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MSL Floor Life Table and Dry Pack Handling Reference

Moisture sensitive devices can crack in reflow if they absorb too much humidity before assembly. This table lists the MSL levels and floor life limits that an SMT line has to enforce, along with the dry pack rules.

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Item	Category	Value	Note
MSL 1	Level	Unlimited floor life	At or below 30 deg C and 85% RH
MSL 2	Level	1 year floor life	At or below 30 deg C and 60% RH
MSL 2a	Level	4 weeks floor life	At or below 30 deg C and 60% RH
MSL 3	Level	168 hours floor life	At or below 30 deg C and 60% RH
MSL 4	Level	72 hours floor life	At or below 30 deg C and 60% RH
MSL 5	Level	48 hours floor life	At or below 30 deg C and 60% RH
MSL 5a	Level	24 hours floor life	At or below 30 deg C and 60% RH
MSL 6	Level	Time on label (TOL)	Must be baked before use and reflowed within the time printed on the label
Floor life clock start	Rule	When the sealed bag is opened	Record bag open date and time on the reel or in the MES
Sealed bag shelf life	Rule	At least 12 months	At or below 40 deg C and 90% RH, per J-STD-033
Humidity indicator card	Check	Read when bag is opened	Spots show the humidity inside the bag, compare with the card limits for the MSL
Moisture barrier bag	Packing	Sealed with desiccant and indicator card	Also carries a caution label with the MSL and peak body temperature
Peak package body temperature	Label	Printed on caution label	Do not exceed this peak in reflow, lead free parts are often rated higher than tin lead
Bake	Recovery	Time and temperature depend on package thickness and MSL	Use the bake table in J-STD-033, never improvise, and check reel and tape ratings before baking
Reels not rated for high temperature	Recovery	Low temperature bake only	Many plastic reels cannot go through high temperature bake, move parts to a rated carrier
Dry cabinet storage	Storage	Low humidity cabinet	Follow J-STD-033 for how exposure time can be paused or reset, and keep records
Repeated reflow	Rule	Reflow count is limited	Typical limit is three reflow passes unless the datasheet states otherwise, include rework
Exposed out of bag overnight	Event	Compare exposure with the floor life	If beyond the limit, bake or scrap per your procedure and log it

Use this table as a quick lookup only. The controlling documents are IPC/JEDEC J-STD-020 for classification and J-STD-033 for handling, plus the label on the bag.

Floor life tracking from ERP data

Interested in linking reel open times to ERP lots? We can discuss options.

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How to use the table

Read the MSL printed on the caution label of the bag, then find that level in the table to see how long the part can stay out of the bag before reflow. Start the clock when the bag is opened and record the time. If the exposure exceeds the floor life, the part needs a bake according to J-STD-033 before it can be used. Export the table for your handling work instruction.

What the standards say

J-STD-020 classifies a component by how much moisture it can absorb and survive reflow. J-STD-033 describes how to pack, store and handle those parts. The most common level on a typical line is MSL 3 with a floor life of 168 hours, but many fine pitch BGAs and QFNs are MSL 3 or higher.

Always read the label, not just the datasheet
Track exposure per reel, not per job
Count every reflow pass including rework

Worked example

A reel of MSL 3 BGAs is opened on Monday morning and about 30 hours are used on the line. The reel goes back to a dry cabinet. The remaining floor life is 168 minus 30 hours, but the actual treatment depends on how your cabinet and procedure follow J-STD-033. The log records the open date, hours used and the storage condition.

Common mistakes

Common errors include losing track of the open time when a reel is split, baking reels that are not rated for the bake temperature, and ignoring the second side of a double sided board where components wait for a second reflow. Another mistake is assuming that a humidity card in the green zone resets the floor life clock.

Frequently Asked Questions

What does MSL 3 mean?

MSL 3 allows 168 hours of floor life at up to 30 deg C and 60% RH after the bag is opened. After that, the part has to be baked before reflow. It is a very common level for BGAs and QFNs.

What is the difference between MSL 2 and MSL 2a?

MSL 2 allows one year of floor life, while MSL 2a allows four weeks, both at up to 30 deg C and 60% RH. The device with MSL 2a absorbs moisture faster.

Can I bake parts while they are on the reel?

Only if the reel and tape are rated for the bake temperature. Many are not. Follow J-STD-033 and the supplier guidance, and move parts to a high temperature carrier when needed.

Does the sealed bag expire?

Sealed bag shelf life is at least 12 months under the specified storage conditions per J-STD-033. If the date is exceeded or the humidity card shows too much moisture, check the part before use.

If you want floor life tracked automatically against ERP receipts and issues, Netray can discuss how to connect those records.

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