Hi Raye, 

The final Cu thickness is what matters to us, not the starting Cu foil wt. I agree with your engineering dept that it makes no difference functionally whether the Cu is foil or plated. 

Sometimes, while we may spec 1/2oz + plating, our PCB suppliers may request to use thinner starting foil (1/3 or 3/8 oz) in order to achieve fine line/width traces or in certain via-in-pad applications where the board may see two plating cycles so they don't have to etch down as much material. It's not an issue for them to meet final overall conductor thickness if they achieve minimum thickness in the vias.

Just be aware that very thin foils (e.g., 1/4oz & 1/8oz) can have much lower peel strength performance and are more prone to damage during layup because they're so thin. 

Todd


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rivera, Raye
Sent: Tuesday, December 10, 2013 12:13 PM
To: [log in to unmask]
Subject: [TN] IPC-6012C Total Cu thickness

Hello technet gurus,

I have a question regarding total copper thickness for external conductors.

3.6.2.13 states only a requirement for total conductor thickness, that is foil + plating, and references table 3-12 for the appropriate values. There is no requirement for the foil thickness.
Table 3-12 also has a column with heading:

Absolute Cu Min. (IPC-4562 less 10% reduction)

Does that column heading constitute a requirement?   Would using a copper foil less than the stated minimum constitute a rejectable condition even if total copper thickness meets requirements?

Engineering  states that they only care about the total thickness from a functional point of view.

I ask this because I have a difference of opinion with a colleague on the interpretation of the standard.

Best regards,
Raye Rivera

QA Manager * Canoga Perkins
20600 Prairie Street * Chatsworth * CA 91311-6008
818-678-3872  * [log in to unmask]<mailto:[log in to unmask]>



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