Moisture Resistance

Moisture Resistance



Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices.

The advent of surface mount devices (SMDs) introduced a new class of quality and reliability concerns regarding package damage ”cracks and delamination” from the solder reflow process. This document describes the standardized Moisture Sensitivity Levels (MSL) of floor life exposure for moisture/reflow-sensitive SMD packages along with the handling, packing and shipping requirements necessary to avoid moisture/reflow-related failures. Companion documents J-STD-020D.1 and JEP113 define the classification procedure and the labeling requirements, respectively.

Moisture from atmospheric humidity enters permeable packaging materials by diffusion. Assembly processes used to solder SMD packages to printed circuit boards (PCBs) expose the entire package body to temperatures higher than 200°C. During solder reflow, the combination of rapid moisture expansion, materials mismatch, and material interface degradation can result in package cracking and/or delamination of critical interfaces within the package.

The solder reflow processes of concern are convection, convection/IR, infrared (IR), vapor phase (VPR) and hot air rework tools. The use of assembly processes that immerse the component body in molten solder are not recommended for most SMD packages.

This JEDEC testing identifies the classification level of non hermetic solid-state surface mount devices (SMDs) that are sensitive to moisture-induced stress. It is used to determine what classification level should be used for initial reliability qualification. Once identified, the SMDs can be properly packaged, stored and handled to avoid subsequent thermal and mechanical damage during the assembly solder reflow attachment and/or repair operation. This D revision now covers components to be processed at higher temperatures for lead-free assembly.

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