The storage of moisture sensitive (electronic) components and materials are problematic.
Manufacturers with Long term Storage Requirements face additional obstacles.
Due to rapid changes in packaging design, material and a very high demand for electronic components (consequently a shortage of semiconductors in all industries), companies find themselves forced to purchase additional quantities of components in order to guard against the impact of component obsolescence on their final product designs. This in turn creates an issue of long term inventory storage.
Product lifecycles have become very short with new models being released sooner than ever before. However, many manufacturers in industries including automobiles, aviation and avionics, military and railway must guarantee the availability of replacement parts including PCBs for ten or even twenty years. This demands the advance purchase and extended storage of components and materials. Further complicating the problem is that most components cannot be stored for more than a few years without very special handling procedures.
After long-term storage, components and circuit boards are often no longer solderable, due to oxidation caused by the oxygen of the air (oxidant) and the humidity (electrolyte). However, if the humidity, which forms an invisible water film of few atomic layers on the surfaces, is lowered below 5% RH, this corrosion process is stopped. At the same time, other negative effects due to moisture absorption are also avoided.
Intermetallic compounds form when two unlike metals diffuse into one another creating species materials which are combinations of the two materials. Intermetallic growth is the result of the diffusion of one material into another via crystal vacancies made available by defects, contamination, impurities, grain boundaries and mechanical stress. There are a number of locations within the electronic package where these dissimilar metals are joined. These include die level interconnects and wire bonds, plating finishes on lead frames, solder joints, flip chip interconnects, etc. Growth of intermetallics during the storage period can occur and reduce the strength.
Intermetallic growth rate is strongly temperature-dependent and doubles for each 10°C temperature increase.
This aging process can be slowed by appropriate cooling. However, the risk of whisker formation of tin alloys increases with decreasing temperature. Studies and practice have shown that a storage temperature of 13-14°C is optimal.
The XSDC-1412-55 cabinet from Totech Europe will help you avoid risks as mentioned above.
Find out more about the XSDC long term storage Dry Cabinets.
