5.4 MSD Handling & Baking

Start/stop floor-life clocks, manage on-feeder exposure, bake ICs/PCBs safely, and reseal/reset right.

Moisture is a quiet failure mode in assembly: plastic-packaged ICs and even bare PCBs absorb humidity, then at reflow trapped steam expands and cracks packages (“popcorning”) or lifts pads. MSD (moisture-sensitive device) control hinges on the device’s MSL (Moisture Sensitivity Level, per J-STD-033/020) and a simple floor-life clock that starts the moment packaging is opened. That clock only truly pauses in an MBB (moisture barrier bag) with desiccant and a readable HIC (humidity indicator card), or inside a DRY-CAB (dry cabinet, ≤10% RH). Baking—at profiles safe for components or boards—drives out absorbed moisture and, when qualified, restores full floor life. The sections ahead align roles and checkpoints from receiving through rework so moisture becomes a managed variable, not a last-minute defect factory.

5.4.1 Terms you’ll see

MSL: Moisture Sensitivity Level per J-STD-033/020.
Floor life: Allowed time at ≤30 °C / 60 % RH after an MBB is opened.
MBB / HIC / Desiccant: Moisture barrier bag, humidity indicator card, and drying agent.
DRY-CAB: Dry cabinet (≤10 % RH, ≤5 % preferred) that pauses floor life.

5.4.2 MSL levels (1–6) — quick reference

(Floor life at ≤30 °C / 60 % RH; always defer to the device label/datasheet.)

MSL	Floor life	Typical parts	Handling notes (what changes for you)
1	Unlimited	Most resistors/caps, robust logic	Dry-pack not required by J-STD; still use ESD controls. Treat like non-MSD unless customer dictates otherwise.
2	1 year	Many SOIC/QFP, robust QFNs	Dry-pack for shipping; start timer at first open. Normal feeder/shift rules apply (5.4.6).
2a	4 weeks	Finer-pitch QFN/LGA, some small BGAs	Keep cabinets close to kitting to minimize ambient time. Label remaining hours clearly.
3	168 h (7 days)	BGAs, QFNs, CSPs, modules	Most common “real” MSD on the floor. Plan changeovers; avoid leaving reels mounted overnight. Pre-bake before hot-air rework (5.4.7/5.4.9).
4	72 h	Moisture-sensitive analog/PMICs	Treat like MSL3 but with tighter buffers. Prefer cabinet-parked feeders for any pause.
5	48 h	Very moisture-sensitive packages	Kitting issues only what you’ll place today. Expect more frequent reseal events.
5a	24 h	Ultra-sensitive fine-pitch/CSPs	Avoid night holds at ambient; cabinet-park between runs. Reseal promptly.
6	Bake + mount-within (per label)	Extreme cases	Mandatory bake before use; must be mounted within the labelled time after bake. No exceptions—plan takt accordingly.

Good to know

Floor-life pauses only in a sealed MBB or ≤10 % RH dry cabinet (5.4.5).
After a qualified bake (5.4.9), the device returns to full floor life for its MSL when resealed (DRY-PACK (RESET)).
MSL ≠ shelf life. MSL is moisture exposure after opening; chemical shelf life lives in 5.5.
Read the MSL triangle label and HIC on every open (5.4.4); if the HIC low-% spot is wet, treat as expired and follow 5.4.8.
For PCBs, apply the same logic when moisture-loaded (OSP especially); see PCB bake notes in 5.4.9.

5.4.3 Where things happen (area roles)

REC-STAGE / BULK-PARTS: Transit only; do not open MBBs here (5.2).
CMP-STORE (EPA): Open/inspect MBBs, read HICs, apply UID/line labels, DRY-CAB storage (5.1/5.2).
LINE-SMKT (EPA): Kitting/feeding; manage exposure; cabinet-park feeders for pauses (5.2).

5.4.4 Opening an MSD pack (start the clock right)

Prep in CMP-STORE: ESD on (5.3), UID ready (5.1).
Open MBB cleanly; immediately read HIC.
- OK: low-% spot still “dry” color → proceed.
- Caution: mid/high spots turned → proceed but note.
- Wet: low-% spot shows “wet” → treat as expired → go to Bake decision (5.4.8).
Start the floor-life timer in MES at the moment of opening; apply visible line label with remaining hours.
Unused remainder back to DRY-CAB or reseal (5.4.10).

5.4.5 What pauses vs runs the timer

Timer RUNS whenever parts are at ambient (benchtop, kitting table, mounted on feeders, carts).
Timer PAUSES only when either:
- The pack is sealed in an MBB, or
- The parts are fully inside a DRY-CAB ≤10 % RH.
  Zip bags and “covered boxes” don’t count unless your site has qualified them—assume no.

5.4.6 On-feeder exposure, shift hand-off, and changeovers

Mounted on a machine = timer runs.
Pausing across breaks or shifts: either cabinet-park the feeder+reel in a DRY-CAB with feeder slots, or reseal the reel and remove it.
Night holds: never leave MSDs mounted at ambient overnight.
Kitting discipline: issue shift demand + buffer; keep the rest sealed/dry.
Visual control: every reel/feeder shows remaining hours; supervisors verify at hand-off.

5.4.7 Rework & re-exposure (don’t popcorn at hot-air)

Assemblies before hot-air/BGA/QFN work: if they’ve seen ≥1 day ambient or suspect humidity, pre-bake the assembled PCB (5.4.9) to avoid popcorning/pad lift.
Salvaged MSDs: unless kept dry from first opening, treat as expired; default is scrap or tray-rebake if device and tracking allow.
Cumulative exposure: add rework exposure to the device’s timer; if it exceeds floor life, bake then reseal/reset before reuse.

5.4.8 Bake decision (simple rule)

Bake if any of these are true:

Floor life expired or will expire before next use.
HIC low spot wet on opening.
Evidence of compromised storage (torn MBB, humidity excursion, unknown history).
Pre-rework bake required as above.

Otherwise, continue with timer rules.

5.4.9 Bake profiles (ICs vs PCBs; pick the safest that works)

Always check the device/packaging ratings. Some carrier tapes, labels, or elastomers can’t take heat.

ICs / components

Preferred (in trays/tubes): 125 °C dry bake; duration per site table (typ. 24 h for MSL3+; longer for higher MSL).
If still in tape-and-reel:
- Many tapes soften at 60–90 °C. Choose low-temp/long-time (40–60 °C, ≤5 % RH, extended hours), or re-tray parts suitable for 125 °C and bake.
MSL6: follow label exactly (mandatory bake and mount-within time).

PCBs (bare or assembled)

General FR-4: 105–125 °C, 2–8 h based on thickness/storage history.
OSP finish: prefer lower temp, longer time (e.g., 105 °C) to protect finish.
Assembled boards for rework: ~105 °C for 4–8 h; mask or remove heat-sensitive labels, elastomers, bezels.
Heavy copper/thick boards: choose longer times.

After bake

Cool to ≤30 °C in dry conditions before reseal or immediate use; don’t open-air cool in humid rooms.

5.4.10 Reseal & reset (MBB done right)

Bag: Use qualified MBB sized for minimal free volume; no pinholes.
Desiccant: Fresh, in-date; mass matched to free volume per site table; distribute evenly.
HIC: New card placed on top, visible at next open.
Purge (optional): Short dry N₂ purge; don’t crush sharp edges.
Seal: Straight, 10–12 mm heat seal; wrinkle-free; quick squeeze test for leaks.
Label (outside): PN, lot/date, MSL, state (DRY-PACK (RESET) or REMAINING x h), open time, reseal time, remaining time if not baked, operator/workstation.
Reset logic:
- After a qualified bake → timer resets to full floor life.
  Reseal without bake → timer stays at remaining hours.

5.4.11 Data & traceability links

Every reel/tray/tube has a UID (5.1) bound to MSL, timer state, bake/ reseal events, and feeder IDs while mounted.
Rework tickets carry added exposure and any pre-bake performed.
Pack labels mirror the MES state—so operators don’t guess.

5.4.12 Acceptance cues (fast table)

Area	Accept	Reject
HIC at open	Low-% spot dry	Low-% spot wet → Bake
Timer control	MES timer matches label; pauses only in MBB/DRY-CAB	Handwritten guesses; timer “paused” in zip bag
Feeder pauses	Feeder+reel cabinet-parked or reel resealed	Mounted overnight at ambient
Bake profile	Matches device/medium; safe temps	125 °C with tape; OSP baked too hot
Reseal	Fresh HIC + desiccant; straight seal; full label	Missing HIC; no desiccant; unlabeled
Reset	“RESET” only after qualified bake	Timer reset without bake

5.4.13 Common traps → smallest reliable fix

Trap	Symptom	First move
“We’ll finish tomorrow” on feeder	Popcorning, HiP, delam	Cabinet-park or reseal; add shift hand-off check
Baking tape at 125 °C	Warped tape, loose pockets	Low-temp/long-time or re-tray
Zip bags used as dry pack	HIC wet on next open	Only MBB or DRY-CAB pauses the clock
Rework without pre-bake	Cracked packages at hot-air	Pre-bake assemblies before rework
OSP boards baked hot	Poor wetting in next run	Bake lower/longer for OSP
No reseal label	Timers reset by rumor	Label state + times + remaining h; update MES

5.4.14 Pocket checklists

Open & stage (CMP-STORE)

ESD on; open MBB; read HIC
Start MES timer; apply remaining-hours label
Remainders to DRY-CAB or reseal

On the line

Issue shift demand + buffer; cover reels
Pauses: cabinet-park feeder or reseal
Supervisor verifies remaining hours at hand-off

Bake & reseal

Profile matches device & medium
Cool dry; fresh desiccant + HIC; straight seal
Label with state/times; reset only if baked; MES updated

Rework

Pre-bake assemblies if ambient-exposed
Salvaged MSDs handled per policy (rebake/scrap)
Added exposure logged on ticket

Bottom line: moisture is a timer with rules. Start it when you open, pause it only when truly dry, pre-bake before hot ops, reseal/reset with full labeling. Do that, and reflow-side gremlins—popcorning, delam, voids/blowholes—fade into rare stories, not daily work.