This paper describes an application of the LIGA technology to the fabrication of optical fiber ferrule mold inserts with twelve channels. It presents the overall process from mask design, mask fabrication, deep x-ray lithography exposure, resist development, nickel electroforming, as well as surface finishing to attain the final result. Several deep x-ray mask-making methods are explored, including mechanically machined masks, micro-EDM masks, and electron beam written masks. The exposure, development and electroforming to fabricate nickel molds up to 500 micrometers thickness are reported in this study. Nickel structures for fiber ferrule mold insert with twelve channels made by electroforming are the final products. A practical method to finish the microstructure surface is presented. Channels with diameter precision -0.0/+0.5 micrometers and pitch alignment of 0.25 micrometers were accomplished to satisfy the requirements of the research sponsor for inserting and aligning 125 micrometers single-mode fibers.