A Cost-Effective MEMS Cavity Packaging Technology for Mass Production

Cost effective microelectromechanical system (MEMS) packaging methods have been required, because the cost portion of the MEMS package is more than 80% of the manufacturing cost of a MEMS device. For this reason, cost-effective MEMS packaging is proposed in this paper for mass production using copper (Cu) lead frames (L/F) as a preplated frame (PPF). Package types include an epoxy molding compound (EMC) cavity wall and an on-frame type. The EMC-cavity package consists of a substrate, a cavity wall and a flat lid on top of the cavity. The on-frame package has a folded lid without a cavity wall. Finite element method (FEM) numerical modeling is performed to anticipate the mechanical warpage and stress of the packages. Assembled MEMS cavity packages were tested for wire pulling, lid pulling, hermetic test, and reliability tests in order to prove the feasibility of this packaging. The wire bonding strength was improved by 40% using plasma cleaning before wire bonding. Through a lid pulling test, a lid bonding strength of 2.40 kgf on average was obtained using an epoxy adhesive. Finally, all samples of the packages passed the reliability tests of the TC, HAST, and HTST, standardized by Joint Electron Device Engineering Council (JEDEC). Also, this cavity package showed excellent hermeticity through leak tests.