How to Store and Bake MSL Components Before Reflow
Moisture-sensitive devices (MSD) absorb water from the air and can crack during reflow as trapped moisture flashes to steam (the popcorn effect). This guide explains the MSL levels from J-STD-020, floor life, dry cabinet storage and correct baking per J-STD-033.
View dry storageWhat do MSL levels and floor life mean?
The Moisture Sensitivity Level (MSL) classifies, per IPC/JEDEC J-STD-020, how sensitive a component package is to humidity. The matching floor life states how long a device may stay outside dry storage after the sealed bag is opened, referenced to 30 °C and 60 % RH, before it has to be soldered.
MSL 1 is uncritical and has no limit. From MSL 2 onward a clock starts: once the floor life is exceeded, the part must be baked before reflow. The label on the moisture barrier bag states the MSL level and the permitted floor life.
How do you store MSD parts dry the right way?
Opened MSD parts belong in a dry cabinet below 5 % relative humidity, or back in a sealed moisture barrier bag (MBB) with fresh desiccant. At very low residual humidity the floor-life clock effectively pauses, so components can be held without another bake.
- Dry cabinet at < 5 % RH: the standard for MSL 2 to MSL 5a, halting moisture uptake.
- Ultra-dry cabinets at < 1 % RH: even speed up desorption of residual moisture.
- Moisture barrier bag with silica gel and HIC: seal for shipping and long-term storage.
- Floor-life reset: per J-STD-033, depends on storage humidity and prior exposure time.
When and how do you bake before reflow?
If the floor life is exceeded or the HIC has changed colour, the part must be baked before reflow. The standard is a bake at 125 °C; the duration depends on package thickness and MSL level and can run from a few hours to well over 24 hours. For temperature-sensitive carriers, gentler profiles at 90 °C or 40 °C are defined.
- After baking, a fresh floor life begins - restart the clock.
- Document the bake with lot, temperature and duration.
- Process baked parts promptly or return them to dry storage.
Frequently asked questions
What is the popcorn effect?
Moisture absorbed into the package flashes to steam during reflow. The pressure can swell or crack the package and cause delamination as well as cracks at the bond wires.
How do I know if I need to bake?
When the floor life since opening is exceeded, or the Humidity Indicator Card reads too high. MSL 1 is exempt, while MSL 6 is always baked before every reflow.
Is a dry cabinet enough instead of baking?
If parts are stored below 5 % RH in time, yes - the cabinet halts moisture uptake. Once the floor life is already exceeded, only a bake per J-STD-033 replaces baking.
Which standard governs baking?
IPC/JEDEC J-STD-033 defines handling, storage and bake profiles, while J-STD-020 defines the MSL classification of the components.
Looking for dry storage and a bake oven?
We supply dry cabinets below 5 % RH, moisture barrier bags, desiccant and indicator cards - matched to J-STD-033.
Standard-compliant
Processes to IPC/JEDEC J-STD-020 and J-STD-033.
Defined dry
Cabinets stay safely below 5 % RH.
Traceable
Floor life and bake lots are documentable.
Expert advice
ESD specialists help with the selection.