Slots and Cutouts
Slots and Cutouts
At MADPCB, we support plated and non-plated slots and cutouts PCB manufacturing and their thru-hole assembly. We see a lot of different slot and cutout footprints and part types. A majority of thru-hole part footprints are designed with circular holes to fit circular or square leads, like USB 2.0 connector. This configuration is ideal for most thru-hole components, but many parts include rectangular or “blade-style leads, which do not fit well in circular or square holes; instead, it is best to use a plated slot footprint.
How to Define Slot on PCB?
If you want to add slots (/cutouts) in your design, MADPCB prefers Gerber mechanical layer. The safest and clearest way in a Gerber mechanical layer which shows the slots/cutouts and the profile of the PCB. Two possible ways forward:
Use draws and/or flashes with the correct end size of the slot/cut-out.
Draw the slots/cutouts with a 0.50mm line. It has the advantage that at the same time the line helps you to visually check the clearance of any copper to the PCB board edge. Our engineer will take the center of the line as the edge of the slot.
Combine your definition of the slots/cut-outs with the PCB contour (outline) into the Gerber file. This layer should line up with the copper layers, but to be as safe as possible make sure that the copper layer also includes the PCB outline.
Different systems have different names for the mechanical layer (for instance in Eagle it is layer milling -layer46). Provided that you have included milling in your order (see below) our engineers will find the right file.
If there is no mechanical layer, you may have to adapt another layer. If there could be any doubt which is the right file, point to it in a README file.
Avoid defining slots only in a copper layer or in a legend layer, as they are then very easy to overlook or misunderstand. You can indicate large cut-outs in a copper or legend layer, but make sure that there is a clear outline, and put text CUTOUT in the middle.
Some CAD systems allow you to define slots in the drill file. This is also safe and clear. But they must be defined as slots with an X and Y dimension, not as a row of overlapping holes.
Plated or Non-Plated
If slots and cutouts with copper on top and bottom, it’s a plated slots or plated cutouts; or it’s non-pated slots or non-plated cutouts. This is similar to a drill placed in the center of a copper pad of a PTH. For non-plated, pull the copper back at lease the recommended distance from copper to board edge DRC. That is all you need to do to denote the difference in your design files. Give the dimension of the finished slot size. We will make the necessary adjustment for the plating. If you need non-plated slots through copper pads, indicate this clearly in the mechanical layer or in a separate drill file.
How to Mill Slots and Cutouts?
When the cutouts and slots are milled out of the rigid board material (FR4, PTFE, metal core), the PCB fabrication uses a round bit similar to a CNC machine. Thus, inside corners of the cut outs will not be sharp but will have a round edge to them. This is something to watch out for in enclosure designs. The smallest inside corner radius possible at MADPCB is 0.5mm. This is because the smallest tool used for routing out boards is 1.0mm in diameter. The inside corners are rounded and the edge of the PCB is cut to the middle of the border line.