A comprehensive review of radiation effects on solder alloys and solder joints

In the realm of military and defence applications, exposure to radiation significantly challenges the performance and reliability of solder alloys and joints in electronic systems. This comprehensive review examines radiation-induced effects on solder alloys and solder joints in terms of microstructure and mechanical properties. In this paper, we evaluate the existing literature, including experimental studies and fundamental theory, to provide a comprehensive overview of the behavior of solder materials under radiation. A review of the literature highlights key mechanisms that contribute to radiation-induced changes in the microstructure, such as the formation of intermetallic compounds, grain growth,micro-voids and micro-cracks. Radiation is explored as a factor influencing solder alloy hardness,strength, fatigue and ductility. Moreover, the review addresses the challenges and limitations inherent in studying the effects of radiation on solder materials and offers recommendations for future research. It is crucial to understand radiation-induced effects on solder performance to design robust and radiationresistant electronic systems. A review of radiation effects on solder materials and their applications in electronics serves as a valuable resource for researchers, engineers, and practitioners in that field.

Drop failure modes of Sn-3.0Ag-0.5Cu solder joints in wafer level chip scale package

To reveal the drop failure modes of the wafer level chip scale packages （WLCSPs） with Sn-3.0Ag-0.5Cu solder joints, board level drop tests were performed according to the JEDEC standard. Six failure modes were identified, i.e., short FR-4 cracks and complete FR-4 cracks at the printing circuit board （PCB） side, split between redistribution layer （RDL） and Cu under bump metallization （UBM）, RDL fracture, bulk cracks and partial bulk and intermetallic compound （IMC） cracks at the chip side. For the outmost solder joints, complete FR-4 cracks tended to occur, due to large deformation of PCB and low strength of FR-4 dielectric layer. The formation of complete FR-4 cracks largely absorbed the impact energy, resulting in the absence of other failure modes. For the inner solder joints, the absorption of impact energy by the short FR-4 cracks was limited, resulting in other failure modes at the chip side.

Thermo-mechanical fatigue reliability optimization of PBGA solder joints based on ANN-PSO

Based on a method combined artificial neural network (ANN) with particle swarm optimization (PSO) algorithm, the thermo-mechanical fatigue reliability of plastic ball grid array (PBGA) solder joints was studied. The simulation experiments of accelerated thermal cycling test were performed by ANSYS software. Based on orthogonal array experiments, a back-propagation artificial neural network (BPNN) was used to establish the nonlinear multivariate relationship between thermo-mechanical fatigue reliability and control factors. Then, PSO was applied to obtaining the optimal levels of control factors by using the output of BPNN as the affinity measure. The results show that the control factors, such as print circuit board (PCB) size, PCB thickness, substrate size, substrate thickness, PCB coefficient of thermal expansion (CTE), substrate CTE, silicon die CTE, and solder joint CTE, have a great influence on thermo-mechanical fatigue reliability of PBGA solder joints. The ratio of signal to noise of ANN-PSO method is 51.77 dB and its error is 33.3% less than that of Taguchi method. Moreover, the running time of ANN-PSO method is only 2% of that of the BPNN. These conclusions are verified by the confirmative experiments.

QUICK ASSESSMENT METHODOLOGY FOR RELIABILITY OF SOLDER JOINTS IN BALL GRID ARRAY (BGA) ASSEMBLY——PART Ⅰ: CREEP CONSTITUTIVE RELATION AND FATIGUE MODEL

In this study, a new unified creep constitutive relation and a mod- ified energy-based fatigue model have been established respectively to describe the creep flow and predict the fatigue life of Sn-Pb solders. It is found that the relation successfully elucidates the creep mechanism related to current constitutive relations. The model can be used to describe the temperature and frequency dependent low cycle fatigue behavior of the solder. The relation and the model are further employed in part Ⅱ to develop the numerical simulation approach for the long-term reliability assessment of the plastic ball grid array (BGA) assembly.

Interfacial intermetallic compound growth and shear strength of low-silver SnAgCuBiNi/Cu lead-free solder joints

The growth rule of the interfacial intermetallic compound （IMC） and the degradation of shear strength of Sn-0.SAg-0.5Cu-2.0Bi-0.05Ni （SACBN）/Cu solder joints were investigated in comparison with Sn-3.0Ag-0.5Cu （SAC305）/ Cu solder joints aging at 373, 403, and 438 K. The results show that （Cul-x,Nix）6Sn5 phase forms between the SACBN solder and Cu substrate during soldering. The interracial IMC thickens constantly with the aging time increasing, and the higher the aging temperature, the faster the IMC layer grows. Compared with the SAC305/Cu couple, the SACBN/Cu couple exhibits a lower layer growth coefficient. The activation energies of IMC growth for SACBN/Cu and SAC305/Cu couples are 111.70 and 82.35 kJ/mol, respectively. In general, the shear strength of aged solder joints declines continuously. However, SACBN/Cu solder joints exhibit a better shear strength than SAC305/Cu solder joints.

Finite element simulation for mechanical response of surface mounted solder joints under different temperature cycling

Nonlinear finite element simulation for mechanical response of surface mounted solder joint under different temperature cycling was carried out. Seven sets of parameters were used in order to evaluate the influence of temperature cycling profile parameters. The results show that temperature cycling history has significant effect on the stress response of the solder joint. Based on the concept of relative damage stress proposed by the authors, it is found that enough high temperature holding time is necessary for designing the temperature cycling profile in accelerated thermal fatigue test.

Influence of Thermal Cycling on the Microstructure and Shear Strength of Sn3.5Ag0.75Cu and Sn63Pb37 Solder Joints on Au/Ni Metallization

The influence of thermal cycling on the microstructure and joint strength of Sn3.5Ag0.75Cu （SAC） and Sn63Pb37 （SnPb） solder joints was investigated. SAC and SnPb solder balls were soldered on 0.1 and 0.9 μm Au finished metallization, respectively. After 1000 thermal cycles between -40℃ and 125℃, a very thin intermetallic compound （IMC） layer containing Au, Sn, Ni, and Cu formed at the interface between SAC solder joints and underneath metallization with 0.1 μm Au finish, and （Au, Ni, Cu）Sn4 and a very thin AuSn-Ni-Cu IMC layer formed between SAC solder joints and underneath metallization with 0.9 μm Au finish. For SnPb solder joints with 0.1 μm Au finish, a thin （Ni, Cu, Au）3Sn4 IMC layer and a Pb-rich layer formed below and above the （Au, Ni）Sn4 IMC, respectively. Cu diffused through Ni layer and was involved into the IMC formation process. Similar interfacial microstructure was also found for SnPb solder joints with 0.9μm Au finish. The results of shear test show that the shear strength of SAC solder joints is consistently higher than that of SnPb eutectic solder joints during thermal cycling.

Plastic characterization and performance of SnAgCuBiNi/Cu lead-free BGA solder joints

Nanoindentation test is performed on study the plastic and creep properties of the Sn-Ag-Cu （SAC） lead-free ball grid array （ BGA ） solder joints. The dynamic hardness of two kinds of solder joints decreases with indentation depth increase. SACO705 BiNi/ Cu exhibits a higher ultimate dynamic hardness and a smaller indentation depth than SAC305/ Cu. Then the strain hardening phenomenon of SAC305/ Cu is more obvious compared to that of SACO705 BiNi/ Cu. The indentation creep of SACO705BiNi/ Cu solder joint is lower than that of SAC305/ Cu solder joint before and after thermal shock. The creep rate sensitive index of SACBiNi/Cu solder joint is lower than that of solder joint. SACO705BiNi/Cu solder joint is superior to SAC305/Cu solder joint in the anti-creep property. The plasticity of SACOTOSBiNi/Cu and SAC305/Cu solder joints are similar. Compared with SAC305 solder, the SACO705 BiNi solder pe^forms higher hardness and solder creep resistance and still maintains a good plasticity.

Mechanical strength analysis of SMT solder joints by finite element method

In this paper,the finite element calculation is applied to the analysis of stress inside the SMT solder joints.The effects of the solder joints'shape,the voids inside them and the quantity of solder on the mechanical strength of the SMT solder joints are analyzed and compared This is essential to the design of the SMT solder joints and soldering techniques.

VMMAO-YOLO:an ultra-lightweight and scale-aware detector for real-time defect detection of avionics thermistor wire solder joints

The quality of the exposed avionics solder joints has a significant impact on the stable operation of the inorbit spacecrafts.Nevertheless,the previously reported inspection methods for multi-scale solder joint defects generally suffer low accuracy and slow detection speed.Herein,a novel real-time detector VMMAO-YOLO is demonstrated based on variable multi-scale concurrency and multi-depth aggregation network(VMMANet)backbone and“one-stop”global information gather-distribute(OS-GD)module.Combined with infrared thermography technology,it can achieve fast and high-precision detection of both internal and external solder joint defects.Specifically,VMMANet is designed for efficient multi-scale feature extraction,which mainly comprises variable multi-scale feature concurrency(VMC)and multi-depth feature aggregation-alignment(MAA)modules.VMC can extract multi-scale features via multiple fix-sized and deformable convolutions,while MAA can aggregate and align multi-depth features on the same order for feature inference.This allows the low-level features with more spatial details to be transmitted in depth-wise,enabling the deeper network to selectively utilize the preceding inference information.The VMMANet replaces inefficient highdensity deep convolution by increasing the width of intermediate feature levels,leading to a salient decline in parameters.The OS-GD is developed for efficacious feature extraction,aggregation and distribution,further enhancing the global information gather and deployment capability of the network.On a self-made solder joint image data set,the VMMAOYOLO achieves a mean average precision mAP@0.5 of 91.6%,surpassing all the mainstream YOLO-series models.Moreover,the VMMAO-YOLO has a body size of merely 19.3 MB and a detection speed up to 119 frame per second,far superior to the prevalent YOLO-series detectors.

A review of extreme condition effects on solder joint reliability:Understanding failure mechanisms

Solder joint,crucial component in electronic systems,face significant challenges when exposed to extreme conditions during applications.The solder joint reliability involving microstructure and mechanical properties will be affected by extreme conditions.Understanding the behaviour of solder joints under extreme conditions is vital to determine the durability and reliability of solder joint.This review paper aims to comprehensively explore the underlying failure mechanism affecting solder joint reliability under extreme conditions.This study covers an in-depth analysis of effect extreme temperature,mechanical stress,and radiation conditions towards solder joint.Impact of each condition to the microstructure including solder matrix and intermetallic compound layer,and mechanical properties such as fatigue,shear strength,creep,and hardness was thoroughly discussed.The failure mechanisms were illustrated in graphical diagrams to ensure clarity and understanding.Furthermore,the paper highlighted mitigation strategies that enhancing solder joint reliability under challenging operating conditions.The findings offer valuable guidance for researchers,engineers,and practitioners involved in electronics,engineering,and related fields,fostering advancements in solder joint reliability and performance.

Industrial Fusion Cascade Detection of Solder Joint

With the remarkable advancements in machine vision research and its ever-expanding applications,scholars have increasingly focused on harnessing various vision methodologies within the industrial realm.Specifically,detecting vehicle floor welding points poses unique challenges,including high operational costs and limited portability in practical settings.To address these challenges,this paper innovatively integrates template matching and the Faster RCNN algorithm,presenting an industrial fusion cascaded solder joint detection algorithm that seamlessly blends template matching with deep learning techniques.This algorithm meticulously weights and fuses the optimized features of both methodologies,enhancing the overall detection capabilities.Furthermore,it introduces an optimized multi-scale and multi-template matching approach,leveraging a diverse array of templates and image pyramid algorithms to bolster the accuracy and resilience of object detection.By integrating deep learning algorithms with this multi-scale and multi-template matching strategy,the cascaded target matching algorithm effectively accurately identifies solder joint types and positions.A comprehensive welding point dataset,labeled by experts specifically for vehicle detection,was constructed based on images from authentic industrial environments to validate the algorithm’s performance.Experiments demonstrate the algorithm’s compelling performance in industrial scenarios,outperforming the single-template matching algorithm by 21.3%,the multi-scale and multitemplate matching algorithm by 3.4%,the Faster RCNN algorithm by 19.7%,and the YOLOv9 algorithm by 17.3%in terms of solder joint detection accuracy.This optimized algorithm exhibits remarkable robustness and portability,ideally suited for detecting solder joints across diverse vehicle workpieces.Notably,this study’s dataset and feature fusion approach can be a valuable resource for other algorithms seeking to enhance their solder joint detection capabilities.This work thus not only presents a novel and effective solution for industrial solder joint detection but lays the groundwork for future advancements in this critical area.

Research Progress on the Solder Joint Reliability of Electronics Using in Deep Space Exploration

The spacecraft for deep space exploration missions will face extreme environments,including cryogenic temperature,intense radiation,wide-range temperature variations and even the combination of conditions mentioned above.Harsh environments will lead to solder joints degradation or even failure,resulting in damage to onboard electronics.The research activities on high reliability solder joints using in extreme environments can not only reduce the use of onboard protection devices,but effectively improve the overall reliability of spacecraft,which is of great significance to the aviation industry.In this paper,we review the reliability research on SnPb solder alloys,Sn-based lead-free solder alloys and In-based solder alloys in extreme environments,and try to provide some suggestions for the follow-up studies,which focus on solder joint reliability under extreme environments.

EFFECTS OF LEAD WIDTHS AND PITCHES ON RELIABILITY OF QUAD FLAT PACKAGE(QFP)SOLDERED JOINTS

The finite element method（FEM） is used to analyze the effects of lead widths and pitches on reliability of soldered joints. The optimum simulation for QFP devices is also researched. The results indicate that when the lead pitches are the same, the maximum equivalent stress of the soldered joints increases with the increasing of lead widths, while the reliability of the soldered joints reduces. When the lead widths are the same, the maximum equivalent stress of the soldered joints doesn＇t decrease completely with the increasing of lead pitches, a minimum value of the maximum equivalent stress values exists in all the curves. Under this condition the maximum equivalent stress of the soldewed joints is relatively the least, the reliability of soldered joints is high and the assembly is excellent. The simulating results indicate the best parameter： The lead width is 0.2 mm and lead pitch is 0.3 mm （the distance between two leads is 0.1 mm）, which are benefited for the micromation of QFP devices now. The minimum value of the maximum equivalent stress of soldered joints exists while lead width is 0.25 mm and lead pitch is 0.35 mm （the distance between two leads is 0.1 mm）, the devices can serve for a long time and the reliability is the highest, the assembly is excellent. The simulating results also indicate the fact that the lead width is 0.15 mm and lead pitch is 0.2 mm maybe the limit of QFP, which is significant for the high lead count and micromation of assembly.

Mg_(2)Sn-induced whisker growth on the surfaces of Mg/Sn/Mg ultrasonic-assisted soldering joints

In this paper,the phenomena of Mg_(2)Sn-induced Sn whisker growth were explored on the surfaces of Mg/Sn/Mg ultrasonic-assisted soldering joints after aging treatment.The in-situ observation and thermal analysis confirmed that the formation and the corrosion of Mg_(2)Sn nanoparticles were the dominant reason of Sn whisker growth.The Mg_(2)Sn accumulation at the grain boundaries would pin the dislocation slip and affect the continuity of whisker growth,and the boundary angle would thus play a decisive role in the growth shape of Sn whiskers due to the pining effect of Mg_(2)Sn.This study might be conducive to elucidating the growth behavior of Sn whiskers and provide the exploration strategy to further improve the bonding strength of Mg/Sn/Mg ultrasonic-assisted soldering joints.

The influence of temperature on creep behavior of Cu particle enhanced SnPb based composite soldered joints

Creep property of solder alloys is one of the important factors to affect the reliabdity of soldered joints in SMT （surface mount technology）. Particle-enhancement is a way to improve the properties of solder alloys and has caused much more attention than before. Temperatures applied to soldered joints are one of the primary factors of affecting creep properties of particle enhancement composite soldered joints. In this paper single shear lap creep specimens with a 1 mm^2 cross-sectional area were fabricated using Cu particle enhancement 63Sn37 Pb based composite soldered joints and 63Sn37 Pb eutectic soldered joints to examine the influence of temperature on creep behavior of soldered joints. Results indicated that the creep resistance of soldered joints of Cu particle enhancement 63Sn37Pb based composite soldered joint was generally superior to that of the conventional 63Sn37Pb soldered joint. At the same time, creep rupture life of the composite soldered joint was declined with increasing temperature and drop faster than that of the conventional 63Sn37 Pb eutectic soldered joint.

Effect of pad geometry on current density and temperature distributions in solder bump joints

Three-dimensional thermo-electrical finite element analyses were conducted to simulate the current density and temperature distributions in solder bump joints with different pad geometries.The effects of pad thickness,diameter and shape on current density and temperate distributions were investigated respectively.It was found that pads with larger thickness or/and diameter could reduce current density and temperature in solder bump significantly.Pad shapes affected the current density and temperature distributions in solder bumps.The relatively low current density and temperature didn＇t occur in the bump joint with traditional rounded pad but occurred in bump joints with octagonal and nonagonal pads respectively.Therefore,optimized pad geometry may be designed to alleviate the current crowding effect and reduce the bump temperature,and therefore delay electromigration failure and increase the mean-time-to-failure.

Design of a visual system for predicting SMT solder joint shape

A visual software system has been developed for predicting and analyzing the shape of solder joints in surface mount technology (SMT). The formation of the solder joint is numerically simulated through Surface Evolver program and the calculation is automated with an additional controller. A preprocessor is developed in which process parameters determining the shape of solder joints can be input visually and transferred into Evolver program automatically. A postprocessor is built to analyze the global three dimensional shape and cross section profiles of solder fillets in multiple windows. Also, the application for predicting the solder joint shape of RC chip component is conducted with the PSJS system.

Study on solder joint reliability of ceramic ball grid array component based on design of experiment method

Four process parameters, pad diameter, stencil thickness, ball diameter and stand-off were chosen as four control factors. By using an L25 （5^6 ） orthogonal array the ceramic ball grid array （ CBGA ） solder joints which have 25 different combinations of process parameters were designed. The numerical models of all the 25 CBGA solder joints were developed using the Sugrace Evolver. Utilizing the sugrace coordinate exported from the 25 CBGA solder joints numerical models, the finite element analysis models were set up and the nonlinear finite element analysis of the CBGA solder joints under thermal cycles were pegrormed by ANSYS. The thermal fatigue life of CBGA solder joint was calculated using Coffin-Manson equation. Based on the calculated thermal fatigue life results, the range analysis and the variance analysis were pegrormed. The results show that the fatigue life of CBGA solder joint is affected by the pad diameter, the stencil thickness, the ball diameter and the stand-off in a descending order, the best combination of process parameters results in the longest fatigue life is 0.07 mm stand-off, 0.125 mm stencil thickness of, 0.85 mm ball diameter and 0. 89 mm pad diameter. With 95% confidence the pad diameter has a significant effect on the reliability of CBGA solder joints whereas the stand-off, the stencil thickness and the ball diameter have little effect on the reliability of CBGA solder joints.

FORMATION AND CHANGE OF AuSn_4 COMPOUNDS AT INTERFACE BETWEEN PBGA SOLDER BALL AND Au/Ni/Cu METALLIZATION DURING LASER AND INFRA-RED REFLOW SOLDERING

Interactions between 63Sn37Pb solder and PBGA metallization (Au/Ni/Cu) duringlaser and infrared reflow soldering were studied. During laser reflow soldering process,a thin layer of AuSn_4 was observed at the interface of the solder bumps, its morphologywas strongly dependent on the laser reflow power and heating time. The solder bumpsformed by the first laser reflow was reflowed again to form the solder joints. TheAuSn_4 compounds formed in the first laser reflow process dissolved into the bulk solderafter the secondary infrared reflow process. The needle-like AuSn_4 changed into rod-like, and distributed inside the solder near the solder/pad interface.