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PhotoEtching PCBs using XGA laptop display not Transparency

 
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guru



Joined: 03 Jan 2006
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Location: St Pete Beach, FL

PostPosted: Mon Jul 16, 2007 9:45 pm    Post subject: PhotoEtching PCBs using XGA laptop display not Transparency Reply with quote

Hey all,

I was at Radio Shack (Sh#$ Shack) and had a thought:

Could an old laptop and it's dismantled display be used as the UV mask to etch circuit boards? If you have ever taken apart an LCD display you would see that it still works with it's backlight removed. I once did this and help it up to the sun...it's a cool effect as your laptop display is now transparent.

The question would be: (a) Is the LCD black enough to block the UV light without leakage? (Hight COntrast Display matybe) (b) Resolution sufficient enough? Perhaps focusing the UV light and mask via lens would shrink the display area and increase resolution.

I don't like using Photocopied transparencies. I find the tonor leaks too much UV light and makes poor traces. In the past I used a Litho(graph) company to make a litho of my mask. Litho's are used for printing presses. This created perfect UV masks that didnt leak AT ALL! I could keep the IV light on for a day and still have perfect traces. It was also wasnt expensive to produce the litho.

It would be neat to just load a image of the board and flash the UV light. I see buying an old laptop and hacking a new enclosure minus the keyboard/etc and having it networked. It's probably overkill when the litho works so well.

C
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ginge
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PostPosted: Tue Jul 17, 2007 12:07 pm    Post subject: Reply with quote

Colin,

An interesting idea.... I have a stripped LCD sitting right next to me that was intended for a projector conversion. I will give this a go in a couple of hours (when the hangover has settled) and we will see what happens.
Hopefully the LCD layers do not block UV.

B
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guru



Joined: 03 Jan 2006
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PostPosted: Tue Jul 17, 2007 12:46 pm    Post subject: Reply with quote

Hah! Awesome! Can't wait to hear your results!

Tomato Juice works well for hangovers...even better if you take some the night before. We have a thing in Canada called Clamato Juice...tomatos and clams! Nice! Wink

They don't seem to carry the stuff in Florida.

btw: I did some calculations on the widths of displays in mils.
1900x1200....7.6mil x 5 mil
1680x1050....8.6mil x 5.7 mil

I wonder if the thickness of the LCD glass could cause some leakage as the lcd "blackness" would not be flush with the copper.
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ginge
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PostPosted: Tue Jul 17, 2007 2:31 pm    Post subject: Reply with quote

The screen I have is nowhere in that resolution region, but but does have a black filter on the front. I dont know exactly what these are called. They are fairly new to tft screens and give that shiny high contrast look. Anyhoo, I digress.

The setup:-
I have a small uv exposure box which I have placed the TFT on top of. The glass on the exposure box is flush with the enclosure, so the screen is flat.



Preliminary results:-
As you can see, the image is not too bad, I can still see a lot of the UV coming through the black regions, though.
The first board I exposed from the box had a very fuzzy faint image on it that was close the the test pattern. The second exposure was a complete washout. Far too much UV bleeds through the layers, making it difficult to get a sharp image.

Also I noted something odd happening with the LCD when placed on the UV The horizontal lines of the LCD screen are shimmering slightly. You can only see this under the UV light, and I think it may be contributing to the problem somewhat. I have attached a vid so you can see what I mean.

UV horizontal shimmering (about 1MB) AVI

I have a few more things I am going to try before I call this one busted, but at the moment I am erring on the side of too much UV bleeding.

Any ideas to sharpen this up? I will get some pictures up when i get another satisfactory exposure.

Another idea struck me that is probably way beyond my patience level, and that is to use my Over Head Projector to shrink the image onto the top mirror. The PCB would be situated on that mirror. That would need a high powered UV lamp, and I don't have one.

Barry
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guru



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PostPosted: Wed Jul 18, 2007 2:48 am    Post subject: Reply with quote

I have been reading more on display manufacturing. UV light is used to cure the sealeant between the glass panes. UV light also seems to slowly damage the plastic components of LCDs over a period of time.

I am not suprised the lcd leaked a lot. I figured this would be the showstopper if anything at all. What was the contrast ratio on your display? A high contrast I think would be best, but I doubt you could get it high enough after hearing your results.

Great work though! I didnt expect someone would actually try it so quickly!

What do you use normally to develop your boards?

Colin

ginge wrote:

Also I noted something odd happening with the LCD when placed on the UV The horizontal lines of the LCD screen are shimmering slightly. You can only see this under the UV light, and I think it may be contributing to the problem somewhat. I have attached a vid so you can see what I mean.
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ginge
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PostPosted: Wed Jul 18, 2007 9:21 am    Post subject: Reply with quote

Ouch. Luckily the UV didn't damage my screen!

This is the screen I used...
http://www.ebuyer.com/UK/product/126874/rb/0

It has a 500:1 ratio and res of 1440x900.

I don't think I could have done any more to try and get it working. I actually got better results without the glare filter on, but even then the bleedthrough was too high.

I can't run any more experiments now as I am out of photoresist and developer (Electrolube PDN to answer your above question). I would say it's impossible Sad

Quote:
What do you use normally to develop your boards?

I will expand upon what I put previously...
Until recently I used tranparency on a laser printer, until I discovered this direct to PCB method:-

http://techref.massmind.org/techref/pcb/etch/directinkjetresist.htm

I used a HP printer to do the dirty deed, and also used a heating plate to dry the ink on contact with the PCB. It works a million times better than any other homebrew method I have tried. I have succesfully etched TSSOP and high density Maxim micro pitch components. (you know the type)

Barry
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Last edited by ginge on Wed Jul 18, 2007 6:14 pm; edited 1 time in total
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ginge
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PostPosted: Wed Jul 18, 2007 5:57 pm    Post subject: Reply with quote

I just found some Clamato in my local speciality foods store! I honestly thought you were joking, but no!

I was imagining something far more fishy, but it was actually quite sweet.
I am not entirely sure if I like the stuff or not... it's... um... different
Most definitely too bizarre and interesting for the British taste buds Wink

I could only them in a 6 pack, so I guess I have time to get acquired with it's distinctive flavour.

According to the shop keep, the stuff is popular in the south Americas... That is a lot closer to you than it is me, so you should have no problem sourcing some Clamato. Wink
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PostPosted: Thu Jul 19, 2007 12:37 am    Post subject: Reply with quote

I dont like clams but I like clamato juice --- though its not my favorite drink. It's used in Canada in a drink called a Caesar but bartenders looked at me strange when I asked down here so I stopped asking and just said, "...a beer." Clamato Juice, Vodka, Pepper/spices...like a bloody mary. The glass is also rimmed in a celery salt and spices mix and garnished with a stick of celery. That is how I acclimated myself to the clamato juice. Then I found out that if I drink 2 or 3 Caesars at the end of the night I wouldnt get a hangover no matter how much beer I drank. All the salt and vitamins restore your electrolights I guess.

As for direct pcb printing I gotta make myself one of those. I have an Epson C42UX on the desk that I dont use. I think it's going to be ravaged in a few minutes!

C
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PostPosted: Mon Jul 30, 2007 6:53 pm    Post subject: PCB Throughplating Reply with quote

Ginge,

Take a look at this page with the homebrew electro thru-plating. It shows a single picture about halfway down with a brief explanation but the link is bad. I emailed the guy but expect my message will get returned.

http://www.makezine.com/blog/archive/electronics/85.html

I wonder how he is doing it.

Also, I got my hands on a bad Epson C84 for Direct PCB Etching. The head is very clogged and I am trying to clear it. It has depleted the black cartridge so I made a cartridge chip resetter but all it does is erase the chip making it completed non-functional. Maybe I can fetch a buck for my trouble by selling it on Ebay as an "Epson Chip Eraser"!!! I have decided to get a continuous flow system instead.

I also converted a CD-ROM enclosure to an XY table! Replaced the tray eject motor with a stepper, and added at two "goal posts" to the side of the enclosure and mouted another stepper for the Y axis. Also did a Z axis using the goal posts. It should be large enough to drill the pcbs I want. I could post a picture if anyone is interested. I could also use this to mount a laser and aperture disc to expose a sensitized pcb if my epson trick doesnt work out.

Off to Canada for a month so I wont be able to work on this until I get back.

C
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ginge
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PostPosted: Mon Jul 30, 2007 7:04 pm    Post subject: Reply with quote

Colin,

I like it! It is a real shame about that bad link, but I pulled this out of archive.org
http://web.archive.org/web/20070428105437/http://www.myhome.ch/mzingg/pcbstuff/tps/
Seems to be intact. Very very good find.

Quote:
I also converted a CD-ROM enclosure to an XY table!


Great! I considered using the CD-ROM tray in my inkjet to print onto the PCB, but your idea sounds better. Yes, I would love to see a pic!

Quote:

Off to Canada for a month so I wont be able to work on this until I get back.

Damn. I am really looking forward to seeing what you come up with!

Have a good break.

Barry
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PostPosted: Mon Jul 30, 2007 8:22 pm    Post subject: Reply with quote

The website linked to is high on pictures of the equipment, but low on chemistry details. A quick google let me to this lot:

http://www.thinktink.com/stack/volumes/volvi/copplate.htm
http://yarchive.net/metal/through_hole_plating.html

It would seem to be a fairly trivial task, but as that last link suggests, Murphys law applies at each stage of the process.

There is surely a market for prototype PCB's as low low prices, I just can't get them. The last PCB run I did cost me nearly $7/board in very low quantity, and I made quite a few mistakes in the layout too.

There has to be an easier way :/
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PostPosted: Wed Aug 11, 2010 3:02 am    Post subject: ss Reply with quote

There are always so many problems occuring when we import avi to imovie and try to play. The videos may have only picture or only sound, or even nothing at all. That is because imovie can only read the avi which has been compressed with the codecs that imovie understands. convert avi to imovie when we need to play and edit AVI files to iMovie on Mac OS X. avi to imovie converter is not only a converter but also a video editor for Mac. You can do video trim and video crop etc.
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