Comparison of embossing properties of polycarbonate and polystyrene for deep microstructures

Low cost and high-volume production has been identified as the successful route for commercialisation of many Micro Electromechanical system (MEMS) devices. Hot embossing, being a simple and cost effective method of replication of many micro- components in polymeric substrates, has been recognised as the most viable process using laser machining and consequent electroforming. Recently, Polycarbonate (PC) and Polystyrene (PS) are increasingly used for polymer microreplication mainly because of their suitable material properties such as Glass transition temperature (Tg), mechanical stability at high operating temperature and pressure conditions, bondability with other materials especially in the fabrication of multi-layered structures. Hence, in this paper, we present the results of our investigations on the effect of pressure and temperature during microembossing of different features into Polycarbonate and Polystyrene. The hot embossing experiments were carried out on specially designed home made equipment. These experiments demonstrated that polystyrene with lower Tg (∼100ºC) is more suitable for the replication of relatively finer features. The higher glass transition temperature of PC (∼150ºC) necessitates extra heating time, thus extending the replication process time and increasing thermally induced stresses in the embossed material. The effect of variation of temperature and pressure on the replication of similar features in the polycarbonate and polystyrene is discussed in detail.