This thesis explores the use of Fibre Bragg Grating (FBG) sensors for direct on-chip thermal sensing of Insulated Gate Bipolar Transistors (IGBTs). The research focuses on three main aspects: (1) investigating FBG sensor bonding technologies on IGBT chip surfaces and the impact of various interface materials on thermal measurement performance, (2) analyzing the influence of FBG head length on IGBT thermal sensing accuracy, and (3) evaluating FBG sensor performance for in-situ IGBT junction temperature sensing compared to voltage-based methods. A Finite Element Analysis (FEA) model of the IGBT power module was developed to understand thermal distribution on the chip and assess FBG sensor performance. Various FBG sensor bonding techniques were explored, with the FEA model used to study thermal conductivity of interface materials. Performance of glue-bonded FBG sensors during thermal expansion and contraction was examined, revealing potential strain due to coefficient of thermal expansion (CTE) mismatches and adhesive forces. Effective sensing performance was achieved by operating FBG sensors within the glue's linear working range. Additionally, the impact of FBG head length on direct on-chip thermal sensing of IGBTs was investigated through thermal simulations and experimental characterizations. Challenges arising from significant thermal gradients in IGBT applications with longer head lengths were identified. Analysis of reflected spectrum distortion of FBG sensors provided insights into the limitation of accurately measuring IGBT junction temperature. Comparisons were made between FBG-based contact temperature measurement and voltage-based approaches, assessing strengths, limitations, and potential errors associated with each method. Overall, this research provides valuable insights into the application of FBG sensors for direct thermal sensing of IGBTs. The findings contribute to the understanding of the thermal behaviour of IGBT power modules and offer guidance on optimizing FBG sensor performance in terms of bonding techniques, head length selection, and accurate junction temperature measurement. The study confirms the suitability of FBG sensors for in-situ sensing of IGBT junction temperature, enabling reliable and effective thermal monitoring in various operational conditions.
|Date of Award
|31 Dec 2023
- The University of Manchester
|Mike Barnes (Supervisor) & Sinisa Durovic (Supervisor)