"WangoTango" wrote in message
k.net...
In article ,
says...

Aside from silver plated or specialty parts in an old scope, is there any
harm done
in using real solder in a RoHS device?

Here's an example.

a resistor mounted through-hole has a bad joint. Normal repair just
reheat the joint
and add more solder. No problem.

I've reworked a thousand "RoHS" boards with good 'ol 60/40 and have
never had a failure of one of MY joints, or any problems related to
them. The stupid part of all of this is, just how are you going to know
EXACTLY which lead free solder was used to begin with? There a a lot of
formulations, from good 'ol SAC (Tin, silver, copper) to a bunch of
alloys with all kinds of weird stuff in them. So, if you grab a spool
of SAC and the OEM used a bismuth or zinc alloy, what is going to
happen? I just clean up as much of the original solder as possible with
solder wick and put down 60/40 and forget about it. I might also add,
that we have mixed RoHS and non-RoHS parts for years with no failures
due to the tin/lead solder. In fact UPS has destroyed more boards by
running them over than any other failure mechanism.


In general, based on practical experience, I think I would agree with you. I
have also reworked joints on boards that were built with lead-free, but not
subject to the European regs, with regular 60/40 lead solder, and I have
never knowingly had a problem - at least short term. But who's to say what
the long-term effects may be? I mentioned in my original reply about the
'metalurgical wisdom' in this regard. I got this direct from conversations
with a Dr Paul somebody-or-other who is an expert in the field and head of
the subject for a UK consultancy firm, when I was researching for an article
that I was writing on the subject, for a UK trade magazine. He had produced
a paper which was available on the 'net, and he was quite adamant that the
two solder types should not be mixed in the same joint, because of long term
degradation of the integrity of the joint. I've no idea whether this belief
was theoretical or based on experimentation, as I did not ask the question.
That sort of depth was beyond the scope of the article.

On balance, I still feel that the right *overall* practice, is to rework
joints with the same basic formulation as they were made with. Obviously,
it's not going to be a major problem if a reworked joint in a TV set or
whatever, fails down the line because of it having been reworked with the
wrong solder type, but I would hate to think that some item that I had
repaired finished up in a critical application, and later failed because of
me. Remember also, that most of us outside of the USA are in a slightly
different position from you folks in that we must not, officially under
threat of law, do anything to compromise the RoHS certification of a
product. That includes using non RoHS compliant replacement parts, and
solder to fix them in with ... :-\

Arfa