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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

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