Interconnection of micropad electrodes by controlled "extraneous" deposition of electroless NiB film

A method of interconnecting micropad electrodes was developed by using the electroless deposition of NiB for application to the flip-chip bonding technology. The phenomenon of "bridge" formation by the so-called "extraneous deposition" was utilized as a technique to perform selective deposition of NiB on noncatalytic surfaces. The process of extraneous electroless deposition was controlled by optimizing deposition conditions so that the deposit grew anisotropically along the surface between the facing pads. Practical feasibility of this technique was demonstrated by forming an interconnection between pads separated by 5 μm and measuring 5 μm in both height and width. This method was applied successfully to interconnecting the pads forming an array with a pitch of 20 μm.