Agreed. If Nickel from ENIG (possibly the most popular le
Inge
Agreed. If Nickel from ENIG (possibly the most popular lead-free PCB
finish now?) is OK at the component-PCB interface then why are we so
fussy about nickel content in the bulk of the solder joint
Anecdotal evidence that increased nickel content in lead-free baths is
common
Nigel
-----Original Message-----
From: Hernefjord Ingemar [mailto:[log in to unmask]]
Sent: 11 June 2007 12:11
To: TechNet E-Mail Forum; Burtt, Nigel
Subject: RE: [TN] Nickel content in solder
Nigel,
this 0.01 % level is strange. When you solder, you solder on pure Nickel
(e.g. ENIG). The nickel plated pad becomes part of the solder (a IMC).
Now, let's put a nickel ball representing 0.1% of the solder weight into
the solder. And we heat the solder the usual way to solder on a ENIG
board. Will the little nickel ball poison the solder joint? Probably
not. A Sn/Ni intermetalic will grow around the ball, but that won't be
detrimental to the solder joint. Ten little nickel balls, together
representing 0.1% of the solder weight, will that be detrimental? I
guess not. And so on. I have seen large nickel flakes loosen from
(bad)nickel plating and be mixed with the solder and nothing has
happend, at least not in a global solder joint perspective. In analogue
with the said, I can't see why 0.01% or 0.1% makes any difference.
Likewise, if 1 out of 1,000 spheres in the solder paste is Nickel, I
doubt that will matter. Finally, if we anticipate that ALL solder
spheres have 1/1000 of the sphere volume filled with Nickel, will that
be detrimental? Hardly. This is the practical view of things, a
morphologist and/or a metalurgist may have a different view. If you got
a pot of research money, you'll probably find something. Will be
interesting to see what the heavy metal gnus say...
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of N Burtt
Sent: den 11 juni 2007 12:19
To: [log in to unmask]
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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