Mechanical and Thermal Fatigue Property of Sn Base Solder Alloys.

Mechanical Strength and Microstructure of BGA Joints Using Lead-Free Solders

“…However, the average thickness of the (Cu, Ni) 6 Sn 5 layer did not exceed 0.6 µm. This is why the Cu content was insufficient for formation of a (Cu, Ni) 6 Sn 5 layer. The average thickness of the P-enriched Ni-P layer did not exceed 120 nm.…”

“…A compositional analysis by WDX showed the η layer to be composed of (Cu 1−x , Ni x ) 6 Sn 5 by substitution of Ni atoms for a proportion of the Cu atoms. In this experiment, the η layer was identified as (Cu 1−0.33 , Ni 0.33 ) 6 Sn 5 , but Kariya et al have reported the η phase to exist over a wide range, with Ni substituted for Cu by 50 at% or more.…”

“…A compositional analysis by WDX showed the η layer to be composed of (Cu 1−x , Ni x ) 6 Sn 5 by substitution of Ni atoms for a proportion of the Cu atoms. In this experiment, the η layer was identified as (Cu 1−0.33 , Ni 0.33 ) 6 Sn 5 , but Kariya et al have reported the η phase to exist over a wide range, with Ni substituted for Cu by 50 at% or more. 10) Although Sn-Ag-Cu solder contains no more than 0.75 mass% of Cu, the addition of Cu to the solder was effective in changing the reaction layer from a NiSn-based intermetallic compound to a Cu-Sn-based version.…”

“…For the Cu-containing Sn-Ag-Cu solder, a block-shaped (Cu, Ni) 6 Sn 5 layer and a P-enriched Ni-P layer were formed on the boundary between solder and pads. However, the average thickness of the (Cu, Ni) 6 Sn 5 layer did not exceed 0.6 µm.…”

“…After extensive studies, Sn-Ag eutectic alloy-based solders, which have superior mechanical properties, have come to the fore. [5][6][7] Since most Pb-free solders have higher melting temperatures than conventional solder, the control of interfacial behavior, including the chemical reactions that take place between solder and pads, is now a focus of research interest. 8) * Graduate Student, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan.…”