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.

Mechanical and Electrical Properties of Some Sn-Zn Based Lead-Free Quinary Alloys

Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ features. The eutectic Sn-9Zn alloy is among them. This paper investigated the mechanical and electrical properties of Sn-9Zn-x (Ag, Cu, Sb);{x = 0.2, 0.4, and 0.6} lead-free solder alloys. The mechanical properties such as elastic modulus, ultimate tensile strength (UTS), yield strength (YS), and ductility were examined at the strain rates in a range from 4.17 10−3 s−1 to 208.5 10−3 s−1 at room temperature. It is found that increasing the content of the alloying elements and strain rate increases the elastic modulus, ultimate tensile strength, and yield strength while the ductility decreases. The electrical conductivity of the alloys is found to be a little smaller than that of the Sn-9Zn eutectic alloy.

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 cerium on microstructure and mechanical properties of Sn-Ag-Cu system lead-free solder alloys

The melting point, spreading property, mechanical properties and microstructures of Sn-3.0Ag-2.8Cu solder alloys added with micro-variable-Ce were studied by means of optical microscopy, scanning electron microscopy(SEM) and energy dispersive X-ray(EDX). The results indicate that the melting point of Sn-3.0Ag-2.8Cu solder is enhanced by Ce addition; a small amount of Ce will remarkably prolong the creep-rupture life of Sn-3.0Ag-2.8Cu solder joint at room temperature, especially when the content of Ce is 0.1%, the creep-rupture life will be 9 times or more than that of the solder joint without Ce addition; the elongation of Sn-3.0Ag-2.8Cu solder is also obviously improved even up to 15.7%. In sum, the optimum content of Ce is within 0.05%-0.1 %.

Effects of phosphorus addition on the properties of Sn-9Zn lead-free solder alloy

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.

Effects of Ag contents in Sn-xAg lead-free solders on microstructure,corrosion behavior and interfacial reaction with Cu substrate

The effects of Ag on the microstructure and corrosion behavior of pre-soldering Sn-xAg lead-free solders,and on the formation of intermetallic layer of the solders with Cu substrate were investigated.The Ag contents(x)were 0,3.0,3.5,4.0,and5.0 wt.%.The Ag content played a role in the morphology of Ag3 Sn phase in the solders.The microstructure analysis showed that theβ-Sn phase was surrounded by eutectic networks in the 3.0 Ag and 3.5 Ag solders and large plate-like Ag3 Sn formed in the 4.0 Ag and5.0 Ag solders.Nonetheless,the Ag content slightly impacted the corrosion behavior of the as-cast solders as characterized using potentiodynamic polarization test.After soldering,only a single layer of a Cu6 Sn5 intermetallic compound formed at the Sn-xAg/Cu interface.By comparison,the Cu6 Sn5 intermetallic layer of the Ag-doped solders was thinner than that of the 0Ag solder.The fine Ag3 Sn particles in the eutectic networks precipitating in the 3.0 Ag and 3.5 Ag solders effectively hindered the growth of Cu6 Sn5 grains compared to large plate-like Ag3 Sn in the 4.0 and 5.0Ag solders.

Formation of Bulk Intermetallic Compound AgaSn in Slowly-Cooled Lead-Free Sn-4.0 wt pct Ag Solders

Sn-Ag alloy system has been regarded as one of the most promising lead-free solder to substitute conventional Sn- Pb eutectic solder. But the formation of bulk Ag3Sn intermetallic compounds （IMCs） during reflow and post heat treatment significantly influences the performance of the solder joints. With an effort to clarify its microstructural evolution as a function of slow cooling rates, the fraction of bulk IMCs within the slowly solidified Sn-4.0 wt pct Ag solder was investigated by standard metallographic and compared with that detected by thermal analysis. It was found that the bulk IMCs fraction determined by thermal analysis corresponds quite well with the microstructure observation results. In accordance with the conventional solidification theory, the lower the applied cooling rate, the fewer the amount of bulk Ag3Sn IMCs formed in Sn-4.0 wt pct Ag alloy. In addition, Vickers hardness measurement results indicated that the relative coarse eutectic Ag3Sn IMCs distributing in the lamellar eutectic structure favored the improvement of the mechanical performance.

Effects of Ga,Al,Ag,and Ce multi-additions on the wetting characteristics of Sn-9Zn lead-free solder

An orthogonal method was used to evaluate the effects of Ga, Al, Ag, and Ce multi-additions on the wetting characteristics of Sn-9Zn lead-free solders by wetting balance method. The results show that the optimal loading of Ga, Al, Ag, and Ce was 0.2 wt.%, 0.002 wt.%, 0.25 wt.%, and 0.15 wt.%, respectively. Intermetallic compounds （IMCs） formed at the interface between Sn-9Zn-0.2Ga-0.002Al-0.25Ag- 0.15Ce solder and Cu substrate were investigated by scanning electron microscope （SEM） and energy dispersive spectroscopy （EDS） analysis. The SEM images illustrate that the IMCs can be divided into two portions from the substrate side to the solder side： a planar CusZns layer and an additional continuous scallop-like AgZn3 layer. The EDS analysis also shows that Ga segregates in the solder abutting upon the interface. X-ray photoelectron spectroscopy （XPS） and Auger electron spectroscopy （AES） of the surface components of Sn-9Zn-0.2Ga-0.002Al- 0.25Ag-0.15Ce solder indicate that Al aggregates at the surface in the form of Al203 protective fdm, which prevents the further oxidation of the solder surface. On the other hand, Ce aggregates at the subsurface, which may reduce the surface tension of the solder and improve the wettability in consequence.

Property alterations of Sn-0.6Cu-0.05Ni-Ge lead-free solder by Ag, Bi, In and Sb addition

The Sn-Cu-Ni-Ge solder is a strong challenger to the Sn-Ag-Cu（SAC） solders as a replacement for the Sn-Pb eutectic solder. This research investigated the effects of addition of Ag, Bi, In, and Sb on the physical properties of the Sn-0.6 Cu-0.05 Ni-Ge（SCNG） lead-free solder and the interfacial reaction with the Cu substrate. The melting behavior, microstructure, tensile strength, and wettability of the SCNG-x（x=Ag, Bi, In, Sb） solders were examined. The findings revealed that the introduction of Ag, Bi, In, and Sb minimally altered the solidus temperature, liquidus temperature, and tensile strength of the solder. However, the cooling behavior and solidified microstructure of the solder were affected by the concentration of the alloying elements. The wettability of the SCNG solder was improved with the doping of the alloying elements except Sb. The thickness of intermetallic layer was increased by the addition of the alloying elements and was related to the cooling behavior of the solder. The morphology of intermetallic layer between the SCNG-x solders and the Cu substrate was different from that of the typical SAC solders. In conclusion, alloying the SCNG solder with Ag, Bi, In or Sb is able to improve particular properties of the solder.

Effects of rapid solidification on the microstructure and microhardness of a lead-free Sn-3.5Ag solder

A lead-free Sn-3.5Ag solder was prepared by rapid solidification technology. The high solidification rate, obtained by rapid cooling, promotes nucleation, and suppresses the growth of Ag3Sn intermetallic compounds （IMCs） in Ag-rich zone, yielding fine Ag3Sn nanoparticulates with spherical morphology in the matrix of the solder. The large amount of tough homogeneously-dispersed IMCs helps to improve the surface area per unit volume and obstructs the dislocation lines passing through the solder, which fits with the dispersion-strengthening theory. Hence, the rapidly-solidified Sn-3.5Ag solder exhibits a higher rnicrohardness when compared with a slowly-solidified Sn-3.5Ag solder.

Influence of Cu content on microstructure,grain orientation and mechanical properties of Sn-xCu lead-free solders

The effect of Cu content on the microstructure,grain orientation and mechanical properties of Sn-xCu(x=0-4.0 wt.%)lead-free solder was studied.Results showed that added Cu induced the formation of intermetallic phases.Only theη-Cu;Sn;andε-Cu;Sn phases were present in theβ-Sn matrix.For all contents,the strongly preferred orientation of theβ-Sn phase was formed on the{001}plane.In Sn doped with 1.0 wt.%Cu,theη-Cu;Sn;phase exhibited the preferred orientation of{0001}plane,whereas doping with 3.0 or 4.0 wt.%Cu transformed the preferred orientation to the{010}plane.In addition,only the{0001}and{■}planes were present in theε-Cu;Sn phase.The high Cu contents contributed to an increased number of low-angle boundaries,high residual strain,tensile strength and microhardness.

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.

Wettability of Sn-Zn-Bi Based Lead-Free Solder with Rare Earths

Effect of different contents of La and Ga on the wettability and the mierostrueture of interface of Sn-8.9Zn- 2.7Bi trinary alloys was studied. The results show that different contents of La and Ga have significant effect on the wettability of Sn-Zn-Bi based lead-free solder under the condition of both atmosphere and nitrogen. By adding suitable amount of Ga, Cu and La to Sn-Zn-Bi solder, a new lead-free solder Sn-8.9Zn-2.7Bi- 1.0Ga-0.5Cu-0.2La with better wettability was prepared, which has a wetting angle of 25.1° to Cu.

Effect of a Trace of Bi and Ni on the Microstructure and Wetting Properties of Sn-Zn-Cu Lead-Free Solder

The microstructure and melting behavior of Sn-9Zn-2Cu （SZC） lead-free solder with 3 wt pct Bi and various amount of Ni additions were studied. The wetting properties and the interracial reaction of Sn-Zn-Cu with Cu substrate were also examined. The results indicated that the addition of 3 wt pct Bi could decrease the melting point of the solder and Ni would refine the microstructure and the rod-shape Cu5Zn8 phase changed into square-shape （Cu, Ni）5Zn8 phase. The addition of Bi, Ni greatly improved the wettability of SZC solder. In addition, the interracial phase of the solders/Cu joint was typical planar Cu5Zn8 in SZC-3Bi-INi alloy.

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.

Rapid directional solidification in Sn-Cu lead-free solder

An experimental study on the microstructures of a rapid directionally solidified metallo-eutectic Sn-Cu alloy was carried out. This material is an important alloy that is used as a lead-free solder. The results showed that the kinetic undercooling due to the rapid solidification process led to the formation of a pseudoeutectic zone, whereas the hypereutectic reaction produced the regular lamellar structure in the hypereutectic Sn-1.0Cu alloy. The corresponding arm spacing in the obtained lamellar phases decreased gradually with the increase of the applied cooling rate, which corresponded well with the prediction of a rapid directional solidification model.

Structure and Properties of Sn-9Zn Lead-Free Solder Alloy with Heat Treatment

The Sn-9Zn lead-free solder alloy was prepared by conventional casting technique then cold-rolled into long sheets of 1 mm thickness and 3 mm width. It was annealed at 80, 120 and 160°C for 60 min to investigate the effect of isochronal heat treatment on structure and mechanical properties of the cold rolled Sn-9Zn alloy. The results showed that, the crystallite size and lattice strain have opposite behavior with increasing annealing temperature due to recovery and recrystalization processes associated with the heat treatment process. Vickers micro-hardness number increases continuously from 155 to 180 MPa with increasing annealing temperature. Ultimate tensile strength (UTS) was also calculated. It was found that, it is equal to 61.4 MPa for the non annealed sample and slightly decreases to 60.5 and 58.2 MPa for samples annealed at 80 and 120°C, respectively. While, increases to 65.4 MPa for the sample annealed at 160°C. Also, ductility increases with increasing annealing temperature in opposite manor with the UTS. The new method for Micro-creep behavior as well as the creep rate calculated by this method has been characterized at room temperature.

Effects of rare earth element Ce on solderabilities of micron-powdered Sn-Ag-Cu solder

Several important properties of the micron-powdered Sn-Ag-Cu-Ce solder, including the spreadability, spreading ratio, wetting time, and melting point, were investigated for verifying the effects of rare earth element Ce on solderabilities of micron-powdered Sn-Ag-Cu solder. The solidus and the liquidus of the micron-powdered Sn-Ag-Cu-Ce solder are 193.6℃ and 218.4℃, respectively, about 28℃ and 3℃ lower than the melting point of the block Sn-Ag-Cu solder, which reminds the existence of the surface effect of the micron-powdered solder. By adding Ce into Sn-Ag-Cu alloy, its wetting time on pure copper can be obviously decreased. For the Sn-Ag-Cu-0.03%Ce, the soldering temperature is 250℃, and the wetting time on pure copper is close to 1s, with the soldering temperature approaching to 260℃, the wetting time is dropped to 0.8s, which is close to the wetting time, 0.68s, of Sn-Pb solder at 235℃.

Electromotive force measurements in liquid Ag-In-Pd lead-free alloys

Emf technique was employed to determine indium activities in the liquid Ag-In-Pd alloys using galvanic cells with yttria-stabilised-zirconia as solid electrolyte according to the scheme： kanthal/rhenium, Ag-In-Pd, In2O3 ｜ YSZ ｜ Ni, NiO, Pt. Composition and temperature measurement ranges were limited, because of very steep liquidus surface; 35 compositions for Xpd up to 0.3 were investigated and at temperatures from near-liquidus up to 1700 K. High temperature experiments required special moly furnace to be constructed with unique automatic gas supply system for fumace winding protective atmosphere. Emf readings were taken and recorded by automatic data acquisition system. Linear dependence of emf on temperature was observed for all compositions investigated, and results were approximated by straight line equa- tions. Then In activities were calculated using well-known relations and taking into account correction for thermoelectric power between kanthal and platinum. Results are to be used along with other existing data to perform assessment of the ternary system under accord.

La对Sn-Ag-Cu无铅钎料与铜钎焊接头金属间化合物的影响

研究微量稀土La在钎焊和时效过程中对Sn-3.0Ag-0.5Cu无铅钎料与铜基板的钎焊界面及钎料内部金属间化合物(IMC)的形成与生长行为的影响。结果表明:钎焊后钎焊界面形成连续的扇形Cu6Sn5化合物层,其厚度随La含量的增加而减小;在150℃时效100h后,连续的Cu3Sn化合物层在Cu6Sn5化合物层和铜基板之间析出,且Cu6Sn5层里嵌有Ag3Sn颗粒;界面金属间化合物总厚度随时效时间的延长而增厚,且在相同时效条件下随La含量的增加而减小;时效过程中金属间化合物生长动力学的时间系数(n)随着La含量的增加逐渐增大;钎焊后钎料内部Ag仍以共晶形式存在,时效后Ag3Sn颗粒沿钎料内部的共晶组织网络析出。