Ken,

The process used for my boards is:
1. first drill only the  holes to be epoxy filled.
2. plate these holes as normal.
3. fill holes with epoxy (Dupont CB101).
4. grind epoxy flush to board surface.
5. drill and plate all the other holes, thus plating over the filled ones.

Problems are :-

filling holes smaller than about 12 mils (consult your fab house).
filling holes much larger than 25 mils if holes are very shallow (7 mils
deep).
getting the epoxy to stay flush after finish plating, especially with HASL
(ENIG is beautiful). It tends to rise and form bumps
not all fab houses are capable of doing this process well.

I tried it to help with thermal management of conduction cooled boards and
it works well. I specifically mention Dupont material, as some other types
just won't fill the holes (particle size in the compound).

Good luck,

Peter




                    Ken Patel
                    <[log in to unmask]        To:     [log in to unmask]
                    OM>                  cc:     (bcc: DUNCAN Peter/Asst Prin Engr/ST
                    Sent by:             Aero/ST Group)
                    TechNet              Subject:     [TN] Via in Pad: Filling of vias
                    <[log in to unmask]        using silver epoxy!?!?
                    ORG>


                    04/19/02
                    06:20 AM
                    Please
                    respond to
                    "TechNet
                    E-Mail
                    Forum.";
                    Please
                    respond to
                    Ken Patel






Guys,
I am dealing with high frequency board which is 25 mil thick and made of
Rogers material. The other side is totally exposed copper. How should I
handle as there via in pads (VIP)? I have heard about filling the vias
using silver epoxy and then plating it over. Can someone shed some more
light?

re,
ken patel

---------------------------------------------------------------------------------

Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
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 delivery of Technet send e-mail to [log in to unmask]:
SET Technet NOMAIL
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 1.8d
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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL
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
---------------------------------------------------------------------------------