4 ms·

I'm always surprised we don't bother to heat sink the back side of CPUs and such. Sure it's a fraction of total heat output but enthusiasts care a lot about one

I'm always surprised we don't bother to heat sink the back side of CPUs and such. Sure it's a fraction of total heat output but enthusiasts care a lot about one or two degrees.

RF_Savage 4y ago
Hard to do when the backside is all pins or pads. But I do recall some serious overclockers having fans on the back of the mobo aimed at the socket and it's pins. But that was in,times just after breaking the 1GHz barrier. It was more popular with GPU's and many modern day GPU's do have a heatsink on the back side of the board as well.
fest 4y ago
The board area under CPU is usually filled with ceramic capacitors, not to mention the lack of ecosystem support (i.e. CPU vendors just cannot rely on everyone starting to provide additional cooling from the other side, so they have to design for the most common denominator). This method is sometimes used though, particularly with power transistors, where the heat conduction path through metal pads is usually better than the epoxy package over the die.
- jacquesm 4y ago
  CPUs are mounted 'upside down' in the die. So they are as close as they can get to the body of the cooler. Adding one to the bottom of the package wouldn't do all that much.
- formerly_proven 4y ago
  Power semiconductors in EP packages aren't flip chip, so the back of the die is glued to the main pad, and that's soldered to the PCB for SMD parts or mounted to a heatsink. Logic ICs are generally flip chip, so the back of the die points at the IHS / cooler.
hengheng 4y ago
It's a fraction, yes, but it's also delayed a lot. For a while the challenge has not been to remove heat from the general area, but to keep small spots from overheating within milliseconds. Cooling on the other side of the building does not play a big enough role for it to matter. (For enthusiasts, lowering environmental temperature would have the same effect.)
bismuthcrystal 4y ago
Next: we try to heat sink the sides of the CPU.
nicolaslem 4y ago
Nowadays GPUs do exactly that, they have thermal pads that connect the back of the PCB to a metal backplate. It is not clear whether this is actually necessary and not just for show.

I'm always surprised we don't bother to heat sink the back side of CPUs and such. Sure it's a fraction of total heat output but enthusiasts care a lot about one or two degrees.

RF_Savage 4y ago

Hard to do when the backside is all pins or pads. But I do recall some serious overclockers having fans on the back of the mobo aimed at the socket and it's pins. But that was in,times just after breaking the 1GHz barrier. It was more popular with GPU's and many modern day GPU's do have a heatsink on the back side of the board as well.

fest 4y ago

The board area under CPU is usually filled with ceramic capacitors, not to mention the lack of ecosystem support (i.e. CPU vendors just cannot rely on everyone starting to provide additional cooling from the other side, so they have to design for the most common denominator). This method is sometimes used though, particularly with power transistors, where the heat conduction path through metal pads is usually better than the epoxy package over the die.

jacquesm 4y ago
CPUs are mounted 'upside down' in the die. So they are as close as they can get to the body of the cooler. Adding one to the bottom of the package wouldn't do all that much.
formerly_proven 4y ago
Power semiconductors in EP packages aren't flip chip, so the back of the die is glued to the main pad, and that's soldered to the PCB for SMD parts or mounted to a heatsink. Logic ICs are generally flip chip, so the back of the die points at the IHS / cooler.

hengheng 4y ago

It's a fraction, yes, but it's also delayed a lot. For a while the challenge has not been to remove heat from the general area, but to keep small spots from overheating within milliseconds. Cooling on the other side of the building does not play a big enough role for it to matter. (For enthusiasts, lowering environmental temperature would have the same effect.)

bismuthcrystal 4y ago

Next: we try to heat sink the sides of the CPU.

nicolaslem 4y ago

Nowadays GPUs do exactly that, they have thermal pads that connect the back of the PCB to a metal backplate. It is not clear whether this is actually necessary and not just for show.