Unexpected export of vias only on inner layer 4


Today I exported a 6 layer project to gerber files. Everything looks fine so far, but all vias leave a circle on inner layer 4. I attached some pictures to make that clear. I am a Kicad noob so maybe its something I made wrong, but i dont understand its only happening on inner layer 4.

thanks in adavance for your advice.

How does it look in pcbnew if you turn vias on?

here is a screenshot with vias turned on, inner layer 4

I thought maybe something went wrong during import of the originakl gerber project. But even when i completely remove the via and place a new one, the behaviour is the same.

and here is a scrrenshot with vias turned off, inner layer 3

here is a screenshot with vias turned on, inner layer 3

This far everything is expected. Turning vias on/off in pcbnew is visual only, it doesn’t affect the generated gerbers. The vias are there in every layer.

KiCad doesn’t have “padstacks”, i.e. different annular rings in different layers. For a via every layer has the copper ring. If a specific via is connected to a copper zone (they are in the same net), there’s no hole in the gerber, it’s all copper. If it’s not connected, there’s the copper circle for the annular ring where the via is and a hole around it in the gerber copper because the annular ring copper and the zone must not touch.

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That doesn’t help to understand your problem. Normal vias go through the board and are in every level. There’s problem only if some level in gerber files doesn’t have have copper where the via is.

my actual guess ist, that kicad imported layer 4 wrong, because in the original gerber files layer 4 is a negative layer. would that make sense?

Gerber import of kicad is quite bad. So yes i would suspect that it might have been imported wrong (after all the layer looks very strange and the small lines around the pads could be the result of a thermal spokes algorithm.)

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