Etch Pit Formation Model During Chemical and Electrochemical Etching in Polycarbonate Foil

Abstract

In addition to conventional chemical etching (CE), electrochemical etching (ECE) is usually required for the initial tiny α tracks in polycarbonate (PC) to enlarge to visible etch pits. A model based on the «vertical effective range» is proposed. The vertical effective range is a modified concept of the vertical mean range, and indicates the spot on the α trajectory which possesses the ability to cause electrochemical discharge. From both the theoretical and empirial approaches, the features of the transformation of an α tracks into an electrochemical etch pit are explained consistently as follows ; (1) if the vertical effective range of α tracks is contained in the bulk etched layer of ECE, electrochemical etch pits are created by electric treeing, (2) if the vertical effective range of α tracks is included in the mayer removed by preliminary CE, the α tracks are transformed into microscopic chemical etch pits, (3) once α tracks are converted inot chemical etch pits, they will never be detected as electrochemical etch pits