phototransfer questions

[zachtheterrible]

I've been having this problem every once in a while and am wondering what I'm doing wrong:
When i put my circuit in the developer solution, one part of the circuit will develop much faster than the otehr part of the circuit, leading to that part's tracks disappearing.

Other question: How do you guys cut the board? Whenever I use shears, it ends up cracking parts of the pre-sensitize solution.

 

[Russlk]

I cut my PC boards using a metal cutting fiber wheel on my table saw. You could no doubt use a bandsaw with metal cutting blade also.

 

[Joel Rainville]

I cut on the table saw using a carbide tipped blade, or with a small scrollsaw for tiny boards.

I never used the photoresist method of making PCBs...

 

[justDIY]

I use a 'suicide saw' setup

**broken link removed**

basiclly it is a jigsaw / sabersaw clamped upside down in a vice, with some rope tied around the switch so it's constantly on - use a multistrip to turn it on and off

I use a sheetmetal / composite type blade... hard metal type blades teeth are too fine and ruin too quickly, wood cutting blades have too few / large teeth and cut really hard and rough ... the composite / sheetmetal blade is kinda inbetween and works very well.

note the packs of fresh blades - change blades often to avoid excessive pressure required to feed pcb into blade

note the safety glasses - don't even think of trying this setup without them

note the pile of cut-up pcbs above the saw - only takes a few min.

 

[justDIY]

oh, regarding your developing

you need to keep your developer fluid constantly agitated, that is always moving and mixing and sloshing around ... otherwise it will burn parts of your board before other parts are clear - use a cheap foam paintbrush to stir your developer continously until your pcb is clear - don't stop stiring for any reason.

also, I usually keep the developer tray in the same darkroom as the exposer setup, so I can slip the board into the developer before turning the lights on... I don't know if this really makes a difference or not, but it would ruin a photographic print, so, it might not be good to expose the pcb to any unnessecary light.

underexposure or your postive lifting off the pcb can cause tracks to fade ... use a heavy piece of 1/4" plate glass to weigh your postive down flat onto the pcb, and if you're using the recommened 15w fluorescent light, expose for at least nine min. ... better to have the light a little higher than the instructions suggest and expose for a few more min then to have a faded board.

oh, any holes or faded spots you have in your board after the cold rinse, you can repair with a plain 'ol black sharpie ... it is the weirdest thing that a fine fine layer of sharpie ink can resist the etchant... better than the green photoresist infact.

one last thing I found when I made ten 4x6 pcbs over labor day ... make your postive with as much 'black' areas as possible ... whether they are ground planes or just unconnected pours, the more copper you cover with resist means the faster your exposed board with etch and the longer your etchant will last. if you are exposing multiple board designs onto a single pcb (panelizing), fill any unused space with black, including most of the space between your board designs

 

[Screech]

more info ?, Zack.

What developer solution are you using?
Sodium Hydroxide? or Universal Developer.


I'm gonna make that suicide saw too.

 

[zachtheterrible]

Thanks just DIY, I can see a couple things that I'm doing wrong:
1. Don't think I was keeping it agitated enough
2. I think I might need to expose the board longer. I'm using a halogen desk lamp that is only a couple of watts. I'm exposing for only 5 minutes.
3. My piece of glass is from a picture frame and is definetaly not 1/4" think.

BTW, I really like your suicide saw :lol: . Especially because it's the only power saw that I own :wink:

Screech, I'm not really sure what kind of developer that I have. It is made by MGchemicals and says that it is for use w/ 600 series presensitized baords.

 

[justDIY]

mg chemicals - yep that is sodium hydroxide and mg's 'secret' ingredient, which I suspect isn't that crucial - i gave up buying the bottled stuff and went with the crystalized sodium hydroxide instead ... www.web-tronics.com has it for 50 cents a piece in quanity, just mix it up with a few cups of water and you're good to go

halogen doesn't put out enough of the right spectrum, according to mg ... use a standard "soft white" 60 or 100 watt bulb, and just suspend it 6-8" above your board or use a 15 watt under-cabinet fluorescent light (usually like $5-10 bucks at home depot) and position it 4-6" above your board

sounds like you're using 'single strength" or 1/8" - might not be heavy enough, the transparencies I use really wrinkle up in my printer, even though they claim to be for laser printers ... the 1/4" slab 'o glass really smooths it down. I also have a piece of non-slip shelf liner under the pcb, so I can slide the glass and transparency around a bit to align it correctly to the pcb.

 

[Screech]

mg chemicals - yep that is sodium hydroxide and mg's 'secret' ingredient, which I suspect isn't that crucial

HOW DID I KNOW!!!

No wonder they keep it a secret.
If I was selling that ****, I wouldn't advertise that sodium hydroxide was in it either.

Do your-self a favour and only use universal developer,

**broken link removed**

....crystalized sodium hydroxide instead ... www.web-tronics.com has it for 50 cents a piece in quanity, just mix it up with a few cups of water and you're good to go

yeah, you get what you pay for, and a headache.

 

[mstechca]

use a developer that is all ready to go, and put like a teaspoon of it in a container with about 1/4 cup of water. You may have to double or triple the recipe for bigger projects, but make sure the ratio of developer and water are about the same.

I use a hack saw for my board. and I think using shears is just plain wrong. For every method, some photoresist cracks at the edges where you have sawed the board. This is normal according to MG Chemicals.

So just make sure that you saw a board at least 5mm bigger in length and width.

You can use a halogen lamp to transfer the image on the transparent paper to the board. Make sure the glass covers the board completely.

Leave it under the lamp (1 foot away) for at least an hour.

now stick the board in the solution completely, and switch to normal light. Turn the halogen lamp off. In about 10 minutes, the board is ready.

If you see a dark colour liquid forming in the water, that means you need to stir it. (or better yet, wiggle the container the solution is in).

 

[zachtheterrible]

https://www.web-tronics.com/posdev.html
Is that the developer you were atlking about DIY? And does it work well? screech doesn't seem to think so.

It's funny that halogen doesn't work. It has a UV filter on the light. If a soft white has more UV in it, then why does my halogen have a UV filter??[/quote]

 

[justDIY]

thats' the stuff ... I'm not how much cheaper someone can get sodium hydroxide for ... or if it is worth the trouble.

that crystalized stuff couldn't be easier to use, I just pour the recommended amount of water into a tray, dump in the packet, and slosh it around till the crystals are gone

i quickly developed eight boards with one batch, and could have done more but the mixture starts getting cloudly with all the resist it has dissolved, so at 50 cents a mix, just toss it out and start fresh

regardless of what developer you use, it must be agitated - anyone claiming otherwise, well, they're just really lucky

as far as exposing the pcb for an hour ... my goodness that's overkill or the light source is really weak ... seeing as how the pcb itself is the most expensive part of the operation, it's worth the investment to buy a cheap fluorescent light or incandescent "painters light" (just a socket with a cord, a cheap aluminum reflector and a flimsy clamp) - it'll last virtually forever and yeilds excellent results

with phototransfer and my method (fluorescent, crystal developer, ferric chloride etchant) I routinely make boards with all sorts of SMT pads, traces down to .0120 inch (12 mills or 0.3048 mm)

here is an example of the results I get:

on the left is a pcb with 12 mil traces, next to it on the right is a board with 24 mil traces ... these have been banging around in a drawer for a bit, so the resist is scratched a bit.

**broken link removed**

 

[zachtheterrible]

Well the proof is in the pudding and that pudding looks good. I think I'll try that crystalized stuff. And if it doesn't work I'm out a whole $.95 :lol:

The presensitized boards are real nice and cheap too, cheaper that I've ever been able to find. Thanks for that link. I have an exposure source sitting on my desk, my 100W lightbulb that I use for lighting :lol: