- All
- Product Name
- Product Keyword
- Product Model
- Product Summary
- Product Description
- Multi Field Search
Author: Site Editor Publish Time: 11-18-2025 Origin: Site
Moisture Sensitivity Level (MSL) is an industry classification that defines how susceptible a plastic-encapsulated SMD component is to moisture-induced damage during reflow. Most SMD packages—especially ICs—are built with epoxy mold compound, lead frames, die attach compounds, and internal interfaces where moisture can accumulate. When these components are exposed to ambient humidity, water vapor slowly diffuses through the mold compound into internal layers.
During reflow soldering, where temperatures commonly reach 230–260°C, absorbed moisture turns into high-pressure vapor. This sudden expansion can create physical stress inside the component package. MSL
exists to quantify how long a component can remain outside dry storage conditions before moisture uptake becomes critical.
MSL categories are standardized across the industry. They help manufacturers, EMS providers, and assembly technicians determine how long a component can be safely exposed to ambient conditions, how it should be stored, and whether it requires baking before reflow. Proper MSL control ensures component reliability, improves yield, and prevents catastrophic failures such as popcorning or delamination.
Moisture ingress is a slow but continuous process. Even when packages look perfectly sealed, their epoxy materials are naturally permeable to water vapor. Several failure mechanisms arise from moisture exposure:
Atmospheric moisture gradually enters the plastic encapsulation through diffusion. The rate depends on humidity, temperature, and package thickness. Smaller packages tend to saturate faster because they have thinner mold compounds and larger surface-to-volume ratios.
When moisture-laden components enter the reflow oven, the temperature spike causes the absorbed water to vaporize instantly. This creates internal pressure strong enough to deform the structure.
Moisture-induced failures can appear in multiple forms:
Popcorning: A rapid “explosion” inside the package causing cracking or package rupture.
Delamination: Layers inside the component separate (die paddle, lead frame, die attach).
Microcracks: Small but dangerous cracks that cause intermittent connections or latent failures.
Die Damage: Excessive pressure can stress or fracture the silicon die.
Poor Solderability: Microcracks can affect solder wetting and joint reliability.
Such defects may not always show during production, but they often lead to warranty returns, intermittent field failures, and costly rework.
JEDEC classifies moisture sensitivity from MSL 1 to MSL 6, where MSL 1 is the least sensitive (no dry storage required) and MSL 6 is the most sensitive (must be reflowed immediately after opening).
Here is a summary:
Table 1: JEDEC Moisture Sensitivity Levels and Floor Life
MSL Level | Floor Life at 30°C/60% RH | Description |
MSL 1 | Unlimited | No moisture restrictions |
MSL 2 | 1 year | Low sensitivity |
MSL 2A | 4 weeks | Moderate sensitivity |
MSL 3 | 168 hours (7 days) | Common for many ICs |
MSL 4 | 72 hours | High sensitivity |
MSL 5 | 48 hours | Very high sensitivity |
MSL 5A | 24 hours | Extremely sensitive |
MSL 6 | 0 hours (must reflow immediately after opening) | Highest sensitivity |
Floor life represents how long an IC can remain outside dry packaging at standard factory conditions (≤30°C, ≤60% RH). After this period, the component may absorb excessive moisture and become unsafe for reflow.
Exposure time must be strictly tracked using floor-life labels or digital logging systems. If exposure exceeds allowable floor life, the components must be baked to remove moisture before reflow.
Accurate moisture assessment is critical for predicting component behavior during reflow.
Cracked components
Bulged or warped mold casing
Solder balls trapped under component edges
Lifted or damaged leads
These visible issues often indicate popcorning or delamination.
X-ray equipment helps detect internal voids or cracks. It is commonly used for BGAs, QFNs, and CSPs where visual inspection is insufficient.
C-mode scanning acoustic microscopy can detect delamination between mold compound and die paddle. This is the industry’s most accurate method for moisture-induced failure detection.
Some semiconductor manufacturers use weight-gain measurement and diffusion modeling to determine moisture absorption rates.
Component suppliers test MSL during reliability qualifications using:
Moisture soak
Preconditioning
Reflow simulation
Temperature cycling
This ensures MSL rating accuracy before components reach your production line.
MSL components are shipped in moisture barrier bags that contain:
Desiccant packs to absorb moisture
Humidity Indicator Cards (HICs) to show exposure
Sealed aluminum barrier layer to protect components
A humidity indicator turning pink indicates moisture exposure, signaling a need for baking or replacement of desiccant.
Opened reels, trays, and tubes should be placed in:
Dry Cabinets (≤5% RH)
Nitrogen Storage Cabinets
Vacuum-sealed bags
These storage methods greatly slow moisture ingress and extend floor life.
Accurate MSL tracking prevents moisture-related failures. Techniques include:
Floor-life labels on each reel
Exposure timers for operators
Software-based MSL control in MES/ERP
Automated dry cabinets with digital logs
Keeping precise exposure records is essential for meeting high reliability requirements, especially in automotive, aerospace, and medical product manufacturing.
Baking removes absorbed moisture by heating components gently at controlled temperatures.
Why Baking Is Necessary
When floor life expires, baking resets the component’s moisture level. Without baking, reflow leads to internal pressure spikes and package failures.
Typical Baking Parameters
125°C for 24 hours (common for MSL 3–5A components)
40–90°C for plastic carrier materials sensitive to high heat
Table 2: Typical Baking Time for MSL Components
MSL Level | Bake Temperature | Bake Duration |
MSL 2A–3 | 125°C | 24 hours |
MSL 4–5A | 125°C | 48 hours |
MSL 6 | Must reflow immediately; baking only before re-pack |
Risks of Over-Baking
Excessive or repeated baking can:
Oxidize component leads
Degrade solderability
Damage packaging materials
Cause reeled components to warp
Therefore, baking must be controlled, timed, and logged.
Moisture-damaged components can cause:
Popcorning—visible cracks or explosive failure in the package
Mold compound delamination
Solder joint inconsistencies
Tombstoning or lifted leads due to warping
Each of these defects creates immediate yield loss.
Even if components pass initial AOI and in-circuit testing, moisture-induced microcracks can evolve into field failures. Although these latent faults are hard to find, they can be quite expensive in the long run.
Applications especially at risk include:
Automotive ECUs
Industrial power modules
Telecom equipment
Medical electronics
Aerospace systems
Poor MSL control can shorten product lifespan dramatically.
MSL-related failures impact many cost areas:
Scrap cost from damaged components
Rework labor and process interruptions
Customer returns and warranty replacements
Extra inspection time
Quality reporting overhead
Once MSL-related issues appear, they often multiply quickly across thousands of boards, affecting production output and customer confidence.
Create a dedicated MSL inspection checklist:
Check MBB integrity
Verify desiccant status
Confirm humidity indicator color
Review manufacturer’s MSL labeling
Open MBBs only when components are needed
Avoid leaving reels at operators’ workbenches for long periods
Use dry boxes between placement jobs
Modern smart factories use:
RFID-based exposure tracking
Smart dry cabinets with automatic logs
Real-time alerts to prevent floor-life violations
Operator mistakes—such as leaving reels exposed overnight—are among the most common causes of moisture-related failures. Regular training reduces errors significantly.
A stable, well-characterized reflow temperature profile reduces internal stress on moisture-sensitive packages. Avoid sudden temperature spikes and maintain controlled preheat stages.
As factories adopt more automation, MSL management is becoming integrated into smart production systems.
Software systems can track:
Component floor life
Exposure time per reel
Re-baking history
Incoming lot data
Automated MSL management guarantees complete traceability and removes human mistake.
Advanced dry cabinets record:
Humidity levels
Door open/close events
Component identification via barcode/RFID
These features ensure MSL compliance without manual paperwork.
Production managers can monitor:
Components near floor-life expiration
Required baking actions
Reflow-ready status for all reels
This prevents last-minute quality failures on the production floor.
A mid-size EMS manufacturer left MSL 3 IC reels exposed overnight. The next day, wave cracks and delamination caused a 15% yield drop. After adopting dry cabinet usage and adding MSL timers, the issue disappeared entirely.
An automotive electronics producer implemented RFID-based MSL tracking for BGA components. Within two months, the defect rate dropped by 40%, and reflow-related failures became negligible.
A factory used excessive baking for safety. However, this caused oxidation and poor solderability. After adopting the correct baking schedule, they reduced defects and saved nearly 20% on component cost.
ABOUT US | CONTACT US | FAQS
English