The images shown here are from an actual tear-down of a computer. They were taken from a forum where a perturbed PC technician replaced the thermal interface material shown with a more conductive material. This was done to encourage his one week old computer to run cooler.
As illustrated, the interface material was a grease. For some devices, the performance of grease is good enough. Grease is gooey though. It was and is not formulated to be dispensed in the volume that this PC manufacturer used.
The good news is that by applying a more conductive interface with a much thinner bondline, the logic board was tested to run 20C cooler than with the previous interface material.