Making PCBs at home is a great means to get your prototype up and running without having to wait weeks for a professionally made board. Regardless if these prototype boards are milled or etched, they are easily identified as ‘home brew’ due to their ‘unfinished’ appearance. [HomeDIY&Stuff] has put together a little how-to on the process for making DIY PCBs look a little closer to a professionally manufactured board.
The process starts out with designing the board in a PCB program. There are a lot of these programs available. Eagle is a popular choice and has a free version available. Once the layout it finalized, the design is printed out on a transparent sheet of plastic. A blank copper-clad PCB board that already has a UV sensitive coating applied are available for purchase and is what is used in this example. The transparency is placed over the PCB blank and then exposed to UV light. The coating on the PCB cures where ever the UV light passes through the open areas of the transparency.
Once the transparency is removed, there is a noticeable difference in coating color where it has cured. This board is now placed in a developer solution that removes the un-cured UV sensitive coating. A Ferric Chloride acid bath then etches away at the now-exposed copper. The cured coating from the previous step protects the copper at the trace locations during the etch process. The result is a board with copper where you want it and none where you don’t. If the board has any through-hole components, this would be the time to drill those holes.
Up to this point the process has been pretty standard for homemade PCBs and the next part is certainly the most interesting but, unfortunately, is also the worst documented step; the solder mask and silk screening. It appears that two silk screens are produced, one for the solder mask and one for the silk screen. The artwork for making the silk screens can be output from the PCB design software. There is no mention of the solder mask material used but oil-based silk screen ink is specified. Although the details are lacking, the photos show that it works pretty well. If you have had any experience with silk screening DIY PCBs, let us know in the comments.
