Hello makers, it's maker moekoe!
If you want to assemble PCBs at home you can use several tools which could get really expensive. For those of you loving SMD parts I will show a way to get around the costs for ordering SMD soldering stencils.
If you have a lasercutter at home you can use it to cut your stencils out of a piece of tape. Next to its cheapness, it has the awesome feature that it sticks to the PCB once you have aligned it correctly. Therefore you don't need to own a stencil station or holder which are really expensive. Unfortunately the stencils themself are really expensive, so the method presented in this Instructable could be really helpful for some of you makers.
In the next steps I will show you the procedure of cutting your own stencils by the example of my octoclick PCB. This PCB is just 40 by 40 mm and consist of many components. Smallest components are 0603 resistors and capacitors.
More infos to my octoclick project as well as to this project can be found on my Instagram blog.
Step 1: Warning!
As you might know, working with a laser is very dangerous in general. Especially for your eyes. I think that I don't have to remind you not to look directly into the laser. And always wear your safety glasses!
Furthermore, some materials are not usable with a lasercutter. Some cannot be cut related to the color of the material (acrylic glass) or to the atomic density (steel) and some others can be cut but shouldn't. Latter means that these materials produces chlorine gas during cutting and this is very unhealthy to your lungs and the environment.
I will link a detailed list of materials which can be used and which cannot be used for several reasons listed above.
One in advance: standard electrical tape cannot be used.
Step 2: Export Stencil As PDF
First of all you will have to export the suitable stencil of your PCB layout. I am using Autodesk Eagle, but this step should be somehow possible with every PCB layout software.
Just follow this few steps to export the so called cream layer as a PDF. As you can see in the pictures above, my Eagle software is set to german language, but if you swipe over the picture you can see several boxes belonging to the steps listed underneath.
- Inside the board viewer, hit the button for layer settings
- Hide all layers
- Select only one of the two cream layers (tCream for the top layer of your PCB,bCream for the bottom layer of your PCB)
- Hit the rect next to the layer name to open color menu
- Select the infill pattern to be black
- Hit OK once done and close the window
- Open the printing menu and select "Export as PDF"
- Deselect the option "Undertitle" and click OK
The file should appear in your Eagle project folder.
Step 3: Generate Laser Gcode From Stencil
Once you have exported the stencil from your layout software, you have to convert the PDF file into something readable for your lasercutter - Gcode. To do so, you can use your favorite software. I am using Inkscape with the laser plug-in from J Tech Photonics:
- Import the PDF in am empty window of Inkscape
- Place it to your needs, in my case it is the origin
- Go to Extensions - Generate Laser Gcode - Export
The settings for the Gcode tool and my 5500mW 445nm laser can be read out in the last picture of this step.
Step 4: Cut Your Stencils
When you are ready to go and have correctly exported your Gcode file, you can upload it to your CNC machine and cut it. Cutting process looks about 3 minutes for this PCB, which is quite fast.
The results are good enough to solder 0603 components, but as you might see the solder paste is slightly thick compared to a professional stainless steel stencil. Nevertheless, for me as a maker it is definitely worth it!
Hope this could help somebody.