UV-LIGA Based Discrete Fabrication Process for Terahertz Corrugated Feed Horn

Abstract Corrugated horn is a kind of key feed component of antenna system, which could be fabricated by electroforming method. However, the feed horn is becoming more difficult to electroform with the increase of frequency. In the terahertz band, which is now of great interest in military and social safety application, the widths of the corrugation teeth and gaps decrease to the micrometer scale, and their depth-width ratios are higher than 2:1. It is really a challenging, time-consuming work to directly machine a terahertz feed horn or make a metal mandrel for electroforming of that. To solve the difficulties in the normal process of terahertz feed horn, a novel discrete fabrication method based on UV-LIGA technology is put forward avoiding the need of mandrel machining. In this method, the manufacturing of a 3D corrugated horn is transformed into 2D slices forming, that is, the corrugation structure is separated into discrete slices according to the width of each tooth or gap. The slices are formed through UV-LIGA technology, in which electroforming is an essential process. Consequently, slices with micro hardness higher than 250HV(200g) and internal compress stress less than 20MPa were electroformed. After assembly and vacuum bonding of slices, typical nickel micro-structure of a conical corrugated horn operating at frequency 2.5THz was fabricated successfully. This layer-by-layer method breaks though the traditional solution of direct machining of metal feed horn or its mandrel by coupling UV-LIGA and vacuum hot bonding technology, which is feasible for vacuum electronic devices like rectangular folded waveguide and multilayer MEMS components moreover.