Study On Dynamic Mechanical Properties Of Low Silver Lead-Free Solder

It is inevitable to cause the portable electronic products drop or impact in the process oftransportation or application，so we expect the solder joints own excellent resistance todrop.In addition, the electronic components will release a lot of heat in the process of service,and lead to high temperature of solde accordingly. The lowest temperature of our country inthe history is around for-50℃, which will affect the mechanical properties of solder jointsin the use of electronic products under low or high temperature, thus the life of electronicproducts to use is affected. Currently, there is little research about the mechanical propertiesof solder joints under low temperature. Along with the improve of human awareness ofenvironmental protection and cost control of electronic industry, low-silver lead-free soldersproducts were gradually replaced high-silver solder products, also put forward the newsubject for the solder joint reliability.To solve the above problems, in this paper the mechanical properties of low silverlead-free solder and solder joint reliability of systematic were studied. The main work andresults list as follows:1）The mechanical properties of low silver solder Sn0.3Ag0.7Cu were characterized byusing an electronic universal material testing system and Split Hopkinson Pressure Bar(SHPB) under different conditions. The results show that, the strain rate hardening andtemperature softening effects on the plastic deformation of low silver solder Sn0.3Ag0.7Cuare different among experiment temperature ranges. In high temperatures (40℃~100℃), thestrain rate hardening effect and temperature softening effect were weaker than lowtemperature (-45℃~0℃). The dynamic constitutive relationship was determined throughthese experiments based on Johnson-Cook model.2）The model of VFBGA packaging in board-level drop condition was established by thefinite element method. The results show that, as for low silver lead-free solder Sn0.3Ag0.7Cu,the distribution of the maximum stress on the joints was observed in the interface of the solderjoints at low temperature; Compared with high silver solder, the maximum peeling stress oflow silver lead-free solder is much lower than that of the high silver solder, which shows better resistance to drop.