JF,

If you are specifying notes on your drawing you should know your minimum current carrying requirements and determine the cross-sectional area needed based on conductor width and thickness.  You should know the minimum designed conductor width and also specify the minimum acceptable conductor width on the drawing.  Understand that when you specify 1 oz finished that this is a weight and not and actual thickness but it can be converted to a thickness.  Also understand there are fabrication or processing allowances for the copper supplier and the board manufacturer.  As someone else mentioned, if you are dealing with rigid boards, get a copy of IPC-6012 and understand what you will be getting from a board manufacturer based on the class of product.

I go with the practice of specifying the starting copper weights in a stackup detail on the fabrication drawing and know what the minimum copper thickness will be based on the Class, i.e., 1, 2 or 3.  If you are looking for around 1 ounce copper finished, understand that on internal layers if you specify starting with 1 ounce copper the minimum thickness can be at 24.9 µm or .00098" regardless of Class.  On external layers I would specify to start with 1/2 ounce copper knowing the minimum thickness can be 33.4 µm or .001315" for Class 1 & 2 or a minimum thickness of 38.4 µm or .001512" for Class 3.

Regards,

Scott A. Bowles
Staff Engineer - Printed Circuit Designer IV
Engineering Services
L3 Fuzing & Ordnance Systems
3975 McMann Rd.
Cincinnati, OH 45245
Office: 513-943-2483
Mobile: 513-208-9009



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of JF
Sent: Thursday, February 28, 2013 11:45 AM
To: [log in to unmask]
Subject: [TN] Notes in PCB Fabrication

Hello All!

I'm having a curious note in a fabrication drawing and I would like to know if it makes sense.

"1.0oz FINISH (0.5oz COPPER + 0.5oz PLATING)"

And somewhere else in the notes, ENIG is specified...

Ideas?

JF

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