Storing MSD correctly: floor life, MSL and dry storage under IPC/JEDEC J-STD-033

Modern SMD components absorb moisture from the ambient air. If the component is then heated in the reflow oven, the trapped moisture expands abruptly. Possible consequences are package cracking ("popcorning"), delamination or hidden damage that only shows up later in use. This article explains concisely how to handle and store moisture-sensitive devices (MSD) in line with IPC/JEDEC J-STD-033.

1) MSL and floor life: the basics

Every moisture-sensitive component is assigned a Moisture Sensitivity Level (MSL) from 1 to 6 according to J-STD-020. The floor life is the time a component may remain in the factory environment (up to 30 °C and 60% relative humidity) after the dry bag has been opened before it must be processed. Common values:

• MSL 1: unlimited (up to 30 °C / 85% RH)
• MSL 2: 1 year, MSL 2a: 4 weeks
• MSL 3: 168 hours, MSL 4: 72 hours
• MSL 5: 48 hours, MSL 5a: 24 hours
• MSL 6: bake before use, time on label (TOL)

Floor life starts as soon as the bag is opened and keeps running while the component is exposed to air. The information on the component manufacturer's label is always decisive.

2) Before opening: dry bag

Moisture-sensitive components are delivered in an airtight bag with desiccant and a humidity indicator card. As a rule, a shelf life of at least twelve months applies in the unopened bag; the exact figure is printed on the bag. When opening, check the indicator card: if it shows excessive humidity, the component must be baked before processing.

3) After opening: storage in a dry cabinet

If not all components are processed immediately, they belong in a dry cabinet with controlled low humidity. Two variants are common:

• ≤ 5% RH for standard MSD. According to the manufacturer's datasheet, a cabinet of this class meets the storage requirements of the standard (in our range: X2B series).
• ≤ 1% RH for particularly sensitive components or corresponding customer requirements (F1 series).

The behavior of the cabinet with the door open also matters: according to the datasheet, an X2B cabinet returns to below 5% RH within 30 minutes after the door has been open for 30 seconds. Therefore open it only when necessary and document storage times. A data logger, an alarm for limit violations and the reminder to calibrate the hygrometer (after 365 days) help with quality assurance records.

The exact rules on when dry storage pauses or resets floor life depend on the MSL and prior exposure. They are laid out in the standard; when in doubt, the component manufacturer's specification applies.

4) Floor life exceeded: baking

If floor life has expired, the components must be baked before soldering. Table 4-1 of the standard gives conditions depending on package thickness and MSL, for example at 125 °C, at 90 °C with at most 5% RH or at 40 °C with at most 5% RH. Important in practice:

• Many carrier tapes (reels) are not designed for high temperatures and deform above 40 °C. Then only gentle baking at 40 °C remains, which takes much longer (days to weeks depending on the package).
• An oven with ambient air can cause oxidation and discoloration of the leads. A baking dry cabinet that combines heat with very low humidity is better.
• After baking, the components should stay dry in the same cabinet so that they do not absorb moisture again.

5) Practical checklist

• Note the opening date and time on the bag or reel.
• Put open components into the dry cabinet quickly and use them first in, first out.
• Record humidity and temperature in the cabinet (data logger).
• Set up an alarm and calibrate the hygrometer regularly.
• Observe the limits and baking rules of the component manufacturer, not only the general standard.

6) Which cabinet fits?

The choice depends on the humidity requirement, reel size and quantity. The selection guide gives you a recommendation with a guideline for the number of reels. Baking dry cabinets for baking and dry storage are in the T series. smt-Sander is happy to advise you: info@smt-sander.de.

Note: This article gives an overview and replaces neither the IPC/JEDEC J-STD-033 standard nor the component manufacturer's specifications. As of: 14.10.2026.