Introduction: Dry Film Photopolymer for Making Circuit Boards

I was reading on different web pages what could be the better way on doing a printed circuit.
I tried presensitize board with great success, The first time I used one the circuit came out pretty good, the second time I tried to
use a double sided presensitze board but it never worked. I was wondering what I did different from the first time but after a few tries I realized that the board was simply bad. A useless board that maybe later I will use it with the toner transfer method.
The resolution is good and is fast. But what happen if you detect a failure on your circuit after you develop it?  Well, the clad is useless, you have to remove the green stuff and use the toner transfer method.

I tried the toner transfer method later with some limited results.  Nobody knows which one is the magic paper that works 100% all the time and you have to have a laser printer. I even tried one magic paper from one web page that I found, I bought the paper with some other stuff they recommended and it didn't work the way I was expecting, I have always have to retouch the traces. I like to have a big ground path around the traces. I do it this way because the routing tool easily connect the ground lines and the etching is fast because the solution doesn't have to eat too much copper.

The problem with the  toner transfer method is that it never covers completely the big ground path and It always came out with a porous ground line after etching the board and then later you have to remove the toner that is nothing easy leaving my copper with a dirty rusted aspect. I also bought the laminator they suggested and it was kind of expensive (86 bucks).

So after the success with the dry film solder mask I decided to try the dry film photopolymer to do my circuits.  It worked fantastic. you don't even need a UV light and by the way I don't recommend using one, is too strong!!!. A conventional 15 watt florescent light  is better because it doesn't burn the paper and you will attain near 40 micrometers of resolution.

You can get the paper on ebay at this address

http://www.ebay.com/itm/Photosensitive-dry-film-photopolymer-10-sheets-of-9-75-x-8-inches-/271041805484?pt=LH_DefaultDomain_0&hash=item3f1b59bcac

The materials are:

Dry film photo polymer
Laminator or Iron.
Sodium Carbonate better know as soda ash
Sodium Hydroxide better know as caustic soda or Lye.
Your preferred etching solution.
And the negative of your art work printed on a transparency.









Step 1: Procedure

1.- First you need to cut your board the size of your art work.
The film has two protective film layers, remove one layer with the help of two tapes. Then put the tacky suface over the copper clad and pass it through the laminator.  Avoid wrinkles and bubbles between the paper and the copper clad.

2.- Expose the film to the light. I use a conventional florescent light 15 watt during 15 minutes. Remember that you have to use the negative of your art work like in the picture. The paper is green without been exposed and it will become blue when is already exposed. The first photo looks purpule because I leave it standing around one day before etching. The color should be more like the second photo.
I tired an UV light but it is too strong for the paper. It turned the paper's color to dark purpule and the paper became brittle. Not good.


3.- Once exposed remove the second protectic layer and develop the copper with the sodium carbonate solution.  You have to use 0.85% sodium carbonate concentration, that means that you have to put 0.85 grams of sodium cabonate on a liter of water.

4.-  Etch the board with a fresh etching solution. Use a fresh etching solution to cut down the etching time.

5.- Once the board is etched we need to prepare a solution of 2-5% of sodium hidroxyde. 
Caution: if you are using sodium hidroxyde crystals pour the water slowly and in a ventilated area. The solution will generate heat and will expel fumes. Use gloves .
Put the board in the solution and wait util the paper becomes transparent, remove the board from the solution with the help of some plastic pliers or something similar.
Rinse the board with water and the paper will start to peel off.

Now all you need is to apply the dry film solder mask already explained in another instructable, put your components and you will end up with a board like the one in the last photo.


Comments

author
roliop (author)2014-12-24

Encouraging article !

Bit confused about the concentration of sodium carbonate...

0.85% of 1000g water = 8.5g, not the 0.85g mentioned

Other articles mention around 10g.

rp

author
JohnathanW15 (author)roliop2017-08-04

it depends on the data sheet for the film u buy and sometimes varies with what resolution you aim for. The blue to purple stuff that is easy to get on Amazon and ebay at the moment is what he appears to have used. I'm using it Untill the harder to source replacement arrives and if that doesn't go well I'll bite the bullet and get real riston. Anyway. 0.85 to 1 percent at about 100f for no more than 60 seconds before rinse is how u want to do the blue stuff. Google solid dilution in water formula to figure out the math. You need to clean your board b4 applying. I use 3 baths and green scrubbers for dishes(but not already used on dishes). 1) 5 percent hcl bath to scrub off oxides and make it all shiny. 2 acetone 3iso pro. With rinse between. Use distilled water for rinsing and baths. Always handle board through thin disposal able gloves. Touch your face? Change that glove. The oils on your hands will prevent adhesion of film. Now have a Tupperwear of distilled by laminator drop in prepped board. Cut resist film little bigger than needed. Pull off protective bottom float the sheet over board. With gloved fingers pull board up into film/out of water. This prevents air bubbles from causing issue. Turn laminator on at some point in between. I like it less than full temp for the first pass so the water is pushed out with out boiling. Once exposed my last tip is You are gonna want to lightly brush at it with tooth brush while in dev bath. Take the 60s seriously for that film. Too long it all crumbles. You will start to see blue hairs bits floating and stuck to board. Rinse after 60 sec... Pat dry and let sit for a few min. Now check it's gone where it should be... Touch up by dipping a touch brush in dev and rinsing so as not to over dev

author
tardishead (author)2014-05-19

what laminator did you use with this resist? Did you have to modify it at all?

author
bowlofpudding (author)2013-09-22

i bought this stuff and i give it a 7 out of 10 for difficulty to use, 10 being most difficult. the picture shows the artwork with the traces black, my experience is opposite of this. i had to print where i DIDNT want the copper to be black. any part of the film that is exposed to uv light will harden and resist etching, so expose any part you want to have copper to uv light and it will resist the etchant. i would also recommend holding the film away from the board as put the board through the laminator. this will let the laminator push the film down in an even way, reducing bubbles and wrinkles. my laserjet printer wasnt printing dark enough to keep the uv off the parts i didnt want exposed so i printed 2 transparencys of the same image and layed them on top of each other, this doubled the darkness, however ive read there are products that will darken the toner. this method of etching takes some patience and practice so i reccomend attempting smaller, simple boards before going on to larger complex boards if its your first time using this. i would normally use the toner transfer method but i wanted something with more consistancy, and smaller traces, and im finding this more difficult with this method, but im sure after a few tries itll be better. ive also been using the dry film solder resist which i highly recommend. its very easy to use, makes your boards look better, and protects the copper. this is all my advice from my own experience, your mileage may very. i hope everyone finds this helpful

author
offtherails2010 (author)2012-10-09

Hey thanks for being back in-stock with this stuff, ive been waiting for it lol !!!

Also, just a suggestion, there's a way to do the toner-transfer method without all the bother and fuss with SOAKING OR with IRONING !!! !!! !!!

Yup - you heard right lol !

NO SOAK 
NO IRONING
lol !

Here's the instructable made by a good chap, dustinandrews, here's his 'ible:

NO SOAK Toner Transfer Method !

Its Sooooo-Cool !

Using a Laminator for the heat-Source - A Nice Even-Heating of the board with perfect guaranteed results - PERFECT everytime !

And baking parchment paper for the toner-transfer medium !

Ive long since thrown-out (ahem, recycled lol) the HUGE stacks of magazine paper, NEVER again will i collect any of that anymore !

IMHO its the best idea since sliced bread (and BTW so is this instructable and the Photopolymer Film, lol x 2 !!!)

Give it a try !

author
iurius (author)2012-09-11

Well, regarding the toner transfer method, I believe you haven't done everything right. The most important about toner method is to get the board REALLY hot. That means you shouldn't place the board on a cold surface for ironing, instead you should lay it on a piece of wood or on a stack of (news)papers about 5 (2 inch) cm thick such that it insulates well from cold surfaces. In such a way you will get the highest temperature on board. Also, do not raise the iron too many times over the plate, be patient, press the iron on board, as long time as possible. The toner printed paper should get yellowish - that means the temperature was high enough for the toner to melt and stick.
I've had great result even with plain printer paper. Even better results I got with slightly thicker paper from glossy magazines (really!). Just try it and be patient!
Regards!

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