ESD protection

Many semiconductors are sensitive to electrostatic discharge (ESD), commonly known as static electricity. Static electricity charges can occur when different materials are rubbed against each other. The voltage is discharged when, for example, someone touches the charged material. The voltage generated and discharged can be several thousand volts.

Though the amount of energy i small, the high voltages are harmful to many kinds of electronics. Components damaged by ESD often don't break completely, but are only damaged. They may still function, but with altered properties and a shortened lifespan. This may be the cause of "unexplained faults" in electronic equipment. Finding such unclear defects in an assembled product is very time-consuming – so it's best to protect sensitive components from the onset. 

Some semiconductors are more sensitive than others. Mosfets, for instance, have highly sensitive gates – and Mosfet transistors are located in all microprocessors, and much of other modern electronics, too. Miniaturization also makes electronics more sensitive, simply because the semiconductor materials have less mass and cannot withstand higher voltages. Even some passive components such as resistors can be damaged by ESD discharge, but this is mainly relevant for the smallest of surface-mount resistors.

In addition to components, some test equipment may also be sensitive to ESD. This is especially true for equipment with higher bandwidth, e.g. spectrum analyzers or signal generators with 50 Ohm input or output impedance. The fact that it is the most expensive equipment that is most sensitive makes ESD protection particularly important.

There are many different products to protect electronics from ESD. The protection is required at all stages, from storage and transport to assembly and repair. Storage should be in boxes made of materials that cannot be charged, or materials that are dissipative. Mechanical protection for transport should take place in bags that are shielded so that discharges from outside the bag cannot affect the contents inside it, and using e.g. electrically conductive foam. 

In the workplace, a dissipative surface is needed (usually a mat, but materials such as steel are used), as well as a conductive strap around the ankle or wrist. Both of these must be grounded – this allows the work surface and the person to hold the same potential as ground, and no discharges can occur when the person touches the work surface.