Tong Hong Wang

Physical Behavior of Nanoporous Anodic Alumina Using Nanoindentation and Microhardness Tests

In this paper, the mechanical response and deformation behavior of anodic aluminum oxide (AAO) were investigated using experimental nanoindentation and Vickers hardness tests. The results showed the contact angle for the nanoporous AAO specimen was 105° and the specimen exhibited hydrophobic behavior. The hardness and the fracture strength of AAO were discussed and a three-dimensional finite element model (FEM) was also conducted to understand the nanoindentation-induced mechanism.

Mechanical characterization of nanoindented graphene via molecular dynamics simulations

The mechanical behavior of graphene under various indentation depths, velocities, and temperatures is studied using molecular dynamics analysis. The results show that the load, elastic and plastic energies, and relaxation force increased with increasing indentation depth and velocity. Nanoindentation induced pile ups and corrugations of the graphene. Resistance to deformation decreased at higher temperature. Strong adhesion caused topological defects and vacancies during the unloading process.

Transient Thermal Analysis for Board-Level Chip-Scale Packages Subjected to Coupled Power and Thermal Cycling Test Conditions

In this work, thermal characteristics of a board-level chip-scale package, subjected to coupled power and thermal cycling test conditions defined by JEDEC, are investigated through the transient thermal analysis. Tabular boundary conditions are utilized to deal with time-varying thermal boundary conditions brought by thermal cycling. It is obvious from the analysis that the presence of power cycling leads to a significant deviation of the junction temperature from the thermal cycling profile. However, for components away from the die, the deviation is insignificant. Moreover, for low-power applications, temperature histories from coupled power and thermal cycling are approximately linear combinations of temperature histories from pure power cycling and the ones from pure thermal cycling.

Correlation between power cycling and thermal cycling fatigue reliabilities of chip-scale packages

In this paper, the sequential thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, was carried out to investigate board-level fatigue reliabilities of TFBGA under accelerated power cycling test conditions. Experiments for steady state and transient thermal dissipations were conducted to verify the thermal analysis. Comparing between numerical results for power cycling and thermal cycling, it is noticed that for the tests similar low and high temperature extremes, power cycling leads to a much longer fatigue life than thermal cycling does, which indicates that thermal cycling is a more conservative criterion than power cycling is in evaluating the fatigue resistance of the electronic packages.

Thermal-mechanical coupling analysis for coupled power and thermal cycling reliability of chip-scale packages

The sequential thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermo-mechanical deformations, is carried out in this paper to investigate thermal characteristics along with fatigue reliability of board-level thin-profile fine-pitch ball grid array chip-scale packages under coupled power and thermal cycling test conditions. Pure thermal cycling and pure power cycling test conditions are also examined and compared.

Nanoindentation characteristics of clamped freestanding Cu membranes

This research employed instrumented nanoindentation to address the issue of bending to stretching-induced deformation of clamped freestanding Cu membranes. The experimental results show that indentation-induced plastic deformation only comes into effect at the centre and the indented edge of the Cu membrane when the indenter is applied, while the other locations remain undamaged. A step-by-step evolution was presumed for the time histories of the bending to stretching-induced deformation and for the timing of the significant change in slope of the load-deflection curve. Deformation was deliberately introduced at the transition from the single-point bending indentation to the surface stretching indentation at the impact location touched with the indenter. Good elastic recovery was found at locations away from the indenter. A similar finding can be arrived at by means of finite element analysis.

Coupled Power and Thermal Cycling Reliability of Board-Level Package-on-Package Stacking Assembly

In this paper, the sequential thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, is performed to investigate thermal characteristics along with fatigue reliability of a board-level package-on-package (PoP) stacking assembly under coupled power and thermal cycling test conditions. Effects of powering sequences on thermal characteristics and fatigue reliability of the PoP are examined. The numerical analysis shows that coupled power and thermal cycling creates temperature excursions based on the thermal cycling profile. Also, reliability of the PoP is highly related to the range of temperature excursions and the degree of deviation of the temperature profile from the thermal cycling profile.

Reliability evaluations for board-level chip-scale packages under coupled power and thermal cycling test conditions☆

Abstract To evaluate conjointly the effects of ambient temperature fluctuation and operation bias on the reliability of board-level electronic packages, a coupled power and thermal cycling test has been proposed. In this study, the sequential thermal–mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, is performed to investigate thermal characteristics along with fatigue reliability of board-level thin-profile fine-pitch ball grid array chip-scale packages under coupled power and thermal cycling test conditions. Effects of different power cycling durations are studied. A pure thermal cycling condition is also examined and compared. Numerical results indicate that, for the coupled power and thermal cycling test, a shorter power cycling duration in general leads to a shorter fatigue life. However, the temperature compensation effect elongates the fatigue life under certain power cycling durations.

Study of factors affecting warpage of HFCBGA subjected to reflow soldering-liked profile

Abstract Package warpage is an important factor to the effect of yield of board assembly, delamination, solder joint fatigue reliability and other thermal stress issues. Reduction of warpage is always the ultimate purpose for enhancing the service life. HFBCGA equipped only peripheral stiffener ring is selected to investigate the effect of heating rate, with and without ball mounted, moisture sensitivity level, white-coated paint on package and glass gratings to the warpage subjected to a reflow soldering-liked profile. Releasing viscoelasticity at processing temperature, maintaining structural rigidity of the residual solder, certain moisture resistivity at MSL 3, and light white paint help on reducing the warpage along the reflow soldering-liked profile.

Board-level Reliability of Package-on-Package Stacking Assemblies Subjected to Coupled Power and Thermal Cycling Tests

In this work, the sequential thermal-mechanical coupling analysis, which solves in turn the transient temperature field and subsequent thermomechanical deformations, is performed to investigate thermal characteristics along with fatigue reliability of a board-level package-on-package (PoP) stacking assembly under coupled power and thermal cycling test conditions. Effects of powering sequences on thermal characteristics and fatigue reliability of the PoP are examined.