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70 DESIGN007 MAGAZINE I JUNE 2020 being brought to light early on and help to pre- vent a costly system-level teardown. The crite- ria for evaluating the success of your thermal management process is actually fairly simple and involves three factors to consider. If you can say "check, check, and check" to the following, then you can reassuringly consider your thermal management process as a success: 1. Improved efficiency of heat transfer. 2. Reduced thermal resistance. 3. Observe a lower temperature around the heat-generating component/device. 2. What is the worst that can happen if a device overheats? Increasing miniaturization in electronics means that heat dissipation problems are be- coming increasingly important. More effective thermal management will often lead to en- hanced reliability and life expectancy of de- vices. Insufficient thermal management will quite simply lead to overheating, which may be caused by different factors at play as to why an electronic component becomes subjected to excessive levels of heat. For instance, consum- er electronic devices, such as portable laptops and smartphones, are becoming more prone to overheating. This is because the physical di- mensions of these devices are becoming small- er and more compact. To be specific, as the demand for smaller devices increases and be- comes even more challenging, manufactur- ers of electronic components need to pack far more into even smaller areas. With overheating, failure of the component is typical. If we consider a heat-producing elec- tronic component in isolation, then during op- eration, its temperature will rise until the heat produced within the device becomes equal to the heat lost to the surroundings, and the de- vice has reached equilibrium. The rate of loss of heat from a hot object is governed approx- imately by Newton's law of cooling, which states that the rate of loss of heat is propor- tional to the temperature difference between the body and the surroundings. As the temperature of the component ris- es, the heat loss increases. When the heat loss per second equates to the heat produced per second within the component, the device will have achieved its equilibrium temperature. This temperature may be high enough to sig- nificantly shorten the life of the component or even cause the device to fail. Here, the worst outcome is if an entire de- vice overheats. This will consequently affect neighboring materials, and it must be con- sidered how these materials will react if the temperatures reach the maximum possible level. Thermal management products are the ideal solution for this scenario. A similar ap- proach can be applied to a complete circuit or device which incorporates heat producing in- dividual components. 3. What exactly is a gap filler? A gap filler is a material that is designed to be used at higher thicknesses than a standard thermal interface material. It could be used on a gap of 300 µm up to a few mm. A gap filler will provide a good thermal conductivity but also maintain its stability at these higher thicknesses, ensuring good heat transfer throughout the life of the product. Thermal gap fillers are widely used for mo- bile and touch screen applications; however, some products are extremely adaptable and can be used in a multitude of applications from PCB assembly and housing electronic compo- nents discretely to automotive electronics, in- cluding HEV and NEV batteries, power elec- tronics, LEDs, and fiberoptic telecoms equip- ment. Gap fillers are typically soft and compli- ant for low-stress applications and are easy to dispense due to their low viscosity. They also offer high thermal conductivity, and their low modulus elastomer prevents pump-out, which conveniently leads to my next point. 4. How do I avoid pump-out, and what are the potential consequences of this phenomenon? In general, most devices will go through some form of thermal cycle, even if it's as sim- ple as switching the device on and off. When changes in temperature occur, all materials in the unit will expand or contract to a certain