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Making PCBs at home — Parallax Forums

Making PCBs at home

LeonLeon Posts: 7,620
edited 2012-04-25 09:37 in General Discussion
PCBs with tracks as narrow as 8/8 mil (8 mil width with 8 mil spacing) or even less are easy to make at home with inexpensive equipment. I use an HP 9540 printer to print transparencies that are used with positive pre-sensitised PCB material in a simple UV exposure unit. After exposure the board is developed, etched and then drilled.

Printing

I use the HP 5940 printer because it is comparatively cheap, it can deliver 1200 dpi output directly from the Pulsonix PCB software I use, and it works well with the JetStar Premium film available from Mega Electronics (UK).

I print on an ordinary sheet of A4 paper initially, cut a piece of film a bit oversize (it's expensive), and stick it to the A4 printout with a piece of masking tape. The matt surface of the film must be uppermost. It goes into the paper input tray with the film on the underside, and the tape towards the back of the printer, in the feed direction.

Print the artwork using the best quality setting, and cut it to size. I mainly make single-sided boards, the artwork has to be reversed for a through-hole board with the copper on the bottom.

Exposure

Cut the PCB laminate to size and remove the protective black film. I use Mega Electronics FPC 16 material as it's very easy to cut and drill, unlike the more usual FR4.

Place the sensitized side of the laminate in contact with the transparency (ink side against the resist) and put it on the exposure unit. Switch on the lamps and leave it for the required exposure time. This needs to be established beforehand using test strips, as was done with photographic enlargers.

Remove the laminate, and develop it.

Development

I use caustic soda (sodium hydroxide) solution (about two teaspoons to a litre of water), and it takes about 30 seconds to remove the exposed resist with constant agitation in a small plastic container at room temperature. Wear rubber gloves.

Etching

I use warm ferric chloride solution for etching, it lasts a long time and can be used until it is exhausted. It's usually supplied in powder form. Follow the instructions when making up the solution.

Put about 1.5 cm of ferric chloride solution into a suitable plastic container, and place the container in an old washing up bowl with about 2.5 cm of very hot water in it. I use boiling water straight from the kettle. Put the laminate into the ferric chloride and rock the container, wearing rubber gloves. The board should be etched in about 5 minutes.

Remove the board from the solution, rinse thoroughly in clean water, and dry. It's now ready for drilling.

Double-sided boards

Double-sided boards can be made by sticking the top and bottom transparencies together along one edge, ensuring that the two sides are properly registered. The double-sided laminate is then placed between the two transparencies, and each side exposed in turn. With care, reasonable results can be obtained. I prefer to make single-sided boards, with a few wire links on the other side.

UV exposure

Here is a photo of my home-made UV exposure unit:

http://www.leonheller.com/Photos/UV%20unit.jpg

A sheet of ordinary window glass cut to size rests on the wood strips.

It takes 12 minutes to expose the laminate I use.

Removing ferric chloride stains

FeCl3 stains clothes, and anything else, badly. Oxalic acid deals with the stains quite well - make a solution with water and soak the stain. Wash the item. Oxalic acid is available on Ebay, it's used for whitening wood. It's rather toxic, don't drink the solution.

Suppliers

Mega Electronics (UK) supplies JetStar and JetStar Premium film, as well as LaserStar film for laser printers:

http://www.megauk.com/artwork_films.php

I also use their FPC 16 laminate:

http://www.megauk.com/pcb_laminates.php

I actually buy it from ESR, as they don't have a minimum order charge:

http://www.esr.co.uk/

Farnell sells something similar, but I don't find it as good as the material sold by Mega. Farnell also sells the film:

http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=WZBJEPFICXA44CQLCIQZMMQ?N=0&Ntk=gensearch&Ntt=jetstar&Ntx=mode+matchallpartial&suggestions=false&ref=globalsearch&_requestid=453190

Please ask if anything needs clarification.
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Comments

  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-02-12 11:21
    Just make sure the kiddies know that sodium hydroxide and ferric chloride are kinda nasty things. You probably don't want to just dump them down the drain as-is, especially if you have your own well.

    200px-GHS-pictogram-acid.svg.png
  • LeonLeon Posts: 7,620
    edited 2012-02-12 11:23
    Sodium hydroxide is OK down the drain, it's used as a drain cleaner. Ferric chloride is used by the water companies, but they won't like the copper.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-02-12 14:11
    How does one dispose of the copper solution?

    My concern about disposing of the waste chemicals has kept me from making PCBs at home.

    BTW, it's now very difficult to purchase NaOH(in USA). They used to sell it in the grocery store, now I have to by it off eBay.
  • LeonLeon Posts: 7,620
    edited 2012-02-12 14:23
    Here in the UK it can be taken to the local council rubbish dump, they have a collection point for toxic waste. Small amounts can be poured down the drain with plenty of water, the copper content will be minimal.

    The solution can be regenerated with hydrochloric acid and hydrogen peroxide, or by bubbling air through it, and will gradually become cupric chloride, which is a good etchant in its own right.

    Developer which doesn't contain NaOH can be bought, but it's expensive.
  • tonyp12tonyp12 Posts: 1,951
    edited 2012-02-12 14:45
    Can not someone come up with inkjet graphene, so you can print your traces.
  • LeonLeon Posts: 7,620
    edited 2012-02-12 16:00
    Do you mean printing directly on the copper?
  • tonyp12tonyp12 Posts: 1,951
    edited 2012-02-12 16:35
    No, I mean printing the traces directly (maybe a few passes) on a substrate.
    A google search shows that is not far fetched.
    http://www.extremetech.com/extreme/106599-first-inkjet-printed-graphene-computer-circuit-is-transparent-flexible
  • Erik FriesenErik Friesen Posts: 1,071
    edited 2012-02-12 18:31
    http://techref.massmind.org/techref/pcb/etch/c84-st.htm
  • tonyp12tonyp12 Posts: 1,951
    edited 2012-02-12 18:48
    I'm not talking about printing a mask on copper and then etch.
    I'm talking about printing the “copper trace” itself, actually graphene that is electrically superior to copper.
  • LeonLeon Posts: 7,620
    edited 2012-02-12 19:19
    I've never heard of anyone using that technology at home. Additive processes using copper deposition are used for fine-line PCBs (< 5/5 mil), but require lots of processing steps and aren't suitable for home-made PCBs.
  • lardomlardom Posts: 1,659
    edited 2012-02-15 13:47
    My guess is that you would have to make a few mistakes before you get a two sided board right.
  • LeonLeon Posts: 7,620
    edited 2012-02-15 14:38
    I've made a few, it isn't difficult.
  • BeanBean Posts: 8,129
    edited 2012-02-15 16:14
    If you are going to drill after you etch, make sure you have a large ring. Otherwise the bit will tear the ring off the board.
    I try to drill before I etch if possible.
    Bean
  • Erik FriesenErik Friesen Posts: 1,071
    edited 2012-02-15 16:51
    I have done some double sided boards using the inkjet method similar to described above. It isn't that hard, especially compared to the toner method. You can line up your artwork before hand, and then tape it to the board.

    @Leon, some links to known good products could be useful.

    I suspect that roughed up laser transparencies would work.
  • LeonLeon Posts: 7,620
    edited 2012-02-15 18:28
    I've added some links.

    Bean,

    I use tungsten carbide drills, running at 15,000 rpm, and don't have any problems with pads coming off, even with small annular rings. I often use teardrops for added support.
  • LeonLeon Posts: 7,620
    edited 2012-04-07 21:00
    Here is one of my boards. It's part of a high-performance direct-conversion radio receiver.
    dc_rx1.jpg
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    dc_rx2.jpg
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    dc_rx3.jpg
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  • average joeaverage joe Posts: 795
    edited 2012-04-07 21:16
    I just read graphene and had to post on this because I was thinking about that a while ago! I read a few things on the way people are producing it, and it seems like a GREAT idea.. Someone should work on that!
  • LeonLeon Posts: 7,620
    edited 2012-04-07 21:28
    I don't see the relevance of graphene to PCBs. Do you have a link?
  • LeonLeon Posts: 7,620
    edited 2012-04-07 21:45
    Here is another board of mine:

    http://webspace.webring.com/people/jl/leon_heller/msp430.html

    It was made a long time ago, using a laser printer and tracing paper.
  • average joeaverage joe Posts: 795
    edited 2012-04-07 22:36
    Sorry if it's not relevant but Graphene and Graphyne have AMAZING properties. If we can make transistors and capacitors out of the stuff, why not entire systems.
    http://physics.aps.org/articles/v5/24
    http://hardware.slashdot.org/story/11/11/26/0439205/uk-university-creates-first-inkjet-printed-graphene-circuit
  • jmgjmg Posts: 15,184
    edited 2012-04-08 00:17
    Leon wrote: »
    Exposure
    Place the sensitized side of the laminate in contact with the transparency (ink side against the resist) and put it on the exposure unit.

    Has anyone tried this sort of UV exposure box, using LEDs ?

    http://s.eeweb.com/members/circuit_projects/blog/2012/01/26/ultraviolet-exposure-box-using-LED-1327597271.jpg

    or this
    http://www.electronics-lab.com/projects/mcu/018/index.html

    and I see Mouser has UV LEDs at tolerable prices ?

    VAOL-5GUV0T4 405nm 160mcd 30deg 100: $0.438
    ( 2,910 In Stock)
    VAOL-5GUV8T4 385nm 80mcd 30deg 100: $0.571
    ( 2,579 In Stock)
  • LeonLeon Posts: 7,620
    edited 2012-04-08 00:24
    I know of people who use them and they work OK. UV tubes are cheaper (they were when I checked a few months ago, at any rate) and less work is involved in mounting them. I've got a feeling that UV tubes are better for narrow tracks because of the increased collimation, but I could be wrong.
  • pik33pik33 Posts: 2,399
    edited 2012-04-08 00:47
    In "good old times" (30 years ago) I made my boards at home like this:

    - draw a board scheme on a paper with pen
    - wrap a board with this paper and drill holes
    - get a waterproof lacquer and a pen (old kind of pen used to write with ink on drawing paper in these times) and draw lines on board with this pen
    - treat a board with FeCL3
    - use a solvent, then a home cleaning detergent to clean PCB
    - ready :)

    FeCl was hard to get (Poland, 198x) so I experimented with solutions made from h2o2, vinegar and salt, it worked :)
  • average joeaverage joe Posts: 795
    edited 2012-04-08 01:09
    I have a couple boards someone bought from RS for me. I have never done anything with them and they are wasting away. A process I was PLANNING to use and read a bit on involves printing schematic on !*MATTE*! photo paper with LASER... Then iron onto board to create resist. Dampen paper and continue applying heat until ink separates from paper. I did a test transfer and it worked. Never did etch the board though. Not the most elegant but should work. Eventually I would like to do photo-resist work, but need a darkroom first :(
  • LeonLeon Posts: 7,620
    edited 2012-04-08 01:10
    pik33,

    I made my PCBs the same way when I started playing about with electronics at home. I used to paint the tracks with cellulose paint and a fine paintbrush.

    Joe,

    A darkroom isn't required for photo-etch.
  • average joeaverage joe Posts: 795
    edited 2012-04-08 02:04
    Very true, but a workshop would be a big help. A one bedroom apartment makes a poor lab. Especially with a 3 month old. Soldering is done in the bathroom, and any chemical work is done outside in the dirt with spill collection procedures.
    I have seen examples of people using simple CAM machines using stepper motors and a dremel. I've thought about one of these quite often, but do nowhere near the volume necessary to justify the price of one. Could be built DIY IMO.
    http://youtu.be/gZFvra3kXEs
  • LeonLeon Posts: 7,620
    edited 2012-04-08 02:10
    They are slow, compared to the photo-etch technique, and don't produce very good results unless one spends a lot of money. The Pulsonix PCB software I use supports the LPKF prototyping machines, and they are very expensive.
  • LeonLeon Posts: 7,620
    edited 2012-04-08 11:53
    This (rather poor) photo is my latest board. It's a prototyping board for the DIP28 NXP LPC1114 ARM Cortex-M0 chip. They aren't officially available yet, NXP supplies me with samples of new devices in return for running the LPC2000 group. I've also attached the layout, and the schematic.

    I need to remove the resist and drill the board. I'll see if I can get a better photo when I've removed the resist.
    Proto.jpg
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    Proto.jpg
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    pdf
    pdf
    Proto.pdf
    147K
  • jmgjmg Posts: 15,184
    edited 2012-04-08 15:00
    Leon wrote: »
    It's a prototyping board for the DIP28 NXP LPC1114 ARM Cortex-M0 chip. They aren't officially available yet...

    The problem with these DIP offshoots, is they do not cover the newest variants, so the LPC11A14 / LPC11U14 for example, are not showing anything even planned in DIP.

    Also, being wide body, they really have chosen just the hobbyist niche; a SDIP might have more volume but perhaps the die just will not fit ? Lack of wide-supply is another drawback in NXP devices.

    I can also see part codes for DIP24, but no road map mention of these, so do we guess they are pruned for the DIP28 ?
    Not such good news for someone who designed-in a DIP24 ?
  • LeonLeon Posts: 7,620
    edited 2012-04-08 15:19
    It is a bit odd. I prefer the PIC32, which is in a narrow 0.3" package.

    I also asked for some of the SOIC and SSOP ones, but they are having some problems with them.

    .
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