ESD CORNER
ESD Systems’ ESD Technical Newsletter
Issue 7, July 1999: Volume 2
Reference: http://www.esdsystems.com/newsletters/v2issue7.htm
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Systems, 19 Brigham Street, # 9, Marlboro, MA 01752-3170
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IN
THIS ISSUE:
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·
HOT TIP of the
MONTH (Ohmmeters)
·
21st
Annual EOS/ESD Symposium '99 (September 26-30)
·
ESD Q&A
CORNER (ESD Training)
·
PRODUCT
UPDATES (Mini Monitor)
·
Dr. ZAP (ESD Quiz – Test
Your Knowledge)
HOT
TIP of the MONTH (Ohmmeters)
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The basic ohmmeter typically measures resistance from zero ohms to just
over one megohm, and usually at a low voltage such as 1.5 volts. Also, the basic ohmmeter uses two needle
point probes, so the contact area is very small, usually only good for contact
with highly conductive materials, such as wire leads on discrete components or
metal traces on circuit boards. For
ESD, we use a megohmeter, which has some key differences to a standard
ohmmeter. The megohmeter has the
ability to make measurements from about one thousand ohms to one teraohms and
driving a potential difference between the probes to 100 volts, not 1.5
volts. Also, the probes used on a
megohmeter are much larger, 2.5 inches in diameter and with a constant 5 pound
force on the contact surface for consistent readings. Applications for basic ohmmeters would be to check the ground
integrity, according to ANSI/EOS/ESD-S6.1-1991 to less than 1 ohm. Applications for a megohmeter would be to
check planar surfaces for the correct dissipative range, such as floors, bench
mats, packaging, etc. Refer to
ANSI/ESD-S7.1 (floors), ANSI/EOS/ESD-S11.11 (planar materials), ESD DS20.20
(general ESD).
1999 EOS/ESD Symposium
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The 21st
annual EOS/ESD Symposium is scheduled for the Wyndham Palace Resort in Orlando,
FL, September 26-30, 1999.
The Symposium emphasizes the effects of electrical overstress (EOS),
electrostatic discharge (ESD) and electrostatics on electronic and
non-electronic devices, assemblies, systems, and processes.
Technical papers and authors corners will cover the latest research and
technology. The technical program is supplemented by workshops and ESD training
videos. The Symposium opens with two days of ESD seminars and tutorials.
Attendees will also have the opportunity to visit the exhibits of more than 100
companies who provide EOS and ESD control products and services.
Hundreds of attendees from throughout the world are expected to attend the
annual event. The Symposium is sponsored by the ESD Association in cooperation
with the IEEE. It is technically co-sponsored by the Electron Devices Society.
For more information on the Symposium, contact the 1999 EOS/ESD Symposium, c/o
the ESD Association, 7900 Turin Rd., Building 3, Suite 2, Rome, NY 13440.
Phone: 315-339-6937; Fax: 315-339-6793; e-mail: eosesd@aol.com Web Site: http://www.eosesd.org
ESD Q&A CORNER
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The following questions and answers were selected from our FAQ WEB Page: http://www.esdsystems.com/default.asp?PageNo=QANDAINDEX concerning Questions about ESD Sensitive
Components and Standards.
Q1: A field meter
will detect the presence of an electric field or a charge build up. A voltmeter
will detect the potential difference between two points possibly relating to
charge build up.
A1:
We
have an in-house training program that can last up to two days, depending on
the level of training you want. Also, the ESD Association sponsors the EOS/ESD
Symposium each year that has an abundance of ESD Training tutorials, technical
papers, and workshops to help educate people. In addition, there are several
regional tutorials in the States that occur in early spring. Check out the ESDA
website for more details: http://www.eosesd.org/
++++++++++++++++++++++++++++++++++++++++++
Q2: About the application of wrist strap and bench mat, it is a
basic requirement to ground. How can we measure whether the ground point itself
is properly grounded to the ground? Where
can I find an Internet training center that has an ESD course? The best one is
that they can issue a certification proved by ESD Association. - Anonymous,
Sweden
A2: You can check the integrity of the
grounding system with a basic ohmmeter. As long as the grounding cord doesn’t
have a 1 megohm resistor in series, then the maximum resistance in the cord to
ground circuit should be less than 1 ohm. Check this resistance from the common
point ground to the physical power, earth, or dedicated ground. It should read
less than 1 ohm.
As far as Internet courses, I believe there are some companies like CBTC and
maybe IMC that either have one or are working on an Internet ESD control
course, but they are not ESDA approved.
ESD Systems will be coming out with an Internet based training course that is
being written by a NARTE ESD Control Engineer and ESDA active member. This should be available in the late Summer
of 1999.
++++++++++++++++++++++++++++++++++++++++++
Q3: Thanks for your help, I had a few
questions in regards to some of the answers that you gave me.
All employees handling ESD sensitive devices in the ESD safe work area need to
be properly trained, so they know how/why to wear their wrist strap, how to test
it, when to wear it, how to handle ESD sensitive devices including the opening
of ESD packages.
Is there training material available that explains correct procedures for
opening ESD packages ?
Control the necessary insulators at your ESD Safe work area with ionization or
topical ESD treatments. Could you explain "necessary insulators" ?
Remove unnecessary insulators from your ESD safe work area. Could you explain
"unnecessary insulators"? - Anonymous, Atlanta, GA
A3:
Training in general:
There is a good VHS tape series which comes with a handbook
for group training, part # 36074. This same content is available on CD-ROM for
individual training using a PC, part # 36061. A database keeps track of all
employees progress, where they need help, and gives a recorded final exam.
There are also
that are available to help your training program too.
Training for packaging only:
Insulators:
Necessary insulators are those that are necessary to
complete the job at the bench, such as soldering iron handle, screw driver
handle, Teflon O-rings, etc.
Unnecessary insulators are all other insulators not necessary
to perform the given work at the ESD safe work station. Some examples are
styrofoam coffee cups, radios, notebooks, phones, plastic bins, etc.
PRODUCT UPDATES (NEW!)
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Workstation
Continuous Mini
Monitor - ESD Systems Model 41122
real-time monitoring of an ESD workstation and wrist strap
·
is a compact unit
·
real-time monitoring of an
ESD workstation including wrist strap, mat, and cords.
·
Red and green LEDs indicate
grounding status
·
Can be used with any brand of
industry standard single-wire wrist straps
·
True 100% continuous
monitoring, no pulsed current
·
cannot be fooled
·
There are no false alarms
·
no pulsed current that can
cause skin irritation
For
additional information contact ESD Systems at (508) 485-7390, fax (800)
805-5665 or visit our website: http//www.esdsystems.com
Dr. ZAP
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Topic: ESD Quiz – Test Your Knowledge
1)
Which is the best definition of static electricity:
a) The electrons
on the outer shell of an atom.
b) An electrical
charge at rest on the surface of an object.
c) The discharge
of electrons to earth.
2) What is one
way that static electricity is produced?
a) Static electricity
is produced any time two objects separate.
b) Static charge
is generated when lightning strikes.
c) Static charge
is generated only in extremely dry environments.
3) Under which
conditions is static electricity generated?
a) During humid conditions,
such as a thunderstorm.
b) In a hot, dry
climate, such as a desert.
c) In any
environment, under any weather conditions.
4) Which is the
best definition of electrostatic discharge?
a) The sudden
movement of a static charge from one object to another.
b) An electrical
charge at rest on the surface of an object
c) The movement
of static charge from one conductor to another that can be seen or felt.
5) A worker sets
a printed circuit board on top of a plastic notebook. Is an electrostatic discharge likely between the board and the notebook?
a) No, there will
be no electrostatic discharge.
b) Yes, there
will be an electrostatic discharge.
6) If a field
service representative must replace a circuit board in a computer, which type
of failure has happened?
a) Catastrophic
b) Upset
7) On a dry day,
a computer circuit board failed after its ungrounded operator discharges to the
board several times. Which type of
failure most likely occurred?
a) Immediate
b) Latent
c) Cumulative
8) A customer
calls for service on a piece of equipment a field service representative
repaired only a few days ago. This
computer worked for a while, then the replacement circuit board failed. Which type of failure is the most likely cause?
a) Immediate
b) Latent
c) Cumulative
9) The managers
of a department that will manufacture a new electronic component have decided
not to start and ESD Control program right away. Which choices represent the possible results of this decision?
a) Dissatisfied
customers.
b) A higher
reject rate of products.
c) Increased
warranty service costs.
d) Reduced costs
due to saving on ESD control materials.
10) Which of the
methods listed below are used to protect components from electrostatic discharge?
a) Remove all
charge-generating items from the work area.
b) Remove
unneeded charge-generating items from the work area and control the rest.
c) Put components
in ESD-protective packaging.
d) Make sure
people, static-control work surfaces, and equipment are grounded.
11) Which of the
following are charge-generating objects that should be kept away from sensitive
components?
a) Styrofoam coffee
cup
b) Radio
c) Plastic flower
pot
12) Which is the
farthest distance you should work from a bench-top ionizer and maintain the
effects of the ionizer?
a) Seven feet (2
meters)
b) Five feet (1 1/2
meters)
c) Three feet (1
meter)
13) Your job
requires that you relax the static cling that holds dust to the surface of a wafer. Which ionizer is most effective for this
use?
a) Bench-top
ionizer
b) Room ionizer
c) Compressed gas
ion gun
14) Which is the
best description of the effectiveness of topical anti-stats? Topical anti-stats:
a) Wear off and
should be reapplied once a week
b) Wear off or
are effective in extremely low humidity and should be tested.
c) Are now so
advanced technically they need only be applied once.
15) Match each
type of ground with its description.
____ A
junction where static dissipative a)
Hard ground
work
surfaces, personnel grounds, b)
Resistive (soft) ground
and
equipment being tested can all c)
Common Point ground
be
connected to ground.
____ A
direct connection to ground
that
has very little resistance.
____ A
current limiting personnel ground.
16) What is the
most effective way of keeping a person grounded?
a) A wrist strap.
b) Touching a
grounded chassis
c) Wearing all
cotton clothing.
d) Touching a
dissipative mat.
17) Which of the
following statements about wearing a wrist strap is incorrect?
a) Make sure the
wrist strap fits comfortably snug to your wrist.
b) Connect the
wrist strap cord to the ESD Common point ground or hard ground.
c) If you are
wearing static dissipative garments, make sure the wrist strap fits over the elastic
cuff.
d) If you are
using a dissipative mat, snap the wrist strap to the common point or hard ground
terminal
18) Which of these
statements about wrist strap safety are correct?
a) Do not use a
disposable wrist strap around exposed electrical hazards.
b) Do not use a
disposable wrist strap around equipment that is still connected to its power.
c) Do not use a
wrist strap where the ground cord could become tangled in machinery
19) An employee is
testing her wrist strap. When she
pushes the tester button, the green (SAFE) indicator lights. What should she do next?
a) Use a
different wrist strap tester.
b) Remove this strap
and start over with a new one.
c) Stop the
test. The green light means the wrist strap
passed.
d) Apply approved
moisturizer and try again
20) Another
employee is now testing his wrist strap.
When he presses the tester button, the red (LOW RESISTANCE FAIL)
indicator lights. What should he do
next?
a) Stop the
test. This light means the wrist strap
passed the test.
b) Remove this
strap and start over with a new one.
c) Tighten the
strap until it is snug and try again.
d) Apply approved
moisturizer and try again.
21) An employee
puts on his wrist strap snugly. When he
presses the tester button, the yellow (HIGH RESISTANCE FAIL) indicator lights. What should he do next?
a) Stop the
test. This light means the wrist strap
passed the test.
b) Remove this
strap and star over with a new one.
c) Apply approved
moisturizer and try again.
ANSWERS: (1-21)
b-a-c-a-a-a-c-b-abc-bcd-abc-c-c-b-cab-a-c-ac-c-b-c
<<<=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=>>>
This is a free monthly newsletter, which
specializes on issues in static control in the
semiconductor/electronics workplace.
Need your own copy? Want to subscribe to this Newsletter? All you or your
colleague(s) need to do is simply fill out the subscription form at http://www.esdsystems.com/?PageNo=SENDEMAIL
This Newsletter is never sent unsolicited. To
unsubscribe from this mailing, send an e-mail to ESD_Newletters@esdsystems.com and put " UNSUBSCRIBE
ESD_Newsletters" in the subject.
Let us know what you think. Tell us what you would like to see in future
issues. Want to contribute articles or other related information to our
Newsletter? Send your comments to the editor@esdsystems.com
Copyright © Desco
Industries, Inc. 1999
END V2I7