Use of Pb-free Components

We have talked about this previously on SMTnet. For instance, check this thread, while you wait for others to respond : http://www.smtnet.com/forums/Index.cfm?CFApp=1&Message_ID=25394

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Before "Pb-Free" became an issue we were and still are using Pb-Free component lead finishes- such as on many TSOP, SSOP and QFP packages as well as caps. Components manufacturers changing the lead finish to no-Pb tend to ensure solderability with Sn/Pb alloys since that's what 99.999999% of their customer are using to solder. However, you may see some soldering issues. Its best to notify your component suppliers to advise of any lead finish changes. Many component guys are changing the finish and keeping the p/n the same and not notifiying customers. Where you will see issues is in wetting. Its best to ensure your temp profiles are well within the process window of the paste spec. Peak temp and time-over-liquidous have the greatest impact. No-Pb is making us look at profiles more carefully, which is a good thing, and helping justification for thermal profiling instruments such as the ECD M.O.L.E. and KIC.

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This is the dilema during this transition period.

Here is a tip: If you see typcial solder joints on a lead free process, but only on one component type....it probably has a significant quantity of lead in it (ex. Sn90/Pb10...and so on)

If using Tin / Bismuth solder alloys your single largest threat is lead. Tin/bismuth/lead alloy / intermetallics can liquodus at 93 Celsius!!!

Other issues involving lead are lead enrichment areas of solder joints. Pad-lift and poor shear strength are well documented defects.

Also, lets not forget lead contamination in your solder pot.

Oh and for the record, lead free soldering is not new. It has been used for well over 40 years in electronics.

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