I think i am correct in saying that a [supernova](http://en.wikipedia.org/wiki/Supernova) ($Type$ $II$) is caused by the collapse of the core of a giant star. This contraction of the core is stopped by the [Pauli exclusion principle](http://en.wikipedia.org/wiki/Pauli_exclusion_principle) and the core becomes rigid. The outer layers now rebound of the rigid core and are thrown into space as a supernovae. But presumably this leaves behind a neutron star and not a black hole. For a black hole to form the [Pauli exclusion principle](http://en.wikipedia.org/wiki/Pauli_exclusion_principle) would not be strong enough to stop the collapse? If so what causes the outer layers to rebound, as there is no ridged object for them to rebound off? What I am basically asking is when a black hole forms what mechanism causes the supernovae?