Flip-Chip BGA Design to Avert Die Cracking

1999 ◽  
Vol 123 (1) ◽  
pp. 58-63 ◽  
Author(s):  
J.-B. Han
Keyword(s):  
Fracture Mechanics ◽  
Crack Length ◽  
Material Properties ◽  
Flip Chip ◽  
Design Guidelines ◽  
Design Parameters ◽  
Substrate Thickness ◽  
Element Analysis ◽  
Critical Crack Length ◽  
Fracture Parameters

Fracture mechanics is applied to flip-chip BGA design to avert die cracking from its backside. Fracture mechanics is integrated with the finite element analysis (FEA) and design of virtual experiments (virtual DOE) to analyze the effects of location and length of a die crack, and the effects of some key material properties and package dimensions on die cracking of flip-chip BGA. The stress intensity factor (SIF) and the strain energy release rate (ERR) are taken as the design indices. The FEA is used to calculate the fracture parameters, and the virtual DOE is employed to determine contributions of each design parameter to die cracking and their acceptable design windows. The investigation consists of two parts. The first is relations of length and location of a die crack with the fracture parameters. The relations are established through sweeping along crack length for a crack located at the center of the die backside, and along the die backside surface. The critical crack length is determined for a specific design. The second is the virtual DOE based on fracture mechanics. Several key material properties and package dimensions are used as the design inputs. The main effects and interactions of these design parameters to die cracking are calculated. Based on it, some generic design guidelines are made. It is concluded that substrate and die thicknesses are the two most significant factors to die cracking of flip-chip BGA. Increasing substrate thickness and reducing die thickness are the most effective measures to design a package with high resistance to die cracking.

Optimizing System-on-Film (SOF) Design Using Finite Element Analysis

2011 ◽  
Author(s):  
Vikram Venkatadri ◽  
Mark Downey ◽  
Xiaojie Xue ◽  
Dipak Sengupta ◽  
Daryl Santos ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Flip Chip ◽  
Flexible Substrate ◽  
High Density ◽  
Design Solution ◽  
Design Parameters ◽  
Optimized Design ◽  
Element Analysis ◽  
Bonding Parameters

System-On-Film (SOF) module is a complex integration of a fine pitch high density die and surface mounted discrete devices on a polyimide (PI) film laminate. The die is connected to the film using a thermo-compression flip-chip bonding (TCB) process which is capable of providing a very high density interconnect at less than 50um pitch. Several design and bonding parameters have to be controlled in order to achieve a reliable bond between the Au bumps on the die and the Sn plated Cu traces on the PI film. In the current work, the TCB process is studied using Finite Element Analysis (FEA) to optimize the design parameters and assure proper process margins. The resultant forces acting on the bump-to-trace interfaces are quantified across the different potential geometrical combinations. Baseline simulations showed higher stresses on specific bump locations and stress gradients acting on the bumps along the different sides of the die. These observations were correlated to both the failures and near failures on the actual test vehicles. Further simulations were then utilized to optimize and navigate design tradeoffs at both the die and flexible substrate design levels for a more robust design solution. Construction analysis performed on parts built using optimized design parameters showed significant improvements and correlated well with the simulation results.

On the Multiscale Finite Element Analysis for Interfacial Fracture in Cu/Low-K Interconnects

2007 ◽  
Author(s):  
Tz-Cheng Chiu ◽  
Huang-Chun Lin
Keyword(s):  
Thin Film ◽  
Fracture Mechanics ◽  
Interface Crack ◽  
Integrated Circuit ◽  
Flip Chip ◽  
Thermal Loading ◽  
Global Analysis ◽  
Crack Problem ◽  
Element Analysis ◽  
Low K

The interface crack problem in integrated circuit devices was considered by using global and local modeling approach. In the global analysis the thin film interconnect was modeled by a homogenized layer with material constants obtained from representative volume element (RVE) analysis. Local analyses were then considered to determine fracture mechanics parameters. It was shown that the multiscale model with RVE approach gives accurate fracture mechanics parameters for an interface crack under either thermal or mechanical loads; while significant error was observed when the thin film layers are ignored in the global analysis. The problem of an interface crack between low-k dielectric and etch-stop thin film in a flip-chip package under thermal loading was also investigated as an application example of the multiscale modeling.

FEM Analysis of Thermal Stresses in Advanced Electronic Packages

1998 ◽  
Vol 516 ◽  
Author(s):  
Sven Rzepka ◽  
Matt A. Korhonen ◽  
Che-Yu Li ◽  
Ekkehard Meusel
Keyword(s):  
Finite Element ◽  
Flip Chip ◽  
Thermal Stresses ◽  
Low Cost ◽  
Fem Analysis ◽  
Design Guidelines ◽  
Material Behavior ◽  
General Tendency ◽  
Element Analysis ◽  
Chip Size

AbstractFollowing the general tendency of downsizing in microelectronic packages, the interposing layer between silicon chip and organic board is constantly reduced while the differences in thermal expansion stay constant. Consequently, thermal stresses have become the most important reliability concern in advanced packages. Finite element analysis is known as an effective way of theoretically studying the mechanical situation in multi-component systems with complex material behavior. The paper presents results of finite element simulations that provide practical guidance for design, process and material developments of chip size packaging (CSP), flip chip (FC), and direct chip attach (DCA) modules. Using realistic and efficient models, a low-cost CSP concept is assessed, the effects of underfill, underfill imperfections, and underfill defects on the reliability of FC modules are studied, and an optimum set of mechanical properties for underfill materials is proposed. Finally, reliability risk factors in DCA modules are identified and preliminary design guidelines are given.

Finite Element Analysis of Functionally Graded Thick-Cylinders Subjected to Mechanical and Thermal Loads

2012 ◽  
Author(s):  
Jasem A. Ahmed ◽  
M. A. Wahab
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Radial Direction ◽  
Coefficient Of Thermal Expansion ◽  
Stress Component ◽  
Pressure Vessels ◽  
Functionally Graded ◽  
Design Parameters ◽  
Element Analysis

Functionally graded materials (FGM) are used to design structures used in high temperature environment. Hybrid pressure vessels can be designed from FGMs to incorporate improved strength, weight reduction, thermal properties, impact resistance etc. Progressive research in this area will lead to the determination of optimum design parameters and provide insight in developing manufacturing techniques of full-scale hybrid pressure vessels and experimental validation. In future, an accurate damage model will help in planning component examinations in a selective manner in order to provide useful information about material condition and predict the remaining life of the structure. A functionally graded thick-walled cylindrical vessel with varying material properties in the radial direction is considered. The cylinder is assumed to be made of one phase spatially dispersed in a matrix of another. Volume fractions of the phases are assumed to vary along the radial direction according to power laws. The gradation is represented by dividing the radial domain into finite sub-domains. The effective material properties such as modulus of elasticity, Poisson’s ratio, thermal conductivity and coefficient of thermal expansion are estimated using Mori-Tanaka [1], Hashin–Shtrikman [2], Hatta-Taya [3] and Rosen-Hashin [4] relations. The hollow cylinder is subjected to axisymmetric mechanical and thermal loadings. Finite Element Analysis is performed using a commercial package, ANSYS, to obtain temperature and stress component distribution along the thickness of the cylinder. Results are presented graphically to show the effect of internal pressure, temperature change, and gradient variation of material properties on stress components throughout the thickness.

Fractal Finite-Element Based Continuum Shape Sensitivity Analysis of Cracks

2007 ◽  
Author(s):  
B. N. Rao ◽  
R. M. Reddy
Keyword(s):  
Sensitivity Analysis ◽  
Finite Element ◽  
Fracture Mechanics ◽  
Fracture Initiation ◽  
Actual Behavior ◽  
Shape Sensitivity ◽  
Shape Sensitivity Analysis ◽  
Element Analysis ◽  
Probabilistic Fracture Mechanics ◽  
Fracture Parameters

Probabilistic fracture mechanics (PFM) that blends the theory of fracture mechanics and the probability theory provides a more rational means to describe the actual behavior and reliability of structures. However in PFM, the fracture parameters and their derivatives are often required to predict the probability of fracture initiation and/or instability in cracked structures. The calculation of the derivatives of fracture parameters with respect to load and material parameters, which constitutes size-sensitivity analysis, is not unduly difficult. However, the evaluation of response derivatives with respect to crack size is a challenging task, since it requires shape sensitivity analysis. Using a brute-force type finite-difference method to calculate the shape sensitivities is often computationally expensive, in that numerous repetitions of deterministic finite element analysis may be required for a complete reliability analysis. Therefore, an essential need of probabilistic fracture-mechanics is to evaluate the sensitivity of fracture parameters accurately and efficiently.

scholarly journals Investigating inlay designs of class II cavity with deep margin elevation using finite element method

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Yung-Chung Chen ◽  
Chi-Lun Lin ◽  
Chun-Hsien Hou
Keyword(s):  
Finite Element ◽  
Stress Responses ◽  
Mechanical Performance ◽  
Material Selection ◽  
Design Guidelines ◽  
Geometric Design ◽  
Design Parameters ◽  
Element Analysis ◽  
Tooth Structure ◽  
Deep Margin

Abstract Background This study evaluates the mechanical performance of deep margin elevation technique for carious cavities by considering the shape designs and material selections of inlay using a computational approach combined with the design of experiments method. The goal is to understand the effects of the design parameters on the deep margin elevation technique and provide design guidelines from the biomechanics perspective. Methods Seven geometric design parameters for defining an inlay’s shape of a premolar were specified, and the influence of cavity shape and material selection on the overall stress distribution was investigated via automated modelling. Material selection included composite resin, ceramic, and lithium disilicate. Finite element analysis was performed to evaluate the mechanical behavior of the tooth and inlay under a compressive load. Next, the analysis of variance was conducted to identify the parameters with a significant effect on the stress occurred in the materials. Finally, the response surface method was used to analyze the stress responses of the restored tooth with different design parameters. Results The restored tooth with a larger isthmus width demonstrated superior mechanical performance in all three types of inlay materials, while the influence of other design parameters varied with the inlay material selection. The height of the deep margin elevation layer insignificantly affected the mechanical performance of the restored tooth. Conclusions A proper geometric design of inlay enhances the mechanical performance of the restored tooth and could require less volume of the natural dentin to be excavated. Furthermore, under the loading conditions evaluated in this study, the deep margin elevation layer did not extensively affect the strength of the tooth structure.

Fatigue Life Estimation of Pitted Specimens by Means of an Integrated Fracture Mechanics Approach

2016 ◽  
Author(s):  
Nicolas O. Larrosa ◽  
Mirco D. Chapetti ◽  
Robert A. Ainsworth
Keyword(s):  
Fatigue Life ◽  
Fracture Mechanics ◽  
Crack Length ◽  
Driving Force ◽  
Hot Spot ◽  
Fatigue Cracks ◽  
Stress Concentrations ◽  
Engineering Structures ◽  
Premature Failure ◽  
Critical Crack Length

The synergistic nature of corrosion and fatigue is one of the main reasons for the premature failure of engineering structures and components. The decrease in fatigue life of specimens subjected to aggressive environments is likely to be attributed to local, pit-induced, stress concentrations that cause premature initiation of fatigue cracks. In this work, we have developed a predictive approach to assess the life of specimens containing pits assuming the pit both as a crack and as a smooth notch. The proposed approach assumes that even though the critical place for crack initiation seems to be the pit mouth, once the crack initiates, during propagation, the location of the hot spot shifts according to the location of the crack tip and due to the redistribution of stresses and strains. An integrated fracture mechanics approach that compares the driving force of the crack emanating from the pit and the evolution of the material threshold to crack propagation with crack length is proposed. The material threshold is estimated from the plain fatigue endurance limit, the position d of the strongest microstructural barrier and the SIF threshold for long cracks. The effective driving force is assessed by means of parametric FEA. This approach considers the influence of the pit geometry on the stress field surrounding the crack providing a more realistic estimate of the applied driving force. The maximum applied stress range as a function of number of cycles (S-N curves) have been estimated for different configurations (stress level, initial crack length, location at the crack front) assuming that failure of the component will be given when the critical crack length is reached. The procedure has been first developed and used to assess deep pits, as these are the most detrimental and common configuration encountered in real Oil and Gas applications.

scholarly journals Study on the Strip Warpage Issues Encountered in the Flip-Chip Process

Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 323
Author(s):  
Wan-Chun Chuang ◽  
Wei-Long Chen
Keyword(s):  
Structural Design ◽  
Flip Chip ◽  
Design Guidelines ◽  
Strip Thickness ◽  
Substrate Thickness ◽  
Factors Affecting ◽  
Development Costs ◽  
Development Cycle ◽  
Experimental Values ◽  
Die Thickness

This study successfully established a strip warpage simulation model of the flip-chip process and investigated the effects of structural design and process (molding, post-mold curing, pretreatment, and ball mounting) on strip warpage. The errors between simulated and experimental values were found to be less than 8%. Taguchi analysis was employed to identify the key factors affecting strip warpage, which were discovered to be die thickness and substrate thickness, followed by mold compound thickness and molding temperature. Although a greater die thickness and mold compound thickness reduce the strip warpage, they also substantially increase the overall strip thickness. To overcome this problem, design criteria are proposed, with the neutral axis of the strip structure located on the bump. The results obtained using the criteria revealed that the strip warpage and overall strip thickness are effectively reduced. In summary, the proposed model can be used to evaluate the effect of structural design and process parameters on strip warpage and can provide strip design guidelines for reducing the amount of strip warpage and meeting the requirements for light, thin, and short chips on the production line. In addition, the proposed guidelines can accelerate the product development cycle and improve product quality with reduced development costs.

scholarly journals Design and Analysis of Advanced Nonoverlapping Winding Induction Machines for EV/HEV Applications

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6849
Author(s):  
Tayfun Gundogdu ◽  
Zi-Qiang Zhu ◽  
Jean-Claude Mipo
Keyword(s):  
Axial Length ◽  
Induction Machines ◽  
Considerable Effect ◽  
Design Guidelines ◽  
Design Parameters ◽  
Element Analysis ◽  
Analysis And Design ◽  
Time Stepping ◽  
Electromagnetic Performance ◽  
Flux Weakening

This paper presents a detailed analysis and design guidelines for advanced nonoverlapping winding induction machines (AIMs) with coil-pitch of two slot-pitches by considering some vital empirical rules and flux-weakening characteristics. The aim of the study is to develop a type of new winding and stator topology for induction machines (IMs) that will lead to a decrease in total axial length without sacrificing torque, power, and efficiency. The key performance characteristics of the improved AIMs are investigated by 2D time-stepping finite element analysis (FEA) and compared with those of IMs having fractional and conventional overlapping and nonoverlapping windings. Compared with the conventional overlapping winding counterpart of the AIM, a ~25% shorter axial length without sacrificing torque, output power, and efficiency is achieved. In addition, the influences of major design parameters, such as stator slot, rotor slot and pole numbers, stack length, number of turns per phase, machine geometric parameters, etc., on the flux-weakening characteristics are investigated. It has been concluded that the major design parameters have a considerable effect on the electromagnetic performance. However, among those parameters, the influences of pole number and stack length together with the number of turns on flux-weakening characteristics are significant.

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