Help with Ngineering Micro LEDs

[milw156]

I have purchased pre wired LED'S thru Streamlined Backshops, Southern Digital, and pretty sure Ngineering, and Ledbaron on ebay

[peteski]

Eutectic solder. I don't know if Max's recommendation is a lead-free alloy, but I use 63/37 tin/lead. Crucial for tiny stuff where you need to hold your breath while the joint cools.

I agree. All the silver solders I have ever worked with have relatively high melting temperature and are not eutectic.  Those small LEDs are very sensitive to high temperatures, and can easily be damaged (the solder pads might separate, the LED die ,or even the epoxy lens might get damaged by excessive temps.  A temperature-controller iron is also recommended (I use mine at around 600-650 deg. F).

Tin/Lead 63/37 (or 60/40) electronic solder is highly recommended for any electronic work. Flux is also very important (above and beyond any flux present in the solder).

[jdcolombo]

Let me second Max's technique.

I do the same thing.  I put about a 3" strip of the foam double-sided tape down on my workbench.  Then I line up 10 of the LEDs, making sure the cathode and anode are all aligned in the same direction.  Then I cut 20 pieces of magnet wire (38 gauge), 10 red and 10 green.  Then I tin about 1/16" of each magnet wire using a blob of solder on my soldering iron.  For this step, I don't use my Pace soldering station, but instead use my 25-watt Weller iron.

Then I switch to my Pace, with it's 1/64" tip, and tin the pads on each LED. 

Now it's assembly time: press the magnet wire on the foam tape so that the tinned end of the wire exactly lines up with the pad.  Touch my Pace at 650 degrees to the wire/pad.  Done.

The whole process takes me about 30 minutes for 10 LEDs.  But that's about all I can do in one sitting. 

John C.

[Lemosteam]

I find the foam tape to be more difficult than the 3M thin two sided mylar tape and aslo allows the LED to be more stable and less apt to melt near the soldering iron tip. Also sometimes it is helpful to orient the LED to the wires to help with final installation of the LED.

I.e. on the ends of the led, parallel to the short side, parallel to the ends of the LED but on the back pads, parallel to the long edge of the LED, and last but not least perpendicular to the back of the LED (this one s where the two sided tape does not help).

[mike_lawyer]

I finally was able to get the nano LEDs wired, and I also picked up some of the pre-wired LEDs.  I am using these for steam loco headlights.  I installed them with Microscale Krystal Clear, but I would like a top coating that diffuses the light a bit more.  Anyone have a recommendation for a goodclear coat that diffuses light?

[peteski]

Here are several ways.
Paint the entire inside of the headlight housing white (before installing the LED).  That will nicely bounce the light and will make the entire headlight appear to glow (not just the LED). Silver paint will do that too, but to a much lesser extent. White is best.

Punch a disk from 0.005" white styrene and use as a headlight front cover.  That is translucent, and will diffuse the light. But it will be white in color.

Take a piece of clear styrene sheet (0.005" or 0.010") and sand one side  using 400 or 600 grit sandpaper.  Then punch a disk out and use as headlight cover.

Mix some talcum powder into your Krystal Clear and fill the headlight housing with it (will take some time to cure).  That will make it milky and it will diffuse light.  Any translucent milky/frosty material will do that.

Or use one of the UV-curable clear resins (like Bondic), again with some talcum powder mixed-in to fill the headlight housing.  Depending on how deep the headlight housing is, I would probably do this in multiple layers (the talcum powder might block some of the UV light, slowing down the cure.

[mike_lawyer]

Here are several ways.
Paint the entire inside of the headlight housing white (before installing the LED).  That will nicely bounce the light and will make the entire headlight appear to glow (not just the LED). Silver paint will do that too, but to a much lesser extent. White is best.

Punch a disk from 0.005" white styrene and use as a headlight front cover.  That is translucent, and will diffuse the light. But it will be white in color.

Take a piece of clear styrene sheet (0.005" or 0.010") and sand one side  using 400 or 600 grit sandpaper.  Then punch a disk out and use as headlight cover.

Mix some talcum powder into your Krystal Clear and fill the headlight housing with it (will take some time to cure).  That will make it milky and it will diffuse light.  Any translucent milky/frosty material will do that.

Or use one of the UV-curable clear resins (like Bondic), again with some talcum powder mixed-in to fill the headlight housing.  Depending on how deep the headlight housing is, I would probably do this in multiple layers (the talcum powder might block some of the UV light, slowing down the cure.

Thanks for the great ideas! Are there any milky coating materials you would specifically recommend that don't need to be mixed?  I don't have any talcum powder on hand, and I have a Hobby Lobby about a mile down the road.

[garethashenden]

I wouldn't use silver solder, doesn't that use acid flux? In the past I bought micro LEDs and tried to solder leads to them, and in spite of me being great at soldering, it was VERY HARD to do. Now I buy the LEDs with the leads already attached but what worked best was to use solder paste. Line everything up (LED and wire), apply a dab of paste with a toothpick, heat with the iron (just heat, no need to actually touch the LED or wire), let cool, done. Good luck!

Hopefully what OP meant is the silver bearing solder that Ngineering sells. It’s tin/lead with something like 2% silver.

[peteski]

Thanks for the great ideas! Are there any milky coating materials you would specifically recommend that don't need to be mixed?  I don't have any talcum powder on hand, and I have a Hobby Lobby about a mile down the road.

Well, Baby Powder is talcum powder with some fragrance. You can get a small travel-size bottle places like Walmart or any drug store.  Or get a larger bottle, pretty much anywhere (supermarkets).  I wonder if microbaloons (if Hobby Lobby carries those) would work well too.  Never tried those. Heck, Hobby Lobby might have talcum powder too.  It is sometimes used in casting metal and resins.

But make sure you test my suggestions before committing to using them in the headlight, in case you aren't happy with the results. 

Personally I would go for painting the entire inside of the headlight housing white and filling the cavity with Bondic, and gluing in a clear styrene lens up front (unless you already permanently glued in the LED).