Hi Leif Erik,

I wouldn't worry, the bigger the pin count the more stable to BGA (more balls = more surface tension). I have built tons of boards with many upside down BGAs, some even having metal top. No issue. LF solders have higher surface tension than SnPb and this can only help even further.

Regards,

Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
T | 450.967.7100 ext.244
E | [log in to unmask] 
W | www.digico.cc

N'imprimer que si nécessaire - Print only if you must


-----Message d'origine-----
De : Leif Erik Laerum [mailto:[log in to unmask]] 
Envoyé : April-01-11 2:11 PM
À : [log in to unmask]
Objet : [TN] BGA on Solder Side

  Technetters,

We are faced with a design that puts 2 BGAs on the solder side of a 
board. It will therefore go through reflow on the bottom when building 
the other side. The BGA is 19 x 19 mm 484 balls .8mm pitch. Av Weight 
1.3302 g.  This is a lead free design. I seem to have seen a paper on 
the subject discussed on technet, but the archives do not work for me 
right now.

We have done thousands of boards with BGAs on both sides, but always 
small ones with max ball count at 84. We have never one this size. Any 
experiences out there that you can share? Do's and don'ts?  I can tack 
the corners of the  BGA with SMT adhesive, but I would rather not if I 
can avoid it.

-- 
Leif Erik Laerum




CONFIDENTIALITY NOTICE: This email and any attachments are Texas Memory Systems' proprietary material for the exclusive and confidential use of the intended recipient.  If you are not the intended recipient, please do not read, distribute or take action in reliance upon this message. Any unauthorized disclosure is prohibited.  If you have received this in error, please notify us immediately by return email and promptly delete all copies of this message and its attachments from your computer system. 



______________________________________________________________________
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
-----------------------------------------------------