Increasing Value in Lead-Free Soldering with Nitrogen

Many of the lead-free solder pastes on today's market claim either not to require the use of nitrogen inerting or to work equally well in air or nitrogen. There is a fine balance between a lead-free solder paste that performs well in air and one where the flux residue must be removed to avoid corrosion problems. Even the best pastes are close to their operating limit so that a small narrowing of the soldering window results in poor joint quality. One leading Asian consumer electronics manufacturer found that the best performing paste was also expensive. Trials were carried out to see whether the overall cost of the best solder paste reflowed in air would be less than the cheapest paste reflowed in nitrogen while maintaining the highest level of product quality. Commercial boards were reflowed using four different solder pastes in air and nitrogen. The resulting boards were visually inspected for joint quality. The results showed that not only did nitrogen inerting improve the quality of the joints produced by the best paste, but it could bring the cheapest paste up to that standard as well. The overall processing cost of the best paste reflowed in air was higher than that for the lowest cost paste reflowed in nitrogen, maximizing value