This thermal grease is really cool!

On the one hand you have active here, be careful not to spread the material out of the CPU surface - on the motherboard, this may result in short circuits - on the other hand this material has a tendency to stay together like mercury. The handling is so unusual, but really easy and the effect is very efficient. In addition, the possibility that this material is hardened over years and crumbly omitted, and thus immensely diminishes in its effect.
In my opinion, the best connection between the CPU and heatsink, but not for copper suitable.