I would assume that the second reflow will cause the PoP to go into
liquidus. If you are using a solder paste that can go through reflow
twice before cleaning, then you can cornerbond, underbond, or edgebond
the PoP using Loctite 3609 or similar chipbonder after it goes through
the first reflow. The component will then be held in place during the
second reflow.
You should not have to worry about the PoP package solder, as it is
typically a high-temp solder. If it isn't, then you may have to bond the
stack together as well as bond the package to the PWB.

R. Dean Stadem
Consulting Engineer
Lumagine, Inc.
11441 Rupp Drive
Burnsville, MN 55431
(952)894-9228
[log in to unmask]


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Peter L
Sent: Thursday, April 23, 2009 7:00 PM
To: [log in to unmask]
Subject: [TN] Second time reflow of PoP on bottom side of PCBA

Hello technet

I am reviewing an application involving PoP (14mm package on package) 
placed on the side A of the board, side B involves placement of multiple
SMT 
connectors (USB etc) therefore it's necessary to process them last. 

My question is whether anyone sees a problem with the PoP device on side
A 
going through a 2nd time reflow during side B processing? Would I need
to 
utilize a reflow carrier to shield side A to avoid secondary reflow of
the PoP 
device?

Any input is appreciated. Thanks.

Peter

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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 847-615-7100
ext.2815
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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 847-615-7100 ext.2815
-----------------------------------------------------