Electronics > Manufacturing & Assembly

UV Exposure times

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sleemanj:

--- Quote from: wraper on November 15, 2013, 08:31:39 pm ---. So no hassle at all. Some do it without laminator.

--- End quote ---
I apply negative film using a clothes iron mostly (obviously for boards smaller than the irons plate).  On  a very cool setting just a couple clicks above minimum.  Stick the film down, cover with a piece of paper, sit the iron on top for about 30 seconds, then gently rub it with the iron, especially along the edges.

Any air bubbles that got in, I prick and then rub-down with the iron point to smooth them out.

Temperature is the the key, must not be too hot, too hot and the polymer blisters. 

Have board and film cold when attaching the film, makes it easier (less inclined to bond on contact so you can reposition a bit).

wraper:
I stick board on a piece of paper and stick film in one end. Then feed it to the laminator while holding the film at the same time. So film meets the pcb on laminator rolls, therefore no air bubbles. Then hot run to make better adhesion.

akis:
Please remind me what is the advantage of applying the film on the PCB at home rather than buying a ready made photo resist coated PCB?

sleemanj:

--- Quote from: akis on November 16, 2013, 10:49:13 am ---Please remind me what is the advantage of applying the film on the PCB at home rather than buying a ready made photo resist coated PCB?

--- End quote ---

1. Cost, film is cheaper
2. Flexibility, apply film to any size board, which you can cut, drill, sand, clean, etc to your heart's content before applying film
3. Screw up an exposure with a precoated pcb then you have something not useful (unless you use it with a different method), with film, strip off the film and start again.
4. No dark space required, work under normal household lighting conditions
5. Film is negative acting which may be advantageous if your print is a bit light
6. Develop and strip safely with Sodium Carbonate (Washing Soda, from any supermarket), no need for somewhat more dangerous Sodium Hydroxide (lye, the stuff used in soap manufacture and for example in Fight Club).

madires:

--- Quote from: sleemanj on November 16, 2013, 10:48:17 pm ---1. Cost, film is cheaper
2. Flexibility, apply film to any size board, which you can cut, drill, sand, clean, etc to your heart's content before applying film
3. Screw up an exposure with a precoated pcb then you have something not useful (unless you use it with a different method), with film, strip off the film and start again.

--- End quote ---

If you just focus on cost (excluding time :-), those are valid points.


--- Quote ---4. No dark space required, work under normal household lighting conditions
5. Film is negative acting which may be advantageous if your print is a bit light

--- End quote ---

Never needed a dark room for photoresist coated boards.


--- Quote ---6. Develop and strip safely with Sodium Carbonate (Washing Soda, from any supermarket), no need for somewhat more dangerous Sodium Hydroxide (lye, the stuff used in soap manufacture and for example in Fight Club).

--- End quote ---

Another good point, washing soda is cheap and simple to dispose. I'm lucky because we got a regularly free disposal of dangerous waste for households organized by the county.

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