Moisture Sensitivity Levels: Floor Life and Receiving Checks for ICs

Table of Contents

• Read the Exact Package Label Before Starting the Clock
• Inspect the Shipment Without Unnecessary Bag Opening
• Maintain a Cumulative Exposure Record
• Use a Hold Decision When the History Is Unknown
• Make the Logistics-to-Assembly Handoff Explicit

A reel can have the correct part number and still arrive with an unresolved moisture history. For plastic surface-mount ICs, receiving inspection therefore needs to establish more than quantity and appearance: which moisture sensitivity level applies, whether dry packaging remains intact, and what exposure has occurred before assembly.

The useful distinction is between shelf storage in controlled packaging and floor life after opening. Neither the purchase date nor the semiconductor date code tells an assembler how much permitted exposure remains. This guide concerns packaged ICs entering solder assembly; it does not assign a universal moisture level to bare die or other unrelated product forms.

Read the Exact Package Label Before Starting the Clock

Moisture sensitivity level, or MSL, describes handling limits associated with a component’s moisture and reflow classification. TI’s MSL and reflow application report explains the connection between package classification and floor life. Its reference table gives MSL 3 a 168-hour floor life at 30°C and 60% relative humidity. More severe conditions cannot be treated as equivalent exposure without an approved assessment.

Do not transfer that rating to every device with the same family name. Match the complete ordering code, package, label, and current manufacturer handling information. The peak reflow classification is also a separate constraint; an acceptable exposure record does not authorize any oven profile.

Keep three questions distinct:

• Is this the expected component and package?
• Has its moisture handling remained within the applicable limits?
• Is the intended assembly process qualified for this component and board?

That separation prevents a warehouse acceptance check from becoming an unsupported claim about solder-process suitability.

Inspect the Shipment Without Unnecessary Bag Opening

Receiving should preserve compliant manufacturer packaging wherever possible. Opening a bag simply to photograph every reel can create the very exposure that the inspection is supposed to control. Define which identity and condition checks can be completed from external labels and when an authorized opening is required.

Check	Record	Reason to stop and ask quality
Part identification	Manufacturer, complete ordering code, lot and quantity	Label conflicts with the purchase order or approved part
Moisture barrier bag	Seal condition, punctures, tears, and signs of repacking	Damaged seal or unexplained packaging change
Handling information	MSL, applicable packing information, and reflow classification	Missing, illegible, or inconsistent information
Prior opening	Opening history and supplied exposure record	Repacked material with no usable history
Handoff to storage	Location, time, responsible operator, and required conditions	Material cannot be placed in its approved storage state

When the bag is opened under the work instruction, inspect the humidity indicator card promptly and document the result according to the card’s instructions. Check the desiccant and packaging arrangement as required. A card is evidence about conditions inside the bag; it is not a retrospective stopwatch for all previous exposure.

This receiving record should connect to the organization’s component quality requirements and to any agreed inspection scope. Do not describe a visual inspection as verification of all moisture, authenticity, or electrical characteristics.

Maintain a Cumulative Exposure Record

The difficult cases are split reels, partial kits, returns from a feeder, and movement between an OEM and an EMS partner. Each handoff can break the history unless exposure travels with the material identifier.

For a simple illustration, assume an MSL 3 reel has a documented 168-hour allowance under the stated reference conditions. It spends 20 hours in kitting and 12 hours in a feeder. The recorded exposure is 32 hours, leaving 136 hours under the same approved assumptions. This arithmetic is an example of bookkeeping, not a correction method for higher humidity, uncertain storage, or a previous undocumented opening.

If the reel is split, each child container needs the parent lot identity and exposure already accumulated. A newly printed label must not create a fresh allowance. If two containers have different histories, merging them under one unrestricted stock record loses information.

Dry storage also needs defined rules. Whether a storage interval pauses exposure accumulation or contributes to drying depends on the applicable procedure and conditions. Operators should not decide that any cabinet labeled “dry” resets the clock. Record the cabinet or storage process used and retain the evidence required by the approved method.

Use a Hold Decision When the History Is Unknown

An unknown exposure history is not the same as a known limit exceedance. Both require controlled disposition, but the evidence and recovery options may differ. Isolate the material administratively or physically so that it cannot be consumed while someone searches for a missing record.

Ask the supplier for the original packing information, any opening and repacking records, and the handling procedure applied. Ask manufacturing engineering whether the planned assembly sequence creates additional constraints. If the answers remain incomplete, quality should decide the disposition; purchasing should not convert uncertainty into a pass because the build date is close.

TI’s AN-2029 handling guidance provides further context for moisture-sensitive packaging and handling. Use manufacturer instructions and the applicable controlled IPC/JEDEC procedure for the actual recovery process. A generic bake recipe is inappropriate: component construction, carrier materials, prior exposure, and board-level constraints can change what is permissible.

Repacking after an approved recovery step should include the resulting status and process record. It should not erase the fact that recovery occurred. That distinction matters when a downstream assembler must demonstrate how material was prepared.

Make the Logistics-to-Assembly Handoff Explicit

The semiconductor logistics qualification process should name who may open dry packaging during customs inspection, consolidation, or damage assessment. A logistics provider can preserve and record conditions, but should not invent engineering limits or authorize an unapproved recovery process.

A concise handoff record should answer: what material is moving, what handling state it is in, what exposure is documented, what restrictions remain, and who can authorize release. Use the same terminology at receiving, kitting, storage, and assembly.

The most effective moisture-control improvement is often a reliable record at each transfer. It lets the next operator decide whether the material can proceed, needs more evidence, or must remain on hold before it reaches reflow.