| July 2006
saw the introduction of the Lead Free directive. Which came into play
under the new
RoHS
Restriction of Hazardous Substances Directive.
Quite where it will all end up is still a big
puzzle some large users are successfully making the change, but it's
anyone's guess as to what we will all end up using. Little doubt
that Lead is hazardous in the wrong places, but questions remain as
to whether circuit boards are the wrong place. Lets hope that its
replacement is less toxic and can be proved to work reliably.
We noticed with great interest that some of
the early companies that changed over to an almost pure tin solder,
have suffered irreparable damage to their plant. It appears that
once stainless steel has lost its protective oxide film, molten tin
readily dissolves it.
As a PCB manufacturer Lead free isn't a big
problem, tin,
gold, silver,
and
OSP finishes all comply. The downside is mainly
on the assembly side, as tin lead HASL finish was a very good
all rounder. It gave boards a good shelf life followed by problem
free assemble and a long joint life for the components. Thick tin
along with silver were rejected years ago because of high risk of
the metal migrating across the circuit board, creating metal shorts.
All that's required is a little moisture combined with electricity
and the fun begins. Thin silver, gold, and tin all have
short shelf lives and quickly become difficult to solder. Most
boards can be stripped and reworked so it's not all bad. Some
excellent photos of tin whiskers and a great deal of detailed
information can be found on the
NASA
web site. 2013 Whiskers are still in the news interesting
article and pdf download on the
electronic design website.
The IPC have a Lead Free Forum that's
starting to get some input, if you are after more information its
well worth a look and can be found at;
www.ipc.org
The UK DTI have now produced a
very informative document can be downloaded from the DTI website.
RoHS_Regs_Draft_Guidance.pdf
The main section of the DTI
website dealing with RoHS Regulations can be found at
Other sites well worth a look at
are;
Wikipedia
If you have any questions please
feel free to consult us on Lead Free issues.
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