The interactions of lead (Pb) in lead free solder (Sn/Ag/Cu) system

The solder interaction of Pb within the Sn/Ag/Cu system was characterized using Differential Scanning Calorimetry (DSC). Components were then assembled with the Pb-free solder. Cross-sectioning and fine polishing were performed on the solder joints at the as-soldered stage and after temperature cycl...

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Bibliographic Details
Main Authors: Key Chung, C., Aspandiar, R., Foo Leong, K., Cheng Siew Tay
Format: Conference Proceeding
Language:English
Subjects:
Applied sciences
Assembly
Calorimetry
Design. Technologies. Operation analysis. Testing
Electronics
Environmentally friendly manufacturing techniques
Exact sciences and technology
Integrated circuits
Lead
Microstructure
Needles
Reflow soldering
Scanning electron microscopy
Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices
Temperature
Testing, measurement, noise and reliability
Tin
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Summary:The solder interaction of Pb within the Sn/Ag/Cu system was characterized using Differential Scanning Calorimetry (DSC). Components were then assembled with the Pb-free solder. Cross-sectioning and fine polishing were performed on the solder joints at the as-soldered stage and after temperature cycle readouts at 250, 500, 750, and 1000 cycles. The microstructure of the solder joints was examined using Scanning Electron Microscopy (SEM), and solder elements were mapped and identified by Energy-Dispersive X-ray (EDX) analysis. DSC detected Pb reaction with Sn/Ag at 179/spl deg/C and ternary compound formation. SEM/EDX found that Pb diffused into the Sn/Ag/Cu matrix during reflow soldering to form different microstructures, namely CuSn, SnAg, SnPbAg, and Pb-rich phases. The SnAg structure was found as a rod/needle morphology that was detrimental to solder joint reliability. During temperature cycling, this structure loosened its embedding effects due to grain-boundary sliding in the solder matrix, which accelerated solder fatigue crack propagation. Solutions to this problem are discussed.
ISSN:0569-5503
2377-5726
DOI:10.1109/ECTC.2002.1008091