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Tonerless PCB Templates for UV Exposure

A method for creating long life reusable templates for UV exposing PC Boards

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Templates for producing multiple copies of the same PCB.

The templates should be able to be used indefinitely if cared for properly... Excellent if you need to make the same board(s) over and over again....
This design is made to conform to the UV Oven Project I have going as well...

This project is designed to work with the UV Oven in my projects list.. There are two plates of 1/4" thick borosilicate glass.. 9x6 inches. They are mounted in a 3D printed hinged frame that closes like a notebook on the PCB to be exposed inside and latches shut.. On the inside surface of both plates is a negative of your circuit board pattern.. The pattern is etched into an adhesive aluminum tape adhered to the glass using laser cut adhesive vinyl as an etch resist. In this writeup I will cover how to create the entire device.. The intent is to have a solid, reusable template for each board that you want produce multiple copies of.. the templates should last a very long time..no parts will be susceptible to the UV or heat inside the 'oven'..

Here is a rendering of a pcb placed in between the glass plates before closing it down.. What isn't shown in these renderings is the negative of the pcboard layout (from the image above) layered on the inside of the borosilicate glass plates..

Another angle...

And the frame closed with the board inside..

And another angle...

An a couple exploded views for fun... The frame is in sections to make it easier to 3d print...

This template fits into the UV Oven project like this....

This is cut vinyl before removing the 'negative' bits...

This is after removing the vinyl before etching....

So, as you can see the template should never wear out and you do not have to worry about toner transparencies being so bad that you have to print two of them and stack them.. The aluminum will block 100% of the UV and the borosilicate glass will transmit more of it than transparencies or regular glass...

I guess I forgot to put this same disclaimer on this page that I had on the other...... This goes without saying....

(Make note: cutting vinyl with a laser produces noxious and disgusting fumes and might harm you and/or end your days on this planet..make your family hate you and destroy your life.. Using this method means you understand the health risks and the nasty nature of the chemicals involved and their effects on your well being and peace of mind.....mostly, just make sure you do it in an extremely well ventilated area and don't expose yourself to unnecessary risks... and wear eye protection....!!! Also....most of all, understand that I won't be responsible for you losing an eye or a lung or a family member from misuse of anything involved with this project... =D )

  • Brackets for the 'UV Oven'

    fl@C@04/25/2015 at 05:49 0 comments

    Here's the brackets for the UV Oven Project!

    From the front...

    From above...

    Better front view....

    And with the template only half way in....

    And of course, these files are all in the GitHub repo....

  • Files are in the gitHub!

    fl@C@04/24/2015 at 12:19 0 comments

    The .stl files for the renderings above are now in the gitHub... I'll obviously be adding to them... But I figured I'd put it out there...

  • A little better example..

    fl@C@04/24/2015 at 07:56 0 comments

    This isn't a negative... but it was tested on glass... But this shows the resolution I'm getting using Chilipeppr now.. I'm quite happy...!

  • Example

    fl@C@04/11/2015 at 08:10 0 comments

    So, this probably should be posted in the other project since this is a positive, not a negative for the glass...but I was testing the parameters... this is on glass, but it's a positive image cut... I just wanted to illustrate the traces...

    These are near perfection...

    If you did this on copper instead of the glass like I did here.. this would come out very nice... I'm going to go ahead and try this on copper tomorrow and post it on the other project ( https://hackaday.io/project/3904-tonerless-pcb-etch-resist-direct-to-pcb-method )...

    Getting very close now....

    Just need to get chilipeppr to allow layer selection, allow reversing the layer image, and toggle M3 and M5 instead of moving the Z axis...and it'd be awesome...

    Anyone wanted to help me fork chilipeppr.com's eagle .brd import to do these things...I'll do just about anything.. =)

  • Small update

    fl@C@04/11/2015 at 07:23 0 comments

    So, here's some updated setting I have been using to get better resolution from chilipeppr.... ( this is with my 1watt laser, so the cut speed is pretty high )

    Inflate Milling Path By:
    	positive +0.05
    	negative -0.05
    
    Advanced Inflating
    	Inflate SMDs By
    		positive checked -0.1
    		negative checked -0.1
    	Clip wires
    		unchecked
    	Remove Undefined SMDs
    		unchecked
    	Inflate Pads By
    		checked -0.1
    	Inflate Vias By
    		unchecked 0
    
    Depth of Milling Traces
    	0
    Feedrate for Milling Traces
    	400
    Feedrate for Plunge into Copper
    	800
    Clearance for Z Axis Moves
    	0
    Depth of Cutting Out Dimensions
    	0
    Step Down for Cutting Dimensions
    	0
    Feedrate for Cutting Dimensions
    	400

    And here's slightly upgraded python script that lets you use the input and output names as command line arguments.. Pretty basic still...and it still keys off the cut speed, so I need to find a better way...just haven't spent the time yet...

    import os
    import sys
    
    total = len(sys.argv)
    cmdargs = str(sys.argv)
    
    inputFile = sys.argv[1]
    outputFile = sys.argv[2]
    	
    if os.path.exists(outputFile):
        os.remove (outputFile)
    
    outFile = open(outputFile, 'a')
    with open(inputFile) as f:
        for line in f:
            if line.startswith( 'F400' ):
                outFile.write("M3"  + chr(13) + chr(10))
                print ('M3')
            if line.find( 'G0' ) != -1:
                outFile.write("M5"  + chr(13) + chr(10))
                print ('M5')
            outFile.write(line)
            print (line)
    outFile.close()

  • A little further...

    fl@C@04/11/2015 at 06:37 0 comments

    So, here's some etching into the aluminum I did using the vinyl as a resist layer... I tried various combinations of HCl + H2O2 and ended up going with stragiht HCl ( something like 30% pool variety from home depot )...

    Here is a freshly laser cut layer of vinyl on top of the adhesive aluminum....on a test plate of glass....

    Here is the vinyl bits peeled away to expose the aluminum for etching...(remember this is a negative)...

    And here it is after etching.... My first try, so it's a little sloppy and undercut...the goop from the vinyl being cut should probably be removed with goo-gone or something before etching...acetone doesn't work well on the vinyl...

    Here's the back... a lot of undercutting...I'll work this out later.. ;)

    And this is the light from my monitor shining through the glass plate....

    All in all, I think this is a pretty good proof of concept...the resolution on the TQFP32 is pretty good I'd say... Since these pictures have been taken, I refined the settings a little and have managed to make it even better... Keep an eye out!!

  • Experimenting

    fl@C@04/03/2015 at 22:49 0 comments

    So, here are some experiments I've done with etching the aluminum negative for the glass plate.... I've converted over 100% to chilipeppr.com since it turns out to be awesome... I've been using the Eagle .brd import feature....with the following settings...

    Inflate Milling Path By:
    	0
    
    Advanced Inflating
    	Inflate SMDs By
    		checked -0.12
    	Clip wires
    		unchecked
    	Remove Undefined SMDs
    		unchecked
    	Inflate Pads By
    		checked -0.1
    	Inflate Vias By
    		unchecked 0
    
    Depth of Milling Traces
    	0
    Feedrate for Milling Traces
    	400
    Feedrate for Plunge into Copper
    	800
    
    Clearance for Z Axis Moves
    	0
    
    Depth of Cutting Out Dimensions
    	0
    Step Down for Cutting Dimensions
    	0
    Feedrate for Cutting Dimensions
    	400
    I skip the send gcode to workspace step... copy the gcode from the textbox... I then paste that gcode into a text file...I use a .tap extension... And run a overly simple python script on it to insert my M3 and M5 commands to turn the laser on and off instead of moving the Z Axis.... Here's that code.....it's not great....
    import os
    
    os.remove ('new.tap')
    outFile = open('new.tap', 'a')
    with open("mcu_panel.top.etch.tap") as f:
        for line in f:
            if line.find( 'Z-' ) != -1:
                outFile.write("M3"  + chr(13) + chr(10))
                print ('M3')
            if line.find( 'Z0' ) != -1:
                outFile.write("M5"  + chr(13) + chr(10))
                print ('M5')
            outFile.write(line)
            print (line)
    outFile.close()
            
    I then take the new.tap gcode file it creates (I also remove the dimensions section since I haven't added that to the code yet) and drop it back into chilipeppr.... Hopefully this can be streamlined later...but it certainly works for now...

    This is a TQFP32 for an atMega328.. This is the glass plate with a layer of aluminum tape and a layer of adhesive vinyl on top of that...then cut with a 1w 445nm laser at 400mm/sec... A panel of these goes in about 5-10minutes...

    Here is the same board with the vinyl removed... Take note that this step only has to be done ONCE... After you've done this, then etched the aluminum you'll have a template that can be used indefinitely... Treat it right and you'll never replace it..having used it over and over again...

    A little closer....

    And there you go for now.. I've started the etching experiments... More on that later, but I am using a HCl + H2O2 mixture... It seems a little weak at a 2 part H2O2 and 1 part HCl... Straight HCl is too aggressive... so I'm trying to find a good balance... with the 2to1 ratio, it worked just a little slow. And keep in mind this will also be an automated process with the desktop etching machine I am designing... yay..

  • Design

    fl@C@03/21/2015 at 19:46 0 comments

    So, I'm starting the design for this now... I want it to be sort of like a book where the PCB fits into an area outlined with the gasket material and the glass presses down and forms a tight fit with the PCB in the center...then clamps down.. then the whole thing slides into the 'UV OVen' and gets exposed.. two sides at once.. and if your board is small enough, you can expose several at once.. I'll keep updating the renderings as I get it going.. The frame will be 3D printed, but may have to be either coated in aluminum foil or something to keep the UV from attacking the plastic... I want these to last a long time....through many exposures..

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Jarrett wrote 04/11/2015 at 07:11 point

Which laser, specifically? I might build a similar one based on the CoreXY system

  Are you sure? yes | no

fl@C@ wrote 04/11/2015 at 07:15 point

It's up to $18 now it looks like.. but here it is...does an amazing job really...and a super fine point... pretty cool for the price..

http://www.ebay.com/itm/131178374419

I also tried this thing... 1w 445nm..  

http://www.ebay.com/itm/Real-1W-1000mW-Focusable-445nm-Blue-Laser-Moudle-Blue-Laser-Beam-12V-TTL-and-PSU-/261047937152?pt=LH_DefaultDomain_0&hash=item3cc7ab6880

Does a great job and lets you cut faster... :)  way faster...

  Are you sure? yes | no

Jarrett wrote 04/11/2015 at 06:51 point

Vinyl bad! Cutting it with the laser cutter releases chlorine gas, don't do that!
It'll kill you, but even worse, it'll severly damage the optics of your machine.

  Are you sure? yes | no

fl@C@ wrote 04/11/2015 at 07:06 point

Yes..  The Chlorine gas is nearly as bad as the HCl or Ferric Chloride, etc...and their associated fumes, etc..  A good vent hood or other ventilation system is recommended for every part of this procedure...  the gasses coming from cutting the vinyl as well as etching the aluminum/copper are bad stuff... I wouldn't recommend this for your kids..  And, as I'm using a $15 eBay laser, the optics are pretty replaceable...  

  Are you sure? yes | no

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