Re: [SI-LIST] : Recommendations for High Density PCB to PCB Connection

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From: D. C. Sessions (dc.sessions@vlsi.com)
Date: Wed Nov 03 1999 - 07:11:07 PST


Laurence Michaels wrote:
>
> Doug Piper wrote:
> >
> > I'm working on a new project that requires me to make 40 connections from
> > one PCB to another in a space that's only about 0.2" x 0.5". Does anyone
> > have any experience or recommendations for making a connection of this
> > density?
> >
> > Doug Piper, Woven Electronics, P.O. Box 189, Mauldin, SC 29662
> > PH 864-967-1751, FAX 864-963-1761, e-mail: doug.piper@wovenelectronics.com
> > www.wovenelectronics.com
>
> Only recommendation I can make, is possibly some of the press-fit
> unidirectionally conductive foam material, such as is used on some of
> the more recent Intel Flash chips.
>
> Having done a few calculations, this works out to 400 connections per
> square inch. If you manage to put more connections in an inch, than
> most cotton sheets, I want to know how you did it! Connections on the
> trace level are going to be tight as well. This is going to be 1
> connection per 2.5 square mils. Assuming equal trace and space
> requirements, this works out to 0.625 mil trace and space. That's not a
> standard PCB you're talking about. Are you sure about the space
> requirements?

You might want to check your math on that density calculation.

5mm x 12.7mm space for 40 connections comes to about 1.5mm2/contact,
which is less than the density of an old 1.27mm pitch BGA.

-- 
D. C. Sessions
dc.sessions@vlsi.com

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