Why Moisture-Sensitive Devices Need Dry-Packing
Plastic-encapsulated semiconductors and many surface-mount components are hygroscopic: their moulding compound absorbs water vapour from the air. During reflow soldering the whole package is heated to 245–260°C in seconds, and any absorbed moisture flash-vaporises. The internal steam pressure delaminates the package or cracks it audibly, the “popcorn effect”, and the part fails immediately or, worse, latently in the field. To prevent this, components are assigned a Moisture Sensitivity Level (MSL 1 to 6) and, for MSL 2 to 6, dry-packed in a sealed moisture barrier bag (MBB) with desiccant and a humidity indicator card, with a defined floor life once the bag is opened.
The desiccant in that bag has a non-negotiable requirement that catches out cheaper products: it must be chemically inert toward the bare metal and the boards it sits beside. Many desiccants use nitrogen-based anti-caking additives; in a sealed bag those nitrites can drive electrochemical corrosion on copper traces and leads, and dimethylfumarate (DMF) anti-mould agents are banned in the EU and stain electronics. BENZPACK C DRY activated clay is certified nitrite-free and DMF-free, stays solid when saturated (no dust, no liquid), and is compliant with MIL-D-3464E and J-STD-033C, which is exactly why it is specified for direct use against PCBs, semiconductors and connectors.