Al electrodes are well known as ohmic contact electrodes for the PTC component , the influence of their thickness on final component properties was investigated by comparing their ohmic characteristics with the ones of InGa electrodes . After observing the Al paste physical and chemical behaviors during rising temperature by thermal analysis (DTA), the firing operation of Al electrodes could be divided into three main subsections: the temperature rising time (tr), the peak firing temperature (Tp) and the hold time at peak firing temperature (th). The effects of these three parameters on final component properties were discussed in detail.