Controlled solder interdiffusion for high power semiconductor laser diode die bonding

High power semiconductor laser diodes and optical power amplifiers have important roles in solid state laser and optical fiber pumping, optical storage and recording, and can serve as efficient sources for medical and display applications. These high power devices must be mounted in the epitaxy-side down configuration for good heat transfer and so require a well-controlled, high yield, void-free, die attach method. We have developed a method which consistently yields absolute thermal resistances of 1.5°C/W (±4%) on tapered angle facet semiconductor optical amplifiers and specific thermal resistances of 0.004 K·cm²/W for lasers and optical amplifiers mounted on oxygen-free high conductivity (OFHC) copper heatsinks. Our method has wide process margins, exhibits excellent yield (>95%, N=30) and repeatability, relaxes the requirements for highly polished heatsinks, and is well suited for laser die attach to heatspreading diamond submounts or advanced composite materials