Soldering SMD Resistors - Helpful hints

Soldering SMD Resistors - Helpful hints

Postby 0AlphaOmega » Fri Jan 01, 2016 7:12 pm

The SMD resistors are pretty small and it's worth being prepared before you start to install them, so here are some suggestions if you've not soldered them before and will be using a conventional soldering iron.

Ensure that you have no distractions!

Tools:
  • A good quality fine point soldering iron (temperature controlled workstation is best)
  • Good quality, low melting point, fluxed solder (Lead/Tin if you can get it)
  • Tweezers - I used a metal healthcare set - eyebrow plucking tweezers are probably not a good idea as they are small and fiddly and too stiff. They need to be comfortable in your hand and not require force
  • Glass bowl with high sides - I used a glass ramekin
  • White cloth - I used kitchen towel - This helps visibility and suppresses bouncing if the SMDs are dropped! Place it under the bowl and under the PCB
  • Magnifier - I used a head mounted magnifier with a loupe
  • Lots of light!

Before you begin to solder, ensure that the iron is up to temperature and lightly tinned. Clean your iron throughout the procedure.

Method:
  • Identify the value to solder and highlight with a circle on the drawing where each one goes
  • Tin one pad of each location on the PCB - do not use too much solder
  • Carefully expose the SMDs over the bowl by pulling back the top film with the tweezers. Allow them to drop into the bowl from a low height - The white cloth under the bowl helps to make them visible
  • Any SMDs that are face down can be lifted with the tweezers and dropped, they will flip over without 'man-handling' them as they bounce
  • Count them!
  • Orient the PCB so that soldering will be easy
  • Using the tweezers, transfer one SMD to the board, the silver ends line up with the pads
  • Place the tweezers on top of the SMD do not apply force, if you slip, the SMD will never be seen again! The SMDs are so small that capillary action will cause them to stick to the iron tip; this is why we want to hold the SMD down
  • Apply heat to the junction of the tinned pad and the SMD, when the solder wicks, remove the heat but keep holding the SMD until the solder solidifies.
  • Rotate the PCB 180 degrees
  • Apply heat to the junction of the pad and the SMD, apply a small amount of solder to the junction. Be quick as the heat will transfer and unsolder the other pad
  • Allow the solder to solidify
  • Inspect the joint with the magnifying glass, resolder if you are not happy. If still not happy, come back to it later
  • Mark off the circle on the drawing
  • Pat yourself on the back before moving onto the next
  • Take your time and relax :)

I hope that is helpful
0AlphaOmega
 
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Re: Soldering SMD Resistors - Helpful hints

Postby jye1 » Sun Jan 03, 2016 8:06 am

Thank you for the detailed description!
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Re: Soldering SMD Resistors - Helpful hints

Postby 0AlphaOmega » Tue Jan 05, 2016 1:44 pm

My pleasure!
For the feint hearted, I have just found this if you want to practice.
The company is nothing to do with me; I found them a few moments ago while looking for something else.
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Re: Soldering SMD Resistors - Helpful hints

Postby GTNMUDY » Sun Feb 07, 2016 9:40 pm

Excellent suggestions.

I just hope I dont have to solder a 40 pin IC....

I only did one once back in the 80's :o
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Re: Soldering SMD Resistors - Helpful hints

Postby 0AlphaOmega » Tue Feb 09, 2016 7:49 am

The kits that require SMD soldering usually have the ICs soldered. However mine didn't have all if them soldered, but take it slow and you'll be fine. The through-hole components as easy to solder. Just ensure that you have a good quality fine tipped soldering iron and solder.
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