Subject: | |
From: | |
Reply To: | |
Date: | Tue, 5 Oct 2004 11:01:16 -0700 |
Content-Type: | text/plain |
Parts/Attachments: |
|
|
If you want to eliminate the voiding issue and have a quick check if the
part is soldered...try putting some vias in the grnd pad....Make sure you
get solder into the vias...3 to 4 mils of solder in the vias should
compensate electrically and thermally for the missing copper generated by
the holes...
Paul Edwards
Process Engineering
[log in to unmask]
Tel: 408-433-4700
FAX: 408-433-9988
Surface Art Engineering
81Bonaventura Dr.
San Jose, CA 95134
DUNS: 944740570
CAGE/NCAGE: 1XZ48
-----Original Message-----
From: Jason Gregory [mailto:[log in to unmask]]
Sent: Tuesday, October 05, 2004 6:16 AM
To: [log in to unmask]
Subject: Re: [TN] Solder pad under chip
Sounds like possibly the pad was not in the solder paste layer and wasn't
cut. As far as inspecting, I had to do this in a former life. We inspected
the pad with a 5DX, but not just for the presence of solder, but for solder
coverage percentage. It was in the specs to ensure 70% solder coverage. I
also learned alot about vacuolar porosity. You might want to inspect a
sample every 10 boards or so with X-ray.....if you have the ability.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Bob Wilson
Sent: Monday, October 04, 2004 3:01 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
-----------------------------------------------------
---------------------------------------------------
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
-----------------------------------------------------
|
|
|