5 Tips for Specifying PCB Hole Size Tolerance in Pads and Vias

One of the crucial yet often overlooked aspects of PCB design are the holes through which components are mounted. Specifying the tolerance of hole dimensions in PCB fabrication ensures proper fit of plated-through-hole (PTH) components. Just as important, those dimensions must be clearly communicated to the fabricator so that the boards are properly made.

Now, Altium ^® PCB design software allows you to add hole tolerance attributes for your pads and vias that will be communicated to the fabricator by inclusion in the drill holes table. Here are five tips to help you quickly specify hole sizes in your next PCB hole tolerance design:

1. Set and Specify Hole Tolerance Attributes for Specific Pads and Vias

You can quickly set the pad/via tolerances using the properties of each.
Right-click on the pad or via and select Properties. In the Pad Properties dialog (Figure 1), PCB hole tolerance can be edited under the Hole Information section.

• In the Via Properties dialog, hole tolerance can be edited using Tolerance, in the top left-hand corner of the dialog (Figure 2).

2. Creating Hole Tolerance Attributes for a Pad or Via Template

You can also specify hole tolerances using a pad or via template.

• Right-click in the Pad Via panel and select Add Via Template or Add Pad Template. Hole tolerance can be set under the Hole Information section.

3. Setting Hole Tolerance Attributes for Multiple Pads or Vias at Once

Conveniently, you can set the hole tolerance for multiple pads or vias at the same time (Figure 3, Figure 4).

• Open the PCB Inspector panel. Select the pads or vias on the Printed Board that you wish to set and enter the necessary hole tolerance values in the panel, in the right-hand column under Object Specific.

• Hole tolerance columns can also be added to and edited from the PCB panel, using the Hole Size Editor. Right-click under the Unique Holes header and select Columns » Hole Tolerance (+) and Hole Tolerance (-). By clicking in the hole tolerance columns, the tolerance attributes can be changed.

4. Adding Hole Tolerance to Via Stitching/Via Shielding

Hole tolerances can be added for multiple stitching vias to save time (Figure 5).

• Go to Tools » Via Stitching/Shielding » Add Stitching to Net. Hole tolerance information can be added under Tolerance in the Via Style section.

5. Displaying Hole Tolerance in the Drill Table

You can view the tolerances in the drill size table in two ways: one or two columns to display tolerance attributes.

• From the Drill Table Properties dialog, click Add Column. To view all tolerances attributes in one column, select Hole Tolerance. This column will display the minimum and maximum set attributes together. Alternatively, you can choose to show the minimum and maximum set hole tolerance attributes in separate columns. For the latter option, select Hole Tolerance (+) and Hole Tolerance (-). You can of course also choose to display only the minimum or maximum set hole tolerance independently.

You can also choose to group objects by their hole tolerance. From the Drill Symbols dialog (click Configure Drill Symbols in the Drill Table dialog), click Grouping and select Hole Tolerance.

Note that when adding hole tolerance information to pads and vias, unless all pads or vias grouped under the Count column have the same hole tolerance attributes, hole tolerance values will be displayed as an * (asterisk).

IMPORTANT: After adding columns to PCB drill size table, you must click OK to exit the Drill Table dialog or your changes will not be saved.

Ensure Your Board is Manufactured Properly with Altium

Ensuring that you properly specify hole tolerance is critical for your PTH to properly mount to your PCB manufacturer. Altium Designer^® has made the documentation of your hole size tolerances simple, with your tolerance specifications easily added to the drill table, so that they can be clearly communicated to your fabricator.

Interested in learning more about the PCB hole size tolerance capabilities in Altium? Download the free white paper 5 Tips for Specifying PCB Hole Size Tolerance today.