PCB plating thickness

Hi, I have a general question about PCB manufacturer.

The fab house told me that when I use 1/2OZ copper foil (.7mil) on external layer, after plating additional copper for PTH, it goes to about 2.2mil. Is that true?

What are the minimum copper plating thickness? Does it depends on the PTH copper thickness? Thanks.

When we order PCBs, the standard we use is 0.5oz external copper plated up to 1.0 oz copper minimum. This seems to be fine for most applications. If you are pushing large currents around, you may want to increase the finished copper thickness.

I never asks what their minimum copper plating is. I suppose they could mask all the traces before plating the thru-holes. This would deposit copper on the holes but leave the surface traces the original thickness. I sure an extra cost would be involved.

I find that its best to just tell them what the finished product is supposed to be like and let them determine the best method of how to get there. Spec the minimum and maximum copper thickness of the external layers and let them worry about the processes needed to achieve it. The same applies to impedance. We gave up trying to spec the appropriate dielectrics and trace widths. Before starting the design, we request a stackup from the PCB fab shop for the impedances and layers we want. Then we just design to that.