Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.799645
Title: Eddy current pulsed thermography for non-destructive testing and evaluation of IGBT power semiconductors
Author: Li, Kongjing
ISNI:       0000 0004 8505 893X
Awarding Body: Newcastle University
Current Institution: University of Newcastle upon Tyne
Date of Award: 2019
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Abstract:
Power semiconductors such as Insulated-gate Bipolar Transistors (IGBT) ranked as the most unreliable components in power conversion systems. The hidden nature of defects in IGBT chips or packaging materials may result in them not being noticed, which may ultimately lead to failures. Traditional inspection methods for the detection of defects in IGBT suffer from serious limitations. The electrical testing techniques such as electrical probing testers provide accurate measurement outcomes but are generally very expensive. Other inspection methods such as X-ray or Acoustic microscopy may be capable of detecting defects in a non-destructive way but suffer from low inspection efficiency. In an attempt to contribute an innovative testing approach, this research provides a study of how an eddy current pulsed thermography (ECPT) non-destructive testing (NDT) system can be applied for the inspection of IGBT power semiconductors on both the wafer level and packaging level. The research work offers a number of key contributions. In brief, the research: (1) developed the ECPT system with newly designed induction coils for IGBT inspection; (2) investigated the newly discovered heating mechanism of the defect in ECPT inspections, which is the heat accumulation at the defect; (3) detected bond wire defects using the developed ECPT system; a Helmholtz coil was designed to overcome the challenge of heating the bond wires uniformly in the IGBT modules. The principle of defect detection in bond wires is based on the newly discovered heating mechanism; (4) inspected the IGBT wafer provided by the industrial partner using the developed ECPT with the newly designed induction coil. Thermal features of the wafer surface were investigated with the developed image processing technique that can minimise the emissivity issue in the thermography. Subsurface thermal features of the IGBT wafer were investigated with the help of the image processing technique of independent component analysis. In conclusion, although the application is at a nascent stage, this research successfully demonstrated initial attempts to apply ECPT to the inspection of IGBT power semiconductors. The developed NDT system shows good potential and has important merits such as being contactless, efficient and non-destructive. With future optimisations in induction coil designing, thermal image resolution and feature extraction techniques, ECPT may bring significant financial benefits as the technique can likely be implemented at a much lower cost than the current electrical testing methods.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.799645  DOI: Not available
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