The electromigration behavior of eutectic SnAg solder reaction couples was studied at various temperature （25 and 120℃ when the current density was held constant at 104 A/cm^2 or 5×10^3 A/cm^2. Under the curren...The electromigration behavior of eutectic SnAg solder reaction couples was studied at various temperature （25 and 120℃ when the current density was held constant at 104 A/cm^2 or 5×10^3 A/cm^2. Under the current density of 104 A/cm^2, scallop type Cu6Sn5 spalls and migrates towards the direction of electron flow at room ambient temperature （25℃）, but transforms to layer type Cu3Sn and leaves Kirkendall voids in it at high ambient temperature （120℃）. Under the current density of 5×10^3 A/cm^2 plus room ambient temperature, no obvious directional migration of metal atoms/ions is found. Instead, the thermal stress induced by mismatch of dissimilar materials causes the formation of superficial valley at both interfaces. However, when the ambient temperature increases to 120℃, the mobility of metal atoms/ions is enhanced, and then the grains rotate due to the anisotropic property of β-Sn.展开更多
Laser and hot air reflow soldering of PBGA solder ball was investigated. Experimental results showed that surface quality and shear strength of solder bump reflowed by laser was superior than the solder bump by hot ai...Laser and hot air reflow soldering of PBGA solder ball was investigated. Experimental results showed that surface quality and shear strength of solder bump reflowed by laser was superior than the solder bump by hot air, and the microstructure within the solder bump reflowed by laser was much finer. Analysis on interfacial reaction showed that eutectic solder reacted with Au/Ni/Cu pad shortly after the solder was melted. Interface of solder bump reflowed by laser consists of a continuous AuSn 4 layer and remnant Au element. Needle like AuSn 4 grew sidewise from interface, and then spread out to the entire interface region. A thin layer of Ni 3Sn 4 intermetallic compound was found at the interface of solder bump reflowed by hot air, and AuSn 4 particles distributed within the whole solder bump randomly. The combination effect of the continuous AuSn 4 layer and finer eutectic microstructure contributes to the higher shear strength of solder bump reflowed by laser.展开更多
基金supported by the New Century Talent Support Program, Ministry of Education of China (No.NCET-04-0202)the Beijing Natural Science Foundation Program and Scientific Research Key Program of Beijing Municipal Commission of Education, China (No.KZ200910005004)
文摘The electromigration behavior of eutectic SnAg solder reaction couples was studied at various temperature （25 and 120℃ when the current density was held constant at 104 A/cm^2 or 5×10^3 A/cm^2. Under the current density of 104 A/cm^2, scallop type Cu6Sn5 spalls and migrates towards the direction of electron flow at room ambient temperature （25℃）, but transforms to layer type Cu3Sn and leaves Kirkendall voids in it at high ambient temperature （120℃）. Under the current density of 5×10^3 A/cm^2 plus room ambient temperature, no obvious directional migration of metal atoms/ions is found. Instead, the thermal stress induced by mismatch of dissimilar materials causes the formation of superficial valley at both interfaces. However, when the ambient temperature increases to 120℃, the mobility of metal atoms/ions is enhanced, and then the grains rotate due to the anisotropic property of β-Sn.
文摘Laser and hot air reflow soldering of PBGA solder ball was investigated. Experimental results showed that surface quality and shear strength of solder bump reflowed by laser was superior than the solder bump by hot air, and the microstructure within the solder bump reflowed by laser was much finer. Analysis on interfacial reaction showed that eutectic solder reacted with Au/Ni/Cu pad shortly after the solder was melted. Interface of solder bump reflowed by laser consists of a continuous AuSn 4 layer and remnant Au element. Needle like AuSn 4 grew sidewise from interface, and then spread out to the entire interface region. A thin layer of Ni 3Sn 4 intermetallic compound was found at the interface of solder bump reflowed by hot air, and AuSn 4 particles distributed within the whole solder bump randomly. The combination effect of the continuous AuSn 4 layer and finer eutectic microstructure contributes to the higher shear strength of solder bump reflowed by laser.
