Abstract
Double-side replication of polymer substrates is beneficial to the design and the fabrication of 3-demensional devices. The ultrasonic embossing method is a promising, high efficiency and low cost replication method for thermoplastic substrates. It is convenient to apply silicon molds in ultrasonic embossing, because microstructures can be easily fabricated on silicon wafers with etching techniques. To reduce the risk of damaging to silicon molds and to improve the replication uniformity on both sides of the polymer substrates, thermal assisted ultrasonic embossing method was proposed and tested. The processing parameters for the replication of polymethyl methacrylate (PMMA), including ultrasonic amplitude, ultrasonic force, ultrasonic time, and thermal assisted temperature were studied using orthogonal array experiments. The influences of the substrate thickness, pattern style and density were also investigated. The experiment results show that the principal parameters for the upper and lower surface replication are ultrasonic amplitude and thermal assisted temperature, respectively. As to the replication uniformity on both sides, the ultrasonic force has the maximal influence. Using the optimized parameters, the replication rate reached 97.5% on both sides of the PMMA substrate, and the cycle time was less than 50 s.
Highlights
Thermoplastic polymer materials play an important role in Micro-electro-mechanical system (MEMS) devices and have been investigated over the past decade
There are two methods to bury the thermocouples, the first one is with the same depth below the surfaces of polymethyl methacrylate (PMMA) substrate, and the second is to make the thermocouples on the lower surface buried a little deeper
Double-side ultrasonic embossing was studied in this paper, and silicon molds were applied in ultrasonic embossing
Summary
Thermoplastic polymer materials play an important role in Micro-electro-mechanical system (MEMS) devices and have been investigated over the past decade. They are widely used in the fields of micro-optics [1], lighting [2], sensors [3], micro total analysis systems(mTAS) [4] and artificial organs [5], etc. The fabrication methods mainly include injection molding, hot embossing and thermoforming [9]. Compared with other replication methods, injection molding has the shortest cycle time. The cycle time is about 1 min, which meets the mass production requirements. The molten polymer needs to flow through a long and narrow cavity before filling into the microstructures and it is difficult to fabricate fine microstructures
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