ESD Systems - Questions And Answers

Recently one of customer feedback to us that one of the particular IC (ICH2) on the board fail due to EOS. They says that this failure is cause by handling. This boards after performing the ICT and FT will be going into Burn-in testing. The customer suspect that this failure could be duringloading and unloading in the Burn-in. I have measured the body charge generation on the person who works on the Burn-in. The average body charge generation with heel strap is 40 volts, with wrist strap is 5 volts andwithout any grounding device is 400 volts. All personnel are grounded either with wrist strap or heel strap. The production floor is covered with dissipative mat, the reading is 10E8 - 10E9 ohms/square. I use the Novx 5000 series voltage detector to measure the body voltage. Attached is the scan copy of failure after FA. Appreciate if you could kindly advise what action should be taken during the customer audit. - Anonymous

An ESD (electrostatic discharge) is a type of EOS (electrical overstress). From the images you sent, it looks like these devices were damaged via the CDM (charge device model). The devices themselves can become charged without any human intervention and discharge (ESD event) when in contact with a good conductor (metal tray, etc.) and result in the Failures you showed in your images. To minimize this problem, keep the devices from coming into contact with each other by storing them in ESD antistatic packaging, and do not place or let these devices contact metal or other very good conductors or employ an ionizer at places where this may happen if there is no other way to control this environment.

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