Cordierite-based dielectric thick films on an oxidized copper layer: Microstructural evidence of copper diffusion

Cordierite-based dielectric thick films deposited by screen-printing on a C u2O-Cu-96% alumina substrate were investigated with regard to microstructur al characteristics, densification, and crystallization. Compared to direct deposition of the cordierite layer on metal Cu, the use of the Cu2O layer a s a diffusion barrier caused the cordierite thick film to become more stabl e without any significant interaction layer at the film interface after fir ing at 920 degrees C for 30 min in a N-2 atmosphere. On the other hand, mic rostructural observation of the cordierite thick films on the Cu2O revealed some evidence of Cu diffusion into the cordierite thick films, i.e., incor poration of Cu into the cordierite and remaining glass, and as Cu precipita tes. Additionally, the diffused Cu was found to significantly affect densif ication and crystallization of the thick films, resulting in lower densific ation and crystallization temperatures. An XRD analysis supported the Cu in corporation from the Cu2O layer into the cordierite by showing the disappea rance of Cu2O phase at 700 degrees C, which is below densification temperat ure.