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--- pcbetching [2022-01-19 20:58] – [Developing] jtdburton
+++ pcbetching [2022-02-01 17:17] – jtdburton
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 Ferric chloride (etchant): Moderately corrosive, strong skin and eye irritant, toxic if consumed, toxic vapours. Wear gloves. Wear eye protection. Open a window and/or switch on the air filter. Can be reused for months or even years, so you shouldn't need to dispose of it; if you do, there's a tub under the sink for the used stuff. DO NOT flush down the drain.
-===== 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) and then try going smaller once you've got the hang of the masking and etching process.
+===== Design and Trace File Prep =====
-Export one file with your cuts and another with your circuit traces. If you're making a double-sided board, you'll need one trace image for each side, but double-sided boards are trickier right now (see notes under "Cutting" below). Note that KiCad doesn't actually export all through-holes on the "edge cuts" setting. You might find it easier to export a single image with your copper traces and "print board edges on all pages" ticked, then separate the traces/pads from the holes in Inkscape/Illustrator/etc.
+There are a few approaches to this process. These instructions will assume you're using KiCad and FlatCam (both open source) for PCB design and file manipulation.
-===== 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. Try to fit everything onto a single-sided board if possible, as this means you can use the laser cutter for machining which is currently much simpler than the CNC (see notes under "Cutting" 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 to two major restrictions: use FR1 or FR2 boards ONLY (FR4 vapourises into some VERY nasty stuff), and use only single-sided boards (you can't laser through copper).
+The first thing to create is your trace file. In KiCad, go to File - Plot. Set "Plot format" to "SVG". Select your copper layers ("F.Cu", "B.Cu", or both). Tick "Plot Edge.Cuts on all layers" (this is to help you align the mask to your cut board), make sure "Drill marks" is set to "None", and click Plot.
-Use your image editing software of choice to prepare your cut file for lasering. It needs to be a vector with all shapes as outlines and no fill, and it needs to be mirrored either in your image editor or once you import it into the LaserCut software.
+Open your plot file in your vector editing programme of choice and invert the colours (assuming you're using negative photoresist film - see notes under "Exposure" below). In Illustrator, the easiest way to do this is to create a white filled rectangle slightly larger than your board, put it behind your traces, and then select all and click "Edit" - "Edit Colours" - "Invert Colours".
+===== Cutting (Laser Cutter) =====
+The simplest way to cut your board is with one of the laser cutters. This is subject to two major restrictions: use FR1 or FR2 boards ONLY (FR4 vapourises into some VERY nasty stuff), and use only single-sided boards (you can't laser through copper). Instructions for cutting a board with the CNC router will be added here eventually, but the file prep steps are similar so you may be able to figure it out for yourself.
+Start by going back to KiCad's Plot dialogue. Make sure "Edge.Cuts" is the only layer selected. Select the Gerber plot format and click Plot.
+Now click "Generate Drill Files...". Select "Gerber X2" as your file format here, and click "Generate Drill File". This will create two files, one for plated and one for non-plated through holes.
+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 "Combo" layer as an SVG.
+You should be able to improt this SVG directly into LaserCut 5.3, but it may take some cleanup in Inkscape/Illustrator first.
 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.
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-Take the workpiece out and pop your board out of it. What you're doing here is snapping the copper layer along the lines you've cut in the substrate, it'll be tough but doable. You may need to flex the board a bit. You can leave the through-holes for now, although you may find it useful to punch out any mounting holes to help you align the trace design in the exposure step. Note that you'll lose some copper around the edges of whatever you pop out, so only do this in non-critical areas of your board.
+Take the workpiece out and pop your board out of it. What you're doing here is snapping the copper layer along the lines you've cut in the substrate, it'll be tough but doable. You may need to flex the board a bit. You can leave the through-holes for now, although you may find it useful to drill out a couple to help you align the trace design in the exposure step.
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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.
-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, and add some sellotape to hold everything together.
+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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