Ron,
Where does the antipad contribution come in?
Steve

-----Original Message-----
From: Ronald Giachetti [mailto:[log in to unmask]]
Sent: Friday, May 21, 1999 9:52 AM
To: [log in to unmask]
Subject:


An equation for the estimating the number of layers to route a BGA:

# of layers = ( (n/2)-((G-Db-s)/(L+s))+1 / ((G-Dv-s)/(L+s))+1 ) + 1

where

L = line width
Dv = via pad size
G = I/O pitch
s = line spacing
Db = contact pad size
n = # of I/O

I saw this equation in a technical report, it is originally attributed to
Dr. C. Chao at HP Laboratory.  I
know somebody who has validated with some of their boards.  I'll be
interested in finding out how it works
with yours.

Ron Giachetti
Department of Industrial & Systems Engineering
Florida International University
Miami, FL 33174
[log in to unmask]


[log in to unmask] wrote:

> Looking for information on designing a printed circuit card using  several
> 256-pin micro-BGAs.  The pin scheme is a 16 X 16 matrix with 1mm pad
pitch.
> Issues include:
>
>         Routing approaches (how to best achieve routability).
>         Number of layers required.   Is there a formula to determine this?
>
> Any kind of information anyone can provide would be greatly appreciated.
> Thank you,
>
> Connie Lauterbach
> Sr. PCB Designer
> Evans & Sutherland
> Salt Lake City, UT
>
> [log in to unmask]
>
> ################################################################
> DesignerCouncil E-Mail Forum provided as a free service by IPC using
LISTSERV 1.8c
> ################################################################
> To subscribe/unsubscribe, send a message to [log in to unmask] with
following text in the body:
> To subscribe:   SUBSCRIBE DesignerCouncil <your full name>
> To unsubscribe:   SIGNOFF DesignerCouncil
> ################################################################
> Please visit IPC's web site (http://www.ipc.org) "On-Line Services"
section for additional information.
> For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
> ################################################################

################################################################
DesignerCouncil E-Mail Forum provided as a free service by IPC using
LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in the body:
To subscribe:   SUBSCRIBE DesignerCouncil <your full name>
To unsubscribe:   SIGNOFF DesignerCouncil
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section
for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or
847-509-9700 ext.312
################################################################

################################################################
DesignerCouncil E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE DesignerCouncil <your full name>
To unsubscribe:   SIGNOFF DesignerCouncil
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################