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Luxeon Star ?

J

Jorge Omar

Jan 1, 1970
0
Hello,

Could someone inform if the die is insulated from the mounting plate in the
Star or is it necessary to use insulation between LED and heathsink?

Thanks,

Jorge
 
W

Winfield Hill

Jan 1, 1970
0
Jorge Omar wrote...
Could someone inform if the die is insulated from the mounting plate in
the Star or is it necessary to use insulation between LED and heathsink?

I know the smaller individual high-output Luxeon LEDs are isolated
from the metal heat-sink plate.

Thanks,
- Win

whill_at_picovolt-dot-com
 
M

Mikael Ejberg Pedersen

Jan 1, 1970
0
Both Star and bare Emitter are isolated from the base.

I have some bare emitters, and they are NOT isolated.
The base on my red an yellows are directly in contact with the anode.
And on my green and blue, the bases have a parasitic pn-unction to the
cathode.
I don't have any Stars to test on at the moment.

Regards,
Mikael
 
R

R.Lewis

Jan 1, 1970
0
Adam Aglionby said:
Both Star and bare Emitter are isolated from the base. No such thing as too
big a heatsink with them.
LED fan? have a look at :

The Emitters are *NOT* isolated from their bases - see the datasheet!
 
J

Jorge Omar

Jan 1, 1970
0
Thanks!
I've looked at the datasheet, but did not look close enough to the right
side banner...

Jorge
 
S

S.M.Taylor

Jan 1, 1970
0
R.Lewis said:
The Emitters are *NOT* isolated from their bases - see the datasheet!
A pain isn't it ? I suppose it gets the junction/base thermal
resistance down though.

Steve
 
I

Ian Stirling

Jan 1, 1970
0
Mikael Ejberg Pedersen said:
I have some bare emitters, and they are NOT isolated.
The base on my red an yellows are directly in contact with the anode.
And on my green and blue, the bases have a parasitic pn-unction to the
cathode.
I don't have any Stars to test on at the moment.

I have dissasembled an emitter, to mount it on a sapphire baseplate.

From memory.

There is a 3mm dia *8mm copper bar, with a 7mm dia*4mm height copper cylinder
on the end.

Onto the narrow end is soldered a hexagonal base, on which is mounted the
emitter chip. From the emitter come a couple of gold bondwires which
connect to two segments of copper that are wrapped round the copper bar
just after it narrows. These are connected to the terminals.

On top of the bar is a hemispherical shell of acrylic (?) filled with
clear silicone.
If you want to, you can pull the acrylic lens off, and get access to the
chip.

I'm unsure how the phosphor is attatched.
 
J

Jorge Omar

Jan 1, 1970
0
Yes, I will be mounting 3 different colors in the same heathsink.
Oh, well...

When I get the parts, I will see if the same side (anode or cathode) is
in contact with the base.
If so, maybe I will redesign the driver.

Jorge
 
A

Adam Aglionby

Jan 1, 1970
0
Jorge Omar said:
Yes, I will be mounting 3 different colors in the same heathsink.
Oh, well...

When I get the parts, I will see if the same side (anode or cathode) is
in contact with the base.
If so, maybe I will redesign the driver.

Jorge

Posting before first coffee of day , doh!

From experience do not rely on the emitter slug to be any particular
connection....
What should have said is that the emitters are not consistently and reliably
connected to their slug.
My thanks to R Lewis for correcting this before any LSs were smoked.

The emitter slug is silver plated and solderable, perhaps not reccomended
but possible.

Interesting thought about detaching the chip and remounting it on a sapphire
substrate, just wait for commercial diamond production to ramp up, then can
really get into overdriving.

Adam
 
A

Adam Aglionby

Jan 1, 1970
0
Jorge Omar said:
Yes, I will be mounting 3 different colors in the same heathsink.
Oh, well...

When I get the parts, I will see if the same side (anode or cathode) is
in contact with the base.
If so, maybe I will redesign the driver.

Jorge

Posting before first coffee of day , doh!

From experience do not rely on the emitter slug to be any particular
connection....
What should have said is that the emitters are not consistently and reliably
connected to their slug.
My thanks to R Lewis for correcting this before any LSs were smoked.

The emitter slug is silver plated and solderable, perhaps not reccomended
but possible.

Interesting thought about detaching the chip and remounting it on a sapphire
substrate, just wait for commercial diamond production to ramp up, then can
really get into overdriving.

Adam
 
I

Ian Stirling

Jan 1, 1970
0
Posting before first coffee of day , doh!

From experience do not rely on the emitter slug to be any particular
connection....
What should have said is that the emitters are not consistently and reliably
connected to their slug.
My thanks to R Lewis for correcting this before any LSs were smoked.

The emitter slug is silver plated and solderable, perhaps not reccomended
but possible.

Interesting thought about detaching the chip and remounting it on a sapphire
substrate, just wait for commercial diamond production to ramp up, then can
really get into overdriving.

Yep.
The sapphire substrate isn't very good, it's about a tenth of the
thermal conductivity of copper. (this is countered by the fact that it's
a better shape than the long bar of the emitter)
However, copper isn't transparent, and I'm using a reflector to bounce
light back past the LED.
For a rather silly upgrade to a minimag solitare.

I'd really like to use diamond, but it's only really a bit better at
these sorts of power densities.
Sapphire does 40W/m/K, diamond 2000W/m/K.
The chip is around 2mm square.
80mw/2mm/K.
So the cube behind the chip adds around 12C, and the four in contact
with it around 3C, and the the rest maybe another couple.
So, call it 17C rise for a watt, for a 4mm thick infinite disk.
Diamond would be interesting to try to overdrive it, but in this case,
sapphire is just fine.
 
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