Failure Mode Of Solder Joints Research Articles

Identification of Solder Joint Failure Modes Using Machine Learning

Identification of Solder Joint Failure Modes Using Machine Learning

The design of low-temperature solder alloys and the comparison of mechanical performance of solder joints on ENIG and ENEPIG interface

In recent years, in order to adapt to the trend of low-temperature assembly and integration, low-temperature hybrid solders with multiple elements added to the tin solder matrix have been investigated. In this regard, the morphology and size of intermetallic compounds (IMCs) are altered by adding some alloying elements, and the strength of solder joints is improved to some extent. Different pad surface treatments affect the growth of IMC, which leads to various failure modes in interconnect solder joints. Therefore, it is necessary to study the interfacial reaction, microstructure and mechanical properties of hybrid solder and different metal pads to explore the growth mechanism of IMC and the failure modes of solder joints. In this paper, mixed Sn–3Ag-0.5Cu/Sn–58Bi low-temperature solder joints on Au/Ni/Cu (ENIG) and Au/Pd/Ni/Cu (ENEPIG) substrates are investigated. The results show that the addition of palladium element can change the IMC morphology, refine the grain size of the hybrid solder joints, and affect the fracture failure mode of the solder joints under shear force. The average shear strength is significantly higher than that of solder joints with ENIG surfaces under different process parameters. Thermodynamic calculations of enthalpy change and the effect of Jackson's parameter α value on IMC morphology are also investigated in this paper. The addition of palladium elements increases the α value and is more favorable to the formation of columnar grains. This provides guidance for the grain growth of IMC in hybrid solder joints with added alloying elements.

Development of resistance spot welding material card for dissimilar automobile plates

Taking the resistance spot welding of automotive steel DC04-HC420LA as an example, the failure forces including cross tensile, shear tensile and pull-out tensile tests were obtained in the test for dissimilar materials. The fracture failure model of resistance spot welding of dissimilar materials was established by the finite element analysis method. It was compared with the experimental data to verify the accuracy of the finite element analysis model of solder joint failure mode. And then the data of the welding material card was calibrated and verified. Finally, an accurate dissimilar welding material card was established, which can predict the solder joint failure of the key sensitive parts in the whole vehicle CAE collision analysis, and improve the accuracy of CAE collision analysis.

Effect of high current pulses on solder interfacial reaction and interconnect reliability

The trend of electrification and miniaturization brings the reliability of interconnects to the forefront. The solder joints are subjected to thermo-mechanical mismatch due to the Joule heating and electromigration (EM)-induced degradation under high current stressing conditions. However, most of the studies are limited to lab test samples or lab test conditions, which lack transferability in engineering applications. In this paper, automotive electronic components are studied subjected to field-like current pulse conditions. The work aims to understand the field-relevant failure modes of solder joints exposed to high current stressing via experimental and numerical investigations. Shunt components with and without Ni plating are analyzed in power cycling tests. A polarity effect is observed in the growth of intermetallic compounds (IMCs). The thickness of IMC at the anode exhibits an approximately linear growth with current stressing time, whereas the thickness of IMC at the cathode remains almost unchanged or slightly decreased. Ni, as diffusion barrier, serves to restrain Cu consumption from the terminals of shunts and also reduces Cu mass transport into and within the solder. The net Cu flux at the interface and in the solder is discussed to analyze the IMC growth kinetics. The shunts with Ni plating undergo less EM of Cu and yield longer lifetime. Voids and crack formation are detected in computer tomography (CT) scans and cross-sectional analysis by scanning electron microscopy (SEM). Finite element method (FEM) is implemented to simulate thermo-electro-mechanical fields of the assembly under power cycling test conditions. The distribution of divergence of material flux density corresponds well with the location of voids formation and provides good estimation for the lifetime.

Study on Establishing Degradation Model of Chip Solder Joint Material under Coupled Stress.

The chip is the core component of the integrated circuit. Degradation and failure of chip solder joints can directly lead to function loss of the integrated circuit. In order to establish the degradation model of chip solder joints under coupled stress, this paper takes quad flat package (QFP) chip solder joints as the study object. First, solder joint degradation data and failure samples were obtained through fatigue tests under coupled stress. Three types of micro failure modes of solder joints were obtained by scanning electron microscope (SEM) analysis and finite element model (FEM) simulation results. Second, the characterization of degradation data was obtained by the principal component of Mahalanobis distance (PCMD) algorithm. It is found that solder joint degradation is divided into three stages: strain accumulation stage, crack propagation stage, and failure stage. Later, Coffin–Manson model and Paris model were modified based on the PCMD health index and strain simulation. The function relationship between strain accumulation time, crack propagation time, and strain was determined, respectively. Solder joint degradation models at different degradation stage were established. Finally, through strain simulation, the models can predict the strain accumulation time and failure time effectively under each failure mode, and their prediction accuracy is above 85%.

Study on Chip Reliability Modeling Based on Mutually Dependent Competing Failure of Solder Joints in Different Failure Modes

The chip is a core functional component. Its reliability plays a vital role in electronic equipment normal operation. As the typical cause for chip malfunction, the solder joint degradation is selected to study chip reliability. The degradation models of solder joint in different failure modes are established through data-driven and failure physical model, and chip reliability model is constructed based on mutually competing failures of multiple solder joints. First, the chip reliability degradation test and finite element modeling(FEM) are carried out under coupled environment stress. The solder joint failure modes and degradation processes are studied through the analysis of test data, microstructure and mechanical simulation. Then, solder joint degradation models are established based on Coffin-Manson and Paris functions that have been modified by a data-driven method. Taking the solder joint failure time of degradation model as the characteristic parameter of Weibull distribution, the solder joint reliability function is obtained. Finally, mutually dependent competing failure theory is cited to describe the correlation about solder joint reliability of different failure modes, then the chip reliability model is established. The parameter estimation is realized by the inference function for margins (IFM) method. From verification tests, results show models are highly consistent with the actual reliability, indicting our reliability modeling method achieves the transition from underlying solder joint level to integrated component level. The joint application of different models can make up for the deficiencies of the single model and obtain more accurate results. In addition, we determined that intermetallic compounds (IMC) are main source of model error.

Synergetic effect of strain rate and electroplated Cu film for shear strength of solder/Kovar joints

The effects of strain rate and electroplated Cu on the shear fracture behaviors of Sn37Pb/electroplated Cu (EPC)/Kovar solder joints were investigated after reflowing at 250 °C for 5 min. The Kovar was electroplated with 4.1 µm thick layer of Ni and 1.9 µm thick layer of Au. The copper electroplating time were 2, 5, 10 and 20 min, respectively, resulting in a different deposited thicknesses of Cu film on the Kovar substrate. The shear tests of Sn37Pb/EPC/Kovar joints were performed with different strain rates ranging from 8.3 × 10−2 to 1.6 s−1 to study the shear fracture behavior. Experimental results showed that the shear strength and failure mode of solder joints were affected by the thickness of electroplated Cu film and the applied strain rate. The shear strength of solder joint demonstrated increment at first and then decrement as the applied strain rate increased. It was observed that the shear failure mode of solder joints is well known to have experienced a transition from ductile fracture with the low strain rates (8.33 × 10−2 s−1 and 3.33 × 10− 1 s−1) to a mixed fracture with the intermediate strain rate (6.67 × 10−1 s−1) and high strain rates (1 s−1, 1.33 s−1 and 1.67 s−1). Studies in the shear properties of solder joints with electroplated Cu layer indicated that the electroplated Cu on the Kovar substrate has a significant improvement in the shear strength of solder joints. With increasing in the deposited thickness, the shear strength of solder joints increased when the deposited thickness was no more than 3.3 µm. Subsequently, the shear strength started to drop as the deposited thickness further increased.

Relationship Between the Intermetallic Compounds Growth and the Microcracking Behavior of Lead-Free Solder Joints

This paper investigates the formation and the growth of the intermetallic compound (IMC) layer at the interface between the Sn3.0Ag0.5Cu Pb-free solder and the Cu substrate during isothermal aging at 150 °C. We measure the thickness of the IMC layer and the roughness of the solder/IMC interface, and these two factors are assumed to control the tensile behavior of the solder joints. First, it utilizes the tensile tests of the aged solder joints for analyzing the effect of the IMC growth on the tensile behavior of the solder joints. Then, the microcracking behavior of the IMC layer is investigated by finite element method (FEM). In addition, qualitative numerical simulations are applied to study the effect of the IMC layer thickness and the solder/IMC interfacial roughness on the overall response and the failure mode of solder joints. The experimental results indicate that when the aging time increases, both the thickness and the roughness of the IMC layer have a strong influence on the strength and the failure mode of solder joints. The numerical simulation results suggest that the overall strength of solder joints is reduced when the IMC layer is thick and the solder/IMC interface is rough, and the dominant failure mode migrates to the microcracks within the IMC layer when the IMC layer is thick and the solder/IMC interface is flat.

Assessment of mechanical reliability of surface mounted capacitor by an accelerated shear fatigue test technique

In this study mechanical reliability of Sn3.5Ag0.75Cu solder joints in SMD capacitors has been investigated. Tensile response of the solder joint with respect to thicknesses and aging conditions was studied by using Cu/SnAgCu/Cu model samples. Isothermal lifetime curves of SMD devices subjected to high strain vibrational loading were obtained by using an ultrasonic fatigue testing set-up. Mechanical reliability and the failure modes of solder joints in the SMD capacitors were found to be highly dependent on the microstructure of the solder and the intermetallic compound layer and the testing temperature. Testing at elevated temperature resulted in a clear change of crack path and fracture mode of the solder joints.

Effects of the intermetallic compound microstructure on the tensile behavior of Sn3.0Ag0.5Cu/Cu solder joint under various strain rates

The effects of the intermetallic compound (IMC) microstructure and the strain rate on the tensile strength and failure mode of Pb-free solder joints are investigated. The samples of Sn3.0Ag0.5Cu/Cu solder joints are aged isothermally at 150°C for 0, 72, 288 and 500h, and the thickness of the IMC layer and the roughness of the solder/IMC interface are measured and used to characterize the microstructure evolution of the IMC layer. The tensile tests of the aged solder joints are conducted under the strain rates of 2×10−4, 2×10−2 and 2s−1. The results indicate that both the thickness and roughness of the IMC layer have influence on the strength and failure mode of the solder joint. With the increase of the aging time, the thickness of the IMC layer increases and the roughness of the solder/IMC interface decreases, as a result, the tensile strength of the solder joint decreases and the dominant failure mode migrates from the ductile fracture in the bulk solder to the brittle fracture in the IMC layer. There is a positive correlation between the tensile strength of the solder joint and the stain rate applied during the test. With the increase of the strain rate, the failure mode migrates from the ductile fracture in the bulk solder to the brittle fracture in the IMC layer.

Solder Joint Failure Modes in the Conventional Crystalline Si Module

In the conventional PV module system based on crystalline Si solar cell, solder joint has been used for electrical connection in the four positions such as (1) Cu ribbon interconnection on Ag electrode of Si solar cell, (2) electrical connection of Cu ribbon, (3) by-pass diode connection in the junction box, (4) inverter connection. There are two kinds of solder joint failure modes, (1) Ag or Cu leaching into solder and (2) long-term solder joint fatigue. In both cases, crack is generated and DC arcing discharge may happen at the crack. It is well known phenomena as Ag leaching in the electronic packaging that Ag easily dissolves into solder during the soldering process. Because Ag3Sn compound formed in the solder as result of Ag leaching is rigid and brittle material, crack is generated at the interface between solder and Ag dissolved area. It induces to increase contact resistivity of Cu ribbon and Ag electrode of Si cell and to disconnect the Cu ribbon from Si cell in the worst case. It has been reported as solder joint failure that the bus line of Cu ribbon heated up is one of suspicious causes of PV fire. [4] We observed the two types of crack after 1000 thermal cycles from +85 to -40 degree C. The crack at the interface between Cu ribbon and Ag electrode may be due to Ag leaching. The crack inside solder joint composed of large grain growing by repeated thermal stress is typical long-term fatigue. Considering highly reliable PV module system, we should pay attention to protect solder joint failure.

COHESIVE ZONE MODELING OF INTERGRANULAR CRACKING OF INTERMETALLIC COMPOUNDS IN SOLDER JOINTS

In order to investigate the effect of the microstructure of intermetallic compound (IMC) on the micro and macro mechanical behaviors of solder joints, a finite element based numerical approach is developed to simulate initiation, propagation and coalescence of microcracks along the grain boundaries in the IMC layer. In the approach, the topological microstructure of IMC grains is generated by Voronoi tessellations, and the proposed cohesive interface elements are embedded between the grain boundaries. By the proposed approach, the effect of grain shape and randomly distributed grain interfacial defects on the microcrack pattern and the overall response, and the effect of IMC microstructure on the strength and the failure mode of solder joints, are investigated. The results indicate that the grain shape has little effect on the overall mechanical response, but affects the cracking path. In the model with Weibull distributed grain interfacial strength, the weak grain interface plays a key role in the overall strength. The thickness of the IMC layer has a significant influence on the strength and failure mode of solder joints, while the roughness of the solder/IMC interface has an influence on the failure mode only.

Thermal Aging Effects on the Thermal Cycling Reliability of Lead-Free Fine Pitch Packages

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. A direct and deleterious effect on packaging reliability has been observed during elevated temperature isothermal aging for fine-pitch ball grid array (BGA) packages with Sn-1.0Ag-0.5Cu (SAC105), Sn-3.0Ag-0.5Cu (SAC305), and Sn-37Pb solder ball interconnects. Package sizes range from 19 mm with 0.8-mm pitch BGAs to 5 mm with 0.4-mm pitch BGAs with three different board finishes (ImSn, ImAg, and SnPb) previously studied. This paper presents the latest results from an on-going investigation on the aging temperatures were 25 °C, 55 °C, 85 °C, and 125 °C, applied for a period of 12 months. Subsequently, the specimens were thermally cycled from -40°C to 125 °C with 15 min dwell times at the high temperature. Weibull analysis of failures versus cycle number show a ~ 57% reduction in package lifetimes when aged at 125 °C compared to no aging for 19 mm BGAs, for MLFs the degradation is even worse, more than 58% reduction in experiment result. In contrast, the reliability performance of Sn-37Pb is much more stable over long time up to 12 months and temperature. We also study the evolution during isothermal aging, which is one of the major failure modes of solder joints due to its high homologous temperature. The degradation is observed for both SAC alloys on all tested package sizes and board finishes. For the 19 mm SAC105 case, e.g., there was a 53% (57%) reduction of characteristic lifetime at 125 °C for 6 months (12 months) compared to room temperature aging. The trends are in the expected directions; namely, the reliability is reduced when using higher aging temperatures, smaller solder balls, and SAC105. The dominant failure mode can be associated with the growth of Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> intermetallic compounds during the aging, particularly on the pad side.

Reliability Assessment of Preloaded Solder Joint Under Thermal Cycling

The ever increasing power density in modern semiconductor devices requires heat dissipation solution such as heat sink to remove heat away from the device. A compressive loading is usually applied to reduce the interfacial thermal resistance between package and heat sink. In this paper, both experimental approaches and numerical modeling were employed to study the effect of compressive loading on the interconnect reliability under thermal cycling conditions. A special loading fixture which simulated the heat sink was designed to apply compressive loading to the package. The JEDEC standard thermal cycle tests were performed and the resistance of daisy chained circuits was in situ measured. The time to crack initiation and time to permanent failure were identified separately based on in situ resistance measurement results. Failure analysis has been performed to identify the failure modes of solder joint with and without the presence of compressive loading. A finite element based thermal-fatigue life prediction model for SAC305 solder joint under compressive loading was also developed to understand the thermal-fatigue crack behaviors of solder joint and successfully validated with the experimental results.

Impact reliability estimation of lead free solder joint with IMC layer

To secure the reliability of lead free solder is a critical issue for a chip-scale packaging process. While lots of researches on the solder reliability have been conducted by applying numerical simulation techniques, researches on IMC (intermetallic compound) are not intensively condoned due to its thin thickness, geometric irregularity and so on. However, the IMC layer which is generated during the solder bumping process between solder and substrate is known as a key material determining the failure of solder joint. In this paper, the failure mode of solder joint is investigated by simulating the board level drop test which is described in the JEDEC standard. In this context, the IMC layer is produced by an ENEPIG process. Material properties of the IMC layer are obtained by performing a nano-indentation test for several points in the IMC region and the resulting test data are used for 3-dimensional finite element analyses to simulate the failure behavior. As a result, the solder joint corresponding to ENEPIG(0.1/0.8/0.12) surface finishing shows more resistant tendency against the drop impact failure than any other solder joint owing to a strain softening effect prior to the failure. The solder joint corresponding to ENEPIG(5/0.4/0.12) surface finishing, however, shows a sudden brittle failure mode due to the brittle characteristics of Nickel layer.

Damage mechanics of solder joints viscoplasticity, implementation, simulation, and verification

This paper presents a damage mechanics methodology and its successful implementation for the progressive damage of solder joints widely used for electronic packages, enabling robust design, virtual qualification, and predictive reliability of components and assembly processes of electronic products. A unified viscoplastic constitutive framework with damage evolution and failure criteria has been developed and implemented into a commercially available tool to model time-rate-temperature dependent nonlinear properties of solder materials. As primary failure mode of solder joints, cracks on a solder joint can be automatically initiated and propagated by damage evolution with failure criteria under various loading conditions. Dynamic failure processes of solder joints of an electronic component assembled on PCB have been demonstrated for real-world case study under mechanical and thermal cyclic loadings in three-dimensional cases. The characteristics of crack initiation and propagation have been well verified by microscopic analyses of the failed components collected from the field.

Implementing lead‐free solders – the performance aspects

Purpose – To draw attention to the need to consider design and performance, as well as production, in the implementation of lead‐free solders.Design/methodology/approach – The potential failure modes of solder joints and their underlying causes are reviewed. A hypothetical design exercise is employed to demonstrate key requirements for reliable design.Findings – The substantial variation in influential mechanical properties over the ranges of stress, temperature and strain rate is likely to be encountered in service. In addition to these three parameters, there is the need to consider time‐temperature profiles in the service cycle and the prior thermal history of the joint materials.Originality/value – The demonstration that reliable design and life prediction can only be achieved by employing appropriate properties in appropriate constitutive expressions.

Effects of process conditions on reliability, microstructure evolution and failure modes of SnAgCu solder joints

In this study, microstructure evolution at intermetallic interfaces in SnAgCu solder joints of an area array component was investigated at various stages of a thermal cycling test. Failure modes of solder joints were analyzed to determine the effects of process conditions on crack propagation. Lead-free printed-circuit-board (PCB) assemblies were carried out using different foot print designs on PCBs, solder paste deposition volume and reflow profiles. Lead-free SnAgCu plastic-ball-grid-array (PBGA) components were assembled onto PCBs using SnAgCu solder paste. The assembled boards were subjected to the thermal cycling test (−40 °C/+125 °C), and crack initiation and crack propagation during the test were studied. Microstructure analysis and measurements of interface intermetallic growth were conducted using samples after 0, 1000, 2000 and 3000 thermal cycles. Failures were not found before 5700 thermal cycles and the characteristic lives of all solder joints produced using different process and design parameters were more than 7200 thermal cycles, indicating robust solder joints produced with a wide process window. In addition, the intermetallic interfaces were found to have Sn–Ni–Cu. The solder joints consisted of two Ag–Sn compounds exhibiting unique structures of Sn-rich and Ag-rich compounds. A crystalline star-shaped structure of Sn–Ni–Cu–P was also observed in a solder joint. The intermetallic thicknesses were less than 3 μm. The intermetallics growth was about 10% after 3000 thermal cycles. However, these compounds did not affect the reliability of the solder joints. Furthermore, findings in this study were compared with those in previous studies, and the comparison proved the validity of this study.

Effect of Cu stud microstructure and electroplating process on intermetallic compounds growth and reliability of flip-chip solder bump

In electroplating-based flip-chip technology, the Cu stud and solder deposition processes are two of the most important factors affecting the reliability of solder joints. The growth of Cu-Sn intermetallic compounds (IMC) also plays a critical role. In this paper, the effect of Cu stud surface roughness and microstructures on the reliability of solder joint was studied. The surface roughness of the Cu stud was increased as the Cu electroplating current density increased. The microstructural morphology of the Cu-Sn IMC layer was affected by Cu stud surface structure. We found the growth rate of IMC layer increased with the increasing of Cu stud grain size and surface roughness during aging test. The growth kinetics of Cu-Sn intermetallic compound formation for 63Sn/37Pb solder followed the Arrhenius equation with activation energy varied from 0.78 eV to 1.14 eV. The ratios of Cu/sub 3/Sn layer thickness to the total Cu-Sn IMC layer thickness was in the range of 0.5 to 0.15 for various Cu microstructures at 150/spl deg/C during thermal aging test. The shear strength of solder bump was measured after thermal aging and temperature/humidity tests. The relationship between electroplating process and reliability of solder joints was established. The failure mode of solder joints was also analyzed.