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Tue, 28 Aug 2007 16:28:22 EDT |
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In a message dated 8/28/2007 3:23:54 P.M. Eastern Daylight Time,
[log in to unmask] writes:
As in
the case of Paul's response below, this would also probably cause the
pad adhesive to weaken.
Please remember that there is no "pad adhesive" on rigid boards. That was
the old construction on flex, and now a lot of flex is "adhesiveless". The
bond of copper pads/traces to the rest of the board is physical - foil
roughened on one side at the time of manufacture. And now, with the emphasis on high
speed signal traces and "low profile foils" - there isn't much "tooth" left
for the curing epoxy to physically attach to. Take it easy with heated
irons.
My votes in order are:
1. laser ablation - can be run off the CAD program for trace areas and only
focused on copper.
2. abrasive removal - less selective than laser, but should not damage epoxy
of board
3. heat of any sort
4. chemical - remember epoxy is almost always one of the polymers in the
mask. What is the board made of - epoxy!!. It is a very tight chemical
tightrope to chemically attack mask without some attack on the board epoxy.
Denny Fritz
MacDermid
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