Have you heard of component terminations made of “pure iron”?  Not an alloy.  Any concerns that I should know about?  Seems like the CTE is low, although not as low as alloy 42.  These are plated with copper then Sn5Bi.  Rather odd...

Comments from our materials engineer:
Per existing guidelines, Alloy 42 is a high risk in SMT because of CTE mismatches with Sn.
CTE of pure Fe is 11.7 ppm/C
CTE of Cu or alloys ranges from 16.2 to 17.8 ppm/C
CTE of Sn is  23.5 ppm/C
CTE of pure Alloy 42  is  4.6 ppm/C