Component Encapsulation
Protective packaging of electronic components using molded resin provides mechanical support and environmental isolation for semiconductor dies intended for automated surface mount assembly. This type of component, known as a plastic surface mount device, is widely utilized due to its low weight and cost-effectiveness. It must withstand the thermal stresses of the reflow oven during soldering.
Moisture Sensitivity
The polymer materials used to seal these devices are semi-porous and naturally absorb ambient humidity from the factory floor over time. Within a plastic surface mount device, trapped moisture poses a major risk because it expands rapidly during the high-temperature reflow cycle. Component manufacturers classify these parts according to standardized moisture sensitivity levels to define their allowable exposure times.
Reflow Durability
Vaporization of absorbed water creates high internal pressure that can lead to delamination, internal wire breakage, or a destructive rupture of the molded casing. To prevent this cracking, any plastic surface mount device that has exceeded its floor-life limit must undergo a baking cycle to drive out the moisture before it passes through the reflow oven. Assemblers store these components in dry cabinets or sealed moisture-barrier bags with desiccant cards to ensure they remain dry.
Following these handling guidelines prevents thermal stress failures during high-volume assembly runs.
