Thermal Conductivity

[ziggyfish]

Simple question, I can't seem to find the answer to.

I know with heatsinks, the higher the thermal resistance, the less heat gets dissipated from the component.

Am I right in thinking, that the higher the thermal conductivity, the more heat that gets transferred from the component to the heat sink Thermally conductive material?

I.e With thermal conductivity, more is better. 0.8 W/(m.K) > 0.682 W/(m.K)

Thanks

Brendan

[Brumby]

Thermal resistance is the inverse of thermal conductivity ... and vice versa.

Am I right in thinking, that the higher the thermal conductivity, the more heat that gets transferred from the component to the heat sink Thermally conductive material?

I.e With thermal conductivity, more is better. 0.8 W/(m.K) > 0.682 W/(m.K)

Dave has done a video that might be helpful....

[IanB]

Simple question, I can't seem to find the answer to.

I know with heatsinks, the higher the thermal resistance, the less heat gets dissipated from the component.

Am I right in thinking, that the higher the thermal conductivity, the more heat that gets transferred from the component to the heat sink Thermally conductive material?

I.e With thermal conductivity, more is better. 0.8 W/(m.K) > 0.682 W/(m.K)

There are two separate concepts that are important to know. One is thermal conductivity, the other is the heat transfer coefficient.

Thermal conductivity relates to heat transfer through the interior of a material. As such it is analogous to electrical conductivity.

Heat transfer coefficients relate to heat transfer across the boundary between materials, for example between the surface of the component and the heat sink, or between the surface of the heat sink and the free air around it. An electrical analog might be an oxide layer on the surface of a contact.

Often the heat transfer coefficient is the more limiting factor. Even if the heat sink material has a high thermal conductivity (like aluminium or copper), this is all for nothing if the heat cannot escape the surface of the heat sink into the surrounding air. Heat transfer is promoted by large surface area, fins, and forced air currents (fans).

For basic design purposes all the resistances to heat flow tend to get combined into an effective system resistance, which is why you don't tend to see heat transfer coefficients mentioned in datasheets. But these details are known to the engineers who design heat sinks.

[Ice-Tea]

Most important thing: the amount of heat stats the same, no matter the heatsink. In electricity terms, it's a constant current source (heatflow), not a constant voltage source (temperature).