Heat distribution in diode junction

[Winsu]

Hi All,

When a diode heats up because the current is flowing through it, what heat ups quicker ( or more), the Anode or the Cathode? Is there any difference between Schoktty diodes, fast diodes, signal diodes relevant to the previous question?

Winsu,
Regards

 

[KlausST]

Hi,

This headline is not meaningful at all. Please choose a suitable one.

Diode: Do a search for "peltier"

Klaus

 

[dick_freebird]

The heat will largely be shed at the junction between
anode and cathode because that's where the voltage
drop is (I*Rs adds, at the big end). You would need to
look at construction to say which is the larger and the
better-heat-sunk of the regions.

Schottky has a metal anode and the heat will be shed
in the silicon although the anode has no choice but to
follow, closely, as it's right at the junction. Schottkies
tend to have higher Rs due to no conductivity modulation,
and power Schottkies can have higher Vf@If than you'd
imagine from the low current datasheet number.

 

[Winsu]

Hi,

This headline is not meaningful at all. Please choose a suitable one.

Diode: Do a search for "peltier"

Klaus

I have had a look to Peltier effect and it took me the seebeck effect. It is literally from google:

"The Seebeck effect is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two substances"

That is basically what happens in a PN junction and it seems like the positive with more potential is the one that should get hotter.

 

[dick_freebird]

That is basically what happens in a PN junction and it seems like the positive with more potential is the one that should get hotter.

What makes you say this as a generality?

Current flows through both regions identically. The junction
forward voltage is a common central heater (I*V). The bulk
regions of the anode and cathode each have a series
resistance distributed heater as well (I^2*Rn, I^2*Rp).
Charge polarity is not represented in the power expressions.

At steady state which end of the diode sees the better thermal
path? Cathode to ground plane probably stays cooler than
anode to a skinny trace. Practicalities may trump theory
(even if theory is correct).