Introduction: Single Sided PCB Home Fabrication (Presensitized PCB)
Learn to fabricate Single Sided PCBs at home! Prototype PCB fabrication is one of the essential skills you must learn in electronics. Instead of using breadboards and perfboards, custom PCBs would make any project smaller and more compact! Presensitized PCBs Also Work With Inkjets!
PRESENSITIZED PCBs: Also known as photopositive PCBs or photoresist PCBs, are regular PCB copper clads, layered with a light sensitive paint or film. Once exposed to light, the paint would dissolve in the developing solution, while the unexposed areas would remain undissolved in the solution. This forms a Mask on the copper layer of the PCB. When the developed PCB is exposed to an etchant, the masked areas would remain in tact while the unmasked areas would dissolve on your etchant, thus forming a copy of your printed PCB artwork.
BETTER THAN TONER TRANSFER METHOD: Toner transfer method has been the number 1 go to in homebrew PCB fabcrication, next to the sharpie method. Toner transfer has its own limitations. One, is that you would need a toner printer, common inkjet printers simply wouldn't work. Second, as your line traces gets thinner, it would be more difficult to transfer the toner prints to the copper clad. Presensitized PCBs on the other hand creates the sharpest lines of all the homebrew fabrication methods. This is perfect for smaller circuits that involves SMT (Surface Mount) components. I use this method for building PCBs with line traces reaching down to 10mils (0.254mm). You can go as thin as 5mils (0.1275mm), but you would have to use inkjet friendly acetate.
WATCH MY FULL VIDEO TUTORIAL! :D
Step 1: Thing's You'll Need
Tools & Materials:
1.) Presensitized PCB Pack
- AliExpress: https://bit.ly/2WLOi0F
- Amazon: https://bit.ly/2WLOi0F
- E-Gizmo: https://bit.ly/2WLOi0F
2.) Ferric Chloride (Copper Etchant)
- Amazon: https://amzn.to/3cZu8pL
- Lazada: https://amzn.to/3cZu8pL
3.) Pure Acetone (Nail Polish Remover)
- Amazon: https://amzn.to/2zdVOIE
- Shopee: https://amzn.to/2zdVOIE
4.) Baby Oil
- Amazon: https://amzn.to/2ZrII54
- Lazada: https://amzn.to/2ZrII54
5.) Mini Drill
- AliExpress: https://bit.ly/2XaTJVX
- Amazon: https://bit.ly/2XaTJVX
- Lazada: https://bit.ly/2XaTJVX
6.) Drill Bits (0.8mm - 1.0mm)
- AliExpress: https://bit.ly/2WJNI3n
- Lazada: https://bit.ly/2WJNI3n
7.) LED/ CFL/ UV Lamp
- Amazon: https://amzn.to/3bOFoUq
- Lazada: https://amzn.to/3bOFoUq
8.) Cutter Knife
9.) Hack Saw
10.) Wooden Plank
11.) Plastic Containers
Step 2: Design or Acquire the PCB Layout
If you're planning to design your own PCB layouts, I recommend using softwares like Proteus, Eagle CAD or Altium. There are tons of YouTube tutorials on learning how to use these softwares. Out of preference, I usually use Proteus.
If you're building an existing project from the internet, chances are, the author has provided his or her PCB layout as a PDF file or as a JPEG. I really love PDFs since they are scaled formats of layouts. Just hit the print button and you're ready to go!
Step 3: Printer Settings
Recommended PDF Print Settings:
- Page Sizing: Actual Size
- Paper Type: Plain Papers
- Print Quality: High
Step 4: Cut and Transfer the Layout
After printing your layout, use a cutter and cut it from its boarders. You can use the layout as a stencil for cutting your PCBs later on.
Step 5: Collect & Select Your PCBs
Presensitized PCB usually come in tin foil packages. I usually store my boards in a plastic container, away from sunlight. These boards come in different shapes and sizes. I usually cut them down and keep all the leftover cutouts for smaller projects. I would usually select a board, closest to my PCB layout's footprint to avoid having leftover strips.
Step 6: Cut the PCB (Scoring Method)
There are plenty of ways cut a PCB. My favorite is the scoring method, the same method heavily used for cutting acrylic sheets. It's a clean and fast way for cutting Phenolic Based PCB boards. You can do this by using the blunt edge of your cutter blade and do several passes on the board (20-30 times). Then use a book to press it against the table. Finally bend the PCB till it breaks in half.
Step 7: Cut the PCB (Hacksaw Method)
If you're dealing with Fiberglass PCBs, the scoring method wouldn't work. The scoring method also wouldn't work with smaller or shorter strips. Use a hacksaw instead to solve this problem.
Step 8: Peel the Light Protective Film
Presensitized PCBs has a light protective film that prevents unintended light exposure from storage. You'll have to peel this film before you can proceed to the next steps.
Step 9: Apply Baby Oil (My Trick)
Most people would use Acetate or Parchment Paper for printing the PCB layout. Those types of paper are ideal for photo exposure since it allows more light to pass through. The disadvantage though, is that it's difficult to print on these types of papers using inkjet printers, since they blot more often.
Adding baby oil to your plain paper PCB layout would allow more light to pass through during the photo exposure process. It turns and plain paper into parchment paper.
Step 10: PCB Photo Exposure
You can use sunlight, a CFL Lamp, LED Lamp or a UV Lamp for photo exposure. It doesn't really matter which type of light you'd use, they all work. Although, take not that photo exposure duration would vary between the different types of lights.
My Recommended Exposure Times:
- CFL Lamps: 12 Minutes
- LED Lamps: 10 Minutes
- UV Lamps: 4-7 Minutes
CFL & LED Lamps: If you don't have an exposure box, you can sandwich your PCB and Layout between a piece of wood and glass. Point your lamp towards your PCB, make sure the light distribution is even, otherwise you'll have a vignetting effect.
Want to have more consistent photo exposures?
Watch my tutorial on building a DIY Digital LED/UV Light Exposure Box!
Step 11: Remove the Layout & Clean the PCB
Once you're done with the photo exposure, remove the PCB layout. You can use this as many times as you want. I recommend keeping it if you plan to build more boards with the same PCB footprint. I also recommend cleaning the board with soap to remove the oil. Leftover oils could affect the developing process in the next step, as the chemical developing solution would have a difficult time penetrating the oil to reach the photo-positive paint on the PCB.
Step 12: Prepare the PCB Developer
Presensitized PCB packs, usually come with developing solutions. Most often these solutions are packs of Sodium Hydroxide (a.k.a. Lye or Caustic Soda). You'll have to mix this with tap water in order for it to work. How's the ratio? Your PCB pack would usually come with mixing instructions. Most often you'll have to mix the granules with 500mL or 1L of water, depending on how much Lye is in the pack. Shake it well!
Step 13: Develop the Photo Exposed PCB
Pour your developing solution on a plastic container, then submerge your photo exposed PCB on the developing solution. The line traces should show up within a minute. If the lines show up too fast, quickly add water. Over-concentrated solutions can ruin your PCB traces. If the lines, take too long to show up, this means you'll have to add more developing granules as your solution may be over-concentrated.
Be sure to agitate the tray. You can remove the PCB from the solution once all the paint from the unmasked areas are dissolved. Leaving it too long would dissolved the masked traces as well. I suggest placing a container of tap water beside. Rinsing the board with water quickly stops the developing process.
The developing solution can be used for up to 10 times, but I did notice that the effectivity starts to degrade the moment you use it. Be sure to use only the amount you need.
CAUTION: Please wear latex gloves and wear protective goggles when dealing with these chemicals. For this video, I ran out of gloves at the moment due to the massive shortage of medical supplies due to the COVID19 pandemic. Lye (developing solution) can be corrosive to human tissue, for this project, the concentration of lye is quite low. I washed my hands thoroughly after getting exposed to it.
Step 14: Inspect the PCB for Scratches
Now, inspect your PCB for broken traces. You use a marker (sharpie) to retouch the broken traces. If there's paint left on areas there aren't supposed to be on, use a blade to scratch it off.
Step 15: Choose an Etchant
Before we get to the etching, there are two types of enchants commonly used for PCB fabrication. On the left is Ferric Chloride, it's the safer enchant for newbies to use as it is only corrosive to metals and not plastics or human tissue. Etching time is slow with this one.
On the right is a homebrew mixture of Hydrogen Peroxide and Muriatic acid. It's a really strong etchant, I wouldn't recommend this for first-timers as it is really dangerous to human skin. A fellow author here at instructables made a tutorial about this, check out "The Real Elliot's" tutorial on this homebrew etchant (Link: Stop Using Ferric Chloride Etchant!)
Step 16: Etch the PCB
Submerge your photo-developed PCB on the etching solution. Agitate your tray and observe it until the unmasked areas dissolve. I really hated this process since it takes up so much time, that's why I made a PCB Shaker, I'll post a tutorial about it on the near future. You can subscribe to my Instructables & YouTube channel for updates.
Step 17: Inspect Again
Once you've finished etching. Inspect your board again for shorted lines or broken lines. Shorted lines can be removed by scratching it with a blade. Broken lines on the other hand can be fixed by soldering a bridge of bare copper wire between the broken traces.
Step 18: Ways to Remove the Paint
Soldering with the paint still on would be difficult. You'll have to remove the paint. There are two ways to do this. One is by scratching it off using a fine grit sand paper, years later, I learned that this was a bad ide for boards with thin traces since tinier lines could get dislodged from the board. Use Paint Thinner or Pure Acetone instead! With a few drops, you can easily wipe of the paint using a tissue paper.
Step 19: Drill Holes
Grab your mini drill and drill the holes for your components. Recommended drill bits for THT PCB fabrication are 0.8mm (for thin lead discrete components) and 1.0mm bits (for large transistors and etc...).
Step 20: Solder the Components
A PCB layout usually comes with a Parts Placement diagram as well. Follow it for mounting your components, then solder your component's leads to the copper side of the PCB. Now you have a working circuit!
Step 21: Enjoy!
I hope you liked this project! Feel free to leave down some comments for feedbacks or questions.