Investigation on glass stress relaxation during precision glass molding for microlens array

Precision glass molding (PGM) is one of the most effective methods to produce microlens arrays with different sizes on glass. This paper is intended to fabricate glass microlens array using non-polishing glass preform to reduce costs. The internal stress variation and the surface roughness of formed glass piece are important to evaluate the quality of molded microlens array. The stress relaxation at molding temperature affects the glass internal stress variation during PGM, and the heating time influences on the surface roughness of molded glass piece. In this paper, the relationship between molding temperature and glass stress relaxation time is analysed by FEM simulation. Basic experiments on investigating the effect of heating time on the surface roughness of glass are conducted using Nickel Phosphorous (Ni-P) plating mold. Moreover, the method for microlens array using non-polishing glass preform are proposed based on simulations and experiments. The result shows that FEM simulation can predict the glass relaxation behavior at different temperatures. Glass microlens arrays replicated from the mold with low surface roughness are obtained by controling heating time during PGM using glass preform without polishing.