A razor-blade test of the demolding energy in a thermoplastic embossing process

Abstract

We present a simple and quick test of the energy needed to separate a hot-micro-embossing mold from an embossed polymeric part. The test is an extension of the double-cantilever-beam, or ‘razor-blade’, test that has been widely used to determine the interfacial work of fracture of bonded pairs of semiconductor wafers. Our test extracts a single areal demolding energy that incorporates all the mechanical work done when separating the patterned mold–polymer interface. We have used the test to investigate dependences of the demolding energy on the relief and areal density of 150 µm diameter circular posts on a silicon mold. We find that demolding energy is approximately proportional to the areal density of the posts’ circumferences, and to the square of the etched depth of the posts. We propose a simple explanation for these findings. We have also used the method to compare three mold surface treatments, and find that amorphous silicon carbide and Teflon-like fluoropolymer coatings can reduce demolding energy by a factor of about 10, compared to a bare silicon mold.