even 80% of .8mm leaves enough, that's .64mm which is 25 mils, I recently did a design with pads of .35mm and .25mm pads for BGA's, which is around 14mils and 10mils dia.
-- Jenny Prosmitsky <[log in to unmask]> wrote:
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.
Custom Products Division
3939 W. 56th Street
Indianapolis, IN 46254-4961
Telephone: 317-299-9547, x336
Fax: 317-298-2055
E-mail: [log in to unmask]
Web: www.divsys.com
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