Hi Ofer,
Without knowing which LF-solder you talk about, no specific advise can be 
given. Coatings themselves are not a real problem.
However, when LF-solders will be used and most LF-solders in the running 
require 35 to 40°C higher refllow temperatures--or reductions in belt speeds; 
thus, yes you need to think about process changes. Workmanship is about the same/ 
reliability effects have not fully determined--and will not be for some time 
to come.
You may be interested in the upcoming conference IPC/Soldertec Global 
Conference on Lead Free Electronics in Brussels on June 10 and my workshop 
Reliability Issues for Lead-Free Soldering.

Regards,
Werner Engelmaier

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