When you say plain old FR4- what is the Tg of the FR4. You may be using a
140 Tg. I would for one recommend going to a 170 Tg at minimal. Also-what is
the finish(SMOBC etc.)

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Croslin, Robert
Sent: Tuesday, September 18, 2007 1:59 PM
To: [log in to unmask]
Subject: [TN] Trace Peel on FR4

Dear 'Netters,

We have a product used to measure on/off status on flat screen TV's that was
designed a few years ago.  Over time, with the newer, bigger TV's, there is
a much higher current draw than we'd envisioned way back when.  So, as the
devices cycle back through our repair depot, we're making mods to upgrade
them to handle these new TV's.  A problem we've seen in testing is that the
traces that handle the AC pass-through are now getting quite warm.  We've
measured the traces at 105*C at room temperature.  The base is plain old
FR4.  We haven't been able to get any to fail in testing, but are concerned
about the differential under load possibly causing the trace to peel away
from the FR4.  Our concern is thermal cycling over time; could it cause the
trace to lift?  If the trace is hot but the board cool in a steady state
condition, is there any risk there?

Does anyone know of any specifications that would address this situation?

Bob Croslin
Nielsen Media Research



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