Etching PCB and have your own prototype in under an hour

PCB, Projects

I’ve always wondered how circuit boards were made. I decided to research and came up with this method. I have tried many chemicals and tons of exposure times when I started etching PCB.

Here is a list of materials I used to make a Printed Circuit Board (PCB)

  • Pre Sensitized Positive Acting Printed Circuit Board
  • Safety glasses
  • Nitrile gloves
  • old clothes
  • Two Plastic Containers
  • Resealable Bag
  • Sponge brush
  • A circuit design (can be drawn by had, I’m lazy and used software, best if  printed on transparency)
  • UV light source
  • pane of glass (plexiglass is fine)
  • Permanent Marker
  • Masking tape
  • funnel
  • utility knife
  • straight edge
  • Acetone
  • Sodium hydroxide (Developing Agent)
  • Ferric Chloride (Etching Solution)

Etching PCB

 

To start I will need to fill up one of the plastic containers with hot water. Then I grab a  resealable bag and fill the bag with a couple of ounces of ferric chloride. This stuff stains every thing so I am being as careful as possible and wearing my gloves and safety glasses.  Seal the bag and place it in the hot water. This is going to sit while we get everything and expose the pre sensitized board to UV light.Etching PCB

 

With the other plastic container I put some cold water in it and add a few flakes of the sodium hydroxide. I’ve notice that if I make the solution too strong it will remove all of the photo resist film immediately on the pre sensitive PCB.

Etching PCB

 

Now I prepare the board. I taped the transparency to the plexiglass, then taped the pre sensitized PCB to the glass (I had to use the utility knife to trip it to size). Made sure I lined it up to the design. I also taped some stuff behind the PCB so it will be push up against the circuit design. I used the florescent light as my UV source and expose the board for about 8 minutes (The time varies depending on the distance and strength of UV source).

Etching PCB

 

When the time is up, I dip the board in to make sure the solution is not too strong. This is something I play around with, if it is too strong I add extra water, if it’s too weak I add more sodium hydroxide. What tends to work for me is if it slightly discolors the film after 10 seconds or so, if the discoloring happens right away the solution is too strong. I put the gloves on after I know the solution is right

Etching PCB

 

I use the sponge brush to help develop it. The developing process takes me anywhere from 10 to 20 minutes depending on the concentration of the solution. When completed you should see only the film where the traces are.

Etching PCB

 

As you can see above, some of the film was removed where it shouldn’t of been.

Etching PCB

I fixed this with a permanent marker,I also wrote “Fosgu” on the board so you can see the marker a little better.

Etching PCB

 

I put the board in the bag with ferric chloride, replace the water in the plastic container with fresh warm water (this will speed up the process). I then aggravate the board by rubbing it, checking the board after 45 seconds to see how much copper needs  to be removed. Depending on how hot I got the water determines the etching time. It should take between 1 to 2 minutes with this method.

Etching PCB

When the board is completed, I remove it from the bag and rinse it with water. There will still be a little film left on the board I removed it with a little acetone.

 

Etching PCB

Here is my etched board. I will trim off the excess using a utility knife.

Etching PCB

Now I pour the ferric chloride back in the bottle for later, and dispose of contaminated water according to my city laws.

 

Please read my next blog on Tinning and Drilling PCB’s

*Note: If you decide to attempt to recreate any of these blogs, you do so at your own risk. Be sure to read all MSDS information when working with chemicals.

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