Stress Isolation Structures in MEMS Gyroscope Packages

2007 ◽  
Author(s):  
C. H. Yun ◽  
X. Zhang ◽  
V. Kumar ◽  
M. G. Edwards
Keyword(s):  
Finite Element ◽  
Thermal Stresses ◽  
Lead Frame ◽  
Package Design ◽  
Mems Gyroscope ◽  
Frame Design ◽  
Order Of Magnitude ◽  
Stress Isolation ◽  
The Impact ◽  
Design Ideas

This paper describes the impact of lead frame design to minimize mechanical and thermal stresses to a MEMS (micro-electromechanical systems) gyroscope in a plastic premold cavity package. Design ideas for incorporating stress-isolation structures by etching the die paddle in a lead frame were evaluated with finite element modeling (FEM) and experimental verifications. The results showed that the null drift due to external mechanical stress was significantly improved by more than one order of magnitude, and the temperature variation of the device output was also improved by 30%, both by mounting the device on the lead frame etched with stress-isolation structures.

Thermal Stresses in Layered Electronic Assemblies

1997 ◽  
Vol 119 (2) ◽  
pp. 127-132 ◽  
Author(s):  
Z. Q. Jiang ◽  
Y. Huang ◽  
A. Chandra
Keyword(s):  
Finite Element ◽  
Thermal Stresses ◽  
Interfacial Shear Stress ◽  
Beam Theory ◽  
Accurate Method ◽  
Accurate Estimate ◽  
Electronic Packages ◽  
Package Design ◽  
Adhesive Layers ◽  
Electronic Assemblies

Thermal stresses in layered electronic assemblies are one of the causes of the mechanical failure of electronic packages. A simple but accurate method of estimating these thermal stresses is needed for the design of these packages. A simple approach based on beam theory exists, but it suffers from nonequilibrium of the peeling stress distribution. An improved method that overcomes this drawback is proposed here. For layered electronics with thin adhesives, simple analytical expressions are obtained for interfacial shear stress and peeling stress, as well as for other stress components. The finite element method is used to verify these solutions. It shows excellent agreement between the finite element results and these simple solutions, especially when the moduli of adhesive layers are significantly lower than the moduli of the other layers. This method provides an accurate estimate of thermal stresses for use in package design involving thin and compliant interface or adhesive layers.

Benefit of textured CIGS cells for low reflecting nanogrid application

MRS Advances ◽  
2017 ◽  
Vol 2 (53) ◽  
pp. 3175-3180 ◽  
Author(s):  
Joop van Deelen ◽  
Y. Tezsevin ◽  
A. Omar ◽  
M. Xu ◽  
M. Barink
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Energy Dissipation ◽  
Electric Field Distribution ◽  
Optical Effect ◽  
Optical Losses ◽  
Optical Modeling ◽  
Order Of Magnitude ◽  
The Impact ◽  
Metal Nanowire

ABSTRACTWe show the results of nanotextured device designs combined with carefully placed nanogrids in order to minimize optical losses. Finite element method (FEM) based optical modeling indicates that the reflection of both the layer stack and the metal is diminished by the proposed configuration in which the metallic nanowires at the front of a device are placed into the relatively shallow crevices, whereby the metal is not covered by other materials of the cell stack. The electric field distribution and energy dissipation (i.e. absorption) diagrams of the texture show how the light is distributed and where it is absorbed. It shows that light is ‘concentrated’ in the tips of the texture (depending on the size and wavelength of the light). Simultaneously, for wavelengths above 750 nm there appears to be a reduction of the E-field in the lower part of the texture and, therefore, putting a metallic nanowire in this position has hardly any negative optical effect.Furthermore, the impact of the texture height up to 1000 nm and the nanowire width up to 150nm was systematically investigated for a texture and wire period of 500 nm. The spectra reveal dimension dependent and wavelength specific optical features. This is the case even if the flat nanowire remains fully exposed to the front glass medium (i.e. not embedded underneath absorbers). At a texture height of 900 nm, the reflection related current loss is reduced by an order of magnitude compared to flat layer stacks, virtually regardless of the width of the metal nanowire. This opens up exciting new ways of creating nano-metal containing devices without the usual optical losses.

Effect of Temperature Dependent Mechanical Properties on Thermal Stress in Cooled Turbine Blades

1982 ◽  
Vol 104 (2) ◽  
pp. 349-353 ◽  
Author(s):  
J. M. Allen
Keyword(s):  
Finite Element ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Turbine Blades ◽  
Effect Of Temperature ◽  
Cyclic Life ◽  
Temperature Dependent ◽  
Average Temperature ◽  
Order Of Magnitude ◽  
Computer Codes

Finite element analyses show that maximum thermal stresses in a typically cooled turbine blade are approximately 40 percent larger than they are if calculated assuming constant, average temperature material properties—even though the local-to-average properties vary only 2 to 3 percent. An error of this size in stress leads to an order of magnitude over prediction of cyclic life. This surprisingly large effect is explained by means of the solution for thermal stress in a flat plate with a thermal gradient through its thickness. In general, finite element computer codes allow for temperature dependency of properties, but some do not permit this dependency within an element. It is shown that this can be a serious limitation with higher-order elements.

Pound Wise and Penny Foolish? Weight Loss and The Dynamics of Health Care Spending

2011 ◽  
Vol 14 (2) ◽  
Author(s):  
Thomas G Koch
Keyword(s):  
Weight Loss ◽  
Cost Savings ◽  
Cost Effective ◽  
Economic Consequences ◽  
Health Care Spending ◽  
Order Of Magnitude ◽  
Dynamic Measures ◽  
The Cost ◽  
The Impact ◽  
The Relationship

Current estimates of obesity costs ignore the impact of future weight loss and gain, and may either over or underestimate economic consequences of weight loss. In light of this, I construct static and dynamic measures of medical costs associated with body mass index (BMI), to be balanced against the cost of one-time interventions. This study finds that ignoring the implications of weight loss and gain over time overstates the medical-cost savings of such interventions by an order of magnitude. When the relationship between spending and age is allowed to vary, weight-loss attempts appear to be cost-effective starting and ending with middle age. Some interventions recently proven to decrease weight may also be cost-effective.

scholarly journals Potential and limitations of finite element modelling in assessing structural integrity of coralline algae under future global change

2015 ◽  
Vol 12 (19) ◽  
pp. 5871-5883 ◽  
Author(s):  
L. A. Melbourne ◽  
J. Griffin ◽  
D. N. Schmidt ◽  
E. J. Rayfield
Keyword(s):  
Climate Change ◽  
Finite Element ◽  
Structural Integrity ◽  
Geometric Model ◽  
Algal Growth ◽  
Coralline Algae ◽  
Rocky Shores ◽  
Element Analysis ◽  
Scan Data ◽  
The Impact

Abstract. Coralline algae are important habitat formers found on all rocky shores. While the impact of future ocean acidification on the physiological performance of the species has been well studied, little research has focused on potential changes in structural integrity in response to climate change. A previous study using 2-D Finite Element Analysis (FEA) suggested increased vulnerability to fracture (by wave action or boring) in algae grown under high CO2 conditions. To assess how realistically 2-D simplified models represent structural performance, a series of increasingly biologically accurate 3-D FE models that represent different aspects of coralline algal growth were developed. Simplified geometric 3-D models of the genus Lithothamnion were compared to models created from computed tomography (CT) scan data of the same genus. The biologically accurate model and the simplified geometric model representing individual cells had similar average stresses and stress distributions, emphasising the importance of the cell walls in dissipating the stress throughout the structure. In contrast models without the accurate representation of the cell geometry resulted in larger stress and strain results. Our more complex 3-D model reiterated the potential of climate change to diminish the structural integrity of the organism. This suggests that under future environmental conditions the weakening of the coralline algal skeleton along with increased external pressures (wave and bioerosion) may negatively influence the ability for coralline algae to maintain a habitat able to sustain high levels of biodiversity.

A Fracture Mechanics Based Parametric Study of the Copper-to-Copper Direct Thermo-Compression Bonded Interface Using Finite Element Method

2013 ◽  
Author(s):  
Ah-Young Park ◽  
Satish Chaparala ◽  
Seungbae Park
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Parametric Study ◽  
Initial Crack ◽  
Bonding Interface ◽  
Interface Condition ◽  
Large Temperature ◽  
Bonded Interface ◽  
The Impact ◽  
Element Method

Through-silicon via (TSV) technology is expected to overcome the limitations of I/O density and helps in enhancing system performance of conventional flip chip packages. One of the challenges for producing reliable TSV packages is the stacking and joining of thin wafers or dies. In the case of the conventional solder interconnections, many reliability issues arise at the interface between solder and copper bump. As an alternative solution, Cu-Cu direct thermo-compression bonding (CuDB) is a possible option to enable three-dimension (3D) package integration. CuDB has several advantages over the solder based micro bump joining, such as reduction in soldering process steps, enabling higher interconnect density, enhanced thermal conductivity and decreased concerns about intermetallic compounds (IMC) formation. Critical issue of CuDB is bonding interface condition. After the bonding process, Cu-Cu direct bonding interface is obtained. However, several researchers have reported small voids at the bonded interface. These defects can act as an initial crack which may lead to eventual fracture of the interface. The fracture could happen due to the thermal expansion coefficient (CTE) mismatch between the substrate and the chip during the postbonding process, board level reflow or thermal cycling with large temperature changes. In this study, a quantitative assessment of the energy release rate has been made at the CuDB interface during temperature change finite element method (FEM). A parametric study is conducted to analyze the impact of the initial crack location and the material properties of surrounding materials. Finally, design recommendations are provided to minimize the probability of interfacial delamination in CuDB.

scholarly journals Ice Coverage Induced by Depositing a Water Drop onto the Supercooled Substrate at Extreme Low Vapor Pressure

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 691
Author(s):  
Yugang Zhao ◽  
Zichao Zuo ◽  
Haibo Tang ◽  
Xin Zhang
Keyword(s):  
Vapor Pressure ◽  
Substrate Temperature ◽  
Water Drop ◽  
Industrial Processes ◽  
Aircraft Icing ◽  
Ice Coverage ◽  
Fundamental Understanding ◽  
Order Of Magnitude ◽  
The Impact ◽  
Kinetics Of

Icing/snowing/frosting is ubiquitous in nature and industrial processes, and the accretion of ice mostly leads to catastrophic consequences. The existing understanding of icing is still limited, particularly for aircraft icing, where direct observation of the freezing dynamics is inaccessible. In this work, we investigate experimentally the impact and freezing of a water drop onto the supercooled substrate at extremely low vapor pressure, to mimic an aircraft passing through clouds at a relatively high altitude, engendering icing upon collisions with pendant drops. Special attention is focused on the ice coverage induced by an impinging drop, from the perimeter pointing outward along the radial direction. We observed two freezing regimes: (I) spread-recoil-freeze at the substrate temperature of Ts = −15.4 ± 0.2 °C and (II) spread (incomplete)-freeze at the substrate temperature of Ts = −22.1 ± 0.2 °C. The ice coverage is approximately one order of magnitude larger than the frozen drop itself, and counterintuitively, larger supercooling yields smaller ice coverage in the range of interest. We attribute the variation of ice coverage to the kinetics of vapor diffusion in the two regimes. This fundamental understanding benefits the design of new anti-icing technologies for aircraft.

scholarly journals The impact of drilling and slitting construction on damage field: evolution characteristics in low-permeability coal seam

2021 ◽  
Vol 37 ◽  
pp. 205-215
Author(s):  
Heng Chen ◽  
Hongmei Cheng ◽  
Aibin Xu ◽  
Yi Xue ◽  
Weihong Peng
Keyword(s):  
Finite Element ◽  
Rock Mass ◽  
Damage Mechanics ◽  
Effective Strain ◽  
Secondary Development ◽  
Distribution Area ◽  
Finite Element Program ◽  
Element Program ◽  
Mining Face ◽  
The Impact

ABSTRACT The fracture field of coal and rock mass is the main channel for gas migration and accumulation. Exploring the evolution law of fracture field of coal and rock mass under the condition of drilling and slitting construction has important theoretical significance for guiding efficient gas drainage. The generation and evolution process of coal and rock fissures is also the development and accumulation process of its damage. Therefore, based on damage mechanics and finite element theory, the mathematical model is established. The damage variable of coal mass is defined by effective strain, the elastoplastic damage constitutive equation is established and the secondary development of finite element program is completed by FORTRAN language. Using this program, the numerical simulation of drilling and slitting construction of the 15-14120 mining face of Pingdingshan No. 8 Mine is carried out, and the effects of different single borehole diameters, different kerf widths and different kerf heights on the distribution area of surrounding coal fracture field and the degree of damage are studied quantitatively. These provide a theoretical basis for the reasonable determination of the slitting and drilling arrangement parameters at the engineering site.

Sign in / Sign up

Export Citation Format

Share Document