For most Surface Mount Devices (SMDs), moisture is a silent killer. During the reflow soldering process, if a component has absorbed moisture, the internal water vapor expands rapidly, causing package cracking or delamination, known in the industry as the "Popcorning Effect". Therefore, carrier tape packaging must strictly adhere to Moisture Sensitivity Level (MSL) standards.

1. What is Moisture Sensitivity Level (MSL)?

MSL is a standard established by JEDEC (Joint Electron Device Engineering Council) to classify the moisture sensitivity of non-hermetic SMD components. The higher the level, the more sensitive the component is to moisture, and the stricter the requirements.

Key MSL Levels

• Level 1: Not moisture sensitive; unlimited floor life at ambient conditions.
• Level 2 to Level 5a: Have varying degrees of moisture sensitivity; exposure time to the environment must be limited.
• Level 6: Extremely sensitive; must be baked before use and has a very short exposure time.

2. The Role of Carrier Tape in Moisture Protection

The sealing of Carrier Tape and Cover Tape is the first and most basic moisture barrier after components leave the factory. This process must be used in conjunction with Desiccants and Humidity Indicator Cards (HIC), sealed inside a Moisture Barrier Bag (MBB).

Key Functions of Carrier Tape

• Isolation Protection: Stable sealing of carrier and cover tape ensures each pocket forms a physically sealed space, preventing direct contact between components and external moisture.
• Peel Force Stability: High-quality carrier and cover tapes maintain stable Peel Strength even in humid environments, preventing seal failure due to adhesive moisture absorption, which could lead to component leakage.

3. The Complete Dry Packaging System

To ensure the safety of MSL components, carrier tape packaging must be a systematic process:

• Component Loading: Components must be loaded into carrier tapes under specified temperature and humidity conditions.
• Sealing: Optimal sealing conditions (temperature and pressure) must be used to ensure stable peel force and no gaps.
• Final Sealing: The carrier tape reel must be heat-sealed into a moisture barrier bag along with desiccant and HIC.
• Baking: If components have been exposed beyond their MSL floor life, they must undergo baking to remove absorbed moisture before reflow.

Ultimately, high-quality carrier tape and a strict packaging process are key guarantees for MSL components to survive transport and storage safely and avoid the popcorning effect during reflow.