Solder Joint Life Research Articles

Investigation on improving soldering reliability of large-scale LCCC devices with high-lead solder ball materials

Abstract Leadless Ceramic Chip Carrier (LCCC) is commonly used in high-density electronic packaging PCB boards. Due to the different thermal expansion of materials, the solder joints of LCCC devices are prone to stress and cracking after assembly, which leads to the failure of LCCC devices’ electrical performance. In this paper, the advantages and disadvantages of four solutions were analysed, and comprehensively considered the use of ball planting to alleviate thermal mismatch stress. After experimental verification, the thermal mismatch between the LCCC devices and PCB results in a lifespan of less than 200 cycles for direct assembly of the LCCC devices. Planting balls at the bottom of LCCC devices and soldering can effectively increase the lifespan of solder joints and improve product reliability. By analysing the SMT process, the bottom high-lead ball placement of LCCC devices was implemented, and environmental testing was conducted using temperature shock testing to demonstrate that bottom ball placement can extend solder joint life and improve reliability. This study provides a reliable soldering method for large-scale LCCC devices and provides a basis for improving LCCC reliability.

Investigation of the Impacts of Solder Alloy Composition and Temperature Profile on Fatigue Life of Ball Grid Array Solder Joints Under Accelerated Thermal Cycling

Abstract This study investigated the thermal fatigue reliability of ball grid array (BGA) solder joints under accelerated thermal cycling, considering the impacts of solder alloy and temperature profile. Applying the Darveaux solder joint reliability assessment, simulations consider lead-based (63Sn37Pb and 62Sn36Pb2Ag) and lead-free (SAC105, SAC305, and SAC405) solder alloys under temperature profiles: 0°C (Tmin) to 100°C (Tmax), −40°C to 85 °C, −40 °C to 125 °C, and −40 °C to 150 °C. Results indicate that SAC305 exhibited the highest equivalent stress, while 63Sn37Pb demonstrated the highest plastic strain and creep strain energy density. SAC105 displayed the lowest stress and strain parameters. Moreover, increasing the thermal cycling temperature range intensifies stress, strain, and damage parameters, with −40 °C to 150 °C showing the highest magnitudes. SAC405 exhibited superior thermal fatigue life compared to other alloys, with its cycles to failure outperforming 63Sn37Pb, SAC105, 63Sn36Pb2Ag, and SAC305 by 16832, 11992, 6218, and 3601 cycles, respectively. Lower temperature ranges enhance thermal fatigue life, with 0 °C to 100 °C recording 8%, 33%, and 53% higher life than −40 °C to 85 °C, −40 °C to 125 °C, and −40 °C to 150 °C, respectively. Notably, higher silver content and lower temperature ranges were associated with increased thermal fatigue life, providing valuable insights for BGA solder joint reliability enhancement.

Random Vibration Fatigue Life Prediction of Nano-Silver Solder Joint

Nano-silver is a very potential electronic interconnection material. It’s excellent physical and chemical properties, high thermal conductivity and good electrical conductivity make it very suitable for high power electronic devices. In practical engineering, 20% of the failure of electronic products is caused by vibration load, so it is necessary to study the vibration reliability of interconnected materials. In this paper, the modal and random vibration finite element analysis of nano-silver solder joints were analyzed with workbench software. Predicting random vibration fatigue life of nano-silver solder joint by Coffin-Manson high cycle fatigue empirical formula, Miner’s linear cumulative damage theory and Steinberg model. The random vibration fatigue life of the nanosilver solder joint is 8342 h. It is found that the vibration reliability of nano-silver is inferior to Sn3.0Ag0.5Cu and Sn63Pb37 and the diameter of solder joints and PCB thickness are proportional to the vibration fatigue life, and the PCB thickness has a greater effect on the vibration life than the solder joint diameter. Solder joint height and pad thickness are inversely proportional to vibration fatigue life, and pad thickness has little effect on vibration fatigue life.

Thermal Fatigue Failure of Micro-Solder Joints in Electronic Packaging Devices: A Review

In electronic packaging products in the service process, the solder joints experience thermal fatigue due to temperature cycles, which have a significant influence on the performance of electronic products and the reliability of solder joints. In this paper, the thermal fatigue failure mechanism of solder joints in microelectronic packages, the microstructure changes of the thermal fatigue process, the influence factors on the joint fatigue life, and the simulation analysis and forecasting of thermal fatigue life are reviewed. The results show that the solder joints are heterogeneously coarsened, and this leads to fatigue cracks occurring under the elevated high-temperature phase of alternating temperature cycles. However, the thickness of the solder and the hold time in the high-temperature phase do not significantly influence the thermal fatigue. The coarsened region and the IMC layer thicken with the number of cycles, and the cracks initiate and propagate along the interface between the intermetallic compound (IMC) layer and coarsened region, eventually leading to solder joint failure. For lead-containing and lead-free solders, the lead-containing solder shows a faster fatigue crack growth rate and propagates by transgranular mode. Temperature and frequency affect the thermal fatigue life of solder joints to different degrees, and the fatigue lifetime of solder joints can be predicted through a variety of methods and simulated crack trajectories, but also through the use of a unified constitutive model and finite element analysis for prediction.

Reliability and thermal fatigue life prediction of solder joints using nanoindentation

The construction of accurate constitutive equations is critical for the reliability analysis of the solder joints in high-density interconnect. However, there are some distinct differences between the actual solder joints and conventional bulk solder in determining the parameters for constitutive equations. In this work, the Young's modulus and hardness of various grain regions are experimentally investigated using electron backscatter diffraction and nanoindentation for the Sn-3.0Ag-0.5Cu polycrystalline and single-grain solder joints. The disparities in the Young's modulus and hardness of different grain regions in the polycrystalline solder joint are up to 25.11% and 28.34%, respectively, while those of the single-grain solder joint exhibit stability. It indicates the anisotropy of β-Sn grains and the size effects between actual solder joints and bulk solder materials. Furthermore, a method is proposed to determine the parameters of the Anand constitutive equations using high-temperature nanoindentation creep data. A flip-chip assembly in thermal shock conditions is numerically investigated. The Darveaux model is employed to predict the thermal fatigue life of the critical solder joint. Compared to experimental results, the life prediction of the solder joint using nanoindentation is found to be accurate. A concept of life correction factor n has been proposed to improve the accuracy of the predicted life.

Prediction of mechanical properties and fatigue life of nanosilver slurry in chip interconnection

This article investigates the failure mode and mechanism of copper pillar solder joints in temperature cycling experiments, focusing on a Cu/nano Ag/Cu solder joint structure. The hot pressing bonding condition at 300 °C with insulation for 10 s is chosen for the experiments. Based on the life test results, the thermal cycling fatigue life of the nanosilver solder joint is determined to be 2050 cycles. To gain further insights, finite element software ANSYS is employed to simulate nanosilver solder joints in flip chips, revealing the stress–strain distribution within the solder joints. The simulation utilizes the Anand viscoplastic constitutive model for the solder joint, providing a reasonable representation of the stress–strain behavior under thermal cycling load. Notably, the simulation highlights that the maximum stress and strain occur in the contact area between the solder joint and the copper column. To enhance accuracy, the calculation equation is refined using relevant experience, resulting in a prediction of the thermal fatigue life of nanosilver solder joints. This prediction aligns closely with the experimental results. The research outcomes not only contribute valuable insights into the behavior of nanosilver solder but also serve as a reference for its application in electronic packaging.

Hydrogen evolution and thermal treatments for removal of plating induced impurities from Ni to extend life of solder joints

As operating temperatures and times continue to increase for solder joints with Ni pads, large voids inevitably form at the intermetallic compound (IMC) – solder interface when the IMC thickness nears 5 μm. This leads to a significant reduction of strength, thermal conductivity, and fatigue resistance, and in small joints, also to electromigration life degradation. We have identified the voiding root cause as the breakdown and subsequent outgassing of deposition-related Ni-oxo-hydroxide impurities, impractical to avoid during Ni commercial electroplating. This work takes as the starting point a successful post-deposition voiding-mitigation treatment with 24-hour annealing at 450 °C. It then explores the possibility of rendering this routine more practical by lowering the annealing temperature down to 250 °C. While that approach shows relatively limited success, an alternative strategy, involving treatment with hydrogen evolution reaction for one hour at room temperature, alone or in combination with thermal, leads to a substantial reduction in the voiding propensity.

Internal Bump Cracking Risk Assessment for Flip Chip Ball Grid Array Package During Board Level Reliability Test Through Finite Element Analysis

The performance of semiconductor devices during board-level reliability (BLR) thermal cycling tests continues to be a concern in different applications. The primary focus of those BLR tests is to evaluate the fatigue life of external solder joints between the package and printed circuit board (PCB). For flip-chip ball grid array (FCBGA) package technology, internal solder bumps can also crack and result in open electrical failure. This type of BLR failure has yet to be widely reported in the literature. This article presents failures due to internal solder bump cracks during the BLR test. Failure analysis (FA) clearly shows the cracking location strongly depends on bump density. Finite Element Analysis (FEA) based simulation is performed to understand the failure mechanism. Unlike the standard BLR modeling approach, which focuses on predicting external solder joint fatigue life with correlated data, simulation here has to capture the entire internal bump pattern in the global BLR model. The need to capture the entirety of the bump scheme poses a significant challenge to managing the global model size with a reasonable meshing count and running time. Therefore, a customized post-process approach is developed to analyze bump density impact and enable design optimization.

Optimization of the Boundary Conditions of a Board Level Reliability Test Board to Maximize the Fatigue Life of Ball Grid Array Solder Joints under Thermal Cycling and Random Vibration.

We investigated the screw hole position of a board level reliability (BLR) test board to improve the fatigue reliability of solder joints under thermal cycling and random vibration. We developed a finite element model of a BLR test board and derived the plastic strain energy density and 1-sigma stress, which are the main parameters influencing the fatigue life of solder joints under thermal cycling and random vibration, respectively. We analyzed the correlation between the screw hole position and the main parameters of the fatigue life through sensitivity analysis. By performing multi-objective optimization, we determined the screw hole position that maximizes the fatigue life of solder joints under thermal cycling and random vibration. With the optimal screw hole position, the fatigue life significantly increased under thermal cycling and random vibration compared to the BLR test board with the initial screw hole position.

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.

Study of the effect of crystal orientation on the mechanical response and fatigue life of solder joints under thermal cycling by crystal plasticity

Electronic products are subjected to thermal cycling caused by power cycling in service processes. Owing to the difference in the coefficients of thermal expansion (CTEs) of solder joints and other packaging materials, solder joints suffer from thermomechanical fatigue, and cracks appear at their bonding interfaces. Solder joints are usually a single grain or three grains with Beachball morphology, and their composition is Sn-based Pb-free SAC305 (96.5Sn–3.0Ag–0.5Cu wt.%) solder, which exhibits obvious anisotropic mechanical behavior. This study investigated a thermal cycling simulation of Plastic Ball Grid Array (PBGA) packaging, in which the Anand model was used for solder joints, and the outermost solder joint was found to be a dangerous point. Sub-models were then established for this solder joint with several typical crystal orientations. The effect of crystal orientation under thermal cycling was simulated using thermomechanical crystal plasticity. When the c-axis of Sn crystal was perpendicular to the substrate, the deformation resistance was the largest, and the accumulation of equivalent plastic strain and strain energy dissipation was the slowest; hence, the fatigue life was the longest. As the angle between the c-axis and the substrate decreased, the deformation accumulated faster. When the c-axis was parallel to the substrate, the deformation of the solder joint was the fastest, and thus this joint was the first to fail and had the shortest fatigue life. In addition, the simulation of three grains indicated that orientations and their distributions had an influence on the shear strain accumulation of slip systems and fatigue life.

Effect of boundary conditions on fatigue life of board-level BGA solder joints under random vibration

Effect of boundary conditions on fatigue life of board-level BGA solder joints under random vibration

Comparison of nano-silver solder joints and SAC305 based on ANSYS simulation and life prediction

With the rapid development of microelectronic interconnection technology, the reliability requirements of electronic products are becoming higher and higher. Among them, temperature has the greatest impact on electronic devices. Due to the different coefficients of thermal expansion (CTE) between the many materials of a chip, the inside of a solder joint is subjected to cyclic temperature action. Under the effect of cyclic temperature, the solder joints are subject to internal fracture resulting in the failure of the solder joint. Therefore, it is necessary to find a more reliable material for the solder joint. In this paper, the advantages and disadvantages of pure silver material and low silver material are compared by finite element simulation analysis of nano-silver pure silver material and SAC305 low silver material, and the fatigue life prediction of nano-silveris predicted by a life prediction model. Then, using the Electric Power Research Institute estimation method to estimate the fatigue life of solder joints, the results are compared with those calculated by the finite element method.

Neural-fuzzy machine learning approach for the fatigue-creep reliability modeling of SAC305 solder joints

The accuracy of reliability models is one of the most problematic issues that must be considered for the life of electronic assemblies, particularly those used for critical applications. The reliability of electronics is limited by the fatigue life of interconnected solder materials, which is influenced by many factors. This paper provides a method to build a robust machine-learning reliability model to predict the life of solder joints in common applications. The impacts of combined fatigue and creep stresses on solder joints are also investigated in this paper. The common alloy used in solder joint fabrication is SAC305 (Sn–Ag–Cu). The test vehicle includes individual solder joints of SAC305 alloy assembled on a printed circuit board. The effects of testing temperature, stress amplitude, and creep dwell time on the life of solder joints were considered. A two-parameter Weibull distribution was utilized to analyze the fatigue life. Inelastic work and plastic strain were extracted from the stress–strain curves. Then, Artificial Neural Networks (ANNs) were used to build a machine learning model to predict characteristic life obtained from the Weibull analysis. The inelastic work and plastic stains were also considered in the ANN model. Fuzzy logic was used to combine the process parameters and fatigue properties and to construct the final life prediction model. Then a relationship equation between the comprehensive output measure obtained from the fuzzy system and the life was determined using a nonlinear optimizer. The results indicated that increasing the stress level, testing temperature, and creep dwell time decreases reliability. The case of long creep dwell time at elevated temperatures is worst in terms of impact on reliability. Finally, a single robust reliability model was computed as a function of the fatigue properties and process parameters. A significant enhancement of the prediction model was achieved compared to the stress–life equations.

Stout hourglass – The ideal shape for robust solder joints

The optimum shape of solder joints in an electronic assembly that experienced differential thermal expansion between its constituting members was analysed using advanced beam analysis. The advanced beam analysis is capable of modeling the exact geometry of solder joints. The shearing and bending stresses in solder joints of multiple shapes: barrel, slender hourglass, and stout hourglass, were evaluated. The barrel-shape solder joints returned the highest magnitudes of shear stress, bending stress, and von mises stress. The slender-hourglass-shape solder joints that have superior in-plane shear compliance returned the lowest magnitude of shear stress at 10% that of the barrel-shape solder joints, and a von mises stress that is 27% that of the barrel-shape solder joints. The stout-hourglass-shape solder joints returned the lowest magnitude of bending stress at 13% that of the barrel-shape solder joints, and a von mises stress that is 14% that of the barrel-shape solder joints. The substantial reduction in the magnitude of von mises stress by the stout-hourglass-shape solder joints is estimated to give an eight-time improvement in the temperature cycling life of solder joints.

Reliability modeling of the fatigue life of lead-free solder joints at different testing temperatures and load levels using the Arrhenius model

Reliability of the microelectronic interconnection materials for electronic packages has a significant impact on the fatigue properties of the electronic assemblies. This is due to the correlation between solder joints reliability and the most frequent failure modes seen in electronic devices. Due to their superior mechanical and fatigue properties, SAC alloys have supplanted Pb-solder alloys as one of the most commonly used solder materials used as interconnection joints on electronic packages. The main aim of this study is to develop a prediction model of the fatigue life of the solder joints as a function of the experimental conditions. Using a customized experimental setup, an accelerated fatigue shear test is applied to examine the fatigue life of the individual SAC305 solder joints at actual setting conditions. OSP surface finish and solder mask defined are used in the studied test vehicle. The fatigue test includes three levels of stress amplitude and four levels of testing temperature. A two-parameter Weibull distribution is used for the reliability analysis for the fatigue life of the solder joints. A stress–strain curve is plotted for each cycle to construct the hysteresis loop at each cyclic load and testing temperature. The acquired hysteresis loop is used to estimate the inelastic work per cycle and plastic strain. The Morrow energy and Coffin Manson models are employed to describe the effects of the fatigue properties on the fatigue life of the solder joints. The Arrhenius model is implemented to illustrate the evolutions in the stress life, Morrow, and Coffin Manson equations at various testing temperatures. The fatigue life of SAC305 solder joints is then predicted using a general reliability model as a function of the stress amplitude and testing temperature.

Effects of interface cracks on reliability of surface mount technology interconnection in service environment

PurposeSurface mount technology (SMT) is widely used and plays an important role in electronic equipment. The purpose of this paper is to reveal the effects of interface cracks on the fatigue life of SMT solder joint under service load and to provide some valuable reference information for improving service reliability of SMT packages.Design/methodology/approachA 3D geometric model of SMT package is established. The mechanical properties of SMT solder joint under thermal cycling load and random vibration load were solved by 3D finite element analysis. The fatigue life of SMT solder joint under different loads can be calculated by using the modified Coffin–Manson model and high-cycle fatigue model.FindingsThe results revealed that cracks at different locations and propagation directions have different effect on the fatigue life of the SMT solder joint. From the location of the cracks, Crack 1 has the most significant impact on the thermal fatigue life of the solder joint. Under the same thermal cycling conditions, its life has decreased by 46.98%, followed by Crack 2, Crack 4 and Crack 3. On the other hand, under the same random vibration load, Crack 4 has the most significant impact on the solder joint fatigue life, reducing its life by 81.39%, followed by Crack 1, Crack 3 and Crack 2. From the crack propagation direction, with the increase of crack depth, the thermal fatigue life of the SMT solder joint decreases sharply at first and then continues to decline almost linearly. The random vibration fatigue life of the solder joint decreases continuously with the increase of crack depth. From the crack depth of 0.01 mm to 0.05 mm, the random vibration fatigue life decreases by 86.75%. When the crack width increases, the thermal and random vibration fatigue life of the solder joint decreases almost linearly.Originality/valueThis paper investigates the effects of interface cracks on the fatigue life and provides useful information on the reliability of SMT packages.

A Hybrid Method for Predicting Fatigue Life of Lead-Free Solder Joints Under Coupled Electrical–Thermal–Mechanical Fields

A hybrid method was developed in this study for fatigue life prediction (FLP) of lead-free solder (LFS) joints in ball grid array package under the coupled electrical–thermal–mechanical (ETM) fields. A modified constitutive model for lead-free solder joints under coupled ETM fields was proposed to describe the mechanical and fatigue behavior of solder joints under coupled ETM fields. A modified damage model under coupled ETM fields was then developed to obtain the fatigue life of LFS joints under coupled ETM fields. Uniaxial tension tests of an Sn–3.0Ag–0.5Cu (SAC305) solders and coupled multifields fatigue experiments were performed to verify the accuracy, applicability and validity by the modified constitutive model and fatigue damage model under coupled ETM fields. Based on the modified constitutive model and fatigue damage model, a hybrid method, including current, temperature and mechanics parameters, was proposed for the FLP of the LFS joints, which was demonstrated to be able to predict the results well. A hybrid method provides an idea for investigating the fatigue life of lead-free solder joints in coupled fields.

Class I Creep Deformation of Sn–Ag–Cu Containing Solid Solution Elements and Its Effect on Thermal Fatigue Life of Solder Joints

Class I Creep Deformation of Sn–Ag–Cu Containing Solid Solution Elements and Its Effect on Thermal Fatigue Life of Solder Joints

Research on the reliability of Micro LED high-density solder joints under thermal cycling conditions

For the purpose of studying the effect of high-density, small-size solder joints on the thermal fatigue life of display devices, a 3D model of the corresponding device structure is established, using finite element analysis methods, and using Anand constitutive equations and Coffin-Manson life prediction models. The equivalent stress and strain change law of an indium solder joint with a diameter of 10 μm under thermal cycling loading conditions is explored, and the key position of the solder joint damage is inferred based on the simulated strain cloud diagram. In addition, the influence of different bump height, bump contact area and Under-Bump Metallization (UBM) thickness on the thermal fatigue life of solder joints is studied separately. The final simulation results show that the location where the solder joint may be damaged first is at the point on the outer side where the solder joint is connected to the UBM on the edge away from the center point. The height of the bump and the contact area of the bump have a significant effect on its thermal fatigue life. In the actual experiment, we should focus on the impact of this aspect.