Machining Processes for Precision Molds

INTRODUCTION The continuing drive towards miniaturisation in a number of industries including semiconductor, optoelectronic and medical is stimulated by requirements which include enhanced functionality, performance and reliability, increased energy efficiency, a cleaner environment, improved healthcare, together with reduced costs etc. [1, 2]. Also, new products for fastgrowing industries like IT and electronics are increasingly implemented by using ever smaller and more complex modules. Because of the continuing demand for miniaturisation, complex surface figures with and without precise microstructures are becoming more and more important in technical applications. The high volume production of these parts requires reliable replication techniques by the usage of long term durable molds. Here, the challenge lies in the development of sufficiently precise and accurate, deterministic manufacturing processes for these molds. There is a large number of machining processes available for making precise mold inserts for e.g. out of metal-based, machinable materials like stainless steel or advanced, difficult-to-cut materials like semiconductors or ceramics. The applicable processes differ in the spectrum of machinable geometry, removal rate, achievable form accuracy, surface roughness and subsurface integrity. Therefore, hard milling and diamond machining are state-of-the-art machining technologies with high potentials and various opportunities for further process improvements that make these technologies more effective and flexible. Otherwise, precision grinding and polishing are limited in contrast to e.g. diamond machining, but harder materials like ceramics are only machinable by these bounded or loose abrasive precision processes.