Design And Preparation Of Self-adapting/Self-repairing Solder System And Its Mechanical Behavior

With the rapid development of modern equipment manufacturing industry,intelligent self-repair technology has become an international research focus.From the perspective of materials,if it is possible to realize the bionic design of the soldering structure,so that it will has adaptive/self-repair capacity,which can greatly improve the safety and reliability of service welding points and prevent the failure of the system.First of all,we choose InSn/SnPb/AlNi nanofoils as the design material of the solder system.The metallurgical compatibility of InSn SnPb solder was studied by adding local hot air method,and the structure of the intelligent solder system was successfully prepared by low temperature heating method.The self-repairing ability of InSn/SnPb solder system with different thickness ratio was evaluated and its performance in fatigue crack repair was studied.The self-repairing structure was also applied to the repair design of SnAgCu and Sn Zn Bi smart solder system.The reaction mechanism and exotherm of Al/Ni nanofoils were studied by DSC and XRD.The influence of aging temperature/time on the heat release of the foils was analyzed,and the life prediction model of the intelligent solder system was established.Results show:(1)InSn/SnPb solder system has good metallurgical compatibility.The elements of Indium have significant solid solubility strengthening and fine-grained reinforcement for the matrix SnPb.With the increasesing of repairing temperature and extending of effective time,the solder system repairing strength increaseing;Compared to the time factor,the effect of temperature on the joint repairing is more significant.(2)The introduction of Al/Ni nanofoils can fully melt the InSn solder and wet it into the prefabricated crack of SnPb solder sheet to realize the self-repairing function of the system.Compared to 0.2mm InSn solder sheet,The system of 0.05 mm InSn solder repair more efficient under the reaction of the 40mm Al/Ni nanofoils: the self-repairing efficiency of prefabricated single crack sample is up to 90% or more,and the rate of prefabricated double crack sample reaches more than 60%.for its application to the Cu plate brazing joints,the efficiency ratio of fatigue crack repairing can exceed 70% or more.Based on the repair structure,SnAgCu and SnZnBi intelligent solder system have achieved better self-repairing effect,and the repair efficiency can reach more than 90%.(3)The reaction mechanism and exotherm of Al/Ni nanofoils were investigated by DSC and XRD.The Al/Ni→Al3Ni→Al3Ni2→AlNi phase transition in Al/Ni thin films was found.The results show that the exothermic loss caused by the pre-diffusion layer is mainly concentrated in the first stage of the reaction.The life model of SnPb /InSn/nanofoils solder system was successfully established by theoretical calculation and finite element simulation.The temperature distribution of self-repairing process of system was outputted.