Soldering surface mount components.

Discussion in 'The Projects Forum' started by RodneyB, Oct 23, 2013.

  1. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    I have made myself a reflow oven using an electric frying pan which works really well. I am trying now to improve the quality of my boards.

    I have been spreading solder paste as evenly as possible across the board and then placing the components onto the pads into the electric frying pan and it works, however there is not an even flow across all the copper of the solder.

    Do surface mount capacitors have tinned leads? Why I am asking Is, I want to find out if flux was used and the components then placed directly onto the pads and into the reflow pan, would the components if factory tinned adhere to the copper pads.

    Thanks

    Rodney
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
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    The "paste" part of SMT solder IS flux.
    And No SMT components are not tinned. They are tin/silver,etc.. plated though.. But not tinned/plated in that there is sufficient solder to rely on that only.. You must use solder paste.

    The problem you are having is SOLELY because you are using a frying pan.. Nothing more than that. Its heat distribution will always be uneven. Its a frying pan.. not a precise reflow oven with "preheat"/ramp/soak profiles,etc...
     
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  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    The term "reflow" is a bit of a misnomer as this is the first time you are melting the combination of solder, parts, and the base PCB to form the joint. But yes, you DO, MUST add some solder to get the process to work. SMD solder paste is a slurry of tiny solder balls suspended in a liquid flux.

    Solder paste should be applied VERY SPARINGLY just to the pads to be soldered. Covering the entire board in flux along is a waste of good flux.

    As far as using an electric frying pan as a heat source, well, why not? I've reflowed boards on my stove top.

    You heat the solder, it melts, you take the board off the hear source. It's really a rather simple process.
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Solder paste also comes in a syringe, which is convenient for small boards.

    However, your thumb will fall off if you use it on a large board. Trust me, I know.
     
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  5. RodneyB

    Thread Starter Active Member

    Apr 28, 2012
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    Thanks for the advice. i find the syringe very difficult to dispense the solder with, often the pads and tracks are smaller than the tip of the needle. is there a simpler way of dispensing the solder paste
     
  6. Metalmann

    Active Member

    Dec 8, 2012
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    You can try a toothpick. Small, but deadly!;)
     
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  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Get a smaller needle. I use EFD tips with a .010 opening which have served me well, and I've worked with some very tiny parts.

    Chip Quick makes a syringe gun that makes dispensing painless... a bit pricy but worth it is you do this every day: SMDSG10CCR

    [​IMG]
     
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  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
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    I just cut solder paste stencils on my CNC machine, out of thin plastic film (like overhead transparency film sheets).

    If you don't have CNC capability, you can get stencils laser cut at a number of places, I think Pololu.com still do stencils for people.
     
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