That says pretty much the same thing as your first statement.

The most likely way of manufacturing your board will be to drill a bunch of holes in it, prepare the holes for electroplating, plate copper in the holes which will also plate the faces of the panel, then etch the circuit patterns.  The plating on the outer layers is normally considered a side effect of the production process.  It causes etch resolution issues on very dense designs.  But sometimes, because it also reduces trace resistance (both electrical and thermal) is actually required.

It is common to specify at least 0.9 mils (23 microns) on the hole walls, which is a bit greater than your half ounce.  If there's enough slop in the specification, the fabricator will favor the hole wall criterion so the board is IPC compliant.  (Usually the same thickness deposits on the hole wall as gets plated on the outer layers).

The above explanation only holds for one particular way of building boards, but is the most common way to build cheap, plated boards.  Fabricators can be ingenious in figuring out alternate techniques to get whatever the customer specifies.

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of James Head
Sent: Thursday, February 28, 2013 11:59 AM
To: [log in to unmask]
Subject: Re: [TN] Notes in PCB Fabrication

They want 35 micron finished after plating.  Starting copper thickness of the pre-processed material is 17.5 micron and they want it plated up to 35 micron thickness total for the completed fabricated PCB.

James

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