Anisotropic deposition of localized electroless nickel for preferential bridge connection

Preferential bridge connection by localized electroless NiB deposition was investigated. The phenomenon of "bridge" formation by so-called extraneous deposition was utilized as a technique to perform the selective deposition of NiB on organic surfaces. The films used for bridging were preferentially deposited in the area between facing pads. The deposition proceeded in the direction perpendicular to the surfaces of the facing pads. The occurrence of this anisotropic deposition strongly depends on solution diffusion, and the fabrication of a connection could be controlled by changing the pattern and pad dimensions. This method does not use a resist pattern for selective deposition; thus, it is a high throughput maskless fabrication process for the connection between separated pads. Using this technology, a preferential bridge connection for a pad array with a 5μm pad width, a 5 μm pad height, a distance of 5 μm between the facing pads, and a 20 μm pitch was fabricated. Moreover, the combined use of localized electroless deposition and conventional electroless deposition on the bridging film is expected to realize for pad-to-pad connections with low electric resistance.