Can I solder reliably leaded terminations with lead-free solders in an SMT process?
The amount of lead on SMD terminations can be small often component manufacturers will use 10/90 or 15/85 for the tinning. A small amount of lead will be introduced into the lead-free joint and for small amounts of lead under 2% by weight this doesn’t impact the pull and shear force results when tested. Some assemblers have used a mixed bag of leaded and unleaded SMD’s with no impact to product reliability. Most are in consumer electronics. For the highest reliability a complete lead-free system is preferred. If leaded SMD components must be used, it is recommended to access product reliability and therefore some testing may be required. An important note to that for RoHS compliancy lead must be kept below 0.1% in the joint also, lead in terminations may impact this negatively.
