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Hole size for through hole compoent

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jnbrown View Drop Down
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    Posted: 16 Dec 2021 at 11:58am
I am using a power module that has 1.02mm diameter round pins.
In Footprint Expert I specified a through hole header with 1.02mm round pins.
The resulting hole size is 1.20mm.
I found this IPC information:

Minimum Hole Size = Maximum Lead Diameter + 0.20mm (for Level B of IPC-2222)

Being the manufacturer of the power module does not specify a tolerance I figure I should at least add a few mils to the diameter. Also through hole drill usually has a tolerance of +/- 3 mils. So going by IPC recommendation I am figuring 1.02mm + 0.127mm for tolerances + 0.2mm = 1.347mm.

Does this make sense?

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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 16 Dec 2021 at 12:07pm
Makes perfect sense, but in every through-hole calculator in V2021 Footprint Expert the user must enter the minimum and maximum lead diameter. 

i.e.: the tolerance is built into the calculator. 

A maximum lead diameter of 1.02 should produce a 1.22 hole, but it totally depends on your Hole Size Round-off is in Tools > Options > Terminals > Through-hole > Hole Size Round-off > 0.05 (will round-off to the nearest 0.05 mm value). 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jnbrown Quote  Post ReplyReply Direct Link To This Post Posted: 16 Dec 2021 at 12:35pm
I did not have the Min/Max button selected.
Now I entered 1.02 +/- 0.05mm for the lead size and I am getting 1.25mm for the hole size.
Where is the +/-3 mil drilled hole tolerance taken into account in the calculator?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 16 Dec 2021 at 1:27pm
In Tools > Options > Terminals > Through-hole 

There is a setting for "Minimum Annular Ring"

In the 60-year history of PCB design, the PCB designer should know what the minimum annular ring needs to be to compensate for the +/- 3 mil drill hole tolerance. 

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jnbrown Quote  Post ReplyReply Direct Link To This Post Posted: 16 Dec 2021 at 1:49pm
I am not asking about pad size or annular ring.
I am asking about drilled hole size.
The IPC recommendation says Minimum hole size.

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