SMD LEDs
A typical SMD (Surface Mount Device) LED measures about 2.0mm long and 1.25mm wide, which is the size of a typical 0805 SMD LED. That size is as common as those though-hole equivalent of 5mm LEDs. SMD devices can be very tiny, with the current 0201 being the smallest, of having the footprint of 0.65mm (l) and 0.35 (w). As their name suggests, they are to be soldered on the surface of a PCB (Printed Circuit Board) and does not need any metal solder leads.
Hand-Soldering SMD LEDs
Because of their small size, SMD LEDs are great when it comes scale models. Normally, the scale modeler has to contend with the usual 3mm LED which, not only is it bulky but also, affects the design of the planned detail. The SMD LED can suddenly become very fragile when it is not used as intended; i.e. soldered to the surface of a PCB. There are other Pros and Cons about choosing the ‘right’ LED but today is not the day. Today, I am going to discuss about soldering them.
You can hand-solder a SMD LED with just a soldering iron, a cutter and a pair of reverse-tweezers (aka heatsink tweezers). The process is quite easy.
- Strip the pair of wires to about 1.5mm,
- Dip the exposed wires into the flux paste,
- Add some solder to the tip of the soldering iron,
- Touch-solder the flux coated wires. This is called tinning.
- Grip the 0805 SMD LED with the reverse-tweezers
- Dab some flux paste onto their solder pads
- Clean and add some solder to the tip of the soldering iron,
- Touch-solder the flux coated solder pads.
- Align the tinned wire to the SMD LED’s tinned solder pads.
- Touch both the tinned wires and solder pads for about 500ms.
- Repeat with the other tinned wire and solder pad.
- Cut away the excess tinned wires from the SMD LED’s solder pads.
- Test the soldered LED. Perform some troubleshooting if they do not light up.
So, you got one SMD LED soldered. Once you get the hang of it, even soldering 20 of them would be easy. Now, do that for 500 SMD LEDs. The video below is more or less how I did it, but with solder flux. Please, use solder flux. This is the secret ingredient which makes soldering look like magic. As SMD LEDs are small, there is no way for the excess heat from the soldering iron to escape but right into the LED itself; so you need to solder as fast as possible, or under 1 second.
Pre-wired SMD LEDs
SO, if I have a Project Run, soldering SMD LEDs are going to be a big problem. On one hand, I can solder it myself but it would take days. On other hand, I can get ready-made ones with consistent finishing but I would have to make sure they do light up and, that the price is reasonable. But if I really think about it, there is a THIRD CHOICE, which is, to not include it in the Lighting Solution. But since we’re here, today’s post is to tell you that I have succumbed to my insanity and bought some pre-wired LEDs…
