The effect of lead content and surface roughness on wetting and spreading of low-lead and no-lead solders on copper-clad FR-4 laminates

Conference · Sat Feb 01 04:00:00 EST 1997

OSTI ID:486010

Stevenson, J O; Roberts, J L; Davidson, R N; Yost, F G; Hosking, F M

Environmental and health concerns pertaining to lead have encouraged research into low-lead alloys for electronic soldering. The development of solder alloys containing lower amounts of lead than Sn/Pb eutectic (37 wt.% lead), but possessing similar properties, is an industry-wide goal. To determine the wettability of low-lead solders, 21 alloys each of Sn/Ag and Sn/Cu eutectic (containing 0 to 10 wt.% lead and/or indium) were tested on as-received copper-clad FR-4. Contact angles for the alloys ranged from 12.5 to 38.9{degrees} and area of spread measurements ranged from 5.2 to 17.3 mm{sup 2} compared with 5 to 150 and {approximately}19 mm{sup 2}, respectively, for Sn/Pb eutectic. Alloys with 8 to 10 wt.% lead showed contact angles and areas of spread similar to Sn/Pb eutectic under similar conditions. The best results on the as-received substrates, compared to the Sn/Pb eutectic, were obtained from the Sn/Ag eutectic with 10 wt.% lead. The very low-lead (less than 10 wt.% lead) and lead-free alloys, however, failed to achieve the performance level of eutectic Sn/Pb solders. A desire to improve the spreading of very low-lead and lead-free solders provided the impetus for these efforts to produce {open_quotes}engineered{close_quotes} rough surfaces. In an attempt to improve the wettability and spreading behavior of very low-lead and lead-free alloys, the very low-lead and lead-free members of the Sn/Ag system were tested on roughened copper-clad FR-4. Every alloy in the test suite demonstrated improvement in area of spread on the roughened substrates. The best results on the roughened substrates, compared to the Sn/Pb eutectic, were obtained from the Sn/Ag eutectic with 8 wt.% lead. The effects of surface roughness on the wettability and flow behavior of solder alloys has provided insight into surface morphologies that lead to improved solderability.

• Research Organization: Sandia National Labs., Albuquerque, NM (United States)
• Sponsoring Organization: USDOE Office of Financial Management and Controller, Washington, DC (United States)
• DOE Contract Number: AC04-94AL85000
• OSTI ID: 486010
• Report Number(s): SAND--97-0275C; CONF-970616--1; ON: DE97003009; CRN: C/SNL--SC9101030B
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
54 ENVIRONMENTAL SCIENCES
COPPER
EUTECTICS
LEAD
MITIGATION
PARAMETRIC ANALYSIS
PRINTED CIRCUITS
ROUGHNESS
SOLDERING
SURFACE FINISHING