1.8mm LEDs = what am I doing wrong

jamstraz

Active Member
I have ok soldering skills but somehow I blew out three of these tiny jerks despite correct wiring and resistors tested before soldering. My thoughts are the legs were cut too short(at the indents) and the soldering heat ruined them...right or wrong?
 
When you go to test them are they lighting for an instant then nothing? Also do you have them wired in series or parallel?
 
I have ok soldering skills but somehow I blew out three of these tiny jerks despite correct wiring and resistors tested before soldering. My thoughts are the legs were cut too short(at the indents) and the soldering heat ruined them...right or wrong?

You could be over heating the LED leads as you solder, you should try not to have your iron's tip on the lead longer then 10 seconds, any longer and you risk melting the lead bond on the Anode side of the LED. You should always have some liquid Flux on hand, solder is worthless once the flux has burned away, just make sure it's Rosin and not acid Flux. Try this,
Kester 186 Rosin Soldering Flux 2oz Bottle, RMA No Clean Lead Free - Walmart.com
 
When you go to test them are they lighting for an instant then nothing? Also do you have them wired in series or parallel?
When I tested it was an instant on one. They were tested one by one. 4.5 v with 330ohm resistor. Worked fine before I soldered. Solder and doomed...
 
You could be over heating the LED leads as you solder, you should try not to have your iron's tip on the lead longer then 10 seconds, any longer and you risk melting the lead bond on the Anode side of the LED. You should always have some liquid Flux on hand, solder is worthless once the flux has burned away, just make sure it's Rosin and not acid Flux. Try this,
Kester 186 Rosin Soldering Flux 2oz Bottle, RMA No Clean Lead Free - Walmart.com
I am using rosin with no flux.
 
I am using rosin with no flux.

I think you're referring to rosin in the solder, which gets burned away quickly during the soldering process. The liquid flux is in addition to what is in the solder to ensure there is proper "wetting" of the solder joint.
 
I think you're referring to rosin in the solder, which gets burned away quickly during the soldering process. The liquid flux is in addition to what is in the solder to ensure there is proper "wetting" of the solder joint.
Right, I am using rosin core solder and no fluxing
 
Have you tried pretinning your leads in order to make them solder faster? It also might be good to test the voltage coming into the LEDs and double-check that it's the right amount. Also, what brand of LED are you using? It might be a bad batch, and if you contact the manufacturer you could get some replacement LEDs for nothing.
 
Have you tried pretinning your leads in order to make them solder faster? It also might be good to test the voltage coming into the LEDs and double-check that it's the right amount. Also, what brand of LED are you using? It might be a bad batch, and if you contact the manufacturer you could get some replacement LEDs for nothing.
I wrote my first post on this with a splitting migraine so I don't think I was clear on what is happening. I have a bunch of 1.8mm LEDS in varying colors. Most are rated at 3.0-3.2v (except the yellow green which bizarrely are at 2 or so but this didn't affect them.) I was able to test them using a 4.5v (3 AA battery) battery boxes and 300ohm resistors. They work fine in the test. When I cut the legs at an indent that is on them (see picture) and weld the resistor to the - (black)and the wire it up with + (red), they have failed. It is my belief I have overheated them with my soldering iron because I'm too close to the diode

1586300103307.png
 
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Probably. What I would do is leave cutting the lead for after soldering. This way it'll hopefully act as a heat sink and not allow the heat to travel into the LED itself.
 
I just noticed I messed that typing...need to correct that. I'm soldering the resistor to the positive red. "Long leg gets the resistor"
I blame the rizatriptan...its a hell of a drug. I have a frigging electrical degree and I botched my wires. Class Valedictorian too (hangs head in shame)
 
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Is there any way you can solder it before installation so you can cut the leads after soldering? I've used 1.8mm LEDs before and this is really the only way to ensure they're safe from the heat of the soldering iron in my experience.
 
Is there any way you can solder it before installation so you can cut the leads after soldering? I've used 1.8mm LEDs before and this is really the only way to ensure they're safe from the heat of the soldering iron in my experience.
I don't understand this. The leads need to be cut short before soldering. Unless you mean to say solder along side the leads and then cut the legs short but that feels like it won't stop the heat travelling up to the LEDs because it goes down both lead and wire when I do solder.
 
I don't understand this. The leads need to be cut short before soldering. Unless you mean to say solder along side the leads and then cut the legs short but that feels like it won't stop the heat travelling up to the LEDs because it goes down both lead and wire when I do solder.
Maybe my iron is too hot. I have no way to control the heat though.

 
I would invest in a variable temp soldering station so you can test and find the minimum temp that solders correctly but is safe for the LEDs. And get the varied replacement tip set too- for fine work.

 
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