Fabrication of Silicon Microchannel With Integrated Heater and Temperature Sensors for Flow Boiling Studies

Two-phase microchannel heat sinks are a promising solution to meet the requirements for cooling electronic components with high-density heat dissipation. However, their design requires a thorough understanding of flow boiling and pressure drop in microchannels. The channels described in this paper have been fabricated in silicon, with rectangular cross-sections ranging in hydraulic diameter between 0.62 and 0.1 mm, for studies of boiling in single channels. To facilitate visualisation, the top of each channel is covered with Pyrex 7740, predrilled for fluid inlet and outlet connections. Integrated tantalum resistors are located uniformly along the bottom of the channel for temperature sensing. Tantalum pentoxide and PECVD silicon dioxide (which also conformally coats the channel walls) are used to electrically insulate the sensor from any liquid in the channel. The heater is an integrated aluminium serpentine track on the back of the bottom wafer. The channel is etched down to the sensors on the bonded bottom silicon wafer using the Bosch process. The objective related to the development of these silicon microchannels is to achieve heat fluxes of 2 MW m⁻² with low, near-uniform wall superheat (by means of bubble triggering and artificial nucleation sites). Experiments will be carried out with mass fluxes varying from 100 to 500 kg m⁻² s⁻¹, using de-ionized water and an organic fluid as the working fluids.