From CAD to CAM

One of the most critical phases in making a printed circuit board for an application is transferring the board design data to the board manufacturer without errors. Manufacturing a board correctly requires many kinds of different information. Unfortunately, the file formats that CAD programs commonly use for this are not precise enough, and leave room for uncertainties and interpretation.

eurocircuits drill/slot editor
The Drill/Slot Editor has many selection tools.

Introducing the Drill/Slot Editor

To improve this situation board manufacturer Eurocircuits proposes a free online tool suite  where the board designer can check if the interpretation of his/her data is correct. The new Drill/Slot Editor adds even more capabilities to this already extensive tool suite.

Not all holes are created equal

The subject may seem trivial, but when you manufacture PCBs a hole is not just a hole. PCBs tend to have many holes, from vias to mounting holes, and all have different requirements. Strange as it may seem, basic Gerber files do not contain information about holes, making it necessary to supply information about them in another way. This is where for instance Excellon files come into play.

A drill is more than a hole

To emphasize that a hole is more than just a diameter, the people at Eurocircuits refer to them as ‘drills’. A drill has a diameter, an X-Y position and may require plating. A plated drill usually connects to a trace or a copper plane and if it does, there must be enough copper left after drilling to make this possible. Therefore a drill also has a maximum error for its diameter and position. That makes at least seven parameters for a single hole (via filling anyone?).

Limited precision

Add to that the limited precision of board data files — a good reason to work on a grid — and that some of the specified drill diameters may not be possible within the desired board class. Also keep in mind that the manufacturer’s tools do not have infinite precision either. It should be clear by now that matching CAD drill data to real-world CAM tools is not as easy as it may seem.