Characterizing automated handling equipment using discharge current measurements

Characterizing ESD performances of automated handling equipment (AHE) has always been confusing, subjective, sometimes just plain arbitrary, and most of the time wrong. ESD sensitivity of devices is classified by an amplitude and type of discharge mode. For example, a device may be susceptible to a discharge of 200 volts human body model (HBM), charged device model (CDM), or machine model (MM). Each of the models has unique circuitry of capacitance and resistance to provide a specific current and rise time of the discharge at a specific voltage. This is fairly repeatable in most cases. On the other hand, attempts to classify AHEs based on voltage measured at certain points in the product path can be and most often is misleading. This paper deals with the experimental methods of measuring the discharge currents and the results of processing devices through automatic processes and placing them on a special board to promote a discharge.