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Regarding the Heat sink for High bright LEDs

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prakashvenugopal

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Hi,

I am trying to use the attached HB LEDS for my Lighting application. I have to placed the 25 LEDS one by one in the horizontal line. IF= 350mA and Vf= 3.2V. I have to dissipate the heat generated. so what type of heat sink i will go for this? Please let me know.

Thanks,
V. Prakash
 

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The datasheet mentions Thermal enhanced PCB.
Perhaps now a days some Aluminum substrate pcb is available with a sort of insulation and copper clad over it. Only such has to be used. i understand that one PCB house is able to make these pcbs once artwork is given. I spoke to them. perhaps shortly i suppose a member of that company to reply you here. All the best.
 
Last edited:
Hi,

Only aluminum substrate PCB can be used. No need for external heat sink to dissipate the heat.? Please let me know.


Thanks,
V. Prakash
 

I was searching for a way to service a similar PCB and , thanks that you gave a headway for me.
Al substrate pcb is , perhaps enough. i gathered that such pcb if locally made might cost at 5 times normal glass epoxy. refer my previous post and the pcb house is Bangalore based.
 

Those alluminium based PCB's are technically called "MPCB" which means PCB with a metal base. High bright led's like the 1 watter ones, generally develop instant heat at the junction when powered which will damage the chip if not sunk well. Thus these LED's are mounted over MPCB's to avoid immediate damage when connected to a power source. For testing purpose these MPCB's will of course act as an heatsink. But for a long run, a strong heatsink is highly recomended for the long life of the LED's. Any allunimium material / heatsink atleast 25-30 grams per watt may be calculated. More the better.
Cheers
 
Hi,

Many HB LEDS are manufactured with heat sink. When i use this type of Heatsink based HB leds, i dont want to use the external heat sink to dissipate the heat? or i have to use the external heat sink also to dissipate the heat?

epoxy PCB Having Heat sink with HB LEDS is enough will perform equal to Aluminum substrate PCB? Please let me know.


Thanks,
V. Prakash
 

prakashvenugopal said:
Hi,

Many HB LEDS are manufactured with heat sink. When i use this type of Heatsink based HB leds, i dont want to use the external heat sink to dissipate the heat? or i have to use the external heat sink also to dissipate the heat?

epoxy PCB Having Heat sink with HB LEDS is enough will perform equal to Aluminum substrate PCB? Please let me know.


Thanks,
V. Prakash
Click to expand...

The need for additional heatsinking beyond the MPCB depends on the environment the LED will be in. If this is mounted inside a freezer, then the PCB alone may be sufficient. However, if this is mounted outside in the desert where it reaches 110F, then additional heatsinking is a must. For any installation at room-temp or above, I'd have an additional heatsink behind the MPCB, as pranam suggested.

See if the LED vendor has an preferred suppliers of MPCBs... you may find a cheap source that way. I used some Luxeon Stars a few years ago, and used some pre-built MPCBs with the LEDs installed; they worked out quite well, since I didn't have to mess around with installation of the parts on a nasty heatsink (sucks the heat right out of your soldering iron tip).
 

if 6V0.3 amp filament bub and 0.3 amp lighting LED emit same amount of heat, perhaps Lot mote needs to be done to improve efficiency of LEDs especially the H H ones.
 

prakashvenugopal said:
Hi, Many HB LEDS are manufactured with heat sink. When i use this type of Heatsink based HB leds, i dont want to use the external heat sink to dissipate the heat? or i have to use the external heat sink also to dissipate the heat? epoxy PCB Having Heat sink with HB LEDS is enough will perform equal to Aluminum substrate PCB? Please let me know. Thanks, V. Prakash
Click to expand...
Do a simple experiment. Power your LED's with said voltage and proper current, and let them light for 5 minutes continuous. Now touch the centre of the MPCB at the back side. If you can bear the heat, Never ever use the heat sink. If you cant bear the heat, the LED is saying, i need a heat sink. Simple..DIY
Cheers
 

Hi,

Thanks for the replies.

Al substrate pcb is , perhaps enough. i gathered that such pcb if locally made might cost at 5 times normal glass epoxy. refer my previous post and the pcb house is Bangalore based.
Click to expand...

As sarma told, this metal pcb design will cost 5 times greater than the normal epoxy PCB.

Getting a readymade HB LED with heat sink is better than making our own PCB in PCB house.?
which is better from your views cost-wise?

Note: I had bought HB LED with heat sink(having Vf= 3.5V and IF= 350ma). I had powered the LED with full load that is 350mA. There is no that much heat observed.

Thanks,
V. Prakash
 

That is an intelligent approach to buy one from market.
everything we need not home-brew. How much did you pay for say 1 watt LED?

Incidentally imagine placing a Al Strip below the led. slightly bend the pins and solder to normal PCB. the AL strip can be held bty a drop of superglue to pcb to prevent movement and shorting led leads. there can be conductive paste between AL strip and LED at the centre tab.
 

Hi,

Yes. you are right. HB LED with heat sink cost Rs.45 per piece. So designing our own Al strip for heat sink is cheaper. But nearly 20 to 30 grams Al is needed to dissipate for 1 watt.


Thanks,
V. Prakash
 

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