Re: ESD
Let's offer some numbers guys. An ESD can produce a pulse of 300A, voltage up to 20KV for a duration of few nanoseconds. This pulse can disrupt a electronic device or even destroy it. This kind of energy will always search the shortest path to the ground. Unfortunaytelly, for such high currents, even a strong wire, copper trace or metal case has enough inductance in order to stop the instanteniously surge of ESD potential to ground. Thus, in the point where ESD is discharged the potential is extremely high for a short period of time. This ammount of current will produce a EMP (electromagnetic pulse). If the PCB inside your device is poorly designed and contain loops, these loops will act as antennas for the EMP and inside that loop a electric voltage will be induced. If the loop is close and large enough, the induced pulse will destroy sensitive components. If you are lucky, only false triggering, circuits reset and volatile memory alteration will apear. If electronic components are directly in the path of the point where ESD is produced and ground (ex. you discharge directly into a IC pin), then start praying. There are few components which are protected against ESD discharge and will protect the circuits around(ex. some RS232 interfaces) but these will be effective only if they are properly connected to ground. Detailed informations about what is ESD, and how can be avoided effects of ESD are available in books related to subject like : PCB signal integrity, EMI/EMC/ESD design for compliance, etc. Search e-books upload/download.
/pisoiu