Study of mechanical response in micro-indentation of laminated ceramic green substrates

Micro-indentation at elevated temperature is an effective method for studying the mechanical response of a material used in micro embossing. In this study, micro-indentation was performed on co-firable green ceramic substrates for the purpose of simulating micro embossing process and investigating the mechanical response at certain temperature. The laminated low temperature co-firable ceramic (LTCC) green tapes were used as the testing materials, the correlations of indentation depth versus applied force at various temperatures ranging from 25 to 75°C were studied. The results showed that permanent indentation cavities could be formed and retained at the temperatures ranging from 25 to 75°C; the depth of cavities created was applied force, temperature and holding time dependent. Creep during holding period occurred and made a significant contribution to the plastic deformation at elevated temperatures. There were instantaneous recoveries during the unloading and cooling processes, and retarded recovery in the first day after indentation as well. No significant pile-up around the indented cavities at the temperatures up to 75°C was observed, suggesting that there was little material flow during indentation at this temperature range. The indented cavities on green ceramic substrates were formed mainly due to the plastic deformation under compression. The findings could be used as a guideline for micro embossing of ceramic green substrates.