Abstract
The replication of polymeric microstructures on a flat surface is not easily achieved by conventional injection molding, because of the required micro-dimensional control and the stringent tolerances of most applications. Moreover, the flow behaviour of melts in micro cavities remains not well understood and challenging. On the other hand, injection-compression molding is an established process for the manufacturing of optical storage media, like compact discs (CD) or digital versatile discs (DVD), with grooves and pits at the micro-scale. The difficulties arise mainly from two sources: lack of adequate filling because of premature freezing of features with very small thicknesses and excessive deformation during ejection due to high friction at the polymer-metal interface. In this work, a study is carried out to investigate the effect of process parameters on the replication of various microstructures on a flat disk using microinjection-compression molding. A commercial microinjection molding machine has been used in the study. Two optical grade polymers poly(methyl methacrylate) (PMMA) and cyclic olefin polymer (COP) were used in conjunction with various mold inserts to reproduce the embedded microstructures. The dimensions of the microstructures on the inserts and molded parts were measured with a confocal profiler. A transcription ratio was defined to assess the quality of the replication. The design of experiment (DOE) method was used to obtain correlations between the process parameters and the development of the microstructure during injection-compression molding.
References
Chen, C.-C. A., Kao, S.-C., “A Study of Two-stage Micro Injection Compression Molding Process for Diffractive Optical Lens”, Key Engineering Materials, 364–366, 1211–1214(2008)10.4028/www.scientific.net/KEM.364-366.1211Search in Google Scholar
Chien, R.-D., “Micromolding of bioship Devices Designed with Microchannels”, Sensors and Actuators A: Physical, A 128, 238–247(2006)10.1016/j.sna.2006.02.029Search in Google Scholar
Guo, J., et al., “Study of the Demolding Process – Implication of Thermal Stress, Adhesion and Friction Control”, J. Micromech. Microeng., 17, 9–19(2007)10.1088/0960-1317/17/1/002Search in Google Scholar
Heckele, M., Schomburg, W. K., “Review on Micro Molding of Thermoplastics”, Micromech. Microeng., 14, R1–R14 (2004)10.1088/0960-1317/14/3/R01Search in Google Scholar
Hetu, J. F., et al., “Three Dimensional Simulation of Injection Molding of Parts with Microstructures”, AICHE 2005 Annual Meeting, Cincinnati, Paper ID31792 (2005)Search in Google Scholar
Ito, H., et al., “Development of a Novel Transcription Molding Process to Fabricate Sophisticated Polymer Products with Precise Microstructure and High Transparency Applicable to Display Devices and Bio-Chips”, Int. Polym. Proc., 22, 155–165(2006)Search in Google Scholar
Shen, Y. K., et al., “Study on Optical Properties of Microstructure Lightguiding Plate for Micro Injection Molding and Micro Injection-Compression Molding”, Materials Science Forum Vol. 505–507, 229–234(2006)10.4028/www.scientific.net/MSF.505-507.229Search in Google Scholar
Shen, Y. K., “Comparison of Height Replication Properties of Micro-Injection Moulding and Micro-injection-compression Moulding for Production of Microstructures on Lightguiding Plates”, Plast., Rubber Compos. Process. Appl., 36, 77–84(2007)10.1179/174328907X171244Search in Google Scholar
Su, Y.-C., et al., “Implementation and Analysis of Polymeric Microstructure Replication by Micro Injection Molding”, J. Micromech. Microeng., 14, 415–422(2004)10.1088/0960-1317/14/3/015Search in Google Scholar
Tofteberg, T., et al. “Injection Molding of a Diffractive Optical Element”, Polym. Eng. Sci., 48, 2134–2142(2008)10.1002/pen.21154Search in Google Scholar
Tseng, S. C., Liao, C. L. “A Study of Processing Conditions on the Properties of Diffraction Optical Elements by Injection/Compression Molding Process”, Int. Polym. Proc., 18, 194–198(2003)Search in Google Scholar
Turng, L.-S., “Special and Emerging Injection Molding Processes”, J. Inj. Mold. Tech., 3, 160–179(2001)Search in Google Scholar
Wimberger-Friedl, R., et al., “Molding of Microstructures and High Aspect Ratio Features”, SPE ANTEC Tech. Papers, 539–543 (2003)Search in Google Scholar
Wu, C.-H., Chen, W.-S., “Injection Molding and injection Compression Molding of Three-beam Grating of DVD Pickup Lens”, Sensors and Actuators A: Physical, A 125, 367–375(2006)10.1016/j.sna.2005.07.025Search in Google Scholar
Yu, L., et al., “Flow and Heat Transfer Simulation of Thin-Wall Injection Molding with Microstructures”, SPE ANTEC, 602–606(2003)Search in Google Scholar
Zhao, J., et al., “Effect of Process Parameters on the Micro Molding Process”, Polym. Eng. Sci., 43, 1542–1554(2003)10.1002/pen.10130Search in Google Scholar
© 2009, Carl Hanser Verlag, Munich
