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Based on the VSK-S25 datasheet which states the holes to have a diameter of 1.5 mm,

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I used the following values in EAGLE

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When the PCB is made, it turns out that the pins of VSK-S25 are too large for the pads. Should we have used 0.059 inches for Drill rather than Diameter?

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3 Answers 3

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Drill is the size of the clearance hole, diameter is the outer diameter of the copper pad. The difference between these numbers determines the width of the annular ring (donut).

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Yes, with most (not all) PCB manufacturers you specify the "drill" diameter and they will use a slightly different size of actual tool to ensure the finished, plated hole diameter is close to what you specified.

In your case, you specified 0.8mm, which is obviously way too small. The recommended hole diameter of 1.5mm is a bit loose on the actual 1.0mm nominal pin diameter.

You should make the pad quite a bit bigger than the hole size for a relatively heavy component and large pin diameter. Maybe 2.1mm or 2.2mm, which will give more than 10 mils annular ring. If the board was one-sided you'd use a bigger pad size again for the pads that are far enough apart to allow it. You could also use a slightly small hole size- perhaps 1.3mm.

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Sort of if you know the pin size is 1.5mm do you think you can count on drilling a slightly less than 1.5mm (1.4986mm) hole and have it work. Granted your fab house will just pick a drill size close to that one. That 1.5mm hole is going to be plated, the thickness of which will bring down the hole size even further. Then there's tolerances, first off the drill size itself will have a tolerance, and the bit may wander a little from absolute center. So now you find yourself needing some slack so all 6 of those holes always line up.

I'm sure the pins themselves and their spacing also have a tolerance in the datasheet.

All that adds up to needing hole sizes that are slightly larger than your ideal pin sizes. I've gotten lazy and like to specify to my fab house that all my holes sizes are finished sizes after plating which makes it a little easier if your fab house accepts that.

You can come up with your own actual drill size by considering all these requirements, and you can also consult the IPC standards for more advice.

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  • \$\begingroup\$ All excellent points but in this case the nominal pin diameter is 1.0 mm; the 1.5 mm is the manufacturer's suggested footprint hole size. \$\endgroup\$ Jun 10, 2017 at 7:11

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