Guard Rings on SOIC-8 Op Amps

Well that is a good idea - essentially sky wire to a pad - using a driven guard (rest of connections not shown):

Thanks! I hate the Sky Wiring but this alternative is actually pretty good. Of course I will make the pad a bit bigger to make the soldering job easier.

TLDR. The point of the vid was to show how to make the DRC distance smaller, and I think most fab houses can do 0.006". Just check with them. So long as the gap between the IC pins is 0.018", it should make it.

Translating/expanding from @Old_Grey’s numbers, with 0.05 inch (center to center) pin spacing, 0.032in wide pin pads, there will be a 0.018in gap between the pads. With a centered 0.006in wide trace, there will be 0.006in gap on each side. Converting to mils, that will be 50, 32, 18, and 6. If you can narrow the pads by 3mil, the 6, 6, 6 can be increased to 7, 7, 7 (or 6, 9, 6).

1 Like

You guys are terrific thanks.

Ok, if I want to thin up the pads a tad, I have no idea how to do that.

Before asking you, I loaded an SOIC-8 IC, selected it an opened the part Editor.

I couldn’t see what to do.

Is there a video example of such an operation?


The vids cover basic svg drawing as well as making parts.

The referenced videos provide the low level how to do it details. That level of manipulation is not included in the existing part editor tool. The summary, is:

  • open the existing part in parts editor
  • save as a new part
  • export the part
  • unpack the exported fzpz file into the separate part definition (fzp) and svg files (unzip)
  • modify the pcb svg to have narrower pins (using what ever tool you want)
  • combine the fzp and svg back into an fzpz (zip)
  • delete the initial saved part from Fritzing
  • import the modified part
  • place the new part from the MINE bin instead of whatever you are using now. (you can use “delete minus” to remove the existing part, while keeping all of the wires that will need to connect to the new part)

At the resolution you need to work with, you will need to be very careful to get accurate position and sizes, or there will not be quite enough room when you are all done. Which might be harder than expected, depending just how precise the coordinate information in the original part was specified. It might be easier to generate the nice regular array of pads you want, then copy/paste it into the copper layer. How hard that is will again depend on just how the existing pcb image was created and saved. There are some tricks to manipulating svg images that I do not know if are in the referenced videos. I am not going to try to cover options for that here. Wait until you get far enough to know what the question is based on what you find in the first several steps. If you want to start down this path.

As a first cut at finding out more about the part, once you get it exported and unpacked, the FritzingCheckPart can be used to see what (obvious) things might cause problems.

The vids show the above method, but the quicker way is to -
FZ edit part
Goto PCB view
Then File/Show in folder
Copy the svg file and edit that drawing
Then back to FZ edit and File/Load image for view, and save.

It saves all that unpacking and file conflicts.
There should be a vid showing the quicker way, but if it doesn’t, my soon to be posted vid will have it.

Here is the vid

Thank you again -

OK I did what you explained. Everything seemed to work perfectly with one detail I cannot seem to understand - I loaded the SVG in “Method Draw SVG Editor” - a Web based editor - and moved the pads as we discussed (Slightly, just enough to yield a bit more clearance, but I can still solder it). Then, saved it with a new name, then saw the new part show up in My Parts! Perfecto so far. But when I pulled the drawing in, the SCALE of the drawing was drastically different. The change I made was there, but for some reason the basic physical dimensions were drastically smaller.

Kind of fun - because the pad squeez worked like a champ, but something happened with the scale. All I did was pull up the svg, move the pad, and file it with a new name. How did the Scale get stomped on?

Maybe this is the attribute of the web based SVG editor?


Here is a zip file, renamed to .fzpz, with a slightly cleanup up version of the sparkfun analogic so08 pcb svg image, adjusted to use 1000 px per inch (1 mil per px). This uses 24 mil pad widths. Also in the zip file are modified versions with 21 and 18 mil pad widths. The forum would not let me upload the individual images. They are too small for it to figure out the dimensions, then the forum does not like zip files either, so renamed it to .fzpz

so08-footprints.fzpz (1.7 KB)

Here is a table of what maximum trace sizes will fit between the pins, based on the pad with and keepout distance. All numbers in mils

Spacing Pad Width Gap Keepout Trace Width
50 24 26 6 14
50 24 26 7 12
50 24 26 8 10
50 24 26 9 8
50 24 26 10 6
50 21 29 6 17
50 21 29 7 15
50 21 29 8 13
50 21 29 9 11
50 21 29 10 9
50 18 32 6 20
50 18 32 7 18
50 18 32 8 16
50 18 32 9 14
50 18 32 10 12

Smaller pads have there own down sides. For starters, to leave room for the trace between pads, the trace connecting to the pad can not be larger than the pad width. Another alternative would be a further customized footprint, with only specific pads being narrower, instead of all of them.

If fabrication handles it, I would consider the standard 24 mil pad size, with 10 or 12 mil guard trace

Thanks - it will take me awhile to work through this but I will - very much appreciate your efforts here. If you live close I will share wine from my winery if you like… :grinning:

OK - unzipped, pulled in the 21 mil version - edited the Metadata a bit, saved the new part - WORKS GREAT!!


:clap: :clap: :clap:

No modifications to keep out or anything - NICE!


Not much in the way of wineries near hear, so probable not close. Calgary, Alberta, Canada. But its a nice thought :slight_smile:

Shoot. What I meant by close - was lower 48 states of US. I can’t ship to Canada - they won’t allow it - Customs will seize it. If you are ever in California for whatever reason - I would be more than happy to send you home with a half case of wine. I have friends in Toronto and they have managed to get a few cases over the border somehow…

Thanks again. I learned a lot from you guys, and solved a problem!

One cause of this is if the svg is dimensioned in px rather than mm or in. There are at least 3 svg dpi values (72dpi for old illustrator, 90 dpi for Inkscape < 0.9.2 I think, and 96dpi for Inkscape 0.9.3 and greater. Fritzing will try and guess at what dpi value is in use but often gets it wrong which changes the scale in Fritzing. I know how to fix this in Inkscape, but not any of the other svg editors.


Thanks I will look into this - I hadn’t edited an SVG before and assumed that if I imported a drawing into the editor it would preserve the key features (metadata) of that drawing…apparently not.

OK - I used Inkscape and it worked perfectly - thanks. I think Inkscape is a far better editor for SVG than the one I attempted to use originally. Either that or it is just more straightforward and I could see scale, units, etc without even looking for them…LOL.

In this particular case the editor is doing the correct thing, the problem is Fritzing is being helpful and trying to guess what the DPI setting should be and sometimes guesses wrong (especially after the 90DPI to 96DPI shift.) I don;t know of a way (although there may be one) to get Illustrator to use mm or in for the dimensions. I don’t use Illustrator and no one who does has shared a way to get it to use in or mm in place of px so far.


Inkscape certainly has its quirks and bugs but it is open source and therefore popular in Fritzing and once you learn them it works fairly well. The main thing to watch is that Inkscape font size output will end in px (i.e. font-size=“35px”) as that is what CSS calls for, and Fritzing wants font-size=“35” or else it will change the font size to 0 when parts editor is used. The python part checking script I wrote fixes this as it checks the part, but if you don’t want to use that, then replacing the “px” with blanks via a text editor is a good bet with Inkscape (and I expect most other editors as well since I expect they will all be CSS complient,)