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Page 57
May 20-21, 2019 | Vienna, Austria
Biomaterials and Nanomaterials &
Materials Physics and Materials Science
2
nd
International Conference on
Journal of Materials Science and Nanotechnology | Volume 3
Notes:
Some critical problems of the mechanical behavior and performance of electronic
and optical materials, assemblies and systems: Application of analytical
(“mathematical”) modeling
E Suhir
Portland State University, USA
S
ome critical problems of the mechanical behavior
and performance of electronic and optical materials,
assemblies and systems are addressed and discussed. It
is shown that application of analytical modeling (always
confirmed by finite-element-analyses) enables to reveal
and explain the underlying physics associated with such,
often non-obvious, always non-trivial and sometime
even paradoxical, problems and situations. Most of the
problems were encountered by the first author during his
tenure with Bell Labs (basic research area, Murray Hill,
NJ), University-of-California at Santa Cruz, Portland State
University at Portland, OR, and small business innovative
research (SBIR) ERS Co., USA. The following major
problems are addressed: magnitude and distribution of
the interfacial thermal stresses in adhesively bonded or
soldered assemblies; incentive for using low modulus
bonding materials and, in some cases, materials with low
yield stress; assemblies bonded at the ends; incentive
for using test specimens with transverse grooves in
the bonded materials for lower and more uniformly
distributed interfacial stresses; thermostatic compensation
in temperature-sensitive devices using conventional
materials (as opposite to ceramics with negative CTE);
bow-free (temperature change insensitive) assemblies;
thermal and lattice mismatch stresses in semiconductor
crystal grown assemblies; ability to adequately mimic drop
test conditions using shock testers; demonstration that
the maximum acceleration is not always the adequate
criterion of the dynamic strength of an electronic product,
and that a static short-term load could be more damaging
than the dynamic one; combined action of tensile and
bending deformations of the PCBs subjected to drop tests
and ability to obtain closed-form and even exact solutions
for highly nonlinear shock-excited vibrations, such as, e.g.,
those taking place during drop tests on the board level;
role of upper harmonics during drop tests; nonlinear
response of the rocket PCB (with surface-mounted
devices on it) to the sudden acceleration applied to its
support contour; modeling situations, when the dynamic
response of a linear or a non-linear electronic system
subjected to a short-time loading can be substituted with
an instantaneous impulse; stress relief in solder joints of
the second level of interconnections (package to PCB)
owing to larger stand-off heights of the solder joints;
incentive for using inhomogeneous solder joint systems
for lower thermally induced stresses; thermal stress in
flexible electronics; ability to predict the threshold of
the added transmission losses in jacketed (single coated)
optical fibers using mechanical considerations; incentive
for mechanical pre-stressing of accelerated test specimens
subjected to thermal loading; ability to relieve stress in
thermoelectric module designs using thinner and longer
legs; reducing bending stress in optical fiber interconnects
by properly rotating their ends; low-temperature micro-
bending of long-haul dual-coated optical fibers; two-
point bending of optical fiber specimens. It is concluded
that all the three basic approaches in microelectronics
and photonics materials science and engineering -
analytical (“mathematical”) modeling, numerical modeling
(simulation) and experimental investigations - are equally
important in understanding the physics of the materials
behavior and in designing, on this basis, viable and reliable
electronic devices and products. As to analytical modeling,
it is a powerful tool that enables one to explain critical
and often paradoxical situations in the behavior and
performance of electronic materials and products, and to
make a viable device into a reliable product.
e
:
suhire@aol.com