than that of the solder alloys of Examples 1 to 6. The tensile test and Brinell hardness test of the commercial alloy are the same as those in Example 1. The tensile curve is as follows: Figure 16 As shown in the figure, the tensile strength of the commercial alloy is 38.85 MPa and the Brinell hardness is 11.24 ± 0.73 N / mm. 2 ,like Figure 17 and Figure 18 As shown, they are all lower than the solder alloys of Examples 1 to 6.

[0040] Table 1 Test results of copper dissolution rate of the solders of Examples 1 to 6 and the commercial tin-copper binary alloy of Comparative Example 1

[0041] As can be seen from Table 1, the copper dissolution rate of the tin-copper solder of the present invention is reduced by more than 25% compared with SnCu0.7.

[0042] Table 2 Test results of oxidation slag rate of solders of Examples 1 to 6 and commercial tin-copper binary alloy of Comparative Example 1

[0043] As shown in Tables 1 and 2, compared with the pure copper SnCu0.7 eutectic solder alloy, the solder of the present invention has a copper dissolution rate reduced by 26.4% to 58.7% at 360°C; at 400°C, the liquid surface remains bright for 40 to 70 seconds, and the oxidation slag rate is only 1% to 2.5%; the Brinell hardness at room temperature is increased by 4.8% to 65.3%, and the tensile strength is increased by 8.5% to 59.4%.

[0044] The above embodiments are only some of the embodiments of the present invention and are not exhaustive. Based on the optimized novel tin-copper alloy, the present invention adds two metal trace elements, Sb and Ag, with an Sb content of 0 to 0.5 wt.% and an Ag to Sb ratio of 1:2. All of these fall within the scope of protection of the present invention.

[0045] Unless otherwise specified, all percentages described in the present invention are by mass.

Claims

1. A tin-copper high-temperature anti-oxidation solder with a low copper dissolution rate, characterized in that: Calculated by mass percentage, it contains 1.2-2.5% Cu, 0.1-1.2% Bi, 0.03-0.15% alloy element X, where X is one or more of Ni, Nd, As, P and Ga, and the balance is Sn.

2. The tin-copper high-temperature anti-oxidation solder with low copper dissolution rate according to claim 1, characterized in that: In the alloy element X, the Ni content is 0.02-0.1%, the total content of Nd and As is 0.01-0.02%, and the total content of P and Ga is 0.005-0.025%.

3. The tin-copper high-temperature anti-oxidation solder with low copper dissolution rate according to claim 2, characterized in that: In the solder, 1.42%≤(Cu+Ni)≤2.5%.

4. The tin-copper high-temperature anti-oxidation solder with low copper dissolution rate according to claim 2, characterized in that: In the solder, 0.5≤(P+Ga) / (Nd+As)≤1.

2.

5. The tin-copper high-temperature anti-oxidation solder with low copper dissolution rate according to claim 2, characterized in that: In the solder, 0.001≤(Nd+As)×Bi≤0.

02.

6. The tin-copper high-temperature antioxidant solder with a low copper corrosion rate according to any one of claims 1 to 5, characterized in that: The purity of Sn, Bi and Ga is 99.99%.

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