ee:pcbetching
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ee:pcbetching [2019/01/11 12:39] FKR@staff.hsrw |
ee:pcbetching [2021/03/08 13:39] (current) |
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| - | ===== Etching PCBs ===== | + | ====== Etching PCBs ====== |
| - | ==== Disclaimer ==== | + | ===== Disclaimer ===== |
| This instruction has been written for a supervised session performed in a chemical lab. Be careful when applying to a different environment. | This instruction has been written for a supervised session performed in a chemical lab. Be careful when applying to a different environment. | ||
| - | ==== Introduction ==== | + | ===== Introduction ===== |
| This instruction is about producing printed circuit boards (PCBs) from already prepared designs. There are two major techniques for PCB manufacturing. For prototyping purposes it is popular to use a special milling machine for PCBs. The faculty uses a LPKF ProtoMat S62 in its [[ee:electricalworkshop|electrical workshop]]. EAGLE board designs are exported to gerber and excellon files and after making some adjustments in a CAM tool like CircuitCAM designs can be used for milling out copper-clad boards. The machine isolates all traces on the board and drills holes where necessary. | This instruction is about producing printed circuit boards (PCBs) from already prepared designs. There are two major techniques for PCB manufacturing. For prototyping purposes it is popular to use a special milling machine for PCBs. The faculty uses a LPKF ProtoMat S62 in its [[ee:electricalworkshop|electrical workshop]]. EAGLE board designs are exported to gerber and excellon files and after making some adjustments in a CAM tool like CircuitCAM designs can be used for milling out copper-clad boards. The machine isolates all traces on the board and drills holes where necessary. | ||
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| - | ==== Resources ==== | + | ===== Resources ===== |
| Here is a list of supplies you probably need: | Here is a list of supplies you probably need: | ||
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| * [[https://www.reichelt.de/-p89770.html|toner compressor]] | * [[https://www.reichelt.de/-p89770.html|toner compressor]] | ||
| * [[https://www.reichelt.de/-p9486.html|solderable protective spray]] | * [[https://www.reichelt.de/-p9486.html|solderable protective spray]] | ||
| + | * paper towels | ||
| Optimally this process is executed in a chemistry lab. This is the list of needed tools: | Optimally this process is executed in a chemistry lab. This is the list of needed tools: | ||
| * [[https://www.reichelt.de/-p23418.html|etching machine]] (if you have exacly this machine, torx screwdrivers are handy) | * [[https://www.reichelt.de/-p23418.html|etching machine]] (if you have exacly this machine, torx screwdrivers are handy) | ||
| - | * UV expusure unit (light from both sides) | + | * UV expusure unit, preferably with light bulbs from both sides |
| * magnetic stirrer (optional) | * magnetic stirrer (optional) | ||
| * thermometer (optional) | * thermometer (optional) | ||
| Line 39: | Line 40: | ||
| * scoop | * scoop | ||
| * glass stirrer | * glass stirrer | ||
| - | * paper towels | ||
| * cotton pad | * cotton pad | ||
| * stapler | * stapler | ||
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| * lab coat | * lab coat | ||
| * gloves | * gloves | ||
| + | ===== Procedure ===== | ||
| + | ==== Masks for uv exposure ==== | ||
| + | The PCB design should already be finished and the artwork should be ready. If not there is a separate guide on how to [[pcbuvmasks|create masks for uv exposure]]. | ||
| ==== Safety instructions ==== | ==== Safety instructions ==== | ||
| - | Please read the chemistry lab safety rules on Moodle before taking the experiment. The safety rules will also be pointed out at the beginning of the experiment. | + | The following substances will be used: |
| - | + | ||
| - | We will work with the following substances in this lab: | + | |
| * toner compressor | * toner compressor | ||
| - | * Developer / sodium hydroxide (Natriumhydroxid, NaOH) | + | * developer / sodium hydroxide (Natriumhydroxid, NaOH) |
| - | * Etchant / sodium persulafte (Natriumpersulfat, Na<sub>2</sub>S<sub>2</sub>O<sub>8</sub>) | + | * etchant / sodium persulafte (Natriumpersulfat, Na<sub>2</sub>S<sub>2</sub>O<sub>8</sub>) |
| - | * item ethanol (C<sub>2</sub>H<sub>6</sub>O) | + | * ethanol (C<sub>2</sub>H<sub>6</sub>O) |
| - | * item distilled (purified) water (H<sub>2</sub>O) | + | * distilled (purified) water (H<sub>2</sub>O) |
| - | ==== Masks for uv exposure ==== | + | Make yourself familiar with safety precautions for these substances and read the safety data sheets for them. |
| - | The PCB design should already be finished and the artwork should be ready. If not there is a separate guide on how to [[pcbuvmasks|create masks for uv exposure]]. | + | |
| + | As stated in the beginning the following steps are normally performed in a proper lab after special security instructions and under supervision. | ||
| ==== Set up developing and etching solutions ==== | ==== Set up developing and etching solutions ==== | ||
| - | Get your safety equipment. This includes glasses, lab coat and gloves. Make yourself familiar with the provided tools. | + | Put on your safety equipment. This includes glasses, lab coat and gloves. Make yourself familiar with the tools. |
| - Make sure you have a bowl like shown in <imgref bowl>. It will be used as container for the development solution. You should also have a 500 ml beaker (see <imgref beaker>) for measurement, a glass rod for stirring and a weighing boat. | - Make sure you have a bowl like shown in <imgref bowl>. It will be used as container for the development solution. You should also have a 500 ml beaker (see <imgref beaker>) for measurement, a glass rod for stirring and a weighing boat. | ||
| - Fill the beaker with 250 ml distilled water. | - Fill the beaker with 250 ml distilled water. | ||
| - | - Get 5g sodium hydroxide from the front of the classroom and fill it into your beaker. In order to get the right amount use the precision scale and a weighing boat. Close the container of sodium hydroxide as sodium hydroxide is hrydrophilic. | + | - Fill 5g sodium hydroxide into your beaker. In order to get the right amount use the precision scale and a weighing boat. Close the container of sodium hydroxide as sodium hydroxide is hrydrophilic. |
| - Stir the liquid in the beaker with a glass rod until everything is dissolved. | - Stir the liquid in the beaker with a glass rod until everything is dissolved. | ||
| - Pour the solution into the plastic bowl. | - Pour the solution into the plastic bowl. | ||
| - Make sure you have a big glass beaker like shown in <imgref beaker>, a magnetic stirrer (see <imgref magnetic_stirrer>), a thermometer and a small beaker with sodium persulfate. | - Make sure you have a big glass beaker like shown in <imgref beaker>, a magnetic stirrer (see <imgref magnetic_stirrer>), a thermometer and a small beaker with sodium persulfate. | ||
| - Fill the big beaker with approximately 1.6 liter of distilled water. | - Fill the big beaker with approximately 1.6 liter of distilled water. | ||
| - | - Add 300g sodium persulfate to it, it should be already prepared in the second beaker. | + | - Add 300g sodium persulfate to it. |
| - | - Use the magnetic stirrer to heat the big beaker up and help dissolving the sodium persulfate at the same time (setting 4 / 4). As etching etching works best above 40°C (and below 50°C). Try to heat the solution up until it reaches 40°C. | + | - Use the magnetic stirrer (if available) to heat the big beaker up and help dissolving the sodium persulfate at the same time (setting 4 / 4). As etching etching works best above 40°C (and below 50°C). Try to heat the solution up until it reaches 40°C. |
| + | - If there is no magnetic stirrer available, stirr the solution and continus. The etching machine also has a heater, it will just take longer. | ||
| - When the solution is ready turn off the magnetic stirrer and pour the solution **carefully** into the etching device. | - When the solution is ready turn off the magnetic stirrer and pour the solution **carefully** into the etching device. | ||
| - Turn on the heating and air compressor of the etching device by plugging it into the electric outlets. | - Turn on the heating and air compressor of the etching device by plugging it into the electric outlets. | ||
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| - Get the transparent foils containing your PCB design. | - Get the transparent foils containing your PCB design. | ||
| - | - Go to the fume cupboard at the end of the room and apply some density spray to both foils. Make sure to apply it on the side with the printing. | + | - Apply some density spray to both foils. Make sure to apply it on the side with the printing. This step has to be executed in a well ventilated room, if available do it under a fume cupboard. |
| - | - Wait for it to dry. The black areas should be clearly darker now. | + | - Wait for the density spray to dry. The black areas should be clearly darker now. |
| - | - Use the scissors to cut out your design. Leave a big surrounding area, as you will nedd it for stapeling. | + | - Use scissors to cut out your design. Leave a big surrounding area, as you will nedd it for stapeling. |
| - Place the foils on top of each other. The sides with the printing on it have to be facing each other (the board will be in between of the foils later). | - Place the foils on top of each other. The sides with the printing on it have to be facing each other (the board will be in between of the foils later). | ||
| - Staple the foils together while trying to align them perfectly. | - Staple the foils together while trying to align them perfectly. | ||
| - Check the alignment. Misalignments will probably result in defective PCBs later. | - Check the alignment. Misalignments will probably result in defective PCBs later. | ||
| - | - Get a piece of fotensensitive base material (FR4 in this case) for exposure. It will be slightly bigger than your design so you should have no problems with that. | + | - Get a piece of fotensensitive base material (FR4 in this case) for exposure. It should only be slightly bigger than your design. If necessary cut it with a plate shear. |
| - Remove the blue protection foil (see <imgref RemoveProtectionFoil>) on both sides. | - Remove the blue protection foil (see <imgref RemoveProtectionFoil>) on both sides. | ||
| - | - Avoid exposing the unprotected plate to sunlight (all UV sources). | + | - Avoid exposing the unprotected plate to sunlight (all UV sources). Best to have a special room for this step, if not available make sure to not waste to much time. |
| - Put the copper plate between the transparent foils and put both under the glass plate of the uv exposure device (see <imgref UVExposureDevice>, <imgref BoardUnderPlate>). | - Put the copper plate between the transparent foils and put both under the glass plate of the uv exposure device (see <imgref UVExposureDevice>, <imgref BoardUnderPlate>). | ||
| - **Beware:** For your own safety avoid looking into the uv lights. The device is to be only turned on when closed! | - **Beware:** For your own safety avoid looking into the uv lights. The device is to be only turned on when closed! | ||
| - | - Turn it on and wait for the vacuum to go up to 0.3, compare to <imgref CheckVacuum>. The vacuum prevents things from moving. | + | - Turn it on and wait for the vacuum to go up (to 0.3 with our device, compare to <imgref CheckVacuum>). The vacuum prevents things from moving and presses foils and PCB together. |
| - | - Set the exposure time to two minutes and thirty seconds (the display should read 2-3-0), make sure the bottom lights are also enabled as you are making a two sided PCB and start the device by pressing the knob once. | + | - Set the exposure time to two minutes and thirty seconds (the display should read 2-3-0), make sure the bottom lights are also enabled if you are making a two sided PCB and start the device by pressing the knob once. |
| - When the time is up the lights will automatically be turned off and the vacuum will be released. | - When the time is up the lights will automatically be turned off and the vacuum will be released. | ||
| - Open the device and get out the exposed board. | - Open the device and get out the exposed board. | ||
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| - Brown residues from the exposed parts of the board should start to appear after a couple of seconds. Stir until the process seems to stop and take it out immediately. Do not leave the board in for longer than 90 seconds maximum. | - Brown residues from the exposed parts of the board should start to appear after a couple of seconds. Stir until the process seems to stop and take it out immediately. Do not leave the board in for longer than 90 seconds maximum. | ||
| - Rinse the board thoroughly with (purified) water. | - Rinse the board thoroughly with (purified) water. | ||
| - | - Check the temperature of the etching solution, it should be above 40 and below 50 degrees C. | + | - Check the temperature of the etching solution, it should be above 40 and below 50 degrees C. If not, keep waiting. |
| - | - Mount the board to the grey retainer (see <imgref Holder>). To speed up the procution process mount two boards at the same time. | + | - Mount the board to the grey retainer (see <imgref Holder>). To speed up the procution process you may want to mount two boards at the same time. |
| - Submerge the board(s) in the tank. | - Submerge the board(s) in the tank. | ||
| - Wait for the etching process to complete. You may have to wait a couple of minutes before something seems to be happening but from this point it should be going quite fast and obvious. | - Wait for the etching process to complete. You may have to wait a couple of minutes before something seems to be happening but from this point it should be going quite fast and obvious. | ||
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| - Shut down pump and heating. | - Shut down pump and heating. | ||
| - Use ethanol and paper tissue to remove the remaining photoresist from the board(s). Be thorough. | - Use ethanol and paper tissue to remove the remaining photoresist from the board(s). Be thorough. | ||
| - | - Let the board(s) dry. | + | - Let the board(s) dry. You can also use compressed air to speed things up. |
| - Clean the lab equipment, rinse everything with water. | - Clean the lab equipment, rinse everything with water. | ||
| - Dispose of waste properly. | - Dispose of waste properly. | ||
ee/pcbetching.1547206751.txt.gz · Last modified: 2021/03/08 13:39 (external edit)
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