Fatigue Life Of Solder Joints Research Articles

Thermo-Mechanical Design and Validation of Spaceborne High-Speed Digital Receiver Unit for Synthetic Aperture Radar Application

This paper presents the effectiveness of the thermo-mechanical design of a high-speed digital receiver unit (HSDRU) developed for spaceborne synthetic aperture radar applications. The main features of HSDRU’s thermo-mechanical design include the thermal management of high-heat dissipation units by adopting heat sinks with the additional function of structural stiffeners and securing the heat rejection path to the upper side of electronics that interfaces the foil radiator for the on-orbit passive thermal control of electronics exposed to deep space environments. The thermal design, which adopts a thermal gap pad, is closely related to the solder joint fatigue life in a launch vibration environment, owing to its initial compressive static load between the heat sink and heat dissipation units that enhances the heat transfer capability. The effectiveness of the design was validated via the qualification level of launch environment tests.

New Version of High-Damping PCB with Multi-Layered Viscous Lamina

In a previous study, a high-damping printed circuit board (PCB) implemented by multilayered viscoelastic acrylic tapes was investigated to increase the fatigue life of solder joints of electronic packages by vibration attenuation in a random vibration environment. However, the main drawback of this concept is its inability to mount electronic parts on the PCB surface area occupied by interlaminated layers. For the efficient spatial accommodation of electronics, this paper proposes a new version of a high-damping PCB with multilayered viscoelastic tapes interlaminated on a thin metal stiffener spaced from a PCB. Compared to the previous study, this concept ensures efficient utilization of the PCB area for mounting electronic parts as well as the vibration attenuation capability. Free vibration tests were performed at various temperatures to obtain the basic characteristics of the proposed PCB. The effectiveness of the proposed PCB was verified by random vibration fatigue tests of sample PCBs with various numbers of viscoelastic layers to compare the fatigue life of electronic packages.

Effect of Ni3Sn4 on the Thermo-Mechanical Fatigue Life of Solder Joints in 3D IC

In this article, the 3D integration with Ni/Sn/Ni joints was conducted using transient liquid phase (TLP) bonding (250°C, 0.2 N) with different bonding time. After TLP bonding, plane-type Ni3Sn4 intermetallic compound (IMC) was observed, and when the bonding time is 180 min, complete Ni3Sn4 was found. The diffusion coefficient D was determined to be 32.4 μm2/min. Based on the finite element (FE) simulation, the results demonstrated that the shear stress and equivalent creep strain increased obviously with an increase in the IMC thickness; the results calculated show that the IMC thickness impacts the fatigue life of solder joints significantly, and the fatigue life decreases notably with an increase in the Ni3Sn4 thickness.

Thermal Fatigue Life Prediction of BGA Solder Joints Using a Creep Constitutive Equation Incorporating Microstructural Coarsening Effect

A thermal fatigue life prediction method is proposed for Sn–Ag–Cu solder joints that incorporates the effect of creep strength reduction due to microstructural coarsening of the solder during thermal cycling. The proposed method was used to predict the thermal fatigue life of solder joints in a BGA (ball grid array) semiconductor package. In the study, the thermal fatigue life was calculated through as follows. A creep constitutive equation for the solder that incorporates the strain-enhanced growth of the intermetallic compounds in the solder was used to update the constitutive equation at each given cycle and the relationship between inelastic strain energy density range and the number of cycles of the solder joint was obtained to calculate the fatigue life. As the number of thermal cycles increased, the intermetallic compounds grew, and in conjunction with this, the inelastic strain energy density range increased, causing the thermal fatigue life of the solder joint to decrease compared with that without the microstructural coarsening effect. Since the growth of intermetallic compounds under field conditions with a long dwell time is large compared with that during accelerated tests, the decrease in thermal fatigue life due to microstructural coarsening was found to be significant under field conditions with a long dwell time.

Impact of inter-metallic compound thickness on thermo-mechanical reliability of solder joints in solar cell assembly

This study evaluates the impact of intermetallic compound (IMC) thickness on thermo-mechanical reliability of lead-free SnAgCu solder joints in crystalline silicon solar cell assembly with regard to fatigue life. Finite element modelling is used to simulate the non-linear thermo-mechanical deformation of the joints. Five geometric models of solar cell assemblies with different IMC thickness layers in the range of 1 to 4 μm are utilized. The models were subjected to accelerated thermal cycling from 40 °C to 85 °C employing IEC 61215 standard for photovoltaic panels. Creep response of each of the assembly's solder joints to the induced thermal load were simulated using Garofalo-Arrhenius creep model. Simulation results indicate that when IMC thickness grows incrementally to 1, 2, 2.5, 3 and 4 μm, thermo-mechanical fatigue life of solder joints diminishes to 13,800, 11,800, 10,600, 9400 and 7800 cycles to failure respectively. Thus, solder joint fatigue life decreases as the IMC thickness increases during service lifetime. Therefore, proper design of solder joint in crystalline silicon solar cell assembly must include consideration of IMC layer thickness to prevent premature failure and to ensure fulfilment of desired functional lifetime of 13,688 cycles to failure (25 years).

Properties and microstructure evolution of Sn–Cu–Ni/Cu joints bearing carbon nanotubes and graphene nanosheets for solar cell

In this paper, 0.5 wt% carbon nanotubes (CNTs) and 0.05 wt% graphene nanosheets (GNSs) were selected as additives to modify the properties of Sn–Cu–Ni solder joints for solar cell. The mechanical properties of Sn–Cu–Ni solder joints can be improved by 20–25%. The interface growth behavior of Cu–Sn intermetallic compounds at Sn–Cu–Ni/Cu and Sn–Cu–Ni–0.5CNTs–0.05GNSs/Cu couples after 250 °C and 260 °C soldering with 10 min and 20 min. The experimental results indicate that the growth rate of Cu6Sn5 IMC of Sn–Cu–Ni/Cu solder joints is higher than that of Sn–Cu–Ni–0.5CNTs–0.05GNSs/Cu solder joints. That is, adding 0.5 wt% CNTs and 0.05 wt% GNSs can reduce the growth rate of the Cu6Sn5 IMC layer, which can be attributed to the reduction of the element diffusion coefficient. In addition, the stress–strain of the two solder joints were calculated using finite element method, it is found that the Sn–Cu–Ni–0.5CNTs–0.05GNSs/Cu solder joints have significantly less stress–strain than Sn–Cu–Ni/Cu solder joints, due to the reduction of Cu6Sn5 layer thickness, fatigue life of solder joints can be enhanced by three times.

Fatigue Life of Sn3.0Ag0.5Cu Solder Alloy Under Combined Cyclic Shear and Constant Tensile/Compressive Loads

Abstract Solder joints in electronic assemblies experience damage due to cyclic thermomechanical loading that eventually leads to fatigue fracture and electrical failure. While solder joints in smaller, die-sized area-array packages largely experience shear fatigue due to thermal expansion mismatch between the component and the substrate, larger area-array packages experience a combination of cyclic shear and axial tensile/compressive loads due to flexure of the substrate. Additionally, on larger processor packages, the attachment of heatsinks further exacerbates the imposed axial loads, as does package warpage. With the increase in size of packages due to 2.5D heterogeneous integration, the above additional axial loads can be significant. Thus, there exists a critical need to understand the impact on fatigue life of solder joints with superposed compressive/tensile loads on the cyclic shear loads. In this paper, we describe a carefully constructed multi-axial microprecision mechanical tester as well as fatigue test results on Sn3.0Ag0.5Cu (SAC305) solder joints subjected to controlled cyclic shear and constant compressive/tensile loads. The tester design allows one to apply cyclic shear loads up to 200 N while maintaining a constant axial load of up to 38 N in tension or compression. The tester is capable of maintaining the axial load to within a tolerance of ±0.5 N during the entirety of fatigue experiment. Carefully constructed test specimens of Sn3.0Ag0.5Cu solder joints were isothermally fatigued under systematically increased compressive and tensile loads imposed on the test specimen subject to repeated loading (R = 0) under lap-shear. In general, the imposition of the superposed compressive load increases the fatigue life of the solder joint compared to application of pure cyclic shear, while the imposition of the superposed tensile load decreases the fatigue life. At larger compressive loads, friction between fractured surfaces is responsible for significant energy dissipation during the cyclic load–unload cycles.

Fatigue Life Degradation Modeling of SnAgCu Solder Joints After Aging

The reliability of electronic assemblies is exceedingly reliant on the life of solder joints. Many factors may influence the fatigue life and mechanical properties of solder joints. Aging is one of the main factors that adversely affect the reliability of solder joints. In this article, the mechanical reliability of individual SnAgCu solder joints is studied at different aging conditions. The experiments include aging then cycling solder joints in stress-controlled shear fatigue at different stress amplitudes (16, 20, and 24 MPa) until complete failure. The aging conditions include three levels of aging temperatures (50 °C, 100 °C, and 150 °C) and four levels of aging time (2, 10, 100, and 1000 h). The effect of stress amplitude, aging time, and aging temperature on the fatigue life is investigated. The evolutions in the hysteresis loop, including the inelastic work dissipation, are explored by studying the stress–strain diagrams. The results showed that the fatigue life was affected by the stress amplitude, where increasing the stress by a factor of 2 leads to life reduction by a factor of 22. It was also found that increasing the aging time leads to nonlinear life reduction, where the first few hours of aging had the largest effect. Increasing the aging temperatures aggregates the aging time effect and leads to less fatigue resistance. Overall, increasing the aging time, temperature, and/or stress amplitudes leads to an increase in the work dissipation per cycle, which creates more damage and leads to less number of cycles to failure. The effect of these factors was fit into mathematical equations. Then, a general reliability model as a function of those parameters was developed.

Experimental and finite element analysis on determining the fatigue life of pb-free solder joint (Sn-0.5Cu-3Bi-1Ag) used in electronic packages under harmonic loads

Electronic packages that are used these days are exposed to different types of vibration loadings in their usage environment. This vibration exposure can be categorized as harmonic and random vibrations. When reliability assessment of modern electronic systems is considered, vibration loading has an important role to play. One of the biggest challenges facing today is the accurate and rapid assessment of fatigue life under the vibration loading. Conventional solder joints were made of lead-tin alloy. According to many environment legislations and rules, lead is prohibited as an ingredient in the solder alloy. The reason for the prohibition of the usage of the lead is that it poisons the environment. In this study, Sn-0.5Cu-3Bi-1Ag is used as the lead-free solder alloy. Fatigue life prediction of electronic package containing SAC405 is conducted with the aid of vibration testing and Finite element analysis under harmonic vibration loading. A specially designed Plastic Ball Grid Array Package (PBGA) component is mounted on Printed Circuit Board (PCB). It is taken as a test vehicle for the vibration test. The test vehicle is excited by a sinusoidal vibration. The frequency of this excitation equals the fundamental frequency of the test vehicle and it is continued till the component fails. Since the solder balls are very small for direct measurement, Finite Element analysis (FEA) is used for noting down the stresses. The stress versus failures cycles (S-N) curve is made by relating both the stresses on the solder balls obtained and the number of failure cycles from vibration analysis. The fatigue life of the component can be estimated from the generated S-N curve. It is analyzed that the methodology is effective in predicting the component’s life. Hence, the reliability of electronic package can be improved.

Modeling and experimentation of creep-fatigue and failure of low-profile quad flat package under thermal cycle

An experimental investigation and numerical modeling using multiphysics finite element method were performed to study the thermal failure mechanism of low-profile quad flat package solder joints of memory module due to low-cycle fatigue. The strain, stress, and number of cycles to failure have been calculated according to a strain life Coffin–Manson and energy-based Morrow fatigue models. Scanning electron microscopy imaging at the end of thermal cycle was used to evaluate the damage initiation and propagation. The effect of the solder volume on fatigue life of solder joints was discussed. Through analyses of theoretical results and experimental data on fatigue life, cracks initiation and propagation have been highlighted and their possible causes have been discussed.

Energy based modeling for temperature cycling induced tin silver copper solder interconnect fatigue life

Lead free (LF) solders such as tin silver copper (SAC) and its variations have been used in microelectronic products for the past decade due the Restriction of Hazardous Substances regulation. In use, temperature cycling is a major contributor to the wear-out failure mechanisms of solder joints during the life span of electronics. To predict the reliability of electronic solder joints, a fatigue life model is needed. Currently, strain energy density based models are widely used for solder joint fatigue life estimation. This paper reviews existing LF solder fatigue life models and provides strain energy based life model constants for a variety of LF solder materials.

Thermal Fatigue Modelling and Simulation of Flip Chip Component Solder Joints under Cyclic Thermal Loading

Thermal Fatigue of flip chip component solder joints is widely existing in thermal energy systems, which imposes a great challenge to operational safety. In order to investigate the influential factors, this paper develops a model to analyze thermal fatigue, based on the Darveaux energy method. Under cyclic thermal loading, a theoretical heat transfer and thermal stress model is developed for the flip chip components and the thermal fatigue lives of flip chip component solder joints are analyzed. The model based simulation results show the effects of environmental and power parameters on thermal fatigue life. It is indicated that under cyclic thermal loading, the solder joint with the shortest life in a package of flip chip components is located at the outer corner point of the array. Increment in either power density or ambient temperature or the decrease in either power conversion time or ambient pressure will result in short thermal fatigue lives of the key solder joints in the flip chip components. In addition, thermal fatigue life is more sensitive to power density and ambient temperature than to power conversion time and ambient air pressure.

A State-of-the-Art Review of Fatigue Life Prediction Models for Solder Joint

Fatigue failure of solder joints is one of the major causes of failure in electronic devices. Fatigue life prediction models of solder joints were first put forward in the early 1960s, and since then, numbers of methods were used to model the fatigue mechanism of solder joints. In this article, the majority fatigue life models are summarized, with emphasis on the latest developments in the fatigue life prediction methods. All the models reviewed are grouped into four categories based on the factors affecting the fatigue life of solder joints, which are: plastic strain-based fatigue models, creep damage-based fatigue models, energy-based fatigue models, and damage accumulation-based fatigue models. The models that do not fit any of the above categories are grouped into “other models.” Applications and potential limitations for those models are also discussed.

Thermal fatigue life of Sn–3.0Ag–0.5Cu solder joint under temperature cycling coupled with electric current

In this paper, the physical and mechanical properties of Sn–3.0Ag–0.5Cu (SAC305) solder and the thermal fatigue properties of solder joints under different electric current densities and heat sink temperatures are investigated. The thermal and electrical conductivities of the SAC305 specimens are measured for the electric current density between 6.37 × 102 A/cm2 and 2.55 × 103 A/cm2. Through comparisons against the experimental results, it is found that the prediction results of finite element simulations can reasonably characterize the mechanical properties of SAC305 solder materials. In order to evaluate the effect on mechanical behaviour of solder alloys, a typical solder joint of mechanical properties for the upper and lower bounds under thermo-electric coupling conditions are analyzed by finite element simulations. The original Coffin–Manson model is improved to predict the fatigue life of SAC305 solder joints under temperature cycling coupled with electric current. Comparisons show that the different mechanical behaviour of SAC305 solder materials results in different performances at varying electric current densities and heat sink temperatures. For low current densities and heat sink temperatures, the solder material with lower yielding and ultimate strengths has a higher fatigue life. On the contrary, at high current densities and heat sink temperatures, the solder material with higher yielding and ultimate strengths will exhibit advantages in terms of fatigue life. From the numerical simulation point of view, this study reveals the performance advantages of lead-free solders with higher yielding and ultimate strengths in terms of thermal fatigue and current density for high temperature and power applications.

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.

Finite Element Analysis for Reliability of Solder Joints Materials in the Embedded Package

This paper is about study on warpage, creep strain and the total strain energy density (TSED) effect on fatigue life of the solder joints in the embedded package under thermal cycling conditions by finite element method. In order to investigate the influence of material of solder joints in embedded package, four materials (SAC305, SnAgCu, Sn96.5Ag3.5, Pb97.5Sn2.5) of solder joints were used. Calculated results show that warpage of package was low, creep strain and TSED of solder joints were low in embedded package. Therefore the fatigue life of the solder joint in embedded package increases. Also, the fatigue life of solder joints of Sn96.5Ag3.5 would be highest among solder materials because of the lowest of TSED.

Influence of Directional Random Vibration on the Fatigue Life of Solder Joints in a Power Module

In this paper, fatigue life of solder joints of the power module and the printed circuit board in a power inverter under directional random vibration using the finite element method (FEM) was evaluated. Five angles of 0°, 30°, 45°, 60°, and 90° were selected for direction of vibration loading. The simulation results showed that the outermost corner of the solder layer undergoes the maximum stress during the vibration frequencies in all the situations. In general, with the increase of input frequency, the solder joints got more susceptible to the catastrophic failure. Moreover, it was found that in lower angles of loading direction, the peeling stress is dramatically increased in the solder layer. This event can be attributed to the considerable portion of shear stress in loading directions with lower angles. The experimental results also proved the FEM simulation and showed that the void growth and coalescence, resulted by fatigue, are intensified in the lower angles of vibration loading. Overall, this paper indicates that the reliability of a power module under a normal loading (90°) is the highest among all other conditions.

Prediction of Fatigue Life of solder joints on Field winding

Prediction of Fatigue Life of solder joints on Field winding

Multi-scale Finite Element Analysis into Fatigue Lives of Various Component Solder Joints on Printed Circuit Board

Multi-scale Finite Element Analysis into Fatigue Lives of Various Component Solder Joints on Printed Circuit Board

Improving the reliability of ball grid arrays under random vibration by optimization of module design

In this work, three different arrangements of circuit board in an electronic device were designed and the effects of random vibration frequencies on the reliability of ball grid arrays (BGA) in these arrangements were evaluated. The failure criterion in solder balls was the root mean square of peeling stress exerted during the dynamical loadings. According to the finite element method (FEM) results, the uttermost stress concentration was generated at the interface of printed circuit board (PCB) and the solder balls. It was also revealed that the increase of input power spectral density (PSD) decreased the fatigue life of solder joint in all the arrangements. Considering the arrangements of circuit boards, it was found that the maximum domain of peeling stress had a minimum effect on the solder balls when the heat sinks were away from the packages. The microstructural characterization of critical zone in solder balls indicated that with the increase of maximum peeling stress, the crack initiated and propagated along the interface.