semi OT- removing plastic lens from LED

[George Herold]

Hi guys, Is there a fairly easy way to remove the plastic lens on the 'standard' 5mm through hole LED? I've used a file to get ~90% down to the element, but I'm afradi if I go further I'll wreck it.
I tried some acetone but it did nothing. A chemical would be nice, but hopefully *not* methylene chloride.

 

[Syd Rumpo]

Hi guys, Is there a fairly easy way to remove the plastic lens on the 'standard' 5mm through hole LED? I've used a file to get ~90% down to the element, but I'm afradi if I go further I'll wreck it.
I tried some acetone but it did nothing. A chemical would be nice, but hopefully *not* methylene chloride.

This may be folklore.

I often work with high-temperature stuff, and the wisdom is that you
can't use conventional LEDs at 180C because the lenses melt. I've never
needed to and haven't tried, but just maybe they'll soften sufficiently
to aid removal.

Some of the small SM ones seem to have Silicone lenses which it might be
possible to remove carefully under a microscope. Silicone oil will
soften Silicone rubber a little.

Cheers

 

[Spehro Pefhany]

Hi guys, Is there a fairly easy way to remove the plastic lens on the 'standard' 5mm through hole LED? I've used a file to get ~90% down to the element, but I'm afradi if I go further I'll wreck it.
I tried some acetone but it did nothing. A chemical would be nice, but hopefully *not* methylene chloride.

Try hot (~85'C) red fuming nitric acid. You said a chemical would be
nice, but that is not a nice chemical.

 

[Joerg]

Hi guys, Is there a fairly easy way to remove the plastic lens on
the 'standard' 5mm through hole LED? I've used a file to get ~90%
down to the element, but I'm afradi if I go further I'll wreck it. I
tried some acetone but it did nothing. A chemical would be nice, but
hopefully *not* methylene chloride.

Johne Wayne would have put the LED on a fence post, step back 30ft, draw
and pull the trigger.

When looking at the 5mm through-hole LEDs I have here they are all fully
encapsulated, "immersed in plastic". And as John said, with the
placement precision all over the map. Not sure what you are trying to
design but you may be better off buying bare die. I don't know them,
just as an example:

http://www.tech-led.com/LED_die_bare_chips.shtml

 

[George Herold]

Can't you buy a flat-end LED?

Well, I'm using this red led as a light sensor. I was taking some data on response vs light intensity. (using a yellow led as a light source) And then I tried a green led (as a source) And though there were more photons I got a lot smaller signal. WTF I thought to myself, well maybe the red palstice lens is absorbing all the green light. So I filed it down and increased the signal by a factor of 5 or so... Now if I could just get more of itoff...

One problem with the lens-end ones is that the chip placement isn't

When hitting this with a file I'm afraid I'll 'take out' the little bondingwire and that will be the end of it.

George H.

 

[George Herold]

This may be folklore.



I often work with high-temperature stuff, and the wisdom is that you
can't use conventional LEDs at 180C because the lenses melt. I've never
needed to and haven't tried, but just maybe they'll soften sufficiently
to aid removal.

Hmm OK maybe I can 'dig' around a bit with a soldering iron tip.
Thanks,

george H.

 

[George Herold]

Try hot (~85'C) red fuming nitric acid. You said a chemical would be

nice, but that is not a nice chemical.

"Arghhhh... Run Away!!" I've never heard of red fuming nitric acid but it sound like methyelene chloride would be safer.

George H.

 

[George Herold]

Johne Wayne would have put the LED on a fence post, step back 30ft, draw
and pull the trigger.

"I'd never shoot an LED in the back."

I guess I'm just going to have to settle for a bit of filing... I tried digging a bit out with the soldering iron and broke one.

George H.

 

[Ecnerwal]

"Arghhhh... Run Away!!" I've never heard of red fuming nitric acid but it
sound like methyelene chloride would be safer.

George H.

Run, don't walk, to your nearest library that keeps old books, and get a
copy of "Some Birds Don't Fly" for a fuller appreciation of RFNA (and
quite a few chuckles.)

 

[Spehro Pefhany]

"Arghhhh... Run Away!!" I've never heard of red fuming nitric acid but it sound like methyelene chloride would be safer.

George H.

Last time I went to Home Depot I didn't see any consumer grade
methylene chloride.. has it been outlawed or something?

 

[Joerg]

Why not a flat-lens surface-mount LED? Or a proper photodiode?

Yup. Or better yet, buy them with flat lenses:

http://uk.rs-online.com/web/p/photodiodes/7319225/

 

[Joerg]

You can get red LEDs in untinted packages.

Even whole tail light assemblies. But then you also need a lowering kit
and a major tchk tchk *BOOM* stereo.

 

[Spehro Pefhany]

https://dl.dropboxusercontent.com/u/53724080/Optos/LED_Sane.JPG

https://dl.dropboxusercontent.com/u/53724080/Optos/LED_Crazed.JPG

Acetone? Lacquer thinner?


Best regards,
Spehro Pefhany

 

[Lasse Langwadt Christensen]

Den fredag den 27. september 2013 00.54.12 UTC+2 skrev Phil Hobbs:

IPA will do that to many kinds of acrylic.

many types of acrylic craze and break in to little pieces
if it cleaned with any kind of alcohol

-Lasse

 

[hamilton]

Well, I'm using this red led as a light sensor.

Light Sensor ??

What does hacking an LED do that a regular "light sensor" won't do ??

h

 

[George Herold]

Light Sensor ??

What does hacking an LED do that a regular "light sensor" won't do ??
h

Well this is a bit embarrasing since it's written by my boss.
http://teachspin.com/newsletters/TeachSpin_MAY13FINALFOR WEB.pdf

But basically it detects single photons. Which is way cool for ~$0.10.

This is all old news, but there's been a redesign to the elecronics box.. adding a voltage source (lm317) some series resistors and an LED light source. Yellow led's are great and greens stink.. visible light led's seem OK..so the spectral response is mostly unknown.* (I need a monochrometer... Well maybe just a wideband light source.)

George H.
*like being mostly harmless.

 

[George Herold]

Run, don't walk, to your nearest library that keeps old books, and get a
copy of "Some Birds Don't Fly" for a fuller appreciation of RFNA (and
quite a few chuckles.)

Got it, I mostly found chemistry to be confusing.

George H.

 

[[email protected]]

This may be folklore.

I often work with high-temperature stuff, and the wisdom is that you
can't use conventional LEDs at 180C because the lenses melt. I've never
needed to and haven't tried, but just maybe they'll soften sufficiently
to aid removal.

180C? RoHS reflow solder processes go up to 260C. Yeah, a lot of
LEDs melt there, but...

 

[[email protected]]

"Arghhhh... Run Away!!" I've never heard of red fuming nitric acid but it sound like methyelene chloride would be safer.

RFNA is rocket fuel (specifically an oxidizer). It's truly nasty
stuff.

 

[Spehro Pefhany]

IPA will do that to many kinds of acrylic.

Cheers

Phil Hobbs

I've seen stress corrosion cracking in acrylic when PCBs were cleaned
with certain solvents. Nothing like the visible crazing but where
there were stress risers (eg. threads) cracks would gradually
propagate. This was in some very nice clear acrylic moldings we had
made for instrument faces. The problem was solved by baking off the
boards to remove small amounts of residual volatiles before assembly.



Best regards,
Spehro Pefhany