DRIFT Analysis of Polyimide After UV Laser Irradiation

DRIFT Analysis of Polyimide After UV Laser Irradiation 

During the past three decades, since the commercialization of Kapton polyimide, an impressive variety of polyimides have been synthesized [258, 259]. Polyimides possess outstanding key properties, such as thermooxidative stability [260], high mechanical strength [261], high modules, excellent electrical [262] and optical properties [263, 264], and superior chemical resistance [265]. Recently polyimides have also been applied as membranes for gas separation [266, 267]. Approximately 15 years ago the direct structuring or laser ablation of polyimides by excimer lasers was first described [73, 130]. 

The XeCl laser (308 nm)-induced decomposition of Kapton is studied to identify reaction steps leading to the previously mentioned gaseous products, and to identify the intermediate steps of the surface carbonization of Kapton. The XeCl laser is applied in the industrial processing of polyimide due to the reliability of its optical and laser components at the emission 

Laser Ablation of Kapton with 308-nm Irradiation. The laser ablation of Kapton at 308 nm has been studied previously in detail [276]. An ablation threshold of 40 mj cm-2 has been determined for the same Kapton samples and the same experimental setup as in this study. The term ablation threshold is defined in this study as the laser fluence necessary to remove polymer material in the irradiated area, measured by a profilometer. For this study we used laser fluences below, at, and above the threshold of ablation of Kapton films. 

Irradiation of the SiC Substrate. The stability of the SiC disks under laser ablation conditions was tested first. A spectrum of a SiC disk was used as background. The difference spectra of the SiC disk after irradiation with the highest fluence applied in this study (155 mj cm 2) were measured after various pulse numbers (50, 100, 500, and 5,000) and at the highest repetition rate (10 Hz). No changes in the spectra were observed, suggesting that SiC is stable under the applied conditions. 

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