Fabrication and Numerical Design of MEMS Based Silicon Micro-Jet Array Impingement Coolers

摘要

With the increase in heat fluxes generated by fast and compact electronics, thermal management is becoming a challenging task. In some of these applications, air is preferred as a coolant. Even though it has a poor thermal conductivity, it has been shown that air could be used efficiently as a coolant. One of these cooling methods where air can be efficiently utilized is jet impingement. A MEMS based micro-jet array (MJA) air impinging device has been numerical simulated, fabricated, and tested. Computer modeling was used to predict the performance of the designed MJA cooler. Navier-Stokes (NS) equations with incompressible flow were solved using an implicit procedure. The temperature contour and velocity vector visualization diagrams are created to visualize the performance of the designed MJA cooler. Computer modeling enables us to explain the unexpected flow phenomenon and yield valuable information on the flow and heat transfer characteristics in the MJA cooler. Three 625-micron thick wafers were micromachined from both sides using reactive ion etching (RIE) to form the parts for the micro jet array cooler. An inlet hole of 7 mm, and 181 micro-jets of 250 microns within an area of 17 by 17 mm form the air distribution part of the cooler. Micro-channels were formed on the cooling surface to enhance the cooling efficiency. A measurement set up was developed, where thin film heater and sensors are directly fabricated on the front side of thermo mechanical test chip, which gives more accurate surface temperatures of the cooled surface. By using double-sided etching, the number of layers and bonding interfaces could be reduced. A value of 0.165W/cm{sup}2K for the heat transfer coefficient at the input power of 70 Watts and the air velocity of 21m/sec has been measured for this MJA cooler.