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Re: Approximate cost of pcb assembly

Discussion in 'Electronic Design' started by Nemo, Aug 8, 2009.

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  1. Nemo

    Nemo Guest

    What is the approximate cost of pcb assembly relative to pcb
    Lots of variables, but for a first finger-in-the-air estimate that's not
    going to be far off.

    In general for LARGE runs the assemblers consider how many components
    there are to place, of how many different types. This determines how
    much time / how many different types of reel will be needed.

    But for small runs other items dominate the cost. Apart from component
    prices, you need to consider if the components are available in these
    quantities (that's tripped me up recently - I spec'd something only
    available in quantities of 250 or more); how many different suppliers
    the assembler will need to deal with, because that will take a lot of
    time; whether there are any special operations like, mounting components
    on the underside of a board.

    I recently used a tiny (1 man!) assembler in the UK who used a
    semi-automatic SM assembly machine. It was very impressive, placing
    things under manual control but doing the fiddly work for him. Good
    blend of machine and man for small scale stuff. Many assembly houses are
    either purely manual or purely large-scale automatic SM machines, with
    all the setup hassle their overheads imply.
  2. John Larkin

    John Larkin Guest

    We have a couple of Essemtec semi-auto p+p machines. Great stuff.

  3. Nemo

    Nemo Guest

    Bobby Joe writes
    For a relatively small run like this there are no industry standard
    rules. You need to talk it over with the assembler you choose and they
    will guide you through their assembly procedure. The small / medium ones
    are pretty flexible as *they want your business*. Your CAD package can
    probably output an x,y file to aid machine assembly of PCB's - ie "R4 is
    at origin + 23mm in the x direction, +12mm in y direction". I think most
    people put their origin at the bottom left corner of the PCB but it's
    arbitrary. Some assemblers like "fiducial" marks (target shaped things)
    on the PCB's to centre their camera-based component placement machines.

    If you ask for the leftover components back, you should get them.

    If mounting tiny LED's make sure there is some obvious polarisation.
    I've seen PCB's where not one LED lit up because they'd all been put in
    the wrong way round. Machine assembly is nothing if not consistent!
    These days if I choose an LED I make sure there's some way to tell if
    it's the right way round - not always an option if your design requires
    miniaturisation, in which case you need to look at the manufacturer's
    specs to see which way round it is fitted in the reel.

    Anyhow - basically choose an assembler or two, then discuss with their
    production engineers over the best approach.

    If you're in the UK I can maybe help you a bit further with finding a
    suitable assembler. If you're in the States, I leave you to the tender
    mercies of your countrymen. Sounds like you're in a good position
    though, a small run like this implies you are in a small company thus
    have freedom to do whatever suits you - unlike large companies where you
    have to use the Approved Suppliers and Procedures 8)
  4. Ben Jackson

    Ben Jackson Guest

    My understanding from discussion of XY files on the PCB dev list is
    that the exact XY position (center of the part, corner of the part,
    etc) is so machine/vendor specific that they only expect rough
    figures anyway. Then as part of the setup they tweak that file to
    their process.
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