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SMD techniques

Discussion in 'Electronic Design' started by PigPOg, Mar 31, 2005.

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  1. PigPOg

    PigPOg Guest

    Hi, can anyone help please?

    I have to migrate a number of designs from PTH to Surface mount. Can
    anyone suggest a concise book or on-line resource that can answer
    questions such as: -

    Do I put mixed (PTH and SMD) components on the same side of the PCB or
    on opposite sides and what are the associated merits/disadvantages?


    When generating the solder-paste mask what alignment marks do PCB
    manufacturers generally require?

    These are but two of many questions I have. I'd be most grateful for
    any suggestions/advice.

  2. Guest

    Life is easiest if you put both sorts of components on the same side of
    the board - putting SMD components on the track side the board means
    that they have to be glued down before the board can be reflow soldered
    - it isn't a big deal, but ti is an extra operation.

    Solder-paste masks work the same way as every other mask - you don't
    need special alignment masks (at least not anywhere I've worked).

    The printed circuit board house that makes your boards should be able
    to tell you all about this sort of stuff.
  3. PigPOg

    PigPOg Guest

    Thanks for the info Bill.

  4. Fred Bartoli

    Fred Bartoli Guest

    Sure, but on the other side :

    Having both components variety on the same side requires 2 additional
    - solder past screening
    - oven reflow
    that are not necessary if the SMD components are soldered along with the TH

    If _all_ the components can withstand wave soldering the most economical way
    would be SMD on track side, and just one soldering pass.
  5. Apparatus

    Apparatus Guest

    I usually put SMT debouncing caps on the bottom of the board and
    everything else on top. I'm a hobbyist though -- not sure how well this
    works in mass production.

    Be sure to put thermal reliefs on the power pins of the SMT pads,
    similar to through-hole thermal relief. On my first board I had some
    bad solder joints due to not putting these in.

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