X-Ray study of LED reliability

[Gunner12]

Came across this video about LED failures from Creative Electron:
https://youtu.be/UoxexFBmr0E?t=3m48s

Didn't know about solder voids, now I know that solder can sometimes look like a sponge.
So, if your build isn't getting as bright as you expect, or is dying early, blame the voids!

 

[DIWdiver]

Wow, that video is all over the place. First, it's 50% voiding reduced to 35%, then it's 40% reduced to 8%. I don't see anything in the "before" pictures that approaches 40% voiding, or anything in the "after" that approaches 8%. The voids shown in the X-rays are nothing like the voids shown in the microscopic cross section (macroscopic bubbles vs. microscopic "sponginess", which have completely different causes). First he's talking about die attach (which is within the LED component), then he's talking about attaching the component to a PCB. It's like he's blaming both the LED component manufacturer and the PCB assembler, but talking interchangeably about them, without making any distinction about what he's doing. But even that doesn't make sense because the LED he shows X-rays of is not the same LED he shows on the PCB.

To me, this sounds like a job well done being oversold to an audience whose technical knowledge is being severely dissed (and deservedly so if they let him get away with it).

 

[LedTed]

That video makes me miss the real time x-ray machine I used for discrete electronic component troubleshooting.

 

[lucca brassi]

X ray inspection is almost standard in automotive industry . For quality checking moulded parts (sensors (bosch , continental, valeo )) we have that one https://www.gemeasurement.com/inspection-ndt/radiography-and-computed-tomography/phoenix-vtomex-s

for instance to check welding quality , moulding quality , for e-cars driver board - bonding quality on substrates for 3-phase power IGBT to PCB ,........ checking competition with as NDT( non destructive test ) :twothumbs

 

[Steve K]

C-T scan x-rays are quite handy for checking out a piece of electronics that you can't disassemble. I've got a few images left from a scan on a sensor 7 or 8 years ago.....


In the image below, you can see a few bubbles in the solder fillets ....

you can see a bit of this in this image too....

It is also handy for looking for broken capacitors (especially in a potted device), cracked traces, etc.

 

[SemiMan]

Remind me to find out who that contract manufacturer is, and NEVER use them. They obviously have severe issues with their soldering process, whether that is old paste, bad paste machine, way too fast heat rise in the reflow oven (bubbles), etc.

 

[more_vampires]

Came across this video about LED failures from Creative Electron:
https://youtu.be/UoxexFBmr0E?t=3m48s

Didn't know about solder voids, now I know that solder can sometimes look like a sponge.
So, if your build isn't getting as bright as you expect, or is dying early, blame the voids!

http://www.cree.com/search-results?&lcid=9&q=solder joint reliability

That Cree Solder Joint Reliability Study seemed like an interesting read, with xray pics.

 

[Steve K]

Remind me to find out who that contract manufacturer is, and NEVER use them. They obviously have severe issues with their soldering process, whether that is old paste, bad paste machine, way too fast heat rise in the reflow oven (bubbles), etc.

well, that was the least of the problems that we had with this supplier. The biggest problem was with potting... it wasn't adhering to the plastic housing and had cracks in the potting. Sooo many problems... but we've recently gotten a competing design and should be rid of this device soon <sigh>.

 

[SemiMan]

That seems strange but you need compatible plastics and need to watch for mould release compound on the plastic.

Cracking? Very strange. Sounds like way too hot of a cure.

 

[Gunner12]

This was a area of reliability I haven't though about before, and thought would be nice to share. Glad to see that many of you have more in depth information and experience with this!

http://www.cree.com/search-results?&lcid=9&q=solder joint reliability

That Cree Solder Joint Reliability Study seemed like an interesting read, with xray pics.

Sure was, Osram has also done a study as well, and I'm sure many other companies as well. http://motiv8forums.com/uploads/3/2/9/8/3298228/osram_workshop_led_rf_sept2014.pdf