A Resealable Hermetic Packaging Technique for Silicon Microfluidic Devices

Recent efforts have lead to the development of a silicon microfluidic cooling device known as the micro-Columnated Loop Heat Pipe (μCLHP) [1] [2] [3] . The μCLHP, like a traditional heat pipe, utilizes phase change of a liquid to rapidly draw heat away from a concentrated hot spot. Proper hermetic packaging of this device is critical for the reliable testing of the recirculating fluid. This work presents a novel approach to filling and hermetically sealing the μCLHP. A miniature valve (Beswick M3SV-N) is bonded to the silicon fill ports of the μCLHP. The use of a resealable valve, as opposed to a permanent sealing method, allows the device to be filled, sealed, and then evacuated for testing with different fluids and at multiple pressures. Building on work by Murphy [4], the fill ports on the μCLHP were metalized with a 10nm Cr - 200 nm Ni - 10 nm Au stack. Then a lead based solder was used to bond the stainless steel adapter to the metalized layers. Hermeticity testing of devices sealed using these miniature valves demonstrated average hourly percent weight losses between 0.170 % – 0.821 %. While this bonding method has been developed specifically for the μCLHP, it is broadly applicable to most ceramic microfluidic devices, especially those fabricated from silicon and glass. Due to the time intensive manufacturing process of microfluidic devices made from these hard materials, a novel, robust, resealing method that allows reuse of a single silicon microfluidic device for multiple test conditions is highly desirable.