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Assessing the Accuracy of Thickness-Measurement Tools

(April 2004) posted on Tue Apr 13, 2004

Discover what tools and procedures lead to the most accurate measurements for screen printing.

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By Fernando Zicarelli

By Fernando Zicarelli, Dynamesh Inc.

Mesh thickness and emulsion-over-mesh (EOM) level both play a critical role in metering the thickness of any coating deposited with the screen-printing process. A printer's ability to predict the deposit thickness that a particular mesh and stencil combination will deliver depends primarily on the accuracy and reliability of mesh- and stencil-thickness measurements. Critical electronics applications, for example, require tightly controlled deposits of conductive materials to ensure that printed circuits provide the correct electrical properties (conductivity, resistivity, etc.). Without accurate mesh/stencil thickness measurements, achieving the ideal coating thickness becomes a time-consuming exercise in trial and error.

Several years ago, I began a study to compare thickness variations in stainless-steel screen fabrics produced by four different mesh manufacturers. I measured meshes with similar thread counts and thread diameters from each manufacturer, then compared my results with measurement data they provided. What emerged were significant variations in mesh thicknesses among the manufacturers and between their measurements and my own. It became apparent that a statistical-control study was necessary to determine what combination of tools and procedures would deliver the most accurate thickness measurements.

First, I had to find out what measurement tools and methods each of the mesh manufacturers was using. I was not surprised to learn that each employed a different device, a different probe diameter, and a different measuring force. While the type of measuring device used didn't concern me, I believed that the differences in probe diameters and measuring forces could significantly alter the thickness values returned and focused my study on these two areas.

The discrepancies between the stainless-steel meshes was similar to what we, at Dynamesh, occasionally experience with customers who require us to provide mesh or precoated screens with exacting thickness tolerances. In several instances, we have provided mesh or coated screens to the specifications requested by customers, only to have the buyers report that the thicknesses did not match their specifications. Although our measurements said the thicknesses were correct, the measurement tools and techniques used by our customers were delivering different results.

While I acknowledge that it's important for mesh manufacturers to be aware of how their customers are measuring mesh and stencil thickness, I believe it's more important that measuring equipment and procedures for their use be calibrated and standardized for the screen-printing industry. Without universally accepted standards for measuring mesh and stencil thickness, measurement discrepancies will never end.


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