Study On Electromigration Of Sn2.5Ag0.7Cu0.1RE/Cu Brazed Joints Under Thermal Cycling

With the rapid development of microelectronic products,higher requirements for the quality of micro connection lead free soldering joints are put forward.SnAg Cu,especially SnAg CuRE lead-free solder alloy in China is unique as the best substitute of Sn-Pb solder,the solder joint electromigration problems directly affect the reliability of electronic products,has become an urgent problem in production and application.It is of important engineering value to carry out electromigration studies on lead-free brazed joints under thermal cycling and to find effective methods and measures.According to the actual lead-free soldering electromigration,a welding head electromigration test device for thermal cycle drill was developed on the basis of this,discusses the actual Sn2.5Ag0.7Cu0.1RE/Cu solder joint thermal effects on electromigration and electromigration parameters,the research of the solder joints under thermal cycling and performance electric transfer organization,the corresponding improvement measures were proposed.The results show that the test device for electromigration of brazed joints under thermal cycle has the function of electromigration test under constant temperature and thermal cycles.Main technical parameters: lap joint of 0.2~2mm2 joint size.The range of current density is 0~1×104A/cm2,the range of temperature change is-40 ℃~+125 ℃,the rate of rise and fall is 3~15 ℃ /min,and the humidity range is 20%~98%.The test device has the characteristics of high testing accuracy,convenient operation and safe operation.It can meet the needs of the application of electromigration under thermal cycle.Electromigration plays a major role in the thermal cycle of Sn2.5Ag0.7Cu0.1RE/Cu brazing joint at 100 degrees oil bath,100 ℃ air temperature and average temperature 100 ℃,and the thermal effect plays a role in promoting electromigration.With the Sn2.5Ag0.7Cu0.1RE/Cu solder joints at 100 ℃ and 100 ℃ oil bath air and the average temperature of 100 ℃ heat cycle thermal effect increases,corresponding to the brazing joint transfer interface IMC thickness increased,t he anode side of the cathode side IMC cracks and holes increased correspondingly lower joint shear strength.In thermal cycling,the current density affects the maximum of electromigration in Sn2.5Ag0.7Cu0.1RE/Cu brazed joints.When the current density is greater than 7×103A/cm2,Sn2.5Ag0.7Cu0.1RE/Cu solder joint interface of anode side IMC thickness exponent increases,the cathode side IMC defects increase,with the typical electromigration phenomena in organization feature is obvious.The Sn2.5Ag0.7Cu0.1RE/Cu brazing joint has a greater thermal effect at the thermal cycle temperature rise rate of 9 ℃ /min and 15 cycles,and a more pronounced electromigration phenomenon occurs under the thermal cycle of the brazed joint.In the electrifying test of Sn2.5Ag0.7Cu0.1RE/Cu brazed joint under thermal cycle,the current density is less than 7×103A/cm2,the thickness and roughness of the anode and cathode of the joint interface are almost the same as that of the cathode,and it is in the incubation period of IMC.When the current density is greater than 7×103A/cm2,Sn2.5Ag0.7Cu0.1RE/Cu solder joint in the common role of electromigration and thermal effects,with the increase of soldering current density and thermal effect,the anode side interface IMC thickness and roughness exponent increased rapidly,the morphology of IMC by the "Scallop in Shell" became "bamboo shoots" and extends to the drill the weld interface;the cathode side IMC thickness increased slightly but roughness increases rapidly,and the emergence of more cracks and holes.Sn2.5Ag0.7Cu0.1RE/Cu braze welding head transition between shear fracture under thermal cycles by brazing and the interface of the cathode side IMC is mixed fracture to dimple fracture facet and local interface to the cathode side with IMC cleavage and fracture facet based brittle fracture,according to the joint shear strength reduction.