Cover glass behavior in handheld device drop: modeling; validation and design evaluation

Cover glass reliability performance in a drop test is critical for handheld electronic devices. Handheld device drop test has limitations in measuring dynamic response on the device components which complicates the test control and data analysis. To supplement, design and improve the drop test we developed a full-scale modeling approach of a representative handheld device drop test. The device model includes all the major components such as: display, cover glass, rear cover, battery, printed circuit board/bracket, screws, adhesives, etc. The developed model explicitly simulates the device drop test, allowing us to measure mechanical parameters as function of process time for each of the device components. The numerical model was validated with the device drop test. In the current report we are focused on cover glass reliability. The cover glass performance was studied with respect to effects of adhesive materials on the rear side of the cover glass and the overall device rigidity. Using the model, we evaluated effects of each device component for the cover glass during drop. It was shown that significant cover glass reliability improvement in the device resistance against sharp indentation can be achieved if the glass is supported from the back side with a soft adhesive material. Key observations from these extensive modeling efforts have been discussed and the conclusions from the current study can serve as a general guideline to improve cover glass's reliability of a handheld device.