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.

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.

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.

Al 1060/Pure Iron Clad Materials by Vacuum Roll Bonding and Their Solderability

Al 1060/pure iron clad materials were produced by vacuum roll bonding. The effects of preheating temperature, vacuum roll reduction and initial thickness of the A11060 sheet on the metal interface and bonding strength were investigated. The interfacial microstructure was investigated and the mechanical properties of the joint were evaluated by shear testing. The bonding strength of the clad materials was generally enhanced by increasing the total reduction or preheating temperature, which caused the metal interface to flatten. No obvious reaction or diffusion layer was observed at the interface between Al 1060 and pure iron. The bonding strength increased with decreasing the initial thickness of the Al 1060 sheets. The Al 1060/pure iron clad materials were soldered with Zn-Al alloy by using an ultrasonic-assisted method. Strong bonding of the Al 1060 layer and Al 7N01 was realized without obvious Al 1060 dissolution or effect on the initial interface of Al 1060/pure iron clad materials by soldering at relatively low temperature.

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.

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.

Fluxless bonding with silver nanowires aerogel in die-attached interconnection

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.

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.

Research Progress in Solderable Black Pad of Electroless Nickel/Immersion Gold

Electroless nickel/immersion gold (ENIG) technology is widely used as one of the surface final finish for electronics packaging substrate and printed circuit board (PCB), providing a protective, conductive and solderable surface. However, there is a solder joint interfacial brittle fracture (or solderability failure) of using the ENIG coating. The characteristics and the application of ENIG technology were narrated in this paper. The research progress on the solderability failure of ENIG was introduced. The mechanism of 'black pad' and the possible measure of eliminating or alleviating the 'black pad' were also introduced. The development direction and market prospects of ENIG were prospected.

选择性波峰焊工艺研究要点

主要介绍了选择性波峰焊的现状,分析了选择性波峰焊的工艺特点,提出了进行选择性波峰焊工艺研究的要点。

INTERACTION BETWEEN Cu AND LIQUID Sn(II)——SEM OBSERVATION OF INTERMETALLIC GROWTH

The features of Cu_6Sn_5 growing slowly at lower temperature and growing rapidly up over 350℃,and or Cu_3Sn growing at higher temperatures,bave been detailedly observed under SEM.The increase of Pb content seems to inhibit sequentially the growth of Cu_6Sn_5 in Pb-Sn alloy.

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。

低成本倒装片组装的断裂力学分析

本文论述了不同厚度的印制电路板上不完全下填充倒装芯片的焊点可靠性,着重强调了对不同裂纹(剥离)长度,焊点角上与温度相关的应力和塑料应变的确定另外,陈述了采用断裂力学法求得在下填充物和焊料掩膜之间界面处,裂纹尖端的应变能释放率和相角。

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 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 rare earth La on the microstructure and melting property of(Ag-Cu_(28))-30Sn alloys prepared by mechanical alloying

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.

Effect of Microalloying on Wettability, Oxidation and Solidification Morphology of Sn-9Zn Alloy

Eutectic alloy Sn-9Zn is an attractive candidate for lead-free solders. However, its wettability to copper is poor thus,its development was limited. Effects of less than 1% (mass fraction) additions of mischmetal consisting mainly of La and Ce, heavy rare earth Y, pure P, Al, Mg and Ti elements on the wetting/adhesion behavior of Sn-9Zn alloy to copper, as well as the associated oxidation and solidification morphology of this alloy were examined. The results show that harmful effect on the wettability can be found when adding Al and Ti elements, while the wettability can be improved slightly by adding Mg and Y elements. The adhesion of the alloy to copper can be decreased by Mg element. The RE and P are found to significantly improve the wettability. In addition, oxidation of the alloy can be increased by adding RE, while little effect on the oxidation behavior can be found by adding P element. As-solidified Sn-9Zn alloy has a rough surface with protrusions and cavities shaped by coarse needle-like crystallites, while the Sn-37Pb sample has a rather smooth surface, which indicates the different solidification behavior of Sn-9Zn alloy and the Sn-37Pb one. The additions of the different elements investigated in this study do not alter Sn-9Zn's as-solidified morphology.