Hi Bob,
I don't remember exactly how the board was constructed, but I'm pretty sure
it wasn't etched. Copper that thick can be plated up. There's a company
called UPE ( http://www.upe-inc.com/ ) that can plate up to 200 oz. copper!
This board was machined down around the edges to expose the copper plane, it
went into a VME rack that pulled the heat from the board into the rack.
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Tuesday, July 24, 2012 1:35 PM
To: [log in to unmask]
Subject: Re: [TN] 10 oz Cu PCB Assys
Steve,
Is a thick layer like that actually etched or is it a machined / stamped
item that is part of the final stackup then plate through process?
Thanks,
Bob K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, July 24, 2012 7:50 AM
To: [log in to unmask]
Subject: Re: [TN] 10 oz Cu PCB Assys
Hi Bill!
It's been a while, but I once built some boards that had two 20 oz. layers
in them, one in layer 2, the other in layer 11 of a 12-layer board. Check
out:
http://stevezeva.homestead.com/HeavyMetal.jpg
http://stevezeva.homestead.com/HeavyMetal3.jpg
The SMT went surprisingly well. We had an Electrovert Omniflo-10 and the
biggest thing I did was to slow my belt speed down from my normal 32-ipm to
26-ipm, the set-points on the zones was a pretty typical ramp-to-spike for
tin lead solder. The copper actually seemed to help to even the heat across
the PCB. Now the board is going to stay hotter for a longer time, I even
think it was still liquidous for a split second while exiting the oven, but
the reflow actually went pretty well.
Wave soldering was another story. We had selective pallets for these boards
because there was SMT on both sides. The wave pre-heaters just couldn't heat
everything up prior to the wave unless I slowed the belt speed to a crawl,
which would mean that the board would spend WAY too much time over the wave.
So we wound up placing the pallet with the board into an oven to help get
things preheated which helped a great deal with hole fill.
To even think about doing any sort of hand touch-up on a board with this
much copper, pre-heat is absolutely necessary. We used Hakko's FR1012 IR
pre-heaters, they worked great!
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: Monday, July 23, 2012 7:42 PM
To: [log in to unmask]
Subject: [TN] 10 oz Cu PCB Assys
Hello Fellow TechNetters:
Can anyone share some information on processing SMD's on PCB's that have 10
oz. of Cu?
Difficulties in processing, lessons learned, etc.
Thank you all in advance,
Bill
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