3. Apply thermal interface material (TIM). New retail processors usually come with heatsinks that
have preapplied TIM (see Figure 19.9). Some vendors cover the TIM with protective tape that
must be removed before installing the heatsink. You cannot reuse TIM or thermal grease. If it is
damaged, or if the heatsink has already been installed once, the existing TIM must be cleaned
off and reapplied. To do this, use a soft towel or cloth to remove the previous thermal grease
from the heatsink and the top of the processor. Apply new thermal grease to the top of the
processor heat spreader (metal cap). Use the smallest amount that you can spread over the top
of the chip, usually an amount the size of a “BB” is sufficient. Use your finger (wearing a rubber
glove to prevent contamination) or a hard plastic card (such as a credit card) to spread the thermal
grease in the thinnest possible layer covering the entire surface of the heat spreader (metal
cap).
4. Install the heatsink. If the heatsink uses push pins (see Figure 19.10), make sure the pins are
rotated in the proper position. The tops should be turned in the opposite direction of the
arrows on top. Set the heatsink on the processor such that the four pins engage in the holes surrounding
the socket. Then push down each of the four pins until they click or latch into place.
This can take more force than you might think is prudent, so be sure to visually inspect the
installation to ensure that all four pins have fully engaged and are locked. Some heatsinks use
one or more retainer clips (see Figure 19.11). With this type you must be careful when attaching
the clip to the socket; you don’t want it to scrape against the motherboard, which can damage
circuit traces or components. You also need to keep the heatsink steady on the chip while
attaching the clips, so do not move, tilt, or slide the heatsink while you attach it.