Properties of power electronic substrates based on thick printed copper technology

- Principles and characteristics of particular firing phases in inert gas batch furnace
- Morphology and film properties of the fired copper films
- Evaluation of copper pastes for TPC technology
- Firing of up to 300 μm thick copper film in inert gas batch furnace

The aim of this work is to develop new metallisation procedures of 96% alumina substrates with copper using thick film technology and firing in a special batch furnace, designed for the process. Standard firing process of copper pastes is done in conveyor furnaces and it has been described in literature. The firing process in batch furnaces is characterised by different problems and it has not yet been published. The developed batch furnace can combine firing in a protective atmosphere e.g. that of high nitrogen purity gas, automated mixing of different gases, and evacuation of the furnace chamber using rotary pump. The work is concentrated on Heraeus pastes that make it possible to reach up to about 300 μm film thickness and, if needed, high resolution pattern of lower film thickness on the same substrate, metallised through holes and application of ENIG metallisation. Principles and characteristics of particular firing phases in the batch furnace as well as morphology and film properties of the fired copper films are described in the paper. The whole metallisation process proved to be effective offering high quality substrates for power electronics at reasonable investment and production costs.

484