From idea to PCB

Hi everyone. Today’s project is the creation, from scratch, of a complete PCB. My aim here is to give you a ready-to-go method, allowing you to create your own PCBs with common products. I’ll try to give you as much advices as I can.

First, we need an idea. Something not too complicated. But something useful. Let’s build an iPhone charger. Here’s an early prototype I made a few months ago:

And le awesomely drawn schematic for it:

 

Let’s get rid of perfboards and create a real PCB.

First, let’s use Eagle to create our schematic. To those of you that are kinda unused to this, I heavily recommend that you watch rpcelectronics’ video tutorial on youtube. Here’s the first lesson:

Based on the schematic above, let’s create something neat with Eagle.

First, create a new project, let’s say “iPhoneCharger”:

Then, in this project, add a new schematic:

From this point, I will kinda fast-forward the creation of the schematic. If you’re familiar with eagle this should be a piece of cake. If not, refer to the youtube tutorial.

First, add 5V signal and GND:

The, from the “rcl” library, add 4 resistors. I use 7.5mm width resistors, feel free to use the one you want:

Wire all this stuff up:

Then, add USB port. I found out that “con-berg -> PN87520” fits perfectly the ones I have. Create connections using the NAME tool:

Next, voltage regulator:

don’t forget resistor values:

You’re done! Now switch to PCB:

Arrange a bit the components:

Here’s a not-so bad first try. Note that I used a 9V battery clip as a battery input, so there are two big pads I can solder wires on:

Ok now that the circuit is ready to go, here’s some advice before you go further.

Many recommend the use of glossy magazine paper, so that’s what I did. But it failed, here’s why. First, I cut a piece of PCB:

Then scrub it using sandpaper. The finer the sandpaper, the longer it will take, but the finer the result:

Dry the board, then print your schematic:

Place the printed schematic on the board, and iron it at max temperature for 2/3min. The toner will melt and stick to the copper :

Then, the trickiest part, removing the paper. Pour water on the paper to soak it, and gently rub it until it removes completely:

   Here’s where I failed: magazine paper absorbs a part of the toner, and that part won’t transfer. Here’s the results of various tests:

almost there! From this point I decided to use glossy photo paper. I found that 170 g/sqmeter is ok with my laser printer. I insist on the fact that I used GLOSSY paper. It transfered almost perfectly:

now, to the etching. Here again, there were some fails 😀

I used my failed PCBs to test the recipe. For my first try, I used this:

  • one half of 23% muriatic (hypochloric) acid, known as HCl.
  • one half of 30% hydrogen peroxyde, known as H2O2.

BEWARE:

always pour acid to H2O2, not the opposite: a drop of water/H2O2 in strong acid would boil immediately and provoke dangerous smoke/spills!!!

Always wear safety goggles, gloves, and work in a ventilated area: etching process may exhaust toxic HCl smoke!!!

Also use glassware, plastic stuff may melt!!!

I did all the rest outside, on a plastic garden table. I gently tossed the board and, in a blink of an eye, it was etched. I used plastic tweezers to retrieve it and transfer it to a bucket of water.

Once the board was clean from acid and dried, I used acetone to remove the toner and reveal copper tracks. The result is that the blending I used was way to strong to correctly etch the board without destroying some of the tracks:

From here I adjusted the formula to be a lot less aggressive:

  • 100 mL water
  • 66 mL H2O2
  • 33 mL HCl

It resulted in a more gentle etching process. It took 10mn instead of a few seconds, but the result was almost perfect:

They see me bubblin’, they hatin’

Now to the painting.

I found out on some websites that glass paint fits perfectly the job. I used “anise green” paint, applied a thick layer and used q-tips to remove paint on pads:

The end is coming soon!