Solution for clearing LED epoxy on emitter? - Page 1
Forum section: electronics / beginners

author: steveggz
author_rank: Contributor
timestamp: March 21, 2018, 06:05:04 am
content: While soldering Cree XT-E surface mount LEDs I managed to get rosin flux on the epoxy/plastic coating of the emitter (see attached pictures). Has anyone successfully managed to clear up that coating? I've tried everything from 91% alcohol and scrubbing to acetone and even polishing it with a dremmel and buffing wheel. I tried all this on a spare Cree LED to see if it would work and nothing worked.Is there anything I can do or is that plastic epoxy coating damaged for good?As soon as the alcohol or liquids I use to clean it evaporate the coating becomes frosted and unclear. Is there anything I can put over it like a coat of lacquer to keep it clear. Or epoxy?

author: ivaylo
author_rank: Frequent Contributor
timestamp: March 21, 2018, 06:16:48 am
content: Nah, plastic can be polished... Unless you overheated it or something. How many RPM do you run your Dremel at? I assume you are aware of products like thesehttps://www.amazon.com/gp/product/B002UD0GGS

author: Gyro
author_rank: Super Contributor
timestamp: March 21, 2018, 12:32:36 pm
content: Your best action would have been to check the manufacturer's website for cleaning methods before you started, specifically the soldering and handling instructions:http://www.cree.com/led-components/media/documents/XLamp_XT_SH.pdfQuoteIt sounds as if you didn't use sufficient passes of the IPA (hopefully it was IPA) to completely remove the flux residue, if there was any left then, yes it would have gone cloudy again as it dried. I think the Acetone will have softened the plastic and permanently crazed the surface. I doubt if Dremmels feature anywhere in the proper handling procedures- best case, you will change the lens profile, it would be advisable to short each one to avoid static damage too.I'd say, at this point, you'd be best off replacing them.

author: steveggz
author_rank: Contributor
timestamp: March 21, 2018, 12:43:15 pm
content: I tried Meguiars ultra cut compound. I used the lowest setting on my Dremmel but it basically shaved down the led coating to a flat one. I think the plastic coasting is too soft to polishThanks Gyro, I actually used both of their recommended cleaning solutions with no luck. I only tried the more harmful ones in a attempt to salvage them but they also didn't work. It seems the rosin flux either baked on the lens or chemically changed the surface of the emitter coating.

author: jmelson
author_rank: Super Contributor
timestamp: March 21, 2018, 07:19:55 pm
content: Quote from: steveggz on March 21, 2018, 06:05:04 amI suspect the acetone has partially melted the plastic. It will take some buffing with polishing compound to remove all the frosted surface. This will change the shape of the dome, so the light pattern will be altered. If that is not a problem, then go at it.Acetone is really hard on most plastics.Jon

author: rdl
author_rank: Super Contributor
timestamp: March 22, 2018, 05:37:26 pm
content: Assuming the plastic was crystal clear originally, a thin coat of clear acrylic such as Krylon, or even clear nail polish will mostly fix it. Why does it need to be clear (just curious)?

author: Habropoda
author_rank: Regular Contributor
timestamp: March 22, 2018, 06:43:02 pm
content: The lens is not plastic epoxy; it is silicone. It is slightly rubbery. It is unlikely that polishing will help.Exactly which rosin flux are you using? Try a long soak in IPA; a couple of hours or even a full day.

author: rdl
author_rank: Super Contributor
timestamp: March 22, 2018, 06:46:51 pm
content: Ah, well if it's silicone you can probably forget about using any kind of clear paint on it - most likely nothing will stick to it.