Comparing fusion bonding methods for glass substrates

Glass bonding is often necessary in microfluidic, nanofluidic and MEMS applications. Fusion bonding is a popular method in which glass substrates are permanently bonded using chemical treatment, low pressure and annealing. This project investigates a range of bonding methods and measures the bond strength. Float glass substrates were chemically cleaned and prepared using four different methods (Ethanol Rub, Ethanol Rub + NH₄OH, piranha + NH₄OH, and piranha + HCl + NH₄OH), pressed together by hand, and placed in the oven at 400 °C for 10 h. Bond strength was assessed using compressive shear stress. It was determined that the piranha + HCl +NH4OH produced the strongest bond. All methods produced satisfactory bonds and the simplicity and safety of a simple Ethanol rub means it should be considered whenever possible.