Light Emitting Diodes

These are the lights I am using for my project. They are surface mount L.E.Ds size 0603 ,1.2 x 0.8 mm . This blog is about the process I have undergone getting them the way I wanted. I had a lot of trouble working with them before i devised the method I am showing you. Because of the voltage I am using I also need resistors and to keep everything super small I am using surface mount resistors size 0402 which are 1 x 0.5 mm. I have taken photos against a 1 pence piece and and a pin to show how small the compentes are. I want to use the L.E.Ds in a straight line with the resistors at 90 degrees to the L.E.Ds to create the smallest possible lights. A problem with working with micro components is the wire used to join them, conventional electrical wire is thick in comparison to the components. You can buy conductive thread over the Internet, it is quite expensive and takes a while to arrive. I found spun metal embroidery thread, which is the same thickness as ordinary sewing thread, and tested it for its conductivity. It conducts for up to 6v which is exactly what i need, however it has a tendency for the metallic coating to come apart on very long lengths, so i am using a mixture of metal jewellery wire and metal embroidery thread. Ok so here is my method of putting together my lights. I do 5 LEDs at a time, it makes it easier.

1) I had to laser cut a jig from a piece of wood. I cut dents into the wood on the laser cutter the size of the LEDs at the distance I wanted them. The LEDs are spaced at every 5mm. Then using tweezers and the end of a pin I place the LEDs face down in the right polarity and tape down the positive side. You can tell the polarity by the arrows on the back of the LEDs the point is the negative side. 2) I tape the tread down in position over the negative side of the LEDs and solder. 3) I cover the soldered negative side with tape to keep the LEDs in place and remove the tape of the positive side. Here comes the tricky bit. the resistors are placed on making tape so the don't move and are easier to pick up.Then I pick them up with the very tip of tweezers, with my left hand. I move the bottom of the resistors so they sit right angled to the tweezers. I move the resistor, still in the tweezers, so the positive side of the led and the bottom of the resistor are touching at right angles. With my right hand I move the soldering iron, with a tiny bit of solder on the very tip, towards the joint and solder. the solder takes about half a second. any longer and the solder on the other side of the LED heats up and that solder is broken. I do this with each LED and end up - 4) Now i have to hold the wire with he tweezers in my left and and very quickly solder it to the top of the LEDs with my right hand. this step needs to be done super quickly so the resistors do not come away from the LEDs. at this stage there is always one resistor that needs to be re soldered but in groups of 5 its not that bad. This is what it looks like before they are glued- After a set of 5 I glue them with 5 minute setting epxoy resin which is a strong 2 part glue what is clear. I apply it to the LEDs with the end of a pin to make little bulbs, the LEDs and resistors and encased in a ball of epxoy. This ensures that the solders do not break when the next set of 5 is made. The epoxy sets in an hour so I leave about an hour and a half between sets.I have to hand the LEDs between 2 pieces of wood so i can cover them with epoxy and not stick them to anything. These are the lights i have used in my prototype, out of 50, 48 worked so I must make sure i test that the LEDs work before I glue them. All the soldering was done by myself without any other help, it is a one person job and also I don't use any help to see the components like magnifying glasses. 5 is defiantly the optimum number to do at any one time, any more and solders start to break, any less and it takes too long. after 5 my eyes get tired so a rest is good. A set of 5 takes about 20 - 30 minutes. I hope you like the lights, next step is using warm white LEDs as these are ultra bright white. I had to buy the warm whites from Germany.