This paper reports a study of a micro-EDM process to fabricate micro-through holes in 30 micron thick copper sheets. Circular holes in various micro-sizes were produced by a micro-EDM machine and with tungsten electrodes. Scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDX) were used to identify the influence of electric sparks on the quality of the fabricated features by careful study of resulted cavitation, adhesion of debris, and re-solidification of molten materials, etc. Such analyses allow the generalization of the relevant fabrication mechanisms. In addition, measurements of overcut of the holes facilitate a working model to be developed for predicting the overcut as a function of process parameters including the discharge capacitance and the working voltage of the circuitry. Results of this study enable the derivation of proper settings for fabricating holes of good quality and permit the precision fabrication of the range of micro-throughholes.