Eutectic diffusion brazing process for joining aluminum laminae with macro- and microscale features.

摘要

Eutectic brazing occurs when two metals, such as aluminum and copper, react and diffuse together at a temperature lower than either material would melt separately. Commonly used in electronics manufacturing, this brazing method provides the basis for a new process of joining a laminated device with micro fluidic features. The proposed process overcomes the challenges of aluminum oxidation resulting from traditional diffusion bonding of aluminum laminae and does not require flux or caustic material pre-treatments. The process also protects surface geometries and avoids warpage, which is common with other higher-temperature joining processes such as welding.;This research provides a foundation for manufacturing multi-laminae, microfluidic, micro-feature devices in metals, especially aluminum. A reliable method of joining metal laminae could help make the manufacturing of these types of devices cost effective and reliable. These advantages will lead to faster rates of adoption of microfluidic micro-devices in industries such as pharmaceuticals, energy, food, and others.;This work combined laminae of aluminum alloy 6061 with copper foil interlayers to produce a milli-channel heat exchanger and reactor device. The devices contained overlapping coolant and reactant channel systems arranged perpendicularly within each lamina. Related work suggests that diffused joints are mechanically robust in contrast to the parent materials.;A laser micromachining center was used to trim the copper foil interlayers and a vacuum furnace hot press served to join laminae for the device. A reliable, leak-tight joining of the laminae occurred. Closed-loop argon testing at high operating temperatures verified the seal of the joint. The process repeatedly produced leak-tight, milli-channel heat-exchange and reactor devices.;The joining process is advantageous for joining complex milli- and micro-scale fluidic devices, such as a heat exchange and reactor device. Reliable joining takes place without application of fluxes, metal deposition, hazardous chemicals, or expensive cleanroom support.;This process will also benefit future microfluidics-related research and the integration of such technologies as arrayed milli-channel heat exchangers and reactor devices in industry. These devices enable modular scaling of production capacity, on-demand chemical processing, and higher purity products.