Static cracking due to electro-static discharge during glass substrate transferring system in vacuum

Glass substrates for flat panel displays are insulating materials that can generate and maintain high levels of frictional charges that pose a risk of electrostatic discharge (ESD) damage, and the glass transfer process also generates a lot of static electricity. When glass is transported, a frictional charge is generated on the bottom of the glass substrate by the transport roller in contact with the glass, and is affected by the material of the roller, acceleration/deceleration, and maximum speed. In this paper, we would like to introduce a case of electrostatic discharge (ESD) failures that occurred across the glass from the bottom of the glass to the metal lines on the top of the glass during the vacuum transport process. We also addressed the process of failure analysis to find the cause of this ESD failure and the measurement of electrostatic charges at the point when the glass substrate stops moving and ESD events occur. In the end, this failure was improved through the speed and deceleration conditions of the roller, which are expected to affect the friction charging characteristics, but there was little difference in the electrostatic charging according to our experiment. In order to clarify the ESD energy within the glass, the test to the vacuum degree of the chamber, glass thickness, the deceleration condition of the rollers, and the metal layout on the top of the glass will be needed in the future.