Solder reaction-assisted crystallization of electroless Ni–P under bump metallization in the Si/SiO2/Al/Ni–P/63Sn–37Pb multilayer structure was analyzed using transmission electron microscopy, scanning electron microscopy, energy dispersive x-ray, and electron probe microanalyzer. The electroless Ni–P had an amorphous structure and a composition of Ni85P15 in the as-plated condition. Upon reflow, the electroless Ni–P transformed to Ni3Sn4 and Ni3P. The crystallization of electroless Ni–P to Ni3P was induced by the depletion of Ni from electroless Ni–P to form Ni3Sn4. The interface between electroless Ni–P and Ni3P layer was planar. From the Ni3P thickness-time relationship, the kinetics of crystallization was found to be diffusion controlled. Conservation of P occurs between electroless Ni–P and Ni3P, meaning that little or no P diffuses into the molten solder. Combining the growth rates of Ni3Sn4 and Ni3P, the consumption rate of electroless Ni–P was determined. Based upon microstructural and diffusion r...

Solder reaction-assisted crystallization of electroless Ni-P under bump metallization in low cost flip chip technology

Characterization of nickel-based microlattice materials with structural hierarchy from the nanometer to the millimeter scale

A novel approach to texturing a landing zone at the inner diameter of a magnetic disk is presented. The technique employs a high repetition rate short-pulsed laser to create discrete topographical features with rounded, dome-like protrusions ("bumps"). These bumps serve as smooth support points for the contacting slider. The laser texture technique provides precision in the landing zone placement while eliminating the transition zone of a mechanically textured landing zone. It also provides excellent tribological performance in terms of low contact start/stop stiction and good durability.

A new laser texturing technique for high performance magnetic disk drives

Friction and wear behavior of electroless Ni–P and Ni–W–P alloy coatings

Electroless Ni-plating on Mg alloy AZ91 has been studied to understand the effect of the substrate microstructure and roughness on the deposition rate, nucleation, coating microstructure, and mechanical property of the coatings. Experimental results indicate that the growth of Ni deposit in the early stage was influenced by the substrate microstructure and roughness. The electroless Ni-plating on the abrasive blasted AZ91 (rough) substrate showed a higher deposition rate than that on the finely polished one, indicating that the mechanical roughening enhances the nucleation and coalescence of Ni crystallites. Scratching tests showed that higher coating adhesion is achieved on the roughened AZ91 substrate. Wear tests, however, showed that the Ni plating on the rough substrate has a higher friction coefficient than that on the polished surface. The hardness and adhesion property of Ni coatings before and after heat treatment were also characterised.

Electroless nickel plating on AZ91 Mg alloy substrate

Studies on crystallization of electroless NiP deposits

Effect of phosphorus content on the relative proportions of crystalline and amorphous phases in electroless NiP deposits

Electroless Ni-P-B deposits with weight percentages of 0.72 P and 4.15 B; 1.87 P and 4.87 B, were observed to be a mixture of microcrystalline nickel and amorphous phases, based on X-ray diffraction and transmission electron microscopy. On annealing, Ni 3 P and Ni 3 B precipitated along with crystalline nickel in one step. The microhardness of the deposits showed typical precipitation hardening behavior, with hardness increasing from about 550 VHN in the as-deposited condition, to about 1000 VHN in the fully crystallized condition

P. Sampath Kumar

Papers

Studies on crystallization of electroless NiP deposits

Effect of phosphorus content on the relative proportions of crystalline and amorphous phases in electroless NiP deposits

Structural Transformations in electroless Ni-P-B deposits