Adhesive Bonding of Glass Parts

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. 

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. 

The properties of the adhesives can be modified by the addition of metal or other powder fillers. Electrically and thermally conductive adhesives 

The successful application of the adhesives is a major problem in the microtechnique [22]. The amoimt of the adhesive used and its viscosity should be optimised with respect to surface area and the shape of the surface. Often a pulsating pressurised capillary system is used to apply tiny amounts of adhesives [22]. Overflow trenches allow for the removal of adhesive that is not required to bond the surfaces. These trenches help to protect the geometrical fine structures against unintentional filling by the adhesive. 

The application of adhesives can also be assisted by various other means. For instance, it is possible to use spaces with a predefined depth to dose exactly the amount of glue required. An adhesive with a low viscosity will penetrate these spaces under capillary action. This technique is called capillary space adhesive technique and is very often used in the microtechnique for example to join microvalve systems by adhesive bonding [341]. The fabrication of a micropump and the optimisation of microstructures for the adhesive bonding process are described in the literature [339,340]. 

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