Lapping and polishing of different LTCC substrates for thin film applications

Substrates made of Low Temperature Cofired Ceramics offer high integration capabilities and good high temperature properties. Because the surface roughness of commercial, free sintered LTCC substrates is higher than 300 nm, LTCC substrates show a poor performance for thin film applications. One way to improve the surface quality is lapping and polishing. Lapped LTCC substrates show a very good flatness. To reduce the surface roughness Ra below 100 nm, the substrates must be polished after the lapping process. In this publication the lapping and polishing process of different LTCC materials is compared. All processes were realized on a Logitech PM5 precision lapping and polishing system, which is built for research and low volume production. Three different LTCC substrate materials were lapped and polished with different polishing agents. The roughness of the polished substrates was measured by laser scanning microscopy, chromatic confocal microscopy and regular tactile measurement technologies.