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52 DESIGN007 MAGAZINE I JUNE 2018 Last year I introduced the subject of thermal management materials—why they are neces- sary, what materials and methods are available to us, how best to apply them and so on—bas- ing each column on our customers' frequently asked questions. My colleague, Alistair Little, has discussed resins in greater detail in each of his columns; now, I've been invited back to pick up from my last series, this time con- centrating more closely on the practicalities of thermal management with this five-point guide to material choice and application. Understanding the Dimensions: Interface or Gap Filler? Knowledge of the dimensions of your appli- cation is critical to the selection of appropri- ate thermal management materials. A thermal interface is the space between a component and its heat sink, and the thermally conduc- tive media used in this space are referred to as thermal interface materials (TIMs). This space is usually very small (i.e., on the micron scale). A gap filling application, on the other hand, is more to do with the distance between a component and the metal housing that encloses an electronics assem- bly and is typically measured in millimetres. In this case, a ther- mally conductive material is used to help minimise the chances of hot spots within the unit itself while the casing is used as the heat sink. The difference between a few microns and a few millimetres could be critical to the perfor- mance of the thermal medium chosen. For example, if you place a TIM in a gap filling application, it is likely to be unstable in the thicker layer: with vibration, or following a period of tempera- ture cycling, it could easily be dis- placed. Likewise, if a gap filling material is used in a thermal interface application, it will be very difficult to achieve a thin, Thermal Management Materials: Easing the Decision-Making Process Sensible Design by Jade Bridges, ELECTROLUBE