Big LED failure problem

Jaakub

Newly Enlightened
Joined
Sep 20, 2017
Messages
2
Hi guys,
recently I have many problems with SMD LEDs. The most common problem is some kind of leakage in silicone encapsulation. It might be air but I have no idea what is the root cause of it. Do you have any ideas? Is it dangerous? What can be done to prevent it? Is it encapsulation process fault?
LED after putting into tester first shines few times, than start to work normally. After about month they become damaged permanently.
Here are some photos of good and bad one.

muh00x.png

Hi guys,
recently I have many problems with SMD LEDs. The most common problem is some kind of leakage in silicone encapsulation. It might be air but I have no idea, what is the root cause of it. Do you have any idea? Is it dangerous? What can be done to prevent it? Is it encapsulation process fault?
LED after putting into tester first shines few times, than start to work normally. After about month they become damaged permanently.
Here are some photos of good and bad one.
 

ssanasisredna

Enlightened
Joined
Oct 19, 2016
Messages
457
What can be done? .... Don't buy cheap LEDs. Stick to higher quality brands (which includes some Chinese brands).
 

Jaakub

Newly Enlightened
Joined
Sep 20, 2017
Messages
2
Sure, you are right :)
I am just curious what is the cause of such failure. I browsed many websites about LEDs problems, and noone is even similar to mine.
 

mercrazy

Newly Enlightened
Joined
Jul 28, 2014
Messages
160
i had a similar looking problem that was caused by moisture in the LED before reflow. if parts have been out of sealed package, they should be baked before reflow.
 

iamlucky13

Flashlight Enthusiast
Joined
Oct 11, 2016
Messages
1,139
i had a similar looking problem that was caused by moisture in the LED before reflow. if parts have been out of sealed package, they should be baked before reflow.

I don't know if this is relevant to Jaakub's problem, but just for general knowledge, I recently looked up information on why moisture is a problem for LED's, which is why reputable suppliers usually sell surface mount LED's in sealed packaging.

Basically, the humidity from the air can be absorbed by the LED (and other electrical components that may have moisture exposure limits), but evaporates again during reflow. The pressure generated by moisture evaporating faster than it can migrate out of the package could cause the die itself to separate from the substrate it is mounted to. That means the thermal path it is cooled by is compromised, and possible even that the electrical connection gets broken. There may also be other potential problems I'm unaware of.

I think most good LED's are pretty tolerant of exposure to even high humidity air, but there are procedures for baking them to dry them out if necessary. That procedure usually seems to be something like 200 degrees or so for several hours before performing the reflow soldering.
 
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