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Forum: PCB Design & Technology PCB for High Power LEDs


Author: Ersin Oezalp (Company: BARAN) (baran-tech)
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Hello,

I have developed a high power UV-LED Array. Total loss of the PCB is 
about 200 Watts. The PCB is made from Aluminum and installed on a big 
heat-sink. The heat-sink is cooled with a high power FAN.

Unfortunately I can't cool down enough with the aluminum PCB. It can't 
transfer enough heat. I thought about using a ceramic PCB. Does anyone 
have experience with ceramic PCBs?
How are they attached to the heat-sink? Can I use screws?
Which type of thermal material is used between the PCB and the 
heat-sink?

Another question: Is there a way to manufacture an aluminum PCB directly 
on a heat-sink?

Regards,
Ersin

Author: hdd (Guest)
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Have you thought about using a petier element between the PCB and the 
heat-sink for a better heat transfer?

Author: Ersin Oezalp (Company: BARAN) (baran-tech)
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I didn't think about it since the current consumption will be too high.

Author: Fasti (Guest)
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Hello,

I don't think that a ceramic PCB will perform better. A Copperinlay 
might be the better way of coping with these high losses. You didn't 
tell us how big your PCB is.

regards

Fasti

Author: Ersin Oezalp (Company: BARAN) (baran-tech)
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Hello Fasti,
The PCB is 60x45 mm. However I can change its dimensions.
Attached is the MCPCB for 6 LEDs in PDF.
Thanks,
Ersin

Author: Carlos84 (Guest)
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Hi Ersin,

i know some cool experts for cooling.
please send me an email at
carlosde84 @ yahoo . com
as i am right your company is in krefeld. this is
40 km away from them.

regards

carlos

Author: Tim (Guest)
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Ersin Oezalp wrote:

> The PCB is 60x45 mm.
> Total loss of the PCB is about 200 Watts.

This ist not a cooling Problem.
Its obviously a design failure.

Author: water (Guest)
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Use water cooling- anything else will fail.

Author: Falk (Guest)
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@  Tim (Guest)

>> The PCB is 60x45 mm.
>> Total loss of the PCB is about 200 Watts.

>This ist not a cooling Problem.
>Its obviously a design failure.

Why? A Pentium CPU did/does dissipate around 100W over an area of 
roughly 10x10mm, cooled with a reasonable big heatsink and a fan.

For ceramic pcbs/heatsinks, look here

http://www.ceramtec.de/ceramcool/

>How are they attached to the heat-sink?

Solder

> Can I use screws?

Nope.

>Which type of thermal material is used between the PCB and the
>heat-sink?

Copper. There is no PCB anymore, just the isolating ceramic, copper 
layer, device.

Good luck.

Author: Michael D. (Guest)
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Why is the loss that high?

Is it only the LED's that create this heat or is there sonething like 
resitors, converters?

If it's only the LED`s I would be interessed how many of wich LED's you 
are using.

Author: Ersin Oezalp (Company: BARAN) (baran-tech)
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Thank you very much for your answers.

@water: We will design also water-cooled version of the lamp. But an 
air-cooled version is also required.

@Michael D.: Only LEDs are creating heat. I use 6x LZC UV Leds from 
company Ledengin. The next version will be 12 LEDs.

@Falk: Thanks. The idea with copper directly on ceramic heat-sink looks 
perfect. I will contact ceramtec tomorrow.

Author: Tim (Guest)
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Falk wrote:

> Why? A Pentium CPU did/does dissipate around 100W over an area of
> roughly 10x10mm

Thats right but a Pentium CPU integrates 3 Mio. of Transistors.
The PCB of the TS holds only 6 LEDs and loses 200W. Thats clearly a 
design error.

Author: Maddin (Guest)
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Maybe you should get in contact with Häusermann in Austria, they are 
specialized on this kind of PCBs.

http://www.haeusermann.at/2,product/22,HSMtec/35,L...


Best regards,

Martin

Author: A6AA (Guest)
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Hello Tim,

you wrote:
>Thats right but a Pentium CPU integrates 3 Mio. of Transistors.
>The PCB of the TS holds only 6 LEDs and loses 200W. Thats clearly a
>design error.

The LEDs mentioned here are most likely multi-die LEDs i.e. there are 
for example 10x10 dies on a ceramic interposer. The dies itself are high 
power dies. This means the design uses 600 LEDs. That's roughly 
1800V*LED. With 100W that's roughly 50mA per LED which ist not foo far 
out for high power LEDs. The only problem in such a desigh as 
highlighted by the TO is the heat in a small space. And if you think 
back to the Pentium: The Pentium of nowadays has an intelligent 
heat/Voltage management to reduce power consumption. You get your old PC 
(e.g. Celeron) a high perfonace task and the fan will spin up to 
decrease the Rth in order to get the heat away from the device. I'd 
guess that would be a nice feature :) for a lamp: you switch it on and 
as the lamp gets warmer a fan will start to enligthen the surrounding by 
its roaring noise :)

rgds

Author: Reinhard Kern (Guest)
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Hi,

did you ever work with a conventionel 500 Watt movie lamp? You would 
want to have a fan to cool it.

I am sure Ersin does not use a 100W output UV light sitting at his tv. 
This would be hazardous for his health.

Reinhard

Author: Jay Hughes (Guest)
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Our company manufactures many LED torch/flashlight designs for the 
Non-Aligned Military market.

We typically use arrays of 10W LEDs, some are 140cm diameter with 40 x 
10W LEDs, particularly in our drone bomb diverters. These units heat 
dissipation is way beyond alumim(i)um PCB capabilities.

Our PCBs are FR4 with holes sufficiently large for the rear ends of the 
LEDs to protrude into. Note: The use of LEDs with isolated heat 
dissipaters is required.

The heatsinks are thick alumin(i)um plates (5-15mm).

When the light assemblies are fabricated, generous dollops of heat 
conducting paste is applied to each exposed LED heatsink and when the 
faceplate - with the LEDs - is assembled to the alumin(i)um heatsink and 
secured with screws (mounting screws have to be distributed around the 
outer edge as well as in the central area) good thermal conductivity can 
be achieved.

Many of our IR 'illuminators' (as the military call them) have a 
sighting Laser unit in the centre position.

Where the application requires addition cooling, we simply add a 
computer CPU fan assembly to the rear of the thick heat sink.

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