How to make double-sided PCB at home?

Discussion in 'General Electronics Chat' started by nelsonys, Apr 7, 2011.

  1. nelsonys

    Thread Starter New Member

    Apr 6, 2011
    Most of us are able to fabricate one-sided PCB at home using different kinds of methods, be it using photosensitive board, blueprint, wax paper, etc.

    Anyone has any idea or guides in fabricating double-sided board while maintaining great overlapping accuracy?
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    Everything was going great until you used the "A" word!


    That is rather tough to achieve at home.

    What I do, is cut my boards square, and be sure to make registration marks on the layout.

    This will allow you to use the photosensitive method rather easily.

    With the other methods, it can be rather difficult to see through the transfer paper, whatever it may be.

    With the photosensitive method, using transparencies, it is trivial to line up the registration marks with the edges of the board.

    If you are using DIP packages only, you can usually get away with the "Pocket" or "Pouch" methods.

    This is done by taping the front and backside transparencies together on 3 sides, making a pocket.

    Drop your board in the pocket, expose and etch. The thinner the board, the more accurate this method is.

    Measure thrice, etch once ;)
  3. Wendy


    Mar 24, 2008
    Many people drill holes and use them as fudicials. It works, but accuracy is always a problem. Another issue, while you are working on one side, the other side is getting scratched up on its resist. No fun a'tall.

    I've never done this, but you could always paint one side, etch the other, drill holes, then repeat. The holes will help with the alignment.
  4. nelsonys

    Thread Starter New Member

    Apr 6, 2011
    I am thinking of trying something brave.
    One side with SIP and some SMD components, both side compact with traces and ground fill.
    I am going to use printing method. First accuracy problem comes from the printer itself, I may need to do some calibration first.

    Register mark is very important so what would I do is to make two fiducial marks lying diagonally outside the board. Finish with one side etching and drilling then continue with the other side.

    Here comes another problem, the previously fabricated side, I used to use scotch tape to seal it, but after etching process, it was hardly tear off completely from the board. Besides, I am worried that the etchant might sip through those drilled holes and causes the fabricated side to be re-etch again.

    For via holes, I am just going to use a short lead and solder both side together.

    Any ideas or suggestions?
  5. t06afre

    AAC Fanatic!

    May 11, 2009
    If you expose both sides of PCB simultaneous. You will get the best accuracy. But such equipment is quite expensive
  6. jpanhalt


    Jan 18, 2008
    I tape my two transparencies together, nicely aligned, and slip the board between them for exposure. The board and transparencies is clamped between two layers of glass and exposed in the usual manner.

    edit: I etch both sides simultaneously and drill after etching.

    Last edited: Apr 8, 2011
  7. nelsonys

    Thread Starter New Member

    Apr 6, 2011
    But I'm thinking of printing traces on the board instead of photolithography. Print and etch side by side. The registers helps to make alignment as accurate as possible. That's why I have to take care of the printer's tolerance too.
  8. Wendy


    Mar 24, 2008
    Are you talking about the toner transfer method? I have heard of the printing directly on the PCB, but it would be harder to align than any other method I would think.

    The problem with accuracy with the toner method (on my setup) is the toner transfer tends to slide a bit when fusing it to the board, this is a killer.
  9. nelsonys

    Thread Starter New Member

    Apr 6, 2011
    Have you ever used "blueprint" before. A piece of blue paper which one side is for printing layout onto it. Then use an iron to iron the trace directly onto the board.
  10. radiohead

    Distinguished Member

    May 28, 2009
    Blue print also known as "Pray and Peel" can be tricky to use if you don't apply even heat to the transfer film. Any number of errors can occur using this stuff. You can get areas that the toner did not adhere, uneven trace lines, if you use too much heat with too much pressure, and the film shifts even slightly, you will get a shadowing effect. I would advise experimenting with the blue transfer film to find the best results. See the customer comments on this site.
  11. CVMichael

    AAC Fanatic!

    Aug 3, 2007
    This is how I do it:

    I print one side of the PCB on paper (make sure the scaling after printing matches the real size)
    I tape the paper to the PCB board
    Drill the holes through the paper using a Dremel
    Remove the paper
    Clean the PCB using fine sand paper
    I borrow nail polish (color does not matter, but dark color is easy to see on the PCB) from my GF, and draw by had the traces on both sides, using the holes as a reference. If I make mistakes I correct by scratching (removing) the nail polish using a pin (or anything sharp). For big mistakes I use nail polish remover, then sand that area a little bit.
    Let it dry, then I dip it into Ferric Chloride. Wait till it's done. I am usually impatient, so I check on it every few minutes :)
    Remove the nail polish using the nail polish remover.

    That's it...
  12. Wendy


    Mar 24, 2008
    Since you mentioned wax paper I assumed you had read this...

    How I make PCBs

    The problems as I see them is making the pesky transfer paper hold still.
  13. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    That's pretty easy to fix. I use paper laserprint sticker (cut thin like tape) to stick the toner sheet to the PCB at one edge only, then feed that edge into the laminator first to cook it.

    Even with 10 or 12 feeds through the laminator there is no movement. The laserprinter sticker (like they use on mailing envelopes) has glue that is suitbale for laserprinter temperatures and it doesn't move with the laminator heat.

    Obviously the laminator helps a lot too, much better than an iron which moves it all over the place.