Conductive vs Dissipative vs Insulative: What the Resistance Ranges Actually Mean

Most explanations of these three categories stop at the definitions. This one includes measured readings taken on a single product — both layers of one two-layer bench mat, tested on an ACL Staticide Model 800, with the temperature and humidity recorded alongside every reading.

The Three Categories in One Sentence Each

All three describe how easily charge moves across or through a material. The difference is only a matter of how much resistance stands in the way.

Conductive

Charge moves almost freely. Resistance is low, so a charged object touching a conductive surface loses its charge quickly. In ESD control this is used where fast, reliable charge removal matters more than controlling the speed of the discharge.

Static dissipative

Charge still moves, but slowly enough that the discharge is spread out over time rather than happening in one spike. This is the behaviour wanted on a worksurface where sensitive components are handled.

Insulative

Charge does not move. It stays where it was generated. Ordinary plastics, cardboard and untreated packaging are insulative, which is why they are kept out of an EPA even when they never touch a component.

Why the Boundaries Are Where They Are

The two ends of the scale fail for opposite reasons, and understanding both explains why the useful range sits in the middle.

Too conductive: the discharge happens too fast

Connecting a charged object to ground through near-zero resistance does remove the charge, but it does so almost instantaneously. That produces a current spike, and the spike is itself an ESD event. It can couple into nearby circuitry even when nothing was touched directly. This is the reason wrist strap cords contain a 1 megohm resistor rather than a plain wire.

Too insulative: the charge never leaves

At the other end, charge generated by friction simply stays on the surface. A worker moves a plastic tray across a bench, the tray carries a field, and the next component that comes close is exposed to it. Nothing in the process gives the charge anywhere to go.

The middle: controlled removal

Static dissipative material removes charge, but over a longer interval. The energy is dissipated gradually instead of released at once. That is the whole design intent, and it is why an ESD worksurface is not simply made as conductive as possible.

Measured on a Single Product — Both Layers of One Bench Mat

A two-layer bench mat is a useful specimen for this comparison because both categories are present in one piece of material. The green working surface is specified as static dissipative; the black backing layer is specified at a lower resistance. We measured both.

Green working surface — specified 1×10⁶ to 1×10⁹ Ω

ID	Measured PTP resistance	Within specified range
PTP-T01	2.00 × 10⁶ Ω	Yes
PTP-T02	2.01 × 10⁶ Ω	Yes

Observed range: 2.00 × 10⁶ to 2.01 × 10⁶ Ω. Both readings sit near the low end of the specified band — closer to 10⁶ than to 10⁹.

Black backing layer — specified 1×10⁴ to 1×10⁶ Ω

ID	Measured PTP resistance	Within specified range
PTP-B01	5.76 × 10⁴ Ω	Yes
PTP-B02	3.12 × 10⁵ Ω	Yes
PTP-B03	3.12 × 10⁵ Ω	Yes
PTP-B04	6.23 × 10⁴ Ω	Yes
PTP-B05	6.26 × 10⁴ Ω	Yes
PTP-B06	3.50 × 10⁴ Ω	Yes

Observed range: 3.50 × 10⁴ to 3.12 × 10⁵ Ω. The spread across six locations is roughly one order of magnitude, which is normal for a filled rubber compound and is one reason a single reading is not a sufficient basis for acceptance.

The Naming Problem Nobody Mentions

Product literature across this industry — ours included — routinely calls a low-resistance backing layer the “conductive layer”. Measured at 10⁴ to 10⁵ ohms, that layer is well above the resistance of an actual conductor, and depending on which standard’s classification you apply, it may fall inside the dissipative band rather than the conductive one. This is a naming convention, not a defect. It describes the layer’s role relative to the working surface above it, which is what matters when assembling a bench. But it causes real confusion during incoming inspection, because an inspector reading “conductive” may test against a conductive-class limit that the product was never designed to meet. The practical rule: compare each measurement against the specification for that specific layer, not against a category name. If a datasheet gives you a category word without a numeric range, ask for the range.

Where Each Category Belongs in an EPA

Location	Typical requirement	Why
Worksurface	Dissipative	Components rest here; discharge must be slowed, not accelerated
Mat backing layer	Low resistance	Carries charge from the working surface to the ground path
Flooring	Dissipative or conductive, per programme	Works as a system with footwear; the combined value is what matters
Personnel path	Dissipative + 1 MΩ resistor	Operator safety and controlled discharge
Packaging entering EPA	Never insulative	Insulative material holds a field even when untouched

How These Values Are Measured

Point-to-point vs resistance-to-ground

Point-to-point (PTP) places two electrodes on the same surface and measures the resistance of the material between them. Resistance-to-ground (RTG) places one electrode on the surface and connects the other to the earth point, measuring the whole path including the cord, the snap and the connection. They answer different questions. PTP tells you about the material. RTG tells you whether the installation works. A mat can pass PTP and fail RTG if the ground cord is faulty, and that is one of the more common causes of a workstation being ungrounded without anyone noticing.

Why temperature and humidity must be recorded

Surface resistance in these materials varies with humidity. The readings above were taken at 81.7–82.5 %RH — a South China summer. The same mat measured in a heated European workshop in January would not necessarily read the same. A resistance figure published without its conditions is incomplete, which is why every table above carries them.

Common Mistakes

Testing a two-layer mat against a single range

The most frequent incoming-inspection failure we see. The inspector applies the working-surface range to both layers, the backing reads 10⁴ and gets marked as out of specification. Nothing is wrong with the mat; the wrong limit was applied.

Taking one reading and calling it done

The six backing-layer readings above span roughly one order of magnitude across a 25 × 30 cm sample. A single measurement anywhere in that spread would be true and also unrepresentative.

Ignoring the display units

The ACL Model 800 shows “ohms/sq” on its display at all times. The instrument panel states that readings taken with the external electrodes are in ohms. In practice the industry treats the two as interchangeable for this measurement, and no customer has raised it with us — but it is worth knowing why the display says what it says.

Comparing figures measured under different conditions

Two datasheets showing different numbers may simply have been measured at different humidity. Without conditions, the comparison is not meaningful.

Frequently Asked Questions

Related

For the construction and specifications of the mat tested here, see our two-layer rubber ESD bench mat. For the measurement procedure in more detail, see how to test an ESD mat.