Papers by Keyword: Intermetallic Growth

Abstract: Sn whisker growth on Cu substrate Pb-free solder is a serious problem in electric and electronic devices and as well as in aerospace applications. Due to the concern on the toxicity of lead by Restriction of Hazardous Substances Directive (RoHS), new lead free materials have been developed, and this resulted in the resurfacing of Sn whisker. The compressive stress, corrosionand surface oxide have been identified as the driving force for Sn whisker formation induced by mechanical alloying and oxidation. In this paper, we report the study to understand the mechanism of Sn whisker growth that control whisker formation on Sn finished.Based on the review, a preliminary conclusion has been made, where the analysis of the topography and microstructural characterization can be determined by evaluating under various environmental influences.Furthermore, the whisker growth happening on lead-free soldered can be considerably reduced by controlling the compressive stress in the solder which initiates the growth of intermetallic compounds (IMCs).

Abstract: The wettability of Sn-Cu-Ni with Germanium (Ge) additions of 0 ppm, 10 ppm, 60 ppm, 100 ppm and 200 ppm were investigated with Gen3 machine. The range of the wettability shows the lowest and the highest reading of wetting time and maximum force. Three different conditions were investigated which consist of as soldered, reflowed and aged. Further interfacial IMC observation was done for 0 ppm and 60 ppm of Ge to investigate the growth of interfacial IMC after thermal aging. From the measurement, the thickness of IMC for 0 ppm Ge is 2.075μm, 3.936μm and 4.502μm with aging time at 24,120 and 240 hours respectively. While for 60 ppm Ge, the IMC thickness are much lower with 1.8μm, 3.11μm and 4.154μm at the same aging time with 0ppm Ge. The results indicate that 60 ppm of Ge in Sn-Cu-Ni has the lowest wetting time, higher maximum force and slow IMC growth.

Abstract: Stress relaxation processes accompanying intermetallic growth during reactive diffusion between Cd and Ni have been studied by the methods of optical and scanning electron microscopy, provided with X-ray microanalysis. The experiments were carried out with the two-layer Cd-Ni samples at 250 and 280oC under hydrostatic pressures 350-900 MPa. The observed processes have been compared with those occurred at low pressures to demonstrate that the mechanisms of stress relaxation and thus the kinetics of intermetallic growth essentially depend on applied hydrostatic pressure. New mechanisms of stress relaxation were found, such as Cd extrusion and Cd whisker growth, which accompanied formation of Cd21Ni5 compound. It is shown, that the whisker growth is more probable at lower temperatures when the grain size is smaller, and the stress gradient, which support a driving force for whisker formation, is higher. An atomic mechanism for whisker growth, based on diffusion climbing of dislocation loops produced by Bardeen-Herring source for building new atomic layers, has been discussed.