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difference between smd and through hole passive elements

Discussion in 'General Electronics Discussion' started by at89atbits, Sep 20, 2014.

  1. at89atbits

    at89atbits

    39
    0
    Sep 20, 2014
    Hi,
    Is there any elemental difference between smd and through hole passive elements other than the mounting technology,
    I opened the casing other day for a consumer appliance product and i noticed some of the capacitors were smd while some were through hole. However there was no particular logic to the ratings of the capacitors taken smd or through hole.
    Nor was there any correlation of it to the area of the board used.

    So does it depend on the circuit requirement which mounting technology to be used in any way?
    Or what are the things to consider?
     
  2. Arouse1973

    Arouse1973 Adam

    5,164
    1,078
    Dec 18, 2013
    Thats an interesting question. Sometimes the addition of components to a design results in SMD devices because its the way to go.But that costs more to produce becsuse you need reflow and bath or selective soldering. I have had 500,000 of my PCBs made over the last 10 years or so, and some have mixed SMD and TH.

    The products I design are used by idiots who drop them from a great height sometimes. We actually test them from 10m high. We went through a stage where ICs were popping out of their holders. So we cable tied them in. And guess what, they still popped out.

    We went to SMD and most problems went away, apart from SMD electrolytics which popped off like popcorn. We changed to MLCCs. Now most problems have now gone.

    Now SMD components have lower inductance which can help with certain circuits, they also are smaller and cost less to assemble. But it tends to be easier to heatsink TH components for power devices rather than having to use PCB space and copper pour for thermal managment.

    The other time I would use TH over SMD is if I wanted isolation from ESD. Our products are tested to over 25KV so a small diode, resistor would track 25KV no probs.

    Adam
     
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