Cooling of SO8

H

Heindorf

Guest
Hi,
I'm using a TC4420-SMD as a gate driver ( 15V, 100kHz, Qg=0.8ľC, Rg=5
Ohm). Now the board is finished and the creature gets pretty hot despite
a little heatsink glued on top.Is there a pin-compatible IC available
with perhaps a higher power dissipation and/or lower output impedance?
Is there a better way to cool down the case ( no fan)?
Rolf
 
Heindorf wrote:
Hi,
I'm using a TC4420-SMD as a gate driver ( 15V, 100kHz, Qg=0.8ľC, Rg=5
Ohm). Now the board is finished and the creature gets pretty hot despite
a little heatsink glued on top.Is there a pin-compatible IC available
with perhaps a higher power dissipation and/or lower output impedance?
Is there a better way to cool down the case ( no fan)?
Click to expand...
The usual way with little SM devices is to track out the ground pins to
an appreciable area of copper on the PCB, the leads and solder being
much more thermally conductive than the plastic case.

Paul Burke
 
Paul Burke schrieb:

Heindorf wrote:
Hi,
I'm using a TC4420-SMD as a gate driver ( 15V, 100kHz, Qg=0.8ľC, Rg=5
Ohm). Now the board is finished and the creature gets pretty hot despite
a little heatsink glued on top.Is there a pin-compatible IC available
with perhaps a higher power dissipation and/or lower output impedance?
Is there a better way to cool down the case ( no fan)?

The usual way with little SM devices is to track out the ground pins to
an appreciable area of copper on the PCB, the leads and solder being
much more thermally conductive than the plastic case.

Paul Burke
Click to expand...
Hello,
that's not a bad proposal and I'll consider this at any rate the next time.
Currently there is little space available and the board is finished. BTW the
frequency is 50 kHz ( two stages alternately switched on) and I calculate
approx. 0.3W for each driver. With 25°C and the small heatsink it's tolerable,
I think. But at 70 °C I've doubts.
Rolf
 
"Heindorf" <heindorf@aeras.de> wrote in message
news:41B5988A.9662F4C4@aeras.de...
Paul Burke schrieb:

Heindorf wrote:
Hi,
I'm using a TC4420-SMD as a gate driver ( 15V, 100kHz, Qg=0.8ľC, Rg=5
Ohm). Now the board is finished and the creature gets pretty hot
despite
a little heatsink glued on top.Is there a pin-compatible IC available
with perhaps a higher power dissipation and/or lower output impedance?
Is there a better way to cool down the case ( no fan)?

The usual way with little SM devices is to track out the ground pins to
an appreciable area of copper on the PCB, the leads and solder being
much more thermally conductive than the plastic case.

Paul Burke

Hello,
that's not a bad proposal and I'll consider this at any rate the next
time.
Currently there is little space available and the board is finished. BTW
the
frequency is 50 kHz ( two stages alternately switched on) and I calculate
approx. 0.3W for each driver. With 25°C and the small heatsink it's
tolerable,
I think. But at 70 °C I've doubts.
Click to expand...
I don't know the device. But generally you should go for power packages for
power devices. Ie. SO8 with an exposed thermal pad under it (which you
solder directly to a copper fill with thermal vias to a plane). 0.3W is
nothing - if you have problems even with a heatsink I guess you calculated
wrongly ;-)

/A

Rolf
Click to expand...
 
On Tue, 07 Dec 2004 12:07:09 +0100, Heindorf wrote:

Hi,
I'm using a TC4420-SMD as a gate driver ( 15V, 100kHz, Qg=0.8ľC, Rg=5
Ohm). Now the board is finished and the creature gets pretty hot despite
a little heatsink glued on top.Is there a pin-compatible IC available
with perhaps a higher power dissipation and/or lower output impedance?
Is there a better way to cool down the case ( no fan)?
Rolf
Click to expand...
You didn't say what kind of glue. You can get thermally conductive epoxy,
but it's a little expensive.

Good Luck!
Rich
 
Rich Grise wrote:
On Tue, 07 Dec 2004 12:07:09 +0100, Heindorf wrote:


Hi,
I'm using a TC4420-SMD as a gate driver ( 15V, 100kHz, Qg=0.8ľC, Rg=5
Ohm). Now the board is finished and the creature gets pretty hot despite
a little heatsink glued on top.Is there a pin-compatible IC available
with perhaps a higher power dissipation and/or lower output impedance?
Is there a better way to cool down the case ( no fan)?
Rolf


You didn't say what kind of glue. You can get thermally conductive epoxy,
but it's a little expensive.

Good Luck!
Rich
Click to expand...
My experience with "thermal conductive" epoxy suggests it should be
called "less thermally insulating" epoxy. Its a lot better than an
ordinary epoxy, but absolutely ratshit compared to, say, clamping the
parts together - by an order of magnitude at least.

Cheers
Terry
 
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