To sum up, in view of the fatigue failure of solder wire solder joints, we require that the solder joints of solder wire must be very bright and not black in actual operation and application. The fatigue failure of solder wire solder joints mainly includes thermal fatigue and mechanical fatigue, of which thermal fatigue is the dominant cause. Thermal fatigue stems from the thermal cycle load and power cycle process that the solder joints bear during the working process, including isothermal mechanical fatigue caused by thermal mismatch. The following editor will share with you the solution to the fatigue failure of solder wire solder joints :

1. During the transportation and use of solder wire products after assembly, the solder joint is a weak link in reliability. It bears various functions such as thermal, electrical and mechanical connections, and is generally subject to periodic mechanical stress. And creep stress, especially in aerospace, aviation, marine and automotive products. If the process conditions are poor, the solder wire will melt and spread unevenly during the welding process, which is called segregation; segregation changes the mechanical and physical properties of the solder joints, affecting its working effect and service life; therefore, it must be prevented during the production process Solder wire segregation or unsatisfactory metallographic structure during solidification can effectively increase the inherent reliability or service life of solder joints.

2. For solder wire joints that are susceptible to cyclic stress, the stress relief scheme should be fully considered in planning. For example, to fix the mounting holes and fill the suspended component body with appropriate glue, it is also necessary to fully consider the matching of the linear expansion coefficients of various materials.

3. Reliability tests can be used to detect or expose early, and then take targeted corrective measures to deal with it.

The research on the reliability of tin-lead solder joints has always been paid attention to by people. The traditional method to improve the strength of tin-lead solder alloys is to add silver to tin-lead solder to improve the shear strength of solder joints; the same increase of antimony will also make The comprehensive mechanical properties of tin-lead solder, such as enhanced shear resistance, tensile resistance and creep resistance. In recent years, some people have used a small amount of rare metals to add tin-lead solder to achieve the purpose of enhancing the mechanical properties of the solder alloy. The creep life of the alloy solder is more than doubled. This is because the addition of Re can change the microstructure of the SnPb alloy, that is, the eutectic structure of the SnPb alloy changes from the original lamellar structure to a mixture of short rods and rods, and in the SnPbRe solder alloy, the tin-rich phase and the rich phase The distribution of the lead phase is also more uniform than that in SnPb, thus effectively changing the anisotropy of the tin crystal. When the solder is subjected to an external force, from a microscopic point of view, its fracture mode changes, that is, from the intergranular fracture mode to the transgranular fracture mode. It can be seen that the addition of mixed rare earths changes the fracture mode of the lead alloy, from the intergranular fracture mode to the transgranular mode, indicating that the addition of rhenium improves the plasticity and creep of the solder alloy, and the life is improved. Due to the addition of metal rhenium, the structure of SnPb is changed, which is of positive significance to enhance the creep resistance of SnPb alloy.