Hi Grant!

I don't know if the boards I've had experience with are like yours, but
the ones I've had experience with have had a great deal of copper in
them.

Below is a cross-section of one:

http://www.stevezeva.homestead.com/files/Rough_Cross_Section.jpg

The copper core on that one was .055" thick. Here's another:

http://www.stevezeva.homestead.com/HeavyMetal.jpg

This board didn't have a copper core per-se, but layers 2 and 11 were
40-oz copper layers..

When I first learned that we were going to build the first board I had
all kinds of questions. I didn't think our reflow oven was going to be
able to handle it. I thought that we were going to need vapor phase to
reflow it. But actually, it was a piece of cake. We were using
Electrovert Omniflo-10's at the time, and all I really did was slow the
belt-speed down to give the board some time to absorb the heat. I
normally ran most boards at 32 inches per minute, I ran the heavy metal
boards anywhere from 26-28 inches per minute and they did fine. 

The heavy copper actually made the heat very even across the board,
there was very little delta across the assembly. One caution; when a
board with that kind of mass comes out of the oven, it is going to be
VERY HOT and stay hot for a lot longer than most assemblies! Depending
on the mass, the solder on the board may still be liquidous just as it
comes out of the oven.

-Steve Gregory-  

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Grant Emandien
Sent: Friday, March 16, 2007 5:42 AM
To: [log in to unmask]
Subject: [TN] Metal-core PCBs

'netters, has anyone advice/guidelines to offer on the reflow of
metal-core PCBs? We are running for the first time and would appreciate
any insight.
 
Regards
Grant
 

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