Phil,
Although a batch process and capital intensive, a plasma desmear is another
way to deflourinate the Teflon to present a wettable surface. It may take
some looking, but this could be done as a subcontracted operation at a
vendor providing this service. The pre-cut wire could then be sealed in a
container filled with an inert gas until you need the material for assembly.
Lastly, another good resource to contact for ideas is Dupont..
Ron VandenDolder
Telaxis Communications
SouthDeerfield ,MA
[log in to unmask]
-----Original Message-----
From: DUTTON Phil [mailto:[log in to unmask]]
Sent: Wednesday, March 21, 2001 7:03 PM
To: [log in to unmask]
Subject: [TN] Potting in PTFE enclosure
Hello Technetters,
A problem that I hope that some of you assembly experts can help me with.
I have a Printed Board Assy that is to be potted in a PTFE based enclosure.
The wires connecting the board to the outside world are also PTFE insulated.
The entire unit will spend it's life attached to, and partially immersed in
a lead acid battery. We need a fairly good bond between the potting compound
(polyurethane)and the PTFE to ensure that none of the corrosive
liquids/vapours can travel by capilliary to the PB. Using a flouropolymer
etch solves this problem, but turns the colour coding on the wires to brown.
Also there are some concerns about how far the etchant can wick up the
wires, possibly affecting their soldering. A suggestion has been made to
sleeve the wires for a short length, within the encapsulant using adhesive
lined polyolefin heatshrink to provide a seal, rather than etching the
wires. The idea being that the polyolefin will bond to the potting compound,
and the heatshrink adhesive will bond sufficiently with the PTFE wire
insulation. Is there any problem with this approach, or are there any
suggestions for a better way?
Thankyou,
Phil.
Phil Dutton C.I.D.
Senior CAD Technician
IPC Certified Interconnect Designer
Tenix Defence Systems Pty Ltd
Systems Division - Adelaide
Second Avenue, Technology Park,
Mawson Lakes. SOUTH AUSTRALIA 5095
================================
Phone (08) 8300 4400 (reception)
(08) 8300 4481 (direct)
Fax (08) 8349 7420
email [log in to unmask]
Internet Page http//www.tenix.com
================================
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