Hi Nigel! The maximum nickel content in solder alloys as a contaminate is 
based on a number of investigative studies from the 1960's. Klein Wassink, 
C.J. Thawaites and a number of other investigators established the maximum 
limits for a number of elements after a series of tests over several 
years. Those maximum levels have been stable and served the industry well. 
The introduction of Pbfree solders has caused some concerns. The higher 
tin content of the popular SAC solder alloys results in an 
erosion/dissolution attack of the traditional ferrous materials that 
comprise the standard solder pot and solder iron tips. Some folks have 
"discovered" this attack on stainless steel hardware when the nickel 
content of their solder pot analysis increased.  The use of protective 
coatings or the use of titanium eliminates the erosion/dissolution issue. 
Additionally, a number of solder alloy suppliers have been investigating 
the use of  tin/copper solder alloys with minor element modifications 
(nickel being one of the elements being heavily investigated). The 
JSTD-006 is also looking at the issue - some of the minor element 
modifications are at levels below the JSTD-006 standard composition 
tolerance limits (as you described) which has caused some confusion. The 
bottom line is that for our current level of understanding, the historical 
maximum nickel contaminate values are adequate and more information will 
be gathered as we gain more experience with Pbfree soldering. Hope this 
helps. 

Dave Hillman
Rockwell Collins
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[TN] Nickel content in solder






To all the metallurgy-minded readers.

The old standard for Sn60Pb40 and similar solder baths (J-STD-001?) gave 
max Nickel as 0.01%, but I have failed to find any definitive evidence of 
the 
negative effect on solder joints that leads to this figure. An older 
reference 
said that upto 0.1% was OK and gave various possible problems it might 
cause 
but claimed most of these were based on disputed evidence.

Apparently for SAC305 and similar SAC alloys, J-STD-006 also specs the 
same 
0.01% max level of Nickel, but again I don't know what detrimental effect 
this 
would have, given one popular SnCu alternate alloy actually includes about 

0.05% Nickel as a deliberate and beneficial additive.

Its apparent that the high tin content lead-free alloys are quite good at 
pulling 
some nickel content out of stainless steel, even when components in 
contact 
with the moving molten metal are treated to increase resistance to 
erosion.

Can anyone enlighten me further?

Thanks

Nigel

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