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3D drill size ?

Lennie

When I measure the finished hole diameter in the 3D the software starts with the finished hole size and then adds the layer thickness to the hole. So for example a 40 mil finished hole with 1 OZ Copper plus plating ends up a 34.8 mil hole.

The value for the drill is the finished hole size , not the starting hole size before plating. Usually the plating process only adds 1.4 . 

Is this just a bug or is there a way to fix this ?

  • excellon1

    Lennie, while I had not used that feature of the 3d if the drill holes are off by that much then for sure that is a bug.

    On the Drill files. The drill file and tool used in the drill file will be the tool size the manufacturer uses. This would be the primary drill size. Plating will give you a finished size. Normally when I do a board I include a tolerance of +1.4, -1.4 mils on the drill ledgend as this will account for a board with 1 oz of plating.

    This would save the manufacturer from having to use over-sized drills and instead just use what's in the actual drill file. When you use a drill on FR4 or similar pcb material the drilled hole will be slightly larger than the actual drill. This is because the material you are drilling into is a weave. From the plating perspective it is kind of splitting hairs on the finished hole size because the plating thickness is so small it kind of does not matter.

  • Lennie
    in reply to excellon1

    Thanks.. It is a bug as you change the thickness of the top layer copper and the hole gets smaller.

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