Soldering considerations for lead‐free printed circuit board assembly – an Envirowise Guide

To give an overview of the issues encountered, and changes that need to be made in the various types of soldering process when converting them from conventional to lead‐free assembly.

This paper has been written to provide a review of the lead‐free reflow, wave and hand soldering processes. Problem areas highlighted and methods for adjusting and optimising each type of soldering process for compatibility with lead‐free solders are described.

The move to lead‐free soldering in electronics assembly can lead to a number of issues that affect process performance, yields and reliability. Problems that are sometimes encountered with conventional lead‐bearing solders can exacerbated when moving to lead‐free. Many of the issues are associated with the higher melting points of the recommended lead‐free solders. Fortunately, these issues are now well known and, with care and attention to process optimisation, they can largely be avoided.

The value of the paper lies in its ability to provide information on the types of problems and issues encountered when moving to lead‐free solders and the advice it gives on how to avoid them. It also describes how to convert the various lead‐free soldering processes used in PCB assembly using a range of measures that can minimise defects, avoid common problems and optimise yields. Sources of additional assistance are also identified.