It has been my experience that it depends on the starting copper wt. and how much plating is being applied after drilling.

* Rogers 4003 .032 thick 1/2 oZ. plated up to 1 1/2 oZ. can be spec'd, this will give you a total finished conductor width

tolerance of .0015 (mils)

* Rogers 4003 .032 thick 1 oZ plated up to 2 oZ. can be spec'd, this will give you a total finished conductor width tolerance of

It is important to note that these types of PCB's should be marked as "critical etch" on the fabrication drawing.

My experience is with small QTY. There was no difference in pricing from unspecified tolerance. If you are interested I can

give you information for a PCB fab shop that you can work with on this.

Here is one I have recently been hit with. My current incarnation as an engineer is with and RF component manufacturer. We recently hired a new design engineer, he uses embedded inductors in the pcb fab. The prototypes, produced with a board mill, worked fine. The pilot production boards had a parametric problem. We traced it to a reduction in the inductor trace width due to the etch factor (currently unspecified on the fab drawing.) Due to size constraints the inductor uses .004" traces with .004" separation. So here is the question; how do I specify the acceptable variation on a specific feature of the PCB, and what is reasonable (i.e. how tight can I spec. trace variance without driving the cost out of sight).