Intermetallic Compound Grains Research Articles

Investigating the impact of cobalt incorporation on the transformation of Cu6Sn5 layer to (Cu, Co)6Sn5: Microstructural and mechanical insights

In this study, cobalt (Co) particles were incorporated as reinforcing agents into the Sn58Bi solder. The solderability of the solder and the strength of the solder joints were investigated. The results indicated that adding Co particles did not alter the low melting point characteristics of the Sn58Bi solder, yet its undercooling was reduced, and the wettability was enhanced. In the Sn58Bi/Cu solder joint, adding Co led to forming free (Cu, Co)6Sn5 intermetallic compound (IMC) and generating the CoSn2 phase through microalloying. The interfacial IMC was gradually transformed from a fan-shaped Cu6Sn5 to a flatter layer-like (Cu, Co)6Sn5 IMC, eventually exhibiting a coral-like structure with increased Co content. Adding Co particles increased the thickness of the IMC layer, but at low levels, the Co could refine the IMC grains. Simultaneously, implementing grain refinement and Orowan strengthening resulted in heightened microhardness and shear strength. In the shear test, the fracture of solder joints predominantly transpired within the solder matrix. Excessive Co particles were prone to aggregating within the solder, forming irregular block-shaped (Cu, Co)6Sn5. Concurrently, the coral-like IMC at the interface led to a decline in the mechanical performance of the solder joints, with some interfacial IMC being exposed in the fracture region.

Interfacial reaction of Sn-1.5Ag-2.0Zn low-silver lead-free solder with oriented copper

High density packaging technology reduces the pad size and the number of grains contained in the pad. When the polycrystalline pad turns into a single crystal pad, the grain orientation has an important impact on the formation of the intermetallic compound (IMC) at the interface. The growth of IMC at the interface between the solder and the single-crystal copper substrate is investigated by selecting the prospective Sn-1.5Ag–2Zn as the solder alloy. Sn-1.5Ag-2.0Zn lead-free solder joints soldered with single crystal (111) copper substrate and polycrystalline red copper substrate are reflowed at 250 °C for 5 min. Samples are subsequently aged at 160 °C. The uneven scallop like Cu6Sn5 IMC layer grows rapidly when the alloy solder contacts with the copper substrate. The Cu6Sn5 grain size formed on the surface of single crystal copper is larger than that of polycrystalline copper. Single crystal copper has no grain boundary to block atomic diffusion, which affects grain nucleation and growth. The growth rate of Cu6Sn5 formed by alloy solder and the single crystal (111) copper solder joint after aging treatment at 160 °C for 20 h is about twice that of the polycrystalline copper solder joint. Then it grows slowly with the increase of aging treatment time. The thick layer Cu6Sn5 breaks due to crack diffusion after 600 h of aging treatment, and the thickness of IMC remains at 3.5 μm. Cu5Zn8 generated at the solder and polycrystalline copper solder joint during aging treatment acts as a barrier layer, preventing the solder from contacting the copper substrate and inhibiting the formation of Cu6Sn5. Cu5Zn8 is broken and decomposed after 300 h of aging treatment, and Cu6Sn5 grows rapidly after the barrier layer disappeared. The thickness of Cu6Sn5 is about 2.8 μm. The thickness of IMC of solder joint on single crystal copper is 0.7 μm more than that on polycrystalline copper. After aging treatment, the IMC formed at the interface between alloy solder and single crystal copper has better compactness and basically no pores, while there are obvious pores between IMC grains at the interface between alloy solder and polycrystalline copper, which can predict that the soldering quality of the interface between alloy solder and single crystal copper is better. This will provide application prospects for solder joint interface reliability research.

Effect of post-weld heat treatment on the microstructure and properties of titanium/304 stainless steel laser welding dissimilar metal joints with copper as the transition layer

Low elongation has been an important factor limiting the application of titanium/304 stainless steel (304SS) laser welding of dissimilar metal joint products. By adopting the post-weld heat treatment (PWHT) process of holding the welded joint at 400 ℃, 550 ℃ and 700 ℃ for 30 min, this study increases the elongation of the welded joint from 0.3 % to 2.21 % in the welded state and further analyses and investigates the structural changes in the organization and the formation process of intermetallic compounds (IMC) within the weld seam. The results showed that the acicular structure in the weld could not be eliminated by holding at 400 ℃ for 30 min, but only part of the residual stress was released, and the elongation was increased to 0.85 %. After holding at 550 ℃ for 30 min, a large number of equiaxed crystals appeared to replace the acicular structure in the weld and released the residual stress. With the enhancement of the IMC layer thickness, grain gap and deformation coordination ability, the elongation increased to 2.21 %. After holding at 700 ℃ for half an hour, the IMC layer becomes thinner, the grain gap decreases, the deformation coordination ability deteriorates, and the tensile strength and elongation decrease. In the tensile test, the fracture position was all at the weld. After being held at 400 ℃ for 30 min, the average tensile strength of the tensile sample increased from 330 MPa in the welded state to 352 MPa; after being held at 550 ℃ for 30 min, the average tensile strength of the tensile sample was 340 MPa, and the fracture elongation was 7.4 times that of the welded state, reaching 331 µm.

Study on the dual inhibition behavior of interfacial IMCs in Cu/SAC105/Cu joint by adopting SiC nanowires and nanocrystalline Cu substrate

To obtain high-strength joints suitable for three-dimensional (3D) packaging, SiC nanowires (NWs) were doped to the Sn1.0Ag0.5Cu (SAC105) solder, and the conventional Cu substrate was replaced with nanocrystalline (NC) Cu to form Cu/solder/NC Cu solder joints. It was found that the application of SiC NWs and NC Cu had an essential effect on the evolution and growth kinetics of the solder joint interface. The formation of intermetallic compounds (IMC) bridging and full-IMC joints at the interface was delayed. The absorption effect of SiC NWs and numerous nucleation sites provided by NC Cu resulted in a notable reduction in interfacial IMC grains size and interfacial Cu3Sn IMC layer thickness. In addition, the Cu/SAC105-SiC/NC Cu solder joint exhibited the highest shear strength. On the one hand, SiC NWs were incorporated into Cu6Sn5 IMC grains to form the reinforced concrete structure. On the other hand, NC Cu provided more fine Cu6Sn5 IMC grains for the interface. Combined with the analysis of the fracture morphology, it can be concluded that the combination of SiC NWs and NC Cu substrate substantially improved the mechanical properties of the solder joints.

Intermetallic compound evolution and mechanical properties of Cu/Sn58Bi/Cu 3D structures blended with B4C nanoparticles during isothermal aging

The Cu/Sn58Bi/Cu and Cu/Sn58Bi-0.6B4C/Cu joints were prepared by transient liquid phase (TLP) bonding technology to verify the reliability of low-temperature connection joints. Intermetallic compound (IMC) evolution at the interface under different isothermal aging times was analyzed, and the mechanical properties of the joints were tested. The results show that two kinds of IMC, lamellar Cu3Sn and fan-shaped Cu6Sn5, are formed on both sides of the joint. With increasing soldering time, the thickness for both kinds of IMC become thicker, and it is significantly thicker for the IMC near the cold end. Furthermore, the IMC growth rate of the Cu/Sn58Bi-0.6B4C/Cu solder joint is significantly lower. When the isothermal aging time reaches 36 h, the Cu/Sn58Bi/Cu joint has been almost composed of IMC, while it needs a longer time for the Cu/Sn58Bi-0.6B4C/Cu joint. The growth of Cu3Sn IMC is in line with parabolic law, being mainly controlled by volume diffusion near the hot end, while the grain boundary diffusion significantly affects it at the cold end. The joints shear strength decreases gradually with extending bonding time, but it is always higher for the Cu/Sn58Bi-0.6B4C/Cu joint. When the heating time is not long, the fracture mainly appears at the Bi-rich phase in the solder matrix. With increasing bonding time, the location of fracture gradually transformed from the Cu6Sn5 grains to the junction of the two IMC and Cu3Sn grains, along with the intercrystalline fracture and transcrystalline fracture. In summary, B4C nanoparticles can significantly improve the joint reliability and enhance its mechanical properties.

Formation Mechanism of Thicker Intermetallic Compounds in Friction Stir Weld Joints of Dissimilar AA2024/AZ31B Alloys

The hybrid structures of AA2024 aluminum alloy and AZ31B magnesium alloy have the advantages of being lightweight, having high specific strength, etc., which are of great application potentials in the aerospace industry. It is a key problem to realize the high-quality welding of these two dissimilar alloys. In this study, the friction stir welding (FSW) tests of AA2024 aluminum alloy and AZ31B magnesium alloy plates of thickness 3 mm were carried out. The intermetallic compounds (IMCs) at the bonding interface were characterized by scanning electron microscope, electron probe, and transmission electron microscope. It was found that the IMCs at the bonding interface in weld nugget zones of dissimilar AA2024/AZ31B FSW has a double-layer structure and a much larger thickness. During the welding process of AA2024/AZ31B, when the boundary of magnesium grains bulges and nucleates, the aluminum atoms diffuse into the magnesium grains, and the γ phase (Al12Mg17) nucleates at the bonding interface. The β phase (Al3Mg2) then precipitates at the grain boundary of the γ phase and preferentially grows into γ phase grains. The continuous grain growth to the aluminum side makes the copper contained in AA2024 aluminum alloy concentrate on the side of β phase, which reduces the nucleation work of recrystallization and phase transformation, and further promotes the nucleation and growth of IMCs grains. This is the main reason for the thicker IMCs in the FSW weld of dissimilar AA2024/AZ31B alloys.

Drastic Improvement in Dissimilar Aluminum-to-Steel Joint Strength by Combining Positive Roles of Silicon and Nickel Additions

Dissimilar welding of an aluminum (Al) alloy to steel is expected to be effective for weight reduction of automotive car bodies. In this study, an aluminum alloy 1050 sheet was welded to a nickel (Ni)-plated Fe sheet using a silicon (Si)-containing Al filler by gas tungsten arc welding. The effect of the simultaneous addition of Si and Ni on the Al/Fe joint strength associated with the microstructure of the intermetallic compound (IMC) layer was systematically examined. The addition of Si and Ni individually improved the Al/Fe joint strength by the reduction in the IMC layer thickness caused by the Si addition and the refinement of the IMC grains due to the Ni addition, respectively. The most effective improvement in the joint strength was achieved by the simultaneous addition of Si and Ni. The IMC layer at the Al/Fe interface with Si addition consisted of θ-Fe4Al13, η-Fe2Al5, and Al–Fe–Si ternary IMCs, while it changed to θ-Fe4Al13, η-Fe2Al5, and an Al–Fe–Ni ternary IMC after Ni was additionally added. This change in the phase as well as the thickness reduction and grain refinement of the IMC layer probably contributes to further improving the joint strength by the simultaneous addition of Si and Ni.

Analysis of intermetallic compound formation in the reactions at liquid Ga/solid Pd interface

Interfacial reactions between liquid Ga and solid Pd were investigated in two different temperature ranges: 120–180 °C and 250–350 °C. In the low-temperature range (120–180 °C), Ga5Pd intermetallic compounds (IMCs) grew at the reaction interfaces, with irregular consumption of the Pd substrates. The time exponents for Ga5Pd IMC growth were 1.04, 1.22, and 1.72 at 120, 150, and 180 °C, respectively, with an activation energy of 71.0 KJ/mol. In the high-temperature range (250–350 °C), the Ga7Pd3 IMCs grew as the reaction progressed, whereas the Ga5Pd IMCs precipitated on the Ga7Pd3 layer during the cooling process. In this case, the time exponents for Ga7Pd3 growth were 0.96, 1.40, and 1.38 at 250, 300, and 350 °C, respectively, with an activation energy of 68.6 KJ/mol. The low time exponent values determined in this study are attributed to the porous microstructures of the IMC layers, which provide effective pathways for Ga-Pd interdiffusion. Growth of the rod-type Ga5Pd (or Ga7Pd3) IMCs was presumed to be governed by interface reaction-controlled kinetics, where the reaction species were abundantly available in numerous channels between the IMC grains. The results have prospectively important implications for interconnection between Ga and Pd in the fabrication of future flexible electronic devices.

Size effects on IMC growth of Cu/Ni/Sn-3.5Ag microbump joints during isothermal aging and prediction of shear strength using ANN

Significant downsizing trend is currently directing the advanced microelectronic packaging industry, which poses new challenges to the manufacturing process and reliability of high-density chip interconnections. In this paper, to investigate the size effect of microbump joints on the interfacial structure and bonding strength, the chip-to-chip bonding joints fabricated by microbumps of same Cu/Ni/Sn-3.5Ag construction but of various sizes were experimentally examined. After thermocompression bonding process to fabricate the chip-to-chip microbump interconnections, the intermetallic compound (IMC) growth on the Ni/Sn-3.5Ag interface during 150 °C isothermal aging was compared for joints of 100, 40 and 25 μm in diameter as well as 35, 25 and 15 μm in solder layer height, using field emission electron microscopy and electron probe microanalysis. A clear size effect on the thickness and morphology of Ni3Sn4 IMC was observed, showing thicker IMC in joints of smaller diameter and lower height. The Ni concentration distribution in the solder layer was verified to be dependent on the joint size, with possible reasons being enhanced sidewall diffusion and grain boundary diffusion through IMC grains in small-diametered joints, as well as shorter diffusion path in lower joints. The shear strength of chip-to-chip bonding vehicles was also found to be size-dependent. In addition, artificial neural network (ANN) approach was applied to establish the numerical correlation of structural factors and bonding strength. It was found that a properly constructed ANN model can successfully predict the influence of the complex combinations of geometric and interfacial factors with highly accurate output, providing an effective tool for design and optimization of microbump interconnection structures and processes.

Highly reliable Cu[sbnd]Cu low temperature bonding using SAC305 solder with rGO interlayer

The immoderate growth of intermetallic compounds (IMCs) and the transformation of benign IMCs to malignant IMCs are the main causes for the decrease of the mechanical properties and reliability in the CuSn joints. In this study, a 14 nm thickness reduced graphene oxide (rGO) interlayer was directly prepared between Cu and Sn-3.0 Ag-0.5 Cu (SAC305) solder to inhibit the immoderate growth of IMCs and malignant IMCs formation at the bonding interface. The highly reliable CuCu bonding was realized at 150 °C under the external pressure of ~8.3 MPa. The bonded samples were aged at 150 °C for 0 h–72 h for reliability tests. After aging for 72 h, the thickness of the IMCs layer at the Cu/rGO/solder interface decreases by more than 30%, and the average projected area of IMCs grains decreases by more than 80% compared with that at the Cu/solder interface. Furthermore, the decreasing rate of shear strength with rGO interlayer is lower than that without rGO interlayer for long time aging. For the Cu/rGO/solder bonding structure, after 72 h aging, the shear strength is higher and the contact resistance is lower compared with the Cu/solder bonding structure. For this low temperature bonding process using the rGO interlayer, the immoderate growth of IMCs at the bonding interface was inhibited, which can delay the decrease of shear strength due to aging of the bonding interface.

Multi-phase field simulation of Al[formula omitted]Ni[formula omitted] intermetallic growth at liquid Al/solid Ni interface using MD computed interfacial energies

Considering its application in developing Raney-type Ni catalysts and in metal surface coatings, the study on the growth behavior of Al3Ni2 intermetallic compound (IMC) at the Al/Ni material interface is of utmost importance. The present work integrates nanoscale molecular dynamics (MD) calculation with mesoscale phase field model for studying the interfacial phenomena associated with Al3Ni2 growth in Al/Ni interface at 1173.15 K. The interfacial energies computed from MD are in the range 0.9–1.2 J/m2 with FCC/IMC featuring as the interface with the largest value and IMC/LIQUID as the one with the lowest value. Phase field model parameters characterizing a varying interface energy formulation are established to simulate the 2D growth of interfacial IMC grains. With the help of an atomistically informed phase field model, it has been revealed that the phase areas and morphology are obviously sensitive to the interfacial properties. The methodologies and results of these multiscale simulations for IMC interfaced between Al and Ni microstructures offer the complementary and accelerated design route of in-silico studies for materials systems experimented at high temperature.

Effect of SiO2 nanoparticle addition on growth of interfacial Ag3Sn intermetallic compound layers between lead-free solder and silver conductor

This study investigated the effects of silver powder modification on intermetallic compound (IMC) formation and silver leaching during soldering at high temperatures. Silica nanoparticles (NPs) were deposited onto a silver powder surface to inhibit silver leaching, which can lead to soldering joint failure during high-temperature soldering. The NPs were deposited through hydrolysis and a condensation reaction of tetraethyl orthosilicate (TEOS) based on the Stöber method. Fourier transform infrared spectroscopy and scanning electron microscopy were used to observe the microstructures of silver powders after the deposition of silica NPs with various TEOS concentrations and various deposition times. As the deposition time increased, the amount of silica NPs on the surface of the silver powder increased. The transmission electron microscopy results show that silica NPs were located at the IMC grain boundaries, which can hinder the dissolution of IMCs by lead-free solder melt along grain boundaries during soldering, retarding silver leaching. The growth kinetics and mechanism of IMCs during soldering were investigated. The results show that the growth of IMCs is mainly dominated by bulk diffusion. The activation energy for IMC growth increased and the growth rate decreased with increasing silica NP addition and deposition time.

Interfacial evolution of pure Sn solder bearing silicon carbide nanowires under isothermal aging and thermal cycling

In this paper, the intermetallic compound (IMC) growth behaviors of Sn/Cu and Sn–0.6SiC/Cu solder under isothermal aging (50, 100, 150, 200 and 250 h) and thermal cycling (300, 600, 900, 1200 and 1500 cycles) were studied. The results manifested that the IMC layer got thicker in Sn/Cu solder and Sn–0.6SiC/Cu solder as the aging time or thermal cycles increased, but the IMC thickness of Sn solder incorporated with silicon carbide nanowires (SiC NWs) was smaller than that of Sn solder in the same condition. According to the adsorption theory, SiC NWs would adsorb on the IMC grains and then reduce the surface tension of IMC, which made for the suppression of IMC growth. Also, SiC NWs could nail at grain boundaries and then prohibit the further growth of IMC grains. Thus, doping 0.6 wt% SiC NWs could reduce the size of IMC grains and decrease the diffusion coefficient of IMC growth, which led to prohibiting the interfacial IMC growth at solder/substrate under isothermal aging. During thermal cycling process, SiC NWs addition was beneficial to decrease the rate of IMC growth at the interface of Sn/Cu solder. Moreover, adding SiC NWs into Sn solder could improve the reliability of solder joints in that there were less cracks formed at IMC layer in Sn–SiC/Cu solder.

Improving tensile strength of SnAgCu/Cu solder joint through multi-elements alloying

In this study, different content combinations of the Sb, Bi, Ni, In and Ce elements were added into the SnAgCu (SAC) solder, then the composite alloying effects of these elements on microstructure and properties of the SAC solder, and the interfacial reaction and tensile strength of the SAC/Cu solder joints were investigated. The results reveal that the melting ranges of the multi-alloyed solders are larger, and their wetting areas increase by different degree. More intermetallic compounds (IMCs) and some Bi particles are formed in the multi-alloyed solders and the solder grains are refined, which significantly increase the microhardness. The interfacial IMC layer change from single layered scallop-type Cu6Sn5 grains at the SAC/Cu interface to an agglomeration of fine (Cu, Ni)6Sn5 particles by the multi-element alloying, while the residual stress in the interfacial IMC layers can be released due to the decrease in the IMC grain size. Through solid solution strengthening, precipitation strengthening and fine grain strengthening of the solder and release of residual stress in the interfacial IMCs, tensile strength of the multi-alloyed SAC/Cu solder joints was significantly improved to 100–160 MPa, and the fracture location transfer from inside the solders close to the joint interface to inside the interfacial IMCs layer.

Convolutional neural network model for synchrotron radiation imaging datasets to automatically detect interfacial microstructure: An in situ process monitoring tool during solar PV ribbon fabrication

Designing means and methods to detect the presence of interfacial bubbles and intermetallic compounds (IMCs) during hot dipping solder coating of Cu ribbon, can help in the production of defect-free PV ribbons. A mechanistic study of Cu6Sn5 IMC grain growth and bubble morphology evolution at the solder-substrate interface is performed with phase field simulation. A machine learning model is utilized to identify the occurrence of bubble(s) and IMC at the material interface of liquid solder and solid Cu. The datasets for the microstructural images consisting of bubble(s), IMC and planar solder/Cu interface are generated using in situ synchrotron radiation (SR) imaging experiment techniques. The integration of in situ SR radiography based non-destructive testing experiments with convolutional neural network model to intelligently detect the interfacial microstructures paves the path for potential industrial application of this technique in the smart manufacturing of defect free and reliable PV ribbon material.

Interfacial microstructure evolution and properties of Sn-0.3Ag-0.7Cu–xSiC solder joints

Abstract The impacts of SiC on the wettability, mechanical properties and growth of intermetallic compound (IMC) of the low silver Sn-0.3Ag-0.7Cu (SAC0307) –xSiC composite solders paste prepared by mechanical mixing were investigated. It is found that there is an improvement in the wettability and a large reduction in the thickness of IMC with increasing SiC content, such as the contact angle shrinks by 11.48% and the thickness of IMC at the interface decreases by 63% with 0.10 wt% SiC addition. Meanwhile, according to the fracture morphology analysis, the IMC grains are refined repeatedly with increasing SiC content before less than 0.06 wt%, then agglomerated SiC and brittle phase Ag3Sn appear with further increase in SiC content. As a result, the tensile strength of solders joint increased continuously up to the maximum value of 30.49 MPa with 0.06 wt% SiC addition.

Influence of Ni foam/Sn composite solder foil on IMC growth and mechanical properties of solder joints bonded with solid-liquid electromigration

The effects of Ni foam addition and solid-liquid electromigration on the bonding of Cu/Sn-3.0Ag-0.5Cu/Cu joints under condition of 320 °C for 2, 4 and 8 h with the electric densities of 0, 3.33 and 6.67 × 102 A/cm2 were investigated. The results indicated that intermetallic compounds (IMCs) performed non-interfacial growth in the Cu/Ni foam/SAC305 system and were distributed in an island-like aggregation, and the asymmetric growth pattern of IMCs in both the cathode and anode sides disappeared after addition of Ni foam. In addition, the grain size of IMCs was significantly reduced and the tensile strength of the joints was enhanced by the addition of Ni foam. However, when the current density reached 6.67 × 102 A/cm2, the tensile strength of the joints containing Ni foam decreased dramatically after bonding for 8 h, this was due to the fact that IMCs grains were excessively coarse and the grain growth direction tended to be parallel to the current direction during bonding.

Amorphization and intermetallic nucleation in early-stage interfacial diffusion during Sn-solder/Ni solid-state bonding

As low-temperature interconnection processes for integrated circuit packaging increase in demand, a deeper understanding of the solid-state diffusion behavior between the bonding metals forming chip-to-chip joints is needed for process development and evaluation. In this study, by using a special electrodeposited Ni microcone layer to bond with solder at a solid state temperature of 200 °C, the role of early-stage interfacial diffusion in the formation of bonding could be interpreted. High-resolution microscopic observation revealed different diffusion products at different locations of the contacting solder and Ni microcones, which indicated the sequential formation of an amorphous layer and intermetallic compound (IMC) grains upon initial contact. The morphology and composition of the IMC grains formed at the solid-state contact interface were also influenced by the contact compactness and solder composition, owing to the distinct Ni supply conditions. A low bonding temperature of 100 °C resulted in poor interfacial adhesion and no visible product of diffusion, which corroborated that the interfacial diffusion product, even with a thickness on nanometer scale, can be an effective indicator of bimetal bonding for the low-temperature interconnection process.

Multiphase-field modeling of temperature-driven intermetallic compound evolution in an Al–Mg system for application to solid-state joining processes

Solid-state joining of dissimilar materials results typically in the formation of intermetallic compounds at the weld interface, which strongly determines the resulting mechanical properties. To tailor the joint strength, understanding of the formation of the intermetallic compound and their driving mechanisms is crucial. In this study, the evolution of temperature-driven Al3Mg2 and Al12Mg17 intermetallic compounds in an Al–Mg system for application to solid-state joining processes via a multiphase-field approach is numerically investigated. To this end, the CALPHAD approach to obtain the thermodynamic parameters of the relevant phases is used in conjunction with the multiphase-field model. The simulation results are qualitatively compared with experimental results in the literature in terms of thickness and morphology of intermetallic grains, exhibiting a reasonable agreement. The influence of grain boundary diffusion and interface energy on the morphology and kinetics of the intermetallic compound grains is investigated in detail with the established multiphase-field model.

Influence of Welding Speed on Characteristics of Non-Axisymmetric Laser-Tungsten Inert Gas Hybrid Welded Mg/Al Lap Joints with Zn Filler.

A non-axisymmetric laser-tungsten inert gas (TIG) heat source was designed to join Mg–Al dissimilar metals with pure Zn filler at a series of welding speeds (500–900 mm/min). Laser and TIG heat sources respectively acted on Al and Mg base metals to precisely control their dissolution into the welding pool. The solidification rate of liquid metal was controlled by adjusting the welding speed, then the reaction process of Mg, Al and Zn could be accurately regulated. The results indicated that various microstructures including Al solid solution, Zn solid solution, Mg–Zn intermetallic compounds (IMCs) and eutectic structure formed in the joint produced at different speeds. Lower welding speed (500 mm/min) caused the microstructure coarsening and higher welding speed (900 mm/min) would lead to the enrichment of MgZn2 intermetallic compounds. At the optimal welding speed of 800 mm/min in particular, fine MgZn2 IMCs grains uniformly distributed in the Al and Zn solid solution. The tensile-shear load reached a maximum of 1052.5 N/cm and the joint fractured at the fusion zone near the Al base metal.