Work light for exposing presensitized boards

[burningman]

I was wondering what the general consensus was on using high wattage work lights for exposing presensitized boards? In several instances I've heard that it will work, in others not. Are there any cheap, alternatives to to the MG chemicals light kit, that is available in Canada?
thanks.

[fpaul]

I've been using a 150w halogen worklight from harbor freight about eight inches away from the board.  I open the front before using but not sure if it is necessary.  Probably not good for the eyes so I just turn it on and go away.  I was using 8min but overexposed a board so I'm using about 6min now.  Works good and I've been making some fairly large boards.

[burningman]

What kind of glass do you use for covering/weighting-down the transparency?
Would plexiglass work?
Would double sided boards be possible, or partly exposed by the first top exposure?
Thanks.

[burningman]

Just purchased two 500w worklights from Home Depot, total cost $30!
My goal is to set them up opposite each other and place the double cladded copper in between at a distance of a foot or so on each side.
Is this a fire hazard ?

[davent]

Hello,

I posted this long ago in another thread and i think covers most of what you're trying to do. I'm using MG boards and chemicals and currnetly use an exposure of nine minutes, in the quote below i say twelve minutes.

Davent where do you get your photosensitive boards? Also how do you develop them? Do you have a special UV bed for it or use some sort of makeshift light? Do you just drill the holes with a dremel tool or something? I'm really interested as I too love making PCB designs. I've never gotten one made though I've almost sent in orders to BatchPCB and Futurlec to get them fabricated but the fear of it not working coupled with the cost made me chicken out.

Hi Mike,

I use MG Chemicals' boards and developer which i get from a local electronics store. I've also used no-name boards and developer i've picked up in shops in Toronto as well as the various boards from companies in the Digikey catalogue. A city the size of Chicago's gotta have a few shops you could walk into and pick up some board and developer. Digikey (as well as the other suppliers big and small)  has boards from a few different companies but i don't know whether they carry developer. The MG developer is sodium hydroxide. If you google sodium hydroxide pcb developer or sodium carbonate PCB developer you should get some instructions on mixing your own from grocery or hardware store products. 

For exposing the boards i just use regular flourescent tubes. I used to stack up phone books, Digikey catalogs and other tomes on the kitchen counter under the cupboards to raise the boards to within an inch or so of the under cupboard lights. Now,  above my workbench are a pair of 4' tubes recessed between the joists and i've screwed a piece of clear plexglass that was lying around, to the joists so i have a shelf just below the tubes. The PCB's now get exposed on the shelf there.

I use a frameless picture frame from Ikea to hold the transparency/PCB sandwich securely during the exposure which, with the boards i've been using is about 12 minutes.  I print out two copies of the artwork onto a piece of transparency with a laser printer and make a sandwich of those. Before we bought a laser printer i used to take a copy of the artwork to the local print shop and get them to make a copy onto a transparency with one of their uber  photocopiers and with those i only ever used one layer of transparency but with my cheap laser printer i need the insurance of two layers of art.  So expose for 12 minute then into the developer for ~ 90sec's then it's ready to etch. For a developer tray i just use a little dollar store Tupperware type container marked for developer use only. Dollar store would probably have the picture frames as well.

 
Take care,
dave

[burningman]

I thought about floresent bulbs but the cost was a bit more than I wanted to spend. I'll just remove the UV covers and cage from the work light and hopefully that will produce a good exposure on my board. 

[nomorebetts]

I use an ordinary desk lamp with a 15w flourescent bulb about 10cm from the PCB sandwhiched in a picture frame for 10mins.
Works a charm.

I'm in Australia and use Dick Smith brand positive resist light sensitive boards, develop in a caustic soda/water solution, (caustic soda bought from the supermarket) then etched in ferric chloride etchant from Dick Smith.

[darron]

i made an exposer with 52 (edit) UV LEDS....




results were not so great....


thought id share my adventure though!

[merlinb]

I use an old face-tanning lamp that I bought second hand on ebay.

[fpaul]

What kind of glass do you use for covering/weighting-down the transparency?

I use an old picture frame I had lying around.  I don't know if plexiglass would work or not.  500watt should work as I'm only using 150watt.  You may have to experiment with exposure time.  Also be careful with the developer as it goes very fast.  The one time I had a problem, I'm not sure if it was over exposed or over developed. I've never tried a double sided board.

[darron]

be careful not to use some acrylics and such that are uv resistant. many people who will sell it to you might not even know that they are uv resistant...