Hermetic sealing of microelectronics packages using a room temperature soldering process

This paper describes a process which uses a multilayered reactive foil to hermetically seal microelectronic packages. The foil is comprised of thousands of nanoscale layers of elements with large negative heats of mixing, such as Al and Ni. When the reaction is activated in the foil using a small electrical or thermal stimulus, the heat generated melts the adjoining solder layers and permanently joins the package lid to the base. The seal is achieved without exposing the components to high reflow temperature. RNT has used this process to create a hermetic seal between an Au-plated stainless steel lid and Au-plated stainless steel base. We show that helium leak rates of less than 1 × 10^-10 atm-cc/sec can be achieved by using this method. This process provides an attractive alternative to more expensive methods such as laser welding and eliminates the need for costly fabrication equipment.