Measurement of surface tension of epoxy resins used in dispensing process for manufacturing thin film transistor-liquid crystal displays

This paper presents an inverse method for measuring the surface tension of the epoxy resins used in the dispensing process for manufacturing TFT-LCD based on droplet images. A direct method, which is capable of predicting the profile of an axisymmetric liquid droplet, is developed, and then the direct method is incorporated with a droplet imaging system to build up a measurement system for determination of the surface tension of the epoxy resins. When applying the surface tension measurement method, one only needs to give the density of the liquid and identify the geometric parameters of the liquid droplet, such as the droplet volume and the contact angle, through the imaging system. This approach has been used to determine surface tension of various epoxy resins. Finally, for testing the accuracy of the approach, some commonly used fluids are tested. Results show that the approach leads to satisfactory accuracy.