"A"
"B"
"C",
"D",
"E",
"F",
"G",
"H",
"I",
"J",
"K",
"L",
"M",
"N",
"O",
"P",
"Q",
"R",
"S",
"T",
"U",
"V",
"W",
"X",
"Y",
"Z"
Minimum Annular Ring
The minimum annular ring on a plated thur-hole is the minimum amount of copper (at the narrowest point) between the hole and the edge of the pad after plating of the finished hole. MIL-STD-275E and IPC class 3 calls for a minimum annular ring of 0.05mm (0.002") edge of hole to edge of pad. MIL-STD-275E also calls out .005 inches for via to trace distance.
Minimum Annular Ring; PWB Internal Via
Both diagrams indicate minimum annular ring measured from the outside ring of the pad and to the inside diameter of the plated thru-hole for an external pad [below], or to the center of the plated via for an internal pad [above].
Minimum Annular Ring; PWB External Pad
Minimum Annular Ring applies regardless of the shape of the PCB pad. The next page shows two examples of different pad shapes.
More Printed Wiring Board Terms
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