It's also a matter of the local air pollution profile. Locally, copper roofs turn black. Shocks the heck out of people who put one on without bothering to look at the others in the area. I suppose you can probably apply artificial patinating chemicals (which would also be the solution for your sea monster, especially if it's inside). Outside I expect the normal rain chemistry would revert to black, here, short of patinating and then sealing with acrylic or the like.
i think it was HFPC '96 where there was a great paper on PCBs as heatsinks. ISTR there was almost no difference with or without solder mask.
by the time one tosses in a few gazillion thermal vias, I suspect the effect of solder mask drops into the noise floor.
and yeah, the dT cant be too high. This latest PCB I have I am pouring the heat into an enclosure via the PCB. Which is why the really hot part is astonishingly close to a corner.
and I'm swapping watts for dollars with nice FETs - DirectFETs are pretty darned good; stray L is so low on this design I dont need any of my snubbers, so next rev I'll toss 'em and replace with a pour :)
Cheers Terry
I've seen a lot of green copper roofs, but I can't recall seeing a black one. What gawd-awful metropolitan area do you live in that turns 'em black ?:-)
...Jim Thompson
That's because this is America and we are not the most patient folks. You'll have to wait a couple hundred years.
Reminds me of a grounds keeper in Scotland. A friend (at that time audio engineer at a TV station) asked him how they kept the lawns so lush and saturated-green. "Oh, just give it a wee clippin wunce a week. Do dat for aboot tooh hondrraed yeahrrs."
I don't particularly like those holders. You almost have to insert the battery with a hammer but it still can wiggle itself out during long prop-aircraft flights or washboard road trips in a truck.
[snip]
About 30 years ago I did an off-line switcher (using MJE13000-series bipolars) for GenRad's PSP portable tester. Because of some exquisite snubbing (by yours truly :-) it ran so cool I didn't need any heat sinks on the flags. So cool, in fact, that I _once_ grabbed a flag to see how "cool" it was... unfortunately it was "hot" with 400V P-P... producing great uproarious laughter amongst the technicians ;-)
...Jim Thompson
It may actually be "lack" of, or it may be all the lovely acid rain we're downwind of. NW Mass, SW Vt, out in the trees and mountains.
Partly, you'd have to look for them - black is a pretty common roof color, so it doesn't stand out the way a nice green one does - the green is unusual, and eyecatching. But when you drive by a tarted-up house with a shiny new copper roof, and later you drive by the same tarted-up house and it's turned black, it's noticable.
Saw some nice green copper in Quebec City, as I recall.
I
They all do that in the beginning but it's more a dark brown. "Beginning" meaning the first few decades after installation. Then wait another 150 years and it'll slowly turn green.
I
I guess Boston is old enough ;-)
...Jim Thompson
there
so I
AFAIU Lawrence was writing about residential buildings and unfortunately the average American wood frame home doesn't have a life span anywhere close to where copper can develop patina on its own. The few exceptions would be some of the brick and mortar houses that can occasionally be found back east. Plus nearly all of the big city buildings.
Of course, you can help patina along. I am not sure and this is very dangerous but I believe muriatic acid can turn copper green within hours. Now don't do this!
The 10Oz PCB was for a 100kW 140A 400V motor controller.
A buddy of mine in AM worked for Syncor, and gave me one of their blank PCBs. 8-layer 8-Oz Cu. Stunningly heavy - it was almost entirely Cu (perhaps 20% FR4?)
Cheers Terry
LOL! Would you believe I am designing a proportional base drive circuit for an MJE13003..... 70's here I come. Except I'll use Si not Fe (Mn, Zn etc)
Cheers Terry
I saw an episode of Antiques Roadshow a while back where a guy brought in a copper statue. He had sand-blasted it to get rid of all the nasty green muck, and it looked gorgeous. oops, it was Roman, and he devalued it by about 90%
Cheers Terry
For small pieces of copper, you can electroplate them in a solution of baking soda.
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They need to plate the vias somehow.
IIRC one such issue is thermal relief for vias and through hole mountings. If you are using the ground plans for thermal dissipation the rules are the opposite. Try to keep this in mind with every connection you make.
I wasn't all that but if it is the same guy they bound him to some sticks.
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