Sn-9Zn Solder Research Articles

Microstructure, joining mechanism, mechanical properties and optimization of inactive solder (Sn9Zn) in low temperature ultrasonic soldering of AlN ceramics and 2024Al

With the development of the electronic packaging industry, there is an increased demand for enhanced strength in DBA substrates. Ultrasonic soldering technology allows low-temperature joining of ceramic-metal materials under ambient air conditions. In this paper, we successfully achieved the joining between AlN ceramics and 2024Al using Sn9Zn solder and ultrasonic soldering technique, while also analyzing the joining mechanism through Comsol software simulations. It was observed that under the appropriate ultrasonic amplitude and frequency, the Sn9Zn solder exhibited complete wetting with both base materials, resulting in reliable joints. Building upon this finding, the conventional Sn9Zn solder was further optimized by adding Sb element. The addition of Sb element led to the formation of Zn4Sb3 phase and β-Sn(Sb) phase with Sb acting as solute. Among them, the generation of β-Sn(Sb) solid solution phase effectively improved the joint strength. The maximum joint strength was achieved at an average value of 75.066 MPa when the Sb content reached 1 wt. %. At this point, the failure occurred within the AlN ceramic base material.

Effects of soldering temperature and preheating temperature on the properties of Sn–Zn solder alloys using wave soldering

Purpose This study aims to address the problem of low-temperature wave soldering in industry production with Sn-9Zn-2.5 Bi-1.5In alloys and develop qualified process parameters. Sn–Zn eutectic alloys are lead-free solders applied in consumer electronics due to their low melting point, high strength, and low cost. In the electronic assembly industry, Sn–Zn eutectic alloys have great potential for use. Design/methodology/approach This paper explored developing and implementing process parameters for low-temperature wave soldering of Sn–Zn alloys (SN-9ZN-2.5BI-1.5 In). A two-factor, three-level design of the experiments experiment was designed to simulate various conditions parameters encountered in Sn–Zn soldering, developed the nitrogen protection device of waving soldering and proposed the optimal process parameters to realize mass production of low-temperature wave soldering on Sn–Zn alloys. Findings The Sn-9Zn-2.5 Bi-1.5In alloy can overcome the Zn oxidation problem, achieve low-temperature wave soldering and meet IPC standards, but requires the development of nitrogen protection devices and the optimization of a series of process parameters. The design experiment reveals that preheating temperature, soldering temperature and flux affect failure phenomena. Finally, combined with the process test results, an effective method to support mass production. Research limitations/implications In term of overcome Zn’s oxidation characteristics, anti-oxidation wave welding device needs to be studied. Various process parameters need to be developed to achieve a welding process with lower temperature than that of lead solder(Sn–Pb) and lead-free SAC(Sn-0.3Ag-0.7Cu). The process window of Sn–Zn series alloy (Sn-9Zn-2.5 Bi-1.5In alloy) is narrow. A more stringent quality control chart is required to make mass production. Practical implications In this research, the soldering temperature of Sn-9Zn-2.5 Bi-1.5In is 5 °C and 25 °C lower than Sn–Pb and Sn-0.3Ag-0.7Cu(SAC0307). To the best of the authors’ knowledge, this work was the first time to apply Sn–Zn solder alloy under actual production conditions on wave soldering, which was of great significance for the study of wave soldering of the same kind of solder alloy. Social implications Low-temperature wave soldering can supported green manufacturing widely, offering a new path to achieve carbon emissions for many factories and also combat to international climate change. Originality/value There are many research papers on Sn–Zn alloys, but methods of achieving low-temperature wave soldering to meet IPC standards are infrequent. Especially the process control method that can be mass-produced is more challenging. In addition, the metal storage is very high and the cost is relatively low, which is of great help to provide enterprise competitiveness and can also support the development of green manufacturing, which has a good role in promoting the broader development of the Sn–Zn series.

Effect of temperature on joint quality in wave soldering of Sn-9Zn-2.5Bi-1.5In lead-free solder alloy

SnZn (tin‑zinc) solder has been regarded as a promising lead-free solder material with a low melting point of 198 °C, serving as a suitable alternative to both SnPb solder due to its lack of hazardous substances and Sn-Ag-Cu solder because of the high cost associated with silver. Nonetheless, its susceptibility to oxidation hinders solderability and increases soldering defects such as bridging, insufficient fillings, and voids, limiting its use in commercial production. Devices designed with through-hole technology, in contrast to surface-mounted ones, continue to exhibit superior interconnection reliability in such applications. In this investigation on wave soldering, a newly developed lead-free solder, composed of 87% tin, 9% zinc, 2.5% bismuth, and 1.5% indium by weight, was employed under two conditions related to nitrogen content: 1) Ensuring that static oxygen content remained below 3000 ppm. 2) Maintaining soldering section oxygen content below 600 ppm at a conveyor speed of 1200 mm/min. The soldering results were examined at various temperatures of preheating and soldering. It proves that the measured peak temperature of liquid solder TpL over 230 °C makes the bridging defect rate lower than 0.30%. Additionally, setting the peak temperature of solder joint TpZ above 220 °C, along with specific preheating temperatures (105/115/135/145 °C), archives 100% vertical filling without significant voids in the solder joints. Moreover, optimizing wave soldering settings, specifically adjusting the wave soldering setting temperature Ts to 235 °C, conveyor speed vc to 1000 mm/min, resolves soldering defects associated with Sn-9Zn-2.5Bi-1.5In alloy in wave process. Relevance summary1.TpL surpasses 230 °C, the total number of bridging defects per board decreases to fewer than 6, approximately 0.30%. TpZ values of 220 °C or higher results in 100% vertical fill and no significant large voids, demonstrating optimal filling effects2.Under the conditions of TS = 235 °C and vc = 1000 mm/min yield TpL > 230 °C and TpZ > 210.9 °C, it leads to a reduction in bridging defects.3.To maintain flux efficiency and minimize internal voids, an optimal selection of preheating temperatures (105/115/135/145 °C) is demonstrated.4.An integrated nitrogen content-controlled system is utilized to eliminate oxygen from the solder pot, aiming to prevent oxidation.

Comparative Study of the Impurity Effect on SnAgCu and SnZn Solder Joints with Electrodeposited Cu.

Sn-3Ag-0.5Cu (SAC305)- and Sn-9Zn-based alloys (Sn-Zn-X, X = Al, In) are lead-free solders used in the fabrication of solder joints with Cu metallization. Electroplating is a facile technology used to fabricate Cu metallization. However, the addition of functional additive molecules in the plating solution may result in impurity residues in the Cu electroplated layer, causing damage to the solder joints. This study investigates the impurity effect on solder joints constructed by joining various solder alloys to the Cu electroplated layers. Functional additives are formulated to fabricate high-impurity and low-impurity Cu electroplated samples. The as-joined solder joint samples are thermally aged at 120 °C and 170 °C to explore the interfacial reactions between solder alloys and Cu. The results show that the impurity effect on the interfacial reactions between SAC305 and Cu is significant. Voids are massively formed at the SAC305/Cu interface incorporated with a high impurity content, and the Cu6Sn5 intermetallic compound (IMC) grows at a faster rate. In contrast, the growth of the Cu5Zn8 IMC formed in the SnZn-based solder joints is not significantly influenced by the impurity content in the Cu electroplated layers. Voids are not observed in the SnZn-based solder joints regardless of the impurity content, indicative of an insignificant impurity effect. The discrepancy of the impurity effect is rationalized by the differences in the IMC formation and associated atomic interdiffusion in the SAC305- and SnZn-based solder joints.

The preparation and wettability of the Sn-9Zn-2.5Bi-1.5In solder paste for SMT process and high shear ball performance

Purpose This study aims to focus on the surface mount technology (SMT) mass production process of Sn-9Zn-2.5Bi-1.5In solder. It explores it with some components that will provide theoretical support for the industrial SMT application of Sn-Zn solder. Design/methodology/approach This study evaluates the properties of solder pastes and selects a more appropriate reflow parameter by comparing the microstructure of solder joints with different reflow soldering profile parameters. The aim is to provide an economical and reliable process for SMT production in the industry. Findings Solder paste wettability and solder ball testing in a nitrogen environment with an oxygen content of 3,000 ppm meet the requirements of industrial production. The printing performance of the solder paste is good and can achieve a printing rate of 100–160 mm/s. When soldering with a traditional stepped reflow soldering profile, air bubbles are generated on the surface of the solder joint, and there are many voids and defects in the solder joint. A linear reflow soldering profile reduces the residence time below the melting point of the solder paste (approximately 110 s). This reduces the time the zinc is oxidized, reducing solder joint defects. The joint strength of tin-zinc joints soldered with the optimized reflow parameters is close to that of Sn-58Bi and SAC305, with high joint strength. Originality/value This study attempts to industrialize the application of Sn-Zn solder and solves the problem that Sn-Zn solder paste is prone to be oxidized in the application and obtains the SMT process parameters suitable for Sn-9Zn-2.5Bi-1.5In solder.

Microstructure and mechanical property of thick Cu/AlN joints formed at low temperature

AbstractThe bonding of thick Cu and AlN is necessary in power modules with the development of high‐frequency communication technology. In this work, 2 mm‐thick Cu was successfully bonded with AlN by using Sn9Zn solder with the assistance of ultrasonication at 230°C. Results showed that an AlN/Sn9Zn/Cu joint without crack was manufactured with a cooling rate of 7°C/min. Nonreactive wetting was realized between AlN and Sn9Zn, forming an amorphous transition layer. CuZn2 and CuZn were formed at the Sn9Zn/Cu interface. A joint with the highest bonding strength of 30.07 MPa was obtained, in which the AlN/Sn9Zn interface was no longer the weakest location. This work provides a low‐temperature manufacturing method for thick Cu/AlN joints.

Evaluation of the microstructure, thermal, and mechanical characteristics of Sn-9Zn reinforced with Ni and ZrO2 nanoparticles via vacuum melting process

The impact of minor additions of nickel and ZrO2 nanoparticles to eutectic Sn-9wt%Zn (SZ) prepared by vacuum melting technique was investigated. The morphologies and microstructures were carried out using an optical microscope (OM) and field emission scanning electron microscope technique (FESEM) escorted by energy dispersive x-ray spectrometry (EDX). The phase structure of the specimens was confirmed by an x-ray diffractometer (XRD). The results obtained demonstrate that small Ni addition causes a major grain refinement of β-Sn, due to the formation of the fine intermetallic compounds Ni5Zn21 and Sn3Ni4Zn3 phases and refines the formation of α- Zn lamellar phase. The melting temperature of the recently discovered solder alloys was lower than that of the eutectic Sn-Zn solders (∆Tm ∼ 28 °C) as a result of the preparation technique and the incorporation of Ni and ZrO2 nanoparticles. The tensile test showed enhanced the mechanical properties of SZ solder as a result of the addition of third elements. The experimental results showed that of all the alloys under investigation, the SZN903 alloy had the greatest UTS and YS values. The enhanced strength of the SZ-ZrO2 alloy defended the results of σ UTS and increased the stress exponent parameters, n, by ∼20%. All solders had an activation energy Q that measured between ∼35.62 kJ mol−1 to ∼58.12 kJ mol−1 which comparable to the pipe-diffusion mechanism.

Research Progress in Corrosion Protection Technology for Electronic Components

As a necessary part of all electronic devices, equipment and systems, electronic components play a vital role in the global economy. Since the corrosion of a single electronic component may directly affect the normal operation of the entire electronic system, the failure of electronic components has now become the most important cause of electrical system failure and has become a major obstacle to China’s transformation into a scientific and technological power. Therefore, it is urgent to study the corrosion failure process of electronic components and the means of effective protection. In this paper, starting from the corrosion types and influencing factors of electronic components, especially chips, we introduce the influence of humidity, temperature, salt spray, and environmental particles, as well as the device’s own surface roughness, material adhesion, semiconductor materials, metal coupling system, and lead-free solder system on corrosion performance in the environment. Subsequently, this paper summarizes how to protect electronic components during processing, and sums up the types of electronic component protections, and the specific corrosion protection process for the three commonly used types of chips, namely, the indium antimonide InSb chip, the IC chip, and the Sn–Zn solder chip, for reference. Finally, future development trends in the corrosion protection of electronic components are anticipated and summarized.

Effect of Al and Bi addition on the corrosion behaviour, hardness, and melting temperature of lead-free solder alloys

Herein, the influence of alloying bismuth (Bi) and aluminum (Al) on the corrosion performance of Sn9Zn in a 3.5 % NaCl solution was examined. Electrochemical techniques were used to examine the corrosion behaviour of Sn9Zn, Sn-9Zn-0.5Bi, and Sn-9Zn-0.5Bi-0.5Al. After corrosion measurements, the alloy surfaces were studied by scanning electron microscopy (SEM) and energy dispersive X-ray diffraction (EDX). The results demonstrated that the presence of Bi increased the corrosion resistance because it formed an anodic barrier on the Sn-9Zn-0.5Bi alloy surface. The study extended to measure the Vickers hardness number of these alloys, and the results indicated a significant improvement in the hardness number of the Sn9Zn alloy by approximately 11 % with Bi and 54 % with Bi and Al. More investigations of the melting temperature behaviour of solder alloys using differential scanning calorimetry (DSC) were also carried out before corrosion measurements. The DSC results demonstrated that Sn-9Zn-0.5Bi-0.5Al had a lower melting temperature than Sn9Zn and Sn-9Zn-0.5Bi. Therefore, Al and Bi addition improved the melting temperature characteristics of the Sn9Zn solder alloy. This confirmed that the presence of Bi only enhanced the corrosion resistance, and the presence of both Bi and Al played a crucial role in the properties enhancement of the Sn9Zn alloy. Consequently, these improved characteristics and properties make the suggested compositions a significant alternative choice to SnPb alloys.

Robust effects of In, Fe, and Co additions on microstructures, thermal, and mechanical properties of hypoeutectic Sn–Zn-based lead-free solder alloy

This study examines the influence of separate and dual minor alloying additions of indium (In) and ferrous/cobalt (Fe/Co) on the microstructure, thermal, and mechanical properties of hypoeutectic Sn–7wt.% Zn lead-free solder alloy. The results showed that the addition of In resulted in significant refinement in the microstructure and formation of new intermetallic compounds (IMCs) such as In–Sn phases which capable of extensively removing the unfavorable needle-like α-Zn phase. However, the additions of Fe/Co resulted in the creation of new coarsening flower-shaped IMCs identified as Zn–Co, Fe–Sn, and Co–Sn–Zn distributed uniformly which may have a marked effect on the mechanical and thermal properties of Sn–Zn solder alloy. Thermal analysis by a differential scanning calorimeter indicates slightly reduction in the onset temperature, melting temperature, and undercooling of the Sn–7wt.% Zn by the addition of In, while the pasty range enlarged as compared to Fe/Co additions. The tensile tests indicate that the Sn-Zn-In solder alloy exhibited a superior balance of ultimate tensile strength, yield strength, Young’s modulus, and elongation of 51.5 MPa, 44.4 MPa, 22.2GPa, and 44.5%, respectively, which are better than both those of the Sn–Zn and Sn–Zn–Fe/Co solder alloys. This can be attributed to the synergistic strengthening mechanism of refinement in the microstructure and precipitation of fine secondary particles.

Capillary filling ability of Sn-Zn solder on SiC ceramic surface under electromagnetic ultrasonic action

In this work, we present the capillary filling behavior of Sn-9Zn molten solder on the surface of SiC ceramic with different initial contact angles with and without electromagnetic ultrasonic action. The results showed that the capillary filling behavior did not easily occur in the native state. Electromagnetic ultrasonic action could promote the capillary filling behavior of the Sn-9Zn solder on the surface of SiC ceramic. When the peak current was 10 A, the maximum value of the capillary filling length of the solder at a contact angle of 90° was 11.56 mm. When the peak current was 100 A, the solder on the left side of the gap broke. The surrounding air induced an alternating magnetic field whose direction changed periodically; with opposite directions of the magnetic field generated by the left and right coils. The direction of the Lorentz force on the left side of the solder was opposite to the right side, and the alternating magnetic field influenced the direction of the Lorentz force inside the solder, where the Lorentz force inside the solder was directly proportional to the peak current. The sound pressure inside the solder also changed to positive and negative pressure in one cycle, where the maximum value was 1.67 × 105 Pa.

Corrosion behaviour of Sn-9Zn-xS solders in 3.5 wt-% NaCl solution

The effects of S addition on the corrosion behaviour of Sn-9Zn solders in 3.5 wt-% NaCl solution were investigated using dynamic potential polarisation, electrochemical impedance spectroscopy techniques and weight loss measurement. The results indicate that S addition could obviously improve the corrosion resistance of Sn-9Zn solder alloy as revealed by much lower corrosion current density, higher impedance and the reduced weight loss. It is believed that the homogeneous microstructures of Sn-9Zn, especially the black refined Zn-rich phases are favourable to improve its corrosion resistance. SEM observations found that S addition might promote the formation of denser and more uniform corrosion products on the solder surface. The main corrosion product was Zn5(OH)8Cl2·H2O determined by EDS and XRD analysis.

Electrochemical behavior of Sn-9Zn-xCu solder alloy in 3.5 wt% NaCl solution at room temperature

The effect of Cu addition on potentiodynamic and static immersion corrosion behavior of Sn-9Zn-xCu (x=0,1,2,3 wt%) was evaluated for their application in the electronic industry. Samples of solder alloy were prepared through vacuum induction furnace melting. Techniques such as SEM, XRD, and XPS were applied to evaluate the morphology and corrosion products on the surface. Microstructural characterization and phase analysis before the corrosion test show the presence of Cu 5 Zn 8 and Cu 6 Sn 5 intermetallics in the matrix. The primary corrosion products were found to be zinc hydroxide chloride Zn 5 (OH) 8 Cl 2 .H 2 O, tin oxide chloride hydroxide (Sn 3 O(OH) 2 Cl 2 ), SnO, and ZnO. The possible reasons for the generation of zinc corrosion products were critically discussed, and the most precise mechanism was proposed. Adding 1 to 3 wt.% copper to the Sn-9Zn solder alloy increased its corrosion resistance, owing to coarser and more evenly distributed corrosion-vulnerable Zn-rich precipitates. Static corrosion tests show that the weight loss decreases with increased copper content, indicating an increase in corrosion resistance. Sn-9Zn-3Cu alloys recorded the maximum corrosion resistance among all the alloys in the above corrosion tests.

Control of intermetallic compounds in Ultrasonic-Assisted Sn soldering of Mg/Al alloys

Magnesium and aluminum alloys are widely used in various industries because of their light weight and other properties. However, Mg–Al intermetallic compounds (IMCs) decrease the joint properties of Mg/Al, which limits its applications. Here, the alloys AZ31 Mg and 6061 Al are soldered together with Sn and Sn–9Zn solders though different cooling rates via ultrasonic-assisted soldering to control IMC formation and growth. Results show that this prevents formation of Mg–Al IMCs such as Al3Mg2 and Al12Mg17; however, Mg2Sn forms in the soldered joints. The Mg2Sn thickness increases with soldering temperature, which reduces joint strength. The thickness is reduced using the Sn–9Zn solder, and the effect of Zn is analyzed. With the use of water-cooling, the Mg2Sn formation and growth are inhibited, the Mg2Sn thickness is kept below 5 μm, and the shear strength peaks at 53.2 MPa. A soldering model of Mg2Sn formation is proposed to reveal the evolution and inhibition mechanism of Mg2Sn. This study well controls IMC thickness and improves joint strength, thus expanding industrial application of Mg–Al dissimilar metals and providing a feasible method for controlling IMCs in dissimilar metal joining.

Investigation of thermal and mechanical properties of Sn-Zn and Sn-Zn- Bi near-eutectic solder alloys

In the present work, three near-eutectic lead-free solder melts of Sn-8wt.%Zn; Sn-8wt.%Zn-2wt.%Bi and Sn-8wt.%Zn-4wt.%Bi have swiftly solidified by means of the melt-spinning technique for intermediate –step soldering. The thermal and various mechanical properties of the formed melt-spun ribbons were investigated by dynamic resonance technique, Vickers micro-hardness test under annealing temperatures in the range from 348 K to 448 K. Thermal analysis using differential thermal analysis (DTA) technique revealed a decrease in melting point and solidus point with %Bi. Wettability property was determined by evaluating the contact angle on a different substrate and found to be in the range 31° to 43° on Cu or CuZn30 substrates and in the range from 110° to 115° on Al substrate. The microhardness tests as a function of temperature were performed to determine the stiffness of Sn-Zn solder alloys. Isothermal creep curves for the synthesized samples alloys were determined and plotted under constant applied stresses at a constant temperature of 463 K. Microstructure of the as-cast alloys both, at room temperature and annealed at 348 K were recorded. The creep test on the structure change and properties of Sn–Zn alloys were reported with the effect of the cold work deformation. The Sn-8wt.%Zn-4wt.%Bi is a candidate material for solder which is free of Pb and widely used for packaging of micromechanical systems as a hermetic sealing step.

Microstructure and enhanced joint performance of porous Si3N4 ceramics in ultrasonic soldering

Brazing is a commonly used method to join porous Si3N4 ceramics; it requires high temperature, long holding time, and vacuum environment. In this work, given the phenomena of sonocapillary and increased cavitation in narrow channels, ultrasonic-assisted soldering was successfully used to join porous Si3N4 ceramics at low temperature of 230 °C in the air within a short period. The effect of ultrasonic time on the microstructure and mechanical properties of the soldered joints was studied. The bonding mechanism of solder to ceramic was studied by scanning electron microscope, electron probe microanalyzer, and transmission electron microscope (TEM). Results showed that the Sn9Zn solder can infiltrate the microchannels of the porous Si3N4 ceramics through sonocapillary within a short ultrasonic time of 3 s. Prolonged ultrasonic time resulted in better wetting of solder to ceramic and wider infiltration layer. The infiltrated solder tightly bonded with the ceramic rod without pores and cracks. The TEM results showed that Zn and O were the main bonding elements. The bonding interface was characterized by nanocrystalline and amorphous ZnO. The shear tests revealed that prolonged ultrasonic time enhanced the joint strength.

A novel antioxidant and low-temperature Sn-Zn solder paste based on Zn@Sn core-shell structure

With the advancement of lead-free solder, Sn-Zn solder was once considered the best choice. However, the high activity of Zn limited its application. To solve the problems of serious oxidation of zinc in Sn-Zn solder, a novel Sn-Zn solder paste based on Zn@Sn core-shell structure was developed. The Zn particles with a diameter of 3.5 µm are coated with a Sn layer with a thickness of 1.5 µm, which improves the oxidation resistance of Zn particles. The effect of the weight ratio of Zn@Sn to the Sn particles on the type and thickness of the intermetallic compounds (IMCs) layer was investigated. The shear strengths of solder joints based on the Zn@Sn core-shell particles were increased by 44% compared with that of the commercial Sn-Zn preforms, after reflowing at 230 °C for 10 min. The fracture microstructure showed a mixed fracture mode with both ductile and brittle characteristics. The results demonstrate that composite solder paste based on Zn@Sn core-shell structure is a promising die attach material for power device packaging.

Low temperature bonding mechanism of porous Si3N4 ceramics by Sn9Zn solder in ultrasonic-assisted soldering

Porous Si3N4 ceramics are widely used materials but very difficult to join. In this work, we successfully ultrasonically soldered porous Si3N4 ceramic rapidly at a low temperature of 230 °C. The wetting and bonding mechanism at the ceramic/solder interface was studied. Results showed that the solder rapidly infiltrated the micro-channels of the ceramic during soldering, and high ultrasonic power contributed the sonocapillary distance. Zn and O acted as the main bonding elements. Bonding was realized by the formation of nanocrystalline and amorphous ZnOx region at the wetting interface. Rapid bonding was achieved due to the high liquid velocity, high temperature, and high pressure caused by the collapse of the cavitation bubbles.

Avoiding degradation and increasing joint strength of Al alloys by rapid ultrasonic soldering at low temperature

To avoid substrate softness, AA7075 were rapidly soldered using a Sn-9Zn solder at 200 °C under ultrasonication. The effect of acoustic intensity on the microstructure and mechanical properties of the soldered joint was studied. The acoustic intensity inside the solder was improved by decreasing the lap width without increasing the input ultrasonic power. Results showed that the softness of the substrate was almost avoided with minimal hardness decrease. The acoustic intensity increased by four times when the width of the lap clearance was reduced from 0.8 mm to 0.2 mm. Pronounced erosion of the substrate occurred under high acoustic intensity. Thus, the content of Al in the joint seam increased from 3.35% to 10.84% after reducing the lap width from 0.8 mm to 0.2 mm. The joint seam was characterized by interlaced fine/coarse Sn-Zn eutectic. The Sn and Zn grains had average sizes of 2.31 and 0.31 μm in the fine eutectic and 3.03 and 0.41 μm in the coarse eutectic. Increasing the acoustic intensity during soldering can effectively increase joint strength. The maximum shear strength of 65.4 MPa and hardness of 29.5 HV were obtained in the joint soldered at 0.2 mm. The cavitation bubble with a nucleation diameter of 10 μm had a large liquid velocity of 7653 m/s, a temperature over 1800 K, and a pressure of 4 × 1012 Pa during its collapse.

Evolution of interfacial IMCs and mechanical performance of joints of Mg/Al dissimilar metals soldered by using Ga-coating protection

The soldering of Al/Mg dissimilar metals by using Sn–9Zn solder at a low temperature of 230 °C was investigated. A liquid gallium layer was coated on the faying surface of the base metals to avoid secondary oxidation and contact between Mg and Sn-based filler metal before soldering. The growth and distribution of intermetallic compounds (IMCs) at the interface of Mg/solder was focused on. The interface was composed of scattered large and dense small blocky IMC layers. The discontinuous Mg2Sn layer was found to be the key factor dominating the mechanical performance of the joints. The highest shear strength of 38 MPa was reached at a reasonable holding time of ∼10 min. An over long holding time would cause the segregation of gallium which would deteriorate the water resistance of the joints.