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
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 t...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 rel...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
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
Magnesium and aluminum alloys are widely used in various industries because of their excellent properties,and their reliable connection may increase application of materials.Intermetallic compounds(IMCs)affect the joi...Magnesium and aluminum alloys are widely used in various industries because of their excellent properties,and their reliable connection may increase application of materials.Intermetallic compounds(IMCs)affect the joint performance of Mg/Al.In this study,AZ31 Mg alloy with/without a nickel(Ni)coating layer and 6061 Al alloy were joined by ultrasonic-assisted soldering with Sn-3.0Ag-0.5Cu(SAC)filler.The effects of the Ni coating layer on the microstructure and mechanical properties of Mg/Al joints were systematically investigated.The Ni coating layer had a significant effect on formation of the Mg_(2)Sn IMC and the mechanical properties of Mg/Al joints.The blocky Mg_(2)Sn IMC formed in the Mg/SAC/Al joints without a Ni coating layer.The content of the Mg_(2)Sn IMC increased with increasing soldering temperature,but the joint strength decreased.The joint without a Ni coating layer fractured at the blocky Mg_(2)Sn IMC in the solder,and the maximum shear strength was 32.2 MPa.By pre-plating Ni on the Mg substrate,formation of the blocky Mg_(2)Sn IMC was inhibited in the soldering temperature range 240–280℃and the joint strength increased.However,when the soldering temperature increased to 310℃,the blocky Mg_(2)Sn IMC precipitated again in the solder.Transmission electron microscopy showed that some nano-sized Mg_(2)Sn IMC and the(Cu,Ni)_(6)Sn_(5)phase formed in the Mg(Ni)/SAC/Al joint soldered at 280℃,indicating that the Ni coating layer could no longer prevent diffusion of Mg into the solder when the soldering temperature was higher than 280℃.The maximum shear strength of the Mg(Ni)/SAC/Al joint was 58.2 MPa for a soldering temperature of 280℃,which was 80.7%higher than that of the Mg/SAC/Al joint,and the joint was broken at the Mg(Ni)/SAC interface.Pre-plating Ni is a feasible way to inhibit formation of IMCs when joining dissimilar metals.展开更多
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 ab...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.展开更多
In recent years,the rapid development of the new energy industry has driven continuous upgrading of high-density and high-power devices.In the packaging and assembly process,the problem of differentiation of the therm...In recent years,the rapid development of the new energy industry has driven continuous upgrading of high-density and high-power devices.In the packaging and assembly process,the problem of differentiation of the thermal needs of different modules has become increasingly prominent,especially for small-size solder joints with high heat dissipation in high-power devices.Localized soldering is con-sidered a suitable choice to selectively heat the desired target while not affecting other heat-sensitive chips.This paper reviews several local-ized soldering processes,focusing on the size of solder joints,soldering materials,and current state of the technique.Each localized solder-ing process was discovered to have unique characteristics.The requirements for small-size solder joints are met by laser soldering,microres-istance soldering,and self-propagating soldering;however,laser soldering has difficulty meeting the requirements for large heat dissipation,microresistance soldering requires the application of pressure to joints,and self-propagating soldering requires ignition materials.However,for small-size solder junctions,selective wave soldering,microwave soldering,and ultrasonic soldering are not appropriate.Because the magnetic field can be focused on a tiny area and the output energy of induction heating is large,induction soldering can be employed as a significant trend in future research.展开更多
The electronic product has gravitated towards component miniaturization and integration, employment of lead-free materials, and low-temperature soldering processes. Noble-metal aerogels have drawn increasing attention...The electronic product has gravitated towards component miniaturization and integration, employment of lead-free materials, and low-temperature soldering processes. Noble-metal aerogels have drawn increasing attention for high conduction and low density. However,the noble metal aerogels with outstanding solderability were rarely studied. This work has successfully synthesized an aerogel derived from silver nanowires(AgNWs) using a liquid phase reduction method. It is found that the noble metal aerogels can be made into diverse aerogel preformed soldering sheets. The influence of bonding temperature(150-300 ℃), time(2-20 min), and pressure(5-20 MPa) on the joint strength of the AgNWs aerogel affixed to electroless nickel/silver copper plates were investigated. Additionally, the AgNWs aerogel displays almost the same shear strength for substrates of various sizes. In a word, this study presents a flux-free, high-strength, and adaptable soldering structural material.展开更多
The tensile properties of Sn-9Zn-xAg-ySb;{(x, y) = (0.2, 0.6), (0.2, 0.8), (0.6, 0.2), (0.8, 0.2)} lead-free solders were investigated. All the test samples were annealed at 150°C for 1 hour. The tests are carrie...The tensile properties of Sn-9Zn-xAg-ySb;{(x, y) = (0.2, 0.6), (0.2, 0.8), (0.6, 0.2), (0.8, 0.2)} lead-free solders were investigated. All the test samples were annealed at 150°C for 1 hour. The tests are carried out at room temperature at the strain rate of 4.17 × 10<sup>-3</sup> s<sup>-1</sup>, 20.85 × 10<sup>-3</sup> s<sup>-1</sup>, and 208.5 × 10<sup>-3</sup> s<sup>-1</sup>. It is seen that the tensile strength increases and the ductility decrease with increasing the strain rate over the investigated range. From the strain rate change test results, the strain sensitivity values are found in the range of 0.0831 to 0.1455 due to the addition of different alloying elements.展开更多
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 (S...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.展开更多
In some situations, the accelerated life test on environmental stress for electronic products is not easily implemented due to various restrictions, and thus engineers are lacking of data of the product life test. Con...In some situations, the accelerated life test on environmental stress for electronic products is not easily implemented due to various restrictions, and thus engineers are lacking of data of the product life test. Concerning this problem, environmental life of the printed circuit board(PCB) board is calculated by way of physics of failure. Influences of thermal cycle and vibration on PCB and its components are studied. Based on the analysis of force and stress between components and the PCB board in thermal cycle events and vibration events, four life computing models of pins and soldered dots are established. The miller damage ratio is used to calculate the accumulated damage of a pin or a soldered dot, and then the environment life of the PCB board can be determined by the first failed one. Finally, an example is used to illustrate the models and their calculations.展开更多
This article explores tile effects of phosphorus addition on the wettability between Sn-9Zn solder alloy and Cu substrates, the oxidation behavior and the corrosion behavior of Sn-9Zn solder alloy. Spreading test was ...This article explores tile effects of phosphorus addition on the wettability between Sn-9Zn solder alloy and Cu substrates, the oxidation behavior and the corrosion behavior of Sn-9Zn solder alloy. Spreading test was used to characterize the wettability of Sn-9Zn-xP solder alloys to Cu substrates. The oxidation and corrosion behaviors of Sn- 9Zn-xP solder alloys were determined by means of weight gaining, and secondary ion mass spectrometry was used to analyze the oxygen content. The role and mechanism of P in the solder alloys were also discussed. It is found that the addition of P can significantly improve the wettability of the solder alloys. Incorporating P into Sn-9Zn solder alloy obviously decreases the oxygen content and enhances the oxidation and corrosion resistance. Microstructure observations show that an appropriate amount of P can greatly refine coarse rod-like Zn-rich phases in Sn-gZn solder alloy.展开更多
To obtain novel intermediate temperature alloy solders with a melting temperature of 400-600°C,nominal(Ag-Cu28)-30Sn alloys without or with a trace addition(0.5 or 1.0 wt.%) of rare earth(RE) element La wer...To obtain novel intermediate temperature alloy solders with a melting temperature of 400-600°C,nominal(Ag-Cu28)-30Sn alloys without or with a trace addition(0.5 or 1.0 wt.%) of rare earth(RE) element La were prepared by mechanical alloying.The aim of this research is to investigate the effects of the addition of La on the microstructures,alloying process and melting properties of(Ag-Cu28)-30Sn alloys.The results show that the addition of La produces no new phase.A trace amount of La addition can effectively refine the grain size,but the excessive addition of 1.0 wt.% La inhibits the alloying process.The influence of La on the melting temperatures of solder alloys is negligible.However,the trace addition of 0.5 wt.% La can distinctly reduce the fusion zone and improve the melting property of(Ag-Cu28)-30Sn alloys.展开更多
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.
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.
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(grant numbers 52275385 and U2167216)the Sichuan Province Science and Technology Support Program(grant number 2022YFG0086)。
文摘Magnesium and aluminum alloys are widely used in various industries because of their excellent properties,and their reliable connection may increase application of materials.Intermetallic compounds(IMCs)affect the joint performance of Mg/Al.In this study,AZ31 Mg alloy with/without a nickel(Ni)coating layer and 6061 Al alloy were joined by ultrasonic-assisted soldering with Sn-3.0Ag-0.5Cu(SAC)filler.The effects of the Ni coating layer on the microstructure and mechanical properties of Mg/Al joints were systematically investigated.The Ni coating layer had a significant effect on formation of the Mg_(2)Sn IMC and the mechanical properties of Mg/Al joints.The blocky Mg_(2)Sn IMC formed in the Mg/SAC/Al joints without a Ni coating layer.The content of the Mg_(2)Sn IMC increased with increasing soldering temperature,but the joint strength decreased.The joint without a Ni coating layer fractured at the blocky Mg_(2)Sn IMC in the solder,and the maximum shear strength was 32.2 MPa.By pre-plating Ni on the Mg substrate,formation of the blocky Mg_(2)Sn IMC was inhibited in the soldering temperature range 240–280℃and the joint strength increased.However,when the soldering temperature increased to 310℃,the blocky Mg_(2)Sn IMC precipitated again in the solder.Transmission electron microscopy showed that some nano-sized Mg_(2)Sn IMC and the(Cu,Ni)_(6)Sn_(5)phase formed in the Mg(Ni)/SAC/Al joint soldered at 280℃,indicating that the Ni coating layer could no longer prevent diffusion of Mg into the solder when the soldering temperature was higher than 280℃.The maximum shear strength of the Mg(Ni)/SAC/Al joint was 58.2 MPa for a soldering temperature of 280℃,which was 80.7%higher than that of the Mg/SAC/Al joint,and the joint was broken at the Mg(Ni)/SAC interface.Pre-plating Ni is a feasible way to inhibit formation of IMCs when joining dissimilar metals.
基金Supported by National Natural Science Foundation of China (Grant No.51775141)Heilongjiang Touyan Innovation Team Program。
文摘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.
基金The research was supported by the National Natural Science Foundation of China(Grant No.52105331)the Shenzhen Science and Technology Innovation Committee(Grant No.JSGG20201102154600003,GXWD20220818163456002,JCYJ20210324124203009).
文摘In recent years,the rapid development of the new energy industry has driven continuous upgrading of high-density and high-power devices.In the packaging and assembly process,the problem of differentiation of the thermal needs of different modules has become increasingly prominent,especially for small-size solder joints with high heat dissipation in high-power devices.Localized soldering is con-sidered a suitable choice to selectively heat the desired target while not affecting other heat-sensitive chips.This paper reviews several local-ized soldering processes,focusing on the size of solder joints,soldering materials,and current state of the technique.Each localized solder-ing process was discovered to have unique characteristics.The requirements for small-size solder joints are met by laser soldering,microres-istance soldering,and self-propagating soldering;however,laser soldering has difficulty meeting the requirements for large heat dissipation,microresistance soldering requires the application of pressure to joints,and self-propagating soldering requires ignition materials.However,for small-size solder junctions,selective wave soldering,microwave soldering,and ultrasonic soldering are not appropriate.Because the magnetic field can be focused on a tiny area and the output energy of induction heating is large,induction soldering can be employed as a significant trend in future research.
基金the National Natural Science Foundation of China(Grant No.52075125,No.52105331)the Shenzhen Science and Technology Innovation Committee(Grant No.JCYJ20210324124203009,No.JSGG20201102154600003,No.GXWD20220818163456002)+1 种基金Special Fund for Science and Technology Innovation Strategy of Guangdong Province(Grant No.pdjh2022b0570)Sustainedly Supported Fundation by National Key Laboratory of Science and Technology on Space Microwave under Grant HTKJ2022KL504011,and NIO University Programme(NIO UP).
文摘The electronic product has gravitated towards component miniaturization and integration, employment of lead-free materials, and low-temperature soldering processes. Noble-metal aerogels have drawn increasing attention for high conduction and low density. However,the noble metal aerogels with outstanding solderability were rarely studied. This work has successfully synthesized an aerogel derived from silver nanowires(AgNWs) using a liquid phase reduction method. It is found that the noble metal aerogels can be made into diverse aerogel preformed soldering sheets. The influence of bonding temperature(150-300 ℃), time(2-20 min), and pressure(5-20 MPa) on the joint strength of the AgNWs aerogel affixed to electroless nickel/silver copper plates were investigated. Additionally, the AgNWs aerogel displays almost the same shear strength for substrates of various sizes. In a word, this study presents a flux-free, high-strength, and adaptable soldering structural material.
文摘The tensile properties of Sn-9Zn-xAg-ySb;{(x, y) = (0.2, 0.6), (0.2, 0.8), (0.6, 0.2), (0.8, 0.2)} lead-free solders were investigated. All the test samples were annealed at 150°C for 1 hour. The tests are carried out at room temperature at the strain rate of 4.17 × 10<sup>-3</sup> s<sup>-1</sup>, 20.85 × 10<sup>-3</sup> s<sup>-1</sup>, and 208.5 × 10<sup>-3</sup> s<sup>-1</sup>. It is seen that the tensile strength increases and the ductility decrease with increasing the strain rate over the investigated range. From the strain rate change test results, the strain sensitivity values are found in the range of 0.0831 to 0.1455 due to the addition of different alloying elements.
基金financially supported by the National Natural Science Foundation of China(No.U0734006)Shenzhen Tongfang Electronic New Material Co.,Ltd
文摘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.
文摘In some situations, the accelerated life test on environmental stress for electronic products is not easily implemented due to various restrictions, and thus engineers are lacking of data of the product life test. Concerning this problem, environmental life of the printed circuit board(PCB) board is calculated by way of physics of failure. Influences of thermal cycle and vibration on PCB and its components are studied. Based on the analysis of force and stress between components and the PCB board in thermal cycle events and vibration events, four life computing models of pins and soldered dots are established. The miller damage ratio is used to calculate the accumulated damage of a pin or a soldered dot, and then the environment life of the PCB board can be determined by the first failed one. Finally, an example is used to illustrate the models and their calculations.
基金supported by the National Natural Science Foundation of China(No.50904035)
文摘This article explores tile effects of phosphorus addition on the wettability between Sn-9Zn solder alloy and Cu substrates, the oxidation behavior and the corrosion behavior of Sn-9Zn solder alloy. Spreading test was used to characterize the wettability of Sn-9Zn-xP solder alloys to Cu substrates. The oxidation and corrosion behaviors of Sn- 9Zn-xP solder alloys were determined by means of weight gaining, and secondary ion mass spectrometry was used to analyze the oxygen content. The role and mechanism of P in the solder alloys were also discussed. It is found that the addition of P can significantly improve the wettability of the solder alloys. Incorporating P into Sn-9Zn solder alloy obviously decreases the oxygen content and enhances the oxidation and corrosion resistance. Microstructure observations show that an appropriate amount of P can greatly refine coarse rod-like Zn-rich phases in Sn-gZn solder alloy.
基金Nanjing University of Technology for providing financial support under the BSCX grant No.200806
文摘To obtain novel intermediate temperature alloy solders with a melting temperature of 400-600°C,nominal(Ag-Cu28)-30Sn alloys without or with a trace addition(0.5 or 1.0 wt.%) of rare earth(RE) element La were prepared by mechanical alloying.The aim of this research is to investigate the effects of the addition of La on the microstructures,alloying process and melting properties of(Ag-Cu28)-30Sn alloys.The results show that the addition of La produces no new phase.A trace amount of La addition can effectively refine the grain size,but the excessive addition of 1.0 wt.% La inhibits the alloying process.The influence of La on the melting temperatures of solder alloys is negligible.However,the trace addition of 0.5 wt.% La can distinctly reduce the fusion zone and improve the melting property of(Ag-Cu28)-30Sn alloys.