An evaluation of prototype surface mount circuit boards assembled with three non-lead bearing solders

Conference · Sat Jul 01 04:00:00 EDT 1995

OSTI ID:97035

Vianco, P T ^[1]; May, C ^[2]

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1. Sandia National Labs., Albuquerque, NM (United States)
2. Lockheed Martin Specialty Components, Inc., Largo, FL (United States)

Prototype circuit board test vehicles wee assembled with three candidate lead-free solders: 96.5Sn-3.5Ag (wt %), 58Bi-42Sn, and 91.84Sn-3.33 Ag 83Bi., using a forced-convection/infrared furnace and RMA flux based pastes. Wettability of circuit board features and packages was best with Sn-Ag-Bi alloy followed in order by Bi-Sn and Sn-Ag solders. The Sn-Ag-Bi solder had a greater propensity for void formation in the joints. The reliability assessment was based upon solder joint microstructure and the shear strength of selected leadless packages. Solder joint damage was of a greater extent after thermal shock exposures rather than thermal cycling. The Sn-Ag-Bi alloy on the largest package appeared most susceptible to thermal shock. Test vehicle performance clearly demonstrated that, with the non-lead solders, local thermal expansion mismatch can be as detrimental to joint integrity as the traditional global mismatch damage.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 97035
• Report Number(s): SAND--95-1367C; CONF-9508140--3; ON: DE95014889
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
42 ENGINEERING
BISMUTH ALLOYS
BISMUTH BASE ALLOYS
ELECTRONIC CIRCUITS
LEAD
MATERIAL SUBSTITUTION
MATERIALS TESTING
METALLURGICAL FLUX
PHYSICAL PROPERTIES
SILVER ALLOYS
SOLDERING
THERMAL EXPANSION
THERMAL SHOCK
TIN BASE ALLOYS
WETTABILITY