Artwork of an electronic board

[chicopee]

When examining the artwork of an electronic board supplied from a 60 cycle, 120 volt power source and noting the different widths of the artwork, is there a rule of thumb at how current is flowing per,lets say, inch of width?

 

[nbucska]

yes there is.

<nbucska@pcperipherals.com>

 

[IRstuff]

Why not just to a websearch:

http://www.dogpile.com/info.dogpl/search/web/copper+current+capacity+board

TTFN

 

[buzzp]

Be careful of which table you use for widths vs. current capacity. I have found some that are terrible and do not come close to being right. They plot temp rise vs. current. You will also need to know the 'weight' (thickness) of the copper traces, with 2 oz being the most common. This, too, is subject to some discrepencies, it seems, as far as 2 oz = x mils.
There is much info on the web just use caution and a search engine.

 

[logbook]

I would have said that 1 oz copper was the most common, 2 oz being reserved for heavy power applications. Inner layers of multilayer boards can use 0.5 oz copper.

 

[buzzp]

I have not worked with multi layer boards.
However, when we tried to spec 1 oz copper we found that they still make it with 1 oz copper because of a cost issue- board house can buy 2oz copper clad all the time instead of stocking 2 kinds. These were only 2 layer boards.
With multilayer boards its sounds as though this would not be the case.

 

[chicopee]

OK,please let me know how one or two copper relate to the connection(artwork) widths between components. I know that the cross sectional areas of the connections have a relationship to resistivity and heat generation so what is the rule of thumb between cross sectional areas and current flow and how does that one or two ounces of copper relates to these cross sections?.

 

[jraef]

Heat density on the board material. If you concentrate power paths too close to each other you may warp the board and/or sparate the copper from it.

&quot;Venditori de oleum-vipera non vigere excordis populi&quot;

 

[IRstuff]

The oz rating is per unit square area, so a 2 oz board should have 2x thickness of copper than 1 oz board.

HOWEVER, if you come anywhere close to where the IR drop in the copper causes anything but a minor temperature change, you've underdesigned the layout. The copper traces should NEVER get to the point of being a dominant effect, UNLESS you purposefully designed it that way



TTFN

 

[jraef]

Yeah, what he said.

 

[buzzp]

The ounces of copper designates the thickness of the trace and thereby how much current it can carry (which of course will tell you how much heat will be generated). I am with IRstuff on his comments.
I did a little experiment a long time ago and had some 2 oz copper traces of various widths made up on a PCB (length was the longest we would ever use and the shortest). I then ran current through it to determine how much current it could actually handle without a significant rise in temperature. I suspect many other people have done this but you may want to do it as well to get some of your own numbers to use. (I don't have the results any more or I would give them to you).