To investigate any ESD problem, we will need to have a systematic approach of analyzing the ESD problem.

We will have to start from the very beginning of a process chain of where the ESD sensitive device is first handled.
In a typical Printed Circuit Board Assembly manufacturing environment, a process chain will look something like this.

Incoming -> Store -> Kitting -> Screening ->Pick and Place -> Reflow -> Cleaning -> Backend soldering -> Testing -> Inspection -> Packing

Investigation shall start with how the ESD sensitive device is being handled in each process in the process chain.
Auditing alone to check for ESD compliance is insufficient to make conclusion that the process is not the source of ESD problem.
A fact finding approach is more appropriate to investigate the ESD problem.

Before start collecting data, we need to understand the ESD failure/damage models:
• ESD HBM damage model
• ESD MM damage model
• ESD CDM damage model

For each of ESD damage model, we will know what type of data to be collected.
• HBM damage model : we will have to measure human body voltage on personnel
• MM damage model : we will have to measure the grounding resistance of conductive elements of a manufacturing/test equipment that made contact with ESD sensitive device
• CDM damage model ( Field Induced model ) : we will have to check the electrostatic field voltage of the area where ESD sensitive device might pass through
• CDM damage model (Charged Package model): we will have to check the voltage on the conductive elements of the ESD sensitive device/assembly

After knowing the type of data to be collected, now we will have to prepare the ESD analysis tools. Examples of ESD Analysis tools are as follows:

• Prostat Auto Analysis System (PGA 710), analysis tool will be very handy to measure the human body voltage
• A normal digital multimeter or better still a true ground meter such as Ground Pro will be handy to measure the equipment grounding resistance
• A static field meter will be able to check for electrostatic field voltage
• A high impedance Contact Voltmeter such as Prostat CVM-780 Contact Voltmeter will be handy to measure voltage on the conductive element in ESD device/assembly/equipment

Based on ESD Technology Roadmap issued in year 2005, any ESD process in the manufacturing lines shall be controlled as follows through year 2010.

• Human body voltage on personnel shall be less than 100Volts
• Conductive elements of equipment shall be grounded ( or less than 10Volts)
• Voltage on ESD sensitive devices shall be less than 50 Volts

Measure the voltage on personnel, conductive elements of equipments and ESD sensitive devices at each process in the process chain will tell us whether the ESD sensitive device’s withstand voltage has been exceeded . If the ESD withstand voltage of the ESDS device is exceeded, that will point to the root cause of the ESD problem.

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