Thermal enhancement of surface mount electronic packages with heat sinks

Surface mount plastic packages are a cost effective way to package integrated circuit chips. However, plastics have poor thermal conductivity and therefore, plastic packages are not suitable for packaging high powered chips. Recently several variations of surface mount plastic packages have been developed for improving the thermal performance. These various techniques for improving the thermal performance can be broadly classified into two categories: internal enhancement of the package and external enhancement. For internal enhancement, high conductivity materials are used to improve heat spreading within the package. Examples of such enhancement include plastic packages with molded and exposed heat spreaders, packages made from metals like aluminium, and ceramic packages. For external enhancement, the thermal performance is improved by attaching a suitable heat sink to the package. This paper discusses the thermal performance of the various surface mount packages with and without heat sinks. It is shown that with a suitable heat sink, the thermal performance of a plastic package is similar to that of a metal or a plastic package with exposed heat spreader. In terms of cost, heat sink attachment offers the most cost effective way of improving the thermal performance of the plastic package, provided there is some space available for the heat sink