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Experimental and numerical study of capillary underfill process for advanced CMOS packaging technologies
Leuven | More than two weeks ago
Gain new insights into semiconductor packaging via improved understanding in complex fluids
Capillary underfill is a widely used process in the microelectronics industry to mitigate thermomechanical stresses when bonding a semiconductor die (e.g., a flip-chip) to a printed circuit board (PCB). The underfill material (typically an epoxy-based resin) is drawn by capillary forces through gaps between the die, PCB and solder interconnects to relieve stress in the interconnect joints once the underfill material has cured. However, the complex rheological and wetting behavior of the underfill material presents challenges to accurately model and predict the underfill process. Defects such as voids (entrapped air pockets within the underfill material) can have an adverse impact on reliability. The challenges are exacerbated in advanced packaging technologies under development, including co-packaged optics (involves interfacing semiconductor and optical components into a single package), where reduced interconnect pitch and/or bond gap heights are required.
The scope of this PhD topic is develop improved techniques for modeling and characterizing both the capillary underfill materials and capillary-driven underfill process. Of particular interest is developing a better understanding of how the underfill materials behave in small gaps. Furthermore, experimental techniques to characterize die planarity and gap height after bonding are to be explored. The PhD candidate will be responsible for developing models, utilizing existing experimental methods in fluid mechanics (including optical-based characterization methods), and developing data analysis techniques to assess the capillary behavior of complex, non-Newtonian fluids in small gaps.
Prospective candidates should have strong analytical skills, ambitions to learn experimental characterization techniques in fluid mechanics and preferably, prior knowledge in computational fluid dynamics. At imec, the selected candidate will work in a diverse, dynamic, multi-disciplinary team and gain expertise in the challenges of semiconductor manufacturing, setting the stage for a fruitful career in R&D supporting a high tech industry.
Required background: Engineering, Science, Physics
Type of work: 45% modeling, 45% experimental, 10% literature
Supervisor: Stefan De Gendt
Co-supervisor: Ben Jones
Daily advisor: Ben Jones, Koen Kennes
The reference code for this position is 2025-010. Mention this reference code on your application form.