A high-speed shear-resistant multi-component snin soldering material obtained by regulating the tissue and its application

Abstract

The application discloses a kind of regulation tissue obtains high-speed shearing multivariate SnIn system solder and its application, the solder includes 0.05-0.4 wt.% of Cu, 2.82-2.96 wt.% of Ag, 4-18% of In, the balance is Sn, wherein the total content of Ag and Cu is 2.87 wt.%~3.36 wt.%, and (Ag+Cu) with In mass ratio is 1:1.19~1:6.27, In and Sn mass ratio is 1:4.37~1:23.28, the melting point of solder is 195-215 ℃.The application solder is low-speed shearing, and the fracture displacement and energy of solder joint are lower than SAC305 solder, but the fracture displacement is higher than SAC305 and its low-speed sample under high-speed shearing, and the fracture energy is more than twice the fracture energy of SAC305 under the same condition, in the case where the melting point is reduced simultaneously, the interface Cu6 (Sn, In) 5 of regulation solder joint matrix organization obtains gamma InSn4 phase and has lower hardness value high In content, so as to realize better strain coordination, so as to improve the toughness of solder joint under high-speed load.

Description

Technical Field

[0001] This invention belongs to the field of solder technology for microelectronic interconnect packaging, specifically relating to a multi-element SnIn solder alloy with excellent shear energy under high-speed shearing in the melting peak temperature range of 195-215 ℃ and its application. Background Technology

[0002] In semiconductor device manufacturing, the thermal warpage caused by large-size packaging necessitates lower soldering temperatures. The first-level interconnects of semiconductor devices, using lead-free high-temperature solder alloys such as SAC (tin-silver-copper), Sn0.7Cu, or Sn1.0Cu with surface mount technology (SMT) reflow peaks, require temperatures of 217°C or higher. Due to overheating during high-temperature reflow soldering, significant warpage occurs in semiconductor devices and chips. Warpage caused by high-temperature reflow processes leads to various surface mount defects, such as non-wetting voids (NWO), pillow effect (HoP), and bridging. In high-performance computing devices, the warpage problem of large BGA packages has become a major technical challenge from design to mass production. To reduce warpage and improve component reliability, low-temperature soldering technology has been proposed as a solution.

[0003] The addition of Bi and In elements can effectively lower the temperature. However, the addition of Bi brings many problems. The intrinsic brittleness of Bi causes a significant reduction in plasticity even with a small amount. To lower the temperature, more Bi is added, but Bi tends to accumulate into large brittle regions, causing brittle fracture at the interface. Bi itself is also prone to diffusion, and under the influence of electrical and thermal effects during later service, Bi can also accumulate and form large brittle regions. In addition, when Bi is added at more than 10 wt.%, it has two melting peaks, one high-temperature peak, and a low-temperature eutectic peak of 138 ℃ for Sn58Bi, while SnIn solder in the same temperature range has only one high-temperature peak and has good toughness (see Comparison of high-speed shear properties of low-temperature SnBi and SnIn solder / Cu solder joints). US Patent 10076808B2 discloses a SnInAgCu quaternary alloy with 1.0-13.0 wt.% In added, where Ag is 0.1-4.0 wt.% and Cu is 0.3-1.0 wt.%. The addition of In improves its electromigration performance at high current densities. Chinese Patent CN103501959B also discloses a Sn-Ag-Bi-In solder joint alloy composed of 2-4 wt.% Ag, 2-4 wt.% Bi, 2-5 wt.% In, and the balance Sn, which is effective even at current densities of 5-100 kA / cm². 2Even under long-term use at current densities within a certain range, electromigration is virtually nonexistent. Therefore, the addition of In improves electromigration performance, offering a greater advantage than lowering the melting point by adding Bi. In conclusion, using low-temperature SnIn solder provides superior toughness and long-term reliability.

[0004] Currently, there are few published documents on obtaining low-temperature high-toughness solders by adding In. The main focus is on improving thermal fatigue performance through solid solution strengthening by adding solid solution elements such as In, Bi, and / or Sb. For example, Chinese patent CN101801589B discloses a lead-free solder for automotive electronic circuits containing solid solution elements such as In (3–5.5 wt.%), Bi (0.5–3 wt.%), and Ag (2.8–4.0 wt.%) and Cu (0.5–1.1 wt.%). Chinese patent CN107635716B also discloses a SnAgCuSb-based lead-free solder for harsh environment electronics, which contains the following elements: 0.1–2.5 wt.% Bi and / or 0.1–4.5 wt.% In, 2.55–4.5 wt.% Ag, 0.6–2.0 wt.% Cu, and 2.5–9.0 wt.% Sb. Chinese patent CN105377503B discloses an addition of 6.2-9.0 wt.% In, with Bi content between 0.7% and 5.0% by mass, and Sb content between 0.3% and 5.0% by mass. Chinese patent CN113677477B discloses an alloy containing 13-22 wt.% In, 0.5-2.8 wt.% Ag, 0.5-5.0% Bi, 0.002-0.05% Ni, with the balance being Sn. Furthermore, Chinese patent CN113996967B discloses an alloy containing 10-18 wt.% In, with other elements being Bi: 0.6-1.5 wt.%, Ag: 0.2-0.8 wt.%, and the remainder Sn. This patent's alloy composition increases the solderability of the alloy solder and results in a very low void ratio in the weld, but this patent lacks melting point and reliable performance data. US Patent US9741676B1 discloses an alloy with an In content of 5.0-20.0 wt.%, an Ag content of 1.0-5.0 wt.%, 0.25-2.0 wt.% Cu, 0.1-0.5 wt.% zinc (Zn), and the remainder tin (Sn), which has low yield strength and low melting point.

[0005] During the addition of In, Sn and In form a multiphase structure. The applicant's previous research, "CALPHAD-guided alloy design of Sn–In based solder joints with multiphase structure and their mechanical properties," established structure-property relationships for different phases and bulk alloys of SnIn (x=0, 8, 18, 35, 42, and 52In) under low-velocity shear, showing that different phases exhibit different mechanical properties. Furthermore, considering the need for elemental control during welding and service, Zn is easily oxidized and is not a beneficial element in practical applications. Bi damage to plasticity is not considered, and excessive Ag addition will form coarse compounds that affect plasticity; therefore, the Ag proportion needs to be controlled to no more than 3 wt.%, while Cu can be added in small amounts. The goal is to significantly reduce the melting point without adding Bi, but this reduction must avoid the low-temperature peak of Sn20In2.8Ag. Furthermore, Ag and Cu mainly form compounds with Sn and In, and the size of these compounds needs to be controlled. Therefore, controlling the different phases and compounds in the matrix is ​​the key to obtaining solders with excellent shear energy under high-speed shear. Summary of the Invention

[0006] This invention aims to provide a bismuth-free and lead-free SnIn-based solder with a melting temperature range of 195-210 °C and excellent shear energy under high-speed shearing. This invention also provides application scenarios for this solder.

[0007] The technical solution adopted in this invention is as follows: A high-speed shear-resistant SnIn-based solder obtained by regulating its structure, the solder comprising 0.05-0.4 wt.% Cu, 2.82-2.96 wt.% Ag, 4-18% In, with the balance being Sn, wherein the total content of Ag and Cu is 2.87 wt.% ~ 3.36 wt.%, and the mass ratio of (Ag+Cu) to In is 1:1.19 to 1:6.27, the mass ratio of In to Sn is 1:4.37 to 1:23.28, and the melting point of the solder is 195-215 °C.

[0008] Preferably, the solder comprises 0.05-0.2 wt.% Cu, 2.82-2.88 wt.% Ag, 12-18% In, with the balance being Sn, and the mass ratio of (Ag+Cu) to In is 1:3.89~1:6.29, and the mass ratio of In to Sn is 1:4.39~1:7.09; the melting point of the solder is 196.7 ℃-204.0 ℃.

[0009] The application of the multi-element SnIn-based solder described in this invention involves using the solder on a substrate containing the γInSn4 phase at the solder joint, forming a Cu6(Sn, In)5 interface after soldering, wherein the atomic ratio of In in Cu6(Sn, In)5 is 5.6-7.4%.

[0010] The solder of the present invention contains a low-temperature SnIn alloy with excellent high-speed shear energy, and introduces the γInSn4 phase with excellent shear energy under high-speed shear. When the pad is a Cu substrate, an interface Cu6(SnIn)5 compound with softer interface and higher In content is formed.

[0011] The solder of this invention avoids the introduction of brittle or easily oxidized elements such as Bi and Zn, as well as the introduction of high-melting-point alloy Sb. The Ag content is limited to 2.82-2.96 wt.%, which avoids the formation of large Ag3Sn compounds and subsequent thermal fatigue performance. The Cu content is limited to 0.05-0.4 wt.%, which reduces the impact of different pads and the etching of Cu pads. The In content is limited to 4-18%, which lowers the melting point and avoids the appearance of the SnIn low-temperature peak. To achieve a matrix γInSn4 phase with excellent shear energy under high-speed shearing and a small amount of compounds that do not affect the matrix, the preferred Ag content is 2.82-2.88 wt.%, the Cu content is 0.05-0.2 wt.%, and the In content is 12-18 wt.%.

[0012] Compared with the prior art, the present invention has the following significant advantages: Under low-speed shear, the fracture displacement and energy of the solder joint of the present invention are lower than those of SAC305 solder, but under high-speed shear, the fracture displacement is higher than that of SAC305 and its low-speed sample. The fracture energy is in the range of 7.7-8.95 mJ, which is more than twice that of SAC305 under the same conditions. While reducing the melting point, the matrix structure of the solder joint is controlled to obtain γInSn4 phase and interface Cu6(Sn, In)5 with high In content and lower hardness value, thereby achieving better strain coordination and improving the toughness of the solder joint under high-speed load. Attached Figure Description

[0013] Figure 1 A comparison of the DSC heating curves of the five alloys in Examples 1-5 and the one alloy in Comparative Example 1. Figure 2 The image shows the internal microstructure of the weld joints of the alloy in Example 1 and the energy spectrum of the corresponding elements. Figure 3 The image shows the internal microstructure of the weld joints of the alloy in Example 2 and the energy spectrum of the corresponding elements. Figure 4 The image shows the internal microstructure of the weld joints of the alloy in Example 3 and the energy spectrum of the corresponding elements. Figure 5 The image shows the internal microstructure of the weld joints of the alloy in Example 4 and the energy spectrum of the corresponding elements. Figure 6 The image shows the internal microstructure of the weld joints of the alloy in Example 5 and the energy spectrum of the corresponding elements. Figure 7 The microstructure of the weld joints of alloy Comparative Example 1 and the energy spectrum of the corresponding elements are shown. Figure 8 A comparison of the interface morphology and composition of Examples 1-5 and Comparative Example 1; Figure 9 This is a comparison of the low-speed shear strength data of Examples 1-5 and Comparative Example 1; Figure 10 This is a comparison of low-speed shear displacement between Examples 1-5 and Comparative Example 1; Figure 11 Comparison of low-speed shear energy between Examples 1-5 and Comparative Example 1 Figure 12 Comparison of high-speed shear strength data between Examples 1-5 and Comparative Example 1; Figure 13 A comparison of high-speed shear displacement between Examples 1-5 and Comparative Example 1; Figure 14 This is a comparison of the high-speed shear energy of Examples 1-5 and Comparative Example 1. Detailed Implementation

[0014] The present invention will be further described in detail below through embodiments, but the scope of protection of the present invention is not limited to the contents described in the embodiments. Example 1

[0015] A high-speed shear-resistant SnIn-based solder with controlled microstructure is disclosed. The solder comprises 2.96% Ag, 0.40% Cu, 4% In, and the remainder Sn by weight percentage. The mass ratio of (Ag+Cu) to In is 1:1.19, and the mass ratio of In to Sn is 1:23.16. 。 The peak melting temperature of this lead-free solder is 215.0 ℃. Figure 1 As shown. Its microstructure is as follows. Figure 2 As shown, spot scan results confirm the presence of a matrix composition containing approximately 2 wt.% In of β-Sn, as well as a continuous, fine network of Ag3(SnIn) compounds and a small amount of fine Cu6(SnIn)5 compounds. Figure 8 As shown, its interfacial compound is a typical scalloped Cu6(SnIn)5, with an In content of approximately 1.0 atm % (this refers to the In content within the intermetallic compound, not the overall In content, the same applies below). The mechanical properties of the solder joints corresponding to this composition are shown in [reference needed]. Figures 9-11Under low-speed shearing, the shear strength is approximately 66 MPa, the displacement is 480 mm, and the energy is approximately 7.3 mJ. Under high-speed conditions, the shear strength is approximately 117 MPa, the displacement is 229 mm, and the energy is approximately 3.5 mJ. Figures 12-14 As shown, this indicates that as the shear rate increases, the strength increases by nearly 2 times, but the displacement decreases by less than half. This suggests that the shear mode has shifted from a mixed fracture mode that is biased towards ductility to an interfacial fracture mode that is biased towards brittleness, resulting in an energy reduction of about half. Example 2

[0016] A high-speed shear-resistant SnIn-based solder with controlled microstructure is disclosed. The solder comprises 2.92% Ag, 0.30% Cu, 8% In, and the remainder Sn by weight percentage. The mass ratio of (Ag+Cu) to In is 1:2.48, and the mass ratio of In to Sn is 1:11.10. This lead-free solder has a melting peak temperature of 209.3 °C. Figure 3 As shown. Its microstructure is as follows. Figure 2 As shown, the spot scan results confirm that the matrix consists of approximately 5.7 wt.% In β Sn, as well as continuously dispersed Ag3 (SnIn) compounds and a small amount of fine Cu6 (SnIn)5 compounds. Figure 8 As shown, its interface compound is a typical scalloped Cu6(SnIn)5, with an In content of approximately 2.5 atm%. The mechanical properties of the solder joints corresponding to this composition are shown below. Figures 9-11 Under low-speed shearing, the shear strength is approximately 75 MPa, the displacement is 382 mm, and the energy is approximately 6.1 mJ. Under high-speed conditions, the shear strength is approximately 109 MPa, the displacement is 181 mm, and the energy is approximately 2.8 mJ. Figures 12-14 As shown, this indicates that as the shear rate increases, the strength increases by nearly 1.5 times, but the displacement decreases by less than half. This suggests that the shear mode changes from a mixed fracture mode that is biased towards brittleness to an interfacial fracture mode that is biased towards brittleness, resulting in the energy decreasing by less than half. Example 3

[0017] A high-speed shear-resistant SnIn-based solder with controlled microstructure is disclosed. The solder comprises 2.88% Ag, 0.20% Cu, 12% In (by weight percentage), with the remainder being Sn. The mass ratio of (Ag+Cu) to In is 1:3.90, and the mass ratio of In to Sn is 1:7.08. This lead-free solder has a melting peak temperature of 204.0 °C. Figure 1 As shown. Its microstructure is as follows. Figure 4As shown, the spot scan results prove that the matrix consists of β Sn containing about 6.74 wt.% In and γInSn4 phase containing 12.95% In, as well as continuously dispersed Ag3 (SnIn) compounds and a small amount of fine Cu6 (SnIn)5 compounds. Figure 8 As shown, its interface compound is a typical scalloped Cu6(SnIn)5, with an In content of approximately 5.6 atm%. The mechanical properties of the solder joints corresponding to this composition are shown below. Figures 9-11 Under low-speed shearing, the shear strength is approximately 71 MPa, the displacement is 360 mm, and the energy is approximately 4.8 mJ. Under high-speed conditions, the shear strength is approximately 95 MPa, the displacement is 501 mm, and the energy is approximately 8.95 mJ. Figures 12-14 As shown, this indicates that with the increase in shear rate, the strength increases by nearly 1.3 times, and the displacement also increases by nearly 1.4 times. This suggests that the shear mode has shifted from a mixed fracture mode that is more brittle to a mixed fracture mode that is more ductile, resulting in an energy increase of nearly 1.86 times. Example 4

[0018] A high-speed shear-resistant SnIn-based solder with controlled microstructure is disclosed. The solder comprises 2.85% Ag, 0.1125% Cu, 15% In (by weight percentage), with the remainder being Sn. The mass ratio of (Ag+Cu) to In is 1:5.06, and the mass ratio of In to Sn is 1:5.47. This lead-free solder has a melting peak temperature of 197.6 °C. Figure 1 As shown. Its microstructure is as follows. Figure 5 As shown, the spot scan results prove that the matrix consists of approximately 13 wt.% In β Sn and 15 wt.% In γInSn4 phase, as well as continuously dispersed Ag3 (SnIn) compounds and a small amount of fine Cu6 (SnIn)5 compounds. Figure 8 As shown, its interface compound is a typical scalloped Cu6(SnIn)5, with an In content of approximately 6.3 atm%. The mechanical properties of the solder joints corresponding to this composition are shown below. Figures 9-11 Under low-speed shearing, the shear strength is approximately 65 MPa, the displacement is 355 mm, and the energy is approximately 4.3 mJ. Under high-speed conditions, the shear strength is approximately 74 MPa, the displacement is 513 mm, and the energy is approximately 7.8 mJ. Figures 12-14 As shown, this indicates that with the increase in shear rate, the strength increases by nearly 1.1 times, and the displacement also increases by nearly 1.4 times, indicating that the shear mode shifts from a brittle mixed fracture mode to a ductile mixed fracture mode, thereby increasing the energy by nearly 1.81 times. Example 5

[0019] A high-speed shear-resistant SnIn-based solder with controlled microstructure is disclosed. The solder comprises 2.82% Ag, 0.05% Cu, 18% In (by weight percentage), with the remainder being Sn. The mass ratio of (Ag+Cu) to In is 1:6.27, and the mass ratio of In to Sn is 1:4.40. This lead-free solder has a melting peak temperature of 196.7 °C. Figure 1 As shown. Its microstructure is as follows. Figure 6 As shown, the spot scan results prove that the main components are γInSn4 phase containing 18 wt.% In, as well as continuously dispersed Ag3(SnIn) compounds, a small amount of fine Cu6(SnIn)5 compounds, and a small amount of needle-like Cu6(SnIn)5 compounds. Figure 8 As shown, its interface compound is a typical scalloped Cu6(SnIn)5, with an In content of approximately 7.4 atm%. The mechanical properties of the solder joints corresponding to this composition are shown below. Figures 9-11 Under low-speed shearing, the shear strength is approximately 58 MPa, the displacement is 352 mm, and the energy is approximately 3.9 mJ. Under high-speed conditions, the shear strength is approximately 85 MPa, the displacement is 453 mm, and the energy is approximately 7.7 mJ. Figures 12-14 As shown, this indicates that with the increase in shear rate, the strength increases by nearly 1.47 times, and the displacement also increases by nearly 1.3 times, indicating that the shear mode shifts from a brittle mixed fracture mode to a ductile mixed fracture mode, thereby increasing the energy by nearly 1.97 times. Comparative Example 1

[0020] The composition is a typical commercially available Sn96.5-Ag3.0-Cu0.5 alloy. This lead-free solder has a peak melting temperature of 222.9℃. Figure 1 As shown. Its microstructure is as follows. Figure 7 As shown, the compound consists of a β-Sn matrix and a continuous, fine network of Ag3Sn and Cu6Sn5. Figure 8 The interface compound shown is a typical Cu6Sn5 compound. (See...) Figures 9-11 Under low-speed shearing, the shear strength is approximately 56 MPa, the displacement is 623 mm, and the energy is approximately 7.8 mJ. Under high-speed conditions, the shear strength is approximately 106 MPa, the displacement is 256 mm, and the energy is approximately 3.1 mJ. Figures 12-14 As shown, this indicates that as the shear rate increases, the strength increases by nearly 2 times, but the displacement decreases by less than half. This suggests that the shear mode has shifted from a mixed fracture mode that is biased towards ductility to an interfacial fracture mode that is biased towards brittleness, resulting in an energy reduction of less than half.

[0021] The solder alloys prepared in the examples and comparative examples were characterized and tested with high precision, as shown in Table 1.

[0022] Table 1. Composition and melting peak values ​​of the examples and comparative examples

[0023] The addition of In content led to changes in melting point and microstructure. (See Table 1 and...) Figure 1 It is known that simply increasing the In content can lower the melting point. When the In content increases from 4% to 18%, the peak melting point decreases by 7.9 °C to 26.2 °C compared to SAC305. Figures 2-7 It is known that the addition of In content leads to changes in the microstructure of the solder joint. Initially, the SAC305 consists of a network of Ag3Sn and Cu6Sn5 compounds and embedded In-free β-Sn. As the In content increases to 4% and 8%, the In-free β-Sn gradually transforms into β-Sn containing 2% and 5.7% In, respectively. When the content reaches 12% In, γInSn4 appears, resulting in a two-phase microstructure of β-Sn and γInSn4 with different In contents. With the addition amount increasing to 18% In, the matrix consists only of a single γInSn4 phase. Simultaneously, the composition of Ag and Cu changes relatively little. In the Ag3Sn and Cu6Sn5 compounds, Sn atoms are replaced by In, and the overall morphology remains fine and dispersed. However, these compounds gradually change from a continuous network structure to a discontinuous, dispersed structure. Similarly, Figure 8 It was shown that the In compound had little effect on the size and morphology of the Cu6Sn5 compound after reflux, while the spot scan results showed that In mainly affected the atomic percentage of In in Cu6(SnIn)5. The higher the In content in the matrix, the higher the In percentage, from 1.0 atom% in 4In to 7.4 atom% in 18In.

[0024] Changes in microstructure lead to changes in properties, especially under low-speed shear conditions. Figures 9-12The results show that with the addition of In content, the strength initially increases and then decreases, reaching a maximum of 75 MPa at 8In. The strength after the decrease is slightly higher than that of SAC305 (58 MPa). Displacement, however, decreases gradually and then remains almost constant. Before 8In, the displacement drops significantly from 623 mm to 382 mm, and after 8In, it remains almost constant, decreasing to between 352-360 mm. This ultimately results in the corresponding shear energy decreasing in tandem with the In content. Considering that the Ag and Cu contents do not change significantly, and the cross-sectional compound sizes are not significantly different, fracture at low speeds is more related to the microstructure of the matrix. Before 8In, the corresponding matrix structure transforms from βSn to βSn(In), with solid solution strengthening leading to increased strength but decreased plasticity. After 8In, γInSn4 gradually forms and increases, even forming a single phase at 18In. The strength of γInSn4 is lower than that of βSn(In), thus the strength gradually decreases. The components containing γInSn4 exhibit low and similar displacements at low speeds, indicating that γInSn4 has a significant impact on its plasticity, which explains why. However, with varying strain rates, these different phase compositions exhibit different behaviors, with varying patterns in shear strength, displacement, and In content. At 4In, the In content increases slightly by 10 MPa, then gradually decreases to less than 90 MPa, lower than the strength of SAC305. When In increases to 8In, the displacement decreases from 256 mm in SAC305 to 180 mm, but the displacement trend after 8In shows a significant difference, increasing to the range of 453-513 mm, even higher than the displacement at low speeds.

[0025] Generally, as the strain rate increases, the fracture location of the solder joint shifts from inside the solder joint to the interface, as seen in SAC305 alloy. The displacement decreases, and the corresponding fracture mode changes from matrix-dominated to interface-dominated, resulting in increased strength and decreased displacement. This pattern also applies to 4In and 8In samples containing βSn(In). However, for the component containing γInSn4, the displacement generally increases at high speeds, indicating that the γInSn4-containing component has excellent drop impact resistance and can still fracture within the solder joint under high-speed shear conditions. The fracture energy is in the range of 7.7-8.95 mJ, more than twice that of SAC305. Furthermore, according to previous nanoindentation studies (see influence of Indium addition on microstructural and mechanical behavior of Sn solder alloys Experiments and first principles calculations), the higher the In content in the interface Cu6(Sn, In)5, the lower its Young's modulus and hardness value. After 8In, the strength of the solder matrix decreases slightly regardless of whether it is deformed at high or low speed. This means that the interface compound with higher In content has better deformation coordination with the solder matrix.

[0026] In summary, the peak temperatures of Examples 3-5 containing γInSn4 can not only be reduced to the range of 197-204 °C to lower the welding temperature, but also have better fracture energy under high-speed conditions due to the lower hardness of the Cu6(Sn, In)5 compound and the softer solder matrix.

[0027] The method for preparing the solder of this invention involves adding alloy raw materials to a vacuum furnace, heating and melting them to 400 °C, holding at that temperature for 30 minutes, and then casting them into a mold to form an alloy ingot. The alloy ingot is then processed into solder sheets or... solder powder In use, the solder sheet is rolled and punched into a thin circular sheet, then ultrasonically cleaned with alcohol, cleaned with dilute hydrochloric acid, ultrasonically cleaned with alcohol again, and dried. Flux is then applied to the sheet, which is placed on Cu pads for soldering to form solder joints. The reflow peak temperature is 260 ℃. Alternatively, the alloy can be centrifuged or ultrasonically atomized into solder powder, then flux is added in a certain proportion, stirred and mixed evenly to form solder paste, which is then printed onto Cu pads through a stencil and reflowed to form solder joints. The equipment used for testing the melting point in this invention is a NETZSCH STA 449F5 synchronous thermal analyzer. The test sample is a 50 mg alloy sheet, and the heating rate is 5 k / min.

[0028] Cross-sections of different weld joints were observed using a field emission scanning electron microscope (FET) after grinding and polishing. Weld reliability analysis was performed on a bond strength tester. For low-speed testing, a Dage 4000 shearing device was used with a shearing speed of 0.1 mm / s; for high-speed testing, a high-speed shearing device (Dage 4000 plus) was used with a shearing speed of 1000 mm / s. The shearing height was 50 μm in both cases, and samples under the same condition were repeated at least 10 times. The maximum shear force could be directly obtained from the maximum force value on the bond strength tester. The fracture energy was obtained by integrating the displacement-shear force curve. The specific calculation method is as follows: the displacement-shear force curve was plotted using Origin software, and the area between the entire curve and the corresponding displacement was calculated using the integration function to obtain the fracture energy. As the strain rate increases, the fracture mode of the weld joint shifts from fracture within the weld matrix to primarily interfacial fracture. Furthermore, high-speed shearing and drop tests showed a certain correlation; the higher the high-speed shear energy, the better the drop resistance of the corresponding weld joint. The microstructure was characterized using OM, SEM, and EPMA.

[0029] The application of the bismuth-free and lead-free multi-element SnIn solder of the present invention involves using the solder on a substrate containing the γInSn4 phase at the solder joint, and forming a Cu6(Sn, In)5 interface after soldering, wherein the atomic ratio of In in Cu6(Sn, In)5 is 5.6-7.4%.

[0030] The solder of this invention is particularly suitable for semiconductor device packaging interconnects that operate at low temperatures (195 ℃-215.0 ℃) and require high-speed mechanical conditions.

[0031] The above embodiments are only some embodiments of the present invention, not all embodiments, and are not intended to limit the scope of protection of the present invention.

[0032] Unless otherwise stated, all percentages mentioned in this invention are mass percentages.

Claims

1. A high-speed shear-resistant SnIn-based solder obtained by controlling the microstructure, characterized in that, The solder contains 0.05-0.2 wt.% Cu, 2.82-2.88 wt.% Ag, 12-18 wt.% In, with the balance being Sn. The mass ratio of (Ag+Cu) to In is 1:3.89~1:6.27, and the mass ratio of In to Sn is 1:7.09~1:23.

26. The melting point of the solder is 196.7 ℃-204.0 ℃. The solder is used to solder a substrate containing the γInSn4 phase, forming a Cu6(Sn, In)5 interface after soldering. The atomic ratio of In in Cu6(Sn, In)5 is 5.6-7.4%.

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