New part pads connecting with ground fill

kerrykool · April 17, 2021, 12:08am

Hey everyone, I’ve done a bunch of digging and no luck on finding a solution for this.

I made a custom part (SK6812 Mini-E LED) that I customized from LED strips I found here. After a lot of trial and error in Inkscape, I got a working part. However, after setting ground fill for my PCB using this part, it fills two of the upper pads in the process and leaves the bottom two unfill (like normal). I spent a couple hours reviewing my files and I don’t see any thing wrong that is obvious.

The only thing I found searching the internet, is something about matrix transformations, except I never used any of those, at least not intentionally. I attached the file. Thanks for any help!

SK6812 Mini-E RGB LED .fzpz (11.6 KB)

vanepp · April 17, 2021, 3:17am

I ran your part through FritzingCheckPart.py and it has a number of complaints.

“This is a through hole part as both copper0 and copper1 views are present.
If you wanted a smd part remove the copper0 definition from line 47”

except this is a SMD part and thus copper0 should not be present.

"Warning 14: File
‘part.SK6812 Mini-E New_c1bf5d38d530ff2aaa36d248bd23d316_1.fzp.bak’
At line 104

terminalId missing in schematicView (likely an error)"

"Error 18: File
‘part.SK6812 Mini-E New_c1bf5d38d530ff2aaa36d248bd23d316_1.fzp.bak’

Connector connector0terminal is in the fzp file but not the svg file. (typo?)

svg svg.schematic.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_schematic.svg.bak

Error 18: File
‘part.SK6812 Mini-E New_c1bf5d38d530ff2aaa36d248bd23d316_1.fzp.bak’

Connector connector2terminal is in the fzp file but not the svg file. (typo?)

svg svg.schematic.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_schematic.svg.bak"

Which causes the red circles here in schematic. If the terminalId doesn’t exist Fritzing uses the center of the pin (which in this case is incorrect!) It appears pin1 has a terminalId as it is correct.

As well the alignment to the grid is off by a bit.

"Warning 19: File
‘svg.breadboard.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_breadboard.svg.bak’
At line 2

Height 15.507933 is defined in px
in or mm is a better option (px can cause scaling problems!)

Warning 19: File
‘svg.breadboard.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_breadboard.svg.bak’
At line 2

Width 23.5 is defined in px
in or mm is a better option (px can cause scaling problems!)"

As the message says, it is better to us in or mm as the units, px will cause Fritzing to guess between 72dpi, 90dpi or 96dpi and it often gets it wrong and the part’ scale is incorrect. That may or may not be happening here. Same is true in pcb

"Warning 19: File
‘svg.pcb.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_pcb.svg.bak’
At line 3

Height 13.815009 is defined in px
in or mm is a better option (px can cause scaling problems!)

Warning 19: File
‘svg.pcb.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_pcb.svg.bak’
At line 3

Width 31.195753 is defined in px
in or mm is a better option (px can cause scaling problems!)"

"Error 74: File
‘svg.pcb.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_pcb.svg.bak’
At line 43

Connector connector3pin has no radius no hole will be generated

Error 74: File
‘svg.pcb.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_pcb.svg.bak’
At line 44

Connector connector1pin has no radius no hole will be generated

Error 74: File
‘svg.pcb.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_pcb.svg.bak’
At line 45

Connector connector0pin has no radius no hole will be generated

Error 74: File
‘svg.pcb.SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_pcb.svg.bak’
At line 46

Connector connector2pin has no radius no hole will be generated"

These 4 are complaining that the pads don’t have holes. Because this is a SMD part, they shouldn’t have holes, but Fritzing thinks this is a throuh hole part and will have put pads on both sides of the board. This may be what is confusing ground fill (or you may have hit a ground fill bug assuming you are running 0.9.6.) Here I dragged a couple of .1in headers in to the sketch and attached them on the top and bottom layers to your part (I shouldn’t be able to attach them on the bottom layer as this should be a SMD part.)

I then exported pcb as gerbers and looked at the gerber files in a gerber viewer (gerbv in this case) which shows some more problems (cause as yet undetermined.)

this is bottom layer, and we see the pads and the thermal pad (which we shouldn’t be) but not the two end pads (which we should be seeing!) It looks much the same when I switch to top copper layer:

again the two end pads are missing. So now we need to go figure out why. So to start I edited the pcb svg in Inkscape

Several things wrong here. The Units (circled in red on the right) need to be set to in or mm. The image (which is selected by Edit->Select all) doesn’t start at 0 0 (cirlced in red at the top) so we need to do a Edit->Resize drawing to selection to correct that (and the viewbox at the same time.) This may be what is causing the pads to not be rendered. At the same time I am going to ungroup the uneeded groups above silk screen to reduce the clutter.

Here the groups have been simplified (I left the tspan group in place because an Inkscape bug changes the font size and it isn’t relevant at the moment.) Note the drawing (and the view box) now origin at 0 0 as it should. Next I am going to ungroup copper0 to delete it. Leaving only silkscreen and copper1 which is the correct configuration for an SMD part.

Now I save the file as plain svg and move on to schematic.

Schematic has Units in inches correctly already. But connector3pin lacks a corresponding connector3terminal (circled in red), connector1pin below it has a connector1terminal (circled in green) so I duplicated connector1terminal, renamed it connector3terminal and moved it down .1in to be on the end of connector3pin as it should be.

Then correct connector2pin (whose terminal is set as connector5terminal)

We see connector3 is now correct, so do the same to connector 0 whose terminal is named connector6. Then turn on the page grid (the grid is set to .1in on major lines, .01in on minor lines) and we see that schematic was mis aligned because the right hand pins are beyond the .1 in grid line.

and thus need to move a bit to the left to align exactly to the grid.

While I’m here I added a stroke-linecap:round to make the end of the lines round instead of square and changed the size and position of the terminal rectangle so it fits exactly on the .1in boundary and in the middle of the circular end cap on the line.

Then regrouped the entire image and set schematic as the group name and saved the file as plain svg. Now on to the fzp file to make sure all is well there. We need to remove copper0 from the entire .fzp file, starting with the layer definition:

<pcbView>
  <layers image="pcb/SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_pcb.svg">
    <layer layerId="silkscreen"/>
    <layer layerId="copper1"/>
    <layer layerId="copper0"/>
  </layers>
</pcbView>

becomes

<pcbView>
  <layers image="pcb/SK6812 Mini-E New_67d918244604ca65118d5cb1d23e9181_2_pcb.svg">
    <layer layerId="silkscreen"/>
    <layer layerId="copper1"/>
  </layers>
</pcbView>

Then each connector definition needs copper0 removed

<pcbView>
      <p layer="copper1" svgId="connector0pin"/>
      <p layer="copper0" svgId="connector0pin"/>
    </pcbView>

becomes

<pcbView>
      <p layer="copper1" svgId="connector0pin"/>
    </pcbView>
  </views>

Now run the svgs through FritzingCheckPart.py to clean up and check for errors. Rezipped it to a new part and test

Schematic is now fine. The lines terminate correctly at the end of the pins, and the pins align to the .1in grid. Now on to pcb.

and pcb looks ok. It will only connect on the top layer (as the part is SMD.) Now to see if the gerber is happier.

No, still missing two of the pads. So back to the pcb svg to see why.

However copper bottom now shows no sign of the pads as it should

Well copper1 has a transform so lets start by trying to remove that.

to do so ungroup the entire svg (which usually removes transforms) and see what happens. It did indeed remove the transform, so lets see if that fixed the part. No cigar, still broken. That leaves us with something wrong about the path for the top two pads. So try duplicating and moving the bottom pads. Ungroup again because copying with groups will cause transforms. And success. There is something wrong either in Fritzing gerber processing (because pcb view is rendering the pads correctly) or the two paths. Duplicating and moving the bottom two pads to replace the top two pads makes things work.

We now have the missing pads in the gerber output. Here is the part that generated the above.

SK6812 Mini-E RGB LED-fixed.fzpz (12.0 KB)

Note you need to check the pads on pcb in this part to make sure they are the correct size because I changed px to in in Inkscape and the scale may be wrong depending on what dpi the original svg was in.

edit: Try this part with the ground fill and see if that cures the issue. If it doesn’t you may have hit a 0.9.6 bug as I remember someone else reporting a ground fill issue in 0.9.6 lately.

Peter

kerrykool · April 17, 2021, 8:49pm

Dang Peter! I was only expecting a little assistance and you hand over all the work completed!

This was my first attempt to make a part (totally not obvious, I know) so I was working through it the best I could. Like I mentioned, I did take this from a part from a previously built item I found here so some of those errors may have existed. The SMD portion (copper1) I completely missed because I was referencing to directions I found about other components that needed the extra grouping.

I tested the fixed part and it works! However I did find another bug trying to import the fixed part. I kept running into “This part already exists…” attempting to import it. The only work around is to delete the existing part, save the changes to the parts, exit the program completely and restart. Then you can import the new part under the same name. Would be good to see an overwrite option in the future.

One last question, is that python program/script (FritzingCheckPart.py) included with Fritzing? This is my first time designing a part and PCB and modifying SVG via XML, so any extras I can find will help a lot.

kerrykool · April 17, 2021, 9:15pm

Well, doing my due diligence, I checked out the gerber files and the center square is supposed to be a through ‘hole’, but it’s not showing up like one. I’ll see what I can do about making it one and uploading the finished part.

vanepp · April 17, 2021, 9:34pm

That really is a bug. Fritzing thinks it has deleted the part entirely but hasn’t until you shut down and restart. The good news is that the bug that was causing the path to not render in gerber has been found and fixed (but probably not til the 0.9.7 release.) Does ground fill work correctly with the new part? There is a bug report open on ground fill, but it may have just been the part config that was the issue.

That is harder to do. Fritzing doesn’t really support mixed through hole and SMD parts. It wants one or the other. Usually I put the places for the vias on silkscreen and tell the user they need to manually drag a via in to the sketch and add a pad on the bottom of the board to achieve this.

Peter

kerrykool · April 17, 2021, 10:41pm

Ground fill works great now, much appreciated! Definitely related to the part config.

I see what you mean about one or the other. I’m looking at other parts that have those through holes and testing some other things. I’ll report back if I have any success.

vanepp · April 17, 2021, 11:02pm

You can do it, but then you need to put a circle in all the pads so that there is a through hole connection as well . If copper1 and copper0 are both present Fritzing assumes there is a through hole connection and will try and connect on either layer which usually doesn’t work on SMD parts and won’t work if there isn’t a circle to cause a hole to be created.

Peter