I have a designed board on which all the parts are set manually,
In the downside, I would replace 0805 with 0402, But I do not know if this dimension is no longer too small for manual placement with tweezers.
What's your experience?
0402 devices are NOT marked, while most 0603 and higher are. If you are really tight on room, then 0402s can be manually placed (with tweezers and a microscope) successfully. It's not fun - 0402s are basically "sand" - if you drop one, forget trying to find it, just get another from a marked supply. I don't use them unless absolutely necessary!
I am too old to do neat soldering but it could be done with a magnifying glass and a steady hand. My philosophy is that if you can see it, you can place it...
But if your board is already designed (I mean a finished product) - just go ahead and do it. For a fraction of a second, it will float on the molten solder and then settle on a steady position.
>0402 devices are NOT marked
That's true, but marked is only resistor and resistor not problém measure,
Plus the resistors are so cheap that it is better to drop them than to measure.
Size 0603 I usually use, but the real space saving between 0603 and 0805 is not significant
Up to size 0402 allows for example this