Hechong - 

As reported previously, there is no "one size fits all" for line width.? Previous post answered some of the electrical property and heat rise caluculations.? 

From a fabrication standpoint, the critical parameter is "how thick is the copper of this layer"??? 3.5 mils is easy in 5 micron and 9 micron (0.2 and 0.35 mil foil).? It is OK in half ounce 17 micron (0.7 mil) foil.? Good shops can do it in one ounce 35 micron (1.35 mil foil).? It is state-of-the art in two ounce foil!!!

Then, are the traces inner or outer layer?? Inner layer typically have the best resolution as there is only photoresist and etching steps involved in fabrication.? Outer layers may have more copper plated and use a metallic plated etch resist instead of organic photoresist.? 

One source of capabilty information is the PCQRR (Printed cricuit Capability, Quality, and Relative Reliability) team for IPC.? Their reports show all this against the best, good and average printed circuit fabricators. 

Denny Fritz
MacDermid, Inc. 


-----Original Message-----
From: Cong He <[log in to unmask]>
To: [log in to unmask]
Sent: Mon, 16 Feb 2009 9:07 pm
Subject: [TN] PCB'S minimum line width



Hi all,

 I want to know that how much is the minimum  line with when you usually 
designe the PCB? 
The surface and the inner sides?

And what does that affect except the process capability of the PCB 
factory?

Will 3.5mil be OK?


Hechong

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