Good point! I agree on the linewidth tolerance issues. How about layer counts higher than 10 layers? They get real fun to drill when all internals are comprised of HTE copper. 1/2 oz is far more easier to drill with all that accumulated copper. As circuit density increases and linewidth decreases, the 1/2 oz copper will be vital to hold required critical linewidth tolerances. Like .004".004" (Trace/Space) on dual stripline trying to hit 50 Ohms. (That ones fun! Especially when the material(s) tolerance window gives you basically +/- 6 ohms) Groovy ______________________________ Reply Separator _________________________________ Subject: FW: Half ounce internals Author: [log in to unmask] Date: 2/16/96 8:27 PM One argument for using is 1/2 oz on internal layers is a reduction in line width variation. There are very few PWB suppliers that can supply supply a 4 mil line +/-20% on 1oz copper. In addition, mixed copper thicknesses on a layer pair [i.e. lyr 2 (top)and lyr 3 (bottom)] result in reduced yields. I also don't believe there is anyone who can honestly quote a 3 mil line +/-20% on 1oz copper and maintain the specification. nwbluez ---------- From: TechNet-request To: Technet Subject: Half ounce internals Date: Friday, February 16, 1996 4:40PM A strong consideration for not using 1/2 ounce copper on internal layers, is that you only half the width of copper to make a connection at the barrel of plating. Possible problems. Be careful. May not be reliable. Norm Einarson