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Photo Resist Preparation
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Hello, Recently, started using photo resist technique for making printed circuit boards (PCB).? One of the steps in this technique I'm having difficulty with, is making sure there are no air bubbles between the photo resist sheet and the PCB.? So far I've only been successful on small boards, 4" x 5", 3" x 6", etc? in clearing the air bubbles, but not larger boards, e.g.,? 6" x 8".? I would like to use the photo resist technique to make larger boards in the 8" x 11" range but, I'm hesitant to try due to my lack of understanding of how to remove all air bubbles on the larger boards.? I've made a 6" x 8" board but, could not remove all the small air bubbles, approximately 1/8" dia. or less,? between the photo resist sheet and the PCB.? The board did turn out okay but, believe I got "lucky" with no small air bubbles on any of the traces or component pads.? Prior to being exposed to the UV light the PCB with the photo resist sheet was run through a laminator but, the remaining small bubbles were not removed.? Not sure my luck would hold if tried to make another 6" x 8" board.? I have used toner transfer for larger boards, but had too many broken traces and spotty transfer of the toner on the board.? Neither using a clothes iron nor a variable temperature laminator gave consistent good transfer of the toner to the larger boards.? YouTube was searched for an answer and a number of videos on making PCBs using the photo resist technique have been reviewed.? However, only small boards, less than 6" x 8", were in the videos.? There were several different approaches used to get the photo resist on to the board and removing air bubbles, but again, these approaches were used for less than 6" x 8" PCBs.? I'm sure I haven't seen all the YouTube videos on making PCB using photo resist, so maybe there is one or more showing how to apply the photo resist to the larger PCBs and end up without any air bubbles, small or large, between the photo resist and the PCB.? ? V/R, ? Mike, K4GMH -- Mike, K4GMH |
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Try wet lamination. One person on the net describes submerging both the film and the board completely in water, another just sprays some water on the board. I have only experimented a little with the photosensitive film. Spraying a small amount of water and working any bubbles with a squeegee before laminating does seem to work. One person said to let the board dry overnight, however in their literature Dupont states that if you use wet lamination the board should be processed "without delay". Even if you are not using Dupont (Riston) film you may find some of their instructions and information useful in working out a process that works for you.? ? Start with: f ? Some of their other product specific literature may also be worth looking at. If you work out a process that works for you please post your results. ? Craig L On Sun, Mar 10, 2019 at 09:22 AM, Michael Sims wrote:
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开云体育Mike, Even though it goes without saying, your boards must be cleaner
than clean for this to work. Small particles will lift the film.
One tip that shows up repeatedly is to test the cleanliness of the
board by spraying a light layer of water on the surface to be
laminated. If the board is reasonably clean, it will support a
continuous film of water. The film will pull away from spots that
have oil or grease, and from around particles. The water you use
must be clean enough that it doesn't introduce particles on it's
own. Filtered or distilled water should do the trick. As I read your post, I remembered that I saw some processes for
dry film application. You didn't mention if you wet the film/board
before application, but I remember seeing a few posts somewhere
about that. I did a search, and found this one on Instructables: . The first part seems to be a justification for how the OP arrived at the process, and can be skipped. This method seems to be very flexible in terms of the ability to go back and re do if there a problem, but it is very labor intensive. Here is a second article, rather verbose, but he also uses a wet method: This page from Dupont has a PDF titled "Riston Processing Guide"
that talks about cleaning and laminating, among other things:
Think and Tinker has a very complete manual on PCB production, including a section of Dry Film laminating. Find them here: I hope this helps (The other) Harvey On 3/10/2019 9:22 AM, Michael Sims
wrote:
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As described in my tips document ? I find a mister bottle of water is the best way.? Mist the cleaned PCB with water, don't need much, lay the film down preferably making first contact in the middle, squeeze out the water and bubbles with a squeegee from the middle out, then clothes iron/hot air to bond the film.? You can pull up and reposition to a degree before you apply heat.? Clothes iron must be only warm, too hot and the moisture will make a mess of things, just warm and the film will adhere fine.? Laminator would work fine too I expect if you use one already, I have one somewhere but find clothes iron more convenient. I just use a wad of paper towel for my squeegee, not an actual squeegee. bigclivedotcom on youtube has shown similar method to mine a number of times if you search his videos for ones where he makes a PCB in the last couple years (before that he used pre-sensitised boards). On Mon, Mar 11, 2019 at 8:48 AM Harvey Altstadter <hrconsult@...> wrote:
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Sorry my reply wasn't intended as a reply to Harvey's post specifically, Gmail is a bit misleading when it comes to replying to threads.? Also didn't notice Harvey had already linked to my tips :-) On Mon, Mar 11, 2019 at 9:20 AM James via Groups.Io <bitsyboffin=[email protected]> wrote:
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开云体育James, I think we were both doing the same thing at the same time. It
was just a matter of who posted first. On 3/10/2019 1:30 PM, James wrote:
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I've used photoresist film for the past 8 years or so. I mostly work with brass and stainless steel sheets that are 6 x 12 inches wide and .015 inch thick creating artsy bits of stuff. I've made a few circuit boards for friends, and some other thinner designs over the years. What I'm saying is - I've used the film for a long time and might be able to help.
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The best way is to clean your work table. Use a spray bottle and spray your work area with water. Clean your board with soap and hot water. Rinse and put on your work area. Peel off the back layer of the film. Put it on your work area with the peeled side up. Spray both board and resist with filtered water (no debris). Flip the resist onto the board. Squeegee several times looking to get bubbles out. I'd they don't come right out, you can peel back the resist and reapply. Sometimes there are flakes that get on the film. Use your finger to slide it off the film. This is the first part. If everything at this point is bubble free, you're not out of the woods just yet.
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Put your board between 2 pieces of paper and tape the edge that goes through the laminator first. Check the specs to see how hot the laminator should be and put the paper with your board in the laminator when it's heated up to the right temp. If your laminator is too hot, or if you run it through several times, you may get bubbles that weren't there before.
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Now you have a laminated board that still if everything was done to the best of your abilities, may still have a bubble. If that happens, the best thing to do is get an x-acto knife and poke (not cut) a hole in the middle of the bubble. Use your finger to push the film flat. Most of the time this works without issue. The finger pressure might be enough to adhere the film to the board, ?or you may want to put it through the laminator again on lower or no heat at all. Sometimes finger pressure at this stage is enough. Excessive heat causes bubbles.
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Sorry to be so wordy, but this is an issue even with 2 inch pieces that I make. Bubbles are a pain, but they can be dealt with.
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Sven |
Leon