Heat Transfer in Electronic Systems With Emphasis on Asymmetric Heating

and power dissipation level are assessed with emphasis on asym- For the past several years, the trend in electronic equipment design has been toward ever-increasing circuit speeds. Now it is common for response times of telecommunication equipment to be specified in terms of nanoseconds while, in high-performance data processing systems, the required response times are given in the picosecond range. The increase in circuit speed is facilitated by integration of circuit functions, circuit miniaturization, and higher-density packaging. Although the miniaturization of circuits results in decreased power dissipation per circuit, the power generation per unit volume, which is the important parameter in determining the circuit temperature, is actually increased due to the much higher packaging densities. The thermal problem is also compounded by the lower operating temperature re907 908 THE B E L L SYSTEM TECHNICAL JOURNAL, J U L Y - A U G U S T 1 9 7 3 quirements of integrated circuits. This gives rise to a challenging undertaking in thermal design. And yet a poor thermal design could possibly lead to complete failure or unreliable performance of equipment. Thus, it is imperative that a sound thermal design be initiated, and this at the earliest possible stage of system planning. The thermal design of a modern electronic system is based on a rational selection of a cooling option followed by a thoughtful design consideration. A design should not only be practicable, but also economical, serviceable, reliable, and compatible with other system components.