Floor life, baking and the rack in between

Floor life is a clock. It starts when a moisture barrier bag is opened and it runs while the parts sit in the factory atmosphere. The most common misunderstanding about it is that putting boards somewhere tidy slows it down.

A rack does not stop the clock

A rack holds boards apart. It does not change the humidity around them, and moisture uptake is driven by the atmosphere, not by whether the boards are neatly arranged.

Boards in a rack on an open floor are accruing floor life at the same rate as boards in a tote next to them. The rack is solving damage, handling and traceability. It is not solving moisture.

What stops the clock is a controlled environment: a dry cabinet at low relative humidity, or resealing into a moisture barrier bag with fresh desiccant. Those are the two mechanisms. Everything else is bookkeeping.

Why the rack still matters to the clock

Indirectly, and significantly, because floor life is only manageable if you know when it started.

The practical failure is not usually running out of floor life. It is losing track of which boards were opened when, and having to bake a whole batch because nobody can prove otherwise. That is a traceability failure wearing a moisture costume.

A rack with identifiable slots is where that gets solved. One board per slot, slot numbers, and the bag-open date recorded against the slot rather than against a pile. There is more on this in labelling and tracing boards in a rack.

When baking becomes the answer

When the clock has run out, or when it cannot be established. The conditions are set by the moisture sensitivity level of the devices and the thickness of the package, and they are not a matter of local preference. Our note on baking MSD boards per J-STD-033 covers what the standard specifies.

The thing to plan for before you get there is what the boards sit in while they bake. An oven at baking temperature is well outside what an ordinary storage rack is built for, and a rack that softens in an oven takes its slot geometry with it.

The trap in the handoff

Most floors have a rack for storage and a different rack for baking, which is correct. The trap is the moment between them.

Boards get transferred from the storage rack to the oven rack, and that transfer is where identity is most often lost. If the slot numbering does not carry across, the batch comes out of the oven correctly baked and no longer traceable to the bag-open dates that sent it there.

Numbering both racks the same way is a small thing that removes an entire category of problem.

What to have in place

Somewhere controlled for anything with a live clock, whether that is a dry cabinet or resealed bags. A rack with identifiable slots so the clock can be attributed to specific boards. A high temperature rack rated for your bake conditions, kept separate from the storage racks. And matching slot identification across both, so nothing is lost in the handoff.

The rack is not the moisture control. It is what makes the moisture control auditable, which in practice is what stops good boards being baked unnecessarily.