Most ESD programmes pick a resistivity range and consider the specification finished. The decisions that actually cause trouble come later: which parts get made from the board, how those parts are fabricated, and what everyone assumes the board protects against. This article is about that second half. For the numbers themselves and what each range is for, see our piece on what surface resistivity means in practice.
What gets made from it, and why that differs
The same dissipative board goes into four or five part types on one line, and they do not age alike.
- Layer pads stacked between boards or panels. These get slid against each other constantly, and abrasion is what removes a surface additive fastest. Pads are usually the shortest-lived ESD item in the area.
- Dividers and slots inside a tote. Moderate wear, mostly from parts going in and out rather than from handling.
- Tray inserts and nests. Low wear, but they are often the items that get cleaned most, which is a different kind of attack.
- Box walls and lids. Long service life, low wear, and the item most likely to be relied on for shipping.
Specifying one grade across all four means either paying for durability where it is not needed or replacing the pads far too often. It is worth splitting them.
Conversion changes the surface you qualified
A sheet qualification is measured on a flat face. The finished part is not a flat face, and the differences are not cosmetic.
Cut edges expose fresh material. With a permanent conductive filler the bulk is conductive, so a freshly cut edge behaves like the rest of the sheet straight away. With a migrating additive the new edge has no bloomed layer yet and has to rebuild one, so a box fresh off the machine can read differently from the same box next week. If you measure incoming parts the day they arrive, you may be measuring before they have settled.
Printing and labelling sit on top of the path you are relying on. Ink, ordinary tape and standard labels are insulators. A printed band running across the surface you expect to drain charge interrupts it locally, and a plain label over the contact area is the same problem in a smaller patch. In audits this is a recurring finding: correct board, plain vinyl label, no protection at the point that matters. Say early that the packaging is dissipative, and ask for ESD-rated labels and tapes to match.
Welding behaves differently too. Filled materials absorb heat differently and often need a longer dwell or a different temperature window, and if the joint is under- or over-welded it is a structural problem rather than an electrical one.
What antistatic board does not do
Three limitations are worth stating plainly, because assuming otherwise is expensive.
It does not shield. A dissipative board drains charge that reaches it. It is not a Faraday cage, and it will not protect the contents from a field or a discharge arriving from outside. Roughly handled shipments through uncontrolled environments belong in a shielding bag inside the board box. No amount of upgrading the board substitutes for that.
It does not stop generation. Two surfaces rubbing together in transit generate charge. Antistatic additives reduce how much, and they do not remove the mechanism. Packing a dissipative box tightly enough that parts move against each other defeats much of what you paid for.
It needs somewhere to drain to. Dissipative packaging sitting on an insulating shelf, carried on an insulating conveyor, handled by someone with no grounding, drains nothing. The board is one component of a control programme, and the weakest link elsewhere nullifies it.
Where the durable grade earns its cost
It is tempting to standardise everything on the permanent, filler-based material, and in a dry or heavily washed area that is usually right. In a moderate climate, on short-life internal parts that get replaced in a few months, it can be money spent twice over.
The honest rule we work to: durable construction for anything that is washed, anything in a dry environment, and anything expected to last more than about a year. Migrating construction for high-turnover internal parts in a normal-humidity area, replaced on a schedule. The second option has a genuine cost too – someone has to own the replacement interval, and that is often where it quietly stops happening.
One practical consequence that surprises people: filler-based material is effectively black. If your line uses colour to separate flows or departments, dissipative board cannot repeat that signal, and the visual control has to come from labels instead.
Checking it still works
None of this holds without occasional verification, and it takes minutes. A hand-held surface resistance meter with a concentric ring probe, a reading taken at the humidity the line actually runs at rather than in the office, and a note of the date. Repeat after washing cycles begin and roughly once a year after that. Readings that have drifted upward are telling you the packaging stopped doing its job somewhere along the way.
What we can do
We supply ESD corrugated PP boxes and dissipative PP board fabricated into pads, dividers, inserts and trays, with the grade chosen per part rather than per order. Tell us what each part does, how often it is cleaned and how dry the area runs – those answers decide the construction, and we will say so when the cheaper option is genuinely the right one.