Week5: Electronics Production

PCB Production process

Characterisation of Laser engraving

Using the Trotec Speedy 100 Flexx af the Photonic FabLab, Adrian and I studied the line test

With the "Cut then engrave x6" process we achieved a 127um resolution. Look at Adrian's page for full details and pictures.

Cutting holes with the CO2 laser is very durty.

Full "Laser" PCB workflow

I used Kicad to draw a PCB shematic and root it.

Then I exported the PCB in two file formats: colored *.svg for the Cu layer, and *.dxf for the Cu outline

Then using an image editor software, I fusioned those files on a green background:

NB: I used CorelDraw for the editing. I wanted to use Inkscape, but it wouldn't open the *.dxf files nor *.gerber files generated with KiCad... :/

I printed with the fibre laser (1um, 25W) of a Trotec Speedy 100 Flexx going through the API 'JobControl'.
Thanks to "JobControl" it is possible top associate a type of machining (power/speed/frequency) to each color.

It takes about 20min to print 2 PCBs

When the engraving is done, the PCBs are dirty. I cleaned them with propanol.

I cut the edge using a manual cutter (faster and cleaner than CO2 cut through FR4). Since there are only few holes, I also drill them manually.

Finally, I solder the PCB using solder paste, manual pick&place and a reflow oven.

Here's what the finished PCB looks like:

Engraving the Fab ISP

When engraving a PCB with laser it is critical to stay on focus. Delta of more than 0.1mm will cause failure.
That is why we use a holder (or a weight) in order to press the row FR4+Cu plate flat. Double side tape is NOT a viable option.

And here it is, soldered: