Re: [SI-LIST] :PCB Bd thkness'

About this list Date view Thread view Subject view Author view

From: Ritchey Lee (leeritchey@earthlink.net)
Date: Fri Mar 10 2000 - 08:02:47 PST


.062 thick PCBs happened way back before we actually made printed circuits. Early electronics used sheets of bakelite to mount vacuum tubes, resistors and capacitors. The standard thickness of bakelite
sheets was .062. These sheets were laminated as the outer layers of sheets of plywood to provide a good workbench surface. We just borrowed the material for electronics.

One day someone bonded foiil copper to the sheets of bakelite and etched circuits. Not long after, we decided we needed connectors so we could plug many boards into backplanes or racks. The edge
connector was born. Now that we have billions of edge connectors designed for .062 thick PCBs, we are stuck with this odd dimension. .093 is jsut 1.5 times .062. By the way .062 is 1/16 of an inch
thick. .093 is 3/32 of an inch.

Funny how we have dimensions in electronics that stem from the plywood industry!

And-- that is the rest of the story!

Lee

Dave Hoover wrote:

> I always thought the .062", .093", .125" was for through hole leads,
> press fit connector length, and edge card connectors. Standardize
> for consistancy and repeatability. That's what I was taught.....
>
> Dave
> -----Original Message-----
> From: Abd ul-Rahman Lomax [mailto:marjan@vom.com]
> Sent: Tuesday, March 07, 2000 12:59 PM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : different 4-layer board Stack up (S-P-G-S) ?
>
> At 11:14 AM 3/7/00 -0700, ajmani@us.ibm.com wrote:
>
> >By the way, can someone enlighten me on how 0.062" came to be the standard
> >board thickness.
>
> I haven't seen any documentation, but the reason is fairly obvious. 1/8
> inch was thicker than necessary for most applications and 1/32 inch was too
> thin, so 1/16 was chosen. .031 and .125 are still standard core
> thicknesses, along with 3/32, 0.093. We see the same history in 1/2 ounce,
> 1 ounce, and 2 ounce copper foil.
>
> marjan@vom.com
> Abdulrahman Lomax
> P.O. Box 690
> El Verano, CA 95433
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
> majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list
> or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu
> ****
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu
> ****

**** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Apr 20 2000 - 11:35:31 PDT