The use of conductive epoxy is solely to provide a flat (plated) surface
for the probes to impinge upon, rather than a pad and hole. By filling the
hole with epoxy, you prevent the probes from damaging the plating at the
edge of the hole, while the conductivity of the test pad is largely
unaffected (actually improved slightly) since the copper plating inside the
hole does what it would normally do anyway, with or without epoxy filling.
Epoxy filling does not replace the copper plating as it's applied after the
plating process.
A number of fab houses do fill holes very successfully within certain
bounds - hole diameter and aspect ratio are the two critical parameters in
determining if a hole can be filled or not. I can give you the names of 3
or 4 fab shops I've used for epoxy filling if you want to contact me
off-line.
Peter
Collins Graham <[log in to unmask]> 15/04/2003 07:32 PM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to Collins Graham
To: [log in to unmask]
cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: Re: [TN] Neither a question, or a response...
Hi Dave
Whenever I hear of issues like this I usually go hound the test guys to
change the probes on the ICT tester. We do a fair bit of partial wave
here, so lots of via surfaces don't get touched by the wave. To
manually fill these would be a pain in the wallet, and I'm not getting
into screen printing paste on to vias if I can avoid it. Thus far the
test guys have been able to get good results with different probes.
If you are going to use a conductive epoxy, is it as conductive as
copper? I'd be worried about throwing off the test results. E.G. my
ICT is looking for a 500k resistor, but my conductive epoxy is adding
10k to the reading - I might replace parts as being out of tolerance
when they are actually just on the edge... Just a thought.
Good luck!
regards,
Graham Collins
Process Engineer,
Northrop Grumman Canada Corporation
Halifax
(902) 873-2000 ext 6215
>>> [log in to unmask] 04/15/03 08:09AM >>>
I do have a question and would like a response offline please. I have
2000
vias on the bottomside of a wave soldered board and vias (not all) will
be
used by test. Problem is operators spend way too long inspecting to see
the
vias are filled by the wave. I want to fill the vias with conductive
epoxy,
Methode or Dupont material. I hear it is done but can find none of our
board houses who have ever done it. Is this a fantasy? A good theory no
one
is doing? Why not? I got a response that it is "very very expensive"
what
does that mean? $1 a board more $10 a board more? And yes I have
searched
the archives. This is a high volume job I may be able to eliminate 3
shifts
worth of inspection vs. whatever the increased board cost is.
Thank you. I promise to post results to Steve's website complete with
pictures whether it works or not.
Dave Chapman
Manufacturing Engineer
Circuit Service Inc.
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV
1.8e
To unsubscribe, send a message to [log in to unmask] with following text
in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for
additional
information, or contact Keach Sasamori at [log in to unmask] or
847-509-9700
ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV
1.8e
To unsubscribe, send a message to [log in to unmask] with following text
in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at:
http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for
additional
information, or contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
-----------------------------------------------------
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to
[log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to
[log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700
ext.5315
-----------------------------------------------------
[This e-mail is confidential and may also be privileged. If you are not the
intended recipient, please delete it and notify us immediately; you should
not copy or use it for any purpose, nor disclose its contents to any other
person. Thank you.]
---------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8e
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
Please visit IPC web site http://www.ipc.org/html/forum.htm for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------
|
