Universal solders for direct bonding and packaging of optical devices

For optical packaging, there is a need to directly bond non-solderable materials such as oxides, nitrides, borides and fluorides, which are very difficult to wet/bond with low melting point solders, for example, at ∼150 °C or below. In this research, we describe new Pb-free universal solders with low melting point of 140 °C or below by doping with a small amount of rare-earth elements, especially inexpensive mischmetals, which allow direct and powerful bonding onto the surfaces of various optical and electronic devices. The microstructure of the solder bonds is described, and their potential applications for passive and active optical components assembly are discussed.