Teledyne T100 Manuale Utente

 

 

If one of the surfaces is a poor conductor or even a good conductor that is not grounded, 
the resulting positive or negative charge cannot bleed off and becomes trapped in place, 
or static.  The most common example of triboelectric charging happens when someone 
wearing leather or rubber soled shoes walks across a nylon carpet or linoleum tiled floor.  
With each step, electrons change places and the resulting electro-static charge builds up, 
quickly reaching significant levels.  Pushing an epoxy printed circuit board across a 
workbench, using a plastic handled screwdriver or even the constant jostling of 
Styrofoam

TM

 pellets during shipment can also build hefty static charges 

Walking across nylon carpet 

1,500V 

35,000V 

Walking across vinyl tile 

250V 

12,000V 

Worker at bench 

100V 

6,000V 

Poly bag picked up from bench 

1,200V 

20,000V 

Moving around in a chair padded with urethane foam 

1,500V 

18,000V 

Damage to components occurs when these static charges come into contact with an 
electronic device.  Current flows as the charge moves along the conductive circuitry of 
the device and the typically very high voltage levels of the charge overheat the delicate 
traces of the integrated circuits, melting them or even vaporizing parts of them.  When 
examined by microscope the damage caused by electro-static discharge looks a lot like 
tiny bomb craters littered across the landscape of the component’s circuitry. 
A quick comparison of the values in Table 14-1 with the those shown in the Table 14-2, 
listing device susceptibility levels, shows why Semiconductor Reliability News estimates 
that approximately 60% of device failures are the result of damage due to electro-static 
discharge. 

06807C DCN6650