Problem
Our customer was using a LCD with a touch screen in a hand held product. The touch screen manufacturer claimed a long life cycle for the display but offered no test data to support the claim. Several of the touch screens in the hand held units had failed while in service, so the customer asked Alpha Omega to produce an automated tester to determine the actual touch screen life cycle.
Solution
The touch panel manufacturer would not provide operating pressure requirements necessary to perform the life cycle tests. We positioned a standard test stylus tip over an operating unit and raised and lowered the stylus to generate a wide variety of test forces. This allowed us to determine the range of forces necessary to ensure reliable operation of the touch panel.
We adapted an earlier pneumatic button tester to provide the control for the new machine. A small array of pneumatic cylinders was arranged on an X-Y linear motion system to allow the array to be positioned over all test points on the touch panel. The operating force and duration for the pneumatic cylinders was calibrated using a load cell. The unit under test was positioned under the stylus array in a machined holder. The stylus array was moved under program control to allow all points on the touch panel to be tested.
Results
The tester quickly demonstrated that the touch panels failed far sooner than the manufacturer's claimed operating life. Our customer obtained sample touch screen from several other manufacturers and used the tester to find a product that actually met the required performance. This gave our customer confidence that the product would surpass the warranty life time.
