Microalloyed Au-20Sn Eutectic Alloy Of Solidification Structure And Hot Compression Deformation Behavior

Au-20Sn eutectic alloy solder is widely used in the packaging of microelectronics and photoelectronic devices due to its excellent physicochemical property.In order to improve the wokability of Au-20Sn eutectic by conventional method,study have been taken for example,composition adjustment,melt mixing and deep supercooling on Au-20Sn eutectic alloy.However,little research reports employ microalloying method to Au-20Sn eutectic alloy.Therefore,it is worth to do some research on microalloyed Au-Sn eutectic alloy and study solidification structure and hot compression performance to improve workability of Au-20Sn eutectic alloy.In this paper,by adding the third component(Pt,Pd,Cu and Ag)to Au-Sn eutectic alloy,solidification structure was explored in three condition,different solidification conditions(cold graphite pouring,furnace-cooling),spheroidizing annealing,hot compression.The results showed:(1)Via adding Pt(200ppm),the volume fraction of primary phase(?'-Au5Sn)has reduced from15%to 2%and its morphology changed from dendrites to near-spherical particle and eutectic structure was refined(layer thickness is about 40 nm)by using cold graphite mold casting with 370? pouring temperature.(2)Via adding Pd(200ppm),using cold graphite mold to casting and under 370?of pouring temperature,the volume fraction of primary phase(?'-Au5Sn)goes up to 25%and layer became coarsened(layer thickness is about 102nm).The addition of small amount of Cu and Ag has little improvement for eutectic structure refinement.(3)The microalloyed solidification structure can be improved by increasing solidification cooling rate.Compared with the furnace-cooling,casting by cold graphite could refine solidification structure,and reduce volume fraction of primary and lamellar spacing.When using cold graphite,decreasing temperature from 400?to 370? better solidification structure could be obtain.and growth rate is closer,so(4)The lamellar structure of microalloyed Au-Sn alloy could be spherized by annealing.Under the condition of 230?×60min annealing,microalloyed alloy with Pt adding could be spherized totally with particle size of 1 ?n.When decrease the anneal temperature(220?),only part of layer could be spherized and structure would grow up when annealing temperature is 240?(5)Adding Pt(200ppm)can effectively improve hot compression performance of the Au-Sn eutectic alloy.Yield stress reduced 20%,and the rheological softening rate increased,and the steady-state flow stress reduced about 30%.Dynamic recrystallization occurs during hot compression.(6)There has been little improvement to the thermal compression performance by adding Cu and Ag of 200ppm.The addition of Pd of 200ppm has disavantage on the hot compression performance in which yield stress and steady-state flow stress increases.