Infrared Lock-in Thermography Research Articles

Output Power and Gain Monitoring in RF CMOS Class A Power Amplifiers by Thermal Imaging

The viability of using off-chip single-shot imaging techniques for local thermal testing in integrated radio frequency (RF) power amplifiers (PAs) is analyzed. With this approach, the frequency response of the output power and power gain of a Class A RF PA is measured, also deriving information about the intrinsic operation of its transistors. To carry out this paper, the PA is heterodynally driven, and its electrical behavior is down converted into a lower frequency thermal field acquirable with an InfraRed lock-in thermography (IR-LIT) system. After discussing the theory, the feasibility of the proposed approach is demonstrated and assessed with thermal sensors monolithically integrated in the PA. As crucial advantages to RF-testing, this local approach is noninvasive and demands less complex instrumentation than the mainstream commercially available solutions.

Functional and Consumption Analysis of Integrated Circuits Supplied by Inductive Power Transfer by Powering Modulation and Lock-In Infrared Imaging

The functionality and consumption of a Radio Frequency IDentification Integrated Circuit (RFID IC) supplied by inductive power transfer has been noninvasively analyzed. This has been done by means of an InfraRed Lock-In Thermography (IR-LIT) system and frequency modulating the RFID IC powering scheme by biasing the external powering coil considering several amplitude modulation waveforms. This generates thermal harmonics at the beating frequency in all IC blocks, enabling their detection as heat sources by IR-LIT. The main aspects addressed in this investigation have been the following: the suitability study of the proposed modulation strategies, the characterization of the coupling between coils and its effects on the RFID blocks, the RFID IC functional analysis, and the dependence of the local energy consumption on the total power delivered to the die. In addition, it has been determined that the RFID IC presents a dysfunction due to the deactivation of some blocks during operation. Results suggest that this unexpected behavior is due to a desynchronization between some of the RFID blocks. Consequently, this stops the internal control signal, deactivates some specific RFID blocks, and ceases the back-telemetry block operation.

Investigation of factors affecting backside hotspot localization in infrared lock-in thermography

Infrared lock-in thermography (IR-LIT) is a fault localization technique that serves the purpose of detecting a local heat source or hotspot emitted by the faulty area. Performing backside hotspot localization overcomes the limitation during frontside hotspot localization, especially for shorted areas that emit a low heat source. In order to produce better hotspot localization from the package backside, it is important to study more of the factors affecting backside hotspot localization, including the power settings of the device, the lock-in frequency, and the die thickness of the packages. Power packages are inspected using a tool with varying power and frequency settings. The results are collected by observing the size of the hotspot and by recording the time taken for the hotspot to appear. To investigate the die thickness, the die surface is grinded from the backside of the die and the thickness of the die was measured using x-rays. The relationship between the power settings, the frequency settings, and the die thickness does show significant changes to the hotspot size and the time taken to generate a hotspot.

Local non invasive study of SiC diodes with abnormal electrical behavior

In this work, Silicon Carbide Schottky Barrier Diodes (SBDs) were inspected by Infrared Lock-In Thermography to study and determine the origin of structural weak spots resulting from their manufacturing and electro-thermal stressing tests. These spots are frequency modulated following three different approaches representative of the SBDs operating regimes and detected by their infrared emission, as they behave as hot spots. According to thermal results, such weak spots have originated from barrier modification due to the wire-bonding process, non-uniform active area resistance due to bad metallization electrical contact, deep level traps creation due to high energy implantation in the edge termination, and internal propagation of lattice defects during thermal cycling.

Non-destructive Measurement of Total Carotenoid Content in Processed Tomato Products: Infrared Lock-In Thermography, Near-Infrared Spectroscopy/Chemometrics, and Condensed Phase Laser-Based Photoacoustics—Pilot Study

Carotenes found in a diversity of fruits and vegetables are among important natural antioxidants. In a study described in this paper, the total carotenoid content (TCC) in seven different products derived from thermally processed tomatoes was determined using laser photoacoustic spectroscopy (LPAS), infrared lock-in thermography (IRLIT), and near-infrared spectroscopy (NIRS) combined with chemometrics. Results were verified versus data obtained by traditional VIS spectrophotometry (SP) that served as a reference technique. Unlike SP, the IRLIT, NIRS, and LPAS require a minimum of sample preparation which enables practically direct quantification of the TCC.

Spatially and frequency-resolved monitoring of intradie capacitive coupling by heterodyne excitation infrared lock-in thermography

This paper combines the infrared lock-in thermography (IR-LIT) and heterodyne excitation techniques to detect high-frequency capacitive currents due to intradie electrical coupling between microelectronic devices or more complex systems. Modulating the excitation with the heterodyne approach, we drive devices or complex systems with high frequency electrical signals in such a way that they behave as low frequency heat sources, modulating their temperature field at a frequency detectable by an IR-LIT system. This approach is analytically studied and extended to a bi-dimensional scenario, showing that the thermal information at low frequency depends on the electrical characteristics of the sample at high frequency.

Effect of Modulation Frequency on Detecting Metal Materials with Microcracks Based on Ultrasound Infrared Lock-in Thermography

The non-destructive ultrasound infrared lock-in thermography (ULT) testing method was used to detect metal specimens with defects of micro cracks. An experimental platform was built based on the analysis of the ULT principle. Experiments had been carried out to Q235 plates with different testing parameters. The testing effect of thermography, amplitude and phase images was analyzed, and the relations between amplitude difference, phase difference, signal-to-noise ratio and modulation frequency were discussed.

Advanced thermal failure analysis and reliability investigations – Industrial demands and related limitations

The thermal interaction between actively operated integrated circuits and applied characterization tools is one of the most important ones within failure analysis (FA) and reliability/methodology (RM) investigations. Hereby different kind of thermal interaction mechanisms can be utilized, whereas these mechanisms have to be separated for instance into classes with respect to thermal excitation and/or detection, spatial limitations, and underlying physical principle. Although they all have in common the capability to link the thermo-electric device characteristic to a representing output signal, they have to be interpreted in completely different ways. Therefore, within this paper we discuss from a practical engineering point of view established FA/RM characterization techniques by means of infrared-lock in thermography (IR-LIT) and thermal induced voltage alteration (TIVA) case studies as well as the capability of non established ones like scanning thermal microscopy (SThM), thermal reflectance microscopy (TRM), and time domain thermal reflectance (TDTR). Hereby we focus on the complementarities of the methods for localization and characterization as well as on the according industrial demands and related limitations.

Analysis of stainless steel welded joints: a comparison between destructive and non-destructive techniques

Welding is a joining procedure that offers some benefits over mechanical fasteners such as weight reduction and absence of notches induced by machining operations. Adversely, welding generally involves heating the two parts to be joined, but heating can entail local modifications with loss of material characteristics. The welded zone may also include defects such as gas bubbles, or spurious materials with deleterious effects on the material strength and durability. Thus, each welded joint should be non-destructively tested for quality assurance. In the present work two kinds of joints, lap and butt, are analysed. The joints are obtained from both similar and dissimilar materials, which are plates of AISI304 and AISI430. Two different autogenous (i.e. without filler material) fusion–welding processes are employed, which are the conventional tungsten inert gas (TIG) and the CO2 laser beam. Joints are investigated with destructive and non-destructive techniques to evaluate the presence and the extension of the so-called heat-affected zone and/or the occurrence of defects. Non-destructive evaluation is performed with infrared lockin thermography and results are compared to macrographs and micro-hardness destructive measurements.

Localization of gate oxide integrity defects in silicon metal-oxide-semiconductor structures with lock-in IR thermography

A technique to image gate oxide integrity (GOI) defects across large gate areas has been developed. First, a low-ohmic bias pulse is used in order to break down nearly all GOI defects in a large area metal-oxide-semiconductor (MOS) structure. Then a periodic bias of typically 2 V is applied and the local heating caused by the leakage current through the broken GOI defects is imaged by infrared (IR) lock-in thermography. This method allows us to detect very small temperature variations down to 10 μK at a lateral resolution down to 10 μm. The determined defect densities in Czochralski silicon materials with various densities of crystal originated particles are in good agreement with charge-to-breakdown measurements of small area MOS capacitors. In conclusion, IR lock-in thermography provides a fast and reliable imaging technique of the lateral GOI defect distribution across the entire wafer area.