ESD system

An EDS tester is combined with an employee identifier and recording monitor so as to provide and audit trail of compliance with the fact of ESD testing and, if desired, a record of the ESD test results such as body resistance or charge. In one illustrative embodiment, a fingerprint identifier pad is used together with the ESD test to identify a unique biological characteristic of the worker being tested. In addition, the feature of providing physical contact with the workers body typically required for ESD testing may be combined with the fingerprint identifier pad thereby enabling the ESD test results to be correlated with a specific individual.

FIELD OF THE INVENTION 
This invention relates to electrostatic discharge systems and more 
particularly to such systems. 
BACKGROUND OF THE INVENTION 
In many high technology manufacturing operations, such as those involving 
the production of metal oxide silicon (MOS) transistor circuits, it is 
essential that plant personnel carefully observe rules requiring them to 
rid themselves of all static electric charges. In a typical manufacturing 
plant, employees may be required to test their ESD overshoes and log the 
results of the test every time they enter and leave their work area. 
Unfortunately, this task takes time, employees are sometimes lax in 
complying and some consider the task onerous and intrusive. 
A number of prior art patents have addressed the problem of discharging 
static electricity accumulation. For example, U.S. Pat. No. 5,632,255 
discloses a testing wristlet seat which uses an oscillator circuit to test 
a test lead which is grounded to discharge the static electricity produced 
in a manufacturing procedure. The oscillator generates a frequency to 
sound an alarm when the user breaks the ground connection. In U.S. Pat. 
No. 5,519,384 the worker wears a conductive wrist strap, circuitry 
monitors the electric field at the operator's wrist, sounds a warning and 
records when a problems occurs. In U.S. Pat. No. 5,247,420 a 
voltage-controlled oscillator senses the voltage on a discharge capacitor, 
generates high voltage pulses the effect the removal of charge by means of 
air ionization. In U.S. Pat. No. 4,859,992 the integrity of ground 
connections to conductive workbench, floor mats and wrist straps are 
monitored and alarms are generated when the resistance to ground 
approaches a set value. In U.S. Pat. No. 4,800,374 conductive wrist bands, 
touch pads and shoe plates are monitored for resistance and indicator 
lights provide a display of whether a safe or hazardous condition exists. 
U.S. Pat. No. 4,745,519 discloses details of a stretchable wrist strap 
having two or more sections of conductive material and circuitry for 
monitoring whether any of the sections of conductive material are in 
contact with the wearer or if the connection to ground is broken. 
While all of the foregoing devices operate satisfactorily, they are not 
quite adequate to assure, in a commercial environment, the ideal standard 
of conduct to which Paracelsus may have had in mind when he uttered the 
timeless words. "That we devote ourselves to God, is seen In living just 
as through no God there were". Simply stated, the prior art devices 
operate anonymously and therefore do not accommodate the requirements of 
management for assurance that each individual worker remain in compliance 
with ESD standards. In short, an identifiable audit trail of ESD 
compliance is required. 
SUMMARY OF THE INVENTION 
In accordance with the principles of the present invention an ESD tester is 
combined with an employee identifier and recording monitor. For example, 
in one illustrate embodiment, the prior art conductive touch pad is 
replaced by a fingerprint identifier pad to combine the features of 
physical contact with the workers body typically required for ESD testing 
with an identification of a unique biological characteristic of the worker 
being tested, thereby enabling the ESD test results to be correlated with 
a specific individual. The correlation method could comprise: capturing a 
personal identification image such as a fingerprint directly from the 
operator, substantially imultaneously capturing appropriate resistivity or 
electric field intensity ESD test data; comparing the image data with 
stored worker data; comparing the ESD test data with stored criteria and 
recording the results of the comparisons.

DETAILED DESCRIPTION 
Referring now to the single FIGURE of the drawing, a conventional ESD unit 
17 may include inputs from a worker's wrist strap 13 and pigtail lead 14 
and/or a conductive floor pad 15 and associated input lead 16. Over lead 
18, the ESD unit may record the results of its electrostatic charge 
measurement or body resistance tests in an associated computer or 
microprocessor 30. However, in accordance with the principles of out 
invention, at the same time that the ESD unit is acquiring its information 
from the worker, an associated fingerprint identification unit 20 is 
called into operation by the worker placing the finger 10 on its scanning 
platen, sometimes referred to in the art as a "biometric sensor". The 
biometric sensor overcomes the possibility that a wax image of fingerprint 
could be used in an attempt to fool the FIU. One well-known FIU device is 
manufactured and sold by Sony. The fingerprint identification unit 20 
sends data from the image of the scanned fingerprint 10a to microprocessor 
30 over lead 31. 
Prior to actual deployment and during the conventional enrollment process, 
the data storage and update unit 50 associated with the FIU will normally 
have been loaded with the fingerprints, such as fingerprint 10b, of each 
of its employees. When the worker now places his finger on the scanning 
platen, the scanned image of his fingerprint 10a acquired by 
microprocessor 30 is sent over lead 34 and compared in comparator 40 with 
all of the stored images accessed from data storage and update unit 50 via 
lead 54. In typically less than a second, a match may be made. When a 
match occurs between a scanned image 10a and a stored image 10b, the 
results of the comparison, as well as the data obtained by the ESD unit 17 
are entered into the data storage and update unit 50 thereby providing an 
"audit trail" of the ESD test which identifies the employee taking the 
test. 
Typically, the FIU only captures a sampling of the fingerprint and does not 
store an image of the entire fingerprint. This helps reduce the stored 
template size, increases speed, and protects the user by avoiding 
potential security problems. The image may be stored in the associated 
microprocessor or computer as a template or sent to a central processing 
unit (not shown). 
Further in accordance with our invention, the platen 11 of the FIU may be 
made of conductive, transparent plastic or, equally advantageously, 
conductive strips may be incorporated on or closely adjacent to the 
platen. The conductive platen or stripes are connected via lead 12 to an 
input of the ESD unit 17 so that electrical resistance of the finger or 
its electrostatic charge may be measured by the ESD unit. 
What has been disclosed is deemed to be illustrative of the principles of 
our invention. For example, comparator 40 has been shown as a separate 
hardware device. However, it should be understood that such comparisons 
may be made entirely in software withing microprocessor 30 and, indeed, 
microprocessor 30 or many of its functions and/or those of ESD 17, may be 
packaged together with those of FIU 20. Further and other changes may be 
made by those skilled in the art without, however, departing from the 
spirit and scope of our invention.