The thermal transient testing system consists of the T3Ster hardware and software elements for measurement control, data acquisition, and for the subsequent evaluation and display of data measured.
A semiconductor device is modeled in a thermal transient test as a structure consisting of
Figure 2-1: Heater/sensor structures
In the case of dedicated thermal test chips heaters (dissipators) and sensors are separate structures (Figure 2-1d). The most common semiconductor devices like MOS field effect transistors (MOSFET) and bipolar junction transistors (BJT) (Figure 2-1a,b) have an inherent feature of sensing temperature parameters influenced by the temperature such as UBE or UGS voltages can be measured.
The measurement control software applies programmed power excitations to the dissipator element, and records the complex temperature responses.
The evaluation process includes producing smoothed time functions and calculating the impulse thermal resistance diagram, time-constant spectrum, complex locus of the thermal impedance, differential and integral structure or profile function.
In case the sensor and the dissipator is the same element or the sensor is close to the dissipator the thermal impedance can be calculated for this so called driving point. In case the sensor is in a farther position the transfer impedance can be calculated. This way we distinguish between driving point thermal impedances and thermal transfer impedances.
