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ESD Control Experts

HBM vs. CDM vs. CBEWhat is the difference?

Agenda

• ESD Basics

• Different ESD Models

• Applications

ESD Basics

Fig 1: ESD damage/short between Emitter/Collector regions on a device.

ESD

What is Electrostatic Discharge (ESD)?

• ESD is a rapid, spontaneous transfer of electrostatic charge induced by a high electrostatic field through a spark between two bodies at different electrostatic potentials as they approach or are separated from one another.

• There are three different ESD models identified by the standards presently:

− Charge Device Model (CDM)− Machine Model (MM)− Human Body Model (HBM).

Fig 2: ESD damage to a bipolar transistor

Formula

Q=V*CQ – Charge/PotentialV – Voltage C – Capacitance

Mechanism of ESD generation

Product 1 vs. Product 2

C1 * V =Q1 = Q2= V * C2

C1 * V= Q1 ≠ Q2= V * C2

No ESD Event generated

ESD Event generated

ESD Models

Real-life Situation

• Different discharges reflect different situations

• Real-life discharges may differ from specified ESD models

• Models considered for component qualification test

• Important to analyze your process and define most relevant model

HBM – Human Body Model

• Best understood model to date

• Dominant discharge on manual operation electronic assembly

• Operation handling devices by hand is a must

• Poorly grounded charged operator touching a component is source of HBM Event

• Processes automation eliminates HBM

• Better attention to grounding eliminate HBM

• Better in-component protection against slow rise (2-10ns) events eliminates HBM

What is ESD?

• Charged Human Body

• Discharge from a fingertip to a grounded component

• 100 pF capacitor discharged through a switching component and 1,500 ohm series resistor into the device under test

By ESDA

Example

CDM – Charge Device Model

• Most relevant in today’s electronic production

• Rapidly discharge of energy from a charged device to ground

• Dominant discharge on automated operation electronic assembly

• Voltage induction to component and tribocharging is a must

• Faster processes automation - problematic

• Very fast discharge – high energy, trace overheating – craters or blown-up traces

• RF high frequency components have little protection

CDM – What is it?

• Device depended

• CDM event has less than 2.0 nanoseconds duration

• Rise time of CDM event could be as short as 65 picoseconds

By ESDA

Example

CBE – Charge Board Event

• Rapidly discharge of energy from a charged PCB to component

• High capacitance board (>125pF) holds much more voltage

• Voltage induction to the board and component becomes important

• Very fast discharge – high energy/high current

• CBE an extension of CDM

• Components on the board go through EOS

• PCB potential depended – rapid discharge

• Higher Peak Current than CDM Event

• Influences component in the path of the discharge

CBE – What is it?

By Analog Devices

Detecting ESD Events in Your Production

• Identify component sensitivity and measure ESD events

• Instrumentation insures compliance

• Products used:− SCS EM Aware TNG ESD Event Monitor

Starter Kit− SCS EM Eye Meter− SCS ESD Pro Event Indicator

Applications

Finding the Root Causes of ESD

• Identify the Application Where ESD Events are Being Created

• For Example…− SMT Line− Soldering− Printer− Repair− Functional Test (Manual or Automatic Testing)− Manual Applications

Must Know Where to Look…SCS Expertise and Technology Can Help