Preventing formation of intermetallic compounds in ultrasonic-assisted Sn soldering of Mg/Al alloys through pre-plating a Ni coating layer on the Mg substrate

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.

A review of soldering by localized heating

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.

Interfacial reaction behavior and mechanical properties of 5A06 Al alloy soldered with Sn-1Ti-xGa solders at a low temperature

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.

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

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

Effect of Strain Rate on Tensile Behavior 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 Solder Alloys

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 × 10-3 s-1, 20.85 × 10-3 s-1, and 208.5 × 10-3 s-1. 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.

Effect of diode-laser parameters on shear force of micro-joints soldered with Sn-Ag-Cu lead-free solder on Au/Ni/Cu pad

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.

Effects of nano-sized Ag reinforcing particulates on the microstructure of Sn-0.7Cu solder joints

Composite solders were prepared by mechanically dispersing different volumes of nano-sized Ag particles into the Sn-0.7Cu eutectic solder. The effects of Ag particle addition on the microstructure of Sn-0.7Cu solder joints were investigated. Besides, the effects of isothermal aging on the microstructural evolution in the interfacial intermetallic compound （IMC） layer of the Sn-0.7Cu solder and the composite solder reinforced with 1vol% Ag particles were analyzed, respectively. Experimental results indicate that the growth rate of the interfacial IMC layer in the Ag particles reinforced composite solder joint is much lower than that in the Sn-0.7Cu solder joint during isothermal aging. The Ag particles reinforced composite solder joint exhibits much lower layer-growth coefficient for the growth of the IMC layer than the corresponding solder joint.

Preparation and Properties of Particle Reinforced Sn-Zn-based Composite Solder

Particle reinforced Sn-Zn based composite solders were obtained by adding Cu powders to Sn-9Zn melts. The microstructure analysis reveals that in situ CusZn8 particles are formed and distributed uniformly in the composite solders. The strength and plasticity of the composite solders were improved, and creep resistance was considerably enhanced. The wettability of these composite solders is also better than that of Sn-9Zn.

Influences of Ag and Au Additions on Structure and Tensile Strength of Sn-5Sb Lead Free Solder Alloy

It is important, for electronic application, to decrease the melting point of Sn-5Sb solder alloy because it is relatively high as compared with the most popular eutectic Pb-Sn solder alloy. Adding Au or Ag can decrease the onset melting temperature （233℃） of this alloy to 203,5℃ and 216℃, respectively. The results indicate that the Sn-5Sb-i.5Au alloy has very good ultimate tensile strength （UTS）, ductility, and fusion heat, which are better than both those of the Sn-5Sb-3.SAg and Sn-5Sb alloys. The formation of intermetallic compounds （IMCs） AuSn4 and Ag3Sn enhanced the SbSn precipitates in the solidification microstructure microstructure stability, while retained the formation of thus significantly improved the strength and ductility For all alloys, both UTS and yield stress （σy） increase with increasing strain rate and decrease with increasing temperature in tensile tests, but changes of ductility are generally small with inconsistent trends.

An exPerimental study of effect of solder joint geometry on thermal cycle life in SMT

The geometry of solder joint in SMT is one of the important factors whichdetermine the solder joint reliability. In this study, a type of solder joint specimen has beendesigned and is subjected to thermal cycling to failure between -55 ℃ to +125 ℃ with a 36℃/min heating and cooling rate and 10 min temperature holding times. The solder jointgeometry is castellated and controlled with different solder fillet shape and stand off height.A statistical analysis of the scattered thermal cycle lives of solder joints by two parameterWeibull's probability density function has been carried out in this paper. The experimentalresults show that the more reliable solder joint geometry has flat or slight convex solderfillet with a stand off height larger than 0.1 mm. The results may be the recommendedguideline to design optimal solder joint geometry.

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

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

Solder joint geometry of tin-lead alloy and its application in electronic packaging

By employing the minimum energy theorem, the Potential energy controlling equation, which consists of surface energy and gravitational energy for molten meniscus, was investigated. The soder joint geometry of molten tin-lead soder alloy for chip component and thin quad flat package were simulated with finite element method. The simulation results 0f solder joint geometry are coincident well with the experimental results. The solder joint geometry was applied to study the solder joint reliability for chip component RC3216.The thermal cycling tests revealed that the solder joint geometry plays an important ro1e in solder joint reliability.

THE DESIGN OF AN INTEGRATED SYSTEM FOR PREDICTING AND ANALYZING SOLDER JOINT SHAPE AND RELIABILITY INSMT

Solder joint reliability is one of critical problems detemining whether Sirface Mount Technology (SMT) can be used in the prohotion of important electronic products. Optimizing solder joint shape is one of effective ways to improve SMT solder joint reliability.In this paper. based on the theorem of minimum potential energy, an energy model of 3 - D solder joint shape is established,and the forma- tion of solder joint is numerically simulated by Surface Ecolver program. On the basis of the prediction of SMT solder joint shape,the mechanical model of analyzing solder joint reliability is established. An elasto - plasto - creep mateial model and its mechanical constitutive equaton are established for SnPb solder alloy, and the stress/strain response of SMT solder joint under thermal cyclical loabing is ana- lyzed with nonlinear 3 - D FEM. The fatigue life of solder joint is predicted according to Coffin- Manson fatigue life model. An integrated system for Predicting and analyzing SMT solder joint shape and reliability(PSAR) is developed.The system can analyze efficiently SMT solder joint reliability with the variation of structural parameters in the joint and give the optimal structure.

Effect of Ce on solderability of Sn-Cu-Ni solder

Abstract A small amount of rare earth Ce was added to Sn-Cu-Ni solder alloy, and the solderability of Sn-0. 5Cu-0. 05Ni- xCe solders on Cu and Au/Ni/Cu substrates was determined by the wetting balance method. The effects of atmosphere, temperature, substrate, and Ce addition on the solderability of Sn-Cu-Ni-xCe solder were studied, respectively, and Auger electron spectroscopy （ AES） analysis in the depth direction of the alloy was carried out to discuss the effect of Ce addition on the solderability. The results indicate that the greatest improvement on the solderability of Sn-Cu-Ni-xCe is obtai^d with around O. 05wt. % -0. 07wt. % Ce addition, for Ce element keeps high content in a specific area in the depth direction from the surface of Sn-Cu-Ni alloy, which decreases the surface tension of molten solder. It is also found that the solderability of Sn-Cu-Ni-xCe solder on Au/Ni/ Cu substrate is better than that on Cu substrate. In N2 atmosphere, the wetting times of Sn- Ca-Ni-xCe alloys are reduced by 10% - 35% , below 1 s at 260 ℃ on Ca substrate, and about 1s at 250 ℃ on Au/Ni/Ca substrate.

Solder Charge连接器连锡故障解决方案

Solder charge连接器(SBGA)为高速多引脚互联器件,应用于多种通讯产品的子母板间高速互联。在SMT生产过程中,其故障率一直高于同类焊球型封装BGA器件,主要故障表现为相邻两排引脚短路,且故障率表现与来料批次强相关,通过多种工艺方案不能完全解决连锡问题。通过分析Solder charge连接器结构和材料,找到器件连锡的根因,提出了此类器件的设计和焊接改善方案,并进行了实际生产验证,为业界Solder charge连接器(SBGA)类器件焊接提供了可行的解决方案。

Effect of Ag and Ni on the melting point and solderability of SnSbCu solder alloys

To improve the properties of Sn10Sb8Cu solder alloy, two new solders （SnSbCuAg and SnSbCuNi） were formed by adding small amounts of Ag or Ni into the solder alloy. The results show that the melting point of the SnSbCuAg solder alloy decreases by 14.1℃ and the spreading area increases by 16.5% compared to the matrix solder. The melting point of the SnSbCuNi solder alloy decreases by 5.4℃ and the spreading area is slightly less than that of the matrix solder. Microstructure analysis shows that adding trace Ag makes the melting point decline due to the dispersed distribution of SnAg phase with low melting point. Adding trace Ni, Cu6Sn5 and （Cu, Ni）6Sn5 with polyhedron shape on the copper substrate can be easily seen in the SnSbCuNi solder alloy, which makes the viscosity of the melting solder increase and the spreading property of the solder decline.

Solderability of Electrodeposited Fe-Ni Alloys with Eutectic SnAgCu Solder

Solderabilities of electrodeposited Fe-Ni alloys with SnAgCu solder were examined by wetting balance measurements and compared to those of pure Ni and pure Fe platings. Excellent solderability was found on the Ni-52Fe plating as both the wetting force and kinetics approached or exceeded those on the pure Ni. However, upon further increase in Fe content to 75 at. pct, the solderability of the alloy was severely degraded even though it was still better than that of the pure Fe plating. X-ray photoelectron spectroscopy showed that such a strong dependence of solderability on Fe content is related to the much thinner, incomplete oxide coverage of Ni-rich plating surface.

Solderability and intermetallic compounds formation of Sn-9Zn-xAg lead-free solders wetted on Cu substrate

The eutectic Sn-9Zn alloy was doped with Ag （0 wt.%-1 wt.%） to form Sn-9Zn-xAg lead-free solder alloys. The effect of the addition of Ag on the microstructure and solderability of this alloy was investigated and intermetallic compounds （IMCs） formed at the solder/Cu interface were also examined in this study. The results show that, due to the addition of Ag, the microstructure of the solder changes. When the quantity of Ag is lower than 0.3 wt.%, the needle-like Zn-rich phase decreases gradually. However, when the quantity of Ag is 0.5 wt.%-1 wt.%, Ag-Zn intermetallic compounds appear in the solder. In particular, adding 0.3 wt.% Ag improves the wetting behavior due to the better oxidation resistance of the Sn-9Zn solder. The addition of an excessive amount of Ag will deteriorate the wetting property because the gluti- nosity and fluidity of Sn-9Zn-（0.5, 1）Ag solder decrease. The results also indicate that the addition of Ag to the Sn-Zn solder leads to the precipitation of ε-AgZn3 from the liquid solder on preformed interracial intermetallics （CusZn8）. The peripheral AgZn3, nodular on the Cu5Zn8 IMCs layer, is likely to be generated by a peritectic reaction L ＋ γ-Ag5Zns→AgZn3 and the following crystallization of AgZn3.

Effects of Ni-Doping on Microstructures and Properties of Zn-20Sn High-Temperature Lead-Free Solders

In the present work, the effect of Ni doping on the microstructures and properties of Zn-20 Sn high temperature lead-free solder has been investigated. Interestingly,Ni was present as the form of Ni-Zn compounds in the microstructure of Zn-20 Sn-xNi alloy.When the Ni-doping amount was 0.2~0.4 wt.%, the presence of δ phase was found, and when the doping amoun was 0.8 wt.%, the presence of γ phase was observed. With the increase of Ni content, the liquidus temperature increased but the solidus temperature did not change obviously. In addition, the microhardness and electrical resistivities of Zn-20 Sn-xNi solder increased gradually. And the spreading area and shear strength increased firstly but decreased afterwards. When the content of Ni was 0.4 wt.%, the spreading area and shear strength of solder reached to be maximum. After the addition of 0.4 wt.% Ni, the microstructure of the interfacial intermetallic compound(IMC) layer of the interface didn't change, but the total thickness of the IMC layer reduced. The δ-phase was embedded in the grain boundary of ε-Cu Zn5, which hindered the diffusion of atoms. The thickness of IMC layer at the interface reduced, which led to the improvement of the shear strength of the interface.

Effects of Bi and rare earth metal on the microstructure and properties of Zn-based high-temperature solder

A novel Zn-based high-temperature solder was developed to join copper/steel at moderate temperature. The effects of Bi and rare earth metal on the microstructures , wettability of solders as well as the mechanical properties of solder joints were investigated. The results indicated that with the addition of Bi into Zn-Cu-Sn （ZCS） alloy, significant improvement in wettability is realized. When the content of Bi element is 1.5 wt. % in the solder, the spreading area researched over 200 mm^2. Furthermore, with the addition of RE, refined primary ε-CuZn5 phases were formed and the shear strength of the solder joint was largely improved.