Copper fill clearance

[ilium007]

Hi - I am designing my first board in KiCAD 4.0.7. It is a board for an MCP23017 IC with some headers and an I2C level converter circuit.

I have noticed in the 3D render that with the default copper zone clearance setting of 0.254mm leaves all my 0805 SMD pads with their corner solder masks clipped as shown below.





If I increase the copper fill clearance to 0.508mm it seems too much. Is there a standard for this sort of thing ?

[ovnr]

Re: your first image with 0.254mm clearance: This is fine. The holes are small enough that they won't show up in practice - the solder mask process doesn't have that kind of resolution, at least at the "cheap PCB" level.

I should note that I run with 0.025mm clearance on my own exports - enough for the fabs to get the hint that they shouldn't go nuts (like when you have zero clearance), but they'll increase it to whatever they need for manufacturability reasons. I've never had registration issues where the mask ended up on the pads.

[ilium007]

Re: your first image with 0.254mm clearance: This is fine. The holes are small enough that they won't show up in practice - the solder mask process doesn't have that kind of resolution, at least at the "cheap PCB" level.

I should note that I run with 0.025mm clearance on my own exports - enough for the fabs to get the hint that they shouldn't go nuts (like when you have zero clearance), but they'll increase it to whatever they need for manufacturability reasons. I've never had registration issues where the mask ended up on the pads.

Thanks - I am going to se Osh Park for these first boards.

This is what I get when I drop the clearance to 0.025mm - this looks like I may end up with solder bridging (hand soldering these first boards).

[ovnr]

Bit of a brainfart, sorry. I meant solder mask clearance, not copper fill clearance. That should stay at 0.2-0.25.

[ilium007]

Ok - I'll take a look at solder mask settings. Haven't played with those yet !

[hermit]

The 3D tool is excellent and this may well be a fair representation of what you will get but gerbers are the final word.  Defaults are just starting points.