Our experience says that you must identify the desired line width and 
     tolerance on the drawing.  Even if the artwork provided is stated as 
     representing the nominal desired finished width, you must identify 
     specific line widths and tolerances (helps inspection) for critical 
     conductors.  In practice, this call out is usually only required in a 
     couple of locations to insure desired line widths.  It may also be 
     prudent to state that the measurement shall be taken from the bottom 
     or top of the trace.
     
     Andy Pedersen
     Harris Corp.
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: [TN] DES: IPC 6012 Trace width tolerance - RF Applications
Author:  "TechNet E-Mail Forum." <[log in to unmask]> at smtp
Date:    4/2/98 4:05 PM


This message is pointed to those of you involved in RF circuitry I think. 
     
The IPC-6012 specification for trace with tolerance of ±20% is coming under 
fire here. Typically what can most PCB fabricators hold for trace width 
tolerance regardless of what IPC says. How do other RF designers specify 
trace width tolerances in critical circuits.
     
Steve Collins
PCB Design Supervisor 
     
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