How come thermal paste isn't recommended on VRMs?

[ybriK]

Even if the paste is electrically non-conductive how come it isn't recommended to use on VRMs?

[Stefan1024]

It is fine for the VRMs, but when the cooler touches the core and the VRMs, you can only mount it to one point (to core obviousely). Due to tolaerance in manucaturing, you have a gap at the other point, so you need a soft thermal pad. Screwing down the cooler at both points would bend the PCB.

[ybriK]

3 minutes ago, Stefan1024 said:

It is fine for the VRMs, but when the cooler touches the core and the VRMs, you can only mount it to one point (to core obviousely). Due to tolaerance in manucaturing, you have a gap at the other point, so you need a soft thermal pad. Screwing down the cooler at both points would bend the PCB.

I have these little aluminum heatsinks to cool my VRMs but don't have any thermal tape so I put a small drop of thermal paste on each VRM so that I can have some form of "sticky contact". Do you think I should have thermal pads on my VRMs? Or Is Thermal Paste + Heatsink combo fine?

[Stefan1024]

5 minutes ago, ybriK said:

I have these little aluminum heatsinks to cool my VRMs but don't have any thermal tape so I put a small drop of thermal paste on each VRM so that I can have some form of "sticky contact". Do you think I should have thermal pads on my VRMs? Or Is Thermal Paste + Heatsink combo fine?

I recommend pads, as the MOSFETs thend to have a bit different hight due to the soldering process. A thermal pad can eaqualize the mounting preassure while the paste can not.

[ThomasD]

I'd also be a little concerned that vibration from the fan might cause sinks only held on by regular TIM to migrate or even fall off.  The stuff gets pretty darn thin when it's hot.