Evolution Of Intermetallic Compounds Research Articles

Intermetallic compounds evolution between lead-free solder and cu-based lead frame alloys during isothermal aging

This paper investigated the intermetallic compounds (IMCs) formation between SnAgCu solder and four Cu-based lead frame alloys during reflow soldering and isothermal aging. Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) were used to study the cross-sectional microstructure and stoichiometric information. Optical Microscope (OM) was used to measure the mean thickness of IMCs. It was found that Ni and Sn trace element have important influences on the interfacial reactions. After soldering, for the case of Sn-Ag-Cu solder on Cu-Sn-Cr-Zn, Cu-Sn-P and Cu-Fe-P-Zn-Pb, an island type Cu6Sn5 and a thin Cu3Sn layer were formed at the interface. However, for the case on Cu-Ni-Si-Mg alloy, no Cu3Sn was detected and only a layer of ternary (Cu,Ni)6Sn5 was confirmed and some Cu6Sn5 particles was observed to disperse in the bulk solder. The top morphology of IMCs was also characterized after the solder was selectively etched away. The IMCs on the Cu-Ni-Si-Mg showed long rod-like shape, whilst the IMCs on the other three alloys appeared round. After different duration of aging at 150°C, all the IMCs grew thicker and the grain size became larger. The rod-like IMCs on Cu-Ni-Si-Mg gradually transformed into round shape and it was relatively smaller compared to that on the other three alloys. Moreover, the growth rate of IMCs on Cu-Ni-Si-Mg is the fastest among the four alloys.

Influence of interfacial reaction between molten SnAgCu solder droplet and Au/Ni/Cu pad on IMC evolution

Abstract Intermetallic compounds(IMC) formed at Sn-Ag-Cu solder droplet/pad interface during wetting reaction were investigated. Comparative studies of the IMC evolution during reflow and aging were also conducted. The results show that the wetting reaction between molten solder droplet and pad leads to the formation of Au-Sn compound at interface, but Au element is not fully consumed during wetting reaction. After reflow, all Au layer disappears from the interface, Au element is dissolved into solder and Au-Sn intermetallic compounds are precipitated in the bulk. Reaction between Ni layer and Sn-Ag-Cu solder leads to the formation of (CU x Ni 1- x ) 6Sn 5 layer at interface during reflow. According to the thermodynamic-kinetic of interfacial reaction, the wetting reaction at solder droplet/pad interface influences the phase selectivity of IMC evolution during reflow and aging process.

Investigation of interfacial microstructure and wetting property of newly developed Sn–Zn–Cu solders with Cu substrate

The interfacial microstructure and wetting property of the new (Sn–9Zn)–xCu (SZ–xCu, hereafter) solders with Cu substrate were investigated. During the reflow process, Cu5Zn8 compounds formed at the interface of SZ/Cu and when the Cu content is from 2 to 6% both Cu6Sn5 and Cu5Zn8 compounds formed at the interface. However, a nearly single scallop Cu6Sn5 layer was detected at the interface of SZ–8Cu/Cu and SZ–10Cu/Cu. The evolution of intermetallic compounds was due to the formation of short-range ordered Zn–Cu structures in the liquid solder which refrained the reactions between Zn and Cu substrate. The wetting property was improved remarkably with increasing Cu content in the SZ–xCu solder. The lower surface tension, which also resulted from the decrease of the activity of the Zn atoms by the formation of short-range ordered structure in the liquid solder, was the main reason for reaching a better wettability.

Evolution of iron aluminide in Al/Fe in situ composites fabricated by plasma synthesis method

The evolution of intermetallic compounds for Al/Fe in situ composites fabricated by the plasma synthesis method (PSM) was investigated through the microstructural analyses for the partially reacted particle region. The partially reacted particle is composed of Al/Al 13Fe 4/Al 5Fe 2/Fe layer. Based on the concept of effective free energy of formation, the first phase that nucleates on the interfacial layer of Al/Fe is determined as Al 13Fe 4. By the reaction of Al 13Fe 4 and Fe, Al 5Fe 2 forms and grows inward. Due to heat extraction by the reaction, the edge of Al 13Fe 4 dissolves to form angular Al 13Fe 4 in the matrix. By the reaction and decomposition of Al/Fe through the intermediate phase of Al 5Fe 2, the Fe particles transform to Al 13Fe 4 in the plasma synthesis method. In addition, the differences of main intermetallic compounds between by the hot dipping process and by the plasma synthesis method were discussed.

Radiation-induced collapse of the crystalline structure

A theory of irradiation-induced amorphization of ordered intermetallic compounds, based on the destabilization of the crystalline structure by excess defect accumulation, has been developed recently. The theory is reviewed starting with its phenomenological basis, where the microstructural evolution of intermetallic compounds that are rendered amorphous by irradiation is emphasized. Next, the analysis of defect buildup that suggests the formation of a stable complex defect consisting of a vacancy-interstitial pair, called a complex, is reviewed. The possibility of a radiation-induced microstructure such as interstitial clusters, in addition to complexes, in intermetallics that undergo the crystalline-to-amorphous transition is incorporated into the theory. A comparison of radiation effects in NiTi and in Zr 3Al is made using a rate theory approach. In the case of the aluminide, it is found that cluster development can hinder the amorphous transition when the material is irradiated with electrons. However, enhancement of complex production in the collision cascade explains the occurrence of the transition during ion bombardment.