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Interface characterization and mechanical properties of dual beam laser welding-brazing Al/steel dissimilar metals
摘要： The DP590 steel to AA7075 Al-alloy with lap configuration is successfully joined by dual beam laser welding-brazing without using filler metal. Through the introduction of the derived laser beam, the wetting angle, wetting distance and the thickness of intermetallic compound (IMC) layer are well improved and controlled. It is found that the wettability of liquid Al on steel improves with the increase of laser power, i.e. the wetting angle decreasing from 25.3° to 17.8° and the wetting distance increasing from 2.17 mm to 3.19 mm as the laser power increasing from 1.0 kW to 1.6 kW. Two kinds of IMC exist at brazing interface, one is η-phase (Fe2Al5) with flatten morphology closing to the steel side and the other is θ-phase (FeAl3) with needle-like morphology adjacent to the welding-brazing seam. The thickness of IMC layer increases from 8.37 μm to 12.12 μm with increasing laser power from 1.0 kW to 1.6 kW. Tensile test shows that both the wettability and the IMC thickness have influence on the welding-brazing joint strength. Poor wettability and too thick IMC layer will result in lower strength and fracture occurred in brazing interface. The optimal joint tensile strength of 123.7 MPa on average is achieved with the laser power of 1.4 kW.
关键词： Tensile strength,Welding-brazing,IMC,Dual beam laser,Al/steel dissimilar metals
更新于2025-11-28 14:24:20
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Microstructures and Mechanical Properties of Dissimilar Al/Steel Butt Joints Produced by Autogenous Laser Keyhole Welding
摘要： Dissimilar Al/steel butt joints of 6.0 mm thick plates have been achieved using fiber laser keyhole welding autogenously. The cross sections, interface microstructures, hardness and tensile properties of Al/steel butt joints obtained under different travel speeds and laser beam offsets were investigated. The phase morphology and thickness of the intermetallic compound (IMC) layers at the interface were analyzed by scanning electronic microscopes (SEM) using the energy-dispersive spectrometry (EDS) and electron back-scattered diffraction (EBSD) techniques. The results show that travel speeds and laser beam offsets are of considerable importance for the weld shape, morphology and thickness of IMC layers, and ultimate tensile strength (UTS) of Al/steel butt joints. This proves that the IMC layers consist of Fe2Al5 phases and Fe4Al13 phases by EBSD phase mapping. Increasing laser beam offsets from 0.3 mm to 0.7 mm significantly decreases the quantity of Fe4Al13 phases and the thickness of Fe2Al5 layers at the interface. During tensile processing, the Fe2Al5 layer with the weakest bonding strength is the most brittle region at the interface. However, an intergranular fracture that occurred at Fe2Al5 layers leads to a relatively high UTS of Al/steel butt joints.
关键词： laser keyhole welding,IMC layers,Al/steel joints,tensile properties,EBSD phase mapping
更新于2025-09-23 15:21:21
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Effect of Ni thickness on the IMC and reliability of ultrathin ENEPIG
摘要： Electroless Ni(P)/electroless Pd/immersion Au （ ENEPIG ） is a common surface finish featured by good solderability, wide application and reliable mechanical properties. With the miniaturization and high integration of the integrated circuits, high thickness of Ni-P will affect the signal integrity because of the gigantic resistance. This study focused on the effect of the Ni layer thickness on the morphology and evolution of IMC and the reliability of ENEPIG. Commercial SAC305 solders were reflowed on different thicknesses of Ni (0.3um and 3um) to study the Cu/Ni IMC evolution while OSP sample was used as a control sample. Aged experiments were conducted at 150°C to evaluate the long term thermal stabilization and After every aging stage, we conducted high speed shear test to estimate the mechanical strength of the IMCs and analysis of fracture morphology. After aging, scallop-shaped IMCs of (Cu,Ni)6Sn5 was formed and its thickness increased with aging as well. Brittle IMC (Cu,Ni)3Sn first began to appear in ultrathin ENEPIG and the shear strength dropped slightly. After 256 h aging, ultrathin Ni layer had been completely consumed and a large number of (Cu,Ni)3Sn formed while 5um ENEPIG still had a good barrier effect. Even if Ni layer had been consumed, ultrathin ENEPIG still had a certain inhibitory effect on IMC growth compared with OSP, probably because of the formation of NiSnP layer. Further drop tests and temperature cycle tests will be conducted and the failure models together with cause will be also presented combined with previous results of IMC evolution.
关键词： ENEPIG,Ni thickness,Reliability,Ultrathin,IMC
更新于2025-09-23 15:19:57
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Microstructure and mechanical properties of welding–brazing of Ti/Al butt joints with laser melting deposition layer additive
摘要： Laser welding–brazing of Ti/Al butt joints was performed with coaxial Al–10Si–Mg powders feeding. The experimental results indicated that a sound Ti/Al butt joint could be obtained by an additive layer approach. The influence of the laser melting deposition layers on the weld appearance, interfacial microstructure and tensile properties were investigated. High-quality joints were produced when five and seven layers were deposited. The morphology and thickness distributions of the interfacial intermetallic compounds (IMC) at the brazing interface along the thickness direction of the joint varied with the number of deposition layers. Continuous serrated IMC was obtained in joints produced by seven deposition layers, and the IMC layer was distributed homogenously along the thickness direction. The maximum thickness difference of the IMC was only approximately 0.12 μm. The microstructure of the IMC layer was composed of a nanosized granular Ti7Al5Si12 phase and serrated Ti(Al, Si)3 phase. The maximum tensile joint strength reached 240 MPa, 80% of that of the aluminum base metal, and the lower tensile strength of the other joints was caused by insufficient IMC layer or a porosity defect.
关键词： Tensile strength,Laser melting deposition,Interfacial IMC,Laser welding–brazing,Ti/Al butt joint
更新于2025-09-19 17:15:36
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[IEEE 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Las Vegas, NV, USA (2019.5.28-2019.5.31)] 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) - Vertical Laser Assisted Bonding for Advanced "3.5D" Chip Packaging
摘要： In this work the processes of laser assisted bonding (LAB) is compared to thermal compression bonding (TCB). Their respective advantages and disadvantages regarding the assembly of flip chip stacks are compared. It is found, that the LAB allows for faster processing, negligible compression force and creates less internal stress in the chip stack. The concept of “3.5D” stacking is introduced. This new concept allows for the vertical bonding of chips/semiconductors to the sides of a chip stack. The vertically bonded parts can be used to contact the layers, which eliminates the individual necessity for through silicon vias (TSVs).
关键词： 3D-packaging,Silicon interposer,Thermal compression bonding (TCB),Inter metallic phase (IMC-layer),Laser assisted bonding (LAB),System on Package (SOP),Laser beam modulation,vertical Flip Chip bonding
更新于2025-09-16 10:30:52
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Laser welding of dissimilar copper and aluminum sheets by shaping the laser pulses
摘要： Dissimilar metal joining of thin copper and aluminum sheets is very important in the battery connections. The main problem while joining this dissimilar combination is formation of brittle intermetallic phases that degrade the electrical and mechanical properties of the joint. For joining copper and aluminum sheet with laser, very high intensity in the range of 107 W/cm2 is required. Intermixture of copper and aluminum is vital for joint ductility. In this paper, the effect of combined oscillation and shaping of the laser pulses on the overlap welding of copper-aluminum is studied. Precise control of intermixing can be achieved by modifying the laser pulse i.e. the percentage of power with respect to the pulse time. Investigation on different pulse shapes with ramp up and ramp down profile is conducted by cross-section and microstructural analysis.
关键词： Pulse modulation,Dissimilar metal joining,Cu-Al joints,Laser welding,Intermettalic compounds (IMC)
更新于2025-09-12 10:27:22