Deformation mechanism of glass microlenses and microlens arrays in contactless hot embossing

Contactless hot embossing has been demonstrated to possess the potential for cost-effective production and precise mounting concepts in fabricating glass microlenses and microlens arrays due to the reduced difficulty of mold fabrication and the possibility of obtaining self-aligned assemblies. This study aims to provide experimental evidence for understanding the forming mechanism of glass microlenses and microlens arrays in the contactless hot embossing process. The effects of process parameters, diameter and position of the micro-holes, hole diameter, and pitch of the micro-hole array mold on the filling deformation of glass in contactless hot embossing were comprehensively investigated. It is found that placing the micro-hole farther away from the mold center renders decrease in both filling height and tip curvature but increase in the eccentricity of the embossed glass microlens. As a result, the formed glass microlens array shows a nonuniform distribution of filling height and tip curvature. Furthermore, reducing the pitch of micro-hole array mold can significantly improve the uniformity of formed microlens array. Based on these experimental results, the forming mechanism of microlenses and microlens arrays in contactless hot embossing process is summarized. Finally, a glass microlens array with decent uniformity in the center area was hot embossed by using a SiC micro-hole array mold.