Gold/Germanium Eutectic Alloy Foil (Light Tight) (Au88/Ge12)

Gold/Germanium Eutectic Alloy Foil (Light Tight) (Au88/Ge12) combines the precision melting behavior of a eutectic composition with the complete light-blocking performance of a defect-free foil. With a eutectic point near 356 °C, the alloy enables highly controlled brazing and hermetic sealing in optoelectronic and microelectronic assemblies. Its high reflectivity and total opacity to light make it indispensable in optical device packaging, photodetector modules, and sensitive sensor housings. The Au88/Ge12 composition offers excellent corrosion resistance, stable conductivity, and strong metallurgical bonding to gold- and nickel-coated substrates. Applications include sealing infrared detector windows, encapsulating photodiodes to prevent stray light interference, and precision MEMS packaging for vacuum integrity. The light-tight property ensures that no pinholes compromise optical isolation, making it critical in both industrial and defense-related photonics. In research, this foil is a standard material for studying interfacial reactions in gold alloys under sealed, light-excluded environments, reinforcing its status as a specialized but vital material in high-performance device fabrication.