PBGA overprint

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i have a 0.5 pitch(19x19 pbga array) ..with a pad of 20 mi... - Sep 30, 2004 by

Comment: A 20 mil pad for a .5mm pitch BGA? That seems l... - Sep 30, 2004 by RDR

sorry..it s 40 mils...pitch,...but stencil aperture is squar... - Oct 10, 2004 by

I have heard of making square apertures for round pads to ai... - Oct 11, 2004 by RDR

GIO

#30796

PBGA overprint | 30 September, 2004

i have a 0.5 pitch(19x19 pbga array) ..with a pad of 20 mils (thou) , solder mask is same...(20th..)..and an stenCil aperture of rectangular 22 X 22.1 thou...WHICH SHOWS..I AM HAVING AN OVERPRINT..MY PASTE IS A NO-CLEAN..

COMMENTS PLS...

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RDR

#30798

PBGA overprint | 30 September, 2004

Comment:

A 20 mil pad for a .5mm pitch BGA? That seems like an awful large pad for this device. If my math is right the pads will be basically touching each other. .5mm = .020". I would think that you have something else. You cannot have a 22mil aperture on .5mm pitch BGA they will overlap.

Anyway, I do not recommend overprinting a BGA to that extreme. Quite possibly you will see a lot of solder balls underneath this part. I am assuming that the pads on the board are round?

Russ

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GIO

#30914

PBGA overprint | 10 October, 2004

sorry..it s 40 mils...pitch,...but stencil aperture is square...ANY COMMENTS..

THANKS RUSS...

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RDR

#30920

PBGA overprint | 11 October, 2004

I have heard of making square apertures for round pads to aid in Xray and possibly allow for better release in some applications. The square aperture in your case would be for Xray inspection and not release. Usually a 20 mil square would be used for a 20mil round pad. Over printing in this case may be okay contrary to my earlier posting. I would recommend that you try it and look for solder balls underneath the part. Ultimately I would recommend that you use a 19mil round aperture instead.

Russ

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