In this study, we designed and manufactured an ideal electromigration testing device for soldering joints to solve the reliability problems caused by temperature and current density changes in the electromigration processes of micro solder joints. We analyzed the effects of temperature and current density on the electromigration β-Sn (single-crystal β-Sn grain) of Sn2.5Ag0.7Cu0.1RE/Cu solder joints, the relationship between the grain orientation and interfacial IMC (intermetallic compound) growth of Sn2.5Ag0.7Cu0.1RE/Cu solder joints, and the mechanical properties of solder joints. The results showed that the angle θ between the c-axis of the β-Sn grain and the current direction for the Sn2.5Ag0.7Cu0.1RE/Cu solder joint gradually decreased to 8.2° when the temperature increased to 150 °C, which accelerated the diffusion of Cu atoms and Cu substrate dissolution. The recrystallization and grain growth of Cu6Sn5 (An intermetallic compound formed by the fusion of copper and tin in a ratio of six to five) grains in the anode region promoted electromigration polarity. Compared with the initial state, the shear strength decreased to 11 MPa, a decrease of 61.3%, the fracture position shifted from the top of the IMC at the cathode interface to the root of the IMC at the cathode interface, and the fracture mode changed from ductile fracture to brittle fracture. With an increase in the current density to 1.1 × 104 A/cm2, θ decreased to 3.2°. In addition, we observed the recrystallization of Cu6Sn5 grains in the anode region and an increase in the grain length and diameter to 6.8–31.9 μm, which further promoted electromigration polarity. Compared with the initial state, the shear strength decreased by 72.5% to 7.8 MPa, and the fracture position shifted from the top of the IMC at the cathode interface to the root of the IMC at the cathode interface. Additionally, the fracture mode changed from ductile to brittle fracture.

With the trends of miniaturization and high integration of electronic packaging, there has been an urgent demand to develop lead-free solders with high strength,toughness and conductivity, In this study, a scheme of Al2O3 –modified nanoparticles reinforced Sn1.0Ag0.5Cu (SAC105) composite solder was designed.First, a novel amorphous carbon core–shell structure and nickel plating modified on Al2O3 (C/Ni/Al2O3)was prepared by the electroless plating method. Subsequently, C/Ni/Al2O3 as reinforcement was added to the SAC105 solder matrix with ultrasonic stirring. The morphology and interface of C/Ni/Al2O3 were discussed. Moreover, the Microstructure and mechanical properties of the composite solders were aslo investigated. The results showed that C/Ni/Al2O3 nanoparticles prepared by electroless plating method was deposited on the surface of Al2O3, amorphous carbon layer thickness was approximately 6.56nm, the interface of Ni-Al2O3 was a semi-coherent interface, which was a good metallurgical bond. In a certain addition range of C/Ni/Al2O3 (0−0.5mass%), the conductivity and wettability of the composite solder gradually increased compared to that of the plain Sn1.0Ag0.5Cu solder. The mechanical properties of the composite solder aslo gradually increased with added reforcement (0−0.5mass%) to that of solder matrix. The fracture mode also transformed from a ductile−brittle mixed fracture consisting of dimples and cleavage planes to the ductile fracture of consisting dimples.

Ni-plated ZrO2 reinforced alloy was prepared by thermal decomposition and reduction method, and Ni-plated ZrO2 reinforced Sn1.0Ag0.5Cu composite filler metal was prepared by powder metallurgy method. The surface metallization of ZrO2 nanoparticles and its effect on the microstructure, properties and brazing joints of Sn1.0Ag0.5Cu composite filler metal were studied. The results show that the particle size and agglomeration of ZrO2 decrease after mechanical pretreatment. The Ni-plated ZrO2 enhanced phase is successfully prepared by thermal decomposition and reduction method. The Ni particles are uniformly attached to the surface of ZrO2 with a spacing of 8-11 nm, and the interface between ZrO2((1) over bar 02) and Ni(11 (1) over bar) shows a semi-coherent relationship. Resistivity of Ni/ZrO2-Sn1.0Ag0.5Cu composites is not significantly affected by adding a proper amount of nickel-plated ZrO2, but the wettability and tensile strength are improved. The tensile strength and shear strength of brazed joint of Ni/ZrO2-Sn1.0Ag0.5Cu composite filler metal reach the peak when the adding amount of ZrO2 reinforcing phase is 0.7wt%, which are increased by 43.3% and 45%, respectively, compared with those of the matrix material. With the addition of Ni/ZrO2 reinforcing phase, the fracture position of the brazing joint of the composite filler metal moves from the interfacial IMC layer to the side near the brazing seam in the transition zone, and the fracture mechanism gradually changes from the mixed tough-brittle fracture to the ductile fracture dominated by dimple.

针对微焊点服役下的电迁移可靠性检测,设计制造了满足焊点在理想电迁移环境下的试验装置.结果表明:通过热分解法制备 Ni-GNSs增强相,得到的 Ni-GNSs 增强 Sn2.5Ag0.7Cu0.1RE/Cu 钎焊接头能有效抑制电迁移现象的发生.在电加载条件下,随电流密度升高,Ni-GNSs 增强 Sn2.5Ag0.7Cu0.1RE/Cu 接头阳极区界面金属间化合物(IMC)由起伏扇贝状转变为平坦厚大的板状,并出现了明显 Cu3Sn;阴极区界面 IMC 由锯齿状转变为薄条状,且有明显空洞裂纹.钎焊接头断裂位置从阴极界面 IMC/钎缝的过渡区向阴极界面IMC迁移,断裂方式由韧性断裂向脆性断裂转变,剪切强度明显下降.

Aiming at the thermomigration problem caused by the large temperature gradient (TG) of micro-soldering joints, a constant temperature thermomigration device with temperature control function was designed and manufactured. This paper studied the polarity phenomenon, crystallographic characteristics, and interfacial intermetallic compound (IMC) growth kinetics of Ni-GNSs reinforced Sn2.5Ag0.7Cu0.1RE/Cu solder joints under thermomigration. The results indicate that Ni-GNSs reinforced Sn2.5Ag0.7Cu0.1RE/Cu solder joints exhibited a significant thermomigration polarity phenomenon under the conditions of TG >= 1000 degrees C/cm and theta <= 43.5. between the c-axis and TG of beta-Sn grains. At the cold end of the solder joint, the Cu6Sn5 phase at the interface gradually thickens and forms Cu3Sn phase on the substrate side, while microcracks expanded and gradually developed into macrocracks. At the hot end of the interface, the Cu6Sn5 phase gradually dissolved. The growth of the Cu3Sn phase was accompanied by "Kirkendall voids" that formed cracks at the interface between the joint and the solder until a "fully IMC solder joint" was formed. The growth of Cu6Sn5 IMC at the solder joint interface came before that of Cu3Sn IMC. The average temperature and temperature gradient of the solder joint were correlated with the growth of Cu3Sn IMC, leading to the formation of interface Cu3Sn IMC due to the oversaturation of Cu atoms. The addition of 0.05 wt% Ni-GNSs refines the grain structure and increases the activation energy for the growth of Cu6Sn5 and Cu3Sn IMC at the cold end of the solder joint, suppressing the thermomigration polarity phenomenon.

Electromigration is one of the most important research issues affecting the reliability of solder joints. Current-induced Joule heating affects the electromigration behavior of solder joints. Solder joints with different cross-sectional areas were designed to obtain different Joule heating properties. The effects of the interfacial intermetallic compound (IMC) and mechanical properties of Sn58Bi/Cu solder joints were studied for different Joule heating properties. The results showed that as the cross-sectional area of the Sn58Bi/Cu solder joints increased, the Joule heating of the joint increased. The anode IMC thickness of the joint thickened and transformed into a planar shape. The Bi migrated to the anode region to form a Bi-rich layer and gradually increased in thickness. The cathode IMC thickness first increased, then decreased, and gradually dissolved. The Sn-rich layer formed near the solder side and gradually increased in thickness, with microcracks occurring when the cross-sectional area of the joint increased to 0.75 mm2. The joint shear fracture path moved from the soldering zone near the cathode IMC layer to the interfacial IMC layer. The fracture mechanism of the joint changed from a mixed brittle/tough fracture, dominated by deconstruction and secondary cracking, to a brittle fracture dominated by deconstruction. The joint shear strength was reduced by 60.9% compared to that in the absence of electromigration.

To solve the electromigration problem of micro−electronic connection solder joints, an ideal electromigration tester was designed, and the thickness of the intermetallic compounds (IMCs), average void diameter, grain orientation, failure, shear strength, and fracture path of Sn2.5Ag0.7Cu0.1RE0.05Ni−GNSs/Cu solder joints under constant−temperature electromigration were studied. The results indicate that the solder joints show evidence of typical electromigration polarity in the asymmetric growth of interfacial IMCs on the anode and cathode sides under the conditions of a current density ≥7 × 103 A/cm2 and an included angle between the c−axis of the β−Sn grains and the current direction θ ≤ 53.2°. The anode−side interfacial IMC is dominated by a Cu6Sn5 phase with a gradually increasing thickness, forming a Cu3Sn phase and showing evidence of microcracks. The Cu6Sn5 phase of the cathode−side interfacial IMC is gradually completely dissolved, and the growth of the Cu3Sn phase is accompanied by the formation of Kirkendall voids. The anisotropic diffusion of Cu atoms in the β−Sn of the micro−solder joints causes increased solder joint resistance and reduced shear strength. The shear fracture path of the solder joints moves from the cathode side near the IMC solder seam to the Cu3Sn interface. The shear fracture mechanism changes from ductile transgranular fracture dominated by β−Sn dimples to brittle fracture dominated by interfacial IMC cleavage and slip steps.

The trend toward miniaturized and highly integrated chip packaging has created a pressing need for lead-free solders with high strength, toughness, and conductivity. In this paper, we designed a scheme of Al2O3-modified nanomaterial-reinforced low silver Sn1.0Ag0.5Cu (SAC105) solder matrix. To begin with, a novel amorphous carbon and nickel core–shell structure plating modified on Al2O3 (C/Ni/Al2O3) were prepared by the electroless plating method. Then, the nano-C/Ni/Al2O3 particle as reinforcement phase was mixed into the matrix solder alloy by ultrasonic vibration stirring. Finally, the morphology and relationship between coated carbon, deposited nickel and original solder interface were analyzed. The microstructure and main properties of the modified solders were also investigated. The experimental results suggested that amorphous carbon and nickel film were prepared on the surface of Al2O3 by electroless plating method. The outer layer of nano-Al2O3 was coated with non-uniform thickness of nickel and carbon coatings. The mass percentage of amorphous carbon was about 3.50