Homebrew PCBs

>From: "Dave Mucha" <dave_mucha@...>
>Reply-To: Homebrew_PCBs@yahoogroups.com
>To: Homebrew_PCBs@yahoogroups.com
>Subject: [Homebrew_PCBs] basic basics of boards
>Date: Sun, 21 Sep 2003 14:24:05 -0000
>
>Hi all,
>
>I was wondering it there is an introduction to basics of schematics
>and board design?
>
>Things like what polarity is the square pad on an LED ?

Square pads generally indicate pin 1 on a component. I don't think it is 
used much these days, as it takes up too much area.

>Why 15 mil traces and not 12.5 mil ?

For my home made PCBs I go down to 10 mils occasionally.

>how to best isolate an AC rectifier/cap from the rest of the DC on
>the board ?  things like that.
>
>are there 'standard' drill sizes that are common for all board
>houses ?

0.8 mm is the most common drill size, used for ICs, Rs and Cs.


>
>I have a friend who says all square pads on 2 pins are ground or
>negative. Is that rule of thumb or general industry practice ?
>
>and it seems a 90 degree corner on a 15 mil trace, when etched can be
>undercut to less than 10 mil.

It's a good idea to mitre all corners. They etch better and work better at 
high frequencies.

>
>Instrumentation inputs may be put inside of a ground ring to as to
>keep all stray baord voltages away.
>
>Seems I went to the monkey-see monkey-do school of board design.

"Sitting by Nellie" is the UK equivalent.

Leon
--
Leon Heller, G1HSM Tel: +44 1424 423947
Email:leon_heller@...
My web page: http://www.geocities.com/leon_heller

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