Читать книгу The ESD Control Program Handbook - Jeremy M. Smallwood - Страница 68

When a component touches a highly conductive object (e.g. metal) at a different voltage, a very short duration high discharge current ESD event occurs. The voltage difference may occur if the component is charged or the object is charged, or both. The same type of discharge will occur if either the component or the object is grounded.

The voltage on the device may arise from tribocharging or induced as a result of nearby electrostatic field sources. Often field‐induced voltages can give the highest voltages arising on the device. Some examples of field‐induced charged device ESD obtained in a laboratory experiment are given in Figure 2.16. In this experiment, the devices were slid down a charged PVC tube onto a 1.7 Ω target plate connected to a fast digital storage oscilloscope (500 MHz bandwidth, 2 Gs s⁻¹ sample rate).

The fast high current peak typical of charged device ESD can be seen. The indicated peak current and rise and fall times of the waveform peaks are probably under‐represented, as these waveforms are typically faster than the measurement system used here.

Figure 2.16 ESD waveforms from charged integrated circuits: (above) 32‐pin plastic‐leaded chip carrier and (below) 24‐pin dual‐inline package.