Solder wire is one of the indispensable auxiliary materials in the welding of electronic products. That is to say, the use of solder wire is very critical, such as improper operation or process differences and other external factors. Both will lead to the welding effect of solder wire. Let's mainly understand the little knowledge about fatigue failure of solder wire solder joints:
Fatigue in solder joints is firstly caused by cyclic plastic deformation due to temperature changes caused by intermittent current flow in electronic components. The consequence of this fatigue is that it will lead to the cracking and failure of solder joints, or the unbroken contact state will reduce the reliability of electronic products.
Secondly, the fatigue of solder joints of electronic products belongs to low-cycle fatigue (usually the cycle time is 2-3h/cycle longer). We conducted shear tests on 63Sn37Pb solder at 25°C, and found that the fatigue life of tin-lead solder increases with the cycle frequency. and decrease with increasing ambient temperature.
Third, the fatigue damage of solder joints is not only related to the cycle frequency, but also closely related to the welding quality. A well wetted solder joint is more resistant to fatigue than a poorly wetted solder joint.
Fourth, the microscopic cause of solder joint fatigue damage is that the solder tin crystal has a square lattice structure. Due to the anisotropy of the crystal, the thermal expansion coefficient along the crystal axis is different. In addition, the lead crystal has a face-centered cubic lattice structure. , when the temperature changes, the difference in the ratio of tin to lead and its thermal expansion coefficient will also aggravate the fatigue damage of the solder joint. The performance of fatigue damage is that the originally smooth solder surface becomes very rough, and cracks will appear in extreme cases. Solder joint fatigue damage has guiding significance for solder products.
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