Ed, you will find that Teflon/PTFE laminates do not process at all like FR-4
materials when it comes to desmear and electroless/metallization.  As you
have already seen, one response has mentioned Tetra-Etch and
SHADOW.  Tetra-Etch, a sodium napthalene material (same as mothballs)
works quite well, but has a very limited shelf life and must be stored in a
freezer.  I have used a material called POLY-ETCH W from Matheson Gas
Products @ 61 Grove Street,  Gloucester, Mass.  Sorry, I don't have the
phone number, but the company headquarters is at 201/867-4100.  This is
also a napthalene solution; in all cases, the PTFE re-passivates very
quickly so the panels must be "activated" with the napthalene and rinsed
with either acetone or isopropyl alcohol and processed through
electroless copper very quickly - within an hour or so.

I have recently left Electrochemicals after 8 years in field service and can
agree that SHADOW works pretty well on PTFE, but you can certainly
use electroless copper.  You simply need to make sure that your
electroless initiates fairly slowly to improve hole wall adhesion.

You can also process PTFE through plasma; it is important to finish with a
helium burn rather than an oxygen burn to prevent
re-oxidation/passivation of the PTFE.

Regards, Fred Johnson



>>> Ed Cosper <[log in to unmask]> 10/21/97 12:41pm >>>
Does this material process the same as standard FR 4 with respect to
desmear and electroless?
All help is appreciated.

Ed Cosper
Graphic Electronics

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