Speaking as one who advocated it, I intoduced it to some of our boards
where additional plating thickness was undesirable, but we needed maximum
thermal transfer down the vias from components to internal thermal planes.
The epoxy is thermally conductive, not electrically, in my case anyway. It
was also a compromise solution to filling all the holes with solder, which
may have fallen out again during CR, but in any event would probably have a
less-than-flat finish, which we needed for minimum thermal resistance when
mounting metal heatsinks on top.

It is an annoying and not very cheap additional process. It's also not
reliably successful. I later did the Math and found that only a very small
increase in copper plating thickness - decimal points of a mil at worst
case conductivity value - completely replaces the epoxy fill. There is a
limit to the hole diameters and aspect ratios that can be successfully
filled with epoxy as well.

Peter



Steve Gregory <[log in to unmask]>   15/11/2002 07:22 AM
Sent by: TechNet <[log in to unmask]>

Please respond to "TechNet E-Mail Forum."; Please respond to SteveZeva

              To:  [log in to unmask]
              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
              Subject: [TN] Conductive epoxy via filling...








Hi all!

Just a general question about filling vias with conductive epoxy. Why is
that done? Performance reasons? Electrical reasons?

Just curious why one would want to specifically use conductive epoxy to
fill vias...

-Steve Gregory-
--------------------------------------------------- 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
-----------------------------------------------------