2
Un der st a n din g Su r fa ce Re sist ivit y
For ESD purposes, m at erials are classified by t heir resist ance
t o t he m ovem ent of elect r icit y. The follow ing ranges and
definit ions are found in ESD Associat ion or EI A st andards
publicat ions.
Con du ct ive m a t e r ia ls:
Wit h a low elect r ical resist ance,
elect rons flow easily across t he surface or t hrough t he bulk
of t hese m at erials. Charges go t o ground or t o anot her con-
duct ive obj ect t hat t he m at erial cont act s or com es close t o.
Conduct ive m at er ials have a surface resist ivit y less t han 1 x
10
5
Ω/
sq or a volum e resist iv it y less t han 1 x 10
4
Ω
- cm .
D issipa t ive m a t e r ia ls:
For t hese m at erials, t he charges
flow t o ground m ore slow ly and in a som ew hat m ore con-
t rolled m anner t han w it h conduct ive m at erials. Dissipat ive
m at erials
have a surface resist ivit y equal t o or great er t han 1 x 10
5
Ω/
sq but less t han 1 x 10
12
Ω/
sq or a volum e resist iv it y equal
t o or great er t han 1 x 10
4
Ω
- cm but less t han 1 x 10
11
Ω
-
cm .
2
I n su la t ive m a t e r ia ls:
I nsulat ive m at er ials prevent or lim it
t he flow of elect rons across t heir surface or t hrough t heir
volum e. I nsulat ive m at erials have a high elect rical resist ance
and are difficult t o gr ound. St at ic char ges rem ain in place on
t hese m at erials for a very long t im e. I nsulat ive m at er ials
are defined as t hose having a surface resist iv it y of at least 1
x 10
12
Ω/
sq or a volum e resist iv it y of at least 1 x 10
11
Ω
- cm .