Pb-Free Wave Soldering Project

Chair:  Denis Barbini (Vitronics Soltec)

The use of Pb-free solder alloys introduces concerns regarding process changes and solder joint reliability.  While previous iNEMI projects focused on Pb-free joints soldered by the use of forced convection reflow ovens, there was little industry information about the impact of Pb-free implementation on the wave soldering process or the reliability of Pb-free wave soldered joints and component survivability.

Building on the work of the iNEMI Lead-Free Assembly & Rework Project, this project was organized to investigate use of the iNEMI-recommended Pb-free alloy for wave soldering, characterizing the impact of Pb-free alloys on wave and/or selective soldering processes.

Phase I of the project was completed in early 2007 and provided insight into the process issues encountered with Pb-free wave soldering so that a rational implementation strategy for a robust lead-free process can be achieved. The first phase focused on three critical areas:

• Materials selection - fluxes, alloys, components, and board complexity.
• Process optimization - defined "window of opportunity" based on flux amount, preheat temperature, contact time, solder temperature, wave configuration, and atmosphere.
• Solder joint yield - defined failure levels and defect types using IPC Class 3 inspection criteria combined with best practices. Yield was determined by hole-fill characterization using 5DX data analysis.