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Heavy Copper Board Costs

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dude_500

Wed Oct 15 2014, 08:32PM

Registered Member #2288 Joined: Wed Aug 12 2009, 10:42PM
Location: Cambridge, MA
Posts: 179

I'm wondering roughly how much heavy copper boards will cost to manufacture. It'd need to be a double-thickness board (1-2oz signal, 10-20oz power). Board companies won't tell me unless I create all the gerbers and do a formal quote, which would take quite a while for me to make the correct multi-layer gerbers for this just to discover that heavy copper is absurdly expensive.

Not a single page on the internet I can find that actually gives even a ballpark price estimate.

Does anyone know what this will roughly cost in low quantities of 10 or 20 boards of a normal size (say, maybe 3x6 inches)? Am I looking at $100 a board? $500? $5000?

2Spoons

Wed Oct 15 2014, 10:31PM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

Short answer : lots!. We've done a 4oz 8 layer board at work, and its about 3x the price of 2oz. It would probably be cheaper to use 2oz everywhere and fabricate sheet metal links for the high current bits - this can be easily done by etching copper sheet.

Sulaiman

Wed Oct 15 2014, 11:49PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Repairing some high current pcbs I have noticed a few approaches
. wire links .. insulated multi-stand copper wire
. solid copper wire soldered along high current pcb tracks
. thick solder coating of central portions of high current traces
. c70um (2 oz/sq.ft.) multi layers in parallel with many vias

I could speculate on relative merits but I don't actually know.

Patrick

Thu Oct 16 2014, 02:10AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Is the high-current high-frequency too?

Steve Conner

Thu Oct 16 2014, 11:31AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

I've had 4oz boards made and they are about 3x the price of the standard thickness. No idea of prices for the heavier weights, or if 20oz is even possible.

Dr. Slack

Thu Oct 16 2014, 01:10PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

1-2 oz is very easy to come by, 10-20 less so. The fundamental board making process, start with a thin sheet of copper then subtract what shouldn't be there, is not well suited to thick copper.

At high currents the limiting factor for tracks is not only the cross sectional area but also the ability to dissipate heat. This militates against having multiple internal thin layers paralleled up.

For a few off, I would say do all tracks in 1-2 oz, and then beef-up the heavy current tracks by soldering on a suitable cross section copper wire. The track on the board holds it in place, shows you the route, keeps it neat. If it interfaces with (say) TO-220 component pins, then you should take a turn of wire around a nail through the hole, to form a loop on the end for good solder contact.

If you are looking at boards because you want to scale this up to medium quantities, then you could make a jig for rapid forming of the heavy wire, from one of your boards, a backing board, and some nails through the terminal holes and at key changes of direction. Don't forget to straighten the wire after you've taken it off the reel, before forming, by twisting a length of it under tension between a vice and a drill.

Carbon_Rod

Thu Oct 16 2014, 10:02PM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

In general,
most PCB houses will not do heavy clad boards.

The ones that do often require finishing with a PCB CNC router on a fiberglass or ceramic board.

The ones that dip boards in solder... don't sell the garbage locally.

johnf

Fri Oct 17 2014, 08:08AM

Registered Member #230 Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284

In this modern day high current pcb's are made on aluminium using the oxide layer to insulate. This gives excellent heat transfer and is used on high current invertors / motor drives, and led lamps etc

Carbon_Rod

Sat Oct 18 2014, 01:21AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

They have 4oz Metal core PCBs:

IIRC they use a bonded Kapton insulation layer on this product.

Fiddy

Wed Oct 22 2014, 11:26PM

Registered Member #8817 Joined: Mon Dec 17 2012, 05:16AM
Location: Australia
Posts: 110

dodgy fix = don't put solder mask on high current traces so its bare copper then melt solder all along the trace, the trace CSA has now sky-rocketed with the cost of no solder mask (insulation)

Onetesla did this on their high current traces on their DRSSTC

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