Electronic – special way to solder to these LED thermal pads

ledsoldering

[I don't know the correct names for these things, so please correct my vocab as needed.]

I just tried to solder a wire to the one of the rectangular contact areas on this LED. I'm a beginner hobbyist with a radio shack soldering iron, but usually I can solder wires okay. But in this case the solder just balled up on the surface and refused to bind to it. Is there a trick or a special way to connect these to wires?

enter image description here

Actual part is here

Best Answer

The pad is thermally connected to the aluminium plate. That's a byproduct of the LED cooling scheme. As a result, it's harder to heat the pad with a soldering iron. Until the pad is heated sufficiently, the solder will not stick to it.

  • Heat the pad longer before actually trying to solder to it.
  • Perhaps, use a larger tip in the soldering iron.
  • Putting a drop of solder on the tip increases the contact area and improves heat transfer.
  • If possible, pre-heat the whole board using a heat gun or a hot plate. Temperature of the pre-heat should be much lower than melting point of the solder.
  • Use leaded solder. It has a lower melting point.