![]() ![]() We suggest buying a large PCB and cutting it into small squares with a Dremel (I also read a paper cutter works fine). Note: The first time you attempt to make a PCB, you will most likely fail (we failed literally about 40 times. We could not tell the difference between an exposed board and a non-exposed board. The photoresist will look exactly the same after it has been exposed to UV light. You may have to experiment with different times depending on the height above the LEDs. We found that exactly 1 minute exposure time worked well. No scotch tape is necessary to hold the PCB down to the transparency. Stack about 8-10 textbooks on top of the PCB to make sure the photoresist is tightly pressed against the ink of the transparency. Place the PCB on top of the transparency, photoresist facing down towards the LEDs. While the room is somewhat dark, peel the white film off the presensitized circuit board to expose the photoresist. The ink should be facing up towards the sky. Place the printed transparency on the elevated plastic about 10 inches above the LEDs. ![]() Only use transparency paper with smooth surfaces.) ![]() From our experience, the textured side did NOT allow UV light to pass through. We had read a PCB tutorial where the guy used the textured transparency paper without problem. Note: We originally bought transparencies for inkjet printers and laser printers (one side was textured for use with inkjet printers, the other side was smooth for laser printers). We printed the circuit with our Brother HL-2070N (on highest quality) laser printer and MG Chemicals transparencies. The Layout is now ready to be printed, make sure that the image is mirrored so that text shows up correctly after being transferred onto the PCB. This is done by selecting View -> Display/Hide Layers in the Layout editor and selecting the correct settings. To print only the desired circuit, turn on only the Top Layer, Pads, Vias, and Dimension. The program can be downloaded from Once the schematic and layout are drawn, it is time to print the layout onto a transparency. One circuit schematic/layout program that is free is EAGLE. Q-Tips (local grocery store) -Buckets for chemicals (Ace Hardware) -Timer ![]() As you can see from my photo, my voltage was 11.9V and 3.47 Amps were consumed). Make sure your power supply can handle the current the LEDs consume. Instead we used Sn63/Pb37, 2.2% Flux, 23 gauge MG Chemical brand) -Screwdriver -26 and 16 gauge wire -Wire stripper -Gloves (bought at Ace Hardware) -Goggles (bought at Ace Hardware) -Power Supply (wall wart or benchtop power supply will do. Use if any acid is spilled on your skin) -Acetone (Ace Hardware) Tools: -Soldering Iron (any soldering iron will do, I used ) -Solder (We originally bought Lead free solder. 20 inch length x 12 inch width x 11 inch height) -Picture frame transparent plastic (Bought at Goodwill) Chemicals: -Muriatic Acid ( ) -Hydrogen Peroxide ( ) -Photoresist Developer (MG chemicals brand ) -Baking Soda (local grocery store. 4 Breadboards for LEDs ( ) -PCB Standoffs ( ) -Chest/box to house LEDs (Bought at Goodwill. 5mm size, 3.4~3.8 forward voltage, forward current 20 mA, wavelength (nm) 395-400-405, view angle about 25 degrees.) -200 470 ohm resistors (included with Asia Engineer LEDs bought on ebay. PCB: -Transparencies (MG chemicals brand ) -UV Presensitized Copper Clad Boards (MG chemicals brand ) -Laser printer (Brother HL-2070N) -200 UV LEDs (Bought from Ebay - Asia Engineer, seller giorgio11185. Our PCB tested the Atmel 208 pin PQFP Integrated Circuit ( it may not look like it from the poor image quality but there were no shorts between all 208 pins! ). All the supplies can be bought from Fry's Electronics, Ace Hardware, Goodwill, Radio Shack, and Ebay. It took us about 40 boards before we perfected our PCB, so we will share what worked and what didn't work. This instructable shows how to create well done PCB's using Ultraviolet light. ![]()
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