Project: Photographic methods of making PCBs

Discussion in 'The Completed Projects Collection' started by Lestraveled, Mar 1, 2015.

  1. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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    You might be able to spin coat your photo-resist. That's what I did because we had it in the photo-lithography lab. Not designed to do PCB's, but I did them anyway. We also made trinkets by evaporating gold on glass and then doing the photo-lithography process. You do need an accurate way of measuring the light source and timing it for exposure. All of that part of the process was done for me.

    It was something like spin coat, bake, expose and etch. So, I used a mask-aligner which is used to make IC's to make a PCB.
     
  2. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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    How large is large?

    I actually used an early Autotrax DOS PCB layout package. I needed a ground plane, so I just edited the postscript file directly.
     
  3. DPHigley

    New Member

    Dec 21, 2016
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    Thank you, but it looks to me as though the printer would be a substantial investment, and I don't think the volume I do would be worth it. It's pretty quick and easy to do the intermediate litho step. For the initial image, I'm using an inexpensive inkjet printer and "waterproof silk screen positive film", which works beautifully and requires only one layer for contact printing on the litho film.
     
  4. DPHigley

    New Member

    Dec 21, 2016
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    I've recently switched from chemical etching with ferric chloride to electroetching. Do people ever use this for PCBs? Awfully easy to set up, with a battery or two, a piece of copper on the other side of the tank that was pictured for sodium persulfate etching, and an electrolyte (solution of Root Kill) that will last indefinitely.
     
  5. StillMoving

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    Apr 9, 2017
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    Lestraveled, I would like to say thank you for your very clear, and in depth, walk through of using the lithographic film to make a contact negative of your positive artwork. I have read articles before, of people doing it, but none of them gave the specifics on every step the way you did, and your presentation answered many of my questions, and have provided the boost in confidence to continue on a project I've in the works for years, but had slacked off on.
    It would be taking your photographic process a step or two farther, by eliminating the printed positive, that you make the negative from, by using a large format camera to take a photo of the artwork, as it is displayed on a 32" 1920 x 1080 LCD monitor, with the camera setup for the proper reduction needed, to give the proper finished size negative. Or, for more resolution, use our 46" led TV, (with wife's permission), to display the artwork . I realize I will need to work out the display intensity required, vs the exposure duration, and the camera distance from the monitor and the reduction level will be different for the displayed size on the chosen monitor, but either display's size would enable a 4x to even 8x reduction, with an equal increase in resolution in the finished negative. I would be interested in input, from people with camera, or film experience, of the problems this process might present.
     
  6. Paolo Beretta

    New Member

    Oct 6, 2017
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    I thought I could give my two cents to the discussion, mailnly about the bed of tubes and the off contact problem. Bed of UV tubes is convenient, as it takes less space and time than using a 12 inch tall lamp with an unprotected 3w UV LED, so for the off contact issue I worked out my own personal solution, carried from the way similar professional devices work.

    One of the main problems (especially with little PCBs) is that using a rigid PMMA sheet to flat down the PCB master may lead to an imperfect adhesion to the PCB surface. To fix this issue, I assembled a wooden frame and glued to it a cut of plastic sheet (the kind used to protect the floor when when painting rooms), then I used a small foam rubber rug under it and connected the whole structure to a pipe, tied to a vacuum cleaner. When exposing the PCB, I simply turn on the cleaner and the vacuum created under the plastic sheet holds the master in position no matter what the size is.

    It looks more complicated than actually is:

    20171006_111806.jpg

    Bye

    Paul
     
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  7. Janis59

    Active Member

    Aug 21, 2017
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    RE:""OK, enough about how I make PCBs. Now, lets hear how you do it.""
    I use a three methods.
    1) The iron method if there is only discrete transistors and no IC. The 1 mm and even 1/2 mm paths are well elaborated but DIP size is the smallest what is still stable. Technically is possible to produce even SOIC but the quality is rather poor.
    2) if the count of similar pcb~s are at least 100 I apply the polyvinylspiritus with chromium red, to mix the negative photoresist. Quality is rather high, but anyway the soic is most best what is possible to squeeze out. However each pcb cost is very small, because that chemical I have collected for next 100 lifes.
    3) Most often technique, however not very cheap - positiv-20 aerosol, blow, dry into 50 C hot-chamber, expose under 5x8 led matrix (400 nm) about 10 seconds and voila. Etch in the vertical quartz tank with air bubbler and pre-heating 50 C. Printing with COLOUR printer means that black is formed by three colours and contrast is far better than black-and-white printer, of course install that paint must be most bold, and correct the tone to about 120-130%. The quality of film of course is the base of all further, thus use a good printer. As the result - technically 50 micron wire on pcb will be reproduced quite well, but the question is how good is etching. But philosophycally, who is working with so thin wires?
     
  8. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    I have a couple of tips I would like to add.

    I use a hybrid process of drilling with a cheap CNC machine then using the toner transfer method to create the runs.

    If your process requires a lot of steps like mine then document your process. It is easy to forget what to do when if you take a break from the hobby for a while. I wasted a day on getting everything right. Now I have everything documented.

    I may have mentioned it before but I use wax paper in the toner transfer method. Works great and essential to the hybrid process.

    I usually use a lamminator to transfer the image, but I found that for really small boards the good old fashioned iron is better.

    Why I do not mill my boards:

    Simply I do not like the results. I think my issue is not enough RPM on my cheap machine. Plus it makes a mess. A lot of people mention the say that they mill because it is better environmentally. I just don't get it. Unless you have a really good vacuum system, you are creating a lot of fiber glass dust. A bit of muratic acid or ferric chloride is far less hazardous in my opinion.
     
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  9. spinnaker

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    Oct 29, 2009
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    I just hit on a new material to print on for laser transfer. Parchment paper. The type from the grocery store. It pealed right off with no residue left behind. I have only tried it for the component side of the board for component placement. I will post back when I try it for traces but it looks very promising.

    Edit I might also add that it transferred every bit of the toner.
     
    Last edited: Jan 2, 2018
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  10. Janis59

    Active Member

    Aug 21, 2017
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    RE: Spinnaker
    You speak about the ironing transfer method??
    It have principal limit when work with ICs with distance between feet less than 0,3 mm. Simply path sides are too inaccurate. When work is with over mm wide path paper is OK and just every type of paper may be used at slightly elevated temperature, including general use of printer paper. However old type of advertisement chalk paper is best, and it is not disturbing if it previously had been printed in printery. Printery color stays with it and not being transferred.
    So, when DIP tech, use an ironing and paper, when use a SMD, then only Positiv+ aerosol gives a accuracy good enough without of spiner. Spiner I use if I work with polyvinylalcohol - as it is cheaper than positivus but gives the same sub-micrometer resolution, I use if I have larger stok of pcb to work on. But for just one or few it has too much time to loss, with Positivus it is faster, cleaner, simpler, and more warranted result.
     
  11. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    Happy New Year, Les....long time no see!
    I have been experimenting with a number of semi-modern PCB fixin' methods. For one off applications, I still like plain old etching...mainly because the alchemist in my loves playing with vile roiling potions. It takes a lot less setup...(read "thought")... to throw together a hand-etched board than some other methods. Anyway, it's a skill the young whippersnappers need to know about anyway.

    73!
    Eric


    x
     
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  12. cmartinez

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    Jan 17, 2007
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    KL, unfortunately, Les hasn't logged in for than 6 months already.
     
  13. KL7AJ

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    Nov 4, 2008
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    Rats....I hope he's doing okay. He's always been an AAC "Great One."
     
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  14. ROB2019

    New Member

    Apr 5, 2019
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    Hi,

    I enjoyed your article on the Photographic methods of making PCBs. You made your own UV LED exposure light. I am trying to do the same and would like to know how you secured your high power UV LED to the alumina heatsink? Did you use heatsink adhesive only or screws as well?

    Any info you can share would be greatly appreciated.

    Again, great article.

    Regards,

    Rob
     
  15. Mosaic

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    Aug 2, 2010
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  16. Janis59

    Active Member

    Aug 21, 2017
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    RE: Rob1019 ""You made your own UV LED exposure light. I am trying to do the same and would like to know how you secured your high power UV LED to the alumina heatsink? ""

    Those 3W diodes are glued to 6-angular aluminium platelets about 15x15 mm, what are mounted in stripes. Both ends of stripes have an M3 nitting in holes, thus I brought some aluminium face-plate from older decommissioned apparatus 7mm thick, cut the A4 sized piece with not too big holes, and screwed the stripes in both ends. In one stripe I used 5 LEDs, and number of stripes is about 11. In corners of face-plate I drilled holes where four feets of 20cm long are positioning light source on table. All LEDs are switched in series and goes to the 220V mains via corresponding 20W large sized resistor. Firstly I tried the ballast inductor from Hg long-lamps, but after third burned LED I throw this out and substituted to purely resistive ballast. From that time I had no trouble about burned-out LED.
     
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