Hi Dave,
it's still hard to believe that Nickel plays a important role talking
metal dissolution in solder. Is there such a big difference between 60Sn
and SAC? If we start with 60Sn:
220 Centigrades
Au dissolves with 4 um/second, Ag with 1 um/second, Cu with 0.01
um/second, Pt and Ni not measureable,
300 Centigrades
Au dissolves with >>10um/second, Ag with 7 um/second, Cu with 0.5
um/second, Pt and Ni still not measureable.
400 Centigrades
Au dissolves with >>10um/second, Ag with >>10 um/second, Cu with
4um/second, Pt and Ni with 0.1um/second
500 Centigrades
Au dissolves with >>10um/second, Ag with >>10um/second, Cu with
>10um/second, Pt and Ni with 0.2um/second
What would be the corresponding numbers for SAC with its higher Tin
content?
Furthermore, IF the SAC dissolves Ni at a higher speed than 60Sn, won't
there be more Sn/Ni intermetallics, and also a stronger solder joint?
Or, will the higher Ni dissolution be neglectable for what you solder
mount (short time), and ONLY have a negative effect on the solder pots
(long time)?
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: den 11 juni 2007 15:25
To: [log in to unmask]
Subject: Re: [TN] Nickel content in solder
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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N Burtt <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
06/11/2007 05:19 AM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to N Burtt
<[log in to unmask]>
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Subject
[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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