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Wondering about the proper steps from prototyping to PCB board.

Discussion in 'PCB Layout, Design and Manufacture' started by Ehsan, Jun 27, 2014.

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  1. Ehsan

    Ehsan

    100
    1
    Jun 12, 2014
    Ok this is the scenario :

    I setup my circuit on a breadboard. After weeks of tinkering I reach to the point of satisfaction, then I grab my PCB board design software, draw the schematic and send the final PCB document to a factory.

    After getting my PCB board, I solder the components, and switch the power on. Alas ! It ALWAYS DOES NOT work !

    I usually take the components off from that already built breadboard design. Now I have a PCB board that somehow does not work and I also do not have that already working breadboard !

    On PCB board I can't measure currents but only voltages, so I check here and there and look for short circuits and etc.. then I desperately replace some suspected components; After lots of failed attempt I give up and again have to set up the circuit in breadboard... and this cycle goes for a lot of times until I get a working PCB.

    How about you ? How do you do this procedure properly ?
     
  2. OLIVE2222

    OLIVE2222

    690
    25
    Oct 2, 2011
    How many iterations are needed to get a working PCB is highly depending on both the design complexity and the designer skills/experience, yep obvious.
    It's can be a pain when you begin, but that's the learning curve, same to become a good carpenter or anything!
    Having a first PCB with a bit of rework is quite OK to me.

    For High frequency or high density SMD package designs breadboarding usage is excluded you need so to start with mockups based on existing (evaluation) boards, adapters boards and/or to directly go for a PCB.
    Better to check twice that the schematic EXACTLY match you breadboard implementation.
    Use the PCB board software design rules check to ensure that you PCB EXACTLY match you schematics.

    Even if it's work on breadboard you can design your PCB to be a bit more" bullet proof".
    For instance you can:
    - add test points
    - add few 0 ohms resistors in series with critical signals and supplies to isolate thinks a bit if it's go wrong
    -add vias on unused ICs pins just in case...
    - limit as possible to have via's (or even tracks depending on the design density) under the parts
    - allow different parts with the same function to be mounted..

    Olivier
     
    Last edited: Jun 27, 2014
    Ehsan likes this.
  3. Arouse1973

    Arouse1973 Adam

    5,164
    1,081
    Dec 18, 2013
    It helps to have software that has a DRC (Design rule check) so you can see if there are any shorts or opens that you might have created. I would always draw the schematic first in the software I was intending to layout the PCB in. And then when you come to do the breadboard / proto-board design you may find some design mistakes before you transfer the design into the PCB design software. Post the schematic and layout on here and I'll have a look for you, see If I can spot anything obvious.
    Adam
     
  4. Ehsan

    Ehsan

    100
    1
    Jun 12, 2014
    Thank you Adam for offering help. I have fixed my PCB board already, but maybe you can tell me why pouring a layer of copper on top layer is wrong ? ( like what I did on this board )

    Also it has educational value for beginners to look at my mistakes: e.g. the big capacitors are preventing the user to reach the screws tightening heat-sinks on regulators, and as Olivier mentioned I put vias under that big capacitor in the center.

    Plus I never knew that PCB manufacturer can fill the vias with copper, so I just manually made holes and connected vias by a small wire and filled the holes with solder! That's the price one pays when he/she does 'self-studying' .
     
  5. Ehsan

    Ehsan

    100
    1
    Jun 12, 2014
    I forgot to attach the image :

    top_poured.jpg
     
  6. Arouse1973

    Arouse1973 Adam

    5,164
    1,081
    Dec 18, 2013
    What do you mean copper pour on top is wrong?
     
  7. Ehsan

    Ehsan

    100
    1
    Jun 12, 2014
    I showed my PCB board to my friend and he said I only should have copper pour on bottom layer, not the top. I used to not use them until I read an article about their benefit on balancing the heat across the board. So you mean it is ok to use copper pour on both layers, right?
     
  8. Arouse1973

    Arouse1973 Adam

    5,164
    1,081
    Dec 18, 2013
    No your friend is not correct. If we ignore EMC issues for the moment and just look at the manufacturing side. If you are hand soldering components then a copper plane only on one side is ok. The problem comes when your PCB is manufactured in quantity and goes through an automated solder bath or SMD oven. If the PCB is large and has a large amount of copper only on one side the PCB can warp in the oven as the copper on one side expands. This can bend the PCB out of shape. For large production PCBs it is better to have identical internal power planes. Or for double sided PCBs copper balancing might be needed.
    Adam
     
    Last edited: Jun 27, 2014
    Ehsan likes this.
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