Tom,

Is this a ceramic or plastic BGA ?

Bill Kunkle at MET Assocs



-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Gervascio, Thomas L
Sent: Wednesday, February 11, 2009 3:21 PM
To: [log in to unmask]
Subject: [TN] BGA stencil aperture design guidelines


I am dealing with an intermittent solder bridging on a BGA package-
about 5 percent of the time.  One avenue to make the process more robust
I was looking at was redesigning the stencil aperture.  I am currently
using a 33 mil square solder aperture giving a paste volume of 2722
cubic mils (with a 5 mil stencil). This reduced the incidence of
bridging - the previous stencil was 6 mils thick and had a print volume
of 3267 cubic mils. The ratio of the stencil aperture to the stencil
aperture area is 92%

The sphere diameter on the package is 24 mils and the pitch is  and in
the past I have made stencil apertures 2 mil larger than the maximum
diameter- in this case the volume would be 1540 cubic mils.  The ratio
of the stencil aperture wall to the stencil print area for a round
aperture is 52%. I spoke with the supplier of the component but they had
no recommendations and a cursory Google search provided no additional
information so I thought I ask the Technet folks.

Thanks


 Tom



---------------------------------------------------
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
-----------------------------------------------------