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Etching your own copper panels #2: Process Summary

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Blog entry by splintergroup posted 10-28-2016 07:54 PM 762 reads 2 times favorited 3 comments Add to Favorites Watch
« Part 1: Intro. Part 2 of Etching your own copper panels series Part 3: Making the Image Mask »

I’ll give the entire process a quick summary here an then show the details with an actual project.

Be aware that there are plenty of ways to accomplish this process, do a web search on “making PC boards” or something similar.

I’ve used a number of methods when I was young. Most worked ok, but mostly they had the benefit of being cheap!

The Resist:

To etch copper with a pattern, you want some method of keeping the etchant away from the areas you don’t want etched (obviously!). To do this, you need to apply an acid resist to the copper. Where ever the resist is, the copper will not be removed. My first ever attempt at this was to use a permanent marker and draw the pattern onto the copper free-hand. It actually worked! The problem is virtually no control over detail and of course the total lack of talent for free-hand drawing 8^)

Most recently I tried using a laser printer and some thin/glossy magazine paper (unprinted). The idea is that the pattern is printed onto the paper and then that paper is attached to the copper and heated with a clothes iron. The heat re-melts the toner and bonds it to the copper. A bath in water softens the paper, allowing it to be easily brushed away. the toner topped copper has a durable acid resist coating. The problem here was inconsistency! Sometimes the toner just would not stick to some areas.

Anyway, the purpose of mentioning these methods is that you might want to give them a try yourself. The resist is the most “expensive” part of the process (behind the PCB board itself).

I’ve settled on photo resist. Basically it is a paint that is applied to the entire copper surface. The paint (after drying) is then exposed to ultra violet light, through a “mask” which contains the pattern you are creating. Areas not protected by the mask are exposed to the UV and the resist is chemically altered into a very tough surface. Areas that are not exposed to UV are washed away chemically, leaving the copper surface with acid resist in a negative pattern of your mask. This is called a “negative resist”.

The great thing about the photographic process is you can achieve virtually unlimited detail and fine lines.

There are other photo resists/methods, but as I said, this is how I’m doing it currently and it works for me….

The resist comes on a slow boat from China ( source ):

(the container should be sealed up a bit better when you receive it 8^).

About $7 for a few ounces, enough to cover a number of square feet of copper surface.

The Exposing:

You need a UV light source. You can find plenty of examples on the internet of people using compact florescent bulbs, black lights, LEDs, etc. I’ve gone to using a cheap fingernail polish curing light. This produces consistent results

This unit cost about $20. It comes with 4 bulbs (9 Watts each), but I only installed two of them, leaving me with a couple of spares. It is large enough to use on a 12”x12” panel if needed. This light produces the correct spectrum for the resist I referenced. I’ve tried a pond sterilizer, but the UV spectrum was wrong and it didn’t work. You can use sunlight, but the exposure time will vary and you lose the repeatability.

Develop

Simple! Soak the PCB in a solution of washing soda for a few minutes. Anything not exposed to the UV light will magically dissolve.

Etch

I use Ferric Chloride (FeCl3) since I have a stash from many years ago. You can still buy it, but it has gotten expensive. I am intrigued by a method that used pool cleaner (Hydrochloric/muratic acid) and Hydrogen Peroxide.
This is the ultimate in cheap and the method is described here

Strip the Resist

The resist is tough! After etching you need to remove it from the copper. You can sand it away, but them you risk damaging the thin copper layer.
Lye (aka drain cleaner) works perfectly. Get the “pure” lye at a hardware store. A few minutes of the panel soaking in a lye solution will have the resist floating away.

Thats the basics!

Obviously there are a lot of details left out. I’ll address these with an actual example of creating a panel for a project I am building.

Next time I’ll show how I created the photo mask. This requires a picture of the pattern or the ability to create a design and print a copy of it. This picture is then printed onto overhead transparency film or printed onto the film with a standard office copier. I use a laser printer, but I believe ink jet printers work as good or better.

til’ then…



3 comments so far

View Mean_Dean's profile

Mean_Dean

5624 posts in 2964 days


#1 posted 10-29-2016 02:54 AM

Fascinating process!

Looks a little complicated, but I’m looking forward to seeing the process in action. For the photographic process, I was picturing a photo enlarger (which I’ve use before in B&W photography), and those can get kinda pricey.

-- Dean -- "Don't give up the ship -- fight her 'till she sinks!" Capt James Lawrence USN

View splintergroup's profile

splintergroup

1651 posts in 1039 days


#2 posted 10-29-2016 02:18 PM

Dean, A photo enlarger would work, but a bit overkill 8^)

Computers are perfect for this, just scan what ever image you want, then use most any photo, drawing program you want to scale the image to final dimensions. Print to some transparency film and job done.

Copier shops (aka “kinkos”) all have copiers that let you set the scale for the output copies (usually as a percentage of enlargement, i.e. 150%, etc.).

The next post will show going from a scanned image and downloaded JPG, to the final form ready for use.

Thanks for following along!

View CaptainSkully's profile

CaptainSkully

1517 posts in 3375 days


#3 posted 10-30-2016 03:34 PM

I’m dying to use this on a clock face of my own design. I really hoping that you show how to do a relatively detailed piece like a celtic knot or some fancy font. I have a vinyl cutter if that helps.

-- You can't control the wind, but you can trim your sails

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