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Thru-Hole and Surface mount? Costs.

Discussion in 'CAD' started by Mike V., Aug 29, 2003.

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  1. Mike V.

    Mike V. Guest

    Being a software and firmware guy most my life, only now am I doing
    layout (or hiring someone's services to do it for me) of a 4-layer
    PCB.

    I have a few questions:

    1. How much can I save by going surface mount vs thru hole, in terms
    of:
    * costs of thru hole parts vs surface mount counterparts.
    * cost for service to stuff a thru hole board vs a surface mount
    board.
    (I heard I can save up to 20% of the costs on the manufacturing part).

    2. I looked at websites that offer online quotes for manufacturing the
    PCB once you give them your gerber files. They ask how many "holes"
    will be in the board, and the sizes of the holes. With thru-hole, it's
    easy to see that each pin of the component or leg of a resistor or
    capacitor constitutes a hole. Is a surface mount part also considered
    a "hole" that i should account for when getting a price quote?

    Thanks,
    Mike
     
  2. Paul Burke

    Paul Burke Guest

    Some components are cheaper, some more expensive, and some about the
    same! In small quantities, using hand assembly, SM usually costs rather
    more. In large quantities, with assembly automated, it is usually
    cheaper (comparing like with like). Don't forget the saving on PCB size
    and the ability to populate both sides (though this pushes up assembly
    costs). Testing is often easier with through hole, and you get fewer
    problems due to components that look stuck down but aren't.
    They are interested in the number of drill operations and the number of
    times they have to change drill size. So an SM pad will not add to their
    costs. On the other hand, pin- limited CAD packages are interested in
    limiting the functionality you get out of them, so SM pads count as pins
    there.

    Paul Burke
     
  3. I am going through this process too (so don't take the below as
    gospel!).

    This will depend on the mix of components and the quantities.

    There isn't much difference with IC pricing, (although very many new
    chips are only available in SMT).

    Most passives are cheaper in SMT, but for me this is not too
    important since these are only a small portion of the parts cost
    anyway. For example, resistors are say $0.002 each in SMT vs $0.01 for
    through hole. But they both cost me $0.05 to place (small qty
    production). And there is a $15 IC on the board anyway.

    The main saving is probably in the board, especially 4 layer which
    tends to be charged by the square inch. Then again maybe you only had
    to go 4 layer because you went surface mount...

    I think there are higher initial costs with SMT such as the solder
    paste screen (~$120), placement machine programming, prototype
    construction. ICs may *only* be available on reels of 2,500 when you
    are only ever going to make 100 boards. Anyone want 2,400 BA6845
    stepper motor drivers ? :)
    I think you will have to get quotes for your specific quantities and
    parts mix - there seems to be quite a large variation. Also you may be
    able to tailor your design for lowest cost from a particular
    supplier. For example, if they quote per placement, use lots of
    resistor / capacitor / diode arrays instead of individual parts.
    Probably. The ones I have seen use the number of component
    pads. However if they are just quoting per "hole" they may not be
    thinking of SMT at all, or may have a completely different pricing
    structure for this.
     
  4. Depends on the parts. You may not be able to get some parts in through
    hole any more (and some were never introduced in through-hole in the
    first place). If you insist on all-SMT rather than "mixed, mostly SMT"
    you may push the cost up quite a bit, as things like transformers,
    terminal blocks, switches and such like don't translate that well to
    SMT, and LEDs have some issues.
    Depends on the quantity. Hand assembly of SMT is typically slower,
    IME, but it can be economically automated at relatively low quantities
    (low thousands). The solder paste stencil and other setup costs make
    it a bit pricey to do just a couple of hundred boards.
    Don't forget the board will usually be smaller with SMT. Components
    are smaller so they take up less store-room space.
    No, it isn't. But typically, IME, the number of holes doesn't affect
    the price of the PCB in quantities over 100 or 500 pieces, it's mostly
    square inches, order quantity and specifications. The finish of the
    PCB may have to be different for SMT etc. etc.

    Best regards,
    Spehro Pefhany
     
  5. Not sure I agree here about mixing. Like Speff said, there are usually
    some parts which are disproportionately expensive in SMT. In any case,
    for me there always seems to be something that *must* be through
    hole. Once you admit one through hole part it opens the door for the
    others, where they are convenient.

    (My experience is limited to relatively small quantity however)
     
  6. Steven Swift

    Steven Swift Guest


    In low quants you are right. Above a few thousand piece per run, you
    can greatly increase the manufacturing costs by adding processes.
     
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