CN-122007709-A - High-reliability alloy solder capable of being welded at medium temperature and preparation method thereof

Abstract

The application provides a high-reliability alloy solder capable of being welded at medium temperature and a preparation method thereof, and relates to the technical field of welding materials. The soldering flux comprises alloy tin powder and soldering flux, wherein the alloy tin powder comprises first tin-based alloy powder and second tin-based alloy powder, the melting point of the first tin-based alloy powder is higher than that of the second tin-based alloy powder, the first tin-based alloy powder is Sn-rich tin-based alloy powder, the second tin-based alloy powder is tin-based alloy powder which is doped with Bi element and takes SnIn as a main component, and the doping amount of the Bi element in the second tin-based alloy powder is 0.8-1.4 wt%. The preparation method comprises the steps of pre-mixing alloy tin powder uniformly, pre-stirring raw materials of the soldering flux, adding the alloy tin powder, and stirring. The lead-free solder can reduce the cost of raw materials while ensuring the performance by taking the medium-temperature alloy powder as a main material and the high-temperature and low-temperature tin powder as an auxiliary material, can realize a lead-free formula, completely meets the environmental protection regulation requirements of European Union RoHS and the like, and avoids the compliance risk of lead-containing solder.

Inventors

• Shu Changrong
• LUO DENGJUN
• CHEN QIN
• LI WENHAO

Assignees

• 苏州优诺电子材料科技有限公司

Dates

Publication Date

20260512

Application Date

20260416

Claims (10)

1. 1. The high-reliability alloy solder capable of being welded at medium temperature is characterized by comprising alloy tin powder and soldering flux, wherein the alloy tin powder comprises first tin-base alloy powder and second tin-base alloy powder, the melting point of the first tin-base alloy powder is higher than that of the second tin-base alloy powder, the first tin-base alloy powder is tin-base alloy powder rich in Sn, the second tin-base alloy powder is tin-base alloy powder doped with Bi element and taking SnIn as a main component, and the doping amount of the Bi element in the second tin-base alloy powder is 0.8-1.4 wt%.
2. 2. The high reliability alloy solder for medium temperature soldering according to claim 1, wherein the first tin-based alloy powder is SnAgCu alloy powder.
3. 3. The high reliability alloy solder for medium temperature soldering according to claim 2, wherein the mass ratio of the first tin-based alloy powder to the second tin-based alloy powder is 5-16:34-45.
4. 4. The high-reliability alloy solder capable of being welded at medium temperature according to claim 2, wherein the second tin-based alloy powder is further doped with Ag element and Cu element, and the sum of doping amounts of the Bi element, the Ag element and the Cu element is 4.9wt% to 5.3wt%.
5. 5. The high reliability alloy solder of claim 4 wherein the second tin-based alloy powder is one or more of sn75in20ag2.8cu0.8bi1.4, sn70in25ag3.0cu1.0bi1.0, sn85.1in10ag2.5cu1.2bi1.2, sn72.7in22ag3.0cu1.5bi0.8.
6. 6. The high reliability alloy solder of claim 2 wherein said alloy tin powder further comprises a third tin-based alloy powder having a lower melting point than said second tin-based alloy powder.
7. 7. The high reliability alloy solder for medium temperature soldering according to claim 6, wherein the third tin-based alloy powder is SnBi alloy powder.
8. 8. The high reliability alloy solder for medium temperature soldering according to claim 7, wherein the mass ratio of the first tin-based alloy powder, the second tin-based alloy powder and the third tin-based alloy powder is 4-6:13:1-3.
9. 9. The high-reliability alloy solder capable of being welded at medium temperature according to claim 1, wherein the first tin-based alloy powder is tin-based alloy powder doped with Bi element and mainly containing SnIn, and the mass ratio of the first tin-based alloy powder to the second tin-based alloy powder is 1:1.
10. 10. Method for the production of a high-reliability alloy solder that can be soldered at medium temperature according to any of claims 1 to 9, characterized in that it comprises the following steps: uniformly mixing alloy tin powder in advance in an inert environment; Pre-stirring raw materials of the soldering flux, scraping the wall after the pre-stirring, vacuumizing to the vacuum degree of-0.08 MPa, stirring once again, adding alloy tin powder which is uniformly mixed, stirring twice, scraping the wall after the pre-stirring, vacuumizing to the vacuum degree of-0.08 MPa, and stirring for three times to obtain the soldering flux.

Description

High-reliability alloy solder capable of being welded at medium temperature and preparation method thereof Technical Field The application relates to the technical field of welding materials, in particular to a high-reliability alloy solder capable of being welded at medium temperature and a preparation method thereof. Background With the development of miniaturization and high density in electronic manufacturing industry, higher requirements are being placed on thermal compatibility and reliability of soldering materials. The existing lead-free solder has the obvious technical defects that the melting point of high-temperature lead-free solder paste is more than or equal to 217 ℃, the temperature sensitive elements such as a sensor are easy to damage during welding, the energy consumption is high, the melting point of low-temperature lead-free solder paste is less than or equal to 173 ℃, the welding spot brittleness is high, the thermal fatigue resistance is poor, and the long-term reliability requirement of the welding spot cannot be met although the risk of thermal damage is low. In order to solve the contradiction, a medium Wen Xigao scheme is provided in the industry, but the prior medium Wen Xigao adopts a single alloy system, and has the problems of poor welding spot stability, insufficient wettability and the like. For example, china patent publication No. CN108746523A discloses Wen Xigao in a Sn-Bi-Ag-Cu system, the melting point of which is controlled between 175 ℃ and 185 ℃, but the bismuth content in the Sn-Bi-Ag-Cu system is as high as 35% -45%, the elongation of a welding spot is only 8% -10%, and the Sn-Bi-Ag-Cu system is easy to crack after long-term use. Therefore, there is a need to develop a moderate temperature mixed solder paste that has a melting point stable between 183-217 ℃ and combines mechanical strength and thermal reliability, and is compatible with a fine SMT process. Disclosure of Invention In order to solve the problem that the solder in the prior art cannot achieve both mechanical strength and thermal reliability, the application provides a high-reliability alloy solder capable of being welded at medium temperature and a preparation method thereof. In a first aspect, the application provides a high-reliability alloy solder capable of being welded at a medium temperature, which adopts the following technical scheme: the high-reliability alloy solder capable of being welded at medium temperature comprises alloy tin powder and soldering flux, wherein the alloy tin powder comprises first tin-base alloy powder and second tin-base alloy powder, the melting point of the first tin-base alloy powder is higher than that of the second tin-base alloy powder, the first tin-base alloy powder is tin-base alloy powder rich in Sn, the second tin-base alloy powder is tin-base alloy powder which is doped with Bi element and takes SnIn as main components, and the doping amount of the Bi element in the second tin-base alloy powder is 0.8-1.4 wt%. According to the application, two tin-base alloy powders with different melting points are mixed, so that the melting point temperature of solder can be obviously reduced, heat-sensitive components can be effectively protected during welding, and meanwhile, the mechanical strength and long-term reliability of welding spots can be greatly improved. In the welding process, the second tin-base alloy powder is melted first to form a liquid phase, wets and spreads on the bonding pad and the element pins, at this time, the first tin-base alloy powder still maintains the form of solid phase particles, and the solid phase particles are dispersed in the liquid phase as a supporting framework, so that excessive flow and collapse of liquid solder are effectively inhibited, and the liquid solder becomes a crystal core in the subsequent solidification, and grains are refined. After solidification of the solder, the high melting point phase exists in the joint as a reinforcing phase, so that the mechanical strength of the welding spot is improved. Meanwhile, the Bi doping in the second tin-base alloy powder can not only effectively reduce the melting point of the SnIn alloy, but also avoid the coarsening of a brittle phase caused by excessive Bi, thereby reducing the process temperature and simultaneously ensuring the toughness and the reliability of the joint. Optionally, the first tin-based alloy powder is SnAgCu alloy powder. By adopting SnAgCu alloy powder as a high-melting-point framework phase, the intrinsic strength of the joint can be enhanced, thereby laying a high-reliability microstructure foundation. Optionally, the mass ratio of the first tin-base alloy powder to the second tin-base alloy powder is 5-16:34-45. The application ensures that enough low-melting-point liquid phase is available for realizing good wetting and filling at the target welding temperature by limiting the dosage of the two tin-base alloy powders, and simultaneously, enough high-melti