【Introduction】NTC, as a thermistor element with negative temperature coefficient, is widely used in temperature sensing and circuit protection. In the actual use case design, the application scenarios of NTC are different, and some work scenarios are very complicated, which requires in-depth exploration of the application details of NTC. With rich product and application experience, Vishay’s engineers can help you answer all kinds of problems encountered in NTC application development, such as the following thermodynamic analysis problem in NTC applications.
Q: At what temperature can the NTCS detect extreme ambient temperature differences between the top and bottom? (as the picture shows)
The conditions shown in the picture are complex temperature or heat flow patterns depending on the heat transfer on both sides (top and bottom) of the SMD NTC.
To make predictions, we need to quantify the entire thermodynamic environment including the PCB, pads and traces, solder paste, top air conditions, etc.
In the simple picture shown above (no PCB mounted), the condition can be simplified to: the component will be at an average temperature or
In practice, the component (NTCS, NTCAFLEX or NTCALUG) will be fixed to a surface and the average temperature that the NTC thermistor die will reach will depend on the heat flow into and out of the component.
In the NTCAFLEX example in the figure below, the given temperature class is only a reference example.In practice, everything depends on the different thermal resistances between different layers and materials: hot plate (object under test) → flexible PCB → NTC chip → dome package → air
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