yes it usually is 80%, though when the ball gets to .60mm diameter + it's 75% ------------------------------ If you're interested I have some routing guidelines for BGA's of 1mm, .8mm, and .5mm pitches. On 10 May 2005 at 11:59, John Guy wrote: Hello All, I was wondering if there is some guideline for the recommended pad size for a BGA based on the component's ball size? I have been told that it is recommended that the pad diameter be about 80% of the ball diameter, but I would like some confirmation. Thanks in advance, John Guy Surface Mount Process Engineer diversifiedsystems, inc ------------------------------------- Depends if you want to have solder mask defined pads or not. If mask defined then a rule of thumb is to aim for the same mask aperture on the interposer. Non mask defined ROT is to make the pad equal the minimum ball diameter so that solder joint forms around the pad sides improving stress resistance. Although, watch out for ball collapse, and consider what height is left if your needing to clean after reflow, and if there is enough annulus for via in pad (if your forced down the HDI route). Generally, the larger higher value device manufacturers will give some guidance. Altera and Xilinx have apps notes, some stuff at Intel and IBM as well if you've got time to search. If your using an EMS then they probably have their own preferences, best to go along with them because it's their job to stick the bits down on the board with electric glue. Some apps notes: http://www.asat.com/products/library/fg1033.pdf http://www.altera.com/literature/an/an114.pdf The National Physical Lab in the UK also a wealth of data http://www.npl.co.uk/ on solder joint reliability including Pb free. Here's a thought: With all this political correctness stuff prevailing (no naughty words etc), how do you folks on the sunny side of the Atlantic get away with saying 'solder' and 'soldering' all of the time? Best Regards David Greig -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Alcorn, Brent Sent: Tuesday, May 10, 2005 12:09 PM To: [log in to unmask] Subject: Re: [TN] BGA Ball/Pad Size Ratio Hi John, That is correct, see IPC SM-782 rev A amendment 2, section 14. Brent -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of John Guy Sent: Tuesday, May 10, 2005 12:59 PM To: [log in to unmask] Subject: [TN] BGA Ball/Pad Size Ratio Hello All, I was wondering if there is some guideline for the recommended pad size for a BGA based on the component's ball size? I have been told that it is recommended that the pad diameter be about 80% of the ball diameter, but I would like some confirmation. Thanks in advance, John Guy Surface Mount Process Engineer diversifiedsystems, inc. 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Thank you. --------------------------------------------------- Technet Mail List provided as a 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/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 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/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------