Thermoelectric cooling your chip designs

A new approach is needed for electronic thermal management that focuses on providing appropriate cooling when and where it is needed within the electronics system. Using thin-film thermoelectric coolers (TF-TECs) is the answer.

Integrating a TF-TEC material into flip chip solder bumps for electronic packaging enables active thermal management at the surface of the chip. This is a fundamentally new methodology for achieving temperature uniformity at the chip level. Unlike conventional solder bumps, which provide an electrical path and a mechanical structure, each thin-film thermoelectric thermal bump acts as a solid-state heat pump on a micro-scale.

TF-TECs have demonstrated a heat pumping capacity that far exceeds that provided by traditional bulk TEC products. This makes TF-TECs ideally suited for high heat density applications. In addition to the increased heat pumping capability, the use of thin films allows for truly novel implementation of TE devices.

Micro-scale thermal bumps can be integrated into the standard flip-chip process, bringing new functionality to electronic product design. In the future, it will be possible to design thermal management into a circuit in the same manner that transistors, resistors and capacitors are integrated today in conventional circuit design.

Along with the addition of this new design capability also comes the need to quickly and accurately model the behavior of this new circuit element. The reduced-order model algorithm is used for rapid simulation of the performance characteristics of the thermal bumps during the circuit design process. The nature of thermoelectric device operation is such that iterative solutions are required. The reduced-order algorithm minimizes the computational complexity by making an initial estimate of the device's endpoint temperatures based on system boundary conditions, and then employing the method of iterations.

The use of thin-film thermoelectric devices in electronics cooling brings with it significant challenges in the area of mathematical modeling and simulation of devices. The fundamental nature of thermoelectric cooling is such that thermal and electrical degrees of freedom are present in all models describing the system.

Additionally, the amount of heat flowing through a thermoelectric device is a function of the temperature at the boundaries of the active thermoelectric material contained within this device. Likewise, the temperatures at these boundary surfaces are dependent on the amount of heat flowing through the boundaries. This counter-dependence necessitates the usage of iterative methods for determining an accurate solution for the temperature field in the device and in the surrounding system.

It is usual for one of two approaches to be used. The most common approach is the reduction of the system into a one-dimensional thermal resistance model. In this case, familiar equations developed by Goldsmid are used to calculate the basic performance of the TF-TEC in the system. This first-order approach becomes less accurate, however, as the thermal resistance of the system increases.

The second less common approach is to use a numerical simulation using finite element analysis or some other numerical analysis method to solve the field equations for thermal and electrical degrees of freedom simultaneously; usually with some sort of iterative solver.