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 2020-2021 Pooled Research Projects-a partnership between faculty and mentor companies.
2020-2021 Pooled Research Projects
Fabrication of 3-dimensional integrated photonicdevices via femtosecond laser micromachining
- Bonggu Shim
In this proposed research, we will first investigate the optimal parameters for femtosecond laser
micromachining of waveguides both in rigid and flexible glass substrates. Second, we will
implement fully 3-dimensional laser micromachining setup which will be used for manufacturing
integrated photonic devices. Third, we will utilize our 3-dimensional fabrication capability to
manufacture spatial light multiplexers called photonic lanterns.
Modeling Temperature-Dependent Properties ofSolder Interfaces - Manuel Smeu
Building on our recent computational work investigating the temperature-dependent elastic properties of
materials, we will now extend our efforts towards interfaces of solder assemblies. We will use a
combination of density functional theory (DFT) and ab initio molecular dynamics (AIMD) to investigate
the elastic moduli, Poisson’s and Pugh ratios of solder interfaces as a function of temperature. With these
data we will also analyse the hardness, Debye temperature, elastic wave velocity, and coefficient of thermal
conductivity as a function of temperature. In addition, we will also use the volume-energy relationship,
coupled with the Vinet equation of state to calculate the temperature-dependent coefficient of thermal
expansion of these materials. We are particularly interested in the Sn-Bi solder joint as well as other lowtemperature solders. With the combination of these computational
efforts we aim to identifying potential weak spots and failure
mechanisms in these junctions.
Inorganic Composite Phase Change Materials forPassive Thermal Management - Hao Liu
This proposal aims to develop high-energy-density inorganic salt hydrate/carbon foam composite
phase change materials for passive thermal cooling in electronics. This work is expected to yield
a form-stable carbon foam/Ba(OH)2·8H2O composite phase change material with four times as
much thermal energy storage density as the existing paraffin wax. The proposed project will
optimize the critical wetting property between carbon foam and Ba(OH)2·8H2O through a systemic
investigation of strategies for hydrophilic modification of carbon foam.
Multi-Material Additive Manufacturing of Non-Planar Flexible Substrates with ConformallyConductive
Traces for Integrated Electronics - Fuda Ning
Current additive manufacturing (AM) processes lack the ability to construct integrated
electronics with non-planar, conformally patterned features during a single build. In this
proposed research, we present a novel multi-axis multi-head AM approach for one-step
fabrication of non-planar flexible electronics. The objective is to advance fundamental
understanding of this innovative multi-material printing of electronics while integrating direct
ink writing, fused filament fabrication, and machining processes. The underlying materialprocess-structure-performance connection will be deciphered through numerical and
experimental investigations. The curve-shaped PET substrate with tailored surface roughness
will be created with the subsequent depositions of Cu and/or Ag traces and their geometrical,
structural, and electrical effectiveness will be assessed. In addition, the interfacial adhesion
and failure mechanisms will be elucidated by finite element analysis and mechanical testing
including peeling/shear tests and tension/bending fatigue tests. Finally, we will fabricate 3D
integrated circuits by multi-layer deposition to offer the embedded solutions that maximize
the functional capability for 3D integration/packaging.
Cyber-Physical and Intelligent Edge ComputingPlatform for Smart Connected Manufacturing”
- Wenfeng Zhao
The aim of this proposal is to develop KcASE (Figure 1, blue), a cyber-physical and intelligent
edge computing hardware platform for connected and intelligent industrial 4.0 paradigm. In
particular, we consider one use case for the state-of-the-art SMT (surface mount technologies)
inline manufacturing (Figure 1, gray) and real-time quality inspection (Figure 1, green). We plan
to accomplish two specific tasks to achieve the connectivity and intelligence extension to the entire
product line. First, we will develop a communication module with versatile interfaces (COM,
Ethernet, etc.,) that can be used for bidirectional communication among KcASE, 3
equipment and Koh Young Inspection machines. Second, we will integrate the communication
module with the latest embedded AI computing hardware and study efficient, distributed edgenode inference. Upon the success of this project, we envision that KcASE can pave the way for
comprehensive AI-driven, closed-loop process optimization strategies in SMT inline production.
KcASE can also be regarded as a feasibility exploration effort toward a potential future product,
i.e., an edge extension to KBOX for cost-effective industrial 4.0 deployment solutions.
Automated integration with micro/nanowirebasedfine-pitch interconnects for 3D packaging
- Kaiyan Yu
This project aims to create novel micro or nanowire-based fine-pitch interconnects for 3D
packaging using precisely controlled micro or nanowires. An automated, precise 3D manipulation
scheme is proposed to assemble multiple micro and nanowires in fluid suspension under electrical
field. A solution-based approach is designed fabricating interconnects using vertically aligned and
horizontally patterned micro or nanowires. This project addresses important challenges regarding
the precise and scalable assembly for high density interconnects in 3D packaging.
The Electromigration Behavior of Pb Free Solder Jointscontaining Bi: High Melt - Low
Melt SolderInterconnect Structures for SMT Applications - Eric Cotts
We will study the materials science of SAC/BiSn solder joints (e.g., SAC305/Bi42Sn, Fig. 1a)
and on such mixed assemblies when both board
and component are bumped (Fig. 1b), which
promise to provide lower temperature
assembly for a wide range of conditions. The
eutectic Bi42Sn solder alloy enables process
temperatures as low as 150o
C (Fig. 2) and is
widely available in paste form (the Bi42Sn1Ag
is a popular variant intended to improve
interfacial toughness in drop shock
loading). We propose to examine the
properties of mixed solder alloy joints with
combinations of SAC305 or SAC405 solder
balls, and Bi42Sn or Bi42Sn1Ag solder paste
(Fig.1). Key parameters will include the
thickness (volume) of the near eutectic BiSn paste, the peak reflow temperature and reflow time, and
fabrication parameters (in particular, variation of geometry from that of Fig. 1a to that of Fig. 1b).
We will examine microstructures of final joints, determining grain sizes
and orientations, as well as composition throughout the joints (including
Bi concentration). Mechanical characterization will include hardness and
shear characteristics of individual and mixed assembly solder joints.
Furthermore, characterizations of the current density limits of such SnBi mixed assemblies will be conducted over a range of current densities,
temperatures, and geometries, with focus on the newer geometry
illustrated in Fig. 1b. Fabrication of such samples will be by conventional
means. Building an understanding of the materials science of these new
solder joints will provide for reliable product design capability.
“Understanding and Preventing Voiding in Small Ni-SnJoints Through Design and Process
Control - Nikolay Dimitrov
This proposal addresses defects in Sn or solder based joints at scales ranging from BGA to ultra-fine flip chip
Microjoints in 2.5/3D assembly are commonly formed by small Sn or solder caps between opposing Cu or Ni
surfaces. Ongoing work funded by the IEEC is leading to a systematic characterization of the strongly
enhanced risk of Kirkendall voiding within the intermetallic bonds in microjoints on Cu surfaces. This
problem is found to be associated with the quality of the electroplated Cu and guidelines will be offered as to
how to minimize the risk.
An alternative is the use of Ni or Ni/Au coated pillars or pads. Very small Sn thicknesses and repeated
reflows, like in stacking of chips, and/or subsequent exposure to elevated temperatures may however lead the
intermetallic layers from opposing surfaces to meet. Alternatively, this may be done on purpose to provide
for solid support in repeated thermocompression bonding when stacking die or to eliminate concerns with
respect to electromigration and thermomigration through unfortunately oriented Sn grains. In either case,
collision between the highly irregular intermetallic surfaces tends to lead to the entrapment of a row of Sn
‘pockets’ which are finally drained of Sn, leaving severe voiding.
Another concern with slightly larger Ni based joints is the formation of large voids between the Ni3Sn4
intermetallic surface and the solder. Several research groups suggest that the formation of such voids is
inevitable once the intermetallic thickness starts to exceed 5µm.
It is proposed to characterize the effects of interactions between design, electroplating process chemistry and
parameters, assembly process parameters, and subsequent thermomechanical history on either of these
phenomena. The goal is to establish practical guidelines for how to minimize or, preferably, entirely
eliminate the voiding.
Machine learning application for controlling SMTreflow oven - Jia Deng & Sangwon
Research Problem: Thermal interface materials are a bottleneck to heat flow, and limit performance as performance increases.
Research Objective: The goal is to develop an alternative solution for thermal interface materials by metal additive manufacturing which provides lower thermal resistance and enables packages with heat fluxes up to ~1,000 W/cm2.
Technical Approach: We will develop the process parameters to additively fabricate Cu and/or AlSi10Mg structures on a die (CPU, GPU etc.) using Sn3Ag4Ti interlayer alloy by selective laser melting. The structures can be micro-channels, heat pipes or vapor chamber evaporators. Furthermore, we will look at the interface microstructure and composition of Si-interlayer alloy and Cu and/or AlSi10Mg-interlayer alloy by scanning electron microscopy (SE2, EDS, BEI) and transmission electron microscopy (SAED, BF, DF, EDS). Vibratory polishing, focused ion beam (FIB) and Argon beam ion milling will be used along conventional polishing techniques for sample preparation. We will evaluate the strength of the interfacial bonding by mechanical testing such as ball shear tests and finite element analysis simulations. Thermal properties of the fabricated heat sink structures will be experimentally measured using Frequency-Domain Thermoreflectance (FDTR) analysis across the interface. Finally, the performance of the additively fabricated heat sink will be evaluated experimentally and numerically in single phase and two-phase scenarios.
Anticipated Outcome: We will develop a process to additively fabricate thermal management devices onto the chip without using conventional thermal management solutions which lead to lower thermal resistance in the package.
Industry Impact: Current thermal interface materials will not be able to keep up with Moore’s Law, whereas our alternative solution will enable 10X increase in heat fluxes (~1,000 W/cm2). By our calculations, chips can run 10-20 °C cooler under heat fluxes of 100 W/cm2 in current microprocessors.
Nano-crystalline Planar Magnetic Components forhigh power density solid state transformer
in AC-DC Power Converters used for Integration of Li-ionbatteries to AC Systems - Pritam
Das & Scott Schiffres
Current power conversion is only 90% efficient, primarily due to losses in the magnetic components. This power
conversion is increasingly important for the power grid, vehicles, aerospace and defense. This proposal seeks a 3D
printed enhanced magnetic component that can reduce transformer losses, while maintaining a compact design. Our
goal is to develop technologies that will create a transformer with an efficiency of greater than 95%, a 50% reduction
in losses compared to today’s standards. 3D printed cores with varying processing conditions will be manufactured
and the effect of the processing on microstructure and magnetic properties will be investigated. This proposal will
be leveraged into larger future proposals.
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