This free extension for Inkscape makes it easy to create a solder paste stencil for soldering SMT/SMD components to a PCB.

Commercial PCB stencils are laser cut from steel, but for prototypes it is quicker and cheaper to cut your own stencil on a hobbyist-grade laser. I've found vellum paper (200gsm) works well with solder paste, cuts cleanly, very cheap, can be cleaned with isopropanol (isopropyl) and reused to paste up to 10 PCBs.

This extension only works if your PCB was designed with the open-source KiCad EDA, as it relies on the export SVG feature.

Download the latest Inkscape and KiCad EDA packages.

How to install

To manually install this extension, download and unpack the archive file. Copy the pcb_stencil folder to the location listed by the Inkscape menu:

  Edit > Preferences > System: User extensions

For Windows users this will be something like:

  %APPDATA%\inkscape\extensions

Restart Inkscape and the new extension will be available from the menu:

  Extensions > Modify Path > PCB Solder Stencil

Export from KiCad

First export the solder paste layer from your design in KiCad's PCBNew, with just the F.Paste layer ticked:

  File > Export > SVG...

For PCBs with components on both sides you could export the F.Paste and B.Paste layers separately, then merge them into a single stencil. Or just cut as two stencils.

Using the extension

Load the exported solder paste layer into Inkscape, and open the extension from the menu:

  Extensions > Modify Path > PCB Solder Stencil

By default the extension will Annotate the stencil by engraving the filename & export date, but edit this for as much or little text as required. A 'stick' typeface is used for faster engraving.

If your PCB has fine pitch pads (under 0.8mm pitch) then you may need to experiment with the Shrink pads setting, depending on your laser and the stencil material. I've managed useable vellum stencils down to 0.5mm pitch, and 0805, 0603 or 0402 components certainly won't be a problem. Shrinking the pads will increase the gap between pads, so they stay intact to block paste from bridging pads.

Add Border simply adds space around the stencil to make it easier to handle. eg, if you are taping it down onto a PCB.

Finally clicking "Convert" will create the stencil. The cutting order of the pads is optimised so the laser head won't have to travel as far. The colours are red for engraved text, then the green pads are cut, and finally the blue outer cut releases the finished stencil.

Laser cutting the stencil

Send the finished stencil to your laser cutter like any other job. I use my own extension for laser cutting with LaserGRBL which exports to open-source software for controlling the laser cutter.

As with any material, you'll need to experiment to find the ideal cutting & engraving settings for your particular laser. On my 10W diode laser I engrave 1 pass 800 mm/min @ 40% power and cut 2 passes 650 mm/min @ 40% for 200gsm white vellum, with air assist. The vellum doesn't char so it can be hard to make the engraved text visible, without setting the laser so high that it just cuts clean through.

In the UK I can recommend Jackdaw Express who sell sheets of suitable vellum.

An alternative material is Kapton polyimide film (0.1→0.15 mm), but it is expensive to buy in small volumes and charred badly when cut with my diode laser. Perhaps it cuts much better with a CO2 laser? I found one creative user who makes stencils using a cheap roll of adhesive Kapton tape stuck onto normal paper to get the right thickness: 10 cent solder stencil using KiCad, kapton tape, and a laser cutter

Future ideas

Any feedback, suggestions or bug reports is VERY welcome. Below are some ideas, but I'll wait for feedback before working on them:

1. Import Gerber F_Paste.gbr files so works for all EDA packages, not only KiCad
2. Position annotated text as left/center/right, top/bottom of stencil
3. Keep pad stroke-width at 0.1mm, even after scaling for laser kerf
4. Does it need inches/metric setting, or does everyone use mm for laser cutting?
5. Add language translations. Please contact me if you'd like to contribute

Release v0.20 16/Apr/2025

• Refactored TSP code without numpy, now 14× faster
  slight reduction in travel distance by using center of each solder pad
• Inkscape v1.2 reads board name+date from SVG
• Added KiCad v6 and v7 support, not just v8 export SVG
• more options supported: Color Mode, Black and white Mode, Color themes, Current page size, Board area only
• Keeps pad stroke-width at 0.1mm, even after scaling for laser kerf