The directed coating Pd technology and coated Pd copper bonding wire were investigated by scan electronic microscopy,transmission electron microscope,focused ion beam and tensile strength tester,the effects of annealing temperature on Pd binding strength,wire tensile strength,elongation and Pd thickness of the direct coated Pd copper bonding wire were analyzed. The results show that Pd thickness is uniform after direct coating Pd. The bonding strength can increase when annealing temperature increases,and the binding strength is lower after annealing at 300 ℃,and some Pd3Cu5 can be found between Pd and Cu interface after annealing at 450 ℃,then the binding strength can meet the industrial demand. The tensile strength can decrease when annealing temperature increases,while the elongation can increase. When annealing temperature reaches 450 ℃,the Pd coated copper wire has excellent mechanical properties,and the tensile strength is 0. 096 N,elongation is 14. 3%,the Pd thickness is 78 nm. When annealing temperature reaches 500 ℃,the mechanical properties of Pd coated copper bonding wire decrease,and tensile strength is 0. 073 N,and elongation is 11. 6%.

In the study, the effect of silver alloy bonding wire properties on bonding strength was evaluated and the IMCs layer growth under these conditions was also discussed. It was found that the Zn elements in silver alloy bonding wire can decrease the coefficient of heat conductivity, the coefficient of heat conductivity is smaller 16%, and avoid to form golf ball and sharp ball. Long HAZ length will cause the ball neck crack and lead to black bonded or failure bonded, Zn elements can increase the recrystallized temperature, then decrease the HAZ length, the HAZ length decreased 25%. After HTS test, cracks phenomenon happens at the bonding interface because of Ag atoms rapidly migrate, Zn can decrease the Ag migrate rate and avoid the crack in bonded interface.

利用扫描电镜、强度测试仪分析了高纯铜线与微Sn合金铜线不同热处理温度下组织结构及强度、伸长率的差异,研究了高纯铜线、微Sn合金铜线再结晶行为及微量合金元素Sn对高纯铜线再结晶温度的影响机理.结果表明:Sn原子与铜原子间的化学交互作用与弹性交互作用,引起高纯铜的点阵畸变,阻碍再结晶过程中铜的晶界迁移,抑制再结晶和晶粒长大,使微Sn合金铜线再结晶温度由高纯铜线的400℃提高至450℃,且高纯铜线在热处理过程中晶粒增长与热处理时间呈四次方关系;微量Sn合金减少了无空气焊球热影响区长度,热影响区长度由150 μm减少至120 μm.

In the study, the effects of Pd thickness on free air ball, wire elongation/strength on bonding strength and bonding interface of Pd coated copper wire bonding were discussed. It was found that the Pd thickness effects on free air ball, the free air ball will become golf ball when the Pd thickness is thin excessively, then the Pd thickness is not less than 0.47% to the wire diameter, and high tensile strength and low elongation of the Pd coated copper wire will cause the second bond neck crack and irregular wedge formation for the second bond. After PCT test, voiding phenomenon happens at the bonding interface and the bonding strength also significantly reduced because little Pd doesn't form an effective protected layer on the bonded interface, and Cu9Al4 cannot be detected anymore because of corroding by Br. In the high temperature and high humidity condition, Pd coated copper wire with more Pd thickness can form an effective protected layer and increase the bonded strength.