Preparation and Characterization of Electroless Deposited Fe-Ni-B Alloy Films

Abstract

We prepared iron–nickel–boron (Fe–Ni–B) alloy thin films using the electroless plating method. Their stress generation, thermal-stress, thermal-expansion, and crystal structure were evaluated. Changes in the coefficients of thermal expansion (CTEs), related to the crystal structure, depended on the Fe / Ni ratio in the obtained films, and the microstructure and grain size differed depending on the boron content. The microstructures and grain sizes affected the stress generated by film formation. In addition, the CTE values and change of crystal structure upon heating affected the thermal stress. These Fe–Ni–B alloy films in the Invar composition range with 55–63 wt% Fe contents showed lower CTE values and initial internal stress than those of Ni-rich Fe–Ni–B alloy films, and no structural change upon heating. Thus, an electroless deposited Invar Fe–Ni–B alloy film can be used as metallized films with high thermal suitability for reliable high-density packaging.