Ioan,
It's not recommended. However, we have done it in the past, with pretty
high first pass yields. Depending on the weight of the devices, you may need
to use a temporary mask at the corners of the BGA to mechanically hold the
BGA's in place. We had 16 SBGA's (8 per side). Due to the weight of these
parts (heat spreader on the package), that's what we had to do. Failure to
do this could create elongated solder joints or open solder connections.
Depends on the weight of the device.
As for 2d x-ray inspection, it should be the same. You will be inspecting
for bridging, voids, abnormal shapes in the solder spheres. Depending on
your system, it may not have enough power due to the increase in density. We
found we had to go to a higher end machine for this scenario and CBGA's. It
will be a challenge, determining which BGA has a solder bridge, if one is
found. You will have to tilt the board to try and determine this. We have an
Ersascope to help determine this as well.
Regards,
Rey Sosa
Pentagon EMS
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Tempea, Ioan
Sent: Wednesday, October 30, 2002 8:39 AM
To: [log in to unmask]
Subject: [TN] Back to back BGAs
Hi Technos,
I've been asked by a customer of ours what were the rules of assemblying
BGAs back to back. This should mean having BGAs assembled on both sides of
the PCB, at the same coordinates.
I see right away the impossibility to X-Ray (2-D) and rework.
Did you ever run into this kind of design? Good/bad experiences?
Thanks,
Ioan
---------------------------------------------------
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
-----------------------------------------------------
|
