APPENDICES
APPENDIX A
Maximum Allowable Resistances and Discharge Times for Static Safe
Operations
Reading from Operator
through:
Maximum Tolerable*
Resistance
Maximum Acceptable
Discharge Time
Floor mat to ground
1000 megohms
Less than 1 sec.
Table mat to ground
1000 megohms
Less than 1 sec.
Wrist strap to ground
100 megohms
Less than 0.1 sec.
*Minimum resistance to ground for each is 500 kilohms.
ESD Work-station Do’s and Don’ts
Do
Don’t
•
Test the wrist strap/operator combination
for continuity daily or install constant
monitors.
•
Test the mats quarterly.
•
Clean the mats with a cleaner designed
for static mats
•
Remove all nonessential plastic items
from the workstation area. Insulative
plastic items can store large amounts of
static charge that is not removed when
placed on a mat or grounded. Examples
include: Styrofoam cups, plastic lunch
bags and containers, combs and brushes.
•
Require personnel that wear heel
grounders to also wear a wrist strap when
they sit at a workbench. Most people lift
their feet or heels off the floor at some
point while seated.
•
Use GFCI outlets when working with
energized items.
•
Avoid parallel ground paths. The only
connection to ground for an operator at
an ESD workstation should be the wrist
strap, heel grounders or work surface.
Other uncontrolled ground paths could
create a shock hazard.
•
Equipment and tools in the working area
must be grounded
•
Do not ground the mat by
one snap and connect the
wrist strap to the other snap.
This adds the resistance of
the mat to the ground path.
•
Do not “daisy chain” mats
together. Each mat must be
connected to the ground
point - not connected to the
ground point through another
mat.
•
Do not use commercial
cleaners on mats. The
cleaners may leave a residue
that prevents the mat from
draining away charge.
6-2 Preliminary Release
3/24/05