Tenting vias completely removes bottom soldermask??

[Anonymous]

As title.

Wanted to tent vias, followed advice as stated here (Change mask limit to just over via drill size)

After doing this it just completely removes the bottom layer solder mask.

Tenting works perfectly on top layer however.

What on earth could be causing this? Im completely brickwalled.

EDIT: The only way I can make eagle generate the bottom solder mask is by over sizing one via so it doesn't get masked.
This will produce a solder mask but leaves me with one exposed via which I don't want=/.
Hopefully this helps, What am I missing?

[jorge_garcia]

Hi @Anonymous ,

I hope you're doing well. Where are you seeing this in the 3D PCB? In the Gerbers? Let me know exactly where you are seeing the soldermask disappear.

It's a known issue that the 3D PCB doesn't show the soldermask correctly, so that wouldn't concern me as much. However if the gerbers are showing this incorrectly then that is a very big problem and I need some files to diagnose the issue.

Let me know if there's anything else I can do for you.

Best Regards,

[Anonymous]

Hi mate thanks for the swift reply. Ill quickly add that Im still rather new to this, Im also using mm as my measures. Eagle Version 9.6.2.

This shows when I add it to PCB manufacturers gerber viewers. JLC and PCBway both show no solder mask.

Also the "soldermask_bottom.gbr" file size is smaller when the mask vanishes. So this makes me think its not a viewer error. But its only by about 40kb so maybe not? 

Using the viewer in eagle as expected shows nothing but white, in the viewers mentioned above they show full copper exposed bottom.

Drill size is 0.35 and I have tried limit set to 0.35 and 0.351 (Here I was trying exact limit and just over limit value)

Can you can guide me to some better viewers? or some way to confirm the layer?

If you need anymore info let me know.

thanks.

[Anonymous]

EDITED:
I originally wrote something else here but still not conclusive. (So now this is pretty much a useless post)

JLC has a second viewer that makes it appear as there is a green mask, but when I change colours it doesn't change with the top.. so just another weird viewer.

I just need to be guided to something better to confirm the layer.

[Anonymous]

So I sent the files to the factory to confirm things.

The layer is missing.
It only generates a bottom mask layer if I have an exposed via.

So this is a software problem and not a viewer problem.

How do I cover my vias without losing bottom solder mask?
The only thing coming through to the bottom layer is three vias.

[one-of-the-robs]

What else do you have on the board? Is that via the only thing that would have exposed copper on the bottom if not tented? If so, the bottom layer mask Gerber ends up completely empty, and therefore won't be generated. The correct interpretation of this, given that solder mask Gerbers are always negatives, would be to put the mask over the whole of the bottom. If the factory do otherwise then it's their error.

You could try sending a header-only Gerber but I'm not sure their systems wouldn't barf on that.