Low Temperature Full Metal Interconnect Using Supercooled Liquid Metal Solder Microcapsules

Supercooled liquid metal microcapsules are a disruptive technology that simplifies circuit board assembly. Forming full-metal interconnects of lead-free solder alloys without high-heat processes avoids thermal damage to components and materials or quality issues caused by coefficient of thermal expansion mismatch. The technology encapsulates RoHS compliant solder alloys inside a nanofilm that keeps the metal in a metastable supercooled liquid state at ambient temperatures. Metastability is maintained by a core-shell particle architecture. 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 interconnects technology invented by SAFI-Tech is overcoming reliability and processing issues of conductive adhesives while enabling the creation of full metal interconnects at low processing temperatures. The feasibility of this new product is showcased in this presentation where SAFI-Tech takes supercooled liquid metal microcapsules made from BiSnAg solder, screen-prints conductive pads, and then solders passive components at 110°C. This temperature is more than 50 degrees C lower than traditional reflow temperatures for this alloy and enables the soldering of a variety of electronic devices previously not possible. This SEMI-Flex funded product will create a drop-in replacement solder paste formulation that can be reflowed at reduced temperatures to form reliable and electrically conductive interconnects between rigid and flex circuits.