Capillary drilling uses acid electrolyte. The electrodes are fine glass tubes with a noble metal wire (e.g. platinum) passing up the centre of the tube. The tube carries the acid to the work area and the wire carries the electrical power. The process is usually chosen where holes of less than 1.4mm diameter are required through depths exceeding ratios of 10:1.

The process controller monitors acid temperature flow and conductivity and special emphasis is given to acid filtration to prevent debris blocking the bore of the glass tubes.

Like STEM drilling, the resultant metal finish is of high integrity with no recast layer. Feedrates are similar to those of STEMdrilling, generally 1.8mm/min to 2.5 mm/min.

Applications