4 ms·
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
by 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 agoCPUs 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 agoPower 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.