Elementary Mr. Watson: Navigating RF—A Glide Path Approach to Design Success
Designers Notebook: Layer Stackup Planning for RF Circuit Boards
Connect the Dots: Involving Manufacturers Earlier Prevents Downstream Issues
Estimated reading time: Less than a minute
Connect:
July 17, 2013
Connecting the Dots: Nothing's Perfect - Understanding Tolerance
by Jack Olson
Yes, nothing’s perfect.
We designers do our best to maintain accuracy, but the real world produces imperfections:
- Our CAD systems assume that a drill is perfectly centered in a round pad. It never is.
- We declare specific trace widths, but when we measure them on an actual board they are always slightly thinner or thicker.
- Multiple layers are perfectly aligned on our computer screens, but the fabricators can never quite manage to duplicate it. There will always be some misregistration.
- The board design is assumed to be flat, but boards in the final product can be bowed or warped.
- We designate some traces to be impedance controlled, but our measurements differ.
I could go on and on and on, but I think you see the point. As designers, we calculate exact numbers. We design with precision. Our CAD systems show us the ideal board. In the real world, however, nothing is so precise. The final product will vary from the ideal in one way or another, but hopefully in ways that are harmless.
Editor's Note: This column originally appeared in the May 2013 issue of The PCB Design Magazine.
Share on:
More Columns from Various Archived Columns
Slash Sheet Chaos: Is What You See, What You Get?Moisture in Materials: Avoiding Process Gremlins
Material Witness: Beat the Heat--A Non-Math Intro to Thermal Properties
Material Witness: Considerations in Using TC Materials for PWBs
Material Witness: Are Your Materials Up to the Challenge?
Material Witness: Thermal Oxidation of Materials, Part I
Material Witness: Thermal Oxidation of Materials, Part II
Material Witness: R.I.P. Speedboard C
Copyright © 2025 I-Connect007 | IPC Publishing Group Inc. All rights reserved.
Log in