Why is the CPU rarely bad?

From about 2000 years to touch the computer to now seems to have not heard of the CPU is broken. Is the CPU really very rarely bad? is the quality control strict or this kind of product structure is not easy to damage?

The CPU is still going to be bad.

Although the protection of layers of packaging plus the production of good control of the factory, the CPU is difficult because of external causes of the physical damage to the chip, but broken needles, overclocking or lightning caused by excessive voltage burning, short circuit, and so on, and so the reason will make the CPU becomes unusable.

That has been normal use, the CPU is not a permanent work of the components it? In fact, it will also be used in the loss, the normal use of its own life. The main reason for the normal damage to the CPU is the electronic migration. Modern CPUs use the principle of etching doping to produce a nanoscale gate circuit, in which the momentum of the electrons passes through the atoms in the circuit, leaving a tiny portion of them adrift from the constraints of other atoms. Although this effect is very small, but over time will lead to circuit distortion, short-circuit, leakage and interference phenomena. At this time the CPU will appear abnormal operation, its function is affected, and then is reimbursement. The high temperature will make the atomic heat movement intensifies, increases by the electron to cheat the probability, at room temperature, every 20 degrees, the electron migration intensity increases one times. Materials also affect electronic migration, and IBM uses copper materials that are more resistant to migration than Intel's aluminum material. Pressure overclocking can sometimes control the temperature, but high voltages can also increase the intensity of the electron transfer.

However, due to the process and performance of the CPU constantly improve, often a CPU in the end of the past has been replaced by the replacement. I have also seen the end-of-life of CPUs that have been working 7x24 for a long time in harsh, high-temperature environments. Old CPU due to the process is relatively backward, the circuit is more robust, the phenomenon of electronic migration is not enough in so many years to its fatal impact, so the bad is also less. The new CPUs tend to be more atomic in process, but the electronic migration will still be considered by the manufacturer, so the normal use does not care too much about these aspects.