Laser assisted polymer bonding technology for advanced MEMS packaging

This paper presents the development of a laser assisted polymer bonding process using benzocyclobutene (BCB) for encapsulation of MEMS and other microscale sensor devices. The polymer rings were fabricated on capping substrates using the photosensitive BCB resin and photolithography and then bonded onto device substrates to form microcavities for MEMS packaging. A high-power fibre-coupled diode laser at the wavelength of 970 nm was used as the heat source for BCB bonding/curing in conjunction with novel beam forming optics that allows selective illumination of the substrates to be joined. Defect free bonding was realised in 10 seconds using laser power of order 50 W and 1 kgf of bonding force. The quality of the laser produced polymer bond was assessed using optical inspection and leak test and it was shown that it is as good as that formed using conventional hotplate based approach, but reducing the bonding time by a factor of ~100.