Combining Mg and Al dissimilar metals further reduces structural weight,but the formation of intermetallic compounds(IMCs)affectsAl/Mg joint properties.To prevent IMCs,a Ni-Al_(2)O_(3)composite coating was pre-plated ...Combining Mg and Al dissimilar metals further reduces structural weight,but the formation of intermetallic compounds(IMCs)affectsAl/Mg joint properties.To prevent IMCs,a Ni-Al_(2)O_(3)composite coating was pre-plated on the Mg alloy substrate,and then Sn_(3.0)Ag_(0.5)Cu(SAC 305)solder was utilized to facilitate the joining of AZ31 Mg/6061 Al through ultrasonic-assisted soldering.We investigated the impactof Al_(2)O_(3)nano sol content in the coating on microstructure evolution,IMCs formation,and mechanical properties.Results indicated that theNi-Al_(2)O_(3)composite coating effectively suppressed the Mg-Sn reaction,thereby preventing the formation of Mg_(2)Sn IMC and significantlyenhancing joint strength.In joints with a Ni-Al_(2)O_(3)composite coating containing 50 mL/L Al_(2)O_(3)nano sol,no Mg_(2)Sn IMC was detectedafter 50 min of holding at 260℃,achieving a maximum shear strength of approximately 67.2 MPa.Increasing the Al_(2)O_(3)concentrationfurther expanded the soldering process window.For the joint with Ni-Al_(2)O_(3)(100 mL/L Al_(2)O_(3)nano sol)composite coating held at 260℃for 70 min,the coating was dissolved to a thickness of about 5.8μm,but no Mg_(2)Sn IMC was observed.The Ni-based solid solution formednear the coating/solder interface was strengthened,leading to fractures occurring within the SAC solder,and the maximum shear strengthfurther increased to 73.9 MPa.The strengthening mechanism of the joints facilitated by using the Ni-Al_(2)O_(3)composite coating was revealedby comparing with pure Ni-assisted joints.Therefore,employing a Ni-Al_(2)O_(3)composite coating as a barrier layer represents a promisingstrategy for inhibiting IMC formation during the joining of dissimilar metals.展开更多
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 le...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.展开更多
The solder joint strength of Pb/Sn soldering aluminum with electroless layer Sn/Bi and Cu was studied. The results show that the joint shear strength of electroless Sn/Bi on aluminum surface is lower than that of Cu. ...The solder joint strength of Pb/Sn soldering aluminum with electroless layer Sn/Bi and Cu was studied. The results show that the joint shear strength of electroless Sn/Bi on aluminum surface is lower than that of Cu. A Pb-riched region with porosity is formed in region of soldering fillet with electroless Sn/Bi. Both the electroless Sn/Bi layer and Pb-riched layer become thicker, which are the reasons why the shear strength of the solder joint with electroless Sn/Bi on aluminum surface is lower than that of electroless Cu, and the higher the thickness of the electroless Sn/Bi layer is, the lower the shear strength of solder joint is.展开更多
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...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.展开更多
Soldering experiments with Sn-3.5Ag-0.5Cu lead-free solder on Au/Ni/Cu pad were carried out by means of diode-laser and IR reflow soldering methods respectively.The influence of different heating methods as well as ou...Soldering experiments with Sn-3.5Ag-0.5Cu lead-free solder on Au/Ni/Cu pad were carried out by means of diode-laser and IR reflow soldering methods respectively.The influence of different heating methods as well as output power of diode-laser on shear force of micro-joints was studied and the relationship between the shear force and microstructures of micro-joints was analyzed.The results indicate that the formation of intermetallic compound Ag3Sn is the key factor to affect the shear force and the fine eutectic network structures of micro-joints as well as the dispersion morphology of fine compound Ag3Sn,in which eutectic network band is responsible for the improvement of the shear force of micro-joints soldered with Sn-Ag-Cu lead-free solder.With the increases of output power of diode-laser,the shear force and the microstructures change obviously.The eutectic network structures of micro-joints soldered with diode-laser soldering method are more homogeneous and the grains of Ag3Sn compounds are finer in the range of near optimal output power than those soldered with IR reflow soldering method,so the shear force is also higher than that using IR reflow soldering method.When the output power value of diode-laser is about 41.0 W,the shear force exhibits the highest value that is 70% higher than that using IR reflow soldering method.展开更多
The microstructural formation and properties of Sn-2.5Bi-xln-lZn-0.3Ag （in wt%） alloys and the evolution of soldered interfaces on a Cu substrate were investigated. Apart from the relatively low melting point （abou...The microstructural formation and properties of Sn-2.5Bi-xln-lZn-0.3Ag （in wt%） alloys and the evolution of soldered interfaces on a Cu substrate were investigated. Apart from the relatively low melting point （about 195C）, which is close to that of conventional eutectic Sn-Pb solder, the investigated solder presents superior wettability, solderability, and ductility. The refined equiaxial grains enhance the me- chanical properties, and the embedded bulk intermetallic compounds （IMCs） （Cu6Sn5 and CusZns） and granular Bi particles improve the joint reliability. The addition of In reduces the solubility of Zn in the 13-Sn matrix and strongly influences the separation and growth behaviors of the IMCs. The soldered interface of Sn-2.5Bi-xln-lZn-0.3Ag/Cu consists of Cu-Zn and Cu-Sn IMC layers.展开更多
The solder joint reliability of quad flat non-lead(QFN)package,which has become very popular over the past few years,has received intense interest.The finite element method(FEM)is essential to evaluate the reliability...The solder joint reliability of quad flat non-lead(QFN)package,which has become very popular over the past few years,has received intense interest.The finite element method(FEM)is essential to evaluate the reliability of QFN device.In this paper,Garofalo-Arrheninus model was implemented to simulate the deformation of QFN soldered joints.Equivalent creep strain of the soldered joints was calculated by means of finite element analyses,and was used to evaluate the reliability of QFN packages.It is found that the critical soldered joint of QFN is located the package corner while the maximum creep strain is obtained at the top interface of peripheral soldered joint.The creep strain is provided with periodicity and additivity as the thermal cycling.Nonlinear analysis of QFN package with different lead counts was presented as well,in which the phenomenon that the value of induced creep strain arise as the package size decreasing is noted.Moreover,SnPb and two lead-free solders,namely,Sn3.5Ag/Sn3.8Ag0.7Cu,were both taken into consideration.Simulated results indicate that the creep strain value of lead-free soldered joints is lower than that of SnPb soldered joints,which can be attributed to the difference of stiffness and coefficient of thermal expansion among three solders.Garofalo-Arrheninus model is used to calculate the creep strain of the QFN device for the first time in this study.The results provide an important basis for evaluating the reliability of QFN package.展开更多
Active soldering of 5A06 Al alloy was performed at 300 ℃ by using Sn-1Ti and Sn-1Ti-0.3Ga active solders, respectively. Theeffects of soldering time on the microstructure and mechanical properties of the joints were ...Active soldering of 5A06 Al alloy was performed at 300 ℃ by using Sn-1Ti and Sn-1Ti-0.3Ga active solders, respectively. Theeffects of soldering time on the microstructure and mechanical properties of the joints were investigated. The results showed that the Sn-1Tisolder broke the oxide film on the surface of the Al substrate and induced intergranular diffusion in the Al substrate. When Ga was added tothe solder, severe dissolution pits appeared in the Al substrate due to the action of Sn-1Ti-0.3Ga solder, and many Al particles were flakedfrom the matrix into the solder seam. Under thermal stress and the Ti adsorption effect, the oxide film cracked. With increasing solderingtime, the shear strength of 5A06 Al alloy joints soldered with Sn-1Ti and Sn-1Ti-0.3Ga active solders increased. When soldered for 90 min,the joint soldered with Sn-1Ti-0.3Ga solder had a higher shear strength of 22.12 MPa when compared to Sn-1Ti solder.展开更多
In recent years,intensive studies have been carried out to find an alternative for Tin(Sn)⁃Lead(Pb)solder alloys with increasing demand over lower temperature solder alloys in current electronic packaging industry.Hig...In recent years,intensive studies have been carried out to find an alternative for Tin(Sn)⁃Lead(Pb)solder alloys with increasing demand over lower temperature solder alloys in current electronic packaging industry.High temperature operational solder alloys seem to produce drawback to other components on the printed circuit board(PCB).Low melting temperature Sn58Bi substrate as a potential replacement was investigated in this paper based on the melting properties,wettability,and shear strength.The Sn58Bi was soldered at a temperature below 200℃on the Cu substrate,and the shear strength and contact angle were calculated.A peak temperature(melting temperature,T_(M))of 144.83℃was identified.Single lap joint method was performed at a strain rate of 0.1 mm/min and an average shear strength of 23.4 MPa was found from three samples.The contact angle(wettability)was calculated to study the solder joint behaviour at reflow temperature of 170℃.The contact angle of the Sn58Bi was found to be 32.4°and considered to be desired value since the angle is less than 50°.The low temperature soldering provides a preliminary result to allow further application on the real PCB.展开更多
To improve the wettability of hypereutectic Al−60Si alloy and enhance the mechanical properties of the joints,Al−60Si alloy was joined by ultrasonic soldering with Sn-9Zn solder,and a sound joint with in-situ Si parti...To improve the wettability of hypereutectic Al−60Si alloy and enhance the mechanical properties of the joints,Al−60Si alloy was joined by ultrasonic soldering with Sn-9Zn solder,and a sound joint with in-situ Si particle reinforcement was obtained.The oxide film of Al−60Si alloy at the interface was identified by transmission electron microscopy(TEM)analysis as amorphous Al_(2)O_(3).The oxide of Si particles in the base metal was also alumina.The oxide film of Al−60Si alloy was observed to be removed by ultrasonic vibration instead of holding treatment.Si particle-reinforced joints(35.7 vol.%)were obtained by increasing the ultrasonication time.The maximum shear strength peaked at 99.5 MPa for soldering at 330℃with an ultrasonic vibration time of 50 s.A model of forming of Si particles reinforced joint under the ultrasound was proposed,and ultrasonic vibration was considered to promote the dissolution of Al and migration of Si particles.展开更多
Dopamine polymerization reaction and hydrothermal method were used to prepare nickel coated Al_(2)O_(3)reinforcement phase(Ni/Al_(2)O_(3)).Ni/Al_(2)O_(3)reinforced Sn_(1.0)Ag_(0.5)Cu(SAC105)composite solder was prepar...Dopamine polymerization reaction and hydrothermal method were used to prepare nickel coated Al_(2)O_(3)reinforcement phase(Ni/Al_(2)O_(3)).Ni/Al_(2)O_(3)reinforced Sn_(1.0)Ag_(0.5)Cu(SAC105)composite solder was prepared using traditional casting method.The result shows that the nickel coating layer is continuous with uneven thickness.The interface between nickel and aluminum oxide exhibits a metallurgical bonding with coherent interface relationship.The strength,toughness and wettability of the SAC105 solder on the substrate are improved,while the conductivity is not decreased significantly.The fracture mode of composites transitions from a mixed toughness-brittleness mode to a purely toughness-dominated mode,characterized by many dimples.The prepared composite brazing material was made into solder paste for copper plate lap joint experiments.The maximum shear strength is achieved when the doping amount was 0.3wt%.The growth index of intermetallic compound at the brazing interface of Ni/Al_(2)O_(3)reinforced SAC105 composite solder is linearly fitted to n=0.39,demonstrating that the growth of intermetallic compound at the interface is a combined effect of grain boundary diffusion and bulk diffusion.展开更多
Flux-coated brazing and soldering material is a type of material-saving and emission-reducing composite material in recent years,which is the representative product of the development of brazing and soldering technolo...Flux-coated brazing and soldering material is a type of material-saving and emission-reducing composite material in recent years,which is the representative product of the development of brazing and soldering technology,which is highly concerned by welding researchers worldwide.This work mainly reviewed the research reports on the design,preparation technology,and application of flux-coated brazing and soldering materials,put forward the shortcomings of current research,and proposed the future research directions mainly focusing on the standards,the synergistic reaction mechanism between flux and metals,the alloying,and the morphology of flux-coated brazing and soldering materials in order to provide reference information and theoretical guidance for related research and technological development in the field of welding.展开更多
Short process forming techniques for brazing and soldering materials can shorten the process,improve product quality,and increase production efficiency,which has received much attention from welding researchers.This r...Short process forming techniques for brazing and soldering materials can shorten the process,improve product quality,and increase production efficiency,which has received much attention from welding researchers.This review mainly summarized the research reports on short process forming techniques for brazing and soldering materials.Firstly,the traditional process and its shortcomings were presented.Secondly,the latest research of short process forming technologies,such as continuous casting technique,atomization powder technique,solder ball forming technique,and rapid solidification technique,was summarized,and the traditional forming performance of several brazing and soldering materials was introduced.Finally,the current restrictions and research trends of short process forming technique for brazing and solder materials were put forward,providing theoretical guidance and reference for related research and technique development in brazing and soldering field.展开更多
The vacuum volatilization kinetics of Pb in In-Pb solder was investigated.The results indicate a significant increase in the vacuum volatilization rates of Pb,25In-75Pb,40In-60Pb,and In with increasing temperatures fr...The vacuum volatilization kinetics of Pb in In-Pb solder was investigated.The results indicate a significant increase in the vacuum volatilization rates of Pb,25In-75Pb,40In-60Pb,and In with increasing temperatures from 923 to 1123 K,system pressure of 3 Pa and holding time of 30 min.The mass transfer coefficients and apparent activation energies of Pb and its alloys were determined at various temperatures.Additionally,a kinetics model was developed to describe Pb vacuum volatilization in high-temperature melts.It is obtained that the vapor mass transfer is the factor limiting the vacuum volatilization rates of Pb and In-Pb alloys under the above specified conditions.展开更多
Sn-based solder is a widely used interconnection material in the field of electronic packaging;however,the performance requirements for these solders are becoming increasingly demanding owing to the rapid development ...Sn-based solder is a widely used interconnection material in the field of electronic packaging;however,the performance requirements for these solders are becoming increasingly demanding owing to the rapid development in this area.In recent years,the addition of micro/nanoreinforcement phases to Sn-based solders has provided a solution to improve the intrinsic properties of the solders.This paper reviews the progress in Sn-based micro/nanoreinforced composite solders over the past decade.The types of reinforcement particles,preparation methods of the composite solders,and strengthening effects on the microstructure,wettability,melting point,mechanical properties,and corrosion resistance under different particle-addition levels are discussed and summarized.The mechanisms of performance enhancement are summarized based on material-strengthening effects such as grain refinement and second-phase dispersion strengthening.In addition,we discuss the current shortcomings of such composite solders and possible future improvements,thereby establishing a theoretical foundation for the future development of Sn-based solders.展开更多
The construction of intermetallic compounds(IMCs)connection layers with special compositions by adding small amounts of alloying elements has been proven to be an effective strategy for improving the reliability of el...The construction of intermetallic compounds(IMCs)connection layers with special compositions by adding small amounts of alloying elements has been proven to be an effective strategy for improving the reliability of electronic component interconnect.However,the synergistic effect mechanism of multi-component alloy compositions on the growth behavior of IMCs is not clear.Herein,we successfully prepared a new quaternary alloy solder with a composition of Sn-0.7Cu-0.175Pt-0.025Al(wt%)using the high-throughput screening(HTS)method.The results showed that it possesses excellent welding performance with an inhibition rate over 40%on the growth of IMCs layers.For Cu_(6)Sn_(5),the co-doping of Al and Pt not only greatly improves its thermodynamic stability,but also effectively suppresses the phase transition.Meanwhile,the co-doping of Al and Pt also significantly delays the generation time of Kirkendall defects.The substitution sites of Al and Pt in Cu_(6)Sn_(5)have been explored using atomic resolution imaging and advanced data informatics,indicating that Al and Pt preferentially substitute Sn and Cu atoms,respectively,to generate(Cu,Pt)_(6)(Sn,Al)_(5).A one-dimensional(1D)kinetic model of the IMCs layer growth at the Sn solder/Cu substrate interface was derived and validated,and the results showed that the error of the derived mathematical model is less than 5%.Finally,the synergistic mechanism of Al and Pt co-doping on the growth rate of Cu_(6)Sn_(5)was further elucidated.This work provides a feasible route for the design and development of multi-component alloy solders.展开更多
The corrosion behavior and life of Sn−3.0Ag−0.5Cu solder joints were investigated through fire smoke exposure experiments within the temperature range of 45−80℃.The nonlinear Wiener process and Arrhenius equation wer...The corrosion behavior and life of Sn−3.0Ag−0.5Cu solder joints were investigated through fire smoke exposure experiments within the temperature range of 45−80℃.The nonlinear Wiener process and Arrhenius equation were used to establish the probability distribution function and prediction model of the solder joint’s average life and individual remaining useful life.The results indicate that solder joint resistance shows a nonlinear growth trend with time increasing.After 24 h,the solder joint transforms from spherical to rose-like shapes.Higher temperatures accelerate solder joint failure,and the relationship between failure time and temperature conforms to the Arrhenius equation.The predicted life of the model is in good agreement with experimental results,demonstrating the effectiveness and accuracy of the model.展开更多
Kirkendall voids(KVs)at the Cu/Sn interface are a typical failure in integrated circuits,leading to solder joint cracking and electrical disconnection.Although the formation of KVs has been attributed to the differenc...Kirkendall voids(KVs)at the Cu/Sn interface are a typical failure in integrated circuits,leading to solder joint cracking and electrical disconnection.Although the formation of KVs has been attributed to the difference in atomic diffusion rates at the Cu/Sn interface,the role of Cu intrinsic"quality"parameters(crystal defects)in this process remains unclear.This work systematically investigated the effects of Cu crystal defects on KVs:Cu substrates with different lattice defects and grain boundaries were prepared using proprietary electrodeposition additives,and the number of defects was quantitatively characterized by micro-strain,geometric dislocation density,and geometric phase analysis.The thermal aging experiments further showed that the formation of intermetallic compounds and KVs was related to crystal defect energy.When the grain boundary energy was higher than the lattice energy,the additional driving force resulted in short-circuit diffusion,causing local Cu depletion and voids.The lowcrystal-defect samples maintained the local Cu/Sn interdiffusion equilibrium,resulting in fewer voids after 1000 h.This study emphasizes that regulating the crystal defects can reduce KVs and provides a new insight for improving the integrated solder joint's reliability.展开更多
Technological advancements and the emphasis on reducing the use of hazardous materials,such as Pb,have led to the widely use of Sn-based Pb-free solder in advanced packaging technology.With the miniaturization of sold...Technological advancements and the emphasis on reducing the use of hazardous materials,such as Pb,have led to the widely use of Sn-based Pb-free solder in advanced packaging technology.With the miniaturization of solder joints,Sn-based micro solder joints often contain single or limitedβ-Sn grains.The strong anisotropy ofβ-Sn,which is significantly correlated with the reliability of the micro solder joints during service,requires the development of methods for controlling the orientations of theseβ-Sn grains.In this review,we focus on the anisotropy of theβ-Sn grains in micro solder joints and the interactions betweenβ-Sn grain orientation and reliability issues concerning electromigration(EM),thermomigration(TM),EM+TM,corrosion process,tensile and shear creep behavior,thermal cycling(TC)and cryogenic temperature.Furthermore,we summarize the strategies for controlling theβ-Sn orientation in micro solder joints.The methods include changing the solder joint size and composition,adding additives,nucleating on specific substrates and interfacial intermetallic compounds,with the aid of external loads during solidification process and introducing heredity effect of theβ-Sn texture during multi-reflow.Finally,the{101}and{301}twinning models with∼60°rotations about a common〈100〉are adopted to explain the mechanism ofβ-Sn grain nucleation and morphology.The shortcomings of the existing methods and the further potential for the development in the field are discussed to promote the application of Pb-free solders in advanced packaging.展开更多
基金support from the National Natural Science Foundation of China(grant numbers 52275385 and U2167216).
文摘Combining Mg and Al dissimilar metals further reduces structural weight,but the formation of intermetallic compounds(IMCs)affectsAl/Mg joint properties.To prevent IMCs,a Ni-Al_(2)O_(3)composite coating was pre-plated on the Mg alloy substrate,and then Sn_(3.0)Ag_(0.5)Cu(SAC 305)solder was utilized to facilitate the joining of AZ31 Mg/6061 Al through ultrasonic-assisted soldering.We investigated the impactof Al_(2)O_(3)nano sol content in the coating on microstructure evolution,IMCs formation,and mechanical properties.Results indicated that theNi-Al_(2)O_(3)composite coating effectively suppressed the Mg-Sn reaction,thereby preventing the formation of Mg_(2)Sn IMC and significantlyenhancing joint strength.In joints with a Ni-Al_(2)O_(3)composite coating containing 50 mL/L Al_(2)O_(3)nano sol,no Mg_(2)Sn IMC was detectedafter 50 min of holding at 260℃,achieving a maximum shear strength of approximately 67.2 MPa.Increasing the Al_(2)O_(3)concentrationfurther expanded the soldering process window.For the joint with Ni-Al_(2)O_(3)(100 mL/L Al_(2)O_(3)nano sol)composite coating held at 260℃for 70 min,the coating was dissolved to a thickness of about 5.8μm,but no Mg_(2)Sn IMC was observed.The Ni-based solid solution formednear the coating/solder interface was strengthened,leading to fractures occurring within the SAC solder,and the maximum shear strengthfurther increased to 73.9 MPa.The strengthening mechanism of the joints facilitated by using the Ni-Al_(2)O_(3)composite coating was revealedby comparing with pure Ni-assisted joints.Therefore,employing a Ni-Al_(2)O_(3)composite coating as a barrier layer represents a promisingstrategy for inhibiting IMC formation during the joining of dissimilar metals.
基金This project is supported by Provincial Six Kind Skilled Personnel Project of Jiangsu,China(No.06-E-020).
文摘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.
文摘The solder joint strength of Pb/Sn soldering aluminum with electroless layer Sn/Bi and Cu was studied. The results show that the joint shear strength of electroless Sn/Bi on aluminum surface is lower than that of Cu. A Pb-riched region with porosity is formed in region of soldering fillet with electroless Sn/Bi. Both the electroless Sn/Bi layer and Pb-riched layer become thicker, which are the reasons why the shear strength of the solder joint with electroless Sn/Bi on aluminum surface is lower than that of electroless Cu, and the higher the thickness of the electroless Sn/Bi layer is, the lower the shear strength of solder joint is.
文摘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.
文摘Soldering experiments with Sn-3.5Ag-0.5Cu lead-free solder on Au/Ni/Cu pad were carried out by means of diode-laser and IR reflow soldering methods respectively.The influence of different heating methods as well as output power of diode-laser on shear force of micro-joints was studied and the relationship between the shear force and microstructures of micro-joints was analyzed.The results indicate that the formation of intermetallic compound Ag3Sn is the key factor to affect the shear force and the fine eutectic network structures of micro-joints as well as the dispersion morphology of fine compound Ag3Sn,in which eutectic network band is responsible for the improvement of the shear force of micro-joints soldered with Sn-Ag-Cu lead-free solder.With the increases of output power of diode-laser,the shear force and the microstructures change obviously.The eutectic network structures of micro-joints soldered with diode-laser soldering method are more homogeneous and the grains of Ag3Sn compounds are finer in the range of near optimal output power than those soldered with IR reflow soldering method,so the shear force is also higher than that using IR reflow soldering method.When the output power value of diode-laser is about 41.0 W,the shear force exhibits the highest value that is 70% higher than that using IR reflow soldering method.
基金the National Natural Science Foundation of China(No.51077099)Shang hai Baosteel Group Co.(No.50834011)
文摘The microstructural formation and properties of Sn-2.5Bi-xln-lZn-0.3Ag （in wt%） alloys and the evolution of soldered interfaces on a Cu substrate were investigated. Apart from the relatively low melting point （about 195C）, which is close to that of conventional eutectic Sn-Pb solder, the investigated solder presents superior wettability, solderability, and ductility. The refined equiaxial grains enhance the me- chanical properties, and the embedded bulk intermetallic compounds （IMCs） （Cu6Sn5 and CusZns） and granular Bi particles improve the joint reliability. The addition of In reduces the solubility of Zn in the 13-Sn matrix and strongly influences the separation and growth behaviors of the IMCs. The soldered interface of Sn-2.5Bi-xln-lZn-0.3Ag/Cu consists of Cu-Zn and Cu-Sn IMC layers.
基金supported by Jiangsu Provincial General Colleges and Universities Postgraduate Scientific Research Innovative Plan of China(Grant No.CX07B_087Z)Nanjing University of Aeronautics and Astronautics Doctoral Dissertation Innovation and Excellence Producing Foundation of China(Grant No.BCXJ09-07)
文摘The solder joint reliability of quad flat non-lead(QFN)package,which has become very popular over the past few years,has received intense interest.The finite element method(FEM)is essential to evaluate the reliability of QFN device.In this paper,Garofalo-Arrheninus model was implemented to simulate the deformation of QFN soldered joints.Equivalent creep strain of the soldered joints was calculated by means of finite element analyses,and was used to evaluate the reliability of QFN packages.It is found that the critical soldered joint of QFN is located the package corner while the maximum creep strain is obtained at the top interface of peripheral soldered joint.The creep strain is provided with periodicity and additivity as the thermal cycling.Nonlinear analysis of QFN package with different lead counts was presented as well,in which the phenomenon that the value of induced creep strain arise as the package size decreasing is noted.Moreover,SnPb and two lead-free solders,namely,Sn3.5Ag/Sn3.8Ag0.7Cu,were both taken into consideration.Simulated results indicate that the creep strain value of lead-free soldered joints is lower than that of SnPb soldered joints,which can be attributed to the difference of stiffness and coefficient of thermal expansion among three solders.Garofalo-Arrheninus model is used to calculate the creep strain of the QFN device for the first time in this study.The results provide an important basis for evaluating the reliability of QFN package.
基金the National Natural Science Foundation of China(No.52171045).
文摘Active soldering of 5A06 Al alloy was performed at 300 ℃ by using Sn-1Ti and Sn-1Ti-0.3Ga active solders, respectively. Theeffects of soldering time on the microstructure and mechanical properties of the joints were investigated. The results showed that the Sn-1Tisolder broke the oxide film on the surface of the Al substrate and induced intergranular diffusion in the Al substrate. When Ga was added tothe solder, severe dissolution pits appeared in the Al substrate due to the action of Sn-1Ti-0.3Ga solder, and many Al particles were flakedfrom the matrix into the solder seam. Under thermal stress and the Ti adsorption effect, the oxide film cracked. With increasing solderingtime, the shear strength of 5A06 Al alloy joints soldered with Sn-1Ti and Sn-1Ti-0.3Ga active solders increased. When soldered for 90 min,the joint soldered with Sn-1Ti-0.3Ga solder had a higher shear strength of 22.12 MPa when compared to Sn-1Ti solder.
文摘In recent years,intensive studies have been carried out to find an alternative for Tin(Sn)⁃Lead(Pb)solder alloys with increasing demand over lower temperature solder alloys in current electronic packaging industry.High temperature operational solder alloys seem to produce drawback to other components on the printed circuit board(PCB).Low melting temperature Sn58Bi substrate as a potential replacement was investigated in this paper based on the melting properties,wettability,and shear strength.The Sn58Bi was soldered at a temperature below 200℃on the Cu substrate,and the shear strength and contact angle were calculated.A peak temperature(melting temperature,T_(M))of 144.83℃was identified.Single lap joint method was performed at a strain rate of 0.1 mm/min and an average shear strength of 23.4 MPa was found from three samples.The contact angle(wettability)was calculated to study the solder joint behaviour at reflow temperature of 170℃.The contact angle of the Sn58Bi was found to be 32.4°and considered to be desired value since the angle is less than 50°.The low temperature soldering provides a preliminary result to allow further application on the real PCB.
基金financial support from the National Natural Science Foundation of China(Nos.52275385,U2167216)Sichuan Province Science and Technology Support Program,China(No.2022YFG0086).
文摘To improve the wettability of hypereutectic Al−60Si alloy and enhance the mechanical properties of the joints,Al−60Si alloy was joined by ultrasonic soldering with Sn-9Zn solder,and a sound joint with in-situ Si particle reinforcement was obtained.The oxide film of Al−60Si alloy at the interface was identified by transmission electron microscopy(TEM)analysis as amorphous Al_(2)O_(3).The oxide of Si particles in the base metal was also alumina.The oxide film of Al−60Si alloy was observed to be removed by ultrasonic vibration instead of holding treatment.Si particle-reinforced joints(35.7 vol.%)were obtained by increasing the ultrasonication time.The maximum shear strength peaked at 99.5 MPa for soldering at 330℃with an ultrasonic vibration time of 50 s.A model of forming of Si particles reinforced joint under the ultrasound was proposed,and ultrasonic vibration was considered to promote the dissolution of Al and migration of Si particles.
基金ational Natural Science Foundation of China(U1604132)Central Plains Talents Program-Fund of Central Plains Leading Talents(ZYYCYU002130)+1 种基金Key Technology Research and Development Program of Henan Province(222102230114)Major Scientific Research Foundation of Higher Education of Henan Province(23B430003)。
文摘Dopamine polymerization reaction and hydrothermal method were used to prepare nickel coated Al_(2)O_(3)reinforcement phase(Ni/Al_(2)O_(3)).Ni/Al_(2)O_(3)reinforced Sn_(1.0)Ag_(0.5)Cu(SAC105)composite solder was prepared using traditional casting method.The result shows that the nickel coating layer is continuous with uneven thickness.The interface between nickel and aluminum oxide exhibits a metallurgical bonding with coherent interface relationship.The strength,toughness and wettability of the SAC105 solder on the substrate are improved,while the conductivity is not decreased significantly.The fracture mode of composites transitions from a mixed toughness-brittleness mode to a purely toughness-dominated mode,characterized by many dimples.The prepared composite brazing material was made into solder paste for copper plate lap joint experiments.The maximum shear strength is achieved when the doping amount was 0.3wt%.The growth index of intermetallic compound at the brazing interface of Ni/Al_(2)O_(3)reinforced SAC105 composite solder is linearly fitted to n=0.39,demonstrating that the growth of intermetallic compound at the interface is a combined effect of grain boundary diffusion and bulk diffusion.
基金Henan Province Central Guiding Local Science and Technology Development Fund Project(Z20231811002)。
文摘Flux-coated brazing and soldering material is a type of material-saving and emission-reducing composite material in recent years,which is the representative product of the development of brazing and soldering technology,which is highly concerned by welding researchers worldwide.This work mainly reviewed the research reports on the design,preparation technology,and application of flux-coated brazing and soldering materials,put forward the shortcomings of current research,and proposed the future research directions mainly focusing on the standards,the synergistic reaction mechanism between flux and metals,the alloying,and the morphology of flux-coated brazing and soldering materials in order to provide reference information and theoretical guidance for related research and technological development in the field of welding.
基金National Key Research and Development Program(2021YFB3401101)。
文摘Short process forming techniques for brazing and soldering materials can shorten the process,improve product quality,and increase production efficiency,which has received much attention from welding researchers.This review mainly summarized the research reports on short process forming techniques for brazing and soldering materials.Firstly,the traditional process and its shortcomings were presented.Secondly,the latest research of short process forming technologies,such as continuous casting technique,atomization powder technique,solder ball forming technique,and rapid solidification technique,was summarized,and the traditional forming performance of several brazing and soldering materials was introduced.Finally,the current restrictions and research trends of short process forming technique for brazing and solder materials were put forward,providing theoretical guidance and reference for related research and technique development in brazing and soldering field.
基金financially supported by the Fundamental Research Project of Yunnan Province,China(Nos.202301AW070020,202201AT070229,202105AC160091,202202AB080018).
文摘The vacuum volatilization kinetics of Pb in In-Pb solder was investigated.The results indicate a significant increase in the vacuum volatilization rates of Pb,25In-75Pb,40In-60Pb,and In with increasing temperatures from 923 to 1123 K,system pressure of 3 Pa and holding time of 30 min.The mass transfer coefficients and apparent activation energies of Pb and its alloys were determined at various temperatures.Additionally,a kinetics model was developed to describe Pb vacuum volatilization in high-temperature melts.It is obtained that the vapor mass transfer is the factor limiting the vacuum volatilization rates of Pb and In-Pb alloys under the above specified conditions.
基金financially supported by the State Key Laboratory for Mechanical Behavior of Materials,China(No.202325012)the National Natural Science Foundation of China(No.U21A20128).
文摘Sn-based solder is a widely used interconnection material in the field of electronic packaging;however,the performance requirements for these solders are becoming increasingly demanding owing to the rapid development in this area.In recent years,the addition of micro/nanoreinforcement phases to Sn-based solders has provided a solution to improve the intrinsic properties of the solders.This paper reviews the progress in Sn-based micro/nanoreinforced composite solders over the past decade.The types of reinforcement particles,preparation methods of the composite solders,and strengthening effects on the microstructure,wettability,melting point,mechanical properties,and corrosion resistance under different particle-addition levels are discussed and summarized.The mechanisms of performance enhancement are summarized based on material-strengthening effects such as grain refinement and second-phase dispersion strengthening.In addition,we discuss the current shortcomings of such composite solders and possible future improvements,thereby establishing a theoretical foundation for the future development of Sn-based solders.
基金financially supported by the Innovation Team Cultivation Project of Yunnan Province(No.202005AE160016)the Key Research&Development Program of Yunnan Province(No.202103AA080017)Yunnan Ten Thousand Talents Plan Young&Elite Talents Project(No.YNWR-QNBJ2018-044)。
文摘The construction of intermetallic compounds(IMCs)connection layers with special compositions by adding small amounts of alloying elements has been proven to be an effective strategy for improving the reliability of electronic component interconnect.However,the synergistic effect mechanism of multi-component alloy compositions on the growth behavior of IMCs is not clear.Herein,we successfully prepared a new quaternary alloy solder with a composition of Sn-0.7Cu-0.175Pt-0.025Al(wt%)using the high-throughput screening(HTS)method.The results showed that it possesses excellent welding performance with an inhibition rate over 40%on the growth of IMCs layers.For Cu_(6)Sn_(5),the co-doping of Al and Pt not only greatly improves its thermodynamic stability,but also effectively suppresses the phase transition.Meanwhile,the co-doping of Al and Pt also significantly delays the generation time of Kirkendall defects.The substitution sites of Al and Pt in Cu_(6)Sn_(5)have been explored using atomic resolution imaging and advanced data informatics,indicating that Al and Pt preferentially substitute Sn and Cu atoms,respectively,to generate(Cu,Pt)_(6)(Sn,Al)_(5).A one-dimensional(1D)kinetic model of the IMCs layer growth at the Sn solder/Cu substrate interface was derived and validated,and the results showed that the error of the derived mathematical model is less than 5%.Finally,the synergistic mechanism of Al and Pt co-doping on the growth rate of Cu_(6)Sn_(5)was further elucidated.This work provides a feasible route for the design and development of multi-component alloy solders.
基金National Natural Science Foundation of China (No. 52206180)Fundamental Research Funds for the Central Universities,China (No. WK2320000050)。
文摘The corrosion behavior and life of Sn−3.0Ag−0.5Cu solder joints were investigated through fire smoke exposure experiments within the temperature range of 45−80℃.The nonlinear Wiener process and Arrhenius equation were used to establish the probability distribution function and prediction model of the solder joint’s average life and individual remaining useful life.The results indicate that solder joint resistance shows a nonlinear growth trend with time increasing.After 24 h,the solder joint transforms from spherical to rose-like shapes.Higher temperatures accelerate solder joint failure,and the relationship between failure time and temperature conforms to the Arrhenius equation.The predicted life of the model is in good agreement with experimental results,demonstrating the effectiveness and accuracy of the model.
基金financially supported by the National Natural Science Foundation of China(Nos.62274172 and 62304143)High-level Talent Innovation and Entrepreneurship Plan of Shenzhen Key Technology Research and Development Team Funding Application(No.JSGGKQTD20221101115650008)+2 种基金Shenzhen-Hong Kong-Macao Science and Technology Plan Project(Category C)(No.SGDX20220530111004028)Macao Science and Technology Development Fund(FDCT)for funding(No.0013/2024/RIB1)the Multi-Year Research Grant(MYRG)from University of Macao(Nos.MYRG-GRG2023-00140-IAPME-UMDF and MYRG-GRG2024-00206-IAPME)
文摘Kirkendall voids(KVs)at the Cu/Sn interface are a typical failure in integrated circuits,leading to solder joint cracking and electrical disconnection.Although the formation of KVs has been attributed to the difference in atomic diffusion rates at the Cu/Sn interface,the role of Cu intrinsic"quality"parameters(crystal defects)in this process remains unclear.This work systematically investigated the effects of Cu crystal defects on KVs:Cu substrates with different lattice defects and grain boundaries were prepared using proprietary electrodeposition additives,and the number of defects was quantitatively characterized by micro-strain,geometric dislocation density,and geometric phase analysis.The thermal aging experiments further showed that the formation of intermetallic compounds and KVs was related to crystal defect energy.When the grain boundary energy was higher than the lattice energy,the additional driving force resulted in short-circuit diffusion,causing local Cu depletion and voids.The lowcrystal-defect samples maintained the local Cu/Sn interdiffusion equilibrium,resulting in fewer voids after 1000 h.This study emphasizes that regulating the crystal defects can reduce KVs and provides a new insight for improving the integrated solder joint's reliability.
基金financially supported by the National Natural Science Foundation of China(No.52075072)the Provincial Applied Basic Research Program of Liaoning Provincial Department of Science and Technology(No.2023JH2/101300181)the Key R&D Program of Shandong Province,China(No.2022CXGC020408)。
文摘Technological advancements and the emphasis on reducing the use of hazardous materials,such as Pb,have led to the widely use of Sn-based Pb-free solder in advanced packaging technology.With the miniaturization of solder joints,Sn-based micro solder joints often contain single or limitedβ-Sn grains.The strong anisotropy ofβ-Sn,which is significantly correlated with the reliability of the micro solder joints during service,requires the development of methods for controlling the orientations of theseβ-Sn grains.In this review,we focus on the anisotropy of theβ-Sn grains in micro solder joints and the interactions betweenβ-Sn grain orientation and reliability issues concerning electromigration(EM),thermomigration(TM),EM+TM,corrosion process,tensile and shear creep behavior,thermal cycling(TC)and cryogenic temperature.Furthermore,we summarize the strategies for controlling theβ-Sn orientation in micro solder joints.The methods include changing the solder joint size and composition,adding additives,nucleating on specific substrates and interfacial intermetallic compounds,with the aid of external loads during solidification process and introducing heredity effect of theβ-Sn texture during multi-reflow.Finally,the{101}and{301}twinning models with∼60°rotations about a common〈100〉are adopted to explain the mechanism ofβ-Sn grain nucleation and morphology.The shortcomings of the existing methods and the further potential for the development in the field are discussed to promote the application of Pb-free solders in advanced packaging.
