A Finite Element Study of Geometric Modifications to Reduce Thermal Mismatch Curvature in Wafer Bonding

2007 ◽  
Author(s):  
Devasena Duraipandi ◽  
John M. Heck ◽  
Raymond K. Yee ◽  
Sang-Joon J. Lee
Keyword(s):  
Finite Element ◽  
Thermal Expansion ◽  
Wafer Bonding ◽  
Thermal Stresses ◽  
Silicon Wafers ◽  
Geometrical Approach ◽  
Thermal Expansion Mismatch ◽  
Mems Devices ◽  
Element Analysis ◽  
Wafer Curvature

Wafer-level packaging of RF MEMS devices offers an attractive option to reduce packaging cost significantly and ensures hermetic encapsulation of devices. Low-temperature cofired ceramic (LTCC) cap wafers are particularly favorable because they can be pre-patterned with through-wafer vias for integrated electrical contacts and high-density packaging, at a much lower cost than silicon wafers with similar features. However, thermal expansion mismatch between ceramic and silicon wafers at high bonding temperatures induces thermal stresses at the interface, resulting in wafer curvature. For example, a 150 mm silicon wafer 675 μm thick with a ceramic cap wafer 500 μm thick has been measured to exhibit out-of-flatness displacement as severe as of 1.7 mm at the center. While the curvature can be reduced significantly using low-thermal-expansion ceramic, such materials are non-standard and require custom formulation. Furthermore, as the wafer diameter is increased, thermal expansion mismatch becomes more problematic. Therefore, it is desirable to address the problem using a geometrical approach in addition to optimizing the ceramic for wafer bonding applications. The present study applies finite element analysis (FEA) to examine the potential for reducing such curvature by introducing slots in the ceramic cap wafer. Two-level factorial design simulations involving five parameters were conducted to investigate the effect of slot parameters on wafer curvature, using 2-D plane strain simulation of wafer cooling from 300 °C to 25 °C. The five parameters investigated were cap wafer thickness, slot width, slot depth, slot separation, and slot orientation. The nonlinear temperature dependence of thermal expansion was also examined based on test data for the ceramic wafers. Furthermore, a 3-D finite element simulation was conducted to compare the 2-D results to overall impact on wafer distortion. FEA results were compared with experimental curvature measurements on sample wafers measured by coordinate measuring machining (CMM). Simulated results suggest that introduction of slots shows reduction in wafer curvature, and the displacement can be reduced by as much as 25% based on the geometric parameter values for slots in the cap wafer.

Finite Element Analysis of Thermal Stresses in Circumferential Cast Clasps of Removable Partial Dentures

2007 ◽  
Vol 23 ◽  
pp. 229-232
Author(s):  
Liliana Sandu ◽  
Nicolae Faur ◽  
Cristina Bortun ◽  
Sorin Porojan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Stresses ◽  
Element Analysis ◽  
3 Dimensional ◽  
Thermal Changes ◽  
The Finite Element Analysis ◽  
Dimensional Finite Element ◽  
Back Action ◽  
Aggressive Effect

Several studies evaluated the removable partial dentures by the finite element analysis, but none of them evaluated thermal stresses. The purpose of the study was to explore the influence of thermal oral changes induced by hot/cold liquids and food on the circumferential cast clasps of removable partial dentures. A 3-dimensional finite element method was used to explore the temperature distribution, thermal stress and the influence of thermal changes on stresses and displacements of circumferential clasps during functions. Thermal variations induce stresses in dental clasps, high temperatures having a more aggressive effect than lower one. Cold liquids and food induce high stresses in the retentive clasp arms while hot ones in the occlusal rests of the clasps and for the back action clasp also in the minor connector. The study suggests the importance of consFigureidering thermal variations for stress analyses of the cast clasps.

Three Turnaround Heat Treating Studies

2003 ◽  
Author(s):  
Jaan Taagepera ◽  
Marty Clift ◽  
D. Mike DeHart ◽  
Keneth Marden
Keyword(s):  
Heat Treatment ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Stress ◽  
Thermal Stresses ◽  
Heat Treating ◽  
Element Analysis ◽  
Stress Profiles ◽  
Insight Into

Three vessel modifications requiring heat treatment were analyzed prior to and during a planned turnaround at a refinery. One was a thick nozzle that required weld build up. This nozzle had been in hydrogen service and required bake-out to reduce the potential for cracking during the weld build up. Finite element analysis was used to study the thermal stresses involved in the bake-out. Another heat treatment studied was a PWHT of a nozzle replacement. The heat treatment band and temperature were varied with location in order to minimize cost and reduction in remaining strength of the vessel. Again, FEA was used to provide insight into the thermal stress profiles during heat treatment. The fmal heat treatment study was for inserting a new nozzle in a 1-1/4Cr-1/2Mo reactor. While this material would ordinarily require PWHT, the alteration was proposed to be installed without PWHT. Though accepted by the Jurisdiction, this nozzle installation was ultimately cancelled.

Elastic Thermal Stresses in Bimetallic Pipe Welds

1980 ◽  
Vol 102 (4) ◽  
pp. 430-432 ◽  
Author(s):  
R. D. Blevins
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Intensity ◽  
Maximum Stress ◽  
Thermal Stresses ◽  
Simple Expression ◽  
Element Analysis ◽  
Maximum Stress Intensity ◽  
Bimetallic Pipe ◽  
Uniform Change

The elastic thermal stresses in a welded transition between two pipes of the same size but different alloys are explored. A stress-free temperature is postulated and the stress due to a uniform change in temperature is characterized by the maximum stress intensity in the weld. A simple expression for predicting this maximum stress intensity is developed based on the results of finite element analysis.

Linear Thermomechanical Microactuators

1999 ◽  
Author(s):  
Rebecca Cragun ◽  
Larry L. Howell
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Expansion ◽  
Cross Sections ◽  
Variable Cross ◽  
Element Analysis ◽  
Thermal Actuators ◽  
Output Force ◽  
Analysis Models ◽  
High Output

Abstract Thermomechanical in-plane microactuators (TIMs) have been designed, modeled, fabricated, and tested. TIMs offer an alternative to arrays of smaller thermal actuators to obtain high output forces. The design is easily modified to obtain the desired output force or deflection for specific applications. The operational principle is based on the symmetrical thermal expansion of variable cross sections of the surface micromachined microdevice. Sixteen configurations of TIMs were fabricated of polysilicon. Finite element analysis models were used to predict the deflection and output force for the actuators. Experimental results were also recorded for all sixteen configurations, including deflections and output forces up to 20 micron and 35 dyne.

Thermal stresses in multilevel interconnections: Aluminum lines at different levels

1997 ◽  
Vol 12 (9) ◽  
pp. 2219-2222 ◽  
Author(s):  
Y-L. Shen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Thermal Stresses ◽  
Element Analysis ◽  
Future Studies ◽  
Level Lines ◽  
The Finite Element Analysis ◽  
Staggered Arrangement ◽  
Upper Level ◽  
Different Levels

Numerical results on the evolution of thermal stresses in multilevel interconnects are presented. Two levels of aluminum lines with an aspect ratio of unity, aligned vertically or arranged in a staggered manner, are considered by recourse to the finite element analysis. The stresses are found to be significantly higher in the lower-level lines than in the upper-level lines, for both the aligned and staggered arrangements. The stress magnitudes are generally smaller in lines of staggered arrangement, compared to the case of aligned lines. Implications of the present findings are discussed, with directions of future studies highlighted.

Finite Element Analysis of Casing Material Behavior in Steam Injection Well Operations

2015 ◽  
Vol 799-800 ◽  
pp. 196-200
Author(s):  
Abhilash M. Bharadwaj ◽  
Sonny Irawan ◽  
Saravanan Karuppanan ◽  
Mohamad Zaki bin Abdullah ◽  
Ismail bin Mohd Saaid
Keyword(s):  
Finite Element ◽  
Oil Recovery ◽  
Thermal Stresses ◽  
Oil And Gas ◽  
Extreme Temperature ◽  
Injection Pressure ◽  
Oil And Gas Industry ◽  
Steam Injection ◽  
Material Behavior ◽  
Element Analysis

Casing design is one of the most important parts of the well planning in the oil and gas industry. Various factors affecting the casing material needs to be considered by the drilling engineers. Wells partaking in thermal oil recovery processes undergo extreme temperature variation and this induces high thermal stresses in the casings. Therefore, forecasting the material behavior and checking for failure mechanisms becomes highly important. This paper uses Finite Element Methods to analyze the behavior two of the frequently used materials for casing - J55 and L80 steels. Modeling the casing and application of boundary conditions are performed through Ansys Workbench. Effect of steam injection pressure and temperature on the materials is presented in this work, indicating the possibilities of failure during heating cycle. The change in diameter of the casing body due to axial restriction is also presented. This paper aims to draw special attention towards the casing design in high temperature conditions of the well.

Comprehending Occurrence of Premature Failure in Compressor Turbine (CT) Blades for Short-Haul Aircraft Fleet

2019 ◽  
Vol 42 ◽  
pp. 10-23
Author(s):  
Joshua Kimtai Ngoret ◽  
Venkata Parasuram Kommula
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Pressure ◽  
Thermal Stresses ◽  
Geometrical Model ◽  
Mechanical Stresses ◽  
Element Analysis ◽  
Premature Failure ◽  
Structural Stresses ◽  
Transient Thermal

This paper presents results from modeling of Compressor Turbine (CT) blades for short-haul aircraft fleet occasioned by thermo-mechanical stresses in order to comprehend the occurrence of premature failure. A 3D PT6A-114A engine high pressure (HP) CT blade geometrical model was developed in commercial CAD-SolidWorks, then imported to ANSYS 15.0 environment for finite element analysis (FEA). The CT blade was investigated for transient thermal stresses from heat generated by the combustors and static structural stresses from rotational velocities of the engine which account for 80% of inertial field during flight. The results revealed that the blades could have served for another 1.44% of the time they were in service.

A Review of Optimising the Design of a New Coke Drum Skirt

2019 ◽  
Author(s):  
Alex Berry ◽  
Warren Brown ◽  
Antonio Seijas ◽  
Sarah Cook
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Literature Review ◽  
Thermal Stresses ◽  
Fatigue Cracking ◽  
Element Analysis ◽  
Long Life ◽  
Welded Connection

Abstract Coke drums are subjected to severe thermal cycling with the skirt to shell connection weld being vulnerable to fatigue cracking. It is essential this connection is well designed to ensure a long life before repairs are inevitably required. Much has been written on coke drum skirt design with the aim of reducing the thermal stresses and strains encountered at the skirt connection weld, some designs have removed the weld completely allowing the drum to sit in an “egg-in-cup” arrangement. This paper includes a short literature review discussing Coke drum skirt designs and explains skirt behaviour during the drum cycle that results in eventual skirt cracking. A case study is reviewed in detail for a new pair of coke drums, where the predicted fatigue life of the chosen welded connection is assessed using axisymmetric, quarter symmetry and half symmetry finite element analysis supported by thermocouple data. The optimised design focuses on a conventional tangential design where the effects of the essential variables such as skirt thickness, skirt connection location, skirt-to head-gap and slot design (length, location & spacing) have been modelled and optimised to obtain a skirt design that produces the longest fatigue life for the intended duty cycle. Coke drum skirts must be installed onto the shell to exacting tolerances during manufacture to ensure concentricity and minimal gap between the skirt and shell. A brief overview of how this is achieved will be presented.

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