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ESD Control Experts
HBM vs. CDM vs. CBE
What is the difference?
© 2015 Desco Industries Inc.
StaticControl.com
Agenda
• ESD Basics
• Different ESD Models
• Applications
ESD Basics
ESD
Fig 1: ESD damage/short between
Emitter/Collector regions on a device.
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*C
Q – Charge/Potential
V – Voltage
C – Capacitance
Mechanism of ESD generation
Product 1 vs. Product 2
C1 * V =Q1 = Q2= V * C2
No ESD Event generated
C1 * V= Q1 ≠ Q2= V * C2
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
CBE – What is it?
• PCB potential depended – rapid discharge
• Higher Peak Current than CDM Event
• Influences component in the path of the
discharge
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