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The IEEC values research as a means to create connections and to open future possibilities in the area of electronics packaging.

  

Pooled Research Projects

Every year, we provide what we call "seed-funding," to propel research opportunities in the direction of capacity building and problem-solving for faculty members in academia.

Skilled researchers partner with industry members to meet real-time project needs of companies. That is, whether you are a chemist, physicist, or mechanical engineer, to name a few, members of all fields carry expertise that is integral in catapulting the metrics of success for projects to reach new heights.

Below are the abstracts of the selected 2021-2022 Pooled Research Projects-a partnership between faculty and mentor companies.

2021-2022 Pooled Research Projects

• Femtosecond Laser Micromachining Toward Photonic Packaging - Bonggu Shim

  In this proposed research, we will investigate femtosecond laser micromachining (FLM) of single-mode and multi-mode waveguides in various flexible glass substrates with different thermal properties.

  Second, we will fabricate curved waveguides via FLM and investigate light coupling and guiding in preparation for photonic packaging.

  Third, we will fabricate and test photonic lanterns which are spatial light multiplexers connecting multi-mode waveguides and single-mode waveguides.

• SnBi-based Solder Joints During Current Stressing - Characterizating Failure Mechanisms and Times - Eric Cotts

  The increasing use of eutectic SnBi based, low temperature solders has created a demand for a better understanding of the response of these materials to current stress (1,2).

  Segregation of Bi to the anode, into a fairly uniform layer, occurs at relatively low temperatures, current densities, and times (3-11). At longer times, higher temperatures or larger current densities, catastrophic failure of the solder joint occurs, with significant cracking of the solder joint and very large increases in electrical resistance (Fig. 1).

  We seek to characterize and quantify this more extreme behavior, with new models that succinctly predict failure times. We also seek to explain and quantify the long term motion of Bi in these low temperature solder (LTS) joints during current stressing.

• AC Fast Charger for eVTOL Aircraft - Pritam Das

  Electrified Vertical Take-Off and Landing (eVTOL) is a revolutionary concept in environment friendly flight technology enabled by modern batteries, lightweight electrical actuators and motors. This proposal will explore feasibility of high power density lightweight (>500 kW) fast chargers powered by medium voltage (13.8 kV Three phase AC). Given the large amount of energy required by eVTOLs and the quick turn-around extra fast charging allowing charging rates of 2C or higher is a key requirement in enabling mass scale use of EVTOLs.

  Typically this will require chargers of the range of 0.5 MWatts or higher. Initial studies done by the PI and a member company shows that no such high power fast chargers exist. The proposed one year study for an IEEC TAB project will explore charger realization using state of art power electronic converter based on wide band gap devices patented by ºÚÁÏÊÓƵ, exploration of applicable standards for such chargers, reliability assessment etc. Eventually the outcomes of this study will lead to realization of such chargers by member companies in assistance with federal and other sources.

• Fabrication of Liquid Metal Fiber Composites for High Performance and Compliant Thermal Interface Material - Pu Zhang, Scott Schiffres

  This project aims to develop a new thermal interface material (TIM) with high thermal conductivity and low stiffness based on liquid metal (LM) polymer composites.

  We propose to fabricate LM composites with well-aligned and interconnected fiber networks that will have thermal conductivities approaching theoretical limits. Being compliant and resilient, this new TIM will not only provide conformal interfacial contact but also mitigate thermal stress-induced pump out and voiding failure modes.

  We propose to fabricate this material through a novel approach that will enable efficient and mass production of this new TIM. The microstructure, mechanical properties, and thermal properties of the new TIM will be characterized to assess its performance.

  By tailoring composition and microstructure, we expect to develop thin TIMs with thermal conductivity of 10-20 W/m-K, modulus below 1 MPa (1/10000 of indium), and thickness of 100 μm. The new TIM can be used as TIM thermal pads in electronic packaging or soft conductive materials in flexible electronics.

• Fabrication of Ceramic/Metal Bi-material for Hybrid Integrated Circuits and Electronics using a Novel Additive and Substractive Manufacturing Process - Fuda Ning, Mark Poliks

  The conventional manufacturing technologies for the hybrid integrated circuits (HICs) lack design flexibility due to the 2D pattern of the film/tape. In this proposed research, we present an innovative hybrid manufacturing approach to fabricate HICs completed in one manufacturing system. The freedom of geometrical design of the circuits is achieved by the additive manufacturing approaches (including ceramic slurry extrusion and direct silver ink writing) as well as a subtractive milling process.

  This proposal aims to innovate the functional hybrid electronics using a cost-effective and time-saving manufacturing process. In addition, the fundamental understanding of the bi-material co-sintering process will be advanced. Alumina/glass multi-phase slurry will be prepared as the low temperature co-fired ceramic (LTCC) and printed by a dispenser. Surface milling will be used to create internal channels, which are then filled with the silver ink inside the ceramic encapsulation. Such an integrated component will be sintered at a temperature of less than 900°C. The performance of the manufactured device will be comprehensively tested through a variety of mechanical, thermal, and electrical experiments.

• A Low Cost Approach to Filling of Through Holes in Glass or Ceramic Substrates - Peter Borgesen

  Vias through silicon interposers or chips (TSVs) are usually filled by electroplating of Cu. This requires careful optimization of the electroplating processes for the specific design, and the actual time to fill high aspect ratio vias may be extensive. It has been suggested that filling the vias with nano-particles and sintering these may offer a low cost, easier to control alternative. For a number of reasons that should be easier to do for vias through ceramic or glass interposers (TGVs).

  We expect that TGVs with very high aspect ratios can be filled with an appropriate nano-particle paste in a very cost effective manner. Determining the feasibility of this approach will however require a systematic study to optimize the filling and sintering processes, and to assess the resulting reliability under realistic use conditions.

  Process optimization will not only need to maximize filling of the vias with the nano-particle paste, and minimize the final porosity of the sintered structure, but also to ensure adequate adhesion to the side walls. Sintered nano-particle structures tend to be macroscopically brittle unless adhesion to a more rigid substrate or carrier can suppress strain localization. Importantly, interpretation of accelerated test results will require a mechanistic understanding of deformation properties and damage evolution. Previous research has shown both to be very different than for bulk structures. There is little doubt that acceleration factors will be different than for electroplated Cu in the same configurations, so general comparisons cannot simply rely on performance of a specific test vehicle in one or a few conventional accelerated tests.

  Glass offers major potential advantages over silicon, and not only in terms of cost and electrical properties. Ceramic or glass interposers may even allow for filling of the vias with Ag, rather than Cu, which may eliminate the need for an active sintering ambient. A particularly important advantage with the proposed approach is that we do not need to fill blind vias. The interposers will start out with the final thickness and vias through them. Ceramic and glass interposers also allow for high process temperatures if needed.

  It is proposed to conduct a systematic study of the filling of holes through ceramic or glass with nano-Cu and nano-Ag pastes and of the resulting electrical resistance, fatigue resistance and electromigration performance. This will include trying out pastes that provide for adhesion to glass and presumably ceramic without a pre-deposited adhesion layer. Glass wafers with vias will be provided by Corning. Importantly, a mechanistic understanding will be developed, allowing for optimization of the processes, the definition of accelerated test protocols and the proper interpretation of the test results.

• Predictive Modeling for Solder Paste's Physical Properties during Reflow Soldering in the SMT via Physics - Informed Deep Neural Networks - Daehan Won

  With advanced technologies in sensing and data processing, large amounts of data can be collected, and it can be used for intelligent systems as a core of ‘smart’ manufacturing. Surface mount technology (SMT) is the leading technology of core components of modern electronics assembly.

  It has a huge potential to move forward to the next generation of manufacturing and technological advances. One of the critical problems for the advancement of current manufacturing is to predict the physical properties and thermodynamics of solder paste during the electronic assembly process.

  Due to the miniaturization trends in this domain, any subtle environmental changes and variations of the information might affect the physical behavior and consequently lead to critical quality nonconformities. There is a great need for improving the prediction accuracy and efficiency of various physical behaviors, especially during the self-alignment and reflow process.

  Recently, data-driven artificial intelligence (AI) models play an important role in advancing scientific discovery in the engineering context, which is traditionally dominated by physics-based simulation models. However, the application of AI models has often encountered limited successes due to insufficient data, inability to produce physically consistent outcomes, and lack of generalizability and interpretability.

  In this research, we aim to explore a synergistic integration of two pieces of knowledge by developing hybrid physics-informed AI models to solve the fundamental problems in the SMT, mainly predicting the components’ movement through self-alignment and the thermal behavior of solder paste. The successful accomplishment of this research will contribute to improving the closed-loop parameter optimization framework for the PCB assembly process while preserving accurate and interpretable predictions.

• Liquid Metal Anode for Li-ion Batteries with Thin-film Solid Electrolyte - Hao Liu

  This proposal aims to explore the use of liquid metal as the negative electrode to couple with ceramic electrolyte films for flexible electronics applications. This work is expected to yield an assessment of the garnet-based Li-ion conducting films for practical energy storage applications.

  The proposed work will employ liquid Ga as the model liquid metal to evaluate its performance in battery cells with a solid electrolyte. Successful demonstration of the liquid metal anode coupled with a solid electrolyte will enable packaging batteries under ambient conditions.

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