I need to put an SMD Crystal on my through-hole board. How?

Discussion in 'General Electronics Chat' started by TheLaw, Sep 16, 2010.

  1. TheLaw

    Thread Starter Member

    Sep 2, 2010
    228
    2
    Perhaps I am asking a question with a very obvious answer. Regardless, hopefully someone who is thinking straight might be able to help.

    I'm a through-hole sort of guy. Always used through hole. But you see, I am designing an ultra-rugged Arduino board fully equipped with some of the best components in the world. (125C 100V caps, Ceramic/Metal Resistors, etc.) It's going to be able to withstand the worse.

    Regardless, I am working on the circuit design and I realized "Oh shoot, I need to use an SMD crystal on this board. It's a 16Mhz crystal but has a super low PPM and is high temp rated. So, I've never used SMD before.

    How do I get an SMD component on a board that is otherwise through hole. All the leads would be on the bottom and this would be on the top and...maybe it's just too late for me to think straight.

    What basic PCB concept am I missing right now? How do I integrate this SMD component in this application or in any other application (for future reference)?

    Thanks.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Get the crystal's outline off the data sheet and place pads at the correct spacing and dimensions on whichever side of the PCB works best. It will never know if it's on the "wrong" side.

    Can you really do a microprocessor layout on a single sided board?
     
  3. TheLaw

    Thread Starter Member

    Sep 2, 2010
    228
    2
    Well you can do anything on a single sided board. It just depends on how big you want to make it. :D

    Well, a very basic Arduino can be achieved on one side. http://arduino.cc/en/Main/ArduinoBoardSerialSingleSided3

    There's is very little to Arduino. It's really just an DIP Atmel chip, a 16MHz crystal, and a communication chip whether it be MAX232 or an FTDI USB chip. And then you have a small assortment of caps, resistors and diodes.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Strongly agree. My first efforts were done with 2X templates on paper. The final artwork done with tape and rubdown decals. That took lotsa room, as reroutes were a tad inconvenient.
     
  5. TheLaw

    Thread Starter Member

    Sep 2, 2010
    228
    2
    Yep. I dunno how I am going to do this one. I'd really like to etch it but I'm not sure how small I can get the leads. It might have to be ATX motherboard sized. :eek::eek:

    Oh and regarding the original question, you concur that I should put the crystal on the other side? That would be the logical thing to do, but I am almost certain I found boards with a combination of SMT and Thru-Hole with all of the components on the same side...Shucks...I just can't think of how I would do that. Seems like it should be simple too...

    Thanks.
     
  6. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    The other side is fine. Commercial boards have all the components on the same side because they are soldered by applying solder paste and putting them in an oven. The components would fall off if they were on both sides. It requires a PCB with copper on both sides.
     
  7. hobby16

    Active Member

    Aug 30, 2010
    30
    4
    If the ultra-rugged board is just for you, you can essentially do anything because manufacturability is of zero importance. It's OK to mix SMT and through-hole like this (a small 220V~ gradator I made recently) :
    http://faztech.free.fr/uploads/DSCN0105.jpg
    http://faztech.free.fr/uploads/DSCN0104.jpg
    You can even, depending on the package of the SMT quartz, remove the plastic holding and it becomes a through-hole.

    For series fabrication, if you want to mix the two technologies, it may be advantageous to have SMT components on copper face like above : the SMT components are glued to the PCB, through-hole components are placed and all is soldered in one pass in a solder bath.

    BTW, be carefull and don't get suckered by the ppm marketing ploy. If ppm is not ppm per °C temperature coefficient, your quartz would bring nothing more than a quartz from a mainstream manufacturer.
     
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