Thick-Film and LTCC Passive Components for High-Temperature Electronics

At this very moment an increasing interest in the field of high-temperature electronics is observed. This is a result of development in the area of wide-band semiconductors’ engineering but this also generates needs for passives with appropriate characteristics. This paper presents fabrication as well as electrical and stability properties of passive components (resistors, capacitors, inductors) made in thick-film or Low-Temperature Co-fired Ceramics (LTCC) technologies fulfilling demands of high-temperature electronics. Passives with standard dimensions usually are prepared by screen-printing whereas combination of standard screen-printing with photolithography or laser shaping are recommenced for fabrication of micropassives. Attainment of proper characteristics versus temperature as well as satisfactory long-term high-temperature stability of micropassives is more difficult than for structures with typical dimensions for thick-film and LTCC technologies because of increase of interfacial processes’ importance. However it is shown that proper selection of thick-film inks together with proper deposition method permit to prepare thick-film micropassives (microresistors, air-cored microinductors and interdigital microcapacitors) suitable for the temperature range between 150°C and 400°C

Optimisation of the performance characteristics of Cu-Al-Mo thin film resistors

This thesis presents a novel approach to the manufacture of thin film resistors using a new low resistivity material of copper, aluminium and molybdenum, which under industrially achievable optimised process conditions, is shown to be capable of producing excellent temperature coefficient of resistance (TCR) and long term stability properties. Previous developments in the field of thin film resistors have mainly centred around the well established resistive materials such as nickel-chromium, tantalum-nitride and chromium-silicon-monoxide. However recent market demands for lower value resistors have been difficult to satisfy with these materials due to their inherent high resistivity properties. This work focuses on the development and processing of a thin film resistor material system having lower resistivity and equal performance characteristics to that of the well established materials. An in depth review of thin film resistor materials and manufacturing processes was undertaken before the electrical properties of a binary thin film system of copper and aluminium were assessed. These properties were further enhanced through the incorporation of a third doping element, molybdenum, which was used to reduce the TCR and improve the electrical stability of the film. Once the desired chemical composition was established, the performance of the film was then fine tuned through optimisation of critical manufacturing process stages such as sputter deposition, heat treatment and laser adjustment. The results of these investigations were then analysed and used to generate a set of optimum process conditions, suitable for repeatedly producing thin film resistors in the 1 to 10? resistance range, to tolerances of less than ±0.25% and TCR values better than ±15ppm/oC