Types of ESD Damage
Static damage to components can take the form of upset failures or catastrophic failures.
Upset failures - result in gate leakage
Catastrophic failures - occur in two forms, Direct and Latent
Direct catastrophic failures occur when a component is damaged to the point where it is DEAD NOW and it will never again function. This is the easiest type of ESD damage to find since it usually can be detected during testing.
Latent failures occur when ESD weakens or wounds the component to the point where it will still function properly during testing, but over time the wounded component will cause poor system performance and eventually complete system failure. Because latent failures occur after final inspection or in the hands of your customer, the cost for repair is very high. Not only is this type of damage hard to find, but it severely affects the reputation of your company's product.
An upset failure occurs when an electrostatic discharge has caused a current flow that is not significant enough to cause total failure, but in use may intermittently result in gate leakage causing loss of software or incorrect storage of information.
Upset or latent failures may pass your company's quality control testing program. In other words, static damage may occur that cannot be felt, seen, or detected through normal testing procedures.