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ATTN: PCBers SUBJECT: New website and exposure box design for your creative needs - Page 5 — Parallax Forums

ATTN: PCBers SUBJECT: New website and exposure box design for your creative needs

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Comments

  • $WMc%$WMc% Posts: 1,884
    edited 2012-02-01 19:45
    @Bruce--
    '
    Now do you see what I was talking about in post #117..?---
  • idbruceidbruce Posts: 6,197
    edited 2012-02-01 20:59
    @Walt
    Now do you see what I was talking about in post #117..?---

    Of course my problem could have been due to a couple specks of large dirt :)

    But of course I did not find any. My only explanation is a bad section of film. However it is the only true problem that I believe I have had.

    Hopefully your new boards will give you better results.

    I am still not happy with the second exposure plate for my test samples, so I am building a third based upon a previous design. I thought it would be much harder to make, but actually it seems much simpler, more accurate, and easier to get everything to fit together properly.

    I just remembered, I have a spare 3 X 4 exposure plate laying around and it is in good shape (everything fits snug). I will get it out to you soon. After exposing a board with this plate, you must tap the plate against your palm to seperate the board from the positive images, exposure frame, and top glass.

    Bruce
  • idbruceidbruce Posts: 6,197
    edited 2012-02-02 05:29
    @Walt

    In my previous post I stated:
    After exposing a board with this plate, you must tap the plate against your palm to seperate the board from the positive images, exposure frame, and top glass.

    You should now disregard that statement. I have decided to cut an access groove in the exposure plate to help assist in the removal of the top piece of glass, the top artwork, and the PCB. The bottom artwork will still prove to be a little bit of a pain to remove, but it will be worth the trouble for the alignment that you will get in return. Referring back to the previously mentioned groove, when I get finished, you should be able to remove the top piece of glass, the top artwork, and the PCB with a sharpened pencil eraser.

    Bruce
  • idbruceidbruce Posts: 6,197
    edited 2012-02-03 12:05
    I have been taking it easy with the experimenting the last several days, however I did manage to make my very best exposure plate to date. This plate is exceptionally well made. Sometimes I even manage to impress myself. :)

    Anyhow, after dancing all around the perfect PCB exposure, I wondered if Leon could be correct about not being able to achieve perfection with vellum as a positive medium. So I decided to give transparencies another shot with the new exposure plate. I would now say that the exposure is about 99.95% perfect. The only noticable flaw was the two required periods within the homepage web address were missing, however these two periods are very small. After checking other exposures, I noticed that only in a couple did the periods actually show up, and when they did, they were very faint. I will have to do more testing with the new exposure plate and transparencies to see if I can acquire these two periods.

    Okay Leon, I concede, transparencies are definitely working better.

    Bruce
  • LeonLeon Posts: 7,620
    edited 2012-02-03 13:11
    A long time ago I used tracing paper (I think it's similar to vellum) with a laser printer, and had problems getting the correct exposure. I did get it working with fairly wide tracks, but it was never very satisfactory. Another technique is to print on ordinary paper and apply vegetable oil to it, I got similar results with that. The lack of contrast seems to be the cause of the critical exposure.
  • idbruceidbruce Posts: 6,197
    edited 2012-02-03 15:40
    Leon

    I have been able to get acceptable results with vellum for upto 0.010", but that is unacceptable for what I am trying to achieve. My goal is to be able to make solid 0.004" tracks with no problem. And I don't believe that I will be able to do that with vellum and have everything else turn out right. I have read about the vegetable oil trick before, but opted not to introduce oil into the process.

    Recently I purchased a few sheets of laser tranparencies from Office Max, but the transparencies were just to thick, which caused steaking and an inadequate positive. I found some remnants of older tranparencies that I had laying around and I made some nice positives from it. Now I need to order some more from Amazon. As you know, the price of transparencies is quite costly, and of course I was trying to avoid it as much as possible. However, as stated, my main goal is quality and having the ability to do the 0.004" track widths, so I guess I will have to bite the the bullet on this, as well as anyone else that use my system and wants equal results.

    I am now coming close to running out of sample material :(

    Bruce
  • TtailspinTtailspin Posts: 1,326
    edited 2012-02-03 18:57
    I think it takes at least one year of shelf life before the coating starts to to bad, probably more like two years.
    I know the old boards I bought were at least three years old, I remember when she hung them on the rack, brand new.
    it was about a year ago that I asked her about them, and she sold them to me at the bare copper board price...


    Hey, don't forget about your local printing shop,(Kinko's, the UPS store, ect, ect..) for buying blank transparencies,
    The one I go to will sell blank sheets for $1 each. That way I don't have to buy 80 sheets all at once.

    Normally, I will just bring my page of artwork in to them and they will print it extra dark for me,
    I try to cram as many circiuts onto the page as I can fit, then just cut them up as I need them..


    -Tommy
  • idbruceidbruce Posts: 6,197
    edited 2012-02-03 22:32
    @Leon

    Earlier you mentioned using the JetStar film for your positives. I was wondering if you have ever tried the LaserStar film and if you were happy with the results and how it compared to standard transparencies.

    Bruce
  • LeonLeon Posts: 7,620
    edited 2012-02-04 02:26
    I used the LaserStar film for a while, until I switched to an HP inkjet printer and JetStar Premium film. The LaserStar worked very well, and is the best stuff to use with laser printers, but an inkjet printer is much better. The film is expensive, so I cut it roughly to size and stick it to a piece of A4 paper with a piece of masking tape on the leading edge for printing. I then trim it before exposing.
  • $WMc%$WMc% Posts: 1,884
    edited 2012-02-04 11:15
    @Bruce
    '
    Have you tried the 3M PP2500 film? (clear transiences sheets 8 1/2" x 11")
    '
    Its made for over head projector use.
    '
    It has a high temperature rating and its crystal clear.Its thick to keep its size..But its not cheap.
  • idbruceidbruce Posts: 6,197
    edited 2012-02-04 18:39
    Walt

    Through my experiments, I have come the conclusion that my exposure box design and the Premier boards from DATAK are a perfect marriage, however the positive necessary to reach perfection is inadequate. I truly believe that so much could be achieved with my exposure box design and the premier boards, if I only had a nice positive image. I do not believe that a positive image from a laser printer is going to cut the mustard for the type of perfection that I am attempting to achieve. However I am going to visit Office Max, Office Depot, and if I can find a Kinkos I will visit them also, in an attempt to acquire the best positive image possible with spending a great deal of money. I am almost half-tempted to purchase a floor camera or vertical camera for making outstanding positives.

    The laser transparencies that I have been printing are not completely opaque, and to achieve perfection, I will need a positive where the black lines are completely opaque. I am sure you have already printed with the 3M PP2500 film, so do me a favor and carry a sample over to a lamp and let be know if the black lines are opaque or if small amounts of light can pass through.

    Bruce
  • TtailspinTtailspin Posts: 1,326
    edited 2012-02-04 19:32
    The kid "in charge" of the copy machine just needs to know he is in charge, Tell him so..
    And the ink will be as dark and thick as the machine will allow..Think Tom Sawer having to whitewash a fence...
    My "copy guy" knows the way around HIS machine.(feels specially invested now that he has read the manual) :lol:
    when he gets done turning everything up to 100%, the finished artwork will block bright sunlight...:thumb:


    -Tommy
  • $WMc%$WMc% Posts: 1,884
    edited 2012-02-04 20:55
    @Bruce
    '
    My traces are 100% opaque
    '
    Send me your files and I'll print them out and send them to you.
    '
    I have a laser and inkjet printer. I'll print from both printers.
    '
    I'll throw in a few blank transparencies "3M PP2500"so you can see if your printer's are producing the same results as mine.
    '
    PM me your mailing info.
    '
    The image below
    '
    Note the streak in the middle of the film...This was from a previous attempt at a copper poor with the Laser printer.
    My Laser printer does not like to put this much toner down on film or paper for a copper poor.
    After seeing this print I had to clean the laser printer
    '
    The lite spot is the flash from my Android Nexus S 4G....sorry
    1024 x 768 - 65K
  • idbruceidbruce Posts: 6,197
    edited 2012-02-07 05:27
    @Walt

    Thanks for the offer Walt, but I would have been unable to wait.

    After upgrading my positive films, I believe I have finally achieved a sample that is worthy of a photograph. I can't say it is 100% perfect, but definitely worth a photo. I have given up on the hope of getting the dots in the web address, because they keep disappearing either in the developing process or the etching process. They are just to darn small. However, the 4 mil, 6 mil, and 8 mil wire traces all came out looking very nice. I may experiment just a little at a later date to see if I can make a better sample, but for now, I believe I have a good result which will clearly convey the capabilities of my exposure box design.

    Before uploading a photo, I will tin plate the copper traces for a more finished appearance. Of course this will be a first for that process concerning my homemade PCBs. But hey, it is all a learning process.

    For the most current specs concerning my process, please refer to post #110.

    Bruce
  • idbruceidbruce Posts: 6,197
    edited 2012-02-07 15:38
    A good photo mask makes a huge difference. Instead of settling for a two minute and 5 second exposure time, I just tried 1 minute and 30 seconds again. It turned out looking beautiful, but I accidentally left a little resist haze on the board, which of course destroyed it. I never could find a yellow 25 watt bug light locally, so I settled for a tiny 7.5 watt night light. It is kind of nice, but it is very hard to see any left over haze.

    Anyhow, it is looking very promising that I might get periods back in the web address. However, I just scratched my best looking positive and have to create a new one. Actually, I already have one made, I just have to trim off the excess film. I sure wish I had a durable and crystal clear photo masks, then I could really show you a piece of beauty.

    Bruce
  • softconsoftcon Posts: 215
    edited 2012-02-07 18:30
    Wouldn't it be possible to build a small version of a plotter (the kind they used to use in mechanical drawing computer controled classes) and program one of those to etch the board directly instead of messing with chemicals and such? It would seem to me that perhaps it would take longer (since it's cutting harder material) but wouldn't require anything but a new blade in the plotter each cut run.
    Am I way off base here, or would something like that work, and if so, would it be cheaper than purchasing expensive chemicals to do the job, not to mention the time spent on exposures and everything else.
    Of course, there may already be such devices too, and maybe folks are already doing that, but hadn't seen it mentioned here, so figured I'd ask. If I could find such an animal, I'd certainly use it, since mucking about with potential lethal chemicals wouldn't be a very good idea for me, but building circuit boards would definitely be something I'd be interested in doing.
  • softconsoftcon Posts: 215
    edited 2012-02-07 18:56
    I don't know what your box looks like, but this is the parallax forum after all. It should be possible using a stamp or propeller board to automate most of the process. I.E. ds1620 for temperature, then once it's right, open a light blocking cover, let the film expose for x seconds, then close the lid again.
    That way, you could control a lot more closely your exposures and your time trials would be picture perfect. :)
    Of course, how this could be accomplished is a whole nother can of worms, but it seems to me it should be possible.
    Just an idea.
    Feel free to ignore/shoot down/explain away/anything you like the suggestion, just putting it here as a possible solution, since it seems like you're having trouble getting exposure times exact.
  • LeonLeon Posts: 7,620
    edited 2012-02-07 19:00
    There are milling machines for producing PCBs directly, but they are expensive and slow.

    I've thought of using a PIC to control my UV exposure unit, but it's just as easy to use a timer app on my Dell Streak tablet.
  • idbruceidbruce Posts: 6,197
    edited 2012-02-07 19:24
    @softcon

    As Leon mentioned, there are PCB milling machines that operate on x, y, and z axises. They use miniature router bits to eat away at the copper layers. In my opinion, photographic imaging will output a far superior product as compared to PCB milling. Then you must also consider dust issues raised by the milling process. I like building CNC machines, and in fact the next machine I am going to build is a PCB drilling machine, but as far as creating the wire traces, giving me photographic imaging anyday.

    Pertaining to your second post, as Leon also mentioned, a timer is all that is necessary for an exposure box. I am currently contemplating the removal of my basic stamp timer from my other exposure box for my current setup. Other parts of the process may also be microcontrolled such as heating the developer and etching fluids.

    Bruce
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-02-07 20:40
    A CNC PCB engraving machine would be a real challenge to build from scratch. The reason is that the cut depth relative to the top surface of the copper -- not to the top of the platen -- is extremely critical. You need some sort of feeler that rides along the PCB surface to provide feedback to the Z-axis drive, rather than relying upon any kind of absolute coordinates. That's probably one reason the commercial units are so expensive.

    -Phil
  • idbruceidbruce Posts: 6,197
    edited 2012-02-07 20:55
    @Phil

    I never really looked at any commercial PCB millers, but none of the homebrew machines I have seen or read about had anything like that, however I must say that it is a very good idea. I am sure that would help to keep the dust down to a minimum.

    @All Others

    I tried another exposure at 1 minute and 30 seconds, but this time I made sure that I removed all unwanted haze. I must say that I now have two samples that are definitely worthy of tinning and photographing. In the previous 2 minute and 5 second exposure, the web address is definitely more legible, but in the 1 minute and 30 second exposure, the traces appear to be much nicer. Sorry I did not get to the tinning process and photography today, but I will definitely have photos tomorrow :)

    Bruce
  • idbruceidbruce Posts: 6,197
    edited 2012-02-08 06:02
    UPDATE:

    I must say that with some fairly decent artwork, the results have now become very consistent. I can only imagine what the results would look like if I had better artwork.

    I just completed a 1 minute and 45 second exposure, and I must say that this one came out looking pretty nice also. So instead of two samples to tin and photograph, I now have three, which are:
    • 1 minute and 30 second exposure
    • 1 minute and 45 second exposure
    • 2 minute and 5 second exposure
    All three of these samples are double sided boards, with both sides being exposed simultaneously with my exposure box/cylinder, using standard incandescent 60 watt fan light bulbs on each side of the board. For more information pertaining to the exposure box/cylinder, please visit http://www.novelsolutionsonline.com/exposurebox.htm

    LOL Who needs UV lighting for PCB exposures? Not me :)

    I can't say that any of them are 100% perfect, but they look pretty good. And I would have to say that the remaining flaws are directly associated with imperfect photomasks. Eventually I will obtain a much better mask and I am certain that the quality will improve. Until then I will show you what I have achieved so far and let you guys be the judge of the outputted boards :)

    Just give me a little more time for tinning and photographing, and please return later tonight, 02/08/2012, to see the results of these three exposures.

    Bruce
  • idbruceidbruce Posts: 6,197
    edited 2012-02-08 07:37
    As previously mentioned, I have never tinned my boards before, but this tinning solution is some wierd stuff :)
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-02-08 09:21
    Back when I made my own boards, I just left the photoresist on after etching. I could solder through it, yet it protected the unsoldered copper from corrosion, obviating any need for a tinning solution. Boards that I made twenty years ago are still corrosion-free.

    -Phil
  • idbruceidbruce Posts: 6,197
    edited 2012-02-08 11:53
    Phil

    That etch resist must have been well made to last twenty years. I would imagine it must have been laquer based. The method that I just used for the tinning process seemed kind of hinky. Simply mix two unmarked powders into water and add the boards. It worked pretty good, but I imagine that if I ever produce any type of commercial boards, I will do it by electroplating, for which I have some decent documentation.

    Glad to hear that your boards are still in good shape after twenty years :)

    Bruce
  • idbruceidbruce Posts: 6,197
    edited 2012-02-08 12:12
    CONTINUITY TEST RESULTS AND OTHER INFO

    After the tinning process, the board that was exposed 2 minutes and 5 seconds appeared to have some broken traces, most particularly the 4, 6, and 8 mil traces. Without any delay, I decided to perform a continuity test on all three sample boards. I am proud to say that all traces on all three sample boards, being tested end to end, have the ability to pass current. I must not have removed all the photoresist residue from that particular board prior to the tinning process.

    As a side note, I found someone ealier today that is within an hours drive that is willing to create film positives for me. He uses a digital to film process, and this should enable me to produce much higher quality boards, if I should ever decide to do so. I am also contemplating the use of his services to enable me to offer film positives on my web site for those that demand the highest quality exposures. Of course these film positives will be limited to the size of my exposure plates.

    Don't be impatient.... Photos coming soon.

    Bruce
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-02-08 16:05
    When you have the photo house do the films, be sure to add some text outside the board area and specify "positive, right-reading, emulsion side down." The text will help them determine which direction "right-reading" is.

    -Phil
  • idbruceidbruce Posts: 6,197
    edited 2012-02-08 19:42
    UPDATE - PHOTOS OF THREE SAMPLE BOARDS

    Until my brother figures out how to use his nice new photo equipment, these photos will have to do. I will be updating this particular post often, so you may want to keep track of this post, as well as post #110.

    As I previously mentioned, I am certain that these boards could have been much better, if only I had a much better positive film to work with.

    Exposure Unit: My PCB Exposure Box/Cylinder listed at the beginning of this thread.

    PCB Material: Philmore DATAK Premier Series (1/16" 2oz. double sided FR-4 board with positive acting photo-resist film)

    Test Size: 0.937" X 0.937"

    Front Test Pattern: Gradient lines 0.004" - 0.008" in 0.002 increments.
    Rear Test Pattern: Gradient lines 0.010" - 0.075" in 0.005 increments.

    Positive Medium: Premium Matte Laser Film (0.004") Top Coated With Acrylic Krylon Crystal Clear Satin (#51313)

    Exposure Lamps: (2) New 60W/120V Sylvania A15 Ceiling Fan Light Bulbs (60A15/CL/2PK/BL)

    Exposure Time: 1 minute and 30 seconds
    Exposure Time: 1 minute and 45 seconds
    Exposure Time: 2 minutes and 5 seconds

    Developer Mixture:
    • 4 grams of Rooto Crystals of Household 100% Lye Drain Opener (available at ace hardware)(caustic soda/sodium hydroxide) to 1 pint of tap water
    Developer Temperature: 106 degrees fahrenheit

    Bruce
    642 x 708 - 64K
    642 x 708 - 63K
  • idbruceidbruce Posts: 6,197
    edited 2012-02-08 19:45
    Phil

    Thanks for that good piece of advice. I appreciate the tip.

    Bruce
  • LeonLeon Posts: 7,620
    edited 2012-02-09 04:12
    You should really be testing with the inter-track spacing equal to the track width, such as 8/8 mils. Just achieving narrow tracks with wide spacings is quite easy, but that isn't what people use when designing boards for maximum track density.
This discussion has been closed.