Luxeon emitters

[R.Lewis]

Once upon a time the heatsinking 'slug' on the Luxeon emitters was not
electrically isolated from somewhere/something dark and secret within its
'innards and the datasheet/appnotes informed of this fact - detailing that
the slugs must be electrically isolated from each other .

Recently I have noticed that the slugs appear to be electrically isolated
from the anode and cathode connections although I can find no Lumileds
reference to this fact.

Anyone know anything about this?

Regards.

 

[Leon Sorokin]

i pulled an blue High Dome emitter off the star base just yesterday. I did a
continuity test and it seems to be isolated from both. i havent cleaned the
slug yet from the epoxy that held it on though. but i'm pretty confident of
the fact.

Leon

"R.Lewis" <h.lewis@connect-2.co.uk> wrote in message
news:3551u7F4j9l0gU1@individual.net...

Once upon a time the heatsinking 'slug' on the Luxeon emitters was not
electrically isolated from somewhere/something dark and secret within its
'innards and the datasheet/appnotes informed of this fact - detailing that
the slugs must be electrically isolated from each other .

Recently I have noticed that the slugs appear to be electrically isolated
from the anode and cathode connections although I can find no Lumileds
reference to this fact.

Anyone know anything about this?

Regards.

 

[Don Klipstein]

In article <3551u7F4j9l0gU1@individual.net>, R.Lewis wrote:

Once upon a time the heatsinking 'slug' on the Luxeon emitters was not
electrically isolated from somewhere/something dark and secret within its
'innards and the datasheet/appnotes informed of this fact - detailing that
the slugs must be electrically isolated from each other .

Recently I have noticed that the slugs appear to be electrically isolated
from the anode and cathode connections although I can find no Lumileds
reference to this fact.

Anyone know anything about this?

I have noticed that some Luxeons have isolated heatsinking and some do
not. If the datasheet does not say anything in this area about a
particular part number, assume that the manufacturer reserves the right to
change that characteristic of that part number and be prepared for the
worst.

- Don Klipstein (don@misty.com)

 

[Zak]

Don Klipstein wrote:

I have noticed that some Luxeons have isolated heatsinking and some do
not. If the datasheet does not say anything in this area about a
particular part number, assume that the manufacturer reserves the right to
change that characteristic of that part number and be prepared for the
worst.

There may be different production lines or an old batch may appear on
the market, indeed.


Thomas

 

[Ian Stirling]

In sci.engr.lighting R.Lewis <h.lewis@connect-2.co.uk> wrote:

Once upon a time the heatsinking 'slug' on the Luxeon emitters was not
electrically isolated from somewhere/something dark and secret within its
'innards and the datasheet/appnotes informed of this fact - detailing that
the slugs must be electrically isolated from each other .

Recently I have noticed that the slugs appear to be electrically isolated
from the anode and cathode connections although I can find no Lumileds
reference to this fact.

Anyone know anything about this?

Posted this before, it does not seem to havge appeared.

The LED chip is glued onto the copper slug.
If they change from conductive-non-conductive glue, or the chip sits slightly
skew, with one corner touching the mount through the glue, it could be
conductive.

 

[LEDlights]

The slug is electrically connected to the substrate comprising 2
inverse series zener diodes, this explains why you cannot measure with
an ohm meter. See the Lumileds document RD25.pdf
http://www.lumileds.com/pdfs/RD25.PDF

Each zener may be in the range of 5v - 10v so it will not usually show
a problem in low voltage applications.

Pat