Kinetics of the wetting of tin on air-passivated copper in the absence of a fluxing agent
A specially designed ultrahigh vacuum in situ surface analysis and wetting system has been constructed to study the spreading of liquid metal solders on carefully prepared and well-characterized solid substrates. Initial studies have been completed for the spreading of pure tin solder on copper substrates in the absence of any fluxing agent. Surface chemical analysis by x-ray photoelectron spectroscopy showed the air-exposed surface to consisted of about 3 nm of Cu{sub 2}O, while the as-received surface consisted of about 8 nm of Cu{sub 2}O. The sputter-cleaned surface contained less than one monolayer (0.3 nm) of Cu{sub 2}O. Sample surfaces were prepared and spreading experiments performed without intermediate exposure of the surfaces to contaminating atmospheres. Solder spreading was performed under 50 torr of highly purified helium gas to allow for adequate thermal coupling between the solder and the substrate. Spreading experiments utilizing a linear temperature ramp show that pure tin solder spreads readily on oxidized copper surfaces at elevated temperatures. The initiation temperature for rapid tin spreading on the as-received copper surface was 325{degrees}C, similar to the temperature where isothermal spreading changes activation energy or rate. Decreasing the thickness of the oxide on the surface lowered the observed temperature for the initiation of spreading and increased the rate of spreading. On the sputter-cleaned copper surface, rapid solder spreading was observed immediately upon melting of the solder.
- Research Organization:
- Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 10196608
- Report Number(s):
- SAND-94-0587; ON: DE95003810; CRN: C/SNL--SC9101030B; TRN: 94:010739
- Resource Relation:
- Other Information: PBD: Oct 1994
- Country of Publication:
- United States
- Language:
- English
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