Hmmm.
If the aperture was on the paste layer, I would expect that it would be
cut.  I suppose you may want to find out from the stencil house why it
was not cut.  Is the aperture defined properly?

Also, in cases where there is something a little different, it is always
a good idea to kind of point it out on the assembly drawing.  A note
like "Ensure pad 21 on U1 is soldered.  Inspect using Xray or side
viewing equipment." 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Wilson
Sent: Monday, October 04, 2004 4:01 PM
To: [log in to unmask]
Subject: [TN] Solder pad under chip

Hi!

I have a chip on a board (Linear Technology part number LTC3414) found
here:
http://www.linear.com/pdf/3414f.pdf

It has a pad (pin number 21) that is underneath and a note that says:
"To maximize the thermal performance of the LTC3414, the exposed pad
should be soldered to a ground plane."

I built the footprint and made sure the pad was soldermasked and
included the pad shape in the pastemask file.

The engineer was trouble-shooting and de-soldered the part from the
board.  It looks like there was no solderpaste or solder on the pad.

Here's the (dumb) designer question:  How would the solder get to that
pad underneath? Should we add a requirement note saying that the part
should be inspected or x-rayed to see if the pad is indeed soldered?

Thanks for all and any suggestions.

Regards,

Bob Wilson
www.cstone-design.com
[log in to unmask]

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

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