Improved Analytical and Semi-Analytical Durability Models (Constrained Models) for Various Surface-Mount Configurations

2002 ◽  
Author(s):  
Pradeep Sharma ◽  
James Loman
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Solder Joint ◽  
Thermal Cycling ◽  
Deformation Process ◽  
Analytical Models ◽  
Surface Mount ◽  
Constrained Models ◽  
Constraint Approach ◽  
Finite Element Calibration

Several analytical and semi-analytical models to predict solder joint durability under thermal cycling loadings have been proposed. In general, these models are overtly conservative often requiring extensive experimental and/or finite element calibration. We present, based on the physics of the deformation process, a direct approach to improve these classes of model by resolving one of the major causes of conservatism. Our contribution is applicable to virtually all known surface mount configurations. The improved models (henceforth termed as constraint models) retain the simplicity of use of the existing ones. The efficacy of constraint approach is demonstrated on leadless resistors and comparisons are made with existing models and experimental data.

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.

FEA Based Reliability Predictions for PBGA Packages Subjected to Isothermal Aging Prior to Thermal Cycling

2015 ◽  
Author(s):  
Munshi Basit ◽  
Mohammad Motalab ◽  
Jeffrey C. Suhling ◽  
John L. Evans ◽  
Pradeep Lall
Keyword(s):  
Finite Element ◽  
Solder Joint ◽  
Thermal Cycling ◽  
Isothermal Aging ◽  
Material Behavior ◽  
Lead Free ◽  
Stress Strain ◽  
Solder Material ◽  
Free Solder ◽  
Temperature Aging

The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. In our prior work on aging effects, we have demonstrated that the observed material behavior degradations of Sn-Ag-Cu (SAC) lead free solders during room temperature aging (25 C) and elevated temperature aging (50, 75, 100, 125, and 150 C) were unexpectedly large. The measured stress-strain data demonstrated large reductions in stiffness, yield stress, ultimate strength, and strain to failure (up to 50%) during the first 6 months after reflow solidification. In this study, we have used both accelerated life testing and finite element modeling to explore how prior isothermal aging affects the overall reliability of PBGA packages subjected to thermal cycling. In the experimental work, an extensive test matrix of thermal cycling reliability testing has been performed using a test vehicle incorporating several sizes (5, 10, 15, 19 mm) of BGA daisy chain components with 0.4 and 0.8 mm solder joint pitches (SAC305). PCB test boards with 3 different surface finishes (ImAg, ENIG and ENEPIG) were utilized. In this paper, we concentrate on the reporting the results for a PBGA component with 15 mm body size. Before thermal cycling began, the assembled test boards were divided up into test groups that were subjected to several sets of aging conditions (preconditioning) including 0, 6, and 12 months aging at T = 125 °C. After aging, the assemblies were subjected to thermal cycling (−40 to +125 °C) until failure occurred. The Weibull data failure plots have demonstrated that the thermal cycling reliabilities of pre-aged assemblies were significantly less than those of non-aged assemblies. A three-dimensional finite element model of the tested 15 mm PBGA packages was also developed. The cross-sectional details of the solder ball and the internal structure of the BGA were examined by scanning electron microscopy (SEM) to capture the real geometry of the package. Simulations of thermal cycling from −40 to 125 C were performed. To include the effects of aging in the calculations, we have used a revised set of Anand viscoplastic stress-strain relations for the SAC305 Pb-free solder material that includes material parameters that evolve with the thermal history of the solder material. The accumulated plastic work (energy density dissipation) was used is the failure variable; and the Darveaux approach to predict crack initiation and crack growth was applied with aging dependent parameters to estimate the fatigue lives of the studied packages. We have obtained good correlation between our new reliability modeling procedure that includes aging and the measured solder joint reliability data. As expected from our prior studies on degradation of SAC material properties with aging, the reliability reductions were more severe for higher aging temperature and longer aging times.

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.

Thermal Stress Analysis of SMT PQFP Packages and Interconnections

1989 ◽  
Vol 111 (1) ◽  
pp. 2-8 ◽  
Author(s):  
J. H. Lau
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Thermal Stress ◽  
Solder Joint ◽  
Thermal Cycling ◽  
Mechanical Behavior ◽  
Thermal Stresses ◽  
Stress And Strain ◽  
Plastic Analysis ◽  
Chip Carrier

An elasto-plastic analysis of the thermal stresses and strains in a surface mounted plastic-quad-flat-pack (PQFP) assembly by using a 3-D finite element method is presented in this paper. Detailed stress and strain distributions and whole-field displacements of the assembly are also provided for a better understanding of its mechanical behavior during thermal cycling. It was found that the stresses and strains in the PQFP solder joint are smaller than those in the plastic-leaded-chip-carrier (PLCC) solder joint. The results presented herein should be useful in the design for reliability of this class of surface mount assemblies.

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.

Thermal Cycling Reliability Predictions for PBGA Assemblies That Include Aging Effects

2013 ◽  
Author(s):  
Mohammad Motalab ◽  
Muhannad Mustafa ◽  
Jeffrey C. Suhling ◽  
Jiawei Zhang ◽  
John Evans ◽  
...  
Keyword(s):  
Finite Element ◽  
Solder Joint ◽  
Thermal Cycling ◽  
Failure Criteria ◽  
Lead Free ◽  
Aging Effects ◽  
Solder Joint Reliability ◽  
Reliability Models ◽  
Joint Reliability ◽  
Free Solder

The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. Traditional finite element based predictions for solder joint reliability during thermal cycling accelerated life testing are based on solder constitutive equations (e.g. Anand viscoplastic model) and failure models (e.g. energy dissipation per cycle model) that do not evolve with material aging. Thus, there will be significant errors in the calculations with lead free SAC alloys that illustrate dramatic aging phenomena. In this research, we have developed a new reliability prediction procedure that utilizes constitutive relations and failure criteria that incorporate aging effects, and then validated the new approach through correlation with thermal cycling accelerated life testing experimental data. As a part of this work, a revised set off Anand viscoplastic stress-strain relations for solder have been developed that included material parameters that evolve with the thermal history of the solder material. The effects of aging on the nine Anand model parameters have been determined as a function of aging temperature and aging time, and the revised Anand constitutive equations with evolving material parameters have been implemented in commercial finite element codes. In addition, new aging aware failure criteria have been developed based on fatigue data for lead free solder uniaxial specimens that were aged at elevated temperature for various durations prior to mechanical cycling. Using the measured fatigue data, mathematical expressions have been developed for the evolution of the solder fatigue failure criterion constants with aging, both for Coffin-Manson (strain-based) and Morrow-Darveaux (dissipated energy based) type fatigue criteria. Similar to the findings for mechanical/constitutive behavior, our results show that the failure data and associated fatigue models for solder joints are affected significantly by isothermal aging prior to cycling. After development of the tools needed to include aging effects in solder joint reliability models, we have then applied these approaches to predict reliability of PBGA components attached to FR-4 printed circuit boards that were subjected to thermal cycling. Finite element modeling was performed to predict the stress-strain histories during thermal cycling of both non-aged and aged PBGA assemblies, where the aging at constant temperature occurred before the assemblies were subjected to thermal cycling. The results from the finite element calculations were then combined with the aging aware fatigue models to estimate the reliability (cycles to failure) for the aged and non-aged assemblies. As expected, the predictions show significant degradations in the solder joint life for assemblies that had been pre-aged before thermal cycling. To validate our new reliability models, an extensive test matrix of thermal cycling reliability testing has been performed using a test vehicle incorporating several sizes of fine pitch PBGA daisy chain components. Before thermal cycling began, the assembled test boards were divided up into test groups that were subjected to several sets of aging conditions (preconditioning) including different aging temperatures (T = 25, 55, 85 and 125 C) and different aging times (no aging, and 6 and 12 months). After aging, the assemblies were subjected to thermal cycling (−40 to +125 C) until failure occurred. As with the finite element predictions, the Weibull data failure plots have demonstrated that the thermal cycling reliabilities of pre-aged assemblies were significantly less than those of non-aged assemblies. Good correlation was obtained between our new reliability modeling procedure that includes aging and the measured solder joint reliability data.

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.

Surface Mount Technology (SMT) Substrate Material Requirements - A Brief Review

1987 ◽  
Vol 108 ◽  
Author(s):  
A. Mahammad Ibrahim
Keyword(s):  
Dielectric Constant ◽  
Solder Joint ◽  
Thermal Cycling ◽  
Substrate Material ◽  
Surface Mount Technology ◽  
Solder Joint Reliability ◽  
Surface Mount ◽  
Printed Circuit ◽  
Joint Reliability ◽  
Out Of Plane

ABSTRACTThe state of the art for the printed circuit (pc) industry is the Surface Mount Technology (SMT) using leadless ceramic chip carriers (LCCCs). The SMT technique is used to design, fabricate, and assemble affordable high-speed, high-density electronic modules with reduced size and weight. However, to take full advantage of the SMT, new high-performance printed circuit board (PCB) substrate materials must be developed, especially if the goal is to satisfy the high reliability required in military applications. The most critical requirement is matching the in-plane coefficient of thermal expansion (CTE) with the SMT-PCB's and the chip carriers (LCCCs) to reduce the solderjoint stresses during thermal cycling. Solder-joint reliability can be improved significantly by tailoring the in-plane CTE to approximately 6–7 ppm/°C (of the alumina chip carrier) using Kevlar and/or quartz fabric-reinforced polymer composites, instead of conventional glass composites. Less attention has been focussed on other important requirements, e.g., out-of-plane (Z-axis) expansion, glass transition temperature (Tg), dielectric constant, and resin microcracking, which also play important roles in the overall performance of the substrate materials. For example, high Z-expansion puts additional strain on the plated through holes (PTH), thereby affecting PTR reliability. A low Tg significantly increases the amount of thermal stress imposed during thermal cycling on solder joints and PTH, and leads to failures. This paper contains a brief review of the requirements of a SMT-PCB substrate material, including such critical parameters as: in-plane CTE, out-of-plane CTE, Tg, dielectric constant, fiber-to-resin ratio, and resin microcracking, and their effects on solder joint reliability, PTH reliability, dimensional stability, and electrical performance.

Sign in / Sign up

Export Citation Format

Share Document