For those who have never done it (probably not many anyway), for those who want to try a better and cheaper etchant, and for those who click on any thread with pictures (like I do) 
All you need is a laser print or copy of you PCB layout on plain paper. Mirror the print, so the toner has contact with your board. Put some text on you PCB layout to remember which side is up. You need two prints to increase the contrast. One layer of toner often is too transparent.
The next step is making your layout transparent. People are selling expensive chemicals for this, but I tend to prefer veggie oil. I recommend buying (or building) a light box with UV tubes. I got much better and more repeatable results and will never go back. Properly align the two prints, put the PCB on them and light for about five minutes.
Don't expose your eyes to ultraviolet light. I've done it once. Believe me.
After lighting, remove the veggie oil from your PCB (you cannot process it otherwise) and clean you lightbox from the mess you made.
All you need is a laser print or copy of you PCB layout on plain paper. Mirror the print, so the toner has contact with your board. Put some text on you PCB layout to remember which side is up. You need two prints to increase the contrast. One layer of toner often is too transparent.
An externally hosted image should be here but it was not working when we last tested it.
The next step is making your layout transparent. People are selling expensive chemicals for this, but I tend to prefer veggie oil. I recommend buying (or building) a light box with UV tubes. I got much better and more repeatable results and will never go back. Properly align the two prints, put the PCB on them and light for about five minutes.
An externally hosted image should be here but it was not working when we last tested it.
Don't expose your eyes to ultraviolet light. I've done it once. Believe me.
After lighting, remove the veggie oil from your PCB (you cannot process it otherwise) and clean you lightbox from the mess you made.
To develop the board, you need a solution of 10g NaOH in 1 l water. Don't use hot water.
I use a precision weighing machine to prepare the mixture.
NaOH is a hazardous chemical! Wear suitable gloves and eye protection. Avoid contact with skin and seek medical advice when you failed to.
This is how the board looks after developing:
An externally hosted image should be here but it was not working when we last tested it.
I use a precision weighing machine to prepare the mixture.
An externally hosted image should be here but it was not working when we last tested it.
NaOH is a hazardous chemical! Wear suitable gloves and eye protection. Avoid contact with skin and seek medical advice when you failed to.
This is how the board looks after developing:
An externally hosted image should be here but it was not working when we last tested it.
Rinse the board in water. Have a careful look if everything went right. It is the last time to correct little errors. I use a steel needle to remove from, and an etch resistant pen to add to the etch resistant on the board. Write down a series number if you like or sign your boards
I use a special etchant which is water clear, very fast and also cheap! This is what you need:
Hydrochloride acid, fuming, 37%
Hydrogene peroxide solution, 35%
ATTENTION when using these chemicals! Wear protective clothes, eye/face protection and gloves. Both chemicals can cause severe burns. Store them only in suitable bottles and keep them in a cold and dark place. Allow for ventilation. Hydrochloride acid, even when kept in a closed bottle, will corrode metals in the room... Keep away from your valuable tools! When feeling unwell, immediately seek medical advice and show the labels from the bottles. Don't flush these chemicals in the toilet!
I use a special etchant which is water clear, very fast and also cheap! This is what you need:
An externally hosted image should be here but it was not working when we last tested it.
Hydrochloride acid, fuming, 37%
An externally hosted image should be here but it was not working when we last tested it.
Hydrogene peroxide solution, 35%
ATTENTION when using these chemicals! Wear protective clothes, eye/face protection and gloves. Both chemicals can cause severe burns. Store them only in suitable bottles and keep them in a cold and dark place. Allow for ventilation. Hydrochloride acid, even when kept in a closed bottle, will corrode metals in the room... Keep away from your valuable tools! When feeling unwell, immediately seek medical advice and show the labels from the bottles. Don't flush these chemicals in the toilet!
The receipe:
For 1l etchant, mix (in this order!) 770ml hot water, 200ml hydrochloride acid, 30ml hydrogene peroxide.
Here you can see the copper dissolving:
For 1l etchant, mix (in this order!) 770ml hot water, 200ml hydrochloride acid, 30ml hydrogene peroxide.
Here you can see the copper dissolving:
An externally hosted image should be here but it was not working when we last tested it.
Never etch a PCB without proper ventilation, especially when using these chemicals! Don't do this in your living room or the kitchen. If you don't have a workshop, better go outside.
Here's the PCB after stripping the etch resistant with acetone and drilling:
It's a double sided design, but no vias. It belongs to this project.
Here's the PCB after stripping the etch resistant with acetone and drilling:
An externally hosted image should be here but it was not working when we last tested it.
It's a double sided design, but no vias. It belongs to this project.
35% Hydrogen Peroxide is a very powerful oxidizer and not readily purchased by the average DIYr. You can use pharmacy H2O2 by increasing the volume to attain the same molality -- here's my recipe using readily available chemicals:
400ml water
250 ml 31.5% hydrochloric acid (Muriatic Acid)
350 ml 3.0% hydrogen peroxide (Pharmacy Brand)
Wear goggles, don't wear your favorite jeans or shirt! Add acid to water, the reaction is exothermic so be prepared for a rapid rise in temperature. Then add the H2O2, stir.
200 ml of the above solution etched a 4 by 4 inch board in 8 minutes.
You can discard the solution in plenty of running water.
You can also use the hydrogen peroxide from a hair salon -- this is a 7% solution (hmmm, sounds like Sherlock Holmes) In this case adjust the percentages accordingly. H2O2 is available to 91% concentration, but you have to be NASA or the U.S. military to obtain it.
400ml water
250 ml 31.5% hydrochloric acid (Muriatic Acid)
350 ml 3.0% hydrogen peroxide (Pharmacy Brand)
Wear goggles, don't wear your favorite jeans or shirt! Add acid to water, the reaction is exothermic so be prepared for a rapid rise in temperature. Then add the H2O2, stir.
200 ml of the above solution etched a 4 by 4 inch board in 8 minutes.
You can discard the solution in plenty of running water.
You can also use the hydrogen peroxide from a hair salon -- this is a 7% solution (hmmm, sounds like Sherlock Holmes)
In this case adjust the percentages accordingly. H2O2 is available to 91% concentration, but you have to be NASA or the U.S. military to obtain it.OliverD said:
actually, you can do this with "caligene", the name is dutch, i dont know how you call it in english ( somebody ??) , but it is basicly a cleaningprodukt, it cost about 1 euro for 1 liter, and you need about 10cl/liter.
and now the good thing, you can just flush it away trough your sink, thats wat's it made for
Probably "Caligene" mainly consists of NaOH. We have a cleaning product in Germany called "Rohrfrei" which consists of NaOH and aluminium scraps.
NaOH is really cheap to get, the package is the most expensive part of it. However, buying these might be a problem for the typical DIYer as mentioned above. I ordered the chemicals through my gliding club.
NaOH is really cheap to get, the package is the most expensive part of it. However, buying these might be a problem for the typical DIYer as mentioned above. I ordered the chemicals through my gliding club.
Hi OliverD,
That write up with pics was very nice.
But I couldn't understand what you did with the vegetable oil and your reference to " making the print transparent ".
Looks like you missed out that because everyone ( except me ?) knows what is to be done.
I have the prints , the clean board and the veggi oil. What next?
I know the step after that , remove excess veggi oil ( with soap ?). So does one apply the oil to the board ?
The next one would be etching.
Sorry for being dumb.
Thanks,
Ashok.
That write up with pics was very nice.
But I couldn't understand what you did with the vegetable oil and your reference to " making the print transparent ".
Looks like you missed out that because everyone ( except me ?) knows what is to be done.
I have the prints , the clean board and the veggi oil. What next?
I know the step after that , remove excess veggi oil ( with soap ?). So does one apply the oil to the board ?
The next one would be etching.
Sorry for being dumb.
Thanks,
Ashok.
ashok said:
I know it's more expensive than making the paper translucent -- but consider using Avery "Full Page" transparent labels -- these stick right on the photo-resist and are easily to align under "red" illumination. I found that using mylar (or paper) results are difficult to obtain since the mask often does not align 100%
I just use a DeskJet printer with HP standard inkjet transparancies. Print using best quality and have never had a problem even with very thin tracks. They are fairly expensive I suppose, but I put several designs on one sheet to maximise usage, and it's worth paying for the fact that I get perfect results everytime.
why do u people use pcbs....is it because they are easier to poulate than then normal bredboards, bacause you used a computer to design ur stuff.......maybe some other reason...or simply because it looks damn good????
cause right now i only use bredboards at about 1pound70 per 15cm*10cm board...or whatever length t is....are pcbs that much more expensive......how much per board after buying all the other expensive gear ...like the uv box...thats gotta be a *****...huh!??.....
sorry to hijack your thread...
cause right now i only use bredboards at about 1pound70 per 15cm*10cm board...or whatever length t is....are pcbs that much more expensive......how much per board after buying all the other expensive gear ...like the uv box...thats gotta be a *****...huh!??.....
sorry to hijack your thread...
OliverD, great post.
I hope you don't mind me adding a few comments:
Regarding the transparancies: they exist for both inkjet and laser; I've used both with those two types of printers and had very good results.
I also use the same mix as you for the etchant (in fact, I've posted it around here somewhere...), and I've been using it on my diy projects for a long time. But I would not use hot water.
There are developers specifically designed to develop photoresist (see RS, for example). Having worked with both, I can say that a developer, although more expensive, is better than NaOH+H2O because it is less "agressive". With the developer you can leave the board more time in the tub while you wait for all parts of the photoresist to come off. With the NaOH+H2O, if you leave it a bit too much it will remove both the exposed and unexposed bits.
Also, for those that prefer to use photoresist spray instead of pre-sensibilized pcbs, here's my own two cents: the key to a perfect pcb is to dry the photoresist in a perfectly horizontal surface, so it doesn't flow to one side making the layer uneven. If you can, use an hoven at 65deg.celcius for half-hour; thats the best way to do it. That is better than leaving it to dry in room temp because in that case the photoresist will have a longer time to be able to flow before becoming too dry to do so and will almost certainly pick up dust particles. The advange of the spray is that it is cheaper if you're doing more than a few and if you mess up the developing of the pcb you can go back and sensibilize it again. If it's a one-time issue then pre-sensibilized is better, but then I'd say ordering it done might be even better.
J.Guilherme
I hope you don't mind me adding a few comments:
Regarding the transparancies: they exist for both inkjet and laser; I've used both with those two types of printers and had very good results.
I also use the same mix as you for the etchant (in fact, I've posted it around here somewhere...), and I've been using it on my diy projects for a long time. But I would not use hot water.
There are developers specifically designed to develop photoresist (see RS, for example). Having worked with both, I can say that a developer, although more expensive, is better than NaOH+H2O because it is less "agressive". With the developer you can leave the board more time in the tub while you wait for all parts of the photoresist to come off. With the NaOH+H2O, if you leave it a bit too much it will remove both the exposed and unexposed bits.
Also, for those that prefer to use photoresist spray instead of pre-sensibilized pcbs, here's my own two cents: the key to a perfect pcb is to dry the photoresist in a perfectly horizontal surface, so it doesn't flow to one side making the layer uneven. If you can, use an hoven at 65deg.celcius for half-hour; thats the best way to do it. That is better than leaving it to dry in room temp because in that case the photoresist will have a longer time to be able to flow before becoming too dry to do so and will almost certainly pick up dust particles. The advange of the spray is that it is cheaper if you're doing more than a few and if you mess up the developing of the pcb you can go back and sensibilize it again. If it's a one-time issue then pre-sensibilized is better, but then I'd say ordering it done might be even better.
J.Guilherme
Hi J.Guilherme,
I tried transparancies for laser printers, but my HP Laserjet 4 plus simply doesn't produce enough toner density - even with all settings maxed and a brand-new cartridge. Always have to use two layers...
I also use photoresist spray and I'm getting very good results. A dust-free environment and an oven is essential, though.
I tried transparancies for laser printers, but my HP Laserjet 4 plus simply doesn't produce enough toner density - even with all settings maxed and a brand-new cartridge. Always have to use two layers...
I also use photoresist spray and I'm getting very good results. A dust-free environment and an oven is essential, though.
This is what I got using a laser printer on transparency film with max contrast and full darkness :
A zoom on tiny tracks - board completed :
An externally hosted image should be here but it was not working when we last tested it.
A zoom on tiny tracks - board completed :
An externally hosted image should be here but it was not working when we last tested it.
For anyone that etches their own boards as I have many times you will find the etching time greatly reduced if the board is floated copper down in the etchant. When done in this fashion the copper that is being dissolved will fall away from the board to the bottom of the tray due to its weight. This way the bare copper always has fresh full-strength etchant working away at it. Using this method with feric chloride etchant I've been able to cut the average etching time in half. But this should work just as good with any etching solution.
Mark
Mark
even easier
I tried this and it worked quite well: 200 mL of 3% hydrogen peroxide (the pharmacy grade) and 100 mL of 31.5% hydrochloric acid -- aka "Muriatic Acid" . Use once and throw away with plenty of water -- and I mean plenty of water !!!
the Muriatic Acid "fumes" so it's best mixed outdoors.
I tried this and it worked quite well: 200 mL of 3% hydrogen peroxide (the pharmacy grade) and 100 mL of 31.5% hydrochloric acid -- aka "Muriatic Acid" . Use once and throw away with plenty of water -- and I mean plenty of water !!!
the Muriatic Acid "fumes" so it's best mixed outdoors.
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