6 Jul
2007
6 Jul
'07
9:19 p.m.
David Griffith wrote:
I haven't heard anyone discuss this yet: what
causes traces on some old
PCBs to wrinkle and not others? My guess is a combination of suboptimal
glue and wide temperature swings.
From what I've seen, this is caused by the copper
and the base material
expanding and shrinking at different rates. It is seen quite a
bit where
temperature ranges between extremes, especially with cheap and older stuff.
I'm told this is one big reason why PCB's were not accepted for military and
space-grade stuff for quite some time before they managed to more closely match
materials' thermal expansion coefficients.
It happens to most every PCB subject to temperature cycling. This is also why
it's so easy sometimes to lift a trace when soldering.
I think this is mentioned in some writeup about the factors to consider when
purchasing PCB stock.
--
jd
Pascal, n.:
A programming language named after a man who would turn over in
his grave if he knew about it.