Lower Temperature Soldering Using Supercooled Liquid Metal

ABSTRACT Lead-free solder metal alloys can be formed into supercooled liquid metal microcapsules and used to create solid full metal interconnects at dramatically lower processing temperatures. These alloys can be made with or without bismuth. The technology encapsulates known and established RoHS compliant solder alloys inside a thin oxide/organic shell nanofilm that keeps the metal in a metastable supercooled liquid state at ambient temperatures. The thin oxide/organic shell can be mechanically broken or chemically dissolved to release the liquid metal that then rapidly solidifies all without requiring heat. The novel solder interconnect technology avoids thermal damage to components and materials, or quality issues caused by coefficient of thermal expansion mismatch.