Through Hole Footprint with no copper on the Bottom Side

Hello,
I made an custom Through Hole Footprint with the aim haveing no copper on the bottom side (actually an via with no copper on the Bottom side).
Now I have this grey surrunding at the botoom side. It looks like there would be no soldermask/resist and also no copper. Is that true? Because actually there should be green solder mask.
Footprint Editor:

Bottom Side in 3d Viewer:

Which settings should I take for this?

My first idea was to deselct B.Mask. of the pad. If I deselect -> B.Mask , solder Mask is covering the hole. Does anybody have an idea? Or is it simply an problem of the 3D viewer?
Deselected Bottom solder mask:
grafik

Are you sure that PCB manufacturer you use can do metallization if no copper at one side?
I have heard that some can, but not sure if all.

2 Likes

Hm, I am not sure if I get you right. But on the bottom side there should be no copper. What do you exactly mean by “metallization”? Because on the bottom layer there is no copper (=no metallization?).
Finally there should actually an Pad with an hole in it.

We assume your PCB is double sided. Vias and PTH are metalized on the inner surface of the hole.
The process of bringing the Cu there is a bit complex. It requires a ring of Cu around the hole on both top and Bottom side of the pcb.
If you delete the ring on at least one side of the PCB, there will be no Cu inside the hole. Maybe this leads to more problems in the process, not shure.
My manufacturer requires an ring of >= 0.15mm with.
Maybe we can help you better, if you explain the aim of your experiment!

Regarding bottom-mask:
If you deselect it, no mask on bottom will be generated at all, thus in 3D even the hole is “covered” by mask.
The manufacturer will probably take care of that, else surplus mask will smear all over the silk when printing.

If the drilled holes have no copper on the inside, this is no problem or better. Another way I tried: I made an smd pad and made an additional hole in it:


grafik

In the footprint editor it looks like exactly what I want. But in the PCB things seem different:

The hole is filled with grey again.

I think this way works. I uploaded it on pcb manufacturing website. Everything looked fine. I think the problem was thad KICAD 3D viewer ignores when in an copper pad an hole is made.