Thermographic Fault Isolation on Chips and Power Modules

The E-LIT solution employs Lock-in Thermography as its method. This involves selectively applying electrical excitation to electronic components or assemblies in order to detect and analyze local faults based on thermal anomalies. During electrical activation of components under investigation, changes in surface temperature are measured using a high-end infrared camera from the ImageIR® series to identify so-called "hot spots”. This allows even the smallest defects, such as point and line short circuits, oxidation, and faults in transistors and diodes within circuits, which cause only minimal temperature deviations in the millikelvin (mK) or microkelvin (μK) range, to be detected.

At STMicroelectronics, the test system – comprising an excitation source, an infrared camera with adjustable Z-axis positioning and additional accessories – was integrated into the failure analysis laboratory. For the analysis of large components, the E-LIT system is equipped with 25 mm lenses that provide a wide field of view, along with several microscope lenses capable of resolving fine details up to 1.3 µm. Hot spots can be detected with high sensitivity at chip level using as little as 2 μA. To excite power modules, high voltages up to 3 kV are applied.

The analysis is performed using InfraTec’s IRBIS® 3 active online operating software, which offers a wide range of comprehensive analysis functions. The use of various color palettes, including inverted and weighted modes, has proven particularly effective for fault detection.

Lock-in Thermography is a key method at STMicroelectronics for identifying faults in electrical components. The user-friendly method is especially effective in exactly locating short circuits and other anomalies. Users particularly appreciate the simple visual identification of faults and the flexibility of the system for measurements on different components such as ICs, sensors, LEDs or power modules. The E-LIT solution played a crucial role in the approval of a new mass production project in Calamba, where it was used to quickly pinpoint hot spot locations across multiple batches.