MSL Floor Life Remaining Calculator for SMT Lines
Moisture sensitive parts can crack or delaminate during reflow if they absorb too much moisture before soldering. This calculator tracks the floor life clock for a lot so supervisors know how long they have before a bake is required.
Your numbers
Read the MSL on the moisture barrier bag label. MSL 6 is time on label and is not covered here.
Cumulative time out of the dry bag or dry cabinet, from the reel tracking log.
Time on the feeder, in the line queue and during placement, up to reflow.
Reserve for line stops and rework passes.
Your results
Floor life values follow the common J-STD-020 and J-STD-033 MSL table at 30 C and 60 %RH or below. Always follow the label on the bag and your controlled moisture procedure.
Floor life remaining vs planned exposure
Sweeps Planned additional exposure from 0 to 200, holding your other inputs fixed.
Reel-level floor life tracking from your ERP
Optional: review how lot and reel attributes in your ERP could drive floor life alerts.
Optional. The tool and every export work without this. No spam.
How to use it
Select the MSL printed on the moisture barrier bag. Enter hours already consumed from your out-of-bag log, then the extra time the lot will spend on feeders and in queue. The tool returns the remaining floor life, the percentage used and how long you can still run while keeping a reserve. If you set a shift plan that exceeds floor life, the overage and the number of reels at risk are highlighted.
- Start the clock when the bag is opened, not when the reel is loaded.
- Log every exposure interval; the clock is cumulative.
- Use the buffer field to cover line stops and second-side builds.
The MSL table behind it
MSL classes come from J-STD-020 and the handling rules from J-STD-033. At 30 C and 60 %RH or less the floor life is unlimited for MSL 1, one year for MSL 2, four weeks for MSL 2a, 168 hours for MSL 3, 72 hours for MSL 4, 48 hours for MSL 5, and 24 hours for MSL 5a. MSL 6 parts must be baked before use and reflowed within the time on the label. Higher humidity or temperature shortens the real exposure, so dry cabinets matter.
Reading the result
If 40 hours are used on an MSL 3 reel and the plan adds 36 hours, the total is 76 hours, 45 percent of the 168 hour floor life, leaving 92 hours. A negative remaining value means the lot must be baked or dried before reflow according to the procedure and the MSL-specific bake table. Do not guess a bake time here; use the J-STD-033 bake tables and the component manufacturer's data.
Common mistakes
The most common mistakes are resetting the clock without a proper bake, ignoring the time parts spend in kitting before the line, and treating all reels in a bag as one clock when they were opened at different times. Also note that long soak in a dry cabinet can pause or reduce the clock only if the cabinet meets the requirements in the standard. Barcode reel tracking and ERP lot attributes make this far easier than paper tags.
Frequently Asked Questions
What does MSL mean?
MSL is moisture sensitivity level, a classification from J-STD-020 that states how long a surface mount package can sit in factory conditions before it must be baked prior to reflow. Levels run from 1 to 6, with 1 the least sensitive.
When does the floor life clock start?
The clock starts when the moisture barrier bag is opened or the part is removed from dry storage and exposed to ambient factory conditions, and it accumulates until the part is re-dried or reflowed.
Can I reset the clock by putting parts back in a dry cabinet?
Only if the cabinet and the dwell time satisfy the requirements in J-STD-033. Otherwise bake per the standard tables. Check the component maker's guidance because some packages restrict bake temperatures.
Does this cover double-sided boards?
Add the time between the first reflow and the second reflow for parts that are exposed again, and compare the total with the floor life. Parts already soldered on side one are generally already reflowed once, so follow your process rules.
If you track floor life on paper tags or spreadsheets, Netray can discuss how to hold this data against your ERP lot and reel records, on your own servers.
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