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HELP with making pcb??


roboticsound
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Hi all,

not astronomy related but maybe someone can help me. I am trying to make a pcb for an electronics project I'm working on. Now I have made some before using the toner transfer method but since where I am now I don't have a laser printer (or an iron!) I thought that I would use the photoresist method.

However I can't seem to get it to work and I'm sick of wasting boards. The first couple didn't seem to develop properly so I then left them under the light longer. Then when I tried to etch one of them I had to leave it in for 2 hours!!! and then some parts had over etched but some parts still hadn't even come off.

I can post pics if anyone wants but if anyone can help or give me some advice it would be much appreciated.

Thanks,

Louis

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Hi, I have been doing electronics for years now and I miserably failed to make pcbs with the photo etch method. I think the copper oxidises too much before I get the thing sprayed with the resist.

I use the toner/iron-on method.

Is there a print shop near you that you could get access to a lazer printer or pop into a local library or office and beg use of the printer.

Failing that, if you can manage to sort the resist ok, warm the ferric up and place the board copper face down so as it etches the particles fall to the bottom.

I have no idea about the iron, perhaps a kindly neighbour!

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Hey thanks,

I was thinking about going to a printers only what paper do you use since I am not sure if they will be happy with me asking them to use magazine paper :)

Also I read that ferric works better if heated up but I'm using hydrochloric acid + hydrogen peroxide. Do you know if this applies to that as well?

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I've made dozens of boards and the most successful method was using photosensitive board, acetates printed from the layout (often doubled up to get a good density), and a UV light box. Used the recommended developer at room temp, and always warmed up the Ferric Chloride (in a spare microwave). From cutting out the right size of board to finished product was never more than hour. If you use the FeCl in a glass dish over a steaming pan you'll find it almost impossible to remove the crust it leaves behind.

David

Edit - most chemicals 'work' quicker when heated up

Edited by dlp
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Yeah this is more or less exactly how I'm doing it though I don't have a light box just using some lamps. How long does it take you to develop the boards I am wondering if I am not developing them for long enough.

I see that most guides and the instructions that come with the boards say that it should only take about 5 mins but I am leaving them quite a bit longer and I am not convinced that the copper is well enough exposed, this might also explain why it was taking so long in the acid.

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I don't think ordinary lamps will work (if they are ordinary). Some people use sunlight, but I've no idea on exposure time. Once you've exposed you should see green tracks on the pcb. I have a large lightbox with about 4 tubes and it takes 30s-1min to expose (that's very quick), then just about 10-20s in developer watching carefully that the tracks aren't coming off. I always held the edges of the pcb and swooshed it about in the dev. Leave it in too long and you won't have any tracks left!

Hope this helps, but will probably just add to your frustration. I'm out changing oil on the car - I'd swap you anyday. Mmm the smell of FeCl....

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Hi Louis.

Good advice from everyone, provided you are happy to persevere with the 'bucket chemistry. Of course that isn't the end of it. There is drilling. Then the aggravation of tinning for soldering.

I have worked in electronics for longer than I care to remember and as a hobby before that. I have made boards hobby wise using model paint or marker pen on plain board, as well as photo-resist boards from artwork. Then when I started work, we tried the same. The results were inconsistent and often poor. Hairline breaks from artwork defects or handling, over etch, under etch leaving whiskers. The list just went on. Certainly nothing we protoyped could go into a saleable product.

Many years ago we realised that the cost of getting protoype or small quantities, from the right manufacturer, was not high. Simply send an artwork (electronic form now or film) and you get a fully finished, drilled and tinned board back quite soon. No aggravation with registration on double sided. Pay a bit more and you can even have a solder resist and silk screen ident!

There are plenty of 'bottom end' PCB manufacturers struggling for work who will be happy to take on low volume work. Have a wander through yellow pages, web search, etc.

A free PCB that fails in the middle of a clear night is worth less than you paid for it!

Hope this helps,

David.

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You need to have nicely cleaned copper laminate rinsed in demin water and dried, and the photo resist will need a good UV light to print the image cleanly, making sure the artworks are clean and voids spotted in and they need to be in good contact with the resist before exposure.

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I use Press N Peel Blue, Once printed with lazer and ironed on pcb you get a high quality circuit that comes out perfect every time. Even if you forget and leave it in the FECL too long it doesn't seem to matter much.

http://cgi.ebay.co.uk/Press-n-Peel-Blue-PCB-Transfer-Film-FIVE-sheet-pack-/120651791925

Edited by astromerlin
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Well just an update I gave up on using the photoresist method and went back to toner. I got some glossy paper and found a guy at my local print shop who was understanding of what I need.

The boards have come out perfect and using a slightly different mix of etching solution the boards were etched in about 30 seconds. Seriously!!

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