Microstructural characterization of tin lead and lead free solder joint interface

Interface of Cu-(Sn37Pb) and Cu-(Sn3.5Ag0.5Cu) soldered joints has been characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) fitted with EDX. TEM analysis. The presence of different intermetallic compounds (IMCs) in the interface, such as (Cu 6 Sn 5 ), (Cu 3 Sn) and Ag 3 Sn phases have been confirmed. Microstructural observations are correlated with the electrical and mechanical properties of the joints. (Lead free solder)-Cu joint exhibits better electrical conductivity (0.28x10 6 ohm-1 cm-1) and mechanical strength ~68MPa compare to the conventional (lead-tin solder)-Cu joint which exhibits electrical conductivity and mechanical strength as 0.22x10 6 ohm-1cm-1 and ~55MPa respectively

Comparative study of tin lead and lead free solder joint interface

Pure Cu-(Sn37Pb) and Cu-(Sn3.5Ag0.5Cu) soldered interface has been characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) fitted with EDX. TEM analysis of the interface confirms the presence of different intermetallic compounds (IMCs) in the interface, such as (Cu 6 Sn 5 ), (Cu 3 Sn) and Ag 3 Sn phases. Microstructural observations are correlated with the electrical and mechanical properties of the joints. (Lead free solder)-Cu joint exhibits better electrical conductivity (0.28x10 6 ohm-1cm-1) and mechanical strength ~68MPa compare to the conventional (lead-tin solder)-Cu joint which exhibits electrical conductivity and mechanical strength as 0.22x10 6 ohm-1cm-1 and ~55MPa respectively

A comparative study on the ageing behaviour of solder alloy-cu joint assemly using lead free solder and Sn-Pb eutectic solder alloy

In the present investigation, Sn-Ag-In ternary alloy was used to join Cu substrate (SAI-Cu) and compared with conventional Sn-Pb eutectic solder alloy–Cu assembly (SP-Cu). The melting point of the alloys was found to be 192±1 o C and 184±2 o C respectively. The re-flowing was carried out above +30 o C of the melting point of the respective alloys for 30secs. Both the joints were aged at 100 o C for 50-200hrs at a step of 50hrs. Subsequently, structural characterization and mechanical property evaluation of the joints were performed. In re-flowed condition, the shear strength of the SAI-Cu joint (~64MPa) is higher than SP-Cu joint (~55MPa). The diffusion zone of the former is decorated with Cu 6 Sn 5 intermetallic phase, whereas the latter contains both Cu 6 Sn 5 and Cu 3 Sn. The width of the reaction zone is more in case of SP-Cu joint with respect to SAI-Cu joint. Isothermal aging of the solder assembly leads to deterioration of joint shear strength accompanied by structural change in the diffusion zone. After 200hrs of aging the shear strength of SAI-Cu joint is ~44.6MPa and the same becomes ~34.5MPa for SP-Cu joint. In both the cases, formation of Cu 6 Sn 5 and Cu 3 Sn has been observed which causes lowering of bond strength. Indium plays a vital role in controlling the chemical reaction at the interface during reflowing and ageing. Hence, it is responsible for betterment in mechanical properties