Very Easy Photo Etching Method

Fred_Fred asked to see the method I use to make my boards.

Here is the technique I use to make them:

First, you need a few basic supplies.

Transparency film

Positive resist copper clad board

Positive developer solution

Exposure light (I built my own)

Not shown:

Laser or inkjet printer (pick transparency film compatible with your printer)

Plastic trays to develop and etch in

One or two pieces of glass of plastic sheet (I use two sheets of glass I cut from an old window)

I also have a couple of optional items that make my life easier:

A small Drill Press and a Tile Saw.

First, I like to cut my boards to size:

The photo sensitive board has a protective white coating. Make sure when you are cutting

that the blade cuts down into this layer and not up through it.

Next, prepare your transparency:

You can print more than one on a sheet to save money, transparency film is not cheap.

The good thing is you can use them over and over. I like to cut them so they are

just a bit bigger than the board.

Now, you can take the board that you previously cut to size and remove the protective coating.

Line the transparency up with the board and set your glass on top of it. The glass keeps the

transparency flat and in close contact with the board. This is very important!

The side of the transparency that you printed on goes closest to the board.

Now you can expose your board to UV light.

My exposure time is about 13 or 14 minutes.

As soon as you are done, plop the board into the positive board developer.

I use a cheap foam brush to gently wipe back and forth across the board

to help the process along. It should take two to three minutes to remove the 

exposed etch resist. If it takes longer than this your exposure time is too short.

Here is the result:

Now they are ready for the copper etchant. I use the same foam brush technique here too.

Here are the boards etched and drilled:

You can clean the resist off when you are done with alcohol or you can leave it on. You can solder right through it.

Good luck with your boards!

Here is a USB DAC board I just did.

The transparency looks distorted because

of the way I am holding it. I was pretty

impressed in the detail I got. You can

still see the cross hairs in the drill hole

by the USB connector. We will see how

it looks after etching...

I got my chemicals locally, not very expensive.

Sayal (my local source) has as good or better

prices as Digi-Key.

I made the exposure light from a $13 under counter

fluorescent light I got at Wallmart. You can use any

18" fluorescent tube. The tube should be about

five inches from the board. I think mine is six inches.
 

Quote:

Originally Posted by jdkJake 

Very nice! Couple quick questions,

Where do you source your chemicals? Local or online? Expensive?

Any particular UV light (frequency)?

Thanks. Great results.

BTW, I remember not too many years ago when transparency sheets were cheap and abundant. Amazing how fast low cost projectors complete disrupted that market and made the technology mostly obsolete.

In the tank for etching...

Here is the after etching result...

And after cleaning with alcohol...

The traces used in this project were .024 inches

I am not currently doing any double sided boards though I do now the process

for making them. I have made lots double sided board for manufacture by

board houses. I find it more of a challenge to route everything single

sided and I am learning a lot about layout from the challenge.

Aligning (registering) the transparencies on both sides can be done

several ways. Cutting the board and the transparencies the same size

is a pretty easy way. Also dilling alignment holes through both the

board and transparencies can be a more accurate, if less convenient

way, of doing it.

That sounds like a pretty major malfunction in your process.

Do you remember what chemicals you were using and what

you did?

Quote:

Originally Posted by akgfan 

I tried that a few years ago and every time a put my pcb into developer my copper was completely away. Don't know what I did wrong.

Sodium Hydroxide (NaOH) is the chemical to remove the exposed etch resist from the board.

It will also remove the unexposed etch resist given enough time.

Ammonium Persulfate ((NH4)2S2O8) is the chemical I use to remove the copper from the board.

Ferric Chloride (FeCl3) is also very popular, but also very smelly and messy.

I know there are others as well but these are the two most popular.

The only thing I can guess is that your board were exposed to light for too long...

How long was it after you took the protective plastic off the board before you

exposed it? How long after you exposed it before you developed it?

Did you mix the developer properly? Mine is mixed 10 to 1 with water.

This is the developer I use.