Thermal stress and warpage of Chiplet 2.5D/3D Stack – Samsung Austin Semiconductor Fellowship Project, Spring 2024 – Spring 2025.
Chiplet technology utilizing heterogeneous integration allows for high computational power within a small package. One roadblock for chiplet adoption is the thermal warpage produced in chiplets. Thermal stress and warpage are caused by differing coefficients of thermal expansion (CTE) and mechanical properties for materials used in chiplets. Additionally, the variabilities in size and shape of components (i.e., solder balls, TSVs, dies, etc.) of chiplet make it challenging to predict thermal stress and warpage, which can have negative impacts on the performance of electronic components such as transistors or interconnects and can lead to packaging failure.
The goal of this project is to conduct a multi-scale study to understand the formation of thermal stress and warpage and provide guidance for reducing them. The project involves undergraduate students of diverse backgrounds in chemical, electrical, and mechanical engineering.
Chakri Chireddy (Mechanical Engineering)
Cole Garrison (Mechanical Engineering)
Adam Garsha (Mechanical Engineering)
Aaron Lee (Electrical Engineering)
Gisela Mlodzianoswki (Chemical Engineering)
Jacinto Rodriguez Shahin (Electrical Engineering)
Examples below show thermal stress at the microscale components during the solder reflow process, highlighting stress concentrations at the edge of cupper pillars and macroscale warpage due to temperature changes. We are currently investigating the use of an organic interposer to minimize thermal stress and warpage.
MEEN 401-402 UG Capstone Design on High Performance 3D Printed Freeform Composite Structures Fall 2024-Spring 2025, Sponsored by Office of Naval Research
Composites with carbon fiber reinforced polymers (CFRPs) are known for their high strength-to-weight ratio and are increasingly used in various industries from aerospace, automotive, and naval structures. Many of these structures are in the form of complex geometries (freeform structures) and are often exposed to varying mechanical loading in harsh environments. Advances in additive manufacturing techniques have enabled the production of composite structures of complex geometries with tailored mechanical properties. Printing factors (i.e., nozzle speed, temperature, and raster angles) significantly influence the mechanical properties of printed objects. Printed composites present voids between layer depositions, which cannot be eliminated during the printing process. Large void contents can entrap moisture and other corrosive agents, which are detrimental to the performance of composites. Complex geometries introduce prestress (residual stresses), which can affect the load bearing of the freeform structures.
The primary objective of this project is to develop a systematic fabrication and evaluation process for generating 3D Printed Freeform Composite Structures with excellent load-bearing performance. Students are currently designing a composite submarine prototype out of 3D-printed carbon fiber composites. The load-bearing ability of the printed submarine will be evaluated against implosion.
Students: Joshua Serrano, Michael Withey, and Mark Nishikubo
Sound of Kerfing: A New Approach to Integrating Geometry, Materials, & Acoustics to Build Invisibles
Alireza Borhani, Negar Kalantar, Erfan Rezaei, Anastasia Muliana, Zaryab Shahid, Ed Green
Kerf structures are ubiquitous in indoor and outdoor architecture due to their pleasing aesthetics. In this project, we explored their potential applications for tuning indoor acoustics by varying their geometrical parameters (kerf pattern, cut density, cut thickness, etc.) and locally deforming the kerf cells. We presented an integrated design, simulation, and fabrication pipeline to determine the geometrical and material parameters of a kerf panel (Kerfonic Wall) that meets sonic and spatial performance criteria. The acoustic panel is displayed in the Autodesk Gallery in San Francisco. The paper was presented in ACADIA 2022 and was a runner-up for the best paper award.
A kerf panel resembles a porous surface that induces perforations and the coiling kerf cells can act as multiple local resonators. When the kerf piece is deformed to a specific shape, its gap undergoes opening/closing changes and rotations that alter the airflow, influencing sound wave propagation and absorption capacity. Kerfing helps to generate 3D patterns to guide sound diffusion. The slight unevenness of the kerf panels contributes to a better spreading of sounds across the lounge area, while also providing fewer opportunities for focusing acoustic energy. To determine the acoustic performance of kerf structures in space, Reverberation Time tests were performed following ISO 3382-2. The deployment of the Kerfonic Wall resulted in a significant reduction in the Reverberation Time, increased the effective absorption of the space, and thus decreased the echo of the sound in the lounge.
This is a collaborative work between California College of the Arts, Texas A&M University, Parametric House, and Hottinger Bruel & Kjaer Inc. Part of this study is financially supported by the US National Science Foundation. The Autodesk Technology Center in San Francisco supported the fabrication processes.
Shell We Dance?
https://www.biodesignchallenge.org/cca-ucsf-2024
Food waste has negatively impacted our living spaces from the increase in landfills to greenhouse gas emissions. Recycling food waste through composting or bioenergy can lower emissions, improve soil health, and support a circular economy. Researchers from the California College of the Arts and UC San Francisco have been exploring the use of natural shell waste, e.g., eggshells and crustacean shells, as sustainable alternatives for construction applications such as pavers, urban furniture, wall panels, and modular systems for larger-scale architectural applications. Our group has been collaborating with CCA and UCSF on investigating the influence of material compositions and interlocking microstructures on the overall mechanical performance of egg-shell biobased composites. The results show that biobased composites with infused bacteria and interlocking microstructures have better load-bearing ability under compression.
Summer camp: Virtual Acoustic
Our group has actively participated in summer camps to introduce research activities and outcomes to high school campers. For the Youth Adventure Program at TAMU in July 2021, together with faculty and a graduate student from Construction Science (Dr. Youngjib Ham and Ms. Di Liu) we organized a “Virtual Acoustics” camp. The campers determined the resonant frequencies of various materials triggered by sound waves and used a virtual acoustic environment to explore the influence of different wall materials in a virtual room on speech intelligibility. The exit questionnaire indicated that many students were enthusiastic to learn about the projects and seriously considered science and engineering majors.
Summer camp: Plant Mechanical and Electrical Responses
In collaboration with Dr. Matt Pharr at TAMU, we participated in a TAMU-organized summer camp on Plant Mechanical and Electrical Responses that targeted middle and high school students. We introduced the campers to plant morpho-anatomical features and their effects on plant biomechanical properties. We also discussed the ability to harness electrical energy from plants. The campers experimented with measuring current and voltage from multiple crops (potato, lemon, etc.) and exploring strategies to increase electric power. The campers also designed lightweight and stiff composites, mimicking plant stems, to bear bending loads.