Jack,
     
     The chamfered bend if designed correctly is designed to provide a 50 
     ohm impedance around the bend (Touchstone can calculate it and also 
     has the formula included in the documentation).  The general rule of 
     thumb for curved traces is that you want the curve radius to be 3 to 4 
     times the width of your trace.  You can see why the "compensated 
     bends" are preferrable.
     
     I'll bet 50:1 that the tin coat spec is outdated (or was a misnomer) 
     and that your company has been receiving solder coated (Sn63/Pb37) 
     boards.  Tin can be plated up on the board by many PCB suppliers but I 
     don't know why you would want to do it.
     
     In return, I hope you can tell me if you know of anyone with 
     experience using no-clean flux with RF board assemblies and whether 
     there are any problems doing this.  I have heard of the flux becoming 
     conductive at high frequencies.
     
     Frank Hinojos
     Product Engineering Mgr.
     Watkins-Johnson Co.

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