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Re: Kicad libraries for pcbnew
> The size of the soldermask (and the pastemask ?) seems to be hardcoded tobe 6mils larger than the pad on all sides, and there is no way of specifying the masksize(s) in the component libs.
It is not hardcoded, it's a board attribute set in the track/via dimension dialog IIRC.
And BTW, the pastemask is exactly big as the pad (if you think about it, itmake no sense to apply solder paste over something which is not copper... it would be a mess in the oven, trust me:D)
> There are only two ways of changing this in kicad: Either lower the built-in default from 6mils to 3mils (4mils is too large), or enhance the pcbnewcomponent libraries with two extra values: The masksize (relative to the pad size) in X and Y.
The 'right' way to do it is with padstack definitions :P for now you just can change the global value.
> When doing a PCB Design Rules Check on my *QFP sample board, it doesn't complain about the overlapping masks, so are overlapping masks really a problem, or can they be ignored ?
Overlapping masks COULD be a problem but there are legitimate use for them.Expecially when mechanical/thermal issues are involved.
As for the recommended clearance you should ask to you manufacturer... homePCB simply do not have solder masks, and the process involved gives different resolutions; just like tracks can be manufactured 8/6 or 6/4 (usually, depending on the budget), solder mask can be silked over (with a 0.2mm resolution) or photo engraved (usually giving the same resolution of copper planes).
Also one of our fabs simply ask for 0 clearance and postprocess the solder gerbers in house optimizing them for their process.
SO (as usual in PCB design) the 'correct' answer is: ask your board fab facility:D