High placement and levelling accuracy flip-chip assembly for MOEMS

MOEMS micromirror device technology is becoming more important in the effort to develop cost-effective nxn optical switches for next-generation fiber optic networks. Although there are a variety of fabrication and assembly methods available, most are complex and costly. Using established flip-chip assembly techniques to perform device transfer can greatly simplify the assembly process. For this project, a high-accuracy device bonder is proposed for transfer of optical micromirror devices from one substrate to another. The same technique can be applied to individual devices. or on the wafer level. A high-accuracy device bonder is used for, placement and in-situ bonding. The device bonder is capable of achieving 1 mum post-bonding accuracy in x, y and z axes. Levelling accuracy on the order of microns for a 200mm wafer ensures that the optical paths are correctly aligned. In-situ bonding also ensures that the levelling accuracy is maintained for the final device. Prior methods which use the self-levelling effect of solder bumps in a mass reflow type of operation can result in an unacceptable shift in the parallelism, ruining the device's optical performance. Using a high-accuracy device bonder, devices can be successfully transferred using a flip-chip method. The x, y and z placement is accurate to within 1 mum, and even less in some cases. The 1 mum accuracy is sufficient to ensure that optical paths align to waveguides which are subsequently used to align to a 9mum singlemode fiber core. This method of MOEMS transfer reduces the complexity of the transfer process. Use of existing flip-chip placement and bonding techniques speeds the development cycle of MOEMS devices. The flip-chip assembly method is a cost effective and simple method for transfer of MOEMS devices. This method is enabled by a high-accuracy device bonder which is used for 1 mum accuracy placement and in-situ bonding.