© 2015 desco industries inc. staticcontrol.com esd control experts hbm vs. cdm vs. cbe what is the...
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© 2015 Desco Industries Inc. StaticControl.com
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