Instructables

How to make a printed circuit board (PCB) using the UV light LED method.

Picture of How to make a printed circuit board (PCB) using the UV light LED method.
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This instructable shows how to create well done PCB's using Ultraviolet light. It took us about 40 boards before we perfected our PCB, so we will share what worked and what didn't work. All the supplies can be bought from Fry's Electronics, Ace Hardware, Goodwill, Radio Shack, and Ebay . Our PCB tested the Atmel 208 pin PQFP Integrated Circuit (it may not look like it from the poor image quality but there were no shorts between all 208 pins! ).

The materials needed are as follows.

PCB:
-Transparencies (MG chemicals brand http://www.mgchemicals.com/products/416t.html )
-UV Presensitized Copper Clad Boards (MG chemicals brand http://www.mgchemicals.com/products/600.html )
-Laser printer (Brother HL-2070N)
-200 UV LEDs (Bought from Ebay - Asia Engineer, seller giorgio11185. 5mm size, 3.4~3.8 forward voltage, forward current 20 mA, wavelength (nm) 395-400-405, view angle about 25 degrees.)
-200 470 ohm resistors (included with Asia Engineer LEDs bought on ebay. I used 12V for each LED).
-4 Breadboards for LEDs (http://www.radioshack.com/product/index.jsp?productId=2102843 )
-PCB Standoffs (http://www.radioshack.com/product/index.jsp?productId=2102848 )
-Chest/box to house LEDs (Bought at Goodwill. 20 inch length x 12 inch width x 11 inch height)
-Picture frame transparent plastic (Bought at Goodwill)

Chemicals:
-Muriatic Acid (http://www.acehardwaresuperstore.com/transchem-muratic-acid-for-use-in-etching-concrete-p-5243.html )
-Hydrogen Peroxide (http://www.walgreens.com/store/product.jsp?CATID=302248&navAction=jump&navCount=0&nug=VPD&skuid=sku1375525&id=prod1375535 )
-Photoresist Developer (MG chemicals brand http://www.mgchemicals.com/products/418.html )
-Baking Soda (local grocery store. Use if any acid is spilled on your skin)
-Acetone (Ace Hardware)

Tools:
-Soldering Iron (any soldering iron will do, I used http://www.amazon.com/Weller-WESD51-Digital-Soldering-Station/dp/B000ARU9PO/ref=sr_1_1?ie=UTF8&s=hi&qid=1246827601&sr=1-1 )
-Solder (We originally bought Lead free solder. This type of solder did not work. Instead we used Sn63/Pb37, 2.2% Flux, 23 gauge MG Chemical brand)
-Screwdriver
-26 and 16 gauge wire
-Wire stripper
-Gloves (bought at Ace Hardware)
-Goggles (bought at Ace Hardware)
-Power Supply (wall wart or benchtop power supply will do. Make sure your power supply can handle the current the LEDs consume. As you can see from my photo, my voltage was 11.9V and 3.47 Amps were consumed).
-Q-Tips (local grocery store)
-Buckets for chemicals (Ace Hardware)
-Timer
 
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Tomwang2 months ago

Hi

This is Tom from Union Circuits,a professional PCB manufacturer located in Shenzhen,China.

tom(at)unitpcb.com

Tomwang2 months ago

Great invention!!!

baecker034 months ago

you can buy uv smd leds on ebay fairly cheap (guessing 10-20 bucks) just use a collimating lens to create parallel light waves. you would of course want to keep it a distance away.

conoral114 years ago
What mcd rated LEDs are you using?
mcd is a reading of the brightest spot of the LED, not the total output, so it's useless.
Just look for some 20ma LEDs.
2000mcd, 395nm LEDs will suite you just fine
JoeyJunior (author)  conoral114 years ago
I am not sure on the mcd rating of the LEDs.  I bought the LEDs from a seller on ebay, he did not provide the mcd rating.  If you search for "UV LED" in ebay, I purchased the ones for sale by Asia Engineer.
VadimS1 year ago
Looks good, definitely on my to do list.
Glass doesn't block UV in the 400nm range so it's the best bet.
Some plastic does but most should be alright sins 400nm is borderline and is actually in the visible spectrum.
purpulhaze1 year ago
My boards are not far from the leds and they' ve came out ok. Though I am using straw hat leds and I also have a diffused piece of plexi over the top of them. What are you using to cut your boards? I can't get a clean straight edge to save my life.

I also used the acetone a few times but have switched to using a solution of water and 3-5% lye drain cleaner. I just let my boards sit in the solution for a few seconds and they come out shinny and resist free.
cc672 years ago
Is there anyway of doing this method... but instead of using laser printer, use inkjet? I just do have an inexpensive deskjat printer... tnx in advance
f2a4 years ago
I made a UV light box out of a cigar box that turned out great.
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f2a f2a4 years ago
Unfortuantely I haven't tried it out yet. But I used flat top leds with around a 120 degree angle. So you can put the leds really close and make a much smaller box.
agodinhost f2a3 years ago
please, what's the dimensions of this box?
JoeyJunior (author)  f2a4 years ago
Looks awesome! Did you have any troubles with the LEDs being too close to the PCB? You can see a picture of a failed PCB on my last page where the PCB was too close and you can see the holes of the LEDs on the photoresist.
You can solve LED distance problem by puting 2 sheets of tracing paper over LEDs. Paper sheets should be separated 5mm minimum. Two layers of tracing paper will blur UV light, without inerfering with its intensity. That's the way I did it, works good, and I use 20 degree LEDs on 4cm distance.
gulyman3 years ago
I have that exact C++ book. It's a pretty good one.
JoeyJunior (author)  gulyman3 years ago
Haha nice, yup that's how I learned C++.
haze783 years ago
Thanks for the project. Just one advice; LED powering system you're using is rather inefficient, only 29% percent efficiency, you're using 41W to power up 12W worth of LED's. You might consider some circuitry to drive LED's more efficiently, or maybe chain 2 LED's in series at least, this way you could increase efficiency to about 63%. Other more efficient solutions require more complicated and expensive circuitry (like max LED drivers, or constant current circuitry).
JoeyJunior (author)  haze783 years ago
Yup, you're right. The reason I didn't put a couple LEDs in series was because the LEDs came with 470 ohm resistors and I didn't want to buy more resistors. Something like a 5V buck DC/DC converter would be pretty cool to add in the box (something like an LTC3835), maybe I'll make a PCB for one.
ildefonso3 years ago
Hi!

Just one question: why not remove the photoresist from the pads and leave the rest of the tracks covered with the photoresist? I think the photoresist could help protect the copper. What do you think?

JoeyJunior (author)  ildefonso3 years ago
Yeah you could leave the photoresist on the tracks, no problem with that.
Hello, i was wondering what solder paste you use?
JoeyJunior (author)  Pyrotechnic-Robot3 years ago
I didn't use any solder paste. I just hand soldered everything at the end.
Trickynekro3 years ago
You can also remove the photoresist with simple alcohol... ;-)

This can save some trying to find acetone....
Cruwe4 years ago
 What is the pitch of the larger IC footprint?
JoeyJunior (author)  Cruwe4 years ago
It's .5 mm pitch.
Skyriam4 years ago
Is this UV-Light method better for making PCB's? What's the difference to "normal" PCB making?  How is it better? Thanks!
JoeyJunior (author)  Skyriam4 years ago
Yup, it's better.  The differences are:

If you want to produce more than one PCB, this method allows you to make more than on PCB with the same transparency.  The other method (assuming the iron on method), you have to print out a new transparency every time. 

You will be able to accomplish thinner traces by using the UV light method.

The main reason I chose this method was because I tried the iron on method and could not get the ink to stick to the PCB.  Plus I had fun making the lightbox :)
Also, MG chemicals now has negative dry film resist. All you need is a laminater
to put the film on a copper clad board. The resist is exposed with a daylight fluorescent lamp One can do single or double sided boards. The only draw back is you have to work under a yellow or red light  like you would in a dark room.
Ohh I see the light now...  thanks for answering!
Davad Skyriam4 years ago
Way better boards from this method. I thought using LEDs to build an exposure box would be kind of expensive so I went out and bought a fluorescent black light for $15 to do the exposure. An 8 minute exposure time worked great. Plus you can reuse your artwork. 
andreq5 years ago
Hi, I' using the same method to make my own PCB. I didn't have to waste 40 pcb to get good result :) I first did a test pattern ( 5mil to 50 mil lines on a small 1"x6" pcb) to find the best exposure time. You can see it in my gallery. I've attached my third PCB. It's a small i2c digital volume control for an Amp I'm currently building. The only issue I have is that my design is wrong. I grounded a pin that shouldn't be grounded. Anyway it was easy to repair with a small cut and 2 jumper wire. The second picture show a little "too much copper" under the "OUT" wire pad. The text is 3 or 4 mill I think. I'm using Staple Ink jet transparency paper (somewhat textured) and print at 600DPI. Stacking 2 or 3 layers is the key, you will get a perfectly dark (no light pass trough) pattern. Also, do not click "Print in Black only" (or gray scale) in your printer setting, the mix of color ink in the black ink seem to works better at blocking light than black ink only... I use the same mg chemical board with 3:30min exposure time.
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Davad andreq4 years ago
Hi andreq,

How are you doing your green solder mask?
andreq Davad4 years ago
There is no solder mask.

I've only removed the "positive" on the solder pad with a Q-tip imbibed in alcool.

The green part is the developed "positive" film.
JoeyJunior (author)  andreq5 years ago
That's a good idea using 2 or 3 layers so UV light is not allowed through the transparency. I'll have to try that and see what happens. Nice boards!
andreq andreq5 years ago
Furthermore, my first and second PCB where cleaned of all the positive uv resistant material, but I found that only rubbing the solder pad give a nicer "professional" finish and also protect the non soldered traces. As I don't tin my board, I think it's a good idea. That's why this board is part "green" and part "copper"
Skyriam4 years ago
Sorry to bother you again =s.... stupid question: How do you make pcb's out of uv light? Do you need a special copper clad that has a photoresist material?  Thanks joey!!
JoeyJunior (author)  Skyriam4 years ago
Yup, you need a special copper clad that has the photoresist.  I bought these at Fry's Electronics:

http://www.mgchemicals.com/products/600.html
sr1sws5 years ago
Nice job! A somewhat pissy observation, but you could have wired the LEDs as 4 in a series and done away with the resistors. This would have saved some power - at the risk of having a group of 4 go out if one failed. Steve
"at the risk of having a group of 4 go out if one failed" Gotta love LEDs! If one dies, it turns into a jumper. So you end up with 3 in series vs 4. I think you will need to design the circuit with this in mind - if you didn't, then your 3 LEDs may over current and die too. Then your really would lose a set of four. Reminds me of the time I spent with a multimeter and a 150 light chain at Christmas... Back before they put the little jumper resistors in them (the thin wire around the bottom).
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