Well, for starters, the dip paste used to stack the packages is more prone to solder balling. This is because it has a lower metal content and smaller solder particle than screen-printable pastes. Also, it's fairly easy to drown the part in flux. You need to take care to apply liquid flux only to the surface of the balls. I should add that Bob Willis is doing a webinar on PoP during Virtual PCB next week. http://circuitsassembly.com/cms/news/10851-pop-signal-integrity-webinars -highlight-virtual-pcb Best, Mike Mike Buetow Circuits Assembly w/m 617-327-4702 >>> VIRTUAL PCB, the industry's only online tech conference and exhibition, March 8-9, www.virtual-pcb.com <<< Follow me on Twitter: twitter.com/mikebuetow -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Christopher Young Sent: Wednesday, March 02, 2011 9:33 AM To: [log in to unmask] Subject: [TN] POP THE QUESTION?? Can anyone out there give me the pitfalls of POP placement Technology (Package on package) within manufacturing. Also names of CEM's within the UK capable of successfully placing down such devices. Regards Chris The information contained within this e-mail and any files attached to this e-mail is private and in addition may include commercially sensitive information. The contents of this e-mail are for the intended recipient only and therefore if you wish to disclose the information contained within this e-mail or attached files, please contact the sender prior to any such disclosure. If you are not the intended recipient, any disclosure, copying or distribution is prohibited. Please also contact the sender and inform them of the error and delete the e-mail, including any attached files from your system. Cassidian Limited, Registered Office : Quadrant House, Celtic Springs, Coedkernew, Newport, NP10 8FZ Company No: 04191036 http://www.cassidian.com ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- 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.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- 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.aspx?Pageid=E-mail-Forums for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------