COPPER THICK-FILM SINTERING STUDIES IN AN ENVIRONMENTAL SCANNING ELECTRON-MICROSCOPE

The significance of the ElectroScan environmental scanning electron mi croscope (ESEM) as a processing tool for studying dynamic morphologica l changes under controlled temperature/atmosphere conditions was evalu ated. The ability to observe dynamic processes in situ, which cannot b e achieved by other means, is critical to understanding microstructura l formation. Processing of printed copper thick films on ceramics was used as a test case, wherein morphological changes associated with the steps of organic binder removal and sintering of copper particles wer e observed/examined in real time. Good agreement was seen between micr ostructures obtained in the ESEM and those achieved in a belt furnace when similar process variables were used. When processed in atmosphere s which were proven to induce sintering in a conventional belt furnace , sintering was evident in both cases, and the microstructural changes were documented on videotapes in real time. Determination of critical event temperatures was achieved-that is, binder burnout occurring bet ween 270-degrees and 350-degrees-C, onset of oxidation at 520-degrees- C, and sintering starting at 770-degrees-C. It was thus verified that the microstructural changes during the copper thick film sintering pro cess can be observed in situ using an ESEM. (C) 1993 Wiley-Liss, Inc.