Silver colored caps on IC's

Different CPUs have different heat spreaders. CPUs today, if a heat spreader is used, is almost always Kovar

Here is one that is gold plate:



Here are Pentium Pros which is gold plate over a tungsten/copper based heat spreader:





Here is an example of heat spreaders used in the manufacture of different components, some for CPUs, some for memory, some for ICs. None have any gold associated with them, and are made of different materials according to their requirements:



And finally, the silver cap on CPUs we are all so familiar with, this one is probably Pyrolytic Graphite Composite



Here are heat spreaders on the bottom of CPUs that are made of Kovar:



Ans Kovar heat spreader blanks



Scott