From: "Roger Hamlett"
Subject: Re: PCB trace width/capacity question
X-Newsreader: Microsoft Outlook Express 5.50.4807.1700
Date: Thu, 16 Jan 2003 10:28:04 -0000
NNTP-Posting-Date: Thu, 16 Jan 2003 10:33:53 GMT
Organization: ntl Cablemodem News Service
"Glenn Ashmore" wrote in message
> Not to make a pest of myself but I have another question on my remote
> light switch system.
> In laying out the printed circuit board, how do I figure the trace width
> to carry the required power? I figure the +12V buss will have to
> carry about 15A max but want to double that for a safety margin to say
> 30 amps. Total length of the trace is about 3" and the board will be 2
> oz (2.8 mils) copper. The limiting factor is clearance to the pins. Is
> that possible or do I need to go to wire?
You might want to consider a 'bus bar', rather than wire, if the power needs
to distribute to more than one point. The ones I mean, are the metal 'strip'
bars, with pins at intervals. These are cheaper to assemble than seperate
wires, and offer the sort of current rating you require.
A track to carry this will need to be heavy (about 0.15" typically,
depending on the temperature rise you can accept), and you must also be very
careful about the hole sizes chosen (common problem is leaving too much
clearance between the pins, and the plating in the holes, which when dealing
with these sorts of current, leads to increased heating at this point...).