air bubble in LEN lens
- Thread starter Richardli
- Start date
Help Support Candle Power Flashlight Forum
jeffosborne
Enlightened
Hi Richardli! I have used dozens of K2's for various projects and never seen a bubble in the lens. But I imagine that sort of defect can't help but distort the smooth dispersion of light. Makes me wonder if you have found some knock-off K2's. Where did you buy yours? Cheers, Jeff
We use K2 in our production and buy from future electronics and found these bubbles after soldering. These air bubbles might happened after went through high temperature. I don't know if it is was a prcess defect from lumileds which showed up through high temperature.
These bubbls seem all underneath the jel lens and not in the optical path. What are the potential quality problems?
I hope I can get some advice from this very hepful website.
These bubbls seem all underneath the jel lens and not in the optical path. What are the potential quality problems?
I hope I can get some advice from this very hepful website.
Th232
Flashlight Enthusiast
Bit of a long shot, but how well did you bake the LEDs prior to soldering them?
fyrstormer
Banned
If these bubbles are caused or exposed by the heat of soldering, there's another good reason to be using thermal epoxy instead -- the other reason being to allow for LED replacement in the future.
jeffosborne
Enlightened
I am just curious - what product are you producing Richardli? And, now that K2 is discontinued, what LED will you use when the K2 is gone?
Thanks,
Jeff O.
Thanks,
Jeff O.
Illum
Flashaholic
the K2 IIRC is a hard dome, not a soft dome jelly
I've never had issues with the dome part during fabrication, installation, or assembly. I have more than once burned a leg off accidently:shrug: [the 150W iron was pitched and a variable 50W bought]. Perhaps there was an air bell in the epoxy dome and the heat caused it to develop fissures in the dome?
If the bubble is spead out a wide area underneath the dome and close to the substrate it is likely that the dome seared off the K2 sometime during fabrication. Its probably held in place by the dome material around the bond wires. Excessive heat, laterial shear, or dropping the LED against a hard surface can all contribute to the damage of the dome.
I've never had issues with the dome part during fabrication, installation, or assembly. I have more than once burned a leg off accidently:shrug: [the 150W iron was pitched and a variable 50W bought]. Perhaps there was an air bell in the epoxy dome and the heat caused it to develop fissures in the dome?
If the bubble is spead out a wide area underneath the dome and close to the substrate it is likely that the dome seared off the K2 sometime during fabrication. Its probably held in place by the dome material around the bond wires. Excessive heat, laterial shear, or dropping the LED against a hard surface can all contribute to the damage of the dome.
Last edited:
The dome has a hard shell and an optical gel behind that so it really is both. Also using Norland in this manner is a very bad idea. The bubbles probably are almost certainly from soldering as was mentioned already. If the parts have sat around for a while after being out of the sealed bag they absorb atmospheric moisture. When heated to solder that moisture turns to steam and creates those pockets or bubbles. These LEDs must be baked before using to keep this from happening anymore. OP Look in the data sheets and you should find instructions on how to do this.
Illum
Flashaholic
HarryN
Flashlight Enthusiast
Hi, I suggest calling Future and ask them to advise you on the situation. You probably don't want to hear it, but I think the parts are scrap. I would desolder the parts and replace them using a lower temperature solder and proper pre-bake.
You can probably get a good idea of the real problem level with some burn in testing. Get some that you are certain are properly soldered. Run the "konwn good" vs "potential problem" side x side at 2.5 amps for 1 month. The failure mode is likely to show up, but at least you can estimate how bad the problem is.
Christexan
Enlightened
- Joined
- Sep 29, 2006
- Messages
- 224
Beating the dead horse here, but it was almost certainly not a product defect, but a defect in your process that caused the issue.
If you receive, or store, the LEDs outside of the "factory sealed" packaging, the minute they are open they start absorbing moisture (each type is different, have to read the mfger specs).
For instance, Cree XR-Es, going from memory here, have a shelf life of "x" months while in factory packaging. But if opened (cut reel for instance, even though they are still in their pick-and-place packaging, they are no longer atmospherically sealed), it is something like 72 hours maximum exposure before re-baking is required.
Baking (at a low temp, XR-E I think is 80C) for 24 hours to drive out the moisture is REQUIRED to avoid potential bubbles during reflow.
I've personally seen this, when reflowing XR-Es, spotted the bubbles forming (saw through the lens, and the lens itself moved a little) (quickly cooled the oven to prevent further problems and the bubble re-sealed itself in that case thankfully, it happened right at the reflow point).
Bottom line, it's not a product defect, you just have to process it correctly first, if you buy a full factory pack, and open it, you have to use them ALL within x amount of hours (not days or weeks, etc), or else bake the moisture out before using after x hours of atmospheric exposure.
Read the mfger datasheets for JEDEC storage parameters and handling procedures, and treat accordingly. (I've never had a need for K2s so I can't give specifics on their parameters, I have the spec sheets in my parts binder at the home office, I've mostly used XR-Es, so that's my example).
24 hours baketime in this example is "worst case" of course, if they have a 72-hour "open" shelf life, and it's 84 hours later, you might get away with only pre-baking 1-2 hours, but that's a judgement call that wouldn't be in accordance with the manufacturer (meaning you wouldn't have a legitimate claim if it has problems). If you bought a partial reel (by definition, it is "open"). You don't know how long it was open before shipment, how long (and what conditions) it's been through during the process, etc (sitting on a dock by the ocean for 8 hours could saturate the suckers), so unless you have a brand-new factory-sealed reel that has been opened on-site and kept in low-humidity conditions for less than a few days, baking is a MUST to be safe. Might work 100 times without doing so, but if it fails a few times, it's not Lumileds fault that procedures weren't followed.
If you HAVE done all that properly, then take it up with Future or Lumileds. Good luck!
If you receive, or store, the LEDs outside of the "factory sealed" packaging, the minute they are open they start absorbing moisture (each type is different, have to read the mfger specs).
For instance, Cree XR-Es, going from memory here, have a shelf life of "x" months while in factory packaging. But if opened (cut reel for instance, even though they are still in their pick-and-place packaging, they are no longer atmospherically sealed), it is something like 72 hours maximum exposure before re-baking is required.
Baking (at a low temp, XR-E I think is 80C) for 24 hours to drive out the moisture is REQUIRED to avoid potential bubbles during reflow.
I've personally seen this, when reflowing XR-Es, spotted the bubbles forming (saw through the lens, and the lens itself moved a little) (quickly cooled the oven to prevent further problems and the bubble re-sealed itself in that case thankfully, it happened right at the reflow point).
Bottom line, it's not a product defect, you just have to process it correctly first, if you buy a full factory pack, and open it, you have to use them ALL within x amount of hours (not days or weeks, etc), or else bake the moisture out before using after x hours of atmospheric exposure.
Read the mfger datasheets for JEDEC storage parameters and handling procedures, and treat accordingly. (I've never had a need for K2s so I can't give specifics on their parameters, I have the spec sheets in my parts binder at the home office, I've mostly used XR-Es, so that's my example).
24 hours baketime in this example is "worst case" of course, if they have a 72-hour "open" shelf life, and it's 84 hours later, you might get away with only pre-baking 1-2 hours, but that's a judgement call that wouldn't be in accordance with the manufacturer (meaning you wouldn't have a legitimate claim if it has problems). If you bought a partial reel (by definition, it is "open"). You don't know how long it was open before shipment, how long (and what conditions) it's been through during the process, etc (sitting on a dock by the ocean for 8 hours could saturate the suckers), so unless you have a brand-new factory-sealed reel that has been opened on-site and kept in low-humidity conditions for less than a few days, baking is a MUST to be safe. Might work 100 times without doing so, but if it fails a few times, it's not Lumileds fault that procedures weren't followed.
If you HAVE done all that properly, then take it up with Future or Lumileds. Good luck!
Last edited:
