Replication of micro/nano-scale features by micro injection molding with a bulk metallic glass mold insert

The development of MEMS and Microsystems needs a reliable mass
production process to fabricate micro components with micro/nano scale features. In
our study, we used the micro injection molding process to replicate micro/nano scale
channels and ridges from a Bulk Metallic Glass (BMG) cavity insert. High density
polyethylene (HDPE) was used as the molding material and Design of Experiment
(DOE) was adopted to systematically and statistically investigate the relationship
between machine parameters, real process conditions and replication quality. The
peak cavity pressure and temperature were selected as process characteristic values to
describe the real process conditions that material experienced during the filling
process. The experiments revealed that the replication of ridges, including feature
edge, profile and filling height, was sensitive to the flow direction; cavity pressure
and temperature both increased with holding pressure and mold temperature;
replication quality can be improved by increasing cavity pressure and temperature
within a certain range. The replication quality of micro/nano features is tightly related
to the thermomechanical history of material experienced during the molding process.
In addition, the longevity and roughness of the BMG insert was also evaluated based
on the number of injection molding cycles.