Improving Surface Finish of Nickel Bond Pads for Wire Bonding on High Temperature LTCC Devices

Low temperature co-fired ceramic (LTCC) is a material used primarily for packaging embedded circuits. It is resistant to high temperatures and can be used in harsh environments, as well as high vacuum applications. LTCC is designed to be cofired with silver conductive paste, however this paste can only withstand temperatures of up to 400C in vacuum. A solution to this is to cover exposed areas of silver paste with a high-performance nickel paste post fire. This paste can withstand higher temperatures in vacuum. High performance nickel paste is not designed to be cofired with LTCC, so a new fabrication process was developed. Furthermore, the bond pads created with the nickel paste have a higher surface roughness, making it difficult to perform wire bonding to them. A dry sanding technique was developed to prepare the new nickel pads for wire bonding. Surface roughness was then measured using atomic force microscopy. Further processing of the bond surface with ion milling would then be performed following the initial sanding.