14 Dec
2006
14 Dec
'06
11:50 a.m.
On Thu, 14 Dec 2006, Barry Watzman wrote:
Date: Thu, 14 Dec 2006 08:03:53 -0500
From: Barry Watzman <Watzman at neo.rr.com>
Reply-To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
To: cctech at classiccmp.org
Subject: RoHS question
Almost all new equipment has to comply with "RoHS" (Reduction of Hazardous
Substances) requirements, which among other things means it's made with
lead-free solder. Enforcement is stronger in Europe than in the US, but in
any case industry is cleary moving in that direction even when and where not
absolutely required by law.
Question: If one is repairing RoHS compliant equipment, with respect to
functionality only is there a problem with using conventional tin/lead
solder? I'm not asking if it's legal or "environmentally friendly",
I'm
asking if mixing the lead free solder and conventional tin/lead solder will
cause functional problems (for example, any kind of problems similar to
those which we used to see when someone repaired electronic equipment using
plumbing acid flux solder).
Not a good idea to mix solders, If its tin/lead, use tin/lead solder for
repairs, In the RoHS case its trickier because its not so easy to tell which
of the various RoHS compliant solders were used.
Also, if one wants to acquire and use RoHS compliant solder, are there any
changes that someone accustomed to conventional tin/lead solder needs to
make to their soldering technique? And I guess I should also ask the
reverse question from the paragraph above: Are there any issues in using
lead-free RoHS compliant solders on equipment originally built from tin/lead
solder?
Yes, its not a good idea...
The SN/CU/AG RoHS compliant solder I'm used to has a higher melting point, so
its not a good idea to use that for repairs on a SN/PB assembled board
because of possible heat damage. Our RoHS compliant PCB assemblies use a
special FR4 material that will take the higher soldering temperatures of the
SN/CU/AG solder. You always risk PCB damage during a repair, so why increase
the risk?
When hand soldering with the SN/CU/AG solder the noticable differences are the
higher melting point of the solder, slightly lower wetting ability, and
instant freezing. The finished solder joints look grainier (they would look
like colder solder joints if SN/PB solder was used). The finished joints are
quite a bit stronger than SN/PB solderer joints, maybe twice as strong.
Are there any other implications of RoHS that a casual classic computer and
electronics enthusiast should know about, in either direction?
Peter Wallace
Mesa Electronics
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