Читать книгу The ESD Control Program Handbook - Jeremy M. Smallwood - Страница 70

Many products, modules, or subassemblies have an insulating plastic housing containing a circuit board. The connections to this may be brought out to terminations at flying leads or a connector.

The housing can become highly charged, e.g. by rubbing or removal from packaging, inducing a high voltage on the PCB within the housing (Figure 2.18). If a connection is made to the module in this state, a discharge can occur at the termination at which contact is made.

Figure 2.17 ESD waveform from a printed circuit board (above) charged to 1 kV (below) field induced charged by insulator 40 mm away.

Figure 2.18 ESD waveform from a charged automotive module taken out of a polythene bag. Charge transferred 35 nC.

Figure 2.19 Voltage on an automotive cable core as polythene packaging is removed.