Abstract
Being irradiatd by a KrF laser, the electrical conductivity of polyimides (BPDA/p-PDA, BPDA/DDE, PMDA/ DDE, PMDA/BAPB) is increased permanently. At lower total laser fluences than about 50mJ/cm2, capacitive conductance can be obtained. Irradiated surfaces were firstly structured by powdery falling-back products, and then the formation of flakes was observed at the irradiated area. In this range, both nitrogen and oxygen contents were decreased with increasing total fluences. In the range of total fluences higher than 50mJ/cm2, the laser-induced conductivity consists from D.C. conductive low frequency region and capacitive high frequency region. The energetic laser shots sputtered and/or melted these flakes and formed electrically conducting rough surfaces remaining after ablation. Unusual compositional changes were observed at about 54mJ/cm2. For higher fluences, carbon-rich surfaces with a unified bonding environment (aromatic rings, carbon clusters and etc.) are found to be produced.
