SMD PCB Assembly

Discussion in 'General Electronics Chat' started by tracecom, Jun 28, 2015.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
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    I have soldered a few SMD parts, but not a lot. Now, I have a new board design coming in a couple of weeks that has a couple of SOICs and several 0805 parts on it, and I am concerned about keeping track of the parts after they come out of the strip containers.

    I will need to build up to 10 of these boards, and in the past with non-smd parts, I would kit the parts for each board together, and then pick the parts out individually as I assemble each board. That won't work with SMD parts, but I don't quite know a better way. I plan to use solder paste and the hot-plate method of soldering the SMD parts. How susceptible to movement on the PCB will the parts be after they are placed, but before they are soldered? What else to I need to consider? Suggestions needed for the whole process. Thanks.
     
  2. ErnieM

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    Apr 24, 2011
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    I leave the parts in the strips until the very moment I am going to place one (or some) on the board just to keep them organized: caps and resistors typically come with white backing cardboard and I write the part number on them. So my stock is grouped by each kind of board and not for each individual board.

    It's pretty easy to knock aPCB before you reflow it and mess everything up. So make sure you don't do that.

    If you leave the boards out for a very long time the solder paste can dry out. I've always applied and flowed the same day.
     
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  3. #12

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    Nov 30, 2010
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    Can I assume you already know? A dropped 0805 goes the same place as socks go in the dryer. :D
    SMD capacitors are not marked. :(

    But seriously, a wet paste has some surface tension. It will hold parts in place better than nothing, but that's about all.
     
  4. tracecom

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    If I drop an 0805, I just hope it doesn't fall in a pile of 0805s of a different value. It's hard enough to tell my blue socks from my black ones.
     
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  5. Dr.killjoy

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    Apr 28, 2013
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    How many boards you looking to do ??
     
  6. mcgyvr

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    Oct 15, 2009
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    leave parts in the tape reel..
    apply solder paste to all pads (very thin/small if using a syringe... most tend to over do it)
    best to use a stencil/squeegee

    peel back tape and apply parts one at a time with tweezers/vacuum pen,etc...

    Store parts in the tape reels..

    The parts will stick to the paste "fairly" well but won't tank a big jolt or anything so just be careful.. As the solder melts the surface tension will typically pull the parts into the proper spots aligning them back straight... if you used too much paste they can slide all over the darn place screwing it up
     
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  7. tracecom

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    I am going to build one, and assuming it works, then nine more. Each board is about 2" square; the layout is attached so you can get an idea about the number of SMD components.

    PA20BBA Rev.1.PNG
     
    Last edited: Jun 28, 2015
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  8. Lestraveled

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  9. #12

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    The last time I was in CVS they were giving them away for free!
    Which brings to mind, "The Dollar Store". You might find a bargain there.
     
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