I am designing a very dense PCB containing a 0.4mm pitch QFN chip. In parts it is proving very difficult to fan out. It is made all the more difficult by the huge thermal pad that all QFNs have for some reason.

It is reasonable to place tiny vias 0.45mm OD, 0.2mm ID between the land pads and the thermal pad, like this?
![enter image description here](https://i.stack.imgur.com/aYFIY.png)

I can't think of a good reason why not: they're covered in solder resist, and the sizes and clearances are within spec for our PCB shop. But I don't think I've ever seen anyone do this before.

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I just wanted to add some photos for people interested in these small vias. Here's two from a board we had made recently. Some of the drills are bang on, and some are slightly off.![0.2mm via holes](https://i.stack.imgur.com/Ghmg4.jpg)