Metallic Interconnection Technologies for High Power Vertical Cavity Surface Emitting Lasers Modules

Highly reliable power VCSEL (Vertical Cavity Surface Emitting Lasers) array systems with an optimized optical output require a plan parallel assembly for a homogeneous radiation and an advanced packaging design to ensure good heat dissipation and an overall reliable performance. The aim of this study is to evaluate if metallic interconnection technologies like soldering and silver sintering can meet these requirements. Therefore, GaAs dies with VCSEL arrays of more than 2000 single lasers were mounted on substrates by soldering using AuSn20 and SnAg3 solder as well as by applying pressure assisted silver sintering. The samples were analyzed using ultrasonic microscopy (C-SAM), X-ray microscopy and 3D laser profilometry. Cross-sections of selected samples were made and analyzed using light- and scanning electron microscopy (SEM). Soldered and silver sintered samples were subjected to thermal cycling between -55°C and +125°C to validate the reliability of the metallic interconnects. Furthermore, it was tested, if it is possible to assemble a DCB onto a micro channel water cooler made of copper by pressure assisted silver sintering in order to enable an advanced heat transfer of the high power VCSEL module.