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Date: | Wed, 27 Sep 95 15:32:17 PDT |
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To someone familiar with PTFE Microwave Application PWB's:
We are looking at some very small pits (1-5 microinches) located
sporadically on conductor traces. The pits were obviously created by
some minute contamination on the plated copper surface which left small
voids in the tin-lead electroplate. In most cases, copper is exposed
at the bottom of the pit. The etching process may have attacked the
copper to varying degrees but we are unable to determine the depth of
these pits into the copper conductor.
Specifications allow +/- 10% conductor width variation. Nominal
conductor widths are .088" on traces that exhibit these pits. I mention
this fact as it relates to controlled impedance. The amount of copper
loss due to the pitting condition could in no way add up the amount
allowed by this specification (10% .088 = .0088 x conductor length) when
on the low side of the tolerance.
What effect will these pits have on performance and long term
reliability?
Will it create difficulties in 'tuning' the board for it's end use
application?
Will the small amount of exposed copper pose any long term reliability
problems?
In advance, Thanks
Ralph Malloch - Process Enginnering
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