Durability Of Solder Joints Research Articles

Mechanical properties of Sn–Pb based solder joints and fatigue life prediction of PBGA package structure

Solder joints are generally the weakest part in electronic packaging structure whose fatigue life depends to a large extent on the durability of solder joints. In pursuit of a balance between environmental protection and soldering performance, commonly used Sn–Pb solder should be modified by adding other chemical elements to reduce Pb content. This work aims to investigate the performance of different solder materials and explore the impact of different electronic package structures. Firstly, tensile experiments are performed on three kinds of solders (Sn–Pb, Sn–Pb–In, Sn–Pb–Bi) to obtain their mechanical behavior, and then the constitutive laws of them are calibrated by Anand model. Additionally, finite element method (FEM) is used simulate the response of plastic ball grid array (PBGA) package structure under thermal cycles, and mechanical variables including deformation, equivalent stress, and equivalent strain are analyzed. Finally, Coffin-Manson and Engelmaier equations are adopted to predict the fatigue life of package structures and the effects of various factors such as solder materials, dimensions of components, and welding quality are further investigated. Results reveal that adding Bi into Sn–Pb solder can make the solder joints have better performance. From the perspective of optimum fatigue life, the plastic package thickness is recommended in the range of 0.8 mm–0.9 mm, the chip thickness is recommended as 0.35 mm, the substrate thickness is recommended to be less than 0.34 mm, and the ratio of stand-off height to solder ball diameter should be controlled between 0.6 and 0.7. According to the prediction, the solder ball diameter is suggested to be 0.54 mm so that fatigue life could reach 194 cycles, and the stand-off height for this package structure is suggested to be 0.36 mm so that fatigue life could reach 123 cycles.

Analysis of solder joint degradation and output power drop in silicon photovoltaic modules for reliability improvement

With the growing worldwide demand for clean, reliable, and economical energy supply, Photovoltaic (PV) modules have raised the bar for the field over the last years. However, PV modules have shown some shortcomings as environment temperature influences not only the maximum power generation but also the life expectancy of the module. PV reliability has become a topic of extreme importance driven by the extension of the warranty period over the years. This study investigates the degradation of solder joints. A 2-D Finite Element Model (FEM) has been computed to evaluate the lifetime of the solder joints and the cell power drop using accelerated thermal cycling tests in the range of −40 to 85 °C according to IEC 61215 standard. 2 models were used to predict the lifetime. In addition, 5 PV modules were conducted to thermal cycling tests to validate the model. The results reveal that during the thermal cycling test, the rear solder is damaged in a much earlier stage than the top solder. The deterioration of the rear solder area becomes steep after 1000 cycles and the power loss of the module reaches 2% between 600 and 750 thermal cycles depending upon the mathematical model. When compared to experimental results, the Coffin-Mason model is more accurate, with a maximum data disparity of 4.3%. A solder without any residual stress will eventually pass the 600TC test according to CSA/ANSI C450–18 and IEC TS 63209 ED1 standards. These findings inform on the solder joint durability which is an important parameter for the reliability analysis of a PV module.

The Study of Interfacial Reaction between SnAgCu (SAC) Lead-free Solder Alloys and Copper Substrate: A Short Review

This paper is aimed to review and study the interfacial reaction between SnAgCu (SAC) lead-free solder alloys and common copper substrates. Among the lead-free solders, a ternary solder alloys, SnAgCu (SAC) based solder, is leading the lead-free solders as it has excellent thermal and electrical properties. The interfacial between solder alloy and substrate comprise an important characteristic in the reliability performance of a solder alloy. As the current industry has driven to miniaturization, high integration and multifunctionality, the reliability and durability of solder joints are gained attention for its long-term performance of electronic products. Therefore, in this short review, the interfacial reaction between SAC solder alloys and copper substrate will be focused. Besides, the effects of the addition of microalloying elements into SAC solder alloys will be discussed.

Fatigue life prediction of solder joints with consideration of frequency, temperature and cracking energy density

Solder joints between semiconductors and a printed circuit board may fail due to temperature change or vibration. To assess the durability of solder joints a mechanical fatigue test was conducted instead of a thermal cycling test, and a resistance change was monitored to detect a failure at real time. Fatigue tests were conducted for five different semiconductors at three different frequencies, temperatures and displacements, and a fatigue life prediction equation with consideration of frequency, temperature and cracking energy density was proposed. It was shown that all the fatigue test data could be represented appropriately by the prediction equation.

1510 BGAはんだ接合部の振動負荷寿命に与える初期温度サイクルの影響(OS15.電子デバイス・電子材料と計算力学(3),オーガナイズドセッション)

1510 BGAはんだ接合部の振動負荷寿命に与える初期温度サイクルの影響(OS15.電子デバイス・電子材料と計算力学(3),オーガナイズドセッション)

A Global–Local Approach for Mechanical Deformation and Fatigue Durability of Microelectronic Packaging Systems

Abstract This paper presents a global–local methodology for predicting mechanical deformation and fatigue durability of solder joints in electronic packaging systems subject to cyclic thermal loading. It involves a global deformation analysis, a local critical solder–joint analysis, and a fatigue life analysis. The global deformation analysis includes a new optimization formulation for determining an equivalent model. The methodology developed was applied to fine pitch ball grid array (fpBGA) and super ball grid array (SBGA) packages. Selective experimental efforts were also undertaken to evaluate the predicted deformation characteristics of the fpBGA package. A good agreement was obtained between the simulated deformation results and experimental observations. For the durability analysis, the total fatigue life predicted using the energy-based method is larger than 2500 cycles—a trend observed experimentally for both packages entailing widely different designs. Based on proposed modeling and simulation results and package designs studied, the SBGA package is more durable than the fpBGA package.

Thermomechanical Durability of High I/O BGA Packages

Efficient modeling strategies are developed to study thermomechanical durability of high I/O Ball Grid Array (BGA) packages, in order to facilitate virtual qualification and accelerated testing of component designs. A viscoplastic stress analysis technique is developed where the critical solder joint(s) (joint(s) where failure first occurs) are modeled in detail with a multi-domain Rayleigh-Ritz (MDRR) methodology while the load-sharing offered by noncritical joints is modeled with a simplified compact model. This hybrid technique is used to study the behavior of solder interconnects in selected Ball Grid Array (BGA) package under thermal cycling environments. Parametric studies are conducted to determine the optimal scheme for allocating a critical number of solder joints to the MDRR model, and the remaining non-critical joints to the compact models. Damage calculations are made with the Energy Partitioning Solder Durability model and cycles-to-failure predictions are compared with both finite element model predictions as well as experimental failure data provided by CALCE EPSC sponsors. Parametric studies on change in solder joint durability with interconnect volume are also discussed in this paper.

Thermomechanical Durability Analysis of Flip Chip Solder Interconnects: Part 2—With Underfill

The effect of underfill material on reliability of flip chip on board (FCOB) assemblies is investigated in this study by using two-dimensional and three-dimensional finite element simulations under thermal cycling stresses from −55°C to 80°C. Accelerated testing of FCOB conducted by the authors reveals that the presence of underfill can increase the fatigue durability of solder interconnects by two orders of magnitude. Similar data has been extensively reported in the literature. It is the intent of this paper to develop a generic and fundamental predictive model that explains this trend. While empirical models have been reported by other investigators based on experimental data, the main drawback is that many of these empirical models are not truly predictive, and can not be applied to different flip chip architectures using different underfills. In the proposed model, the energy-partitioning (EP) damage model is enhanced in order to capture the underlying mechanisms so that a predictive capability can be developed. A two-dimensional finite element model is developed for stress analysis. This model accounts for underfill over regions of solder in an approximate manner by using overlay elements, and is calibrated using a three-dimensional finite element model. The model constant for the enhanced EP model is derived by fitting model predictions (combination of two-dimensional and three-dimensional model results) to experimental results for a given temperature history. The accuracy of the enhanced EP model is then verified for a different loading profile. The modeling not only reveals the influence of underfill material on solder joint durability, but also provides the acceleration factor to assess durability under life cycle environment, from accelerated test results. Experimental results are used to validate the trends predicted by the analytical model. The final goal is to define the optimum design and process parameters of the underfill material in FCOB assemblies in order to extend the fatigue endurance of the solder joints under cyclic thermal loading environments.

Bus Bar Solder Joint Durability Evaluation

Thermostructural analyses were conducted in support of an investigation into bus bar solder joint reliability for military aircraft. In electronics packaging applications, the most common cause of solder joint failure is repeated straining during temperature cycling as a result of mismatch of the coefficients of thermal expansion (CTE) of the solder joint assembly. To ensure that the bus bar solder joints for military aircraft have sufficient reliability to withstand the environmental exposures, a thermostructural evaluation becomes necessary. To analyze the durability of bus bar solder joints, nonlinear finite element analyses were conducted with the ABAQUS computer code. In the analysis, the solder constitutive relation was incorporated into the ABAQUS code to calculate the nonlinear strains of the solder joints during temperature cycling. These nonlinear strains, combined with modified Manson-Coffin fatigue life prediction theory and Miner’s cumulative damage law, were then used to predict the cumulative damage index (CDI) of the solder joints for two thermal cycling life times. The CDI was also estimated for the case where cracks have initiated and propagated through about half the length of the solder joint. All analysis results indicate that these solder joints have sufficient structural margins to survive two thermal cycling life times.