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April 2001

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From:
Christophe CROCOMBETTE <[log in to unmask]>
Date:
Wed, 11 Apr 2001 17:43:34 +0200
Reply-To:
"TechNet E-Mail Forum." <[log in to unmask]>, Christophe CROCOMBETTE <[log in to unmask]>
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Here, in Electricite De France, our field return shows that ESD/EOS represent
around 30% of our root causes of failure.
It is the feature that one can find in much papers (ex : Component Quality
and Reliability, Intel 1992). Discussions with other users lead to the same
conclusions. The point is to know if the cause is an ESD or an EOS. We have
no idea for our equipment. However, it seems to be possible to identify the
signature of both causes even if their are very similar (???).

You'll find some interesting datas in "ESD in Silicon integrated circuits"
(A. Amerasekera, Ed. Wiley, 1995).

some other field data from other technetters...?

Chris






[log in to unmask] on 11/04/2001 16:39:00
Pour :  [log in to unmask]@hub
cc :     (ccc : Christophe CROCOMBETTE/ERMEL/DER/EDFGDF/FR)
Objet : Re: [TN] ESD consequences

As with many things the consequences of creating ESD damage depends on what you do and who you do it to. [From our ESD Awareness Training .]

Problem #1 with ESD. Our day-to-day activities produce tremendous charges.

          Electrostatic voltage (v)

      Static generation process
       at 10 to 20% RH
       at 65 to 95% RH


      Walking on carpet
       35,000
       1,500

      Walking on vinyl flooring
       12,000
       250

      Worker sitting at a work bench
       6,000
       700

      Handling a vinyl envelope used for work instructions
       7,000
       600

      Picking-up a sandwich plastic bag from a bench
       20,000
       1,200

      Sitting at polyurethane cushioned bench
       18,000
       1,500

. And the level of charge generated varies with the relative humidity (RH) level. This variability caused by humidity helps explain why we seem to get more "carpet shocks" in the winter, when the air is dry, than in the summer, when the air is moist.

This is because most common insulating materials such as wood, fabric, paper, or masonry contain a certain amount of moisture, which is dependent on the relative humidity of the air. To some extent, the moisture content, in turn, affects the conductivity of these materials and their ability to hold static charges.

      Relative humidity
       Conductivity


      Higher >50%
       More conductive

      Lower <30%
       More insulating

Logically, it would follow that high humidity would be an effective means of controlling static electricity. High humidity:

. Still allows generation of unacceptable charges, even though not a large as low humidity.

. Contributes to other problems including oxidation and soldering difficulties.

. Is uncomfortable and expensive to generate.

Problem #2 with ESD. We can not easily see, smell or feel ESD.

      Perception
       Body's electrostatic voltage (volts)


      Not felt when touched at the back of the finger
       Below 500

      Slight sensation when touched at back of finger
       Above 1,000

      Not felt on index finger when touching
       Below 2,500

      Slight sensation on index finger when touching
       Below 3,000

      Audible discharge
       Above 5,000

      Visible spark
       Above 10,000



Problem #3 with ESD. Electronic components are very sensitive. Components can be easily damaged by voltages that we can not sense. The breakdown voltage is the voltage level that causes damage to the component.

      Device type
     Breakdown voltage (v)
       Device type
     Breakdown voltage (v)


      VMOS
     30 to 1,800
       Bipolar transistor
     380 to 7,000

      GaAsFET
     100 to 300
       Junction FET
     140 to 10,000

      EPROM
     100
       OP AMP
     190 to 2,500

      CMOS RAM
     250 to 2,000
       ECL
     500 to 1,500

      Schottky diode
     300 to 2,500
       SCR
     680 to 1,000

      Schottky TTL
     100 to 2,500
       Film resistor
     300 to 3,000

Note that at 1/4 of the breakdown voltage shown, these parts can still be damaged even though they may pass the manufacturers' specifications when tested, but the damage may cause them to fail earlier than normal in the field.

Problem #4 with ESD. Electrostatic discharge events are often imperceptible, causing:

Delayed Failure. Electrostatic discharge may damage a device or change its characteristics without causing immediate failure. The device may pass inspection, move into the market, then fail during its initial period of use.

Difficulty In Identifying Discharge Site. Humans generally cannot perceive electrostatic discharges of under 3000V, while semiconductor devices can sustain damage from electrostatic voltages as low as 100V. It is often very difficult to locate the process at which electrostatic problems are occurring.

Result of these problems: ESD causes billions of dollars in damage each year.



  ----- Original Message -----
  From: Bissonnette, Jean-Francois
  To: [log in to unmask]
  Sent: Wednesday, April 11, 2001 5:10 AM
  Subject: [TN] ESD consequences


  Hello Technetters,

  I'm looking for statistics on ESD consequences on electronic equipment.  Such
  as % of field failures due to ESD and that kind of stuff.  Anyone as a good source
  to suggest??

  Thanks!

  JF


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