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Creating the Perfect Screen

(December 2007) posted on Mon Dec 03, 2007

The key to consistency in screen printing lies in the screen. Discover how discipline and science can help you fine tune the screenmaking process.


By Gordon Roberts

I was very lucky when I first got into this business. I landed a job early on with a company that was riding the exploding electronics boom of the early 1980s, and I cut my screening teeth in the demanding world of printed circuits. While most of my screen-printing contemporaries were still mastering spot colors and rudimentary process printing, a team of engineers was helping me figure out how we could bring our tolerances in line with the demands of the customer, who was always wanted denser circuitry on ever smaller boards. It was a great opportunity that would pay off handsomely—if we could just figure out how to get this highly variable process tamed enough to allow our guys to consistently print to the tolerances our clients demanded.

It soon became obvious that the key to consistency was the screen itself. If we could control the variables in the stencil, then the printing would generally take care of itself. I found myself spending a lot of time with a lot of expensively educated engineers in the murky dampness of the screen-prep area, where we systematically broke down every step of the process in our quest to understand how it all actually worked. In this month’s column, we will continue our journey through what is undoubtedly the most crucial element in any screenprinting process—stencil making—and learn to apply science and discipline to move closer to our goal of creating the everelusive perfect screen.

 

The frame as the foundation

The first thing we looked at was the frame. At the time, the norm in the circuit-board world was a rigid, aluminum frame with the mesh pretensioned using vacuum clamps and then glued into place. The printers hated using new screens. The image warped during the process, and it was a fight from the first pull to the last to keep the print aligned enough to complete the job. These problems improved a little as the screen hardened off with several uses, but it brought more problems for the printer to solve on the press. Snap-off was compromised, the screens had to be raised off of the substrate, the image began to distort when it was printed, and on and on. We immediately realized the brilliance of the retensionable screen frame and enthusiastically embraced the new technology.


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