Most ESD packaging failures are not material failures. The box measured in-band when it arrived, and it still measures in-band if you test it on a bench. What has changed is everything around it — the handling, the cleaning, the surfaces it touches, and the people.
Here is where protection actually degrades in a working electronics protected area, in roughly the order we see it.
1. The wash or the wipe-down
The most common cause by a distance. A topical antistatic treatment is removed by water and by most cleaning agents, and repeated wiping does the same thing more slowly. A box that was dissipative on delivery becomes insulative after twenty wash cycles, and nobody notices because incoming inspection happened once, at the start.
Two fixes. Either specify a compounded dissipative material for anything reusable, or add periodic re-testing to the maintenance schedule and re-treat when it fails. Both work; the first is less administrative.
2. Non-ESD items placed inside the box
An ESD box containing a normal polythene bag, a paperworks sleeve or a piece of standard foam has an insulated conductor sitting inside it. The box cannot drain charge from an item that is electrically isolated from it. This is extremely common and almost never audited, because the audit is done on the box rather than on the box-plus-contents.
If anything goes inside the box, it needs to meet the same requirements as the box. This includes dividers, labels and documentation wallets.
3. Contact with non-ESD surfaces
A dissipative box placed on a standard painted workbench or a normal conveyor belt is grounded through nothing. The material can still drain charge from its contents, but the path to earth is missing, and over time the whole assembly floats.
This is a facility issue rather than a packaging issue, and it is worth walking the actual route the boxes take rather than auditing them at a single station.
4. Dry air
Antistatic performance that depends on absorbed moisture degrades in low humidity. A heated warehouse in winter can sit well below the humidity at which the material was characterised, and a box that was compliant in September can be out of band in January.
If your ESD audit happens only in summer, this will not show up until a customer audit lands in February.
5. Wear at contact points
On a reusable box, the surfaces that get abraded are the corners, the rim and the base. If the dissipative property comes from a surface treatment, those are exactly the places where it goes first. Testing the middle of a flat panel will not reveal it — test the rim.
6. Mixed fleets
Once compliant and non-compliant boxes look identical, people cannot tell them apart. Two visually similar totes in the same loop is a guaranteed problem, and it is one of the strongest arguments for colour-coding an ESD fleet and keeping it physically separate.
If a non-ESD tote enters the loop — borrowed from another line during a busy week — it tends to stay.
What a useful audit looks like
- Test finished boxes in service, not samples from the store
- Test the rim and base, not just a flat panel
- Test at the humidity you actually run at, and repeat at a different time of year
- Test with the contents and inserts in place
- Re-test after a defined number of wash cycles rather than assuming the property is permanent
- Record the box ID so you can see whether failures cluster by batch or by age
That last point is the one that turns an audit into something actionable. Failures clustered by age tell you the property is degrading with use. Failures clustered by batch point at a production issue. Random failures usually mean the handling environment, not the box.
Specifying for a reusable programme
If boxes are going to be washed and reused, say so at the enquiry stage and specify a compounded dissipative material with the property through the section rather than on the surface. Ask what the material measures after the wash regime you actually run, and ask how many cycles that figure is based on.
We can supply corrugated PP ESD boxes in both constructions, and we would rather tell you which one suits your loop than sell you the wrong one twice.