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Circuit board - methods to make it — Parallax Forums

Circuit board - methods to make it

AmaralAmaral Posts: 176
edited 2006-01-27 17:09 in General Discussion
Hi All ,· I haven´t looked around so if this an repetead post I apologize.

I trying a method of building Circuit Boards that uses UV light ( I never had used it before, always on hand write ) . And it seems very tricky to get uniform results.

I´m wondering what kind of methods are you all using for building your own Quality Boards ?

( I´m trying a product called PRP and PDN from Electrolube )

Thanks in advance

Ricardo Amaral

Comments

  • denodeno Posts: 242
    edited 2006-01-24 22:38
    Hello...for years I have had good results with the product that All Electronics sells.· Catalog nujmber TEX-5.· Called "Press and Peel".· There are a couple of tricks in using this product.

    1. Do your art work (I used Microsoft's Paint Brush...which took a little set up time to get the right pad spacing between the legs of the IC's voltage regulators and other components) This is .1 inch spacing on IC's.· Print out your pads that make up the various IC's in your project and test by placing the IC or it's socket on the paper to see if the feet line up.· When you get the spacing just right, go to properties and save the attributes of that drawing size so you can always return and have it right.· Connect the pads with lines or traces to make your circuit.

    2. Follow the instructions that comes with the Press and Peel as far as getting the art work from the printed paper to there special paper.· Requires a copy machine that uses toner fluid.· Most print shops have this kind of printer.· Usually, it is a big one that stands 3 to 4 feet off the floor and requires some help from an assistant in the store.· Lots and lots of buttons.·Set the contrast control to one position darker then the standard middle position.

    3. REALLY clean your precut copper board with a dry 3M scrubbie.· Really clean means really clean and don't touch the copper after. Cut out the artwork with sissors from the press and peel (same size as the artwork) and...important...blow all dust off copper surface and the press and peel artwork. DO NOT WASH!

    4. Place the artwork as directed down on the copper...don't touch the artwork or the copper with your fingers.· Hold by the edge.

    5.· Now here is the secret where people that use this process have a problem.· A hot iron is needed, I set it at the "Cotton" setting AND I carefully place a clean dry (one layer) paper towel over the complete assambly.· Be careful not to move the artwork on the copper when placing the paper towel.

    6. With the hot iron, start to rub the paper towel in a cornor or along one side to "lock" the artwork to the copper.· Evendually, go all over the towel portion that covers the artwork/board.· Do this for several minutes, always moving the iron. Do not rub the iron on the blue acitate of the Press and peel directly, or you will make a big mess.· Always keep a portion of the paper towel between the iron and the artwork.

    7. The next secret is....cold water from the facuet.· Holding the copper/artwork assambly on edge under the cold water, take a tooth pick or sharp impliment and just start to seperate the blue artwork from the copper.· When the water finally gets between the artwork and the copper, it will release and fall in the sink.

    8. Thats it...inspect the board for missing traces and touch up if necessary with a fine tip sharpee pin.· The ink in the sharpee is also resistant to the etching acid.· Only once in a while do I have to touch up.· Usually, a touch up is caused by a single piece of lint or dust between the artwork acitate and the copper.· The board and the artwork on it may be dried with the paper towel·and is hard to the touch.· Ready for etching.

    9.· You will need to drill the various small holes in you pads for the thru the hole parts.· And a drill bit of 1/16 is way to big.· The company above sell small drill bits that can be used in a dremial tool.

    The following is a sample of artwork using Microsoft's Paint Brush.

    Hope this helps...using the Paint Brush program will take some expermenting to get the pad spacing right on different IC's.
    BMP
    BMP
    SAT_TRK_DC_SR_LCD_5_2005.BMP
    361K
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2006-01-24 22:59
    I've had some success with Photosensitive boards.

    There are a few steps that are necessary to "calibrate" your environment.
    First get a scrap piece of your Photosensitive board and mark it off like a ruler
    every 1/2 inch or so. Cover ALL but one section of the scrap piece and expose
    the scrap to your light source for 5 minutes. Move the scrap piece so that the
    next section is exposed. Repeat this every 5 minutes until you have a record
    of at least 30 minutes. Now place the scrap piece of Photosensitive board into
    your etching solution. Check this every 5 min until your scrap piece is etched.
    Note: You will (should) be able to see an obvious "sweet spot" where the copper
    is completely gone, vs. still present. Now, as long as your setup does not change,
    you have the correct exposure times that should work on any of your boards.

    Now, as far as transferring the artwork to the Photo sensitive board. ....There are
    a few methods. Ideally you could use a "flat bed printer" and print directly to the
    board but these are hard to come by. My preferred method if I'm doing this myself
    is to print my artwork to Paper on a x2 scale. Then take my printout to a copy shop
    and have a transparency made with a 50% image reduction.

    Once I have a nice transparency, I can place this directly over the Photo sensitive
    board. For better yield I place a piece of glass over the transparency. So it looks
    something like this....


    [noparse][[/noparse]         Glass         ]
-------------------------
[noparse][[/noparse]      Transparency     ]
-------------------------
[noparse][[/noparse] Photo Sensitive Board ]

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.
  • BeanBean Posts: 8,129
    edited 2006-01-24 23:32
    I use and recommend the Pulsar TTS (toner transfer system) product.
    If you buy the "Starter" kit for $129.95 you get everything you need to get started (including the laminator).
    Note that this system only does 0.032" boards and cannot do the "normal" 0.062" boards.
    It's the easiest method I have tried. And I have made boards for the SX48 (0.5mm lead pitch) with success.
    http://www.pulsar.gs/PCB/a_Pages/1_Menu/Overview.html
    Bean.

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    "SX-Video·Module" Now available from Parallax for only $28.95

    http://www.parallax.com/detail.asp?product_id=30012

    "SX-Video OSD module" Now available from Parallax for only·$49.95
    http://www.parallax.com/detail.asp?product_id=30015

    Product web site: www.sxvm.com

    "Ability may get you to the top, but it takes character to keep you there."
    ·
  • SteelSteel Posts: 313
    edited 2006-01-25 00:24
    Generally, I just use Express PCB. They fab your boards, and do all the work for you. You can get 2 Layer (Top copper and bottom copper) boards 3 for $51. It is cheap and process free...
  • denodeno Posts: 242
    edited 2006-01-25 01:05
    Having said everyting in my post above, I have started using ExpressPCB myself and it is easier and much more professional because of the double sided product.· My above method is alot cheaper, but requires more of my time.

    My next PCB project is going to be a surface mount project, but instead of using very small parts, I am going to use regular components, but bend all leads flat to solder on top of the board.· No thru holes, unless the component requires it, like terminal blocks.

    Deno
  • BongoBongo Posts: 65
    edited 2006-01-25 01:43
    I use Kinsten pre-sesitised board.· It's made in Korea, cheap and reliable.· Unless it's a very simple design, I use double sided, as it is nearly the same price as single sided and it is much faster to design with the extra layer available.



    Print on tracing paper and expose for about 10 minutes.· For 2 sides, print one side in reverse, and tape the two prints together so you can slide your board in between, like a sandwich.· Then sandwich between glass and use some weights like a sealed lead acid battery to press things together.· I print on an old HP laser jet, 300DPI.· Have successfully made boards down to 20 thou tracks and gaps, but found hand production too easy to get solder bridges.· So now I use min. 30 thou tracks and gaps, and set the copper planes up for 40 thou gaps.

    It has taken a little time to perfect the process, but I have found that time was a very good investment.· In fact I recently invested in a bubble tank for etching, and now the whole process happens with minimal input from me.





    bongo
  • OrionOrion Posts: 236
    edited 2006-01-25 01:54
    For transferring artwork to the photosensitive pcb, I have good luck with an inkjet and inkjet transparency film.
  • BeanBean Posts: 8,129
    edited 2006-01-25 02:13
    I'm curious what others do about plated thru holes ? I haven't found a good method other than the old "solder a wire in the hole" method.
    Bean.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "SX-Video·Module" Now available from Parallax for only $28.95

    http://www.parallax.com/detail.asp?product_id=30012

    "SX-Video OSD module" Now available from Parallax for only·$49.95
    http://www.parallax.com/detail.asp?product_id=30015

    Product web site: www.sxvm.com

    "Ability may get you to the top, but it takes character to keep you there."
    ·
  • BongoBongo Posts: 65
    edited 2006-01-25 02:43
    Re: Mr Orion, my list of failure with inkjet and transparancy is extensive. Tracing paper rules and is cheaper.......


    Mr Bean, thru plated is possible but is a lot of trouble. It is definately an improvement for industrial strenght boards, but somewhat meaningless on mine. For vias, I bend a bit of wire sharply so it cannot drop out when the solder melts as I am soldering the "other" side.

    bongo
  • OrionOrion Posts: 236
    edited 2006-01-25 03:40
    Re: Mr Orion, my list of failure with inkjet and transparency is extensive.
    ·
    ·
    Really, I just made a 3"x3" pcb with mostly smd and .01 traces without a problem.· I have cooked at least 6 6"x9" sheets of pcb this way with only a few issues, mainly·when I was first getting setup.
    TouchpcbV2noted.jpg
    640 x 480 - 67K
  • OrionOrion Posts: 236
    edited 2006-01-25 03:46
    Bean (Hitt Consulting) said...
    I'm curious what others do about plated thru holes ? I haven't found a good method other than the old "solder a wire in the hole" method.
    Bean.

    Same here and HATE it.· At one time I thought I saw something like a copper·insert with a ring on one side on Jamco or somewhere.· Wire works but seems to melt the solder on the back side and shift a lot.· Sometimes I use a long piece of wire and clip both sides, works like a heat sink.
  • ForrestForrest Posts: 1,341
    edited 2006-01-25 04:04
    Orion, those circuits look good but your drilling accuracy needs some work. I've used a dremel (set to it's highest speed) mounted in a tabletop press and tungsten carbide N/C drill bits work well.
  • KenMKenM Posts: 657
    edited 2006-01-25 04:16
    I have used the photo sensitive method and toner transfer methods with great results.

    Then I discovered expresspcb.com......have more $$ than time and don't bother with making the boards myself.
    Forrest said...
    Orion, those circuits look good but your drilling accuracy needs some work. I've used a dremel (set to it's highest speed) mounted in a tabletop press and tungsten carbide N/C drill bits work well.
    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Ken
  • BongoBongo Posts: 65
    edited 2006-01-25 07:35
    Re: Mr Orion, my list of failure with inkjet and transparency is extensive.
    ·
    ·
    Really, I just made a 3"x3" pcb with mostly smd and .01 traces without a problem.· I have cooked at least 6 6"x9" sheets of pcb this way with only a few issues, mainly·when I was first getting setup.
    **************************************************************************

    I don't usually get into specifics, am a lazy typer.· To expand a little though, my main problems with inkjet/transparancies where probably linked to the wrong product.· Just cause it says on the box "for inkjets........· But even with that resolved, laser is better, and transparancies are not stable at the temperature generated by the laser printers.· I found a big improvment in being able to align holes in large double boards using tracing paper.· It does not distort with the heat.

    As for plated thu holes, my understanding is that they are more resistant to dry joint problems.· Which are themselves linked to heat stress which is not a problem I usually encounter.· They are also mechanically strong, which once again, is not a requirement for me, all my uses seem to be stationary.· If I was to be making an instrument that is destined to rattle around in a tool box, then I would see a need.

    Would also suggest that you leave the photo resist on.· You can solder through it, it will protect the copper from corrosion in the short term.· For long term use, I brush clear estipol over the photoresist.· I tried a spray on solder thru laquer once, it worked well.· However it was expensive and I only got one use out of the can.· Then the nozzel blocked despite following all instructions on said can.

    bongo
  • ForrestForrest Posts: 1,341
    edited 2006-01-25 11:29
    Bongo, where does the heat come from when you're using photosensitive resist and UV light?
  • ElectronegativityElectronegativity Posts: 311
    edited 2006-01-25 18:45
    I'm with Bean on this one, Pulsar TTS has worked very well for me.

    If you use this method I would reccomend preparing the copper surface with extra fine (000 grade) steel wool instead of the scotch-brite pad that the manufacturer reccomends.

    Also, for big boards you might want to send it through by itself once to pre-heat it before the toner transfer step.

    I have had good luck making boards with traces fine enough to solder an SX28SS.

    Haven't had a need to try it on SX48 yet, but I think it would work fine.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    I wonder if this wire is hot...
  • BongoBongo Posts: 65
    edited 2006-01-25 22:50
    Re: Forrest;

    Heat generated in the finished product.· ie power trannies getting dry jointed.· Thru plating increases the soldered area whilst keeping the solder itself reasonably thin.

    bongo
  • OrionOrion Posts: 236
    edited 2006-01-26 01:05
    Forrest said...
    Orion, those circuits look good but your drilling accuracy needs some work. I've used a dremel (set to it's highest speed) mounted in a tabletop press and tungsten carbide N/C drill bits work well.
    LOL couldn't agree more [noparse]:)[/noparse]· I'm using an ultra cheap drill press and hate drilling holes in the first place.· I decided to work more on soldering smd and ditching the holes as much as possible.· It's·easy enough to·bend the pin over on dip parts and solder if the pad a little·messed up.·
  • ElectronegativityElectronegativity Posts: 311
    edited 2006-01-26 16:02
    I just bought this jeweler's drill press from Micro-Mark:

    www.ares-server.com/Ares/Ares.asp?MerchantID=RET01229&Action=Catalog&Type=Product&ID=81631

    In combination with the XY translation table attachment, it really works wonders for drilling precise .02" holes

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    I wonder if this wire is hot...
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-01-26 16:21
    Very cool, an XY positioned drill press for $260, not too shabby.

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    ·1+1=10
  • PaulPaul Posts: 263
    edited 2006-01-26 20:54
    Maybe, the Y direction is only 1.75 inches. I suppose you can reposition it relatively accurately.
    We use an old carboard box with a UV light in it. We make transparencies on the laser printer and put that over presensitized boards with glass on top for 10 minutes. I'll check out the tracing paper idea next time. We also use small copper eyelets inserted into #60 holes for double sided. (you only have to eyelet the holes that go to traces on the top layer, not every hole.)

    --Paul
  • OrionOrion Posts: 236
    edited 2006-01-26 21:21
    Could you post a link to the supplier of the eyelets you use??
  • PaulPaul Posts: 263
    edited 2006-01-27 17:09
    Eyelets: http://www.solder.net/PCB/pcb_repairmaterials.asp

    Pulsar has white TRF foil to make the 'silkscreen' on the top of your PCB look "professional".
    http://www.pulsar.gs/PCB/a_Pages/4_Products/5c_TRF_Foils/TRF_Foils.html

    Post Edited (Paul) : 1/27/2006 5:15:00 PM GMT
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