EMIT - Questions And Answers

What are the requirements for an ESD Class 0 Lab? (Or, where could I obtain straight forward information on requirements?) - Anonymous

Typically, when people say class 0, they are referring to the Human Body Model (HBM). The Charge Device Model (CDM) is often overlooked and should also be considered when designing an ESD control program. The requirements are to keep the generation of voltages in the ESD protective work too less than the classification rating (in this case 150 volts CDM). A class 0 program requires a lot more discipline and proper design and use of ESD control products.

NOTE: There are 3 classifications based on 3 different ESD models which are detailed standards from the ESD Association: http://www.esda.org

(1) Human Body Model (HBM) [100 pF @ 1.5 kilohms], ESD STM5.1

(2) Charge Device Model (CDM) [4 pF/30 pF], ESD DS5.3.1

(3) Machine Model(MM) [200 pF @ 0 ohms], ESD STM5.2HBMThe most common model is the HBM. This model simulates when a discharge occurs between a human (hand/finger) to a conductor (metal rail). The equivalent capacitance is 100 picofarads (100 x 10^-12 Farads) and equivalent resistance is 1,500 ohms to simulate a human body. The typical rise time of the current pulse (ESD) through a shorting wire averages 6 nanoseconds (6x10^-9 s) and larger for a higher resistant load. The peak current through a 500 ohm resistor averages 463 mA for a 1,000 volt pre-charge voltage. HBM ESDS Component Classification Class Voltage Range (V)0 <2501A 250 to <5001B 500 to <10001C 1000 to <20002 2000 to <40003A 4000 to <80003B > or = 8000CDM The most neglected of models that can compromise your ESD control program. Here, it is the ESDS device itself that becomes charged (sliding out of a tube/bag/sorter/etc) and when contacting a grounded conductor (table top/hand/metal tool) will discharge to that conductor and may result in damaging ESD. Using a 4 pF or 30 pF verification module which can simulate from 2 to 30 Amps peak current for non-socked and up to 18 amps for socketed devices. CDM ESDS Component Classification Class Voltage Range (V)C1 <150C2 150 to <250C3 250 to <500C4 500 to <1000C5 1000 to <1500C6 1500 to <2000C7 > or = 2000MM Testing components to the Machine Model (MM). The tests replicate MM failures and tell you the MM ESD sensitivity levels for your Devices. The criteria (200 pF @ a nominal 0 ohms). 7.1.2. Machine Model Sensitivity:A source of damage for the MM is a rapid transfer of energy from a charged conductor to the conductive leads of the device. This ESD model is a 200 pF capacitor discharged through a 500 nH inductor directly into the device with no series resistor. Due to the lack of a series current limiting resistor, this model approximates a voltage source. In the real world this model represents a rapid discharge from items such as, charged board assembly, charged cables, or the conduction arm of an automatic tester. The discharge itself is a sinusoidal decaying waveform with a rise time of 5-8 nanoseconds and a period of approximately 80 nanoseconds.Control to this model would entail knowing the ESD sensitive devices MM ESD component classification and keeping all voltages below their MM Classes voltage range.MM ESDS Component Classification Class Voltage Range (V)M1 <100M2 100 to <200M3 200 to <400M4 > = 400

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