Solder eases switch to lead-free processing

Soldering & Surface Mount Technology

ISSN: 0954-0911

Article publication date: 1 December 2004




(2004), "Solder eases switch to lead-free processing", Soldering & Surface Mount Technology, Vol. 16 No. 3.



Emerald Group Publishing Limited

Copyright © 2004, Emerald Group Publishing Limited

Solder eases switch to lead-free processing

Solder eases switch to lead-free processing

Keywords: Lead-free soldering

BLT Circuit Services reports considerable success during recent extended trials with its SAC lead-free low-cost solder called LFB/227S.

While testing with a large UK wave soldering machine manufacturer, this nonpatented solder produced excellent results on a variety of PCBs. BLT believes that this would be a sensible choice of lead-free alloy for most users and could be a good contender as a drop in replacement against the standard 63/37 alloys currently used, while enjoying significant savings against other patented lead-free SAC alloys.

Manufactured in house using nitrogen casting techniques, the alloy has special dross-inhibiting properties and flows similarly to higher-silver-content SAC alloys, while producing little dross and using conventional wave soldering techniques with no need for an inert nitrogen atmosphere around the pot or preheat stages. In tests, the alloy, which is based on Sn/Ag/Cu/P, ran at only 10°C hotter than normal leaded solder (260C), and produced very good results with industry-standard alcohol and VOC-free fluxes. Subsequently, for most BLT users there will be no need to change flux formulations, which will be one less process concern.

With considerably less silver content it is expected the savings to be made compared to normal SAC alloys will be in the region of 30 per cent or more, while offering similar wetting speeds and a saving on dross scrap compared with other Sn/Cu alloys. The alloy produced significantly improved solder wetting and flow characteristics compared against tin/copper formulations and is very tolerant to both silver and copper contamination, with a need to make simple additions to the alloy with a special stabilising metal once levels of copper exceed predetermined limits. Regular solder analysis is recommended to ensure the stability and mix of LFB/227S, which is carried out in the BLT laboratory.

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