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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