[PEDA] Thermal Impedance of Copper Areas

[Linden]

To Brad and David,

Thanks for the replies.
The info you suggested was exactly what I was after.

It would appear that utilising the PCB copper as a heatsink doesn't help
greatly once you get above a certain area.
I guess this is due to the low cross section available for conduction
with 1oz. copper.
Even so, it might afford sufficient improvement to help in my application.

Thanks again,

Linden


Brad Velander wrote:
> Linden,
> 	You can also glean some tidbits of information from a number of Linear Technology datasheets and application notes for their regulators. A couple that I know contain some related information which may help you are:
> LT1763C, LT1963  or LT1175I.
>
> 	I know there was another LT regulator that had a fairly extensive section on comparing relative thermal dissipations with varying copper areas, but I could not find it at this time. Ooops it wasn't Linear Technologies I was looking for, I just stumbled onto the one I was thinking of. It was for the LM1117 device from National Semi. It shows varying copper areas and patterns, showing the effects of varying the copper area and pattern on dissipation.
>
> Sincerely,
> Brad Velander
> Senior PCB Designer
> Northern Airborne Technology
> #14 - 1925 Kirschner Road,
> Kelowna, BC, V1Y 4N7.
> tel (250) 763-2232 ext. 225
> fax (250) 762-3374
>
>
>
> -----Original Message-----
> From: Linden [mailto:ldoyle at zener.net]
> Sent: Wednesday, July 26, 2006 5:25 PM
> To: PEDA at techservinc.com
> Subject: [PEDA] Thermal Impedance of Copper Areas
>
>
> Greetings All,
>
> Can anyone direct me to information on the relationship between copper
> area and thermal impedance for SMD devices?
>
> I have a D2PAK MOSFET that has a Thermal impedance of 40K/W junction to
> ambient when mounted with a minimum of copper on the mounting tab..
> I'd like to reduce this figure by adding a copper area (polygon or fill)
> to the mounting tab.
> The problem is I don't have a feel for how much copper is needed for a
> particular reduction in thermal impedance.
>
>
> Thanks in advance,
>
> Linden Doyle
> Browse or Search Current Archives (2004-Current):
> http://www.mail-archive.com/peda@techservinc.com
>
>
>
> ____________________________________________________________
> You are subscribed to the PEDA discussion forum
>
> To Post messages:
> mailto:PEDA at techservinc.com
>
> Unsubscribe and Other Options:
> http://techservinc.com/mailman/listinfo/peda_techservinc.com
>
> Browse or Search Old Archives (2001-2004):
> http://www.mail-archive.com/proteledaforum@techservinc.com
>
> Browse or Search Current Archives (2004-Current):
> http://www.mail-archive.com/peda@techservinc.com
>
>
> .
>
>