Paper or books underneath the computer- are they in danger of being a fire hazard?
The lowest temperature at which spontaneous ignition of paper occurs (meaning that it lights up without a source flame) is at Farenheit 451 degrees.
The melting temperature of the type of plastic materials most likely to be found in computers is much lower – in the range of 300 to 400 degrees Farenheit (it varies between grade of plastic, but most computers are made from a narrow range of plastics).
The melting temperature of the solder that is holding together most of the electronic computer components is even lower – most conventional solders re-flow at around 360 degrees Farenheit. And many electronic components require a re-flow temperature less than 260 degrees Farenheit.
So, to answer your question, the entire computer would melt to a blob and the motherboard would come apart well before a piece of paper would catch fire spontaneously. But there’s no danger – most computers operate at only 175 degrees or so, without considering cooling systems.