Insight Technology – Track Width & Isolation Gap Tolerances

Definition of Tolerance for Manufacturing

Manufacturing tolerances are the amount of variation that is allowed in a measurement or other characteristic of an object.

Ref: Collins English Dictionary

We continue with our series on Understanding Tolerances on a PCB with our latest guide:

Track Width & Isolation Gap Tolerances.

Track widths and isolation gaps are important as they define the maximum current load, impedance values and generally electronic signal integrity for a PCB.

The values defined in the CAD system based on a “Right First Time Design for Manufacturing” and the required functionality of the PCB.

One thing that must be remembered is that the track widths and isolation gaps are linked, you cannot have one without the other.

If the track is over etched (smaller track width) then the isolation gap is increased, if the track is under etched (larger track width) then the isolation gap will decrease.

In the worst-case scenario, under etching may result in the copper between the tracks is not be fully etched away resulting in short circuits.

But the etching process is only part of the story and as a manufacturer we must manage all the factors that influence the final track width & isolation gap, as listed below.

  • Base Copper Thickness.
  • Type of Imaging Process (Di vs Conventional).
  • Copper Balance.
  • The Etching Process.

We produce all our boards according to the IPC-A-600 Acceptability of Printed Boards  (Industrial products).

To read more and see our video on how and why these factors influence the final track width & isolation gap on a PCB simply click on the button below.