Replication Characterization in Injection Molding of Microfeatures With High Aspect Ratio: Influence of Layout and Shape Factor

In this work, both experimental study and numerical simulation were carried out to investigate the replication capability and flow behavior of polymeric melt inside microchannels with high aspect ratio. For this purpose, a mold insert with microchannels having different layouts (parallel and transverse to the main flow direction) and various cross sectional shapes (triangle, rectangle, and semicircle) was designed and fabricated. The filled length and surface morphology of the microfeatures molded under different conditions were characterized using scanning electron microscope and optical microscope. It was found that the cross sectional shape had clear influence on the filled length of the microfeatures, with a dependence on the mold layout. Moreover, serious hesitation of polymeric flows in microchannels took place in the transverse layout, which led to eccentric line defects. However, such defects were not observed in the parallel layout. At last, the specific mechanisms of how the cross sectional shape affected the replication capability and how the line defects in the microfeatures' surface formed were discussed. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers