Interconnect Thermal Management of High Power Packaged Electronic Architectures
Cook, Jason Todd
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Packaged microelectronic technology provides an efficient means to connecting high performance chips to PCBs. As area array bump density increases, joule heating will play an important role in chip and interconnect reliability. Joule heating, in addition to chip heating can significantly reduce the clock speed and I/O while increasing noise, electromigration, and leakage power. Direct cooling of the solder bumps is a new innovative approach to removing heat from packaged high heat dissipating chips. This could be used in conjunction with top surface mounted thermal management devices to maximize heat removal. The solder bumps leave a small gap between the packaged chip and PCB, which can be utilized for incorporating a thermal management scheme. Since space is very limited, fans and conventional heat sinks are not practical solutions. Jet impingement presents a unique solution for cooling solder bumps. It has been shown that micro jets can effectively cool the top surface of laptop computer processors. They can also be used to cool the solder bumps and bottom of the chip. Micro jets are easily implemented into the PCB without compromising the electrical leads powering the chip. A prototype printed wiring board containing micro jets was built and a dummy plastic ball grid array packaged chip with a heating element embedded in it was attached on top. A mini compressor supplied the pressure and flow rates needed to push air through the micro jet holes. The pressure, flow rate, and temperatures were measured and analyzed. A numerical model was created based on the results of the experiments. Both the experiments and model show the effectiveness of interconnect cooling.