RE: [SI-LIST] : why .062?

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From: Gaines, William (WILLIAM.GAINES@Aerojet.com)
Date: Thu Mar 09 2000 - 08:41:17 PST


And wire wrap is still flown on some Spacecraft. (backplanes)
(It is easy to make corrections & you do not need to re-fab and
re-buy connectors spec'ed for space $$$)

Bill Gaines

> ----------
> From: Cusanelli, Tony[SMTP:Tony_Cusanelli@mentorg.com]
> Reply To: si-list@silab.eng.sun.com
> Sent: Thursday, March 09, 2000 3:08 AM
> To: si-list@silab.eng.sun.com
> Subject: RE: [SI-LIST] : why .062?
>
> A few people asked for the "old guys" to comment on why boards are .062.
> Back in the dark ages (30 yrs ago) the boards I first designed were merely
> mechanical devices that supported parts. Connectivity was accomplished via
> wire-wrap. Parts were heavy and boards had to be thick enough to prevent
> breakage, but thin enough to carry. 1/16 inch became the right
> compromise
> and card guides, standard socket boards and chassis were all designed to
> fit
> that thickness.
>
> Even with today's lighter parts, tracks are thin and need some support.
> .032 boards are okay if they are small. Flexing and the pressure from
> connector insertion/extraction will fracture thin traces.
>
> PS - for you young guys - wire wrap was accomplished with a device similar
> to a hollow drill bit that would wrap 6-8 turns of 30 awg wire around a
> square or rectangular post. The edges would bite into the wire and make a
> gas-tight connection that was tested with a pull device (strain gauge).
> We
> had some PC boards, but they were mostly 2 and four layer. Draftsmen
> just
> could not lay out a board as fast as I could write a wirelist for the
> wiring
> machine.
>
> Yes now I feel like a dinosaur.
>
> Tony
>
>
> -----Original Message-----
> From: Alex Li [mailto:alexl@ati.com]
> Sent: Monday, March 06, 2000 9:36 PM
> To: 'si-list@silab.eng.sun.com'
> Subject: [SI-LIST] : different 4-layer board Stack up (S-P-G-S) ?
>
>
>
> Recently I saw a 4-layer mother board with 100 Mhz 128-bit memory bus.
> This board has unusual signal-power-ground-signal stack up. I talked to
> one of their engineer for this kind of arrangement. They said since most
> PC
> motherboard has several power plane split and on the top level there are a
> lot of components with pads. they think if they route all the 128-bit
> memory
> bus on the back and put it close to ground plane, they have much routing
> area and this will help to keep the signals clean.
>
> This is kind of new idea to me, does anyone see any drawback by this
> arrangement ? Will this decrease the decoupling caps performance ?
>
> Alex
>
>
>
>
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