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Assembly feasibility and reliability studies of surface mount circuit boards manufactured with lead-free solders

Conference ·
OSTI ID:10160255
 [1]; ; ;  [2]
  1. Sandia National Labs., Albuquerque, NM (United States)
  2. AT and T Technologies Engineering Research Center, Princeton, NJ (United States)
Manufacturing feasibility and reliability evaluations were performed on circuit board test vehicles assembled with the lead-free solders 96.5Sn-3.5Ag (T{sub eut} = 221C) and 58Bi-42Sn (T{sub eut} = 138C). Manufacturability was assessed by defect analysis of the test vehicles. The reliability evaluation was performed by thermal cycling selected test vehicles for 1000, 2500, and 5000 cycles (0C-100C and 30 min cycles); the quantitative and qualitative metrics were solder joint strength and joint microstructure, respectively. Both lead-free solders demonstrated adequate assembly performance. A slightly reduced degree of spreading (wetting) was the predominant defect which was largely attributed to nonoptimized paste components. Fatigue damage in the form of grain boundary and/or phase boundary sliding resulted from thermal cycling of the 96.5Sn-3.5Ag and 58Bi-42Sn solder joints. The damage was distributed primarily in the solder located between the lead or termination and the pad. The absence of well developed cracks allowed the joints to maintain structural integrity, even when fatigue damage was appreciable.
Research Organization:
Sandia National Labs., Albuquerque, NM (United States)
Sponsoring Organization:
USDOE, Washington, DC (United States)
DOE Contract Number:
AC04-94AL85000
OSTI ID:
10160255
Report Number(s):
SAND--94-0140C; CONF-9408109--2; ON: DE94013783; BR: GB0103012
Country of Publication:
United States
Language:
English