To develop the MEMS cap bonding process without cavity formation, we electroplated Cu/Sn rim structures and measured the bonding characteristics for the Cu/Sn rims of $25{sim}400{mu}m$ width. As the effective device-mounting area ratio decreased and the failure strength ratio increased for wider Cu/Sn rim, these two properties were estimated to be optimized for the Cu/Sn rim with 150 ${mu}m$ width. Complete bonding was accomplished at the whole interfaces of the Cu/Sn packages with the rim widths of 25 ${mu}m$ and 50 ${mu}m$. However, voids were observed locally at the interfaces with the rim widths larger than 100 ${mu}m$. Such voids were formed by local non-contact between the upper and lower rims due to the surface roughness of the electroplated Sn.