Stress Analysis of Surface-Mount Interconnections Due to Vibrational Loading

1997 ◽  
Vol 119 (3) ◽  
pp. 183-188 ◽  
Author(s):  
K. Darbha ◽  
S. Ling ◽  
A. Dasgupta
Keyword(s):  
Finite Element ◽  
Solder Joint ◽  
Stress Analysis ◽  
Solder Joints ◽  
Test Time ◽  
Clear Understanding ◽  
Local Curvature ◽  
Surface Mount ◽  
Quantitative Models ◽  
Vibrational Loading

Recently, accelerated testing of surface mount interconnects under combined temperature and vibration environments has been recognized to be a necessary activity to ensure enhanced test-time compression. Successful use of vibration stresses requires a clear understanding of the correlation between vibrational damage and thermomechanical damage in surface mount solder joints. Hence, fatigue due to vibrational loading is important and accurate quantitative models are required to model effects due to vibrational fatigue. The proposed analysis in this paper contributes towards development of such quantitative models. This paper presents an approximate method to analyze stresses in surface mount solder joints subjected to vibration loading, using a generalized multidomain Rayleigh-Ritz approach (Ling and Dasgupta, 1995). The advantage of this approach is in its computational efficiency, compared to general-purpose finite element methods. Ling developed this approach in the context of thermomechanical stress analysis of solder joints. In this paper, the technique is modified and adapted for analyzing stresses caused by out-of-plane flexural dynamic modes of the printed wiring boards (PWBs). The analysis uses a two-step procedure where the local PWB curvatures are first estimated and the resulting deformations in the solder interconnect are then determined. The input boundary conditions for the first step are the bending moments in the PWB due to random vibrations. The stiffness of the interconnect assembly is then predicted using an energy method and curved-beam analysis. The bending moment and the computed stiffness of the interconnect assembly are then used to predict the local curvature of the PWB under any given surface-mount component by using an eigenfunction technique developed by Suhir (Suhir, 1988). In the second step of the analysis, the local curvature of the PWB is used as a boundary condition to predict the state of deformations, stresses, and strains in the solder joint using a modified version of the multidomain Rayleigh-Ritz approach. The overall method is applied to a specific example (J-lead solder joint) for illustrative purposes, and compared to finite element predictions for validation.

Estimating the Vibration Fatigue Life of Quad Leaded Surface Mount Components

1993 ◽  
Vol 115 (2) ◽  
pp. 195-200 ◽  
Author(s):  
D. B. Barker ◽  
Y. S. Chen ◽  
A. Dasgupta
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Solder Joint ◽  
Finite Element Modeling ◽  
Stress Analysis ◽  
Empirical Equation ◽  
Solder Joint Reliability ◽  
Surface Mount ◽  
Joint Reliability ◽  
Vibration Fatigue

This paper discusses the assumptions and details of the fatigue life calculations required to predict the fatigue life of quad leaded surface mount components operating in a vibration environment. A simple approximate stress analysis is presented that does not require complex finite element modeling, nor does it reduce the problem to a simple empirical equation or rule of thumb. The goal of the new method is to make PWB vibration solder joint reliability information available to the designer as early as possible and in an easily understood and implemented manner.

A Nonlinear Multi-Domain Thermomechanical Stress Analysis Method for Surface-Mount Solder Joints—Part II: Viscoplastic Analysis

1997 ◽  
Vol 119 (3) ◽  
pp. 177-182 ◽  
Author(s):  
S. Ling ◽  
A. Dasgupta
Keyword(s):  
Solder Joint ◽  
Potential Energy ◽  
Stress Analysis ◽  
Thermal Loading ◽  
Solder Joints ◽  
Stress And Strain ◽  
Thermomechanical Stress ◽  
Cyclic Thermal Loading ◽  
Surface Mount ◽  
Elastic Plastic

This is part II of a two-part paper presented by the authors for thermomechanical stress analysis of surface mount interconnects. A generalized multi-domain Rayleigh Ritz (MDRR) stress analysis technique has been developed to obtain the stress and strain fields in surface-mount solder joints under cyclic thermal loading conditions. The methodology was first proposed in Part I by the authors and results were presented for elastic-plastic loading (Ling et al., 1996). This paper extends the analysis for viscoplastic material properties. The solder joint domain is discretized selectively into colonies of nested sub-domains at locations where high stress concentrations are expected. Potential energy stored in the solder domain and in the attached lead and Printed Wiring Board (PWB) is calculated based on an assumed displacement field. Minimization of this potential energy provides a unique solution for the displacement field, consequently, stress and strain distribution. The MDRR technique was demonstrated to provide reasonable accuracy for elastic deformation (Ling and Dasgupta, 1995) and for time-independent elastic-plastic deformation (Ling and Dasgupta, 1996) for solder joints under cyclic thermal loading conditions. A piecewise linear incremental loading technique is used to solve the nonlinear elastic-plastic problem. The focus in the current paper is primarily on time-dependent viscoplastic deformation of the solder joints. Full field elastic, plastic, and viscoplastic analyses are performed, and the stress, strain hysteresis loops are obtained. Results are presented for a J-lead solder joint as an illustrative example.

Effect of intermetallic compound layer thickness on the shear strength of 1206 chip resistor solder joint

2015 ◽  
Vol 27 (1) ◽  
pp. 52-58 ◽  
Author(s):  
Peter K. Bernasko ◽  
Sabuj Mallik ◽  
G. Takyi
Keyword(s):  
Shear Strength ◽  
Intermetallic Compound ◽  
Solder Joint ◽  
Layer Thickness ◽  
Solder Joints ◽  
Ageing Time ◽  
Circuit Board ◽  
Intermetallic Compound Layer ◽  
Content Type ◽  
Surface Mount

Purpose – The purpose of this paper is to study the effect of intermetallic compound (IMC) layer thickness on the shear strength of surface-mount component 1206 chip resistor solder joints. Design/methodology/approach – To evaluate the shear strength and IMC thickness of the 1206 chip resistor solder joints, the test vehicles were conventionally reflowed for 480 seconds at a peak temperature of 240°C at different isothermal ageing times of 100, 200 and 300 hours. A cross-sectional study was conducted on the reflowed and aged 1206 chip resistor solder joints. The shear strength of the solder joints aged at 100, 200 and 300 hours was measured using a shear tester (Dage-4000PXY bond tester). Findings – It was found that the growth of IMC layer thickness increases as the ageing time increases at a constant temperature of 175°C, which resulted in a reduction of solder joint strength due to its brittle nature. It was also found that the shear strength of the reflowed 1206 chip resistor solder joint was higher than the aged joints. Moreover, it was revealed that the shear strength of the 1206 resistor solder joints aged at 100, 200 and 300 hours was influenced by the ageing reaction times. The results also indicate that an increase in ageing time and temperature does not have much influence on the formation and growth of Kirkendall voids. Research limitations/implications – A proper correlation between shear strength and fracture mode is required. Practical implications – The IMC thickness can be used to predict the shear strength of the component/printed circuit board pad solder joint. Originality/value – The shear strength of the 1206 chip resistor solder joint is a function of ageing time and temperature (°C). Therefore, it is vital to consider the shear strength of the surface-mount chip component in high-temperature electronics.

Predicting Thermal Fatigue Lifetimes for SMT Solder Joints

1992 ◽  
Vol 114 (4) ◽  
pp. 472-476 ◽  
Author(s):  
J. Sauber ◽  
J. Seyyedi
Keyword(s):  
Finite Element ◽  
Solder Joint ◽  
Thermal Cycling ◽  
Thermal Fatigue ◽  
Solder Joints ◽  
Finite Element Models ◽  
Creep Tests ◽  
Creep Equation ◽  
Joint Behavior ◽  
Creep Strains

A power-law type creep equation has been added to finite element models to calculate solder joint response to time, temperature, and stress level. The ability of the models to predict solder joint behavior was verified by running a series of creep tests. The models were then solved to determine the solder joint creep strains which occur during thermal cycling. These creep strains were used to predict the degradation of pull strength resulting from thermal cycling. More than 8,600 solder joints were thermally cycled and then individually pull tested to verify the accuracy of the method.

Solder Joint Formation in Surface Mount Technology—Part II: Design

1990 ◽  
Vol 112 (3) ◽  
pp. 219-222 ◽  
Author(s):  
S. M. Heinrich ◽  
N. J. Nigro ◽  
A. F. Elkouh ◽  
P. S. Lee
Keyword(s):  
Surface Tension ◽  
Solder Joint ◽  
Solder Joints ◽  
Cross Sectional Area ◽  
Surface Mount Technology ◽  
Sectional Area ◽  
Cross Sectional ◽  
Joint Formation ◽  
Surface Mount ◽  
Surface Tension Model

In this paper dimensionless design curves relating fillet height and length to joint cross-sectional area are presented for surface-mount solder joints. Based on an analytical surface tension model, the advantage of these dimensionless curves is that they may be used for arbitrary values of solder density and surface tension. The range of applicability of previously developed approximate formulae for predicting joint dimensions is also investigated. A simple example problem is included to illustrate the use of both the design curves and the approximate formulae.

A Nested Finite Element Methodology (NFEM) for Stress Analysis of Electronic Products—Part I: Theory and Formulation

2000 ◽  
Vol 123 (2) ◽  
pp. 141-146 ◽  
Author(s):  
Krishna Darbha ◽  
Abhijit Dasgupta
Keyword(s):  
Finite Element ◽  
Stress Analysis ◽  
Ritz Method ◽  
Element Analysis ◽  
Thermomechanical Stress ◽  
Surface Mount ◽  
Field Displacement ◽  
Analysis Technique ◽  
P Type ◽  
Finite Element Methodology

In this paper, the authors present a stress analysis technique based on a novel nested finite element methodology (NFEM). The NFEM is similar in concept to an earlier proposed multi-domain Rayleigh-Ritz methodology (Ling, S., 1997, “A Multi-Domain Rayleigh-Ritz Method for Thermomechanical Stress Analysis of Surface Mount Interconnects in Electronic Assemblies,” Ph.D. dissertation, Univ., of Maryland), that is based on a nested multi-field displacement assumption. The nested multi-field displacement technique may be viewed as a localized cascading of the p-type refinement in conventional finite element analysis. The concept and formulation of NFEM are presented in this paper while the application of NFEM to analyze the viscoplastic stress-state in two popular surface mount electronic interconnect styles is presented in Part II of this series. To illustrate the concept of NFEM, the formulation and results are provided for a one-dimensional viscoplastic example.

Viscoelastic Warpage Analysis of Surface Mount Package

2001 ◽  
Vol 123 (2) ◽  
pp. 101-104 ◽  
Author(s):  
Kiyoshi Miyake ◽  
Tsukasa Yoshida ◽  
Hyung Gil Baik ◽  
Sang Wook Park
Keyword(s):  
Finite Element ◽  
Solder Joint ◽  
Shear Modulus ◽  
Bulk Modulus ◽  
Shell Element ◽  
Critical Issue ◽  
Thickness Ratio ◽  
Surface Mount ◽  
Joint Connection ◽  
Saddle Shape

The reduction of the warpage of LSI package is a critical issue to ensure good solder joint connection in surface mount. In this study, different combinations of finite element and calculating methods were used to investigate the best method for predicting the thin small outline packages (TSOP) warpage. The results indicate that viscoelastic-GK calculation with relaxation of shear modulus and of bulk modulus using the multilayer shell element is the most appropriate method for predicting the warpage. All calculations confirm that a compound thickness ratio of 1.2 results in minimal warpage for a large chip TSOP. In this case, the warpage is reduced to near zero and the compound properties have little influence on warpage. However, for a small chip TSOP, a compound thickness ratio of 2.0–2.9 reduces the warpage. The warpage of small chip TSOP shows a severe saddle shape. The ratio and the magnitude of warpage depend on the compound properties. Also, the elastic method may result in a false simulation.

Thermomechanical Analysis of Solder Joints Under Thermal and Vibrational Loading

2001 ◽  
Vol 124 (1) ◽  
pp. 60-66 ◽  
Author(s):  
Cemal Basaran ◽  
Rumpa Chandaroy
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Solder Joint ◽  
Constitutive Model ◽  
Solder Joints ◽  
Cycle Fatigue ◽  
Simultaneous Application ◽  
Short Cycle ◽  
Finite Element Procedure ◽  
Life Predictions

Due to the coefficient of thermal expansion (CTE) mismatch between the bonded layers, the solder joint experiences cycling shear strain, which leads to short cycle fatigue. When semiconductor devices are used in a vibrating environment, additional strains shorten the fatigue life of a solder joint. Reliability of these joints in new packages is determined by laboratory tests. In order to use the FEM to replace these expensive reliability tests a unified constitutive model for Pb40/Sn60 solder joints has been developed and implemented in a thermo-viscoplastic-dynamic finite element procedure. The model incorporates thermal-elastic-viscoplastic and damage capabilities in a unified manner. The constitutive model has been verified extensively against laboratory test data. The finite element procedure was used for coupled thermo-viscoplastic-dynamic analyses for fatigue life predictions. The results indicate that using Miner’s rule to calculate accumulative damage by means of two separate analyses, namely dynamic and thermo-mechanical, significantly underestimates the accumulative total damage. It is also shown that a simultaneous application of thermal and dynamic loads significantly shortens the fatigue life of the solder joint. In the microelectronic packaging industry it is common practice to ignore the contribution of vibrations to short cycle fatigue life predictions. The results of this study indicate that damage induced in the solder joints by vibrations have to be included in fatigue life predictions to accurately estimate their reliability.

Solder Joint Reliability — Design Implications From Finite Element Modeling and Experimental Testing

1990 ◽  
Vol 112 (2) ◽  
pp. 135-146 ◽  
Author(s):  
H. K. Charles ◽  
G. V. Clatterbaugh
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Fatigue Life ◽  
Solder Joint ◽  
Solder Joints ◽  
Experimental Testing ◽  
Sectional Area ◽  
Stress Concentrations ◽  
Cross Sectional ◽  
Power Cycling

An extensive finite element modeling and experimental testing program has been carried out to determine the most optimum design parameters for solder joints in surface mount applications. Although the analysis and testing (power cycling and thermal cycling) has been carried out for a variety of package styles, particular attention will be paid to the result for leadless ceramic chip carriers. This package is particularly useful in certain high performance military and commercial applications. Analysis and experimentation indicate that increased fatigue life under power cycling can be attained by fabricating solder joints with large fillets and low standoff heights. The large fillet geometry significantly reduces harmful stress concentrations while increasing the net cross-sectional area within the joint. Both factors tend to improve the fracture toughness of the joint. The temperature and frequency dependencies of solder joint fatigue life under power cycling testing is discussed. The observed frequency dependence can be minimized by eliminating harmful tensile strain components thus reducing harmful stress relaxation and tensile induced oxygen embrittlement of grain boundaries. Temperature cycling studies indicate joints with slightly higher standoffs and low fillet angles are more resistant to cyclic fatigue than pillar type joints which tend to focus shear strains at the interfaces. Solder joints can be tapered to improve overall reliability but, in most cases, tapering will provide only a small increase in fracture toughness of the joint through the elimination of stress concentrations. Additional fatigue life increases can be obtained only through an enlargement of the joint cross-sectional area. Aspects of the above results will be presented in detail along with design guidelines for creating high reliability solder joints for various application scenarios.

Reliability Simulations for Solder Joints Using Stochastic Finite Element and Artificial Neural Network Models

1996 ◽  
Vol 118 (3) ◽  
pp. 148-156 ◽  
Author(s):  
G. Subbarayan ◽  
Y. Li ◽  
R. L. Mahajan
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Finite Element ◽  
Solder Joint ◽  
Six Sigma ◽  
Manufacturing Process ◽  
Solder Joints ◽  
Finite Element Models ◽  
Process Tolerance ◽  
Reliability Of Solder Joints

The field reliability of solder joints depends on the manufacturing process tolerance of design parameters and on the capability of manufacturing processes to achieve the tolerance. This process capability is usually expressed through measures such as “six-sigma.” In this paper, a systematic procedure to estimate the reliability of solder joints due to manufacturing process induced variations on the design is presented. The reliability is calculated using the stochastic finite element method and is most naturally expressed in terms of a mean life and a standard deviation in life. An integrated finite element solution procedure for predicting solder joint profile (during reflow) and life is also presented in the paper. A physico-neural approach in which the finite element models are used to build an artificial neural network model is next developed to combine the accuracy of the finite element models with the computational efficiency of neural networks. This physico-neural approach is shown to reduce the computational time required per design evaluation by four orders of magnitude without significant loss of accuracy. The developed procedures are applied to the 72 I/O OMPAC BGA package from Motorola, Inc. It is shown that a ±10 percent process tolerance on solder joint height, volume and pad sizes with a “six-sigma” process capability on these variables will result in solder joint with over ±20 percent variations in life about the mean life at ±6σ level. It is also shown that variations in life of BGA solder joints are most sensitive to variations in solder joint height. Variations in PWB pad size, solder volume, and substrate pad size are relatively less important, but in the order listed.

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