Yes, that’s the change I was suggesting, it may have been unclear.
ie The fix for this is to change the source, but in a trivial manner to change the default setting, to match the real-world PCB FAB suggested values, not this larger bad choice.
Users should not have to change this, every time, it should be a real-world-valid number to start with.
At the moment, I am leaning towards the setting just being zero.
I disagree here, as the different fab houses have different specifications for their board fabrication. In what way does it make sense that this specific setting should not need to be changed when a different fabricator is chosen?
i think @PCB_Wiz meant that if you always use the same fab you should be able to set your own default values.
KiCad could also use default values that are closer to typical fabs.
Which you can. Just setup a user template. You can setup these things in it.
True, but having the default mask clearance = default copper clearance is a bad choice, because that requires your fab to have infinite precision.
Choosing default mask clearance = 1/2 default copper clearance seems reasonable, allowing offsets of up to 1/2 default copper clearance.
The suggestion by oshpark of default mask clearance = 1/4 kicad default copper clearance is also reasonable, by any standards. This would allow offsets of up to 3/4 kicad default copper clearance, since covering the pad is a less serious error than exposing unwanted copper.
@Jan-Ake_Larsson How does the Fab know that your design is requesting a SMD or NSMD defined pad for each and every part? One is positive clearance and the other is negative clearance.
The purple board house fabricated 2 board designs with seemingly great precision, with many different design factors in place with the global setting set to zero.
A common request on the forum is information on Via stitching for thermal reasons. Using extra board copper in a zone as a thermal element for a Footprint requires the SMD defined pad on one side of the board.
Then there is the issue where a MSSOP part (I THINK), was technically outside the clearances of the purple board fab and anything less than than zero probably would have have provided solder mask between the pins; I will have to double check. Anyways, it is a STUPID SMALL part, with STUPID SMALL pins and spacing and I can not (at the moment) imagine that anything other that zero/zero for SolderMask clearance would have resulted in a hand solderable board.
AFAIK, this is a KiCad library approved V5 Footprint: “SO:MSPO-8_3x3mm_P0.65mm”.
Here it is on the board with the above mentioned 0.002" SolderMask clearance:
As can be seen, the SolderMask clearance interferes/crosses-over to the adjacent pads.
This is with the SolderMask clearance set to zero:
This is an incredibly small part and pin spacing.
The purple board fab house had 3 boards with this Footprint fabbed and sent to me. I really did not know what to expect with the overlapping pad clearances as part of the DRC for their specifications. The design was sent to out to them with zero clearance spacing and the boards came back with an extremely thin SolderMask layer between the pins.
At the moment, I believe this part will be hand solderable onto the KiCad library Footprint.
I have no idea what happens with 2 mill clearance setting when sent out to fab.
Because they can see it in the gerbers?
Look, I am only asking for a sensible default. If you have special components, those need special attention anyway.
I had a look at that component, see below. The inner red rectangles are the pads. The purple rectangles are the mask cutouts. The outer red rounded rectangle is the copper clearance.
I don’t see the problem with 2 mil mask clearance.
You do realize that the pads are copper? And, that the pads copper clearance interferes with the other pads?
There is nothing stopping you from creating your own design and spending your own time and money and sending it out a board file to a fab house with those settings to document what you actually get back.
Telling “me” that I’m wrong, when I have already spent my time and money to have a quality board already fabbed and “in-hand” is sorta pointless.
Yes I do realize the pads are copper. There is no need to be rude.
Look carefully. One pad’s copper clearance does not interfere with the other pads. It reaches the pads, yes, but there is no overlap.
There is overlap of the mask cutout of one pad with the adjacent pads’ copper clearance. But that is not an issue. The mask cutout is not copper.
I would expect your board works fine, since you use mask cutouts that fit the pads. The fab did not offset the mask too much.
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