Many surface-mount ICs absorb moisture from the air. If they are soldered after absorbing too much, the moisture can turn to steam during reflow and crack the package or cause delamination inside. That is why moisture-sensitive parts are shipped in sealed bags with desiccant, and why buyers of surplus stock ask how it was stored. This guide explains moisture sensitivity levels and how to store and describe moisture-sensitive surplus parts.
Key takeaways
- Moisture sensitivity level (MSL) tells you how long a part can be exposed to factory air before it needs baking. The levels are defined in the IPC/JEDEC J-STD-020 standard, and handling is described in J-STD-033.
- Sealed moisture barrier bags with desiccant and a humidity indicator card protect the parts. Once a bag is opened, the exposure time starts.
- When you offer surplus, say whether moisture-sensitive parts are still in sealed bags. It is one of the first things buyers ask.
What is a moisture sensitivity level?
The MSL of a part is shown on the moisture barrier bag label and in the manufacturer's documentation. It indicates the allowed floor life: how long the part can stay out of dry storage, under factory conditions, before it must be baked or otherwise dried before soldering.
| MSL | Typical floor life (out of the bag, at up to 30 °C / 60% RH) |
|---|---|
| 1 | Unlimited (at up to 30 °C / 85% RH) |
| 2 | 1 year |
| 2a | 4 weeks |
| 3 | 168 hours |
| 4 | 72 hours |
| 5 | 48 hours |
| 5a | 24 hours |
| 6 | Must be baked before use; time on label |
Always follow the label and the manufacturer's instructions for the specific part. The table is a general summary of the standard levels.
How are moisture-sensitive parts packed?
- A moisture barrier bag (MBB), heat-sealed.
- Desiccant packs inside the bag.
- A humidity indicator card (HIC) that changes color when humidity inside the bag rises above set levels.
- A moisture-sensitive caution label on the bag showing the MSL and handling instructions.
How should you store surplus moisture-sensitive parts?
- Keep sealed bags sealed until a buyer is confirmed. Do not open bags to count or photograph parts if you can avoid it; photograph the label instead.
- Store opened parts in dry storage, such as a dry cabinet, or reseal them in a moisture barrier bag with fresh desiccant and a humidity indicator card, following J-STD-033.
- Record when bags were opened and how long parts were exposed, if you know.
- Keep storage cool and dry, away from direct sunlight and large temperature swings.
What should you tell buyers?
- The MSL from the bag label.
- Whether bags are factory sealed or have been opened.
- The humidity indicator card reading, if a bag has been opened.
- Any baking done, if you know.
Buyers can then decide whether the parts need baking before use. Clear storage information makes a lot easier to sell.
How to offer your stock through StockWake
Have excess or obsolete electronic components? Send us your list. We review it and reply by email if there is a fit. Your company name and contact details are never shown on the site.
You set a floor price. When we find a buyer, we sell above your floor price — our margin is the difference, and we charge you no fees. Goods ship directly from your location to the buyer; nothing needs to be imported into China.
Add the storage condition to your list, for example "sealed MBB" or "opened, in dry cabinet". See How to Prepare a Surplus Inventory List Buyers Can Act On for the other columns to include.
Frequently asked questions
Can I still sell moisture-sensitive parts from an opened bag? Often, yes. Describe the condition honestly, including the MSL and how the parts have been stored since opening. The buyer can bake them before use if needed.
Do MSL 1 parts need a moisture barrier bag? MSL 1 parts have unlimited floor life under the conditions in the standard, so dry packing is not required for moisture reasons. Follow the manufacturer's packaging for other reasons, such as ESD protection.
Does baking damage parts? Baking follows the conditions in J-STD-033 and the manufacturer's instructions. Repeated or incorrect baking can affect solderability, so follow the guidance for the specific part.
Ready to start? Send us your surplus list.