CAM file question for all the eagle users

Discussion in 'General Electronics Chat' started by chimera, Jul 10, 2011.

  1. chimera

    Thread Starter Member

    Oct 21, 2010
    Hello! I have finally managed to prototype and test out my first smd circuit using eagle (home PCB etching, soldering and testing) It was fun and it was interesting. Learned a lot..wasted a lot.. u know how it is :p

    I want to send files to a pcb manufacturer and get small-volume pcb made. This is my first time doing I don't have a clue how to go about it. Ive seen tutorials on gerber file generation but nothing that goes over circuits that use SMDs. All of them incorporate through-hole stuff

    So here are my questions:

    1- What layers should I select for my gerber files--specifically for SMDs

    2- Even better, is there a tutorial out there that goes SPECIFICALLY over smd gerber files--->as in which layers to select..what to name them..stuff like that. (I'm only doing single side layout to keep things simple)

    Ive learnt eagle on my own. But now I need guidance from an experienced eagle user. Please respond. Thanks!!!
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    While I don't use eagle I do have a lot of PCBs made for me.

    FIRST thing you need to do is pick a vendor and see what THEY want. Some get picky and only accept gerber, some will accept your Eagle project and worry out the correct files themselves.

    There is nothing special about SMD boards over thru hole boards, the same files are needed. Generally, in order of the board these would be:

    Board outline: While not completely necessary, it is best to define the board itself on a separate file just to end any possible confusion. The outline itself may or may not be included in following layers (Ive done it both ways with no blow back from my vendor).

    Top solder mask: the isolating layer over the top of the board

    Top Copper: The traces on the top of the board

    (additional inner layers if need be, make sure they are clearly named for proper stack up)

    Bottom Copper:The traces on the bottom of the board

    Bottom solder mask: the isolating layer over the bottom of the board

    Those are gerber files. Note the mask layers may be negative or positive shapes, vendors will get this correct unless you specifically tell them to use a negative layer as positive. (Also, if your purchasing department repeatedly sends a blank file over and over the house will eventually send you a blank board.)

    Gerbers are best prepared as "RS-274X" type. Gerber files need something called an "aperture," which defines a shape moved about to make lands, traces, and such. The "X" in "RS-274X" means these shapes will be defined in the same gerber file as they are used. The alternative is a separate aperture file, which is messy and not preferred.

    You will also need a drill file, see if you have a setting for enhanced Excellon Format, that puts the drill sizes into the same file.

    Both gerber and excellon files are text files and can be read in notepad.
  3. chimera

    Thread Starter Member

    Oct 21, 2010
    Thanks for your help Erniem.

    - So there isant a preference of files for thru-holes vs smd ?

    - What did u mean by the mask being postive or negative?

    - above are the files that I should send to pcb manfacturer?

    Ive heard (seen) pepole say that generating files for pcb houses is easy but unfortunately, this does not seem to the case for me.
  4. SgtWookie


    Jul 17, 2007
    BatchPCB has a good FAQ section that might answer a lot of your questions:

    They only make 2-layer and 4-layer boards. You could just use the 2-layer service for a single sided board if you want.
  5. chimera

    Thread Starter Member

    Oct 21, 2010
    hello Sgt, havent seen you in a while!! Well thanks for a good FAQ link, but im still stuck to where i began with.

    1- What common files should i generate to give to a generic pcb manufacturer. I ask this is because as i mentioned earliar, i have smd components layout and zero experience sending stuff off to the manufacturer.

    2- Can I get some guidance through this process with a very basic tutorial of the files that i would need to generate.

    Thanks. I hope it isant too much to ask.