Fatigue Life Of Solder Joints Research Articles

Anand model and FEM analysis of SnAgCuZn lead-free solder joints in wafer level chip scale packaging devices

In this paper, the constitutive response of SnAgCuZn solder was studied under uniaxial tension. Anand model was used to represent the inelastic deformation behavior of the lead-free solders. The material parameters of the constitutive relations for SnAgCuZn solders were determined from separated constitutive relations and experimental results. In addition, the constitutive model was used to analyze the thermally induced inelastic deformation of the solder joints in wafer-level chip scale packages mounted on printed circuit boards based on finite element analysis. And it is found that the addition of Zn can enhance the fatigue life of SnAgCu solder joint.

Extending the fatigue life of Pb-free SAC solder joints under thermal cycling

This paper reports on the dependence of the thermal fatigue life of Pb-free solder (Sn–3.0Ag–0.5Cu) joints on the points at which the printed circuit board (PCB) is fixed to a rigid support. Elastic–plastic finite element analysis under various thermal cycling conditions was performed. For the analysis, the mechanical boundary conditions around a solder joint bonded silicon chip were varied by changing the points at which the PCB was attached to its support. From the results of the analysis, it was found that the accumulated strain in the solder joints decreased when the PCB was fixed at points placed diagonally with respect to the silicon chip. The thermal fatigue life could therefore be expected to be extended by the choice of fixing points. Using a special support with a thermal expansion coefficient of less than 1.5×10−6K−1, we demonstrated, experimentally, that the accumulated strain and the failure site of the solder joints could indeed be controlled by the positions at which the printed circuit board was fixed.

Fatigue Reliability Analysis of Sn–Ag–Cu Solder Joints Subject to Thermal Cycling

In this paper, thermal cycling tests and finite-element analysis (FEA) for a plastic ball grid array package with Sn-3.8Ag-0.7Cu lead-free solder joints have been performed. The solder joint fatigue lives were predicted and compared by using different 2-D and 3-D FEA models. The effects of solder constitutive models and fatigue life models on solder fatigue life prediction have been investigated. In order to obtain fatigue parameters, new averaging volumes were proposed for the solder fatigue life prediction. Different reference temperatures were simulated to investigate its effect on the solder fatigue life prediction. The effect of intermetallic compound thickness on solder joint fatigue life prediction was also investigated.

Design for Solder Joint Fatigue Life of BGA Package Subject to Mechanical Environment

There has been a dramatic proliferation of research concerned with thermal stress in electronic package for the last three decades. Moreover, reviewing the mechanical bending during printed circuit board (PCB) assembly has become important in the reliability assessment of modern electronic systems. The primary research demonstrates that the assessment approach can be applied successfully to the design model of a ball grid array (BGA) package with a more complete and accurate assessment model for solder joint fatigue life under mechanical bending. Previous research has focused mostly on the thermal analysis in electronic packages; however, most modern portable electronic products used in mobile devices, personal digital assistants, and aircraft have to endure extreme environments that involve not only thermal but also mechanical bending conditions. Initially, mechanical bending tests were conducted to demonstrate the reliability of the electronic packaging during the manufacturing and shipping process. Currently, the microelectronic packaging faces mechanical bending when everyone uses his or her Smartphones. The mechanical bending occurs when the user touches the screen on the Smartphone. Therefore, interest in the mechanical bending of BGA packaging has increased with the uptake in mobile device use. In this research, the analytical solution and finite element analysis (FEA) are both presented to investigate the solder joint fatigue life. The analytical solution is presented for a PCB assembly subjected to mechanical bending by taking the axial stress, shear stress, and moment of the solder joints with discontinuity function into account. A FEM is proposed to analyze the solder joint fatigue life and to investigate the reliability of solder joints in BGA packaging subjected to mechanical bending.

Thermal Cycle Consideration in Applying Lead-Free TFBGA Simulation to a Design

Three-dimensional (3D) stacked die packaging has become the trend to improve efficiency for transmitting signals, reduce the volume of the package, and help with functions integration. It is more and more applied popularly in telecommunications. Solder joints, interconnections in the packaging structure, are more easily damaged by critical stress from thermal cycle loading when the component is operating, because the coefficient of the thermal expansion of various materials mismatch. People have studied the common single die during the thermal cycle loading for a long time, but the researches for the stacked die BGA are not as complete. In addition, to protect the environment and comply with legislation, the semiconductor industry wants to find a lead-free material to replace the lead solder joints. Therefore, most extant or new types of packaging started using lead-free material to do thermal cycle testing. The critical solder ball location is not the same as in a single die package where at the die corner, due to it is influenced by stacked die with different geometry, the difference in dice length helps to redistribute the die stress. In this paper, we used FEA software, ANSYS, to build up a 3D thin-profile, fine-pitch, ball grid array (TFBGA) model. The modeling investigated the effect on solder joints under thermal cycle and included deformation, von-Mises stress and strain energy density (SED). Then we utilized Darveaux's approach, which is a common methodology used to calculate the fatigue life based on energy and damage accumulation theories, to predict the fatigue life of the critical solder joint and modify our model with the theory. We changed various kinds of SAC solder joints with different ratios of the components and Anand's constants, analyze the divergence and compared them with the lead solder material. We develop a model to forecast the failure phenomenon and fatigue damage on an electronic package. This would help engineers and designers raise the reliability of the package. In addition, we hope to find a lead-free material that can be substituted for the lead solder material. If this is the case, based on simulating results, we hope to improve it and have much a better reliability performance than the original lead solder.

High-temperature fatigue life of flip chip lead-free solder joints at varying component stand-off height

The recent uses of microelectronics as sensors or control devices at high-temperature ambient increase the rate of visco-plastic degradation of solder joints of their components. The response of solder bumped joints to the induced thermal load culminates in plastic strain which over many cycles may accumulate damage in the joints, subsequently leading to their fatigue failures. Finite element modelling is employed to investigate the impact of static structural factors of flip chip (FC) assembly on its solder joint damage at high-temperature excursions. This paper discusses results of a modelling study focused on effects of component stand-off height (CSH) and intermetallic compound (IMC) on static structural integrity of lead-free solder joints in a flip chip FC48D6.3C457 package which is cycled between −38°C and 157°C temperatures. The result analysis is based on accumulation of damage indicators such as stress, strain and plastic work density in the solder joints. The accumulated damage was used to predict the thermo-fatigue life of different architectures of the FC assembly. It was found that the fatigue life of the joint assemblies decrease exponentially as the component stand-off height decreases in a cubic function. Based on our research results, it is proposed that the size of diameter of bond pad defined by solder mask on printed circuit board (PCB) should not exceed 110% of the size of diameter of bond pad at the chip side.

A crack initiation and propagation simulation and the fatigue characteristics of solder joints considering the material property changes

The re-working of the manufacturing process from the reliability evaluation after the production process is a significant cost and loss of energy. In-vehicle electronic devices are exposed to multiple environmental loads such as thermal and vibrational loads. The effects of the material property changes in the thermal cycle load on the fatigue life of solder joints were estimated with our fatigue simulation for the purpose of constructing a design method considering the fatigue characteristic changes in the thermal cycle. The fatigue lives were estimated with and without considering the creep property changes measured by indentation tests. The fatigue ductility index and the coefficients increased toward the reported values by considering the creep property changes.

Impact of Isothermal Aging and Sn Grain Orientation on the Long-Term Reliability of Wafer-Level Chip-Scale Package Sn–Ag–Cu Solder Interconnects

The interaction between isothermal aging and the long-term reliability of wafer-level chip-scale packages with Sn-3.0Ag-0.5Cu (wt%) solder ball interconnects is investigated. On isothermally aging at 100 and 150°C for 500 h and then thermally cycling from 0 to 100°C with 10 min of dwell time, the lifetime of the package is reduced by approximately 29%, depending on the aging condition. The microstructural evolution is observed during thermal aging and thermal cycling using orientation image microscopy. A Sn grain orientation structure transformation is observed. Different mechanisms after aging at various conditions are identified, and their impacts on the fatigue life of solder joints discussed.

F603 インバータ基板のはんだ接合部の熱疲労寿命の評価 : 応力特異性パラメータを用いた評価(F6.企業におけるCAE活用,フォーラム)

It is well known that thermal fatigue easily occurs in the solder joints of inverter circuit board. In this study, we tried to evaluate thermal fatigue life of solder joints with the stress singularity parameters near the solder joint edges. Firstly, we made constitutive equations of the solder materials and confirmed its precision. Next, using FEM analyses, we calculated stress singularity parameters near the solder joint edges for power modules under the conditions of thermal cycle experiments and power cycle experiments. Finally, we made evaluation equations of thermal fatigue life for solder joints by connecting stress singularity parameters and experiment results with fatigue laws.

High temperature reliability of lead-free solder joints in a flip chip assembly

The visco-plastic behaviour of solder joints of two models of a flip chip FC48D6.3C457DC mounted on a printed circuit board (PCB) via SnAgCu solder is investigated using Anand's model. While the bumps of one of the models are realistic with 6 μm thickness of intermetallic compound (IMC) at interconnects of solder and bond pads, the other are made up of conventional bumps without IMC at these interconnects. The solder bump profiles were created using a combination of analytical method and construction geometry. The assembled package on PCB was accelerated thermally cycled (ATC) using IEC standard 60749-25. It was found in the result of the simulation that IMC does not only impact solder joint reliability but also is a key factor of fatigue failure of solder joints. The IMC sandwiched between bond pad at chip side and solder bulk is the most critical and its interface with solder bulk is the most vulnerable site of damage. With reference to our results, it is proposed that non inclusion of IMC in solder joint models composed of Sn-based solder and metalized copper substrate is one of the major causes of the discrepancy on solder joint fatigue life predicted using finite element modelling and the one obtained through experimental investigation.

Comparison of results from empirical ALT test to CAE simulation for wireless clients

PurposeThe purpose of this paper is to investigate how to reduce the time and cost required to conduct reliability testing. With increasing competition in the electronics industry and reduction in product life cycles, it is essential to diminish the time required for new product development and thus time to market.Design/methodology/approachThis study conducts empirical sample test for wireless card and analyzes the fatigue life through finite element modeling (FEM). Simulation results are compared to the data collected from a temperature cycling test under conditions of −40°C to 150°C and −40°C to 100°C.FindingsAssuming that the results of product lifetime from empirical sample test and software simulation exhibit a linear relationship, a “scale factor” should exist for any given product structure, process condition and materials composition scenario. The scale factors were found to be approximately 0.1 in both temperature cycling scenarios. Also, the effectiveness of various adhesive dispensing patterns on solder joint reliability is evaluated through software simulation. The L shape adhesive dispensing was proven to effectively enhance the fatigue life of chip scale package solder joints roughly 100‐fold.Originality/valueThe scale factor is used to convert the results from software simulation to empirical sample test for a given set of processing environments and materials. This helps to reduce the time and cost required to conduct reliability testing.

Finite element based fatigue life estimation of the solder joints with effect of intermetallic compound growth

This paper develops an analysis procedure to study the effects of intermetallic compound (IMC) growth on the fatigue life of 63Sn–37Pb (lead-rich)/96.5Sn–3.5Ag (lead-free) solder balls for flip-chip plastic ball grid array packages under thermal cycling test conditions. In this analysis procedure, the thickness of the IMC increased with the number of thermal cycles, and was determined using the growth rate equation. A series of non-linear finite element analyses was conducted to simulate the stress/strain history at the critical locations of the solder balls with various IMC thicknesses in thermal cycling tests. The simulated stress/strain results were then employed in a fatigue life prediction model to determine the relationship between the predicted fatigue life of the solder ball and the IMC thickness. Based on the concept of continuous damage accumulation and incorporated with the linear damage rule, this study defines the damage of each thermal cycle as the reciprocal of the predicted fatigue life of the solder joints with the corresponding IMC thickness. The final fatigue failure of the solder ball was determined as the number of cycles corresponding to the cumulative damage equal to unity. Results show that the solder joint fatigue life decreased as the IMC thickness increased. Moreover, the predicted thermal fatigue life of lead-rich solders based on the effects of IMC growth is apparently smaller than that without considering the IMC growth in the reliability analysis. Results also show that the influence of the IMC thickness on the fatigue life prediction of the lead-free solder joint can be ignored.

Application of Finite Element Method in Optimal Design of Flip-Chip Package

More and more solder joints in circuit boards and electronic products are changing to lead free solder, placing an emphasis on lead free solder joint reliability. Solder joint fatigue failure is a serious reliability concern in area array technologies. In this study, the effects of substrate materials on the solder joint thermal fatigue life were investigated by finite element model. Accelerated temperature cycling loading was imposed to evaluate the reliability of solder joints. The thermal strain/stress in solder joints of flip chip assemblies with different substrates was compared, and the fatigue life of solder joints were evaluated by Darveaux’s crack initiation and growth model. The results show the mechanisms of substrate flexibility on improving solder joint thermal fatigue.

Solder Joint Reliability of SnAgCu Solder Refinished Components Under Temperature Cycling Test

SnAgCu (SAC) solder is being offered as a lead-free termination finish. SAC finish is obtained by dipping the terminals of components into molten SAC solder. However, the reliability of solder joints formed with SAC solder refinished components needs to be determined in order to evaluate the effects of the SAC solder refinishing process. In this paper, the strength of solder joints with SAC solder refinished thin small outline packages (TSOPs) was evaluated by the shear test. The reliability of solder joints formed with SAC solder refinished components, including TSOPs and resistors, was evaluated by a temperature cycling test. Original Sn finished components were used as a baseline for comparison. It was found that SAC solder refinishing increased solder joint strength. SAC solder refinishing decreased the fatigue life of solder joints of TSOPs and increased the fatigue life of resistors under temperature cycling conditions.

Temperature cycling analysis for ball grid array package using finite element analysis

PurposeThe purpose of this paper is to discuss the capability of finite element analysis (FEA) in performing the virtual thermal cycling reliability test to evaluate the reliability of solder joints in a ball grid array (BGA) package.Design/methodology/approachThermal cycling test has been used to evaluate the reliability or fatigue life of the solder joints in BGA package using commercially available FEA software, ANSYS™. The effect of different temperature cycling condition is studied by applying different value of dwell time and ramp rate. Two types of analyses are used namely, the physics‐based analysis and the statistical‐based analysis. Two screening design methods namely, central composite design (CCD) and Box‐Behnken Matrix Design method are used to isolate the most important factors amongst six selected design variables. The optimization process is carried out using response surface methodology (RSM).FindingsIt is observed that changes in ramp rate produce significant effect in solder fatigue life than changes in dwell time but the dwell time at high temperature has a negligible contribution to solder fatigue life. It has been found that the thickness of the mold has a significant effect on the performance of the solder joint reliability (more than 50 percent) as compared to that from other factors. Besides, the effect of individual factor, the interaction among factors also changes the solder joint reliability. RSM based on Box‐Behnken Matrix design offers the highest characteristic solder joint fatigue life with a value of 2,861 cycles.Originality/valueThis paper provides a comprehensive method to evaluate the reliability of solder joints in terms of physics and statistical‐based analysis.

J031031 高温劣化を考慮したSn3AgO.5Cuはんだ接合部の疲労寿命予測手法([J03103]電子情報機器,電子デバイスの強度・信頼性評価と熱制御(3))

The decrease in fatigue life of solder joints under the high-temperature environment is a critical issue in semiconductor packages for automotive applications. To evaluate the deterioration of solder joints under high temperature, we studied the analytical method considering the decrease in yield-stress due to the grain coarsening of solder. We found that the decrease in yield stress largely depends on the exposed temperature and the holding time by using the Sn3Ag0.5Cu solder specimen. The decreasing ratio of yield stress was determined by the degradation factor and the accumulative holding time. The predicted fatigue life of solder joints using FEM considering the decrease in yield stress agreed well with the results of thermal cycle test.

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.

Analysis of Stress-Strain Hysteresis Loop and Prediction of Thermal Fatigue Life for Chip Size Package Solder Joints

The aim of this study is to investigate the relationship between the inelastic strain range and the thermal fatigue lives of chip size package solder joints with Sn-Pb and Sn-Ag-Cu solder balls. The inelastic strain range was examined by finite element analysis. In both solder joints, the exponential terms in the inelastic strain range term in the Coffin-Manson equation were evaluated as 1.8 - 2.3. These values are very close to the conventional one used in Sn-Pb and the Pb containing solders. The inelastic strain range is almost proportional to the temperature range in the Sn-Pb solder joint. On the contrary, the inelastic strain range is proportional to approximately the square root of the temperature range in the Sn-Ag-Cu solder joint. The deference depends on the change of the stress-strain hysteresis curve in the thermal cycle.

Application of Viscoplastic-Creep Separate Constitutive Model to Lead-Free Solder Alloy

When we estimate the fatigue life of lead-free solder joints, we have to conduct FE analysis using a constitutive model which can exhibit mechanical properties of lead-free solder. In FE analysis of solder joints under cyclic temperature load, a constitutive model has to express stress strain curves, stress strain hysteresis loops and stress relaxation curves accurately, containing these temperature dependencies and these rate dependencies. In this study, we proposed a separate type viscoplastic-creep constitutive model which can describe stress strain curves, stress strain hysteresis loops and stress relaxation curves, with these temperature dependencies and these rate dependencies. We implemented the proposed model into finite element analysis code ABAQUS. We conducted tensile tests, tension-compression tests and tension-stress relaxation tests of Sn3.5Ag0.5Cu0.07Ni0.01Ge solder and determined material parameters of the proposed model from tensile test data and tension-compression test data. Then, we analyzed the conducted material tests using the proposed model and compared FE analysis results with experimental test data to examine the validity of the proposed model. It was confirmed that analytical results were in good agreements with the experimental ones.

Laser moiré interferometry for fatigue life prediction of lead-free solders

A laser moiré interferometry based technique to predict the fatigue life of Sn4.0Ag0.5Cu solder joints in a plastic ball grid array (PBGA) package when subjected to a typical accelerated thermal cycling (ATC) loading has been presented in this paper. The fatigue life is estimated by measuring the in-plane strains in the solder joints at various temperatures. The methodology can be used to predict the reliability of the package in a matter of few days as opposed to many months taken by an actual ATC test. The technique can be extended to include multiple temperature regimes in a single experimental setup thereby making it possible to estimate the fatigue life of solder joints when subjected to various ATC loading profiles in a very short duration.