Static-Sensitive Assemblies Packed Without Adequate ESD Protection
Boards shipped in ordinary polythene arrive with latent static damage; how the packing stack, container humidity and the evidence file should be handled.
Representative scenario, not a specific client engagement. This page describes how a shipment of this kind is genuinely handled — the constraints, the approach, and where it commonly goes wrong. It does not name or describe a real Transeasy customer. Our two documented project moves are the Mexico container move and the India overweight cargo delivery.
The situation
Semiconductor devices and populated boards are damaged by electrostatic discharge at levels a person cannot feel. Human body model thresholds for many components sit in the hundreds of volts, while walking across a synthetic floor covering generates thousands. The damage is often not immediate failure but a weakened junction that passes factory test and fails weeks later in service. Where such assemblies travel in clear polythene, bubble wrap and plain corrugated cartons, nothing in the packing stack shields or dissipates charge.
A sea leg to Europe makes this worse rather than merely longer. Five or six weeks inside a steel box brings repeated condensation cycles, constant vibration that shifts unrestrained items inside their boxes, and handling by people with no reason to know what is inside. Friction between a board and a non-dissipative bag during that motion generates charge continuously. The consignment arrives looking perfect, and the loss surfaces later as an unexplained field failure rate nobody can attribute.
What made it difficult
- ESD damage is usually latent rather than catastrophic, so the goods pass inbound inspection and the eventual fault is blamed on the component instead of the packing.
- Pink antistatic film limits charge generation but provides no Faraday shielding, so it is not a substitute for a metallised shielding bag.
- Containers cycle through condensation at sea, and humidity-dependent antistatic coatings lose effectiveness well before the carton is opened.
- Liability is difficult to allocate after the fact, because no arrival inspection can separate handling damage from a manufacturing defect.
How it is approached
The specification should be written as a stack rather than a single item. Sensitive devices belong inside a metallised shielding bag that closes as a Faraday cage, heat sealed or folded and taped rather than left open. Bags sit in dissipative trays or a conductive inner box, and the outer carton carries the ESD sensitivity symbol so that nobody opens it casually. Moisture-sensitive devices additionally need desiccant and a humidity indicator card inside a sealed moisture barrier bag.
Then the container itself, where static risk and water risk are answered by the same discipline. Fill the voids so nothing can move, and control the moisture. That means blocked and braced pallets, stretch wrap taken down to the pallet rather than loose top layers, desiccant sized against the moisture content of the cargo and its dunnage, and a liner or desiccant sheet where the load is large. Timber that is not kiln dried releases moisture for the whole voyage.
Where damage is suspected on arrival, the sequence is evidence first. Photograph the packing as it is opened, keep the bags and cartons, and read the humidity indicator card before anything is discarded. A surface resistivity check on the bags actually used establishes whether they were shielding, antistatic or plain film. That distinction decides whether the exposure sits with the shipper packing method, with handling in transit, or with the device itself, and no surveyor will form a view without it.
Prevention belongs in the purchase order rather than in an instruction to the packing bay. Specify bag construction by standard instead of by colour, require the ESD symbol on the outer carton, require a sealed moisture barrier bag with desiccant and indicator card for moisture-sensitive parts, and ask for photographs of one sealed representative carton before loading. A forwarder should be testing that specification against the mode and the transit time before the booking is confirmed.
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Takeaways
- Antistatic and shielding are different functions, and only a metallised shielding bag protects a device against a discharge from outside the bag.
- A five to six week sea transit converts marginal packing into cumulative damage through vibration, condensation and repeated handling.
- Because the loss is latent, the only real defence is a documented packing specification agreed before production, not an inspection on arrival.
- Retaining the opened packaging and reading the humidity indicator card is what makes a claim assessable at all.
Frequently asked
Pink film limits charge generation between the bag and the device, but it does not shield. A discharge to the outside of the bag can still reach the contents. For static-sensitive assemblies the working rule is a metallised shielding bag as the primary enclosure, with dissipative foam or trays inside it, and pink film reserved for mechanical parts that are not sensitive. Many pink films are also humidity dependent, which a long sea leg works against.
Yes, for two reasons. A sealed moisture barrier bag protects the device but not the carton, the pallet or the timber dunnage, and wet fibreboard loses stacking strength long before anyone unpacks it. Desiccant also protects humidity-dependent antistatic coatings on secondary packaging. The quantity should be calculated from the moisture content of the cargo and dunnage and the expected voyage length, not fixed at one bag per container.
It is rarely proved outright, which is why the record matters. The usable evidence is the packing itself: bag construction and surface resistivity, whether the seals were intact, the humidity indicator card reading, and photographs taken as the carton was opened. Failure analysis on the returned devices can show discharge signatures at the junction. Without the retained packaging, a surveyor cannot separate transit damage from a component defect.