Heatsinks need to be mounted directly to the heat-producing chip for the most efficient removal of heat from the device. Heatsinks are mounted on a chip in various ways.
In addition to different mounting styles for heatsinks, heatsinks can come with different styles of fins. The style of fin affects the performance as well as price. Heatsinks have fins and the fins are the method by which the heatsink removes heat from a device. The fins have different shapes depending on the manufacturing method.
Here is an example of Genesis heatsink design that solves the heat transfer problem from high speed chips that are shielded. This method has a two piece shield over the chip and a cutout in the shield cover that allows the heatsink to touch the chip directly. This is a much more efficient method to remove heat from the chip as compared to mounting a heatsink on top of a shield. DDR3 memory is also inside the shield.
To learn more please download the Genesis Heatsink presentation, which includes further examples of the Genesis Heatsink/shield solution. Genesis custom-design heatsinks for unique customers/applications with a fast turnaround for design and production parts and low-cost tooling.