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Two standards, two jobs. J-STD-020 decides which MSL a device is — its moisture sensitivity classification. J-STD-033 then dictates how that device must be handled, packed and shipped. Conflating the two leads to floor-life and dry-pack arguments settled with the wrong document.
| Standard | Question it answers |
|---|---|
| J-STD-020 | What is this device's moisture sensitivity level? (the classification procedure) |
| J-STD-033 | Given that level, how must it be handled, packed, shipped and used? |
JEDEC defines the rated moisture sensitivity level (MSL) as the moisture sensitivity level as determined by J-STD-020. That definition is the cleanest statement of the boundary: J-STD-020 rates, J-STD-033 applies.
Floor life is the maximum time a component may be exposed to ambient conditions after removal from its moisture barrier bag before either reflow must occur or the part must be baked. The reference condition matters: floor life is tabulated against a stated ambient, commonly quoted as 30 °C / 60% RH.
| MSL | Floor life | Practical meaning |
|---|---|---|
| 1 | Unlimited | No dry pack needed for floor-life purposes; the condition is quoted at 30 °C / 85% RH. |
| 2 – 5 | Finite, decreasing with level | Dry pack required; the clock starts when the bag is opened. |
| 6 | Mandatory bake before use | After baking, the part must be reflowed within the time limit stated on the label. |
The finite times per level are tabulated in the standard — take the figure from the revision your process references rather than from a secondary table. How the clock is managed once the bag is open is covered in floor life and baking.
Because the dry-pack requirement in J-STD-033 is indexed to MSL, a higher level means a stricter pack. That is the whole reason desiccant, a humidity indicator card and a moisture barrier bag appear on a bill of materials at all — see how the three parts fit together.
One warning that matters commercially: J-STD-020 does not classify bare PCBs. The absence of an MSL on a bare board is not an oversight — it is outside the standard's scope, and it is a question buyers get wrong routinely.
| Ask | Why |
|---|---|
| Which revision of J-STD-033 does your pack follow? | B.1, C.1 and D differ |
| What is the device's MSL, and per which J-STD-020 revision? | the number alone is meaningless without the revision |
| Is the desiccant fresh or regenerated? | exhausted desiccant is not protection |
| Is the card reversible, and which spot set? | 5 / 10 / 60 is the common set |
| Was the bag heat-sealed? | folded or taped is not sealed |
Written by the VEN Desiccant export team from the JEDEC standard listings, the JEDEC dictionary definition of rated MSL, and published industry guidance summarising floor life and dry-pack conditions. Drafting was AI-assisted; the standard-version references and the MSL boundary were checked against the sources named above and edited by our team before publication. We publish it to stop the two standards being used interchangeably. Floor-life times per level are tabulated in the standard — take them from the revision your process references.
Last checked: 11 October 2026.
Tell us the MSL and the revision your process follows and we will quote the pack specification.
