In this guide 6 sections
Moisture sensitive parts start a clock the moment the dry bag opens. Without a record of open time, bake cycles and date codes, nobody knows which reels are still safe. The result is cracked packages, poor solder joints and whole lots scrapped after reflow.
What the clock on a reel actually is
Plastic packages absorb moisture from the air. Reflow heat turns that water to steam, and the package can crack or delaminate. This is the popcorn effect. It often hides inside the part.
Each moisture sensitive part carries an MSL rating on its dry bag label. The rating sets its floor life, which is the time it may sit in shop air before it needs baking. A humidity indicator card in the bag shows whether the contents stayed dry in transit.
Date codes run a second clock. It is slower, but real. Solderability fades with age, so a reel can be dry and still too old to wet properly.
- MSL rating and floor life from the bag label
- Bag seal date and humidity card reading
- Time out of the bag, summed across every exposure
- Date code and shelf life from the supplier
How missing records become defects
A reel is loaded on Monday, pulled off Tuesday and put on a shelf. On Thursday another shift loads it again. Nobody wrote down the first exposure, so the second run starts a fresh clock in everyone’s head.
The boards reflow fine. Weeks later a customer reports intermittent faults, and an X-ray shows internal cracks. Now the question is which lot, which boards, which reel. Nobody can say. There is no log. Without a log, the answer is everything built that month.
Poor wetting from old parts looks different. You see dull joints, tombstoning or open pads, and rework piles up at inspection without an obvious cause.
Track exposure from the first opening
Put a label on every opened reel with the date and time of opening, the floor life allowed and the running total used. Stores writes it. The line adds to it each time the reel returns. Keep it legible.
Dry cabinets pause the clock only when the cabinet holds the right humidity. Log the time in and out of the cabinet, and check the cabinet’s own reading at a set point each shift.
Scan the reel code at issue, at load and at return. Three scans give you the exposure total without anyone doing arithmetic on a clipboard.
- Open time, floor life allowed, time used so far
- Cabinet in and out times with humidity reading
- Operator and machine feeder at each load
- Return scan with remaining floor life
Bake records that stand up to a question
Baking resets floor life only when done to the right profile for the package thickness and the part’s own datasheet. A bake with no record is as good as no bake.
Log the oven, the temperature set, the start and end time and the operator. Note how many bakes a reel has already had, since repeated baking harms terminations and tape.
When the reel comes out, label it with the new floor life start. Reels that have used up their bake allowance go to quarantine. Never back to the shelf.
Run a weekly expiry sweep
Once a week, list every reel by date code and open status. Sort by oldest first. Flag anything past its shelf life and anything opened and idle beyond its floor life.
Send flagged reels for bake, supplier query or scrap, and record the choice. A short list reviewed every Friday costs far less than a lot scrapped after reflow.
Start by walking the dry cabinet today and counting reels with no label. That number is your gap. Count them.
Moisture sensitive reel log
The log fits one page and gives every opened reel its own line. Columns hold part number, supplier lot, date code and MSL rating. Others hold bag open time, floor life allowed, each exposure in and out and the running total. The last ones hold bake date, oven, bakes used and disposition. A weekly sweep box at the bottom lists reels near expiry or floor life limit.
Open a blank worksheet to printQuestions owners ask
Does every part on the BOM need this tracking?
No. Only moisture sensitive devices need floor life tracking, usually larger ICs, BGAs and some modules. Date codes matter for all parts with limited shelf life.
Can we bake a reel as many times as we like?
No. Repeated baking can harm the tape, the reel and component terminations. Check the part datasheet and count bakes on the reel label.
How do we know a bag stayed dry?
Read the humidity indicator card inside the bag when you open it. If the card shows the limit exceeded, treat the contents as exposed and bake before use.
What happens to parts past their date code?
Ask the supplier about solderability testing or return. Otherwise quarantine them with a clear tag and record the decision.