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Published byAustin Lloyd Modified over 9 years ago
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© 2015 Desco Industries Inc. StaticControl.com ESD Control Experts HBM vs. CDM vs. CBE What is the difference?
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Agenda ESD Basics Different ESD Models Applications
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ESD Basics
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Fig 1: ESD damage/short between Emitter/Collector regions on a device. ESD
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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
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Formula Q=V*C Q – Charge/Potential V – Voltage C – Capacitance
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Mechanism of ESD generation Product 1 vs. Product 2 C 1 * V =Q 1 = Q 2 = V * C 2 C 1 * V= Q 1 ≠ Q 2 = V * C 2 No ESD Event generated ESD Event generated
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ESD Models
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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
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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
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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
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Example
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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
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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
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Example
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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
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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
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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
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Applications
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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
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