Method, for defined drilling of blind vias in multilayer circuit boards, involves drilling down to layer in front of desired layer, changing to smaller diameter drill, and establishing contact with desired inner layer

摘要

The method involves drilling through an edge frame and metallizing the bores. Test holes are drilled in a sounding pad region (3) to determine the precise depth between the circuit board surface and the inner layer (IL). Holes proper are then automatically drilled at this depth, firstly only to the last-metallized inner layer in front of the inner layer that is actually to be reached. The drill tool is then changed to a bit of smaller diameter, to establish contact with the desired inner layer.