Replication assessment of surface texture at sub-micrometre scale

Precision molding and micro injection molding (μIM) have been the main replication technologies allowing for a rapid reduction of the dimensions of the products and, consequently, for the realization of new advanced micro and nano systems. Such miniaturization in the manufacture of polymer micro-parts and parts with micro and nano surfaces is still in progress and requires new specially developed solutions in all the steps of injection molding processes [1]. The achievement of a full surface replication of the tool insert component, when molding the polymer melt, is essential in advanced μIM technology [2]. A replication process requires reproducing a master geometry by conveying it to a substrate material. It is typically induced by means of different energy sources (usually heat and force) and a direct physical contact between the master and the substrate. Furthermore, concepts of advanced products may be founded on combined processes and process chains, including large variety of materials (mainly polymers, glass or metals) and different dimensional scales. Hence, it is particularly critical when dealing with increasingly small dimensions in micro and nanostructured surfaces. In addition, because of the replication nature of molding processes, the required specifications for the manufacture of micro molded components must be ensured by means of a metrological approach to surface replication and dimensional control of both master geometry and replicated substrate [3]-[4]. Therefore, a detailed knowledge is necessary of not only absolute dimensions and geometrical quantities, but also of the measurement uncertainty, which is a decisive parameter to deal with the quality assurance of micro and nano manufactured components [5].In this context, the quality of the achieved surface texture replication was assessed by the replication fidelity, i.e., comparing the produced parts with the tool used to replicate the geometry. Furthermore, the uncertainty of the replication fidelity was achieved by propagating the uncertainties evaluated for both masters and replicas. Finally, despite the specimens investigated were made of thermoplastic polymers, the techniques employed are general and can be used to describe any kind of material of the replicated substrate.