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.

Interfacial Thermal Stress Analysis of Anisotropic Multi-Layered Electronic Packaging Structures

1999 ◽  
Vol 122 (1) ◽  
pp. 61-66 ◽  
Author(s):  
Weidong Xie ◽  
Suresh K. Sitaraman
Keyword(s):  
Deformation Theory ◽  
Thermal Stresses ◽  
High Stress ◽  
Free Edge ◽  
Layered Structures ◽  
Thermal Gradients ◽  
Electronic Packages ◽  
Element Analysis ◽  
Laminate Theory ◽  
Electronic Assemblies

The presence of dissimilar material systems and thermal gradients introduce thermal stresses in multi-layered electronic assemblies and packages during fabrication and operation. The high stress gradients near the free edge of bonding interfaces of such structures may cause cracking and delamination leading to the failure or malfunction of electronic assemblies and packages. A simple but accurate engineering approach for the calculation of interlaminar thermal stresses due to thermal mismatch in multi-layered structures is needed so that designers can determine interlaminar thermal stresses easily without much computational efforts. A few approaches based on the generalized deformation theory have been published but most of them are only suitable for structures with symmetric layers. For electronic packages and assemblies, unsymmetric layers are often used. An improved approach, Classical Laminate Theory-Edge Stress Shape (CLT-ESS), for prediction of interlaminar thermal stresses that can be applied to multi-layered structures with unsymmetric layers is presented. Comparisons are made with finite element analysis results and are found to be favorable. The proposed approach provides an efficient way for the calculation of interlaminar thermal stresses. [S1043-7398(00)00901-4]

Structural Analyses of Spacecraft Electronic Packages

1992 ◽  
Vol 114 (1) ◽  
pp. 96-99
Author(s):  
S. Kannappan ◽  
V. Kunukkassril
Keyword(s):  
Finite Element ◽  
Random Vibration ◽  
Static Solution ◽  
Mode Shapes ◽  
Load Factor ◽  
Vibration Test ◽  
Electronic Packages ◽  
Circuit Boards ◽  
Test Conditions ◽  
Electronic Assemblies

The spacecraft electronic assemblies are subjected to severe environmental conditions during testing, launching and during orbit mission. The success of the mission depends upon the proper functioning of these critical electronic modules. The structural analyses using Finite Element Methods (FEM) assure the integrity of these components. A typical box, Array Drive Electronics (ADE), for TIROS satellites [1] is discussed in this article. The NASTRAN software was used to perform the stress and modal analyses of the box assembly with five circuit boards, covers and mounting feet. The stress analysis was performed for a static solution. As a conservative loading, 3 sigma load factor was used in the calculation of the acceleration values from the random vibration test conditions. Margins of safety were calculated. Design and material changes were recommended. The mode shapes fall in to three groups as explained in the text.

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.

Post-buckling inelastic analysis of thin-walled metal members using the Generalised Beam Theory

2019 ◽  
Author(s):  
Miguel Abambres ◽  
Dinar Camotim ◽  
Miguel Abambres
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Beam Theory ◽  
Flow Theory ◽  
Promising Alternative ◽  
Inelastic Analysis ◽  
Post Buckling ◽  
Thin Walled ◽  
Shell Finite Element ◽  
Generalised Beam Theory

A 2nd order inelastic Generalised Beam Theory (GBT) formulation based on the J2 flow theory is proposed, being a promising alternative to the shell finite element method. Its application is illustrated for an I-section beam and a lipped-C column. GBT results were validated against ABAQUS, namely concerning equilibrium paths, deformed configurations, and displacement profiles. It was concluded that the GBT modal nature allows (i) precise results with only 22% of the number of dof required in ABAQUS, as well as (ii) the understanding (by means of modal participation diagrams) of the behavioral mechanics in any elastoplastic stage of member deformation .

First and Second Order Elastoplastic Analyses of Thin-Walled Metal Members using Generalized Beam Theory

2018 ◽  
Author(s):  
Miguel Abambres
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Cross Section ◽  
Beam Theory ◽  
Second Order ◽  
Flow Rule ◽  
Non Linear ◽  
Thin Walled ◽  
Shell Finite Element ◽  
Generalized Beam Theory

Original Generalized Beam Theory (GBT) formulations for elastoplastic first and second order (postbuckling) analyses of thin-walled members are proposed, based on the J2 theory with associated flow rule, and valid for (i) arbitrary residual stress and geometric imperfection distributions, (ii) non-linear isotropic materials (e.g., carbon/stainless steel), and (iii) arbitrary deformation patterns (e.g., global, local, distortional, shear). The cross-section analysis is based on the formulation by Silva (2013), but adopts five types of nodal degrees of freedom (d.o.f.) – one of them (warping rotation) is an innovation of present work and allows the use of cubic polynomials (instead of linear functions) to approximate the warping profiles in each sub-plate. The formulations are validated by presenting various illustrative examples involving beams and columns characterized by several cross-section types (open, closed, (un) branched), materials (bi-linear or non-linear – e.g., stainless steel) and boundary conditions. The GBT results (equilibrium paths, stress/displacement distributions and collapse mechanisms) are validated by comparison with those obtained from shell finite element analyses. It is observed that the results are globally very similar with only 9% and 21% (1st and 2nd order) of the d.o.f. numbers required by the shell finite element models. Moreover, the GBT unique modal nature is highlighted by means of modal participation diagrams and amplitude functions, as well as analyses based on different deformation mode sets, providing an in-depth insight on the member behavioural mechanics in both elastic and inelastic regimes.

Natural frequency analysis of a functionally graded rotor-bearing system with a slant crack subjected to thermal gradients

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Arnab Bose ◽  
Prabhakar Sathujoda ◽  
Giacomo Canale
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Power Law ◽  
Beam Theory ◽  
Functionally Graded ◽  
Thermal Gradients ◽  
Element Analysis ◽  
Rotor Bearing ◽  
Natural Frequency Analysis ◽  
Bearing System

Abstract The present work aims to analyze the natural and whirl frequencies of a slant-cracked functionally graded rotor-bearing system using finite element analysis for the flexural vibrations. The functionally graded shaft is modelled using two nodded beam elements formulated using the Timoshenko beam theory. The flexibility matrix of a slant-cracked functionally graded shaft element has been derived using fracture mechanics concepts, which is further used to develop the stiffness matrix of a cracked element. Material properties are temperature and position-dependent and graded in a radial direction following power-law gradation. A Python code has been developed to carry out the complete finite element analysis to determine the Eigenvalues and Eigenvectors of a slant-cracked rotor subjected to different thermal gradients. The analysis investigates and further reveals significant effect of the power-law index and thermal gradients on the local flexibility coefficients of slant-cracked element and whirl natural frequencies of the cracked functionally graded rotor system.

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