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Plated and Non-Plated Holes

TL;DR

About this article

To realize the drills on your PCB as close to your CAD data as possible, we must adapt them for the manufacturing process. This includes the adjustment of diameters and - in some cases - also their removal.

This article explains how we process your data. It serves to prevent common questions and misunderstandings and will help you to create a robust PCB design.

Final hole diameter

Please note that we interpret any drill diameters in your CAD data as final hole diameters (endsize). The manufacturing including selection of the appropriate tool diameter is our job. You don't have to worry about that.

Adjusting to available tools

We cannot manufacture every diameter, as the number of available tools is finite.

Our tools have a graduation of 0.05 mm for diameters < 2.0 mm (1.95 mm, 1.90 mm, 1.85 mm...) - for larger diameters, a graduation of 0.1 mm (2.10 mm, 2.20 mm, ...).

For the preparation of the production data, we select for each hole the tool diameter that is closest to the desired hole diameter.

Since our largest tool diameter is 5.8 mm, we automatically convert larger drills (without adjusting the diameter) into inner millings. The quality of the resulting hole is identical.

Removing overlapping and very close drills

In order to avoid drilling fractures during the manufacturing process, all drill holes must maintain a minimum distance of at least 0.25 mm (0.001 in).

The minimum distance here refers to the tool diameter! This can lead to a situation where drills in your drawing (endsize) meet the minimum distance but fall short of it after we select a larger tool diameter.

AISLER_Min_Drill_Distances

Important: Holes that do not comply with the minimum distance must be removed by us and will no longer be displayed by the BoardInspector. (We are currently working on marking such changes more clearly visible.)

Compensation

Here we must distinguish between two different types of (circular) holes: Plated through holes (PTH) and non-plated through holes (NPTH).

Copper plating always reduces the effective diameter of a drill hole. Therefore, it is necessary to choose a larger tool diameter for PTHs. NPTHs also experience an - albeit smaller - increase in diameter to account for tool wear.

tool diameter = final hole diameter + compensation

compensations:

Copper Cropping

To prevent NPTHs from being unintentionally plated through, no copper must be present within the hole and/or in the immediate vicinity. Even small copper fragments in the copper layers can lead to an accumulation of copper in the hole due to the production process.

To avoid unintentional through-hole plating, we remove all copper from the copper layers that are within the drilling circle and a distance of 0.25 mm around the drill hole.

So please make sure that traces, pads or other copper structures keep a minimum distance of 0.25 mm to NPTHs.

AISLER_Copper_Cropping_NPTHS