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Solder Mask Expansion, make all vias tented?

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  • Solder Mask Expansion, make all vias tented?

    Hello robertferanec ,

    I am concerned with solder mask expansion on Vias and SMD pads. I understand that SMD pads should have some mask expansion to make better solder contact to BGA pads. But, vias dont need anything soldered onto. So, tenting all vias with no expansion makes sense and Ive seen you use tented for top and bottom for TH vias. However, some TH vias like in the RAM location and micro vias have -10mm expansion. And buried vias like at the T topology breakout, the vias solder mask expansion is specified from the rules. Why not make all vias tented with solder mask expansion set at 0 in the rules? Why are they different?

    TH vias under RAM with -10mm solder expanison mask:



    Mciro Vias with -10mm solder expanison mask:

    Click image for larger version

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    Buried vias L3 - L10, solder mask expansion defined from rules:

    Click image for larger version

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  • #2
    There are two ways how you can tent VIAs or pads ... you can check the checkbox or you can specify negative expansion value bigger enough to cover the whole VIA / PAD. The result is same, just the approach is different. You can use either of the ways.

    PS: I am not 100% sure, but the negative expansion value may come from very old Altium / Protel. I am not sure if there was tenting checkbox.

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