insulating smd LEDs

[jbconn]

I've been soldering magnet wire  to 0603 SMD LEDs to install ditch and marker lights (much cheaper than buying pre-wired).  My technique is improving, but it's still rougher than those I've bought pre-wired. 

When done as neatly as I can, you are left with (at a minimum) two uninsulated solder-covered wires running up the back of each side of the LED.  I'm concerned about these shorting agains the inside metal of the ditch light housing.  In some cases, the insulation on the wires below the LED may also be compromised.  I infer this from one example that worked when initially tested but would not light when I twisted the wires together (it resumed working when I untwisted the wires close to the LED). 

Some pre-wired examples I previously bought had the LED and the wires closest to it dipped in a thin translucent coating of some sort.  (some red ones were dipped in a red-tinted coating, which also improved appearance when not lit).  I've Googled "insulating varnish" which led me to all sorts of products, (insulating lacquer, Q-dope, Corona dope...) and have seen lots of possible solutions, but I'm not sure that any of these are quite right (i.e., thin, translucent, insulating, and can be applied by dipping (vs. spray can). I've also seen conflicting advice on using nail polish, floor polyurethane, and other products.

Has anyone done this and can you recommend a product?

[zakc]

What about liquid electrical tape

[Deleted]

jbconn,

What size SMLED are you using?

I have been using the 0603 LED and solder my own wires to them. I never have any exposed wire coming off the pad. My method is as follows.

1. tin the end of the magnet wire first. I simply put some flux on the end of the wire and then hit it with a soldering iron that has some solder on it. The coating on the magnet wire burns away and leaves the wire tinned.

2. If I solder the wire on the front side of the LED (side with the light), I use a piece of double sided tape and plant the LED down on it. I paint the solder pad with some flux and then lay the magnet wire over the solder pad and then put a piece of masking tape (blue type) over the wire to keep it in place. I lay the magnet wire so that the protective coating is right up next to the solder pad. Then put a small dab of solder on the end of my iron and just touch the solder pad and quickly pull it away after the solder flows. DONE and the protective coating is still in place.

3. If I am soldering to the back of the LED, I put the light side in a small vice to hold it in place. Again, I paint the solder pad with flux an lay the wire so that the protective coating is right up against the pad and again solder the wire in place.

No problems ever with any exposed wire coming off the LED.

[lyled1117]

Brian and others,
Ngineeering does a small 'vice' that works quite well for holding smd LEDs for soldering. For those who desire to it would be relatively easy to build one of these yourself, but sometimes it's just as easy to let someone else do the work. At about the midpoint of the page I've linked to is the holding tool and their instructions on how to use it. It has two key components. One is that one clamp is shorter than the other, and the second is some grip material placed on the longer jaw that holds the wire. They suggest holding the device in a small vice, I have found even a clothes pin will do in a pinch. It works.

Lyle

ngineering.com/other_cool_tools.htm#LEDholder

[c415rock]

Hi Guys,

I second Lyle's recommendation of the ngineering tool. I own one and it is very hand indeed, plus I would also recommend the Intelligent LED Tester as well. These are great tools to have and worth every penny. Especially if you wire up your own SMT LED's.

Erik

[jbconn]

Thanks for your responses. I have seen the ngineering tool, but have not yet bought it. I have the ngineering LED tester and use is to not only test the LEDs but to verify alignment before soldering.

My currently evolving technique is to fix several 0603 LEDs lighted side down on a strip of double side tape. I lightly coat each solder pad with a tiny bit of flux then tin each pad. I flux and tin the LED end of each wire (My magnet wire is not terribly good at heat stripping, so I sand it a bit first. this leaves me about 0.5" of stripped and tinned end on a ~6" wire. This is actually somewhat helpful, since the excess wire allows me to secure the wire on both sides of the LED prior to soldering) I use two parallel strips of double-sided tape running alongside the first to hold the tinned part of the magnet wire across the tinned LED pad. A light tap of the soldering iron fuses the wire to the pad. If it shifts at all, I can use a sharp tweezers to position the wire for a second try. I have learned that a third try risks LED damage.

When soldered and tested, I pull the 0603 off the double-sided tape, flip it over to lighted side up, and trim the excess wire against the plywood with a hobby knife. I twist the LED while holding the wires to neaten it up.

This works generally well. I set out to solder 12, only destroyed two, and lost one on the floor when it flipped out of the tweezers.

I am still concerned about shorting, Anyone have any more thoughts on insulation? The liquid electrical tape I have previously used for boats is very thick and opaque (and the stuff I still have, if it hasn't solidified, is bright blue). If you all know of a thinner translucent product, especially if it's red, I would appreciate a reference or link.

Jim Connolly

[artur]

nail polish also works

[Mark R.]

Give it a coat of CA.  

Mark.

[spike]

This thread is proof that there is such a thing as ESP! I had heard that nail polish worked, but I wasn't sure if it was really true, and I was going to ask.

This is great. I can just raid The Spaghetti's (my wife's) makeup. I think colored would be best, just as long as you are careful. This way you can see that everything is covered, so you don't fry a decoder.

[Eccentric_Crank]

Laurie McLean's YouTube site is a goldmine of useful stuff.

Make sure you look at the marker lamp videos.

www.youtube.com/user/scoopmmr?feature=watch

Dan M.

[analogbeatmaker]

I "paint" the exposed wire and solder blobs with Microscale's Micro Mask. Works great.

[brgp302300]

I would use a drop of Micro-Scale Kristal Klear.

[analogbeatmaker]

Jun 8, 2014 10:36:42 GMT -5 brgp302300 said:

I would use a drop of Micro-Scale Kristal Klear.

Kristal Klear is not as tough as Micro Mask and will rub off easier.