Plastic Ball Grid Array Assembly Research Articles

Optimal Design of Thermal Cycling Reliability for Plastic Ball Grid Array Assembly Via Finite Element Method and Taguchi Method

Abstract A finite element simulation analysis model was developed for a plastic ball grid array (PBGA) assembly to analyze its behavior under thermal cyclic loading conditions. The stress distribution in the SAC305 solder joints at different locations within the array was investigated by using ANAND constitutive equations. Subsequently, the thermal fatigue life of the key solder joints was quantified. The study also examined the influence of the solder joint diameter, substrate thickness, solder joint height, printed circuit board (PCB) thickness, and mold compound height on solder joint stress. Optimization of assembly parameters was achieved through the application of the Taguchi method. An extensive analysis was conducted using different assembly parameter combinations, employing the L9(34) orthogonal array design to explore the thermal cycling effects. The computed average Von Mises stress Δσ for the critical thin-layer elements of solder joints located in hazardous positions within the assembly was notably affected by variations in the solder joint height, substrate thickness, solder joint diameter, and mold compound height. This impact ranked in descending order of significance as solder joint height, substrate thickness, solder joint diameter, and mold compound height. The optimal parameter combination determined was a solder joint height of 0.70 mm, a solder joint diameter of 0.85 mm, a substrate thickness of 0.51 mm, and a mold compound height of 1.12 mm. Implementing this optimized configuration led to a significant 4.07% reduction in average stress Δσ for the critical thin-layer elements within hazardous solder joints. Moreover, the extension of the thermal fatigue life was notably improved, achieving an impressive 51.72% increase.

Vibration lifetime estimation of PBGA solder joints using Steinberg model

The work studies the vibration lifetime modeling of Sn37Pb soldered plastic ball grid array (PBGA) assemblies on the basis of vibration tests, finite element analysis (FEA) and Steinberg's empirical formulation. The test vehicles for the vibration tests consist of twelve PBGA components with built-in daisy-chained circuits, which are assembled on a printed circuit board (PCB) symmetrically. First, the natural frequencies of the test vehicle were determined by modal tests. The first three natural frequencies were obtained using FEA, which were compared with those from the modal test. Then, narrow-band sinusoid vibration tests were conducted at the first natural frequency of the test vehicle using constant-amplitude excitation, and the number of failure cycles was recorded by monitoring the overall electrical resistance. FEA was performed to obtain the stress of the critical solder joints under various levels of sinusoidal vibration loadings. To construct the stress versus failure cycles (SN) curve of the solder joints, the stresses of solder joints were used in conjunction with the lifetime obtained from the sinusoidal vibration tests. The random vibration test was conducted on the test vehicle to assess the lifetime of the solder joints subjected to broad-band excitation. Random vibration analyses were performed numerically to obtain the displacement responses of the PBGA assembly. Finally, a fatigue life prediction based on Steinberg's model was deduced from all these procedures. A comparison of the lifetime between the experimental results and the prediction suggests that the methodology is valid and practicable in predicting the vibration lifetime of PBGA solder joints.

Experimental Study on the Reliability of PBGA Electronic Packaging under Shock Loading

Plastic Ball Grid Array (PBGA) one of the most important electronic packaging methods, is widely used in aeronautical industry field. According to the JEDEC standard, shock tests of PBGA assemblies are conducted under different loading conditions. Several important parameters, such as the fatigue life of PBGA assemblies, the relationship between solder joint positions and fatigue life, the relationship between strain energy density and fatigue life, are analyzed based on experiment results. The failure modes of PBGA assemblies are studied by optical microscope (OM). The results show that during the shock tests, the strains of the solder joints near the center of the specimen are larger than other positions, and these solder joints are prone to form micro cracks. With the increase of the shock times, these micro cracks extend rapidly which will eventually cause the failure of the PBGA electronic packaging.

Microelectronics packaging technology roadmaps, assembly reliability, and prognostics

This paper reviews the industry roadmaps on commercial-off-the shelf (COTS) microelectronics packaging technologies covering the current trends toward further reducing size and increasing functionality. Due to the breadth of work being performed in this field, this paper presents only a number of key packaging technologies. The topics for each category were down-selected by reviewing reports of industry roadmaps including the International Technology Roadmap for Semiconductor (ITRS) and by surveying publications of the International Electronics Manufacturing Initiative (iNEMI) and the roadmap of association connecting electronics industry (IPC). The paper also summarizes the findings of numerous articles and websites that allotted to the emerging and trends in microelectronics packaging technologies. A brief discussion was presented on packaging hierarchy from die to package and to system levels. Key elements of reliability for packaging assemblies were presented followed by reliabilty definition from a probablistic failure perspective. An example was present for showing conventional reliability approach using Monte Carlo simulation results for a number of plastic ball grid array (PBGA). The simulation results were compared to experimental thermal cycle test data. Prognostic health monitoring (PHM) methods, a growing field for microelectronics packaging technologies, were briefly discussed. The artificial neural network (ANN), a data-driven PHM, was discussed in details. Finally, it presented inter- and extra-polations using ANN simulation for thermal cycle test data of PBGA and ceramic BGA (CBGA) assemblies.

Study on Board-Level Drop Impact Reliability of Sn–Ag–Cu Solder Joint by Considering Strain Rate Dependent Properties of Solder

Board-level drop reliability test and analysis require dynamic characterization of the high strain-rate properties of the solder, along with solder joint failure tests. Relying on just the drop impact analysis of board-level dynamic response (i.e. G-levels and board bending strains) and an oversimplification of deformation response of solder joints (i.e., assuming elastic stress criteria) can lead to misleading conclusions in the physics-of-failure understanding in drop impact tests. In this paper, impact tests were conducted with a split Hopkinson pressure bar test system to study the dynamic response of bulk solder materials. A finite-element analysis of drop impact was conducted by considering different solder constitutive models such as the elastic and strain rate-dependent plastic model to investigate the effect of the solder constitutive model on the dynamic response of the solder joint. The important finding of this study is that the constitutive model used has a major impact on the dynamic response of solder joint stress and strain results. Theoretically, it is predicted that the strain rate-dependent plastic model gave better correlation results than the simple elastic model. A solder joint reliability characterization using the drop impact test with a clamped–clamped boundary condition was investigated for a plastic ball grid array assembly with Sn–Ag–Cu solder and two board surface finishes. In order to assess drop reliability of solder joint with different surface finishes, Charpy test was conducted to evaluate the dynamic strength of the soldered specimen using Sn–Ag–Cu solder and with or without Ni/Au plating.

Comparison approach on strain behavior of PBGA assembly by considering different thermal‐mechanical compound loading modes

PurposeThe purpose of this paper is to provide a systematic method to perform analysis and test for vibration‐thermal strain behavior of plastic ball grid array (PBGA) assembly by considering thermal and vibration loading mode. Also to investigate the dynamic behavior of PBGA assembly by considering loading modes for design and reliability evaluation of PBGA packaging.Design/methodology/approachA PBGA assembly prototype with different structure and material parameters is designed and manufactured. Based on investigation of the structural and physical parameters of PBGA sample, the vibration‐thermal strain test is developed to measure the strain distribution at the surface of the BT (bismaleimide triazine) substrates and PCB (printed circuit board) surface under vibration‐thermal cycling loading such as random vibration and the temperature is changed from 0°C to 100°C.FindingsThe test results show that the loading modes have different impact on PCB, EMC and substrate, respectively. In the meantime, it is shown that the characteristics of the compound mode is not the linear accumulative result by single vibration mode and single thermal loading mode as forecasted. The nonlinear mechanism for these modes application is the future work for progress.Research limitations/implicationsIt is very difficult to set up a numerical approach to illustrate the validity of the testing approach because the complex loading modes and the complex structure of PBGA assembly. The research on an accurate mathematical model of the PBGA assembly prototype is a future work.Practical implicationsIt implies a potential design characteristic for future application of PBGA assembly. It also builds a basis for future work for design and reliability evaluation of BGA package.Originality/valueThis paper fulfils useful information about the thermal‐vibration coupling dynamic behavior of PBGA assembly with different structure characteristics, materials parameters.

Testing on dynamic behavior of PBGA assembly by considering fixed‐modes

PurposeThe purpose of this paper is to develop a systematic experimental investigation for testing dynamic behavior of plastic ball grid array (PBGA) integrity in electronic packaging and to investigate the dynamic behavior of PBGA assembly by considering fixed‐modes for design and reliability evaluation of PBGA packaging.Design/methodology/approachA PBGA assembly prototype with different structure and material parameters is designed and manufactured. The modal distribution under excitation cycling can be tested by hammering test. The dynamic test about the PBGA assembly prototype can be implemented with different structure characteristics, materials parameters and fixed‐modes. To illustrate the validity of experimental test, the numerical simulation for the dynamic behavior of the PBGA assembly prototype is developed by using finite element method. Comparison between the experimental results and simulation can illustrate the validity of the experimental test and finite element modeling each other.FindingsThe modal distribution test shows the influence of structure characteristics, materials parameters and fixed‐modes of PBGA assembly board. The changing trends of the dynamic modal characteristics during the dynamic excitation can be obtained with different structure characteristics, materials parameters and fixed‐modes of PBGA assembly. Test shows that the fixed location of the assembly board is the most important factor to influence the first frequency and modal deformation of the assembly board. Higher frequency and smaller deformation can be obtained when there are more constraints in printed circuit board.Research limitations/implicationsThe numerical model is a compendious model by predigesting structure. The research on more accurate mathematical model of the PBGA assembly prototype is a future work.Practical implicationsIt can imply the dynamics of PBGA assembly. It builds a basis for future work for design and reliability evaluation of PBGA packaging.Originality/valueThis paper provides useful information about the dynamic behavior of PBGA assembly with different structure characteristics, materials parameters and fixed‐modes.

Testing approach on dynamic fatigue property of PBGA assembly under determinate vibration excitation

To investigate the reliability property of Plastic Ball Grid Array (PBGA) under determinate vibration, a specified PBGA assembly that contains different structural and material parameters was designed. The fatigue property of PBGA assembly under determinate vibration was tested. Manson?Coffin empirically derived formula and rain-flow algorithm were utilised to achieve the fatigue life of solder joints. Some key parameters that can influence the property of the PBGA assembly were analysed in detail.

Experimental Approach and Evaluation on Dynamic Reliability of PBGA Assembly

The aim of this paper is to provide a systematic method to perform experimental test and theoretical evaluation on fatigue characteristics of plastic-ball-grid-array (PBGA) assembly under random vibration. A specified PBGA assembly which contains different structural and material parameters was manufactured. The fatigue characteristics of PBGA assembly under random vibration were tested. Manson-Coffin empirically derived formula and rain-flow algorithm were used to achieve the fatigue life of solder joints. In the meantime, the failure curve (reliability-cycle number curve) can be obtained by using Weibull distribution method when PBGA assembly is on different working situation. Finally, life prediction of corner solder balls was deduced based on three-band technology and cumulative damage index. Test results lay a basis for high-reliability design of PBGA assembly for engineering application.

Correlation Between Measurement and Simulation of Thermal Warpage in PBGA With Consideration of Molding Compound Residual Strain

The objective of this study is to experimentally and numerically investigate thermal and residual deformation of plastic ball grid array (PBGA) package and assembly. Shadow moire was used to measure their real-time out-of-plane deformations (warpages) during heating and cooling conditions. A finite element model with material properties characterized by dynamic mechanical analyzer and thermomechanical analyzer was established to simulate the thermally-induced deformations of test specimens for understanding mechanics. The full-field warpages of the PBGA package and assembly were measured during the temperature cycling. The results show that a maximum warpage with a concave (smiling) shape in both package and assembly occurred at the neighborhood of 155degC during the thermal cycling, rather than with a convex (crying) shape at room temperature by assuming the warpage-free (or stress-free) temperature is at 175degC of molding. This issue has been resolved through the finite element analyses by cooperating into the residual strain (stress) in the epoxy molding compound (EMC) of the package, which is obtained by measuring the residual and thermal deformations of the detached EMC/die bi-material structure. This residual strain of the EMC maybe comes either from the chemical shrinkage of the EMC curing, or possible from stress relaxation of the EMC during the first solder reflow of attaching the solder balls. Furthermore, the consistency of thermal deformations for both the package and assembly obtained from the finite element models indicates that the maximum warpage occurs at the corner of the substrate at near 155degC, rather than at the room temperature, due to the glass transition temperature (Tg) and residual strains of the EMC. This maximum warpage can be mitigated by lowering the residual shrinkage strain. And the warpage of the PBGA assembly coincides with the package at the temperature beyond 155degC (highly resulting from apparent creep of the solder balls), but is larger than that of the package below 155degC, due to constraint of the printed circuit board through less-pronounced creep solder balls.

Thermal Cycle Reliability and Failure Mechanisms of CCGA and PBGA Assemblies With and Without Corner Staking

Area array packages (AAPs) with 1.27 mm pitch have been the packages of choice for commercial applications; they are now starting to be implemented for use in military and aerospace applications. Thermal cycling characteristics of plastic ball grid array (PBGA) and chip scale package assemblies, because of their wide usage for commercial applications, have been extensively reported on in literature. Thermal cycling represents the on-off environmental condition for most electronic products and therefore is a key factor that defines reliability. However, very limited data is available for thermal cycling behavior of ceramic packages commonly used for the aerospace applications. For high reliability applications, numerous AAPs are available with an identical design pattern both in ceramic and plastic packages. This paper compares assembly reliability of ceramic and plastic packages with the identical inputs/outputs (I/Os) and pattern. The ceramic package was in the form of ceramic column grid array (CCGA) with 560 I/Os peripheral array with the identical pad design as its plastic counterpart. The effects of the following key parameters on reliability of both CCGA and PBGA assemblies were investigated:(1) thermal cycle ranges, -50degC/75degC, -55degC/100degC, and -55degC/125degC; (2) corner staking on failure mechanisms for two thermal cycle profiles, -55degC/125degC and -50degC/75degC; (3) package interchangeability, i.e., using PBGA package on CCGA pad design with a larger pad. Packages were assembled on polyimide boards and their daisy chains were continuously monitored. Optical photomicrographs were taken at various thermal cycle intervals to document damage progress and behavior. Representative samples along with their cross-sectional photomicrographs at higher magnification, taken by scanning electron microscopy and analyzed by energy dispersive X-ray, are also presented. The inspection documents were used to determine crack propagation and failure analyses for packages with and without corner staking. In assemblies with corner staking adhesive, a transition in failure from corner columns to center columns was observed when maximum temperature in thermal cycling profiles changed. This is a new failure mechanism not reported on in literature. Finite element analysis (FEA) was used to predict such global failure mode changes. FEA findings are also presented.

Numerical investigation on dynamic characteristics of BGA structural integrity by using finite element method

A specified plastic ball grid array (PBGA) structural integrity prototype which contains different structure and material parameters is designed and manufactured. Based on investigation of the structural and dynamic parameters of PBGA prototype, the numerical simulation of the dynamic characteristics of the PBGA assembly prototype is analysed by using finite element method. The results show that the changing trends of the dynamic modal characteristics during the dynamic excitation. It builds a basis for future work such as the experimental test, structural design and reliability evaluation of PBGA packaging.

Reliability of BGA and CSP on Metal-Backed Printed Circuit Boards in Harsh Environments

Increased use of sensors and controls in automotive applications has resulted in significant emphasis on the deployment of electronics directly mounted on the engine and transmission. Increased shock, vibration, and higher temperatures necessitate the fundamental understanding of damage mechanisms, which will be active in these environments. Electronics typical of office benign environments uses FR-4 printed circuit boards (PCBs). Automotive applications typically use high glass-transition temperature laminates such as FR4-06 glass∕epoxy laminate material (Tg=164.9°C). In application environments, metal backing of printed circuit boards is being targeted for thermal dissipation, mechanical stability, and interconnections reliability. In this study, the effect of metal-backed boards on the interconnect reliability has been evaluated. Previous studies on electronic reliability for automotive environments have addressed the damage mechanics of solder joints in plastic ball-grid arrays on non-metal-backed substrates (Lall et al., 2003, “Model for BGA and CSP in Automotive Underhood Environments,” Electronic Components and Technology Conference, New Orleans, LA, May 27–30, pp. 189–196;Syed, A. R., 1996, “Thermal Fatigue Reliability Enhancement of Plastic Ball Grid Array (PBGA) Packages,” Proceedings of the 1996 Electronic Components and Technology Conference, Orlando, FL, May 28–31, pp. 1211–1216;Evans et al., 1997, “PBGA Reliability for Under-the-Hood Automotive Applications,” Proceedings of InterPACK ’97, Kohala, HI, Jun. 15–19, pp. 215–219;Mawer et al., 1999, “Board-Level Characterization of 1.0 and 1.27mm Pitch PBGA for Automotive Under-Hood Applications,” Proceedings of the 1999 Electronic Components and Technology Conference, San Diego, CA, Jun. 1–4, pp. 118–124) and ceramic ball-grid arrays (BGAs) on non-metal-backed substrates (Darveaux, R., and Banerji, K., 1992, “Constitutive Relations for Tin-Based Solder Joints,” IEEE Trans-CPMT-A, Vol. 15, No. 6, pp. 1013–1024;Darveaux et al., 1995, “Reliability of Plastic Ball Grid Array Assembly,” Ball Grid Array Technology, Lau, J., ed., McGraw-Hill, New York, pp. 379–442;Darveaux, R., 2000, “Effect of Simulation Methodology on Solder Joint Crack Growth Correlation,” Proceedings of 50th ECTC, May, pp. 1048–1058). Delamination of PCBs from metal backing has also been investigated. The test vehicle is a metal-backed FR4-06 laminate. The printed circuit board has an aluminum metal backing, attached with pressure sensitive adhesive (PSA). Component architectures tested include plastic ball-grid array devices, C2BGA devices, QFN, and discrete resistors. Reliability of the component architectures has been evaluated for HASL. Crack propagation and intermetallic thickness data have been acquired as a function of cycle count. Reliability data have been acquired on all these architectures. Material constitutive behavior of PSA has been measured using uniaxial test samples. The measured constitutive behavior has been incorporated into nonlinear finite element simulations. Predictive models have been developed for the dominant failure mechanisms for all the component architectures tested.

Mechanical bend fatigue reliability of lead-free and halogen-free PBGA assemblies

In order to comply with impending legislative regulations in Europe (WEEE) and Japan and meet market demand for environmentally friendly products, electronics manufacturers are beginning to introduce lead-free solder and halogen-free PCBs into their products. The change of materials impacts the entire manufacturing supply chain, from component and solder-material suppliers to assembly equipment vendors. The manufacturability and reliability of several alternative lead-free alloys have examined in the literature. A majority of US based companies, working with NEMI, are selecting SnAgCu alloys, with minor compositional variations. However, much work is still required in the area of component and assembly reliability, especially in mechanical fatigue and impact loading, where the failure drivers are independent of the coefficient of thermal expansion. In this paper, the mechanical bend fatigue reliability of plastic ball grid array (PBGA) assemblies is investigated. Reliability of traditional PBGA assemblies is compared to those built with environmentally friendly materials. Experimental data is presented for four different combinations of tin-lead and lead-free solders as well as FR4 and Halogen-Free laminate substrates-TL/FR4, LF/FR4, TL/HF, and LF/HF. The fatigue life was correlated to the different failure modes. A transition in failure modes as a function of the applied load was observed. A three-dimensional parametric finite element model was developed to correlate the local PCB strains and solder joint plastic strains with the fatigue life of the assembly.

Model for BGA and CSP Reliability in Automotive Underhood Applications

Fine-pitch ball grid array (BGA) and underfills have been used in benign office environments and wireless applications for a number of years, however their reliability in automotive underhood environment is not well understood. In this work, the reliability of fine-pitch plastic ball grid array (PBGA) packages has been evaluated in the automotive underhood environment. Experimental studies indicate that the coefficient of thermal expansion (CTE) as measured by thermomechanical analyzer (TMA) typically starts to change at 10-15/spl deg/C lower temperature than the T/sub g/ specified by differential scanning calorimetry (DSC) potentially extending the change in CTE well into the accelerated test envelope in the neighborhood of 125/spl deg/C. High T/sub g/ substrates with glass-transition temperatures much higher than the 125/spl deg/C high temperature limit, are therefore not subject to the effect of high coefficient of thermal expansion close to the high temperature of the accelerated test. Darveaux's damage relationships were derived on ceramic ball grid array (CBGA) assemblies, with predominantly solder mask defined (SMD) pads and 62Sn36Pb2Ag solder. In addition to significant differences in the crack propagation paths for the two pad constructions, SMD pads fail significantly faster than the non solder mask defined (NSMD) pads in thermal fatigue. The thermal mismatch on CBGAs is much larger than PBGA assemblies. Crack propagation in CBGAs is often observed predominantly on the package side as opposed to both package and board side for PBGAs. In the present study, crack propagation data has been acquired on assemblies with 15, 17, and 23mm size plastic BGAs with NSMD pads and 63Sn37Pb on high-T/sub g/ printed circuit boards. The data has been benchmarked against Darveaux's data on CBGA assemblies. Experimental matrix also encompasses the effect of bis-maleimide triazine (BT) substrate thickness on reliability. Damage constants have been developed and compared against existing Darveaux Constants. Prediction error has been quantified for both sets of constants.

Simplification of Finite Element Models for Thermal Fatigue Life Prediction of PBGA Packages

The use of PBGA (plastic ball grid array) electronic packages has been greatly increased in the last decade due to high I/O densities offered. The fatigue life prediction for them is a relatively new task in the electronic field. PBGA packages have more complex geometry than conventional SMT (surface mount technology) packages, such as Leaded and Leadless Chip Carriers (LDCC and LLCC), in which the I/O pins are distributed along the perimeters of chip carriers and their geometries are suitable for two-dimensional (2-D) finite element (FE) simulation. This choice is not so clear in PBGAs. In this study, sectional 2-D, sliced three-dimensional (3-D), and 1/8th 3-D FE models for PBGA assemblies are compared to determine the appropriate FE models that are able to save computational time and memory while maintaining reasonable calculation accuracy. The comparisons and merits of each modeling approach are discussed. An energy-based method is used to predict the fatigue life for solder joints in PBGAs. The fatigue coefficients in the correlation equation, which were obtained previously from the analysis of traditional SMT packages, are updated for more accurate prediction. New fatigue coefficients are obtained for different modeling approaches.

Assessment of board level solder joint reliability for PBGA assemblies with lead‐free solders

Evaluates the board level reliability of plastic ball grid array (PBGA) assemblies under thermal and mechanical loading, with the objective of characterizing the reliability of lead‐free solder joints for various assembly conditions. A five‐leg experiment was designed which included various combinations of solder materials and peak reflow temperatures. It was found that the lead‐free solder joints have a much longer thermal fatigue life than the 63Sn–37Pb solder. The 63Sn–37Pb solder joints seem to perform slightly better than the lead‐free solder under mechanical loading.

Finite-element analysis of a PBGA assembly under isothermal/mechanical twisting loading

In order to reduce the reliability testing time for new electronic products, a new highly accelerated mechanical-thermal (HAMT) test system has been developed. In this system, a cyclic out-of-plane deformation is imposed on a printed circuit board (PCB) assembly by twisting the PCB mechanically inside a thermal chamber. The combined effects of the mechanical deformation and the coefficient of thermal expansion (CTE) mismatch of different materials accelerate the failure of solder joints, so as to reduce the reliability testing time of the PCB assembly. To verify the test method, HAMT tests of plastic ball grid array (PBGA) assemblies were carried out in an isothermal environment. Finite-element (FE) simulations were conducted to predict the reliability of the PBGA assemblies under the isothermal/mechanical twisting (ITMT) loading condition. In this paper, the simulation results are presented. The failure locations in the PBGA solder joints under the ITMT loading condition are investigated, and the fatigue life of the interconnections is predicted using Darveaux's crack initiation and growth model. The simulation results exhibit a good correlation with the test results.

Quick assessment methodology for reliability of solder joints in ball grid array (BGA) assembly—Part II: Reliability experiment and numerical simulation

In the present study, a facility, i.e., a mechanical deflection system (MDS), was established and applied to assess the long-term reliability of the solder joints in plastic ball grid array (BGA) assembly. It was found that the MDS not only quickly assesses the long-term reliability of solder joints within days, but can also mimic similar failure mechanisms in accelerated thermal cycling (ATC) tests. Based on the MDS and ATC reliability experiments, the acceleration factors (AF) were obtained for different reliability testing conditions. Furthermore, by using the creep constitutive relation and fatigue life model developed in part I, a numerical approach was established for the purpose of virtual life prediction of solder joints. The simulation results were found to be in good agreement with the test results from the MDS. As a result, a new reliability assessment methodology was established as an alternative to ATC for the evaluation of long-term reliability of plastic BGA assembly.

Reliability Modeling for Ball Grid Array Assembly With a Large Number of Warpage Affected Solder Joints

A reliability model is established to study thermal fatigue behavior of solder joints in plastic ball grid array (PBGA) assemblies. The model is able to simulate a configuration with a large number of warpage affected solder joints. For efficient computation, regression models are used to calculate the force acting on each solder joint to determine its height under different warpage conditions. With the height and specified solder parameters, the shapes of selected solder joints are calculated using the Surface Evolver. In addition, the displacements of these solder joints can be determined by a macro model using equivalent beams to represent hundreds of solder joints. With the shapes and displacements, three-dimensional micro models for the selected joints are established to compute strain energy densities during temperature cycling. The energy densities can be used to estimate fatigue lives through an empirical correlation. Two PBGA assemblies with 72-I/O cavity-up and 540-I/O cavity-down packages are studied using the reliability model. Silicon chip size and substrate thickness are critical to solder fatigue in the cavity-up assembly. Their effects are reduced substantially for the cavity-down assembly, which is more reliable due to small global thermal mismatch. However, its reliability is strongly affected by the warpage. The warpage changes the shapes of solder joints and can reduce the corner joint’s fatigue life from 20,000 to 7800 temperature cycles for an arch-type warpage of 0.28 mm across a 42.5 mm×42.5 mm region.