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- May 2, 2013
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Ok. So, I have found a cheap source for the negative acting (what we want for stencils) photopolymer film used in the PCB etching industry. We want negative acting, as the converse wastes ink trying to make a transparency. This stuff can be used on a very thin substrate or directly on the knife. Directly applied to the steel it makes for a very clean image as you will see below.
So, this is the film. Simple stuff, a sheet of photopolymer between two sheets of clear film. This stuff is thinner than thin...
For this demo I am just using a piece of hardened 4130, unidirectional finish at about 600 grit.
The film, as stated before, is trapped between two clear film layers. To apply the film to a surface we need to remove the clear film from one side. I use the old tint installer trick of taking a piece of masking tape and applying it to both sides of the film. Then pulling in opposing directions. This may begin to remove the clear from both sides, and if it does just use a finger to direct only one side to release.
Then simply apply the uncovered side of the film to the workpiece. The good thing about this stuff is that it can be worked with under any light that doesn't bear heavy UV. I have used it under CFL lighting and not had any issues.
This is the image I am using for this etch. I wanted to really push this stuff so I chose a cursive logo, about 6pt font, with very light details.
We then want to expose the film with the positive logo on top, just like before. For this stuff, same is true, place a piece of glass on top to get it all as flat as possible. Any light bearing good UV output will work, the sun is a great one... Or, I have since found the best (quickest) results using a dedicated UV source... Any very bright LED if is in the blue end of the light spectrum will work, but a black light is better. Even better than that is a UV light in the nearly non-visible spectrum. I have a 400nm light that works very well...
After the exposure, you will be able to see where the film has changed slightly. Now remove the other layer of clear film from the photopolymer from the mask.
With the film you need both a developer and a remover. The developer can either be a premixed type in a bottle, or dry that is mixed with water. I chose dry, as you can mix as needed. It mixes in my case at a 100:1 ratio water to powder. And as always, I use distilled water to avoid contaminants.
Then dunk the whole shebang into the developer.
After the developer, dry the mask. Then dunk in the remover, and same thing, wipe away (a light touch but a little scrubbing is necessary to remove the non-exposed film). You will be left with a perfect mask for your etch.
Then just fire up your etcher and etch away. This type of mask holds up very well to higher voltages if your unit happens to be built off a 24v transformer or the like. I have tried an etch with just an old phone charger, all the way up to my etching machine. So far this masking technique works well with them all. In this example, I did two etching cycles of about 15 seconds each, and one mark for about 10 seconds.
http://media-cache-ak0.pinimg.com/736x/e8/67/2c/e8672ca11a0c8e3e7dd77d3b70b4842f.jpg]/IMG]
Then just wipe away the mask with some acetone.
[IMG]http://media-cache-ec0.pinimg.com/736x/0b/1a/db/0b/1a/db/0b1adb3cf103a9ab6d6a9df034210ea2.jpg
After a brief wipe down with acetone, and a brush with 0000 steel wool, this is what you are left with. Pencil for scale.
This gives you a good idea of the depth of the image.
And an idea of how it compares to the original...
So far, for one offs this is the best outcome. Nothing will top the professional stencils for multiple etchings, but for a one off on a piece, this seems hard to beat. The price would break down to absolute pennies for this method. I do the same logo for my maker logo on almost everything, but have been looking for something like this as I would like to put the 'Overmountain' brand on things from time to time, and want the font to fit the rest of the design. This means either ordering a sheet of pro stencils with many fonts, or using something like this.
I have a very thin plastic based mesh substrate (micron level filter media) that I got from a friend. I am trying to see how well this stuff sticks to the media, and how many etchings I can subsequently get out of that.
The film, plus developer and remover is sold in kit format for etching PCB's on several different sites, as well as eBay. The price is fairly low even in those places, but the best price breakdown comes from buying this stuff in bulk. I think my roll here is about 3'x100', and the developer and remover chemicals are about 2 pounds each in plastic laboratory type bottles... I am yet to see how long the mixed up developer and remover I have will last on the shelf and after multiple uses... I will also see about parting with some of this stuff, and for what price in the near future if there is much of an interest. Until then, if you want to give this a try, the stuff is available by simply searching for 'PCB etching film,' or 'photopolymer film,' or simply 'photoresist film.'
-Eric
So, this is the film. Simple stuff, a sheet of photopolymer between two sheets of clear film. This stuff is thinner than thin...
For this demo I am just using a piece of hardened 4130, unidirectional finish at about 600 grit.
The film, as stated before, is trapped between two clear film layers. To apply the film to a surface we need to remove the clear film from one side. I use the old tint installer trick of taking a piece of masking tape and applying it to both sides of the film. Then pulling in opposing directions. This may begin to remove the clear from both sides, and if it does just use a finger to direct only one side to release.
Then simply apply the uncovered side of the film to the workpiece. The good thing about this stuff is that it can be worked with under any light that doesn't bear heavy UV. I have used it under CFL lighting and not had any issues.
This is the image I am using for this etch. I wanted to really push this stuff so I chose a cursive logo, about 6pt font, with very light details.
We then want to expose the film with the positive logo on top, just like before. For this stuff, same is true, place a piece of glass on top to get it all as flat as possible. Any light bearing good UV output will work, the sun is a great one... Or, I have since found the best (quickest) results using a dedicated UV source... Any very bright LED if is in the blue end of the light spectrum will work, but a black light is better. Even better than that is a UV light in the nearly non-visible spectrum. I have a 400nm light that works very well...
After the exposure, you will be able to see where the film has changed slightly. Now remove the other layer of clear film from the photopolymer from the mask.
With the film you need both a developer and a remover. The developer can either be a premixed type in a bottle, or dry that is mixed with water. I chose dry, as you can mix as needed. It mixes in my case at a 100:1 ratio water to powder. And as always, I use distilled water to avoid contaminants.
Then dunk the whole shebang into the developer.
After the developer, dry the mask. Then dunk in the remover, and same thing, wipe away (a light touch but a little scrubbing is necessary to remove the non-exposed film). You will be left with a perfect mask for your etch.
Then just fire up your etcher and etch away. This type of mask holds up very well to higher voltages if your unit happens to be built off a 24v transformer or the like. I have tried an etch with just an old phone charger, all the way up to my etching machine. So far this masking technique works well with them all. In this example, I did two etching cycles of about 15 seconds each, and one mark for about 10 seconds.
http://media-cache-ak0.pinimg.com/736x/e8/67/2c/e8672ca11a0c8e3e7dd77d3b70b4842f.jpg]/IMG]
Then just wipe away the mask with some acetone.
[IMG]http://media-cache-ec0.pinimg.com/736x/0b/1a/db/0b/1a/db/0b1adb3cf103a9ab6d6a9df034210ea2.jpg
After a brief wipe down with acetone, and a brush with 0000 steel wool, this is what you are left with. Pencil for scale.
This gives you a good idea of the depth of the image.
And an idea of how it compares to the original...
So far, for one offs this is the best outcome. Nothing will top the professional stencils for multiple etchings, but for a one off on a piece, this seems hard to beat. The price would break down to absolute pennies for this method. I do the same logo for my maker logo on almost everything, but have been looking for something like this as I would like to put the 'Overmountain' brand on things from time to time, and want the font to fit the rest of the design. This means either ordering a sheet of pro stencils with many fonts, or using something like this.
I have a very thin plastic based mesh substrate (micron level filter media) that I got from a friend. I am trying to see how well this stuff sticks to the media, and how many etchings I can subsequently get out of that.
The film, plus developer and remover is sold in kit format for etching PCB's on several different sites, as well as eBay. The price is fairly low even in those places, but the best price breakdown comes from buying this stuff in bulk. I think my roll here is about 3'x100', and the developer and remover chemicals are about 2 pounds each in plastic laboratory type bottles... I am yet to see how long the mixed up developer and remover I have will last on the shelf and after multiple uses... I will also see about parting with some of this stuff, and for what price in the near future if there is much of an interest. Until then, if you want to give this a try, the stuff is available by simply searching for 'PCB etching film,' or 'photopolymer film,' or simply 'photoresist film.'
-Eric
