Moisture Sensitivity of Non-Hermetic Optoelectronic Surface Mount Devices

J-STD-033B baking schedules are no longer applicable to non-hermetic optoelectronic surface mount devices since conventional silica fillers are not employed. Critical to Moisture Sensitivity Levels (MSL) performance is the moisture concentration at the interior interfaces that are vulnerable to delamination and package cracking/popcorning during solder reflow. Moisture absorption and desorption has been adequately modeled using a 1-D model assuming a Fickian diffusion, the application of Henry´s Law and Arrhenius behavior of the diffusion process. Analytical moisture diffusion models for the saturated moisture gain, moisture absorption diffusivity, saturated moisture loss and moisture desorption diffusivity has been derived from experimental results. The derived analytical moisture diffusion models were used in determining the critical moisture concentration on the bottom center (die-pad) interface on each MSL. The application of moisture diffusion modeling was proven to be a viable method for analyzing the characteristics of the moisture absorption and desorption of surface mount devices (SMDs). This was used as the main tool in order to define the appropriate handling, storage and use for non-hermetic optoelectronic SMDs that will still meet J-STD-020C MSL requirements.