Between reality and false myths, here are some recommendations to take best advantage of the properties of thermally conductive compounds.
Almost ten years after their introduction to the market, the success of thermoplastic compounds with improved thermal conductivity can be considered as established. Despite the inevitable initial mistrust and difficulties connected with the use of such materials, today many manufacturers of technical compounds include in their range at least one series of grades for injection moulding items requiring a better heat removal.
However, the approach to these new proposals is not always correct, especially by users accustomed to historically proven materials, primarily aluminium or copper. So some “myths” have to be dispelled not to incur common design errors.
Main evaluation mistakes
A first mistake is to expect the same thermal performance of metals.
This is a wrong assumption, as many successful applications showed that metals, in terms of heat exchange, are often oversized, and the same results can be reached by thermally conductive compounds with one-tenth thermal conductivity. This is especially true in the natural convection regime, i.e. when heat extraction is not carried out by forced ventilation. The second typical error is to continue to think about “standard” geometries – e.g. for heat sinks – i.e. designed for a good heat transfer, but always using metals.
A new and more flexible mindset is to be entered into, which allows to understand that thermoplastic compounds are completely different materials, in particular with regard to their compositional inhomogeneities resulting in an physical anisotropic behaviour.
Not considering this fact and treating plastics in the assumption that they behave like metals, may lead to significant design errors, sometimes ending in the failure of potentially viable projects.
For this reason, it is extremely important that the most intimate properties of these materials are understood, “tamed” and capitalized on, especially in the design phase.
In addition, requirements are not limited to thermal performance.
There are, in fact, aesthetic constraints imposed by marketing and product designers, as well as electrical and mechanical properties. The development of increasingly efficient compounds even from this aspect, as well as the freedom of design, flexibility and efficiency of operation offered by these materials, are consolidating their increasing success in the most advanced technology sectors…