Localised laser joining of glass to silicon with BCB intermediate layer Available to Purchase

The use of a laser to provide localised heating is an ideal solution to the problem of packaging micro-electro-mechanical-systems (MEMS) whilst maintaining a low device temperature to avoid changes in temperature-sensitive materials. In this paper we present localised laser bonding of glass to silicon (normally used as the MEMS substrate) by using a fibre-delivered high power laser diode array to cure an intermediate layer of the thermosetting polymer Benzocyclobutene (BCB). In our experiments, we use two techniques to realise localised heating: one is by using a scanning focused laser beam; the other is to use an axicon together with a conventional positive lens to generate a ring focus. Finite Element (FE) simulation indicates that both techniques should keep the temperature in the centre of the package to approximately that of the ambient environment (300 K) during the process, confirmed experimentally by the use of a temperature-sensitive paint. However, the ring focus technique was shown to produce superior bonds.