uv_pcb_etching_kit
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+ | Photo-chemical PCB etching has been perfected! | ||
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+ | After much trial and error, and one foiled attempt at burning down the whole building, the NSL UV PCB kit is now ready for some serious action. It's true that milling boards on the CNC machine is pretty freakin' | ||
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+ | ==== Before getting started: | ||
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+ | **1) Why etch your own PCB? | ||
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+ | There are a couple of reasons.& | ||
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+ | **2) What do you need? | ||
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+ | There are two main things that you need: A pcb design, and a photosensitive board (positive process). At the lab, there are already chemicals, gloves, and vellum for transparencies, | ||
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+ | **3) Do this first** | ||
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+ | As soon as you get to the lab, start heating up the plate etchant. It will take about a half-hour to get the etchant up to the recommended temp (55C), but, as long as it's warm, you'll be able to make a good PCB without waiting forever for it to develop.& | ||
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+ | ==== Preparing the transparency: | ||
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+ | **1) Make your design ** | ||
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+ | Using your favorite PCB layout software, build a basic PCB layout. You won't have to worry about silkscreens and soldermasks, | ||
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+ | **2) Print your design** | ||
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+ | Print out your bottom layer design and pads, right-reading, | ||
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+ | **3) Transfer your prints to a transparency sheet.** | ||
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+ | This doesn' | ||
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+ | ==== Getting ready to expose the board: | ||
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+ | **1) Trim the transparency** | ||
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+ | Cut your transparency so that it's only a little bit past the edge of the design.& | ||
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+ | **2) Trim the board** | ||
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+ | Your board should only be a little bit larger than your transparency. You can trim it down by scoring the copper side (the side with a white protective plastic film on it) with a utility knife. You might need to score it two or three times to get a good, deep score.& | ||
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+ | ==== Exposing the Board: | ||
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+ | Read this part ahead of time and understand it.& | ||
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+ | **1) Put some tape on the edge of your transparency, | ||
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+ | Make sure that you do this while the toner side of the transparency is facing in the same direction as the sticky side of the tape. The toner is going to be touching the photographic emulsion.& | ||
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+ | **2) In very dim lighting, remove the white film from the copper side of the board. ** | ||
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+ | Do this slowly to make sure that the emulsion doesn' | ||
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+ | **3) Tape the transparency to the board**. | ||
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+ | Make sure that it is nice and flat, without bends or warps. | ||
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+ | **4) Place the board with the taped transparency beneath the UV light** | ||
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+ | Put the clear sheet of plexiglass on top of it to push the transparency as close as possible to the plate itself. | ||
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+ | **5) Turn on the light** | ||
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+ | Depending on your transparency quality, you will need different exposure times. For a clear transparency, | ||
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+ | ==== Developing the board: | ||
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+ | Here begins the wet part of the job.& | ||
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+ | **1) Remove the transparency** | ||
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+ | **2) Put the board into the dish marked "UV Developer", | ||
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+ | **3) Add about 1/2 inch of Developer to the the dish with the board in it.& | ||
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+ | Allow to soak for 3-4 minutes.& | ||
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+ | **5) Check in better light** | ||
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+ | The board should be able to handle some light now, so very quickly take a look at it under slightly better, but still dim light. Make sure that the traces are nice and green/blue, and the spaces are shiny and bright. Your pads and traces should be solid.& | ||
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+ | **6) Rinse board with cold water to stop the reaction.** | ||
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+ | Give the board a nice long rinse under tap water. The developer chemistry is just lye, which is a strong base, so try to avoid getting any into the etchant, as this will shorten its lifespan. Also, lye can be disposed of down the drain, so plenty of rinsing is not a problem. | ||
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+ | ==== Etching the board: | ||
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+ | Almost done. But this step is the worst.& | ||
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+ | **1)Get ready to dip ** | ||
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+ | Using one of the little plastic clips and a length of plastic-coated wire, fasten your board to the plastic board holder that rests on top of the etching tank. It's a tiny piece of plastic about 1" long, and it straddles the tank. | ||
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+ | **2) Let it soak for 4-5 minutes. Agitate occasionally.** | ||
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+ | The etchant tank should be a bubbling cauldron of warm, viscous liquid. It should do a fine job of agitating the board, but it doesn' | ||
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+ | **3) How will you know if the board is ready? | ||
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+ | It's almost magical. When the etchant makes it all the way to the fiberglass, the spaces on the board suddenly become translucent. Make sure to give some attention to small spaces between traces, to ensure that no accidental connections occur between traces. | ||
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+ | **4) Rinse it off** | ||
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+ | Once it is rinsed, you can take a good close look at the board and see if it's really finished.& | ||
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+ | ==== Remove the green emulsion: | ||
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+ | **1) Put your board in the tray marked Alcohol** | ||
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+ | **2) Add a half-inch or so of alcohol to the tray** | ||
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+ | **3) Allow it to soak for a few minutes.** | ||
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+ | **4) Rub clean with a soft rag** | ||
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+ | **5) You are done.& | ||
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+ | Clean everything up, and then go play solder-monkey. Have fun drilling those holes you never counted. Hint:& | ||
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+ | ==== How not to fuck it all up: ==== | ||
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+ | I've got some really awful boards here, as well as some good ones. If you would like to make your own lousy boards, please disregard these instructions | ||
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+ | **1) Don't touch the board** | ||
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+ | My experiments have shown that you can make a very high-quality board without ever touching the board with a sponge or any type of cleaning equipment. The slightest scratch on the etch-resist emulsion will typically result in a scratch in the copper that goes all the way to the fiberglass. | ||
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+ | **2) Make sure the transparency lies flat on the board when you expose** | ||
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+ | If you don't, you will get lousy edges everywhere made from soft shadows instead of hard shadows. | ||
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+ | **3) Don't over-etch or over-develop** | ||
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+ | After a while, the processes will begin to shrink your traces until they don't connect anymore, or they' | ||
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+ | **4) Before etching, touch up your developed board with an industrial Sharpie.** | ||
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+ | If you've made an obvious mistake, you can correct it before etching. Some Sharpies (marked " | ||
uv_pcb_etching_kit.txt · Last modified: 2013/08/13 12:13 by 127.0.0.1