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Michaela Brade
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Temperature-dependent Resistance

The temperature on a circuit board may affect the function of the individual components in several ways. Both refrigeration as well as heat exerts have an influence on the components. The temperature is influenced by the installed components as well as the outside temperature. Temperature thresholds between colder and warmer areas could affect for example the resistance which could lead to malfunction or faster wear.


In this application, we have investigated the influence of temperature on the resistance of a circuit board. In the case of high or low temperatures on the circuit board the resistance can change and thereby influencing the functionality. The aim of this project was to define the critical point of temperature.


To solve this question two analysis are needed. Firstly, the temperature-dependent change in resistance must be defined and secondly the temperature distribution has to be simulated. Using this method it is possible to estimate the temperature influence on the functionality of the component.


In Figure 1 you can see how the voltage gradient of the circuit board increases with rising temperature. The progression of the curve results from the dependence of the resistance on temperature. The current flow is kept constant. At the graph you can see that it is important not to pass a certain level or temperature to guarantee the operation of all components without malfunction. The exact resistance of each circuit path can only be measured as a function of temperature. The temperature profile in Figure 2 provides information on the direct heat distribution and its influence on the circuit board. As expected the regions of high thermal conductivity show a significantly higher temperature than the substrate of the circuit board. By using this method we can identify the areas reaching a critical temperature value.  Using this analysis, more efficient and application oriented circuits can be realized. With intelligent design certain areas can for example do without to direct cooling.

Advantages of FEM Simulation

  • investigation and representation of temperature-critical sites
  • Simulation at different outdoor temperatures
  • Presentation of experimentally inaccessible conditions

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