Ferrules are key components of fiber-optic connectors. We successfully molded plastic ferrules for single-mode applications by injection molding process using LCP (Liquid Crystalline Polymer composite). In this paper, we investigated the outer diameter precision profile of plastic ferrules and the mold structure dependence of the dimensional accuracy of the ferrules. Using 3-dimensional (3D) flow analysis, we calculated the temperature and density distribution profiles of ferrules during the cooling process. Two types of mold structures were investigated, Y-type model (conventional model) and M-type model (newly proposed model). For the Y-type model, a large temperature and density distribution was observed especially in the ferrule front side. For the M-type model, the inhomogeneity was decreased dramatically.
In order to validate the 3D simulation predictions, molding experiments were performed. For the Y-type molded ferrule, a sink mark of about 5μm was observed at the ferrule front side. On the other hand, the sink mark disappeared for the M-type ferrule and the outer diameter change along the length was within ±1μm. The proposed M-type structure proved to be effective for the molding of high precision plastic ferrules.
