Measurement Strategies

Abstract

In the following sections some practical aspects of using lock-in thermography in the functional diagnostics of electronic components will be discussed and illustrated by measurement examples of a typical, thermally thin sample (solar cell) and a thermally thick one (integrated circuit). All these discussions are based on the theoretical findings presented in Chap. 4. Section 5.1 discusses the question which of the images available from a lock-in thermography experiment (0° image, −90° image, amplitude image, or phase image) is most appropriate to display certain details of different heat source distributions. In Sect. 5.2, the influence of the lock-in frequency on the obtained signal amplitude and lateral resolution of the thermograms will be discussed and demonstrated for different heat source geometries. In Sect. 5.3, the influence of a spatially varying IR emissivity will be discussed (emissivity contrast), and different ways to overcome this influence will be introduced and demonstrated. Here, a novel way to display lock-in thermography results will be presented, providing a perfect correction of the emissivity contrast and being advantageous particulary for microscopic investigations of ICs. Section 5.4 describes the technique of measuring local I-V characteristics thermally (LIVT). In addition, it will be shown there how a non-destructive mapping of the so-called n-factor of exponential I-V characteristics is possible. Finally, in Sect. 5.5 a simple technique will be introduced to distinguish Joule type heating from Peltier effects in lock-in thermography experiments on resistive samples.