Thermal simulation as an aid in design work

Thermal simulation is often used for optimization of the design in an early stage and helps identify cooling problems in mobile designs. A modern mobile phone feature a 3.2 mega pixel camera, video recording, mp3 player and web browser. All functions generate heat, while the demand for ever smaller size has to be met. In addition, design engineers find it difficult to measure how well their product dissipates heat. Thermocouple may, for example, act as heat sinks and affect the measurement of small heat sources. Thermal simulation can here be a useful tool and provide more accurate prediction of external case temperature. Since mobile devices rarely have cooling fans and limited number of case openings, careful estimations of materials properties has to be considered to predict what the temperature will be during use. Traditional calculations of thermal resistance, followed by physical test match will often give a misleading result compared with the way the product behave when used by the consumer. Other heat sources in the user’s environment will often affect the product and it is also crucial how the product is stored and assembled. Applications for thermal simulation help to analyze heating, convection and heat radiation. These characteristics are different in mobile applications compared with stationary applications. Appearance, orientation and design of printed circuit board and its components, shape, enclosure, materials, thermal quality and radiation are all included in the calculation. Heat emitting semiconductors are also often a big but fluctuating contributor of heat. However, it is important to keep in mind that the simulation has limitations, not the least in the input data used. Data on characteristics for less common materials can be difficult to find and often has to be replaced by qualified guesses. Anyway this method save time and help to optimize the design before the prototype stage.