Abstract
Aluminium thick film conductors offer very large cost advantages compared with noble metals and can also improve the reliability of circuits by eliminating gold-aluminium interfaces and their attendant intermetallic phenomena. To date however, it has not been possible to produce aluminium thick film conductors which are ultrasonically bondable to aluminium-silicon wire.This paper describes a study of the microstructure and line profile of a commercially available aluminium thick film paste as a function of firing schedule. Scanning electron microscopy has revealed the mechanisms which control the sintering process and has suggested a revised firing schedule. It is shown that firing schedules exist which yield conductors with adequate ultrasonic bondability and conductivity. The results of bond ageing experiments on bond strength and conductivity are given for periods of up to 1200 h at temperatures of 60–200℃.It is shown that bonds of aluminium wire to aluminium thick film are resistant to loss of bond strength but suffer from loss of conductivity on ageing at 150℃.