Application Note: Why Choose Desiccator Storage?

Once absorbed by sensitive components, water creates a number of potentially disastrous conditions. Even minute traces of oxidation, the most notorious result of moisture exposure, can degrade soldering and other manufacturing processes. Because water dissolves ionic contaminants, it also alters the conductivity of the material, which in turn can degrade electrical function. Water also combines with other materials, causing harmful chemical reactions that degrade pharmaceutical samples and chemical mixtures.

Although the vast majority of integrated circuits are packaged in plastic encapsulants (because they are cheaper than ceramic ones), manufacturers are often unaware of the consequences of using hygroscopic materials in a solder reflow process. Moisture absorbed into the package vaporizes during the rapid heating and generates pressure along the metal-to-plastic contact regions. Differences between the coefficients of thermal expansion of the two materials can cause loss of adhesion, swelling, and cracking. An audible "pop" signals the problem, and testing confirms a deterioration of electrical function.

Desiccant-based dry storage avoids some of these drawbacks, but introduces others. These systems remove moisture from an incoming supply line of air (or other process gas) and often feature dual-tower designs that perform on-line drying and off-line regeneration simultaneously for continuous operation. Such systems can be effective, but they require heating/drying components that may not be reliable. Further, they must be closely monitored to ensure that incoming gas flow remains below a critical humidity threshold. Their complexity and high operating costs makes them prohibitively expensive for long-term storage applications.