Hi Ken.  Motorola has done extensive studies picking up where IBM left off.
I strongly recommend that you contact your local Mot distributer and get
Mot's BGA PCB packaging/layout design guidelines.  They claim that on a PBGA
(plastic) one should use a soldermask defined pad.  That would be a
soldermask opening smaller than the actual pad diameter.  On a .050 pitch
grid array, for example, they state to use ONLY a .023 opening on a pad of
approximatley .030.  For ceramics and columns it's a diferent configuration
completely.  But - get the specs from Motarola.  They appear to have the
answers based on extensive studies they've done.  Regards, Russ Steiner
Controls/inc.  Good luck/best wishes.
-----Original Message-----
From: Ken Patel <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, October 27, 1998 3:04 PM
Subject: [TN] Hot: Trace width and air gap for 1mm pitch BGA


>BGA Design/process Guru,
>We are designing board with 1mm (39.37 mils) pitch 672 pin BGA. I have the
>following questions which I need urgently.
>
>(1) What is the recommended pad size?
>(2) What the recommended via size?
>(3) What will be the trace width and air gap if I need to pass 2 traces? We
>are limited in number layers so we want to go for double traces instead of
>single trace between the pads.
>
>re,
>Ken Patel
>______________________________________________________
>Ken Patel                       Phone:  (408) 490-6804
>1708 McCarthy Blvd.             Fax:    (408) 490-6859
>Milpitas, CA 95035              Beeper: (888) 769-1808
>
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