Joining Methods for Glass Based Microdevices

Abstract

Adhesive bonding of glass parts is a very fast, simple and inexpensive joining technique. It can be used to join glasses to all materials and is very flexible [341]. However, the disadvantage of adhesive bonding is the necessity of an additional material, i.e. the adhesive which often results in a low thermal and chemical stability of the bond. Furthermore, adhesive joints tend to have limited long term stability. Three main types of adhesives commonly used for the joining of glass devices in the microtechnology are UV-curable adhesives, epoxy-based adhesives and cyanoacrylates. UV-curable adhesives are the most widely used adhesives for glass joining. Because of their low viscosity these adhesives can simply be spread over the surfaces. The parts to be joined can be easily positioned and fixed because the adhesives cure only if exposed to UV light. However, UV-curing requires that the material is sufficiently transparent for UV light, which is the case for glasses. The curing of epoxy-based adhesives is either induced thermally or chemically or occurs as a result of combined action. Epoxy-based adhesives can be one- or more-component systems. The viscosity of epoxy-based adhesives is rather high, which causes problems if structured surfaces are to be bonded. The curing of the adhesives starts either directly after the mixing of the components or during thermal heating.