By Assi Hansen, Isamu Miyamoto, Tiina Amberla, Yasuhiro Okamoto
One of the most employed material combinations in microtechnology is the glass-silicon pair. Since the huge growth of the microelectromechanical devices, sensors and micro-fluidic devices, bonding of this couple has become more and more critical issue. Many of these glass-silicon bonding processes, for example anodic bonding, fusion bonding and eutectic bonding, have reached their limits in terms of flexibility. In addition, high temperature and electrical field applied in the process can limit the application. Compared to conventional methods, local laser joining technique can provide many advantages, such as localized and flexible joining, non-contact manufacturing, high precision and repeatability, easiness and minimization of heat effects. The technique is based on the principle of transmission welding, where glass is transparent to the wavelength used and hence the laser beam passes through the glass wafer and is absorbed to silicon. As a result, silicon is melted and upon resolidification bonding is realized between the two substrates. Continue reading