pcbetching
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pcbetching [2022-01-16 11:41] – jtdburton | pcbetching [2022-07-22 22:12] (current) – [Flux] MirZa | ||
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Sodium hydroxide (" | Sodium hydroxide (" | ||
- | Ferric chloride (etchant): Wear gloves. Wear eye protection. | + | Ferric chloride (etchant): |
- | ===== Design/file prep ===== | + | |
- | Prepare your design using your PCB software of choice (KiCad is a good open-source option). Start with nice thick traces (at least 0.8mm) | + | ===== Design |
- | Export one file with your cuts and another with your circuit traces. If you' | + | There are a few approaches to this process. These instructions will assume |
- | ===== Cutting ===== | + | Make sure to design your board with nice thick traces - start with at least 0.8mm and then try going smaller once you've got the hang of the masking and etching process. If you can fit everything onto a single-sided board, you might be able to use the laser cutter for cutting and drilling; if not, you'll need to use the CNC (both options are detailed below). |
- | With the CNC router not really in working order at the moment, the best way to cut your board is with one of the laser cutters. This is subject | + | The first thing to create |
- | Use your image editing | + | Open your plot file in your vector |
- | Place your workpiece in the laser cutter copper side DOWN. Cut settings may need some experimenting to get right. The aim is to cut all the way through the substrate without hitting the copper hard enough to cause lots of sparks. My best results have come from using the big laser with speed 35, power 60, corner power 50 on 1.5mm board. | + | ===== Cutting (CNC) ===== |
- | Run the cuts. Give it a couple of minutes before you open the lid, vapourised FR1/2 isn't as bad as FR4 but it's still unpleasant. | + | The CNC is a bit tougher to get going on than the laser, but it opens up a lot more options, most notably two-sided boards. |
+ | |||
+ | Start by going back to KiCad' | ||
+ | |||
+ | Now click " | ||
+ | |||
+ | Open up FlatCam and use File - Open Gerber to load your edge cuts and File - Open Excellon to load your drill plot. | ||
+ | |||
+ | //Tip: at each stage of the FlatCam process below you can save your settings for next time by going to Options - Transfer options - Object to Application.// | ||
+ | |||
+ | It's a good idea to go into the " | ||
+ | |||
+ | Double-click the drill plot in the layer list. You can skip over all the CNC settings here, just enter your tool size under "Mill Holes" (a 0.8mm bit is usually good) and click " | ||
+ | |||
+ | Now go back to the " | ||
+ | |||
+ | Back in the " | ||
+ | |||
+ | Double-click the new " | ||
+ | |||
+ | From here, pop the SD card in the CNC laptop, load it into LinuxCNC, and proceed with the usual CNC process. | ||
+ | |||
+ | ===== Cutting (Laser Cutter) ===== | ||
+ | |||
+ | Another way to cut your board, which you may find simpler, is with one of the laser cutters. This is subject to two major restrictions: | ||
+ | |||
+ | Start by going back to KiCad' | ||
+ | |||
+ | Now click " | ||
+ | |||
+ | Open up FlatCam and use File - Open Gerber to load in each of the three files you just created. Combine these using Edit - Join Geometry and export the newly created " | ||
+ | |||
+ | You should be able to improt this SVG directly into LaserCut 5.3, but it may take some cleanup in Inkscape/ | ||
+ | |||
+ | Place your workpiece in the laser cutter copper side DOWN. Cut settings may need some experimenting to get right. The aim is to cut all the way through the substrate without hitting the copper hard enough to cause lots of sparks. My best results have come from using the big laser with speed 25, power 60, corner power 50 on 1.5mm board. However, some boards are much tougher than others so your mileage can and will vary - try cutting out a small circle as a test for new stock. | ||
+ | |||
+ | If you're sure you've got usable laser settings, download and run your cuts. Give it a couple of minutes before you open the lid, vapourised FR1/2 isn't as bad as FR4 but it's still unpleasant. | ||
{{:: | {{:: | ||
- | Take the workpiece out and pop your board out of it. What you're doing here is snapping | + | Take the workpiece out and pop your board out of it. You'll need to snap the copper layer along the lines you've cut in the substrate, |
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- | ===== Exposure ==== | + | ===== Exposure ===== |
- | + | ||
- | Grab the laminator, some sellotape, and a pair of scissors from G1 before you start with this section. | + | |
Currently (as of January 2022) the lab has NEGATIVE photoresist, | Currently (as of January 2022) the lab has NEGATIVE photoresist, | ||
- | In the past the recommendation has been to use transparencies run off the laser printer | + | The best option for creating your UV mask is to print it onto some heavy tracing paper on the laser printer |
+ | |||
+ | {{: | ||
+ | |||
+ | You can also cut your trace pattern into a scrap bit of very thin plywood or black acrylic. | ||
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+ | |||
+ | Either way, once you have your mask ready, grab the laminator, some sellotape, and a pair of scissors from G1. | ||
Cut a piece slightly larger than your board from the roll of photoresist film kept wrapped in a black bag in the cabinet in G14. PUT THE ROLL BACK IN THE BAG - it's UV sensitive. | Cut a piece slightly larger than your board from the roll of photoresist film kept wrapped in a black bag in the cabinet in G14. PUT THE ROLL BACK IN THE BAG - it's UV sensitive. | ||
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Peel off the backing (this is incredibly annoying to do - a couple of pieces of sellotape on either side of the corner can help peel the layers apart) and apply the blue film to your board. Try to squeeze any bubbles or wrinkles out to the sides, then run the board through the laminator. The laminator should be set on the largest thickness setting (2x125MIC), and it helps to run it through two or three times to improve the bond. | Peel off the backing (this is incredibly annoying to do - a couple of pieces of sellotape on either side of the corner can help peel the layers apart) and apply the blue film to your board. Try to squeeze any bubbles or wrinkles out to the sides, then run the board through the laminator. The laminator should be set on the largest thickness setting (2x125MIC), and it helps to run it through two or three times to improve the bond. | ||
- | Put your mask and film-coated board together in a sort of deadly yet exciting chemical sandwich. Align as best you can using the mounting holes you hopefully punched out earlier, | + | Put your mask and film-coated board together in a sort of deadly yet exciting chemical sandwich. Align as best you can and add some sellotape to hold everything together. |
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Make a solution of about 500ml water and 20g washing soda crystals (sodium carbonate decahydrate). There is a handy 3D-printed scoop to help you get the right amount of washing soda. | Make a solution of about 500ml water and 20g washing soda crystals (sodium carbonate decahydrate). There is a handy 3D-printed scoop to help you get the right amount of washing soda. | ||
- | Immerse the PCB in the solution for a few seconds, then remove it. You should now be able to easily peel off the transparent film on the front. Return the board to the solution and start gently brushing it with the paintbrush. You should notice bits of the blue mask coming off. Once all the copper | + | Immerse the PCB in the solution for a few seconds, then remove it. You should now be able to easily peel off the transparent film on the front. Return the board to the solution and start gently brushing it with the paintbrush. You should notice bits of the blue mask coming off. Although it might look like all the unwanted |
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Where a trace has been broken, apply a solder bridge to reconnect it. | Where a trace has been broken, apply a solder bridge to reconnect it. | ||
- | ===== Flux ===== | + | ===== Protective coating |
- | Give your new board a spray with the can of flux. This will both prevent the copper traces from oxidising and make soldering to the board easier. Applies just like spraypaint - use back-and-forth motions from 20-30cm away. | + | Bare copper traces oxidise very quickly without any protection. |
+ | Give your new board a spray with the can of clear varnish after soldering | ||
+ | Mask off any buttons or mechanical components with masking tape so they do not get stuck. | ||
+ | |||
+ | Another option is to use tinning solution before soldering. | ||
- | Leave to dry for a couple of hours. | + | Congratulations, |
pcbetching.txt · Last modified: 2022-07-22 22:12 by MirZa