Papers by Keyword: Intermetallic Compound (IMC)

Abstract: A new dual beam laser deep penetration welding technology for lap joint of 1.5 mm thick aluminum alloy and high strength steel was explored in this paper, and the effects of three different beam energy ratios (R_S=0.25,0.33,0.5) on weld formation, interface microstructure and mechanical properties were studied. The result shows that under certain conditions of other parameters, double beam laser deep penetration welding process can be applied to lap joint of aluminum alloy / high strength steel with good weld shape when R_S=0.25,0.33,0.5. As R_S increases from 0.25 to 0.5, the penetration of the weld reduces from 575 μm to 424.2μm, the thickness of intermetallic compound (IMC) layer at the interface between aluminum alloy and weld metal reduces from 3.4 μm to 2.5 μm, the average microhardness of the IMC layer decreases from 771.1 HV to 571.9 HV, the mechanical resistance of the joint raises from 95.7N/mm to 115.2N/mm. When R_S=0.5, double beam laser deep penetration welding of aluminum alloy / high-strength steel joints has the highest mechanical resistance of joints, because of the relatively good plastic ductility of the joint.

Abstract: The correlation between intermetallic compound (IMC) and interface bonding state of the pure Al/08Al steel clad plate after 645°C/1h diffusion annealing was studied using the SEM. The results indicated that after 645°C/1h diffusion annealing for the pure Al/08Al steel clad plate, the IMC grew continuously along the interface with the thickness of 2-6 μm, while, at some regions grew abnormally with the thickness up to 10-30 μm. Moreover, some intrinsic defects at the interface, such as voids in the abnormally grown IMC and micro cracks along the interface were observed. The voids were possibly caused by huge difference of Al and Fe in diffusion coefficient, which is known as Kirkendall effect. On the other hand, the micro cracks could be attributed to the thermal stress during the cooling process because of larger difference of thermal expansion rate between Al and Al-Fe IMC. The intrinsic defects at the interface of Al/Steel could supply a novel way to correlate the morphology of IMC and interface bonding strength.

Abstract: In this work, B (boron) was added into Sn-1.0Ag-0.5Cu (SAC105) solder alloy using mechanical alloying method in order to develop a new low-silver lead-free solder, Sn-1.0Ag-0.5Cu-xB, where B ranges from 0wt% to 0.2wt%. The melting characteristics, wettability, mechanical properties of welded joints, and microstructure of this solder were studied. The results showed that with adding B into SAC105 alloy, the melting point and melting range was not obviously changed. Although the wettability decreases with the B content increasing, the solder joints exhibited higher shear strength. As a result, the shear strength was the highest at the B content of 0.2wt%. For example, the shear strength of the Sn-1.0Ag-0.5Cu-0.2B solder was 35.12MPa, while that of the B free SAC105 solder was only 28.94MPa. Furthermore, adding B had a significant effect on grain refinement on the SAC105 solder . Observations on solder matrix and weld joints by SEM showed that the IMC thickness of solder joints with the addition of B was less than the SAC105 lead-free solder. Moreover, with the addition of B, the solder grains were refined obviously which had the effect of refining straitening, and the growing rate of brittle IMC in solder joint could be effectively reduced during soldering and aging process. Thus solder joint performance can be improved significantly.

Abstract: Aluminum foam sandwiches (AFSs) served as sheet materials have enormous marketing potential for their interesting combinations of excellent properties, such as low density, high specific strength, energy absorption and thermal insulation. In this paper, transient liquid phase (TLP) bonding method was used to prepare pure titanium sheet enhanced AFS (TS-AFS). Fabricated TS-AFS with the dimension of 80×80×18 mm³ presented uniform foam core, and bubbles ranged from 0 mm to 2 mm occupied the most area of cross section. Thickness of interface layer increased with the increase in the holding time. Additionally, metallic compounds of Al₂₀CaTi₂ and Al₂Ti were detected at the bonding joint.

Abstract: Copper-clad aluminum (CCA) composite wires have been widely used in cable industry. Especially for the application in aerospace, the light weight character of wires is particularly important. To improve the mechanical properties of wires, Cu-Ni-Si alloy and Al-Mg-Si alloy are employed to replace pure copper and pure aluminum, respectively. The objective of this work is to find the appropriate annealing treatment conditions to produce the Cu-Ni-Si/Al-Mg-Si clad composite wires with optimal combination properties. The wires were fabricated by a drawing process and heat treatment at different temperatures and times. Mechanical and electrical properties dependent on outer Cu-Ni-Si, internal Al-Mg-Si and interface properties, are characterized and analyzed. The fracture behavior of Cu-Ni-Si/Al-Mg-Si clad composite wires was studied together with the stress-strain curves of the composite wires.

Abstract: The effect of Al and Si addition on IMC formation at the solder and Cu substrate interface was investigated. The compositions of the solder alloy used are Sn-0.3 wt.% Ag-0.5 wt.% Cu (SAC0305), SAC0305-1 wt.% Al (SAC0305-1Al), SAC0305-2 wt.% Al (SAC0305-2Al) and SAC0305-2 wt.% Al-2 wt.% Si (SAC0305-2Al-2Si). Solder alloys were prepared by casting process. Melting temperature of each solder alloys was determined using DSC. Reflow process of the solder alloys were carried out at 260 ^oC on Cu substrate. Morphology of the intermetallic compound (IMC) formed at the solder joint was observed using Fe-SEM equipped with EDX. The addition of Al and Si reduced the thickness of IMC layer formed at the solder joint. The addition of 1.0 wt.% Al formed planar shape of IMC while the addition of 2.0 wt.% Al and 2.0 wt.% Al with 2.0 wt.% Si formed scallop shape of IMC. This is due to Cu-Al IMC and Ag-Al IMC scattered near the interface that act as diffusion barriers to Sn diffusion. This suggests that the addition of right amount of Al and Si could form thinner IMC layer that could lead to increase of reliability of solder interconnect.

Abstract: This Paper Reports the Microstructure, IMC Evaluation and Wettability of Low-Ag Sn-Ag-Cu(SAC) (0.3 Wt% Ag and 0.5 Wt% Ag) and SAC305 Solder Alloys in Reflowed and Agedconditions. Reflow was Done at 250°C and Thermal Aging at 150°C For100 Hours. Microstructure of Bulk Solder and the IMC Formed at Interfacebetween Solder and Cu Substrate were Observed Using SEM Equipped with EDX. Microstructureobservation Showed Finer β-Sn Dendrites at 0.3%Ag Indicating a Possiblerefining Effect of Lower Ag on Bulk Solder Microstructure. SEM Result Showedfiner Ag₃Sn Distributed in the Solder but the IMC Thickness of Bothreflowed and Aged Solder Joint Seems to Increase with Decreasing Ag Content.This could be due to Finer β-Sn Dendrites which Provide more Diffusion Paththrough Grain Boundaries and Increase IMC Thickness. Similarly, Lower Ag Content Appears to have Detrimental Effect on Wettability and Wetting Angle Ofsolder Joint.

Abstract: An impetus has been provided towards the development of lead-free solders by worldwide environmental legislation that banned the use of lead in solders due to the lead toxicity.This study focus on Bi-Ag and Bi-Sb solder alloys, in compositions from 1.5 to 5 wt % Ag and Sb. The effects of Ag and Sb amount, and reflow number on the microstructure and morphology of solder bulk were analysed by optical microscope and scanning electron microscope-energy dispersive X-ray. Based on the results, the grain boundary grooving was observed in all samples except Bi-5Sb in all three reflows. Metallurgical and chemical reaction between interface and solders were found in Bi-5Sb solder alloys in different reflow numbers which lead to appearance of Cu₃Sb intermetallic compound layer at the interface. Reflow numbers had a significant effect on the size of Cu-rich phase. Also it was observed that, with increasing reflow number Bi-Cu phase found in Bi-2.5Sb solder dissolves into the solder bulk.

Abstract: This work summarizes the interfacial reaction between lead-free solder Sn-3.5Ag and electrolessly plated Ni-P metallization in terms of morphology and growth kinetics of the intermetallic compounds (IMC). Comparison with pure Ni metallization is made in order to clarify the role of P in the solder reaction. During reflow, the IMCs formed with the Ni-P under-bump metallization (UBM) exist in chunky crystal blocks and small crystal agglomerates, while the ones with the sputtered Ni UBM exhibit uniformly scallop grains with faceted surfaces. The IMC thickness increases with reflow time following approximately a t^sup 1/3^ power law for both systems. The IMC growth rate is higher with the Ni-P UBM than the Ni UBM. The thickness of the Ni^sub 3^Sn^sub 4^ layer increases linearly with the square root of thermal aging time, indicating that the growth of the IMCs is a diffusion-controlled process. The activation energy for Ni^sub 3^Sn^sub 4^ growth in solid-state reaction is found to be 110 kJ/mol and 91 kJ/mol for the Ni-P and sputtered Ni UBMs, respectively. Kirkendall voids are detected inside the Ni^sub 3^P layer in the Sn-3.5AgTNi-P system. No such voids are found in the Sn-3.5AgTNi system.

Abstract: In this paper, micro interfacial behavior for Sn3.5Ag0.5Cu (SAC305) lead-free solder on Cu-Ni-Au substrate has been carefully investigated. It is observed that the intermetallic compound (IMC) ingredients along the SAC305 solder on the Cu-Ni-Ag substrate are (Ni, Cu)₃Sn₄ and (Cu, Ni)₆Sn₅ after reflow process. Reliability analysis for IMC ((Ni, Cu)₃Sn₄ and (Cu, Ni)₆Sn₅) was conducted based on the measurement of IMCs thickness and ball shear force. Temperature effects were also included in the analysis. The ingredients of IMC remain un-change if the working temperature is below 400 ^OC. Diffusion rate of interfacial controlled reaction was found to be depended on the annealing temperature. The IMC layer thickness decreased as the ramp-up rate of reflow temperature was increased for all cases studies. Preliminary results demonstrated that the measured ball shear force slightly changed for all different IMC thicknesses.