Lead-free solders for electronics applications: Wetting analysis
The fabrication of electronic systems has relied upon eutectic tin-lead solder for the attachment of components to printed wiring boards. Higher service temperatures are approaching the durability limits of the eutectic solder. The tin-rich, lead-free solders are being actively studied as alternate alloys. Experiments that examined the wettability of 95Sn-5Sb (wt %), 95.5Sn-4.0Cu-0.5Ag, 96.5Sn-3.5Ag, and the control solder, 60Sn-40Pb, on oxygen-free, high conductivity copper were performed. A rosin-based, mildly activated (RMA) flux and three water soluble, organic acid fluxes were used in the wetting balance/meniscometer measurements. The 95.5Sn-4.0Cu-0.5Ag and 95Sn- 5Sb alloys exhibited good wetting, with contact angles of 35{degree} < {theta}{sub c} < 55{degree} as compared to the excellent performance of the 60Sn-40Pb material (20{degree} < {theta}{sub c} < 35{degree}). The fair wettability observed with the 96.5Sn-3.5Ag solder (60{degree} < {theta}{sub c} < 75{degree}) was due in large part to the inability of the fluxes to significantly lower the solder-flux interfacial tension. The wetting rates of the 95.5Sn-4.0Cu-0.5Ag and 95Sn-5Sb solders were comparable to those of the control; the 96. 5Sn-3.5Ag alloy wetting rate was slower than the other candidates. The solder film formed on the substrate surface by the 95.5Sn-4.0Cu-0. 5Ag alloy was very grainy. The water soluble fluxes exhibited a larger degree of residue formation than did the RMA flux. 8 refs., 12 figs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 5494227
- Report Number(s):
- SAND-91-0031C; CONF-9108110-1; ON: DE91014900
- Resource Relation:
- Conference: 4. Electronic materials processing congress, Montreal (Canada), 19-23 Aug 1991
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
ANTIMONY ALLOYS
WETTABILITY
COPPER ALLOYS
LEAD ALLOYS
TIN BASE ALLOYS
ELECTRONIC EQUIPMENT
OPTICAL MICROSCOPY
SOLDERED JOINTS
ALLOYS
EQUIPMENT
JOINTS
MICROSCOPY
TIN ALLOYS
360101* - Metals & Alloys- Preparation & Fabrication
426000 - Engineering- Components
Electron Devices & Circuits- (1990-)