Is conductive always better than dissipative for ESD protection?

No. Conductive is better for shipping cartons (fast drain) and PCB trays (equipotential), but worse for parts bins (can shock components through faster discharge). The right grade depends on the application — most in-plant ESD storage should be dissipative, most shipping should be conductive.

Can I mix conductive and dissipative containers in the same EPA?

Yes — most EPAs use both. Conductive corrugated boxes for outbound, dissipative bins for in-plant storage, and conductive ground mats on benches. Make sure every container is grounded (directly or through the bench mat) and labeled clearly so handlers do not confuse them.

What surface resistance does ANSI/ESD S20.20 actually require?

S20.20 itself does not mandate a single resistance — it mandates that your EPA program controls electrostatic discharge to under the susceptibility of your most-sensitive part. In practice, packaging and bins between 10⁴ and 10¹¹ Ω/sq, plus a grounded bench and wrist strap, satisfy the typical Class 100V HBM requirement.

Does humidity change which grade I need?

Low humidity (under 30% RH) increases triboelectric charging — so in dry climates, faster drain (conductive cartons, conductive floor mats) becomes more important. Permanent dissipative materials hold their rating under 12% RH; pink poly anti-static loses most of its effect under 30% RH.

Conductive vs Dissipative ESD Packaging — Surface Resistance, Standards, When to Use

The numbers (ANSI/ESD S20.20)

Conductive: surface resistance below 1 × 10⁴ Ω/sq up to 1 × 10⁶ Ω/sq. This is the lower-resistance category — charge drains fast.

Static-dissipative: surface resistance 1 × 10⁶ Ω/sq up to 1 × 10¹¹ Ω/sq. Charge drains in a controlled rate — slow enough to avoid sparking, fast enough to prevent buildup.

Insulative: anything above 1 × 10¹¹ Ω/sq. This is normal plastic and is what you are trying to avoid touching ESD-sensitive components.

The transition between conductive and dissipative is fuzzy at the 10⁵–10⁶ Ω/sq boundary; some standards bodies (IEC 61340-5-1) draw the line slightly differently. For purchasing purposes, treat 10⁴–10⁶ Ω/sq as "conductive grade" and 10⁶–10⁹ Ω/sq as "dissipative grade."

When to use conductive

Shipping cartons (conductive corrugated boxes). The fastest charge drain is desirable for outbound packaging where the package may sit on a conveyor or get rubbed against other surfaces — you want any built-up charge to leak away immediately.

PCB transport trays (conductive PS or HIPS). The board is at the same potential as the tray, so any handler can pick the tray up without inducing voltage on the board.

Grounded EPA work surfaces and floor mats. Conductive grade gives the lowest resistance to ground — the standard for an EPA worker bench.

Where you should NOT use conductive: in contact with powered components or boards. A conductive surface can short-circuit live circuits.

When to use dissipative

Component bins and parts storage (ESD storage box, ESD bin shelf). Slow controlled drain prevents fast discharge through sensitive ICs.

In-plant WIP containers (ESD containers, foldable ESD boxes). Components transition between handlers and stations — dissipative is the safe default.

ESD garments, wrist straps, and accessories. Always dissipative — never conductive against skin.

Material choices that hit each grade

Conductive: carbon-loaded HDPE / PP (containers), conductive PS or HIPS (thermoformed trays), carbon-impregnated corrugated board (shipping cartons), conductive foam.

Dissipative: carbon-loaded PP / HDPE at lower carbon fraction, inherently dissipative polymers (IDP), pink anti-static polyethylene (commodity but degrades with humidity and washing — avoid for permanent use).

How to verify what you bought

Ask for a Certificate of Compliance that calls out the test method (ANSI/ESD S20.20 STM11.11 or STM4.1) and the measured range, not just "ESD-safe."

For high-volume buyers: spot-check incoming lots with a surface resistance meter (Prostat PRS-801 or equivalent). Measure 3 points on each of 3 random units per lot; reject if any reading is outside the spec window.

Walk away from any supplier who says "ESD-safe" without giving you a number.

Conductive vs Dissipative ESD Packaging — Which One You Need