how wide of traces are necessary for 120V AC, 5amps?

[John Smith]

http://www.humiseal.com/protect/guide.htm

I think they are also available in spray cans from http://www.mouser.com and
from http://www.digikey.com/.

 

[Active8]

http://www.humiseal.com/protect/guide.htm

Mouser has the AR stuff and at least 2 others. Digi-Key has the
stuff, also. Can you order direct from Humiseal?

 

[Active8]

By far the most common copper thickness is one ounce (1 oz.). This seems
like a rather strange unit of measure for thickness, and it is. It means
that one ounce of copper metal has been deposited evenly onto a surface of 1
square foot. This is a very unintuitive measurement in my mind, but that is
what we use. One ounce copper translates to a copper thickness of about 1.4
mills. 2 ounce copper is twice as thick, 4 ounce copper four times, etc.
Two ounce copper is sometimes used on boards that handle significant amounts
of power/current, but other thicker sizes are rarely used except sometimes
for special requirements in power electronics. Sometimes they use really
thick copper to make windings of really low profile high frequency
transformers.

They do make some spray on substances that are supposed to improve the
electrical peformance of the board surface. I've got some stuff by Tech
Spray "Fine-L-Kote AR" conformal coating in a spray can that claims to make
your circuit surface more rugged while having a strong dielectric strength.
My impression is a real professional solder mask is really quite a bit
better than this stuff.

Better in what respect and how does an "impression" compare with
actual specs like dielectric strength and resistance to humidity
and other stuff?

 

[Fritz Schlunder]

Better in what respect and how does an "impression" compare with
actual specs like dielectric strength and resistance to humidity
and other stuff?

Well I don't know for sure really. My impression is just an impression and
isn't based on any kind of scientific research or tests, nor on extensive
personal use. If you only spray on one coat though it seems really thin.
It is clear and very hard to see. Since you can't see it when you are done
I almost felt like I was wasting my time spraying nothing onto the board.
With only one coat it seems quite easy to scratch, presumably much easier
than with an ordinary solder mask. Perhaps more coats would yeild stronger
results. My suspicion is it probably does improve resistance to
humidity/corrosive atmospheres, but without any scientific tests YMMV.

 

[Active8]

Well I don't know for sure really. My impression is just an impression and
isn't based on any kind of scientific research or tests, nor on extensive
personal use. If you only spray on one coat though it seems really thin.
It is clear and very hard to see. Since you can't see it when you are done
I almost felt like I was wasting my time spraying nothing onto the board.
With only one coat it seems quite easy to scratch, presumably much easier
than with an ordinary solder mask. Perhaps more coats would yeild stronger
results. My suspicion is it probably does improve resistance to
humidity/corrosive atmospheres, but without any scientific tests YMMV.

Ok... Just wondering. I haven't found any spray on solder mask
aside from a thread where someone used Testors Spray Enamel and
claimed that the solder and iron vaporized it. That's not really
solder mask and the contamination of the joint would probably be
unacceptable from a reliability standpoint.

So I take it this stuff you used is the about the same. You sprayed
it on the pads as well as the tracks and bare board?

I've found Photoimageable Liguid Solder Mask and not much else.
It's another back-burner area of research for me.

 

[Mac]

That may be true, Mac. But, if you design UL now, there may be less to do
later. Lots of times they (the ones who have the say-so) say approval isn't
necessary, then sales finds out the competition is UL approved and the
crunch comes to get it for your own product.

Besides, using UL requirements for spacing seems to me to be a good design
starting point.

My 2 cents.

John

Actually I agree 100%. Whether the item is to be UL listed or not, it
would make sense to design it as if it were.

But I wanted to caution the OP that traces may not be allowed at all
unless they are protected by a polycarbonate (or similar) cover. This is
partly to protect people who may work on the board later, and not realize
that there are exposed lethal voltages present on the card. In fact, I
think that the high-voltage circuitry is supposed to be labeled, too.

This all makes sense. The last thing I want to do is get shocked or
electrocuted while poking around inside a consumer product. ;-)

Mac

 

[Mike]

The rule of thumb is about: 10 mil / per Amp.
So, I would say somewhere between 50 mil and 100 mil.
D = The distance between trace centers.
H = The height of the trace from the ground plane.
%crosstalk = 1/1 + ((D/H) * 2) * 100

Without knowing D or H, I can't give you a number.

How do you define crosstalk? More specifically, how can you define the
crosstalk if the frequency is unknown (the OP specified a frequency, but
your equation is only geometry dependent)?

-- Mike --