I have a question concerning the reliability of a PCB that has little to no
annular ring on the via holes on the external surfaces of a multilayer
board:

-there are about 100 such holes on the board
-all components are through hole
-the board is four layers, 0.062" thick
-solder mask fills most of these via holes
-the pad size is about 0.024", with a hole drill size of 0.020", and
finished hole size of about 0.016"
-the trace coming into the hole is 0.008" wide
-there are a few locations where a trace enters a hole and there is no land
(pad) at the junction of trace/hole, just the width of the trace
-the specification is for 2 ounce copper finished amount

The board house has 100% electrically tested the boards for shorts and opens
and found no failures, and believes that the boards will be reliable. We
have assembled, wave soldered and tested (before discovery of the problem)
about 30 of the units and have found no failures related to this issue.

The boards do not meet IPC-A-600 specifications. The customer designed the
board and did not call out any IPC spec.

My concern is the long term reliability of the trace to hole junction. It
seems that I remember hearing of high density boards actually being designed
without pads: the traces came directly into the hole. Has that been done
successfully?

Is the reliability questionable? Will successful thermal cycling of the
assemblies indicate long term reliability? Any thoughts or suggestions will
be appreciated.

Thank you,

Ed Berti

---------------------------------------------------
Technet Mail List provided as a 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
-----------------------------------------------------