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Soldering surface mount LEDs


Dagworth

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Another topic carried over from the old RMweb. Again this started life on DEMU's forum but was brought to RMweb in response to a request. Hope it's useful.

 

As part of my Level Crossing project I needed some tiny LEDs on top of the barriers.

The difficult part is soldering wires to these LEDs, here's how I go about it.

 

These are the tiny 0.8mm LEDs from Bromsgrove Models.

Firstly these LEDs really are TINY!

led1i.jpg

 

The biggest difficulty with soldering something this small is holding it. I use a pyramid of Blu-Tac to keep the LED in place.

led2p.jpg

 

For soldering I use a Maplins temperature controlled beasty with a very fine pointed tip. I run it at its maximum temperature of 450 degrees. I tried it with lower temperatures and found it more difficult to make the joint reliably. The most important thing I find is to keep the tip clean. My favoured method is to wipe the tip on a damp piece of tissue.

led3p.jpg

 

Once the tip is clean I will hold the iron a couple of millimetres above the LED and apply a tiny amount of multicore (tin/lead) solder to the iron tip. Basically just enough to see the solder melt, then immediately apply the melted solder to the LED to tin it.

It should only be neccesary to touch the LED very briefly in order to tin it sufficiently to be able to make the joint.

led4.jpg

 

Scrape about a millimetre of the enamel off the wire with a craft knife and tin the wire.

Clean the tip of the iron again and re-tin it.

Hold the wire in place against the terminal of the LED.

A brief touch of the iron tip onto the tinned wire should melt the tinning on the wire and the LED terminal to make the joint.

Repeat the process for the other terminal and this is what you should have.

led5.jpg

 

Andi

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Dependant on the actual supplier, most seem to be Chinese/FE now, the surface mount LEDs may well come on a strip, or bandoleer tape, or even a plastic strip holder, which of course are designed to hold the LEDs through the tin bath delivery for flow machine soldering.

 

If the strip is there, then it can be used to hold the led for soldering, a great aid, and the led can always be pulled off, as the strip are designed to do just that as they exit the machine delivery system. All the LED's will be aligned the same way round of course.

 

I made a simple wooden jig that is a groove for the band of LEDs to sit in, and the wires are dropped onto each side, with a retaining wall, and end stops to guide them, and it's all soldered in situ, and then just gently pull the wires and the assembled LED comes away from the strip complete with even leads etc., easy mass production for building lamps, and street lighting.

 

Stephen.

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Yes, there are always suppliers of the wired type, but it may help with costs to solder you own wires on, as for some of the quoted items for the cost of 4/5 wired ones you can buy 50 un-wired ones. A recent bided for purchase on Ebay supplied me 1000 on a bandoleer strip for the same money, a massive difference in price, but these bargains are not always there, and the skill is needed to do the soldering.

 

Stephen.

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...

As part of my Level Crossing project I needed some tiny LEDs on top of the barriers.

The difficult part is soldering wires to these LEDs, here's how I go about it.

...

 

 

Hi Andi. Thanks for that info ... very informative.

With regard to Hollywoodfoundary's reference to the 0.8mm smd LEDs, what is the difference between the "sunny white" and "golden white" varieties?

What is peoples' preferences to which ones are better?

 

Thanks and best regards,

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There is no real difference, it is just two ways of saying the same thing. In other words, they have warm 'incandescent' colour to them, whereas the cooler colour versions have a bluish tint to them.

 

White LEDs are quite different to other colour LEDs, and work a little like a flourescent lamp. The LED is actually emitting ultra-violet light, and is covered with a phosphor that glows when hit by ultra-violet light. In the same way that flourescent lamps have different colours, the colour of the phosphor determines the 'flavour' of the white light emitted.

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Guest Digital

Hi Andi,

 

Excellent article, thanks for taking the time to share.

 

I use double sided tape to hold the LED in place while I solder the connections on.

 

John

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On the colours and types of LEDs it is getting a bit complex at first glance, but it boils down to the exact shade of colour, and separately but related to the brightness.

 

Until the white and blue type appeared, it was all down to brightness, and the colour of course!, with standard types and superbright versions.(plus shapes as well)

 

Superbright just means more efficiency, they glow brighter at any particular colour, and can stand more current through them than a standard type.

 

As with all silicon based solid state devices it had been found that the makers could grade the product, and basically the standard LED became the normal item with a minimum specification that worked, so when you see the LED described as standard it is a second grade item, that works, but is basic.

 

Superbright LEDs were better developed and are basically first grade items that meet a more rigorous specification, and give a better and brighter output, or have a better defined viewing angle specified, for instance.

 

Most specialist LEDs like Infra red, Laser, or UV types are first grade anyway, but second grade do exist, and go into TV remotes, toys, etc.

 

When blue was finally made, it allowed the development of very bright blue, with the addition of doping and dual colours to offer white, which on all early white types was, and still is, a blue white output.

 

This is handy as it works rather like sunlight in colour shade, and both standard types and first grade types exist in the same way. Superbright White would be a first grade high output......

 

But, it can be a yellow white shade, as the makers discovered than a phosphor could added to the white LED to glow yellow, and turn it into a warm white colour, which looks more natural, and has a wider bandwidth of colour.

 

Blue white tends to be a narrow bandwidth, and gives a harsh white light.

 

So we have ended up at the moment with basic grade bog standard LEDS and Superbrights, but in each colour there are variations like the shade, (as in yellow warm glow white), or the viewing angle, as with Torch Leds, where the lens makes a tight beam of light, but the basic LED backing it up might be a normal one or a superbright.......

 

Completely confused?? the only way forward is to get a good description from the supplier, but with modelling we usually do not need a tight specification, just to know what it will do.

 

The point to make is to read the advert with, say, Ebay, very carefully, the bargain may not be the bright white you were expecting, but a very blue white that is not so good on a model.

 

The best type to go for is a warm white for most purposes, and superbright if possible, or affordable, as they cost more.

 

They of course only glow as bright as the power that you supply, so a superbright can be underun and work very well indeed, still giving the clean warm white glow.

 

The fact it is a surface mount makes no difference at all, but the latest developments are mainly in surface mount types, as wiring is falling by the wayside now in industrial production.

 

Surface mounts only problem is the tiny size and that is where we came in!!!!

 

As an aside, keep a close eye on what is coming from the makers over the next few years, it is rapidly moving again in LED design, and new types are coming forward, mainly in very high output for lighting, and organic types for displays.

 

Hope this all helps chose the right type, and use Dagworths method to make them usable for models.

 

Stephen.

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As a quick aside I find that blue shade white light looks fine on modern image diesels and modern era layouts, and Yellow white for older steam engines and their environment, and the more vintage, the more yellow white, with Victorian buildings lit by a warm yellow glow!!!

 

Stephen...

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Stephen, the reason for that is because the blue-ish white resembles a halogen lamp whereas the yellow-white looks more like an ordinary lightbulb. In fact, I wouldn't be surprised if modern halogen lamps have first-grade, superbright blue-white LEDs instead of an actual lamp inside ;)

 

You can get LED replacements for domestic halogen lamps but they are pretty expensive. However they are now appearing in some train interiors. They seem to have three LEDs each and are a lot less dazzly than the halogen.

 

Probably more relevant is that most recent train exterior lights, including many replacements for WIPAC clusters, feature a LED cluster that can be lit as a white marker light or a red tail light. Unfortunately though a couple of model suppliers do larger versions I'm not aware of a red/whte SMD LED, which would also be useful in modern ground signals.

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Golden white tends to hint more towards yellow, whereas Sunny white tends to hint more towards white.

 

-----------------------

 

Also, not all of the "incandescent shades" white LEDs have a phosphor ( or alternative ) layer on them and/or a non clear housing.

Some types come in a clear housing version, some come in a more transparant amber-ish colour.

The used names don't really give consistent clues here.

 

Thus, if your LED is in direct sight, without a lens in front of it, and it needs to look as a clear lens, then be careful with your choice !!!!

 

-----------------------

 

DCC Concepts from Australia now also has prewired Nano LEDs, smaller as the 0.8 x 0.8 mm SMT 0603's ( which are on a 1.6 x 0.8 mm base ).

Apparently these are 0.4 x 0.7 mm, but I'm not sure if this is then the base size, with the LED possibly being 0.4 x 0.4 mm ?!?!?

 

DCC Concepts - prewired Nano LEDs

 

 

Regards, Michel

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There are even small leds made, but they are near impossible to wire to, I had a sample of .1x.1mm !!! only tabs or conductive paint would work here, a soldering iron dwarfs the LED totally, and it's needs a good magnifier to handle them, so not for everday use on models.

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I have to admit that I've never used surface mount LEDs, but what I did do 20+ years ago when I built Bonnybridge Central was to use ordinary 6mm dia yellow LEDs to represent oil lamps inside and outside the building. the inside ones were used "as is", but the outside ones were filed to the shape of an oil lamp housing, with glazing bars painted on. They looked very convincing. This should be done with care, as I understand the junction material may be toxic.

 

Allan

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  • 2 months later...

I have soldered many SMLEDs, here is my technique, most of mine are 1.2mm, but I have solder lots of 08 mm which I use for ditch lights.

 

soldering iron (I use 25w)

smallest silver solder I can find

flux

masking tape

small flat board

SMLEDs

coated wire (smallest possible)

 

I break of a piece of masking tape turn it upside down with the sticky side facing up, then tape around the edges of that piece of tape, so there is sticky facing up piece of tape in the middle (this will be attached to the flat board).

 

to solder I place the SMLED to the sticky part of the tape, I then cut the wire to the correct length dip it in the flux, rub some of the flux on the sides of the SMLED and tin the ends of the wire. I then place the wires down on the tape, and tape them in place, then I just have to touch the tined wire, a little solder and the soldering iron to the SMLED, and it done.

 

to color lights to more real colors I use clear Tamya paints, with just a little orange, you can turn the color more golden.

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Golden white tends to hint more towards yellow, whereas Sunny white tends to hint more towards white.

 

 

DCC Concepts from Australia now also has prewired Nano LEDs, smaller as the 0.8 x 0.8 mm SMT 0603's ( which are on a 1.6 x 0.8 mm base ).

Apparently these are 0.4 x 0.7 mm, but I'm not sure if this is then the base size, with the LED possibly being 0.4 x 0.4 mm ?!?!?

 

DCC Concepts - prewired Nano LEDs

 

 

Regards, Michel

 

Which we now stock - available in red, golden white, daylight white and red/white. There are also pre-wired harnesses of varying sizes using the NANO LEDs available for putting into locos or vehicles.

 

Of course if you don't like soldering very small LEDs you could use silver conductive paint...........

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  • 3 weeks later...

Hi

 

SMD are so handy. As pointed out the trick is to find the right color. Dagworth did a great job in showing how to pre wire your SMD's and some excellent advice. I was a big fan of wiring my own until DCC Concepts pre wired ones surfaced.

Most of us don't solder to PCB or boards and usually want to put them in tricky spots. Besides the time it saves them come pre wired with 0.15mm enamel wire which is pre thinned at the ends. I keep any of the scrap wire as it is so handy.

 

To give you an idea of where I use the DCC Concepts Nano SMD's and SMD's all I can say is think outside the box.

 

"Down lights" around the bar area in the Hornby observation car to "set the mood".

 

021.jpg

 

 

Just to light up this area when all other lights in the observation car are switched off.

 

resized_006.jpg

 

 

SMD with silver conductive paint, which was then painted over.

 

TrainShots012-1.jpg

 

SMD's used inside a Bachmann class 20 for dash lights and interior lighting.

 

IMG_1422Medium.jpg

 

Inside N Gauge coaches you can clearly see the difference between prototype (incandescent) and modern white (fluro's).

 

KatoThunderbird003.jpg

 

KatoThunderbird010.jpg

 

German modern Fireless Loco

 

IMGP1650.jpg

 

IMGP1429Small.jpg

 

Bullied with SMD cab lights.

 

IMG_1486Medium.jpg

 

SMD's with fibre optic

 

IMG_1482Medium.jpg

 

So good for those hard to get to places. SMD's and fibre on a bullied uncoupler light.

 

IMG_1176Medium.jpg

 

I lose about 30% of my SMD's through leaving the soldering iron on for more than 1/2 second and they are so small you just lose them. I am more than happy to pay for the pre wired.

 

Just use your imagination SMD's open up a new world for modelers.

 

Enjoy.

 

Martin

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