Prototype circuit boards assembled with non-lead bearing solders

Conference · Wed Apr 01 04:00:00 EST 1998

OSTI ID:650371

Vianco, P T; Rejent, J A

The 91.84Sn-3.33Ag-4.83Bi and 96.5Sn-3.5Ag Pb-free solders were evaluated for surface mount circuit board interconnects. The 63Sn-37Pb solder provided the baseline data. All three solders exhibited suitable manufacturability per a defect analyses of circuit board test vehicles. Thermal cycling had no significant effect on the 91.84Sn-3.33Ag-4.83Bi solder joints. Some degradation in the form of grain boundary sliding was observed in 96.5Sn-3.5Ag and 63Sn-37Pb solder joints. The quality of the solder joint microstructures showed a slight degree of degradation under thermal shock exposure for all of the solders tested. Trends in the solder joint shear strengths could be traced to the presence of Pd in the solder, the source of which was the Pd/Ni finish on the circuit board conductor features. The higher, intrinsic strengths of the Pb-free solders encouraged the failure path to be located in proximity to the solder/substrate interface where Pd combined with Sn to form brittle PdSn{sub 4} particles, resulting in reduced shear strengths.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 650371
• Report Number(s): SAND--98-0827C; CONF-980716--; ON: DE98005041; BR: DP0401017
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
42 ENGINEERING
BISMUTH ALLOYS
BRAZING ALLOYS
ELECTRONIC CIRCUITS
MATERIAL SUBSTITUTION
MICROSTRUCTURE
SHEAR PROPERTIES
SILVER ALLOYS
SOLDERED JOINTS
THERMAL CYCLING
TIN BASE ALLOYS