A high temperature tin-based alloy solder

Abstract

The application discloses a high-temperature tin-based alloy solder and belongs to the technical field of electronic packaging materials and electronic material preparation. The tin-based alloy solder is composed of Sn, Cu, Pt and Al alloy elements, and the mass percentage of each component element is as follows: Cu: 0.7%, Pt: 0.01-0.2%, Al: 0.01-0.05%, and the balance is Sn. The preparation method comprises the following steps: melting Sn, Cu, Pt and Al alloy raw materials, and then cooling to room temperature in a furnace; then turning over the cooled test tube, remelting, and repeating the step twice; after the third remelting, the solder is cooled to 250 DEG C in the furnace, taken out and air-cooled to room temperature to obtain the high-temperature tin-based alloy solder. The novel tin-based lead-free solder prepared by the application can replace the traditional high-temperature Sn-0.7Cu solder, and has the characteristics of high hardness, good plasticity and toughness, good thermodynamic stability, high solder joint bonding strength, bright solder joint surface and long service life.

Description

Technical Field

[0001] This invention belongs to the field of electronic packaging materials and electronic material preparation technology, and specifically relates to a high-temperature tin-based alloy solder. Background Technology

[0002] Sn-based lead-free solders are mainly divided into Sn-Ag, Sn-Cu, Sn-Bi, Sn-In, and Sn-Zn systems. Based on their melting points, they are further categorized into high-temperature solders (melting points above 200℃), medium-temperature solders (melting points between 180-200℃), and low-temperature solders (melting points below 180℃). Low-temperature solders are primarily used in the low-temperature assembly of heat-sensitive electronic components such as LCD / LED displays, high-frequency heads, surge protectors, temperature control components, and flexible boards. High-temperature solders are mainly used for assembling components that do not change during motherboard assembly; low-temperature solders are mainly used for assembling components with low heat resistance, such as microelectronic sensors. In particular, with the widespread use of high-power electronic components, high-temperature control circuits, and 3D integrated circuit technology in recent years, solder joints often generate significant heat during use, especially during power-on and power-off cycles when the instantaneous temperature of the joint exceeds 200℃. Under these conditions, traditional low-temperature and medium-temperature solders are insufficient to meet the soldering requirements. Therefore, the development of new high-temperature solders with good soldering stability remains a significant focus.

[0003] Among a series of high-temperature lead-free solders that have been developed and researched, Sn-Cu series solders are the most inexpensive. However, high-temperature Sn-Cu alloy solders have some unavoidable problems: First, the addition of a tertiary component can improve some properties of the alloy solder while deteriorating others. For example, while the addition of Ag improves the mechanical properties of the alloy solder, it reduces its corrosion resistance. Second, during the soldering process, the transformation of the Cu6Sn5 hexagonal η phase at the interface into the monoclinic η′ phase results in a 2.15% volume expansion, leading to significant stress generation and cracking at the interface. Furthermore, although SAC type solders can achieve good bonding between devices, the problems of brittle fracture between intermetallic compound (IMC) layers and electromigration failure caused by Kirkendal voids during later use remain unresolved. Finally, the excessive growth of the brittle Cu3Sn intermetallic compound phase during later service life reduces the shock and impact resistance of the solder joints. These issues have negatively impacted the further industrial application of this solder, particularly in handheld electronic devices, the shipbuilding industry, and extreme service environments. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a high-temperature tin-based alloy solder by adding Pt and Al to Sn-Cu alloy solder, thereby solving the problems of easy brittle fracture, easy formation of Kokendal voids, poor thermodynamic stability, and poor stability and reliability of existing Sn-Cu alloy solders.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-temperature tin-based alloy solder comprises the following components in weight percentage: Cu: 0.7%, Pt: 0.01%–0.2%, Al: 0.01%–0.05%, with the balance being Sn; the alloy microstructure of the high-temperature tin-based alloy solder comprises strip-shaped PtSn4, strip-shaped Cu6Sn5, lamellar (Cu,Pt)6(Sn,Al)5 solid solution, and Sn matrix.

[0007] This invention also claims a method for preparing the high-temperature tin-based alloy solder, comprising the following steps:

[0008] (1) Weigh out the four alloy raw materials Sn, Cu, Pt and Al according to their mass percentages, and then put the weighed raw materials into a glass tube for vacuum sealing. The vacuum degree inside the glass tube is 10. -4 Pa, the sealed tube is placed in a muffle furnace for melting, and then cooled to room temperature in the furnace;

[0009] (2) After cooling, the test tube is turned over and put back into the muffle furnace for remelting. This step is repeated twice. After the third remelting, the solder is cooled to 250°C with the furnace and then taken out and air-cooled to room temperature to obtain high-temperature tin-based alloy solder.

[0010] In a preferred embodiment of the present invention, the alloy microstructure of the tin-based alloy solder further includes Al2Cu.

[0011] In a preferred embodiment of the present invention, the melting temperature is 1050°C and the melting time is 12 hours.

[0012] In a preferred embodiment of the present invention, the remelting temperature is 800°C and the time is 2 hours.

[0013] Invention Principle: During the welding process of Sn-0.7Cu type alloy solder, a chemical reaction occurs at the interface: 6Cu + 5Sn → Cu6Sn5. When Pt and Al are added to the solder, firstly, because Pt and Sn readily react to form PtSn4, and PtSn4 has good thermodynamic stability, the diffusion rate of Sn atoms is suppressed. Secondly, Al atoms readily adsorb and capture diffusing Cu atoms, thus Al can suppress the diffusion rate of Cu atoms, leading to a more stable interface structure. On the other hand, during solidification, Pt and Al can dissolve into Cu6Sn5 to form a (Cu,Pt)6(Sn,Al)5 solid solution. The E of this solid solution... i A large / H value indicates good ductility and toughness, while also being less prone to phase transformation that could lead to stress concentration at the interface.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] (1) The high-temperature tin-based alloy solder of the present invention has a uniform composition. Pt and Al are added to the brittle intermetallic compound, which improves the plasticity and toughness of the intermetallic compound. In addition, it suppresses the abnormal growth of intermetallic compound at the interface and also suppresses the phase transformation problem of Cu6Sn5 generated at the interface, which alleviates the problem of stress cracking caused by phase transformation during cooling. It has good industrial application value.

[0016] (2) The high-temperature tin-based alloy solder has the characteristics of high hardness, good plasticity and toughness, high bonding strength of welding joints and bright surface of welding joints. It also has the advantages of good thermodynamic stability of intermetallic compounds at the joints, low formation rate of Kirkendal voids at the interface and long service life. Attached Figure Description

[0017] Figure 1 The image shows a SEM image of the high-temperature tin-based alloy solder prepared in Example 1.

[0018] Figure 2 The image shows a SEM image of the high-temperature tin-based alloy solder prepared in Example 2.

[0019] Figure 3 The image shows a SEM image of the high-temperature tin-based alloy solder prepared in Example 3.

[0020] Figure 4 Comparison of Vickers hardness test indentations of the high-temperature tin-based alloy solders prepared in Examples 1-3 and Comparative Example 1. Detailed Implementation

[0021] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0022] Example 1

[0023] The tin-based solder provided by this invention is composed of four alloying elements: Sn, Cu, Pt and Al. The mass percentages of each component are Cu: 0.7%, Pt: 0.175%, Al: 0.01%, and the balance is Sn.

[0024] The preparation process of this alloy solder is as follows:

[0025] (1) Weigh out the required Sn, Cu, Pt and Al alloy raw materials according to the mass percentage, and put the weighed raw materials into a glass tube for vacuum sealing. The vacuum degree inside the glass tube is 10. -4 Pa. The sealing tube was placed in a muffle furnace for melting at a temperature of 1050℃ for 12 hours, and then cooled to room temperature with the furnace.

[0026] (2) After cooling, the test tube is inverted and placed back into the muffle furnace for remelting at a temperature of 800°C for 2 hours. To ensure uniform composition, this step is repeated twice. After the third remelting, the solder is cooled to 250°C in the furnace and then air-cooled to room temperature to obtain the final alloy solder.

[0027] SEM images of the tin-based alloy solder prepared in this embodiment are as follows: Figure 1 As shown, by Figure 1 It can be seen that the alloy is mainly composed of long strip-shaped PtSn4, strip-shaped Cu6Sn5, plate-shaped (Cu,Pt)6(Sn,Al)5 solid solution and Sn matrix.

[0028] Example 2

[0029] The present invention provides a Sn-0.7Cu quaternary tin-based alloy solder, which is composed of four alloying elements: Sn, Cu, Pt and Al. The mass percentages of each component are Cu: 0.7%, Al: 0.025%, Pt: 0.01%, and the balance is Sn.

[0030] The preparation process of this alloy solder is as follows:

[0031] (1) Weigh out the required Sn, Cu, Pt and Al alloy raw materials according to the mass percentage, and put the weighed raw materials into a glass tube for vacuum sealing. The vacuum degree inside the glass tube is 10. -4 Pa. The sealing tube was placed in a muffle furnace for melting at a temperature of 1050℃ for 12 hours, and then cooled to room temperature with the furnace.

[0032] (2) After cooling, the test tube is inverted and placed back into the muffle furnace for remelting at a temperature of 800°C for 2 hours. To ensure uniform composition, this step is repeated twice. After the third remelting, the solder is cooled to 250°C in the furnace and then air-cooled to room temperature to obtain the final alloy solder.

[0033] SEM images of the tin-based alloy solder prepared in this embodiment are as follows: Figure 2 As shown, by Figure 2 It can be seen that the alloy is mainly composed of long strip-shaped PtSn4, strip-shaped Cu6Sn5, plate-shaped (Cu,Pt)6(Sn,Al)5 solid solution and Sn matrix.

[0034] Example 3

[0035] The present invention provides a Sn-0.7Cu quaternary tin-based alloy solder, which is composed of four alloying elements: Sn, Cu, Pt and Al. The mass percentages of each component are Cu: 0.7%, Pt: 0.175%, Al: 0.025%, and the balance is Sn.

[0036] The preparation process of this alloy solder is as follows:

[0037] (1) Weigh out the required Sn, Cu, Pt and Al alloy raw materials according to the mass percentage, and put the weighed raw materials into a glass tube for vacuum sealing. The vacuum degree inside the glass tube is 10. -4 Pa. The sealing tube was placed in a muffle furnace for melting at a temperature of 1050℃ for 12 hours, and then cooled to room temperature with the furnace.

[0038] (2) After cooling, the test tube is inverted and placed back into the muffle furnace for remelting at a temperature of 800°C for 2 hours. To ensure uniform composition, this step is repeated twice. After the third remelting, the solder is cooled to 250°C in the furnace and then air-cooled to room temperature to obtain the final alloy solder.

[0039] SEM images of the tin-based alloy solder prepared in this embodiment are as follows: Figure 3 As shown, by Figure 3 It can be seen that the alloy is mainly composed of long strip-shaped PtSn4, strip-shaped Cu6Sn5, plate-shaped (Cu,Pt)6(Sn,Al)5 solid solution and Sn matrix.

[0040] Example 4

[0041] The present invention provides a Sn-0.7Cu quaternary tin-based alloy solder, which is composed of four alloying elements: Sn, Cu, Pt and Al. The mass percentages of each component are Cu: 0.7%, Pt: 0.2%, Al: 0.05%, and the balance is Sn.

[0042] The preparation process of this alloy solder is as follows:

[0043] (1) Weigh out the required Sn, Cu, Pt and Al alloy raw materials according to the mass percentage, and put the weighed raw materials into a glass tube for vacuum sealing. The vacuum degree inside the glass tube is 10. -4Pa. The sealing tube was placed in a muffle furnace for melting at a temperature of 1050℃ for 12 hours, and then cooled to room temperature with the furnace.

[0044] (2) After cooling, the test tube is inverted and placed back into the muffle furnace for remelting at a temperature of 800°C for 2 hours. To ensure uniform composition, this step is repeated twice. After the third remelting, the solder is cooled to 250°C in the furnace and then air-cooled to room temperature to obtain the final alloy solder.

[0045] The tin-based alloy solder prepared in this embodiment is mainly composed of strip-shaped PtSn4, strip-shaped Cu6Sn5, plate-shaped (Cu,Pt)6(Sn,Al)5 solid solution and Sn matrix, and contains a small amount of dispersed Al2Cu.

[0046] Comparative Example 1

[0047] The present invention provides a tin-based solder composed of Sn and Cu alloying elements, with each component having a mass percentage of Cu: 0.7% and the balance being Sn.

[0048] The preparation process of this alloy solder is as follows:

[0049] (1) Weigh the required Sn and Cu alloy raw materials according to the mass percentage, and put the weighed raw materials into a glass tube for vacuum sealing. The vacuum degree inside the glass tube is 10. -4 Pa. The sealing tube was placed in a muffle furnace for melting at a temperature of 1050℃ for 12 hours, and then cooled to room temperature with the furnace.

[0050] (2) After cooling, the test tube is inverted and placed back into the muffle furnace for remelting at a temperature of 800°C for 2 hours. To ensure uniform composition, this step is repeated twice. After the third remelting, the solder is cooled to 250°C in the furnace and then air-cooled to room temperature to obtain the final alloy solder.

[0051] The tin-based alloy solder prepared in this comparative example is mainly composed of blocky Cu6Sn5 and Sn matrix.

[0052] Comparative Example 2

[0053] The present invention provides a tin-based solder composed of Sn, Cu and Al alloying elements, with the following mass percentages: Cu: 0.7%, Al: 0.01%, and the balance being Sn.

[0054] The preparation process of this alloy solder is as follows:

[0055] (1) Weigh the required Sn, Cu and Al alloy raw materials according to the mass percentage, and put the weighed raw materials into a glass tube for vacuum sealing. The vacuum degree inside the glass tube is 10. -4Pa. The sealing tube was placed in a muffle furnace for melting at a temperature of 1050℃ for 12 hours, and then cooled to room temperature with the furnace.

[0056] (2) After cooling, the test tube is inverted and placed back into the muffle furnace for remelting at a temperature of 800°C for 2 hours. To ensure uniform composition, this step is repeated twice. After the third remelting, the solder is cooled to 250°C in the furnace and then air-cooled to room temperature to obtain the final alloy solder.

[0057] The tin-based alloy solder prepared in this comparative example is mainly composed of blocky Cu6Sn5 and Sn matrix.

[0058] Comparative Example 3

[0059] The tin-based solder provided by this invention is composed of Sn, Cu and Pt alloying elements, with the following mass percentages: Cu: 0.7%, Pt: 0.175%, and the balance being Sn.

[0060] The preparation process of this alloy solder is as follows:

[0061] (1) Weigh the required Sn, Cu and Pt alloy raw materials according to the mass percentage, and put the weighed raw materials into a glass tube for vacuum sealing. The vacuum degree inside the glass tube is 10. -4 Pa. The sealing tube was placed in a muffle furnace for melting at a temperature of 1050℃ for 12 hours, and then cooled to room temperature with the furnace.

[0062] (2) After cooling, the test tube is inverted and placed back into the muffle furnace for remelting at a temperature of 800°C for 2 hours. To ensure uniform composition, this step is repeated twice. After the third remelting, the solder is cooled to 250°C in the furnace and then air-cooled to room temperature to obtain the final alloy solder.

[0063] The tin-based alloy solder prepared in this comparative example mainly consists of strip-shaped PtSn4, strip-shaped Cu6Sn5, and a Sn matrix.

[0064] Example of effect

[0065] The properties of the solders prepared in the above embodiments and comparative examples are listed in Table 1 below:

[0066] Table 1

[0067]

[0068] As shown in Table 1, the addition of Pt and Al within the composition range of the invention has little effect on the melting point of the alloy solder. Compared with Sn-0.7Cu binary alloy solder, the addition of Pt and Al significantly inhibits the thickness of the intermetallic compound layer at the welding interface, reduces the Kirkendal porosity, and improves the thermodynamic stability of IMCs. Among them, the Sn-0.7Cu-0.175Pt-0.025Al quaternary alloy solder has the smallest intermetallic compound layer thickness at the welding interface, the highest hardness of the alloy solder itself, and the highest E of the IMCs. i The high H-value, low defect concentration, and low heat of generation indicate that the quaternary alloy solder in this invention has superior overall performance.

[0069] As shown in Example 1 and Comparative Examples 1-3, the absence of one or both of Pt and Al causes an increase in the thickness and a decrease in the hardness of the IMCs layer. This is because, on the one hand, Pt and Al can suppress the diffusion rates of Sn and Cu atoms, respectively. Specifically, Pt and Sn form PtSn4, which stabilizes Sn atoms, while Cu and Al form Al. x Cu y The compound stabilizes Cu atoms; secondly, the resulting (Cu,Pt)6(Sn,Al)5 solid solution exhibits high thermodynamic stability and reduces the degree of non-uniform atomic diffusion. When both elements are added simultaneously, Pt and Al synergistically slow down the growth rate of the IMCs layer; on the other hand, the addition of Pt and Al has a grain-refining strengthening effect, which can lead to an increase in the hardness of the alloy solder. According to Figure 4 It can be seen that the hardness of the alloy solders in Examples 1-3 is higher than that in Comparative Example 1. The more types of elements added to the Sn-0.7Cu binary alloy solder, the better. If Pt and Al are added to the Sn-Cu-Pt-Al alloy solder, and then other elements, such as Zn or Bi, are added, new brittle IMCs (such as Cu5Zn8 and Bi-rich phases) are easily generated at the interface due to the influence of solubility during the welding process. These brittle IMCs seriously threaten the connection stability of the weld joint.

[0070] 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 high-temperature tin-based alloy solder, characterized in that, The composition includes the following components by mass percentage: Cu: 0.7%, Pt: 0.01%~0.2%, Al: 0.01%~0.05%, with the balance being Sn; the alloy microstructure of the high-temperature tin-based alloy solder includes strip-shaped PtSn4, strip-shaped Cu6Sn5, plate-shaped (Cu,Pt)6(Sn,Al)5 solid solution and Sn matrix; The preparation method of the high-temperature tin-based alloy solder includes the following steps: (1) Weigh out the four alloy raw materials Sn, Cu, Pt and Al according to their mass percentages, and put the weighed raw materials into a glass tube for vacuum sealing. The vacuum degree inside the glass tube is 10. 4 Pa, the sealed tube is placed in a muffle furnace for melting, and then cooled to room temperature in the furnace; (2) After cooling, the test tube is turned upside down and put back into the muffle furnace for remelting. This step is repeated twice. After the third remelting, the solder is cooled to 250°C with the furnace and then taken out and air-cooled to room temperature to obtain high-temperature tin-based alloy solder. The alloy microstructure of the high-temperature tin-based alloy solder also includes Al2Cu; The melting temperature is 1050℃ and the melting time is 12h; The remelting temperature is 800℃ and the time is 2 hours.

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