[Orcnet] Interesting articles on risks of removing lead from solders

[Pete Perkins]

Keith, et al,

    Welcome to the 21st century.  It's quite clear that we used the last
half of the 20th century to learn how to make reliable circuit especially on
circuit boards.  The issue of tin whiskers has been an ongoing issue in all
of this.  

    This issue has been a hobby-horse of mine ever since the RoHS issue
was raised.  The greenies are out to destroy business and drive us back into
the dark ages as technology is removed from modern culture.  I guess we can
learn to plant flowers in all the old, rusting auto hulks that will be
abandoned everywhere when the complete collapse of civilization occurs.
Perhaps we can throw I-pods at one another in protective moves.  Maybe they
think that it is good that we be driven back into a tribal, agricultural
society - fighting off our immediate neighbors who want to keep from
starving, etc.  

    The attached article shows a good example and let's us know that
there are folks out there who have been fighting this for a long time and
still are working on it.  This issue has been on ongoing discussion item for
folks who do insulation systems - especially circuit boards.  Remember, a
circuit board is a thixotropic plating tank and it is only a matter of time
for there to be plating trees growing from power to ground.  Key technical
parameter is the electric field across the plating medium - which seems to
grow as folks work to reduce the material and spacing between layers.  This
is all so fundamental and ignores manufacturing variabilities (prepreg
tolerances and thickness fluctuations) and flat out misteaks (inadequate
uniform penetration of epoxy thruout the layer or voids and bubbles within
the layer - which exacerbate the electric field in the wrong direction).  

    None of my diatribe touches on the increased solder temperatures
required in manufacturing (which increases thermal stress on all the parts
in the assembly and reduces reliability - ask how much? Unk).  Nor does it
cover the oft mentioned reduced mechanical strength of solder joints which
result in cracked solder joints leading to unreliable operation and
premature failure.  

    So the fun increases for us technical types.  

    So, sharpen your technical pencil and take good training notes to
apply to your designs to keep out of trouble. 

:>)     br,     Pete
 
Peter E Perkins,
PO Box 23427
Tigard, ORe  97281-3427
 
503/452-1201     fone/fax
p.perkins at ieee.org
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