Development and characterization of large silicon microchannel heat sink packages for thermal management of high power microelectronics modules

In this paper, the development of large-sized silicon microchannel heat sink (SMHS) packages for high power dissipation microelectronic modules is presented. The microchannel wafer was designed and fabricated through deep reactive ion etching on the 8" (100) wafer, which included 500 microchannels arranged in parallel and each channel possessed a depth of 400 mu m. The channel wafer was then bonded to a cover wafer to form the closed flow channel. Two wafer bonding techniques, gold diffusion bonding and bis-benzocyclobutene (BCB) bonding, were evaluated. Large thermo-mechanical stress was induced in the first technique, which may not be suitable for the large silicon wafer bonding. In the second technique, a BCB bonding process was successfully developed by producing a bonding layer of around 5 mu m of minimal stress and free from micro voids. Fluidic interconnects were formulated through the use of elastic room-temperature vulcanizing silicone material between the cover wafer and the metallic housing to minimize the bonding stress. Both hydraulic tests and thermal modeling were conducted for the fabricated SMHS packages. All the heat sink packages with BCB bonding passed hydraulic tests at around 60 psi at a flowrate of 41/min, whereas those with gold diffusion bonding were found to fail at a pressure of 2030 psi. The workability of the SMHS package for thermal management of high power microelectronics modules is demonstrated through a thermal model.