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36 PCB007 MAGAZINE I MAY 2023 What's an Annular Ring? Let's learn about annular rings, because a greater understanding can help ensure that your PCB designs successfully become physical boards. e annular ring is the space between the drill hole and the edge of the pad—a speci- fied minimum gap around the drill hole. Don't get the impression that an annular ring is a sep- arate part. e term is used to describe the portion of the copper pad that remains aer a hole is drilled through the pad. e annular ring of a pad is measured from edge of hole to edge of pad. Annular rings serve a variety of purposes, and improperly sized annular rings can cause serious PCB concerns. In addition to causing shorts, small or nonexistent annular rings can create significant manufacturing delays and board reliability issues. Connecting the Dots by Matt Stevenson, Kevin Beattie, and Karla Thompson, SUNSTONE Figure 1: Magnified graphic illustrating a typical annular ring.