Localised laser joining of glass to silicon with BCB intermediate layer

Localised laser 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 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 ways to realize localised heating: one is by using scanning focused laser beam; the other is to use an axicon lens and followed a conventional lens to generate a focused ring. FE simulation indicates that provided sufficient heat sinking is provided at the rear of the device, both techniques result in very little in-process heating in the centre of the package, and this is confirmed by the use of a temperature-sensitive paint.