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Altium Designer Slots

Checkout the new Update of FAB 3000! This video demonstrates how to create a Rout for a PCB.

MacroFab’s PCB Assembly supports plated and non-plated cut outs, slots and routes. Last time we touched this subject was in the article Plated Slots: Stop Fitting Square Pegs in Round Holes where we explained why a PCB designer should use plated slots instead of large drills for connectors. In this article, I will show a couple examples of how to draw plated and non-plated cut outs and slots so we can build your PCB according to spec.

  • Drill slots are officially supported. Most design tools can generate a drill slot by use of a built-in command on the footprint or board layout editor. These slots are represented on your Drill file, rather than an outline. Note that limitations apply to the use of drill slots.
  • Drill slots are used when you want to drill straight slots in the board. This command is accessed from the CAMtastic Editor by choosing the Place » Drill » Drill Slot (G85) command from the main menus. First, ensure that the layer you wish to place a drill slot on, is the active layer.
  • I'm trying to create a footprint for the ACS770 current sensor in Altium Designer (17.1), which has a quitte irregular shaped pad: ('round' pad shape with slot hole, and then a small cutoff in the middle).
  • MacroFab’s PCB Assembly supports plated and non-plated cut outs, slots and routes. Last time we touched this subject was in the article Plated Slots: Stop Fitting Square Pegs in Round Holes where we explained why a PCB designer should use plated slots instead of large drills for connectors.

The Border Gerber File

MacroFab looks for cut outs and slots in the .BOR or border gerber file. In the EDA Tool Eagle this is generated from the Dimension layer 20. Other EDA Tools will call this the PCB border. If you are uploading an ODB++ package you will have to make sure the cut outs are drawn on with your border tool. You can check after uploading to MacroFab by reviewing the Border Layer in the PCB viewer. DRC rules for cut outs and slots can be found on our Assembly Specification Page.

MacroWatch Example PCB. Checking if the cutouts exist in the PCB viewer.

Make sure the width of the lines is at least 1 mil or larger. The board is milled/cut to the middle of the line, so thickness of the line does not impact the result. Making the thickness of the lines a non zero number will reduce problems down the road with external gerber viewers.

Drawing Cut Outs and Slots

I used Eagle as my example EDA Tool but others should follow suit to get the desired outcome. I drew the cut outs on the dimension layer for Eagle which is Layer 20. The red areas are Copper. The example shows three different kinds of cut outs or routes; external cut out, internal cut out, and internal plated cut out.

Example Board with three different types of cut outs or routes.

Close up of the USB connector which uses plated cut outs. The cut outs are drawn over the copper pads.

When uploaded to MacroFab, the cut outs can be seen in the PCB view under the Border Outline layer.

Non Plated or Plated Cut Outs?

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If you draw your cut outs over copper it will be assumed to be a plated cut out. This is similar to a drill placed in the center of a copper pad for a via. For non plated, pull the copper back at least the recommended distance from copper to board edge DRC. That is all you need to do to denote the difference in your design files.

How the PCB will be milled

When the cut outs are machined out of the FR-4 material (what PCBs are made out of) the PCB fab uses a round bit similar to a CNC machine. Thus inside corners of 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 MacroFab is 0.5mm. This is because the smallest tool used for routing out boards is 1.0mm in diameter.

Below is what the above design will look like after the PCB is made. The inside corners are rounded and the edge of the PCB is cut to the middle of the border line.

What about external exposed plated cut outs?

Ah! Castellated Edges are an example of external plated cutouts. These are used on breakout boards and similar module style boards. We will be cover these in another article.

Recap

  • Border gerber file should include all routes and cut outs
  • Border lines will be cut to the middle
    • Width does not matter
    • Kerf of the bit will be in the waste area of the route or cut out
  • Inside edges will be rounded due to router bit
  • Route will be plated if through copper planes

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Design Rule Setup

Downloadable Files

Kind customers have provided loadable DRC rule and Stackup files for our 2 and 4 layer services.

Note, these files are not exhaustively validated or guaranteed by OSHPark, and may contain errors. Use your judgment and always verify your designs meet our service specs to prevent design defects that could affect your boards. If you have corrections or find errors, please email support.

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known issues: Current minimum 2 layer specs are 10 mil drill hits, with 5 mil annular rings. The RUL file currently shows the older 13mil drill and 6mil ring

Generating Manufacturing Files

For accessing the various menus and output screens, see Altium’s Gerber Setup

Disabling “ Mechanical Layers to Add to All Gerber Plots”

Altium tools have the option Mechanical Layers to Add to All Gerber Plots, which must have all layers unchecked. Many footprints contain mechanical “courtyard” or “pick and place” data on these layers. When these footprints are added to copper layers, it can create gerbers that will be fabricated with shorts. See Altium’s Gerber Setup for information on how to access this setting.

Internal Plane Polarity

We recommend submitting planes with a Positive polarity. See our Positive vs Negative Gerbers page for additional information.

Board Outline

We need a watertight board outline on its own layer with no extra text or measurements. This tells us where the fab should mill the edges of the board. This layer can also contain board cutouts.

For best results, place the outline by itself on the Keep Out, or on a Mechanical Layer (normally 1 or 2). This will generate the outline on .GKO or a .GM<number> file.

Drills

Drill files should work without issues for most export options. If the drill files do not appear correct, check out our Drill File CAM configuration page for settings that we know will work correctly.

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Slots

Altium’s native Slot callout is supported. See our [slots][slots] guide for limitations and DRC requirements of slots.

Common Issues

Missing Drill File

Altium keeps the drill data in the project-name.TXT file. Make sure any uploaded zip files include this file.

Drill file not being read correctly

Try exporting the drill file with the INCH units. Some format issues in METRIC are more difficult to reliably correct.

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Internal Layer names

If you’re using a 4 layer stackup with both “power” and “signal” internal layers, Altium will generate the internal layers as GP1 and G1. Unfortunately, this makes it impossible for us to determine the correct layer order, since multiple layers identify themselves as “Internal Layer 1”.

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To correct this, simply rename the layers using the G2L and G3L extensions. The G2L will be near the Top Copper Layer, and G3L will be near the bottom layer.