Ebay Classic organs

Collapse

Announcement

Collapse
No announcement yet.

Making PCBs

Collapse
This topic is closed.
X
This is a sticky topic.
X
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Making PCBs

    Is this the forum formerly known as the Electronics Forum? I sure hope so.

    Some discussion in the Hammond Forum has come up recently about making PCBs. I thought I would post my technique here. I have been using and refining this since I was in high school; it's how we did thinks in electronics lab.

    Materials Needed
    - Ammonium Persulphate crystals
    - Water
    - Copper-clad PCB
    - Drill press
    - Tungsten-carbide PCB drill bit kit
    - Laser Printer (or photocopier)
    - Regular printer paper
    - Access to a sink
    - #000 steel wool
    - Masking tape
    - Iron
    - Pyrex pie plate with resealable lid (never cook in again)
    - Toaster oven (kitchen one is okay)
    - Aquarium air pump
    - PCB layout software

    Layout with ExpressPCB
    The software I use is http://expresspcb.com/ExpressPCBHtm/...d_software.htm .. This software can produce drawings for the fab facility that Express PCB uses, or it can "print preview". I haven't done this in a while, but IIRC the procedure is basically, lay the schematic you want to build out using ExpressSCH. Get happy with it. Then make a new PCB in ExpressPCB and link your schematic to it. Lay each part out on the screen, remember to use the netlist feature to insure that your layout matches your schematic. If you want to make a single-sided board (recommended), just use a double-sided board and only put components on one side. Then you can use a via and a trace on the other side help you jump over traces in your layout and keep things tidy. When it's time to build the board, just use a jumper wire on the back of the board in place of a trace. This also means you don't have to figure out how to plate vias...

    Now that you have laid your PCB out in ExpressPCB, you need to get it out of there. Print just the copper on the back side of the board. I used some kind of print driver to give me a TIFF file, you could probably also print to PDF etc. Then I load the file up in Photoshop and get rid of the dots, by using "select by colour" or something like that. Then I can touch up the board in photoshop, write my name on it or whatever, turn it into a black and white (no grey!) image and flip it to make it a mirror-image. Also, make sure the image will print out at the correct size, you may need to play with Image->resize and a calculator. For best results, do not change the number of pixels, just alter the DPI. Next, I print the image out on my laser printer (MUST be laser). If your printer or print driver has settings for how much ink to use, set it as dark as it will go, you want as much ink on the paper as possible.

    Make sure that whatever layout software you use that the copper lands have the holes for the pins in them, you will need this to guide your drill later.

    Transfer etch-resist pattern to PCB
    Pull the PCB out of the package and lightly "sand" the copper with #000 steel wool in criss-cross directions. Now you take your mirror-image of the copper, and tape it, face-down, to the copper side of the PCB. The ink will be transferred to the PCB and wherever the ink is, copper will stay. I like to use 1/16" copper-clad FR4 epoxy PCBs with 1 Oz copper coating, such as MG Chemicals #506. A 4x6" board costs $7.

    Now, get your iron, and make sure there is NO water in it. Plug it and set it on the hottest temperature (wool/cotton/linen?) that it has. Make it gets really really hot. Now, iron the paper onto the PCB. Push down really hard, and iron until you scorch the paper light brown. Now, we go over to the sink and simply wash the paper off the PCB with cold water, leaving the ink behind. Use your thumbs to help. Don't worry about leaving paper hairs in the ink. Do worry about getting all of the paper off between traces, in copper land holes, etc.

    If you somehow screwed up the iron-on process and there problematic traces, you can fix them with a Sharpie. Use lots of ink. Or an expensive etch-resist pen, your choice.

    Making an etching tank
    An etching tank is just a place to hold etchant. It will work faster, and you will get better results, if you have a way of agitating the tank and warming the etchant. I use a Pyrex pie plate (you can't use anything metal) to hold the etchant, and I warm it by sitting it on top of the toaster oven. Actually, a Black and Decker Toast-R-Oven. Put it on broil, sit the dish on top of (not inside) the oven and it will keep the etchant around 25-30C. That's plenty. A hot plate, anything like that will work.

    A fish tank air pump can be used to agitate the solution. Rig the plastic hose up so that it makes bubbles that cross the PCB. Remember to put the pump above the tank so that tank doesn't drain into it.

    You will want something to get the PCB out of the water that is not metal. You can drill a hole in the PCB and put a string in it, or you can use a couple of plastic forks..whatever. Even your hands will work if you wash them right after.

    Etching the PCB
    So, you mix up your etchant and put into the tank..you want a couple of inches of etchant in there. Measure the water you used and figure out how many crystals to use based on the container. Remember 1000mL of water (4 cups) weighs 1Kg (2.2 lbs). If you have a buddy with a "postage" scale that would come in handy. I used a balance made out of a piece of dowel and a ruler, with a measuring cup full of water for weight. Once you figure this out once, write it down. Crystals last a long long long and if the water evaporates, just add more water. You will notice after a dozen boards or so that etching is starting to get slow...that is when it is time to change the etchant.

    The etchant I use is MG Chemicals #410. A 1Kg container will make about a hundred hobby boards. Maybe more, depends on your board layout (hint: large ground planes leave copper behind - the more copper you leave behind, the fresher your etchant will be)

    Click image for larger version

Name:	MG-Chemicals-410-1KG.jpg
Views:	1
Size:	7.0 KB
ID:	610520

    Mix your etchant (see above), drop the board in. Turn on the heat and the bubbler and wait awhile, but not too long. The board is done when all the copper that is not under the ink is gone, but before the ink has been eaten through.

    Drilling the PCB
    Use tungsten carbide drill bits in a drill press. The bits are very delicate and do NOT like any lateral motion. They are also very sharp and will make quick work of your PCB. Remember, etch your boards so that the holes in the lands are already clear of copper. Lower the drill with your right hand and position the board with the other. Use a sharp, tungsten-carbide PCB drill bit, and use your hand on top of the PCB let it wobble a bit. As you lower the drill, the hole etched in the land will center the drill bit if you get your left-hand pressure just right.

    Click image for larger version

Name:	800px-Box_of_02in_pcb_bits.jpg
Views:	1
Size:	101.8 KB
ID:	610519

    I use a Mastercraft drill press..works really well, worth a couple of hundred bucks. You can get fake drill presses that work with your corded drill for $30. They work okay. A dremel drill press with a foot control work probably work well, too. A proper drill press is especially nice because the light and the shadow of the drill bit help to guide it, improving your accuracy. I've never tried one of those laser-guided jobbies.

    Click image for larger version

Name:	attribute_image12776.jpg
Views:	1
Size:	61.4 KB
ID:	610521

    Silk screen layer
    Print the silk screen layer from Express PCB. Repeat the process we used for the copper side, but iron onto the bare side of the board this time. To line up the paper accurately, poke holes in two or three vias, and use the drill holes to line everything up. If you have paper hairs in the ink, you can lightly sand with #000 steel wool, or just colour them black with a Sharpie

    Remove the resist
    Steel wool until it is gone...

    That's it. Now you are ready to stuff with components and solder! Some people like to tin PCBs...I generally don't bother.
    Last edited by Wes; 12-02-2013, 02:44 PM.

  • #2
    New post to avoid attachment limit... I made this stuff in ExpressPCB years ago:

    Resist layer:
    Click image for larger version

Name:	pcb_resist_95dpi.gif
Views:	1
Size:	12.2 KB
ID:	590724

    Silkscreen layer:
    Click image for larger version

Name:	pcb_silkscreen_95dpi.gif
Views:	1
Size:	12.3 KB
ID:	590726

    Schematic:
    Click image for larger version

Name:	Implementation-Schematic.gif
Views:	1
Size:	28.0 KB
ID:	590725

    Here's what it looked like in ExpressPCB:
    Click image for larger version

Name:	pcb_layout.gif
Views:	1
Size:	22.1 KB
ID:	590727

    Here's a nearly finished product - etched but not drilled or stuffed:
    Click image for larger version

Name:	172615.jpg
Views:	1
Size:	33.9 KB
ID:	590728

    That last picture reminds me, this stuff can be hard to cut to size! I used a dremel too for that. Now I use a table saw or chop saw with a carbide blade. We used a band saw in high school, that worked even better.

    If you have any questions, please let me know. If you find this thread unhelpful, please let me know why, don't just vote.

    Wes

    Comment


    • #3
      Wow, Wes, that's a very comprehensive and well illustrated article on how it's done. Thanks for the contribution. I'm going to make it a sticky for now, but will eventually copy it to the Wiki.

      I have to say in all honesty, though, that etching and drilling PCBs at home is a lot mess and work. Been there, done that and won't ever do it again. The boards I used back then had photo-sensitive resist. The etchant that I recall using back in the day was ferric chloride, nasty, corrosive and environmentally unfriendly stuff. The cost of PC boards in prototype quantities is much less today than it was 30 years ago, so I let the pro's do it. For one-offs, I'll just do point to point wiring on perf board.
      -Admin

      Allen 965
      Zuma Group Midi Keyboard Encoder
      Zuma Group DM Midi Stop Controller
      Hauptwerk 4.2

      Comment


      • #4
        Thanks, Admin. I used to help my father ruin my mother's pie plates with Ferric Chloride in the early 80s. That stuff really IS messy. I also don't miss taping traces and lands one bit!

        GuitarBro mentioned in the other thread, "ITEAD is really cheap, only $25 for a 10cmx10cm double layer board. but shipping from china take a few months" -- that's actually about my cost for a homemade board, really great if you don't mind the time lag! I'm glad he pointed them out.

        What I like about PCBs is that they are fast to make once your have the process down, and it saves debugging on perf-board. For some reason I am really good at making assembly mistakes...having ExpressSCH/ExpressPCB marry up netlists is a very large QA step. I also feel more comfortable running power through heavy traces, which are a bit easier to do when you can etch the board yourself. And you can "think out" any sections of the circuit which matter for RF or audio reasons ahead of time a bit better.

        Some day there will be a free program that will let me cut/paste pieces from a SPICE simulator into something like ExpressSCH/ExpressPCB, hopefully with autorouting capabilities...that will be REALLY nice. If that ever happens, I may just have to buy a plotter and modify it to work with etch-resist pens, or maybe just get a CNC setup if the prices fall low enough.

        Wes

        Comment


        • #5
          Originally posted by Wes View Post
          Some day there will be a free program that will let me cut/paste pieces from a SPICE simulator into something like ExpressSCH/ExpressPCB
          I think Eagle CAD can import/export LTspice net files. I don't know if that is just the nets or the entire schematic. Eagle also has an auto router but its pretty bad.
          By the way, great post!
          '60 RT-3
          '69 Leslie 147RV
          '77 Yamaha E-70
          '4x Conn Connsonata 2A2
          '6x L-133A

          Previous:
          '5x M2, '59 Leslie 25, '48 CV, '64 A-102, '6x M-143, '5x M3, '81 kimball stardust,
          '8x Hammond Aurora, A-102, M2, another M2, Wurlitzer spinet, Wersi DX350, Thomas chordian

          Comment


          • #6
            Originally posted by Wes View Post
            Thanks, Admin. I used to help my father ruin my mother's pie plates with Ferric Chloride in the early 80s. That stuff really IS messy. I also don't miss taping traces and lands one bit!

            GuitarBro mentioned in the other thread, "ITEAD is really cheap, only $25 for a 10cmx10cm double layer board. but shipping from china take a few months" -- that's actually about my cost for a homemade board, really great if you don't mind the time lag! I'm glad he pointed them out.

            What I like about PCBs is that they are fast to make once your have the process down, and it saves debugging on perf-board. For some reason I am really good at making assembly mistakes...having ExpressSCH/ExpressPCB marry up netlists is a very large QA step. I also feel more comfortable running power through heavy traces, which are a bit easier to do when you can etch the board yourself. And you can "think out" any sections of the circuit which matter for RF or audio reasons ahead of time a bit better.

            Some day there will be a free program that will let me cut/paste pieces from a SPICE simulator into something like ExpressSCH/ExpressPCB, hopefully with autorouting capabilities...that will be REALLY nice. If that ever happens, I may just have to buy a plotter and modify it to work with etch-resist pens, or maybe just get a CNC setup if the prices fall low enough.

            Wes
            Hi Wes,

            Very impressed with your new thread on making PCBs, It’s refreshing to see that people are out there still building things. It seems that hobby electronics is going out of fashion in this throw away world we live in.

            You say that Ferric Chloride is messy; it’s also rather dangerous stuff as well. Some 35 years ago I was etching a new PCB when by accident, I dropped the PCB back into the bath of Ferric Chloride and the stuff splashed up into eyes. I put my head under the tap and blasted water into my eyes, but the burning in my eyes seemed to get worse. A friend of mine bundle me into his car and rushed me to local eye hospital luckily only a mile or so away. They quickly had my in the treatment room pouring counteracting solution into my eye and that was wonderful, at last the burning stopped. I was very lucky not to have damaged my sight. I should have been wearing safety glasses, but at time I just didn’t see the danger. It didn’t stop my making my PCBs and I’m still making them now.

            Keep up the good work.
            Ken

            Hammond A100, Leslie 760 and a Yamaha PSR S710.

            Comment


            • #7
              Thanks for that note, Ken. In high school -- a safety-conscious environment even 25 years ago -- we were required to wear smocks and face shields when we wanted to pull boards and in and out of the tank. ANY etchant splashed into your eyes is potentially very dangerous, as it is a powerful acid. I have seen folks etch boards with battery acid, muriatic acid, etc.

              Folks, heed Ken's words, safety glasses would be the smart thing here!

              Speaking of safety -- you should also drill a small hole in the lid you keep your solution in, in case there are H+ ions still forming when you put it away. A hydrogen explosion propelling etchant around would suck.

              Wes

              Comment


              • #8
                Originally posted by Wes View Post

                That last picture reminds me, this stuff can be hard to cut to size! I used a dremel too for that. Now I use a table saw or chop saw with a carbide blade. We used a band saw in high school, that worked even better.


                Wes
                A method I have used to cut circuit boards with good results is a 1/16" carbide router bit in a router table. I run the board against the fence to get a straight cut. The edges come out glass smooth with only a small burr. You can easily remove the burr with a file or some abrasive paper. You can get the router bits from Drill Bit City for about $2.50 each. Once I cut up two 14" x 10" panels into 288 small circuit boards using this method.

                Best regards,
                Andy Hall
                Allen TC-3S, Rodgers 321, Rodgers 660, Rodgers 990

                Comment


                • #9
                  Copper-clad boards are available with a full raster of holes already drilled. Is it possible to set your layout tool to utilize such boards? (I think the holes are on a 1/10" grid, matching IC socket spacing.) That would eliminate the need to do any drilling. The traces would need to go between the rows of holes, though, or the etchant would work from the back side on the traces.

                  David

                  Comment


                  • #10
                    Great post - I do something similar myself - the only main difference is the PCB software, I use the KiCad suite. So no need for the Photoshop stage. Yes it's time-consuming and fiddly but if you've got the time, very satisfying to do it all yourself.

                    I use a tiny hand-held drill which is quick and easy. (The problem with fixed spacing of 1/10" is that it won't accommodate some devices and in particular things like PCB-mounting connectors eg for USB.)

                    Comment


                    • #11
                      David - I had no idea pre-drilled copper-clad PCB was available. Interesting. The software I use doesn't support it, but you could probably lay out the board by hand to take advantage of it, by setting the grid points at the right spacing.

                      Adhall - Wow, that's a great idea. It could be much safer than my current technique, and definitely better than using a dremel. I have been meaning to get a router for some time. Yet another use for it when I finally get one!

                      Winelight -- Thank you for the software pointer! This did not exist 10 years (or so) ago when I last did my survey of the field. I will try KiCad the next time I make a PCB. A quick survey suggests this will work even better for me than ExpressPCB/ExpressSCH once I pay for the learning curve. Availability on Mac/Linux and the elimination of the PhotoShop step is a big deal. "Schematic capture", provided it has something like the ExpressPCB/ExpressSCH integration will do the trick. The direct tie between the PCB layout and schematic drawing is the "killer feature" for me.

                      Wes

                      Comment


                      • #12
                        Originally posted by Wes View Post
                        The direct tie between the PCB layout and schematic drawing is the "killer feature" for me. Wes
                        DipTrace is very good that way. You make the schematic in the Schematic part, then open it in Layout, it will lay it out for you, and do the traces.

                        Free too, up to a couple hundred connection points.
                        Mark Sutin

                        Comment


                        • #13
                          KiCad is the same... make the schematic, then assign modules (physical packages for the individual components), then do the layout. It will do auto-routing but I haven't used that. Prefer to do it myself.

                          Comment


                          • #14
                            Although not exactly On Topic, for anyone with simple needs for circuit boards, Radio Shack has several prototyping PCB boards available that permit positioning several ICs and other components using some prepared traces and some point-to-point wiring. I have successfully used a couple of them to build some special circuits for my Schober Recital Model organ. I'm attaching some photos of a couple of the blank boards. Also a picture of one of them as used.

                            David
                            Attached Files

                            Comment


                            • #15
                              Hi, David!

                              RadioShack doesn't exist in Canada any more -- and even when it did, they stopped carrying those small boards more than a decade ago. I really loved them, I have built many projects on them, including my first accidental AM radio (LM386 high-gain amplifier with no input connected). I actually kept my last one so that I could replicate it one day!

                              The white one in your photo, I have used before to transfer projects from breadboard to PCB - a handy layout that decreases errors for that use-case. One thing that always frustrates me is that I have never seen perf board laid out for op-amp circuits. Three power rails would be very handy!


                              Wes

                              Comment

                              Working...
                              X