Dry Storage of Electonic Components  [ Return towards  Electronic Components & Products  ]

Long-term storage
Storage is required for strategic or obsolete components (military, aerospace, medical, and automotive markets). Spare parts must be available for the entire lifetime of the final product. This period can be very long, especially in the aerospace / military or automotive industry. Storing these components in a dry, inert cabinet can eliminate the worries of moisture and oxidation damages over time. It also protects components from particulate, dust, or any physical shock.

Short-Term Storage

Moisture: The Enemy of Surface Mount-Devices
The introduction of surface mount devices (SMDs) has significantly contributed to the advancement of electronic assembly. However, moisture from atmospheric humidity can diffuse through the permeable plastic SMD package, and if the moisture level inside the package reach a critical point, the device may be damaged when exposed to high temperatures during the reflow process. These types of moisture-induced failures, also called ‘popcorning’, are of particular concern as they are often undetectable though greatly impacting product reliability. And with lead-free solders on the horizon and the higher reflow temperature they will command, moisture sensitivity issues will become more prominent.

Traditional Practices

PCB assemblers traditionally 'bake' or 'bake-and-bag' components that have exceeded their floor life as dictated by their IPC / JEDEC level. Baking, normally done for periods and temperatures varying from 24-hours at 125°C to 8-days at 40°C, removes the moisture absorbed from ambient humidity. While baking prevents moisture-induced failures and 'popcorning', it adds a non-value, timely and expensive step to the assembly process. Additionally, baking alters the component solderability, encourages growth of intermetallic layers, poses carrier compatibility, and creates bottleneck and logistic nightmares.

Dry Storage Option

Another option to reduce baking significantly is to adopt a moisture management system. This typically is comprised of a time tracking system and the use of dry cabinets. This is a pro-active step rather than a reactive approach (exposure to moisture and then bake). Experiments on the effectiveness of a dry gas (nitrogen) environment have proven that 1) it can prevent moisture absorption and 2) it can dry or dehumidify components that may have absorbed some moisture. For the practical application, the same storage atmosphere at ambient or near-ambient temperature is used to perform both tasks. Until IC manufacturers fabricate truly hermetic packages, the best and simplest way to eliminate moisture-induced failure and popcorning may reside in preventing moisture from being absorbed by the components.

Air or Nitrogen

By using nitrogen, a reliable, clean and dry gas source, solderability is preserved over time. In addition, nitrogen is cleaner than most filtered and dried air and is becoming the atmosphere of choice for electronic assembly facilities. When nitrogen is used for soldering processes, it makes sense to extend its use to the dry storage of components. In all cases, nitrogen should be considered for its combination of properties: low dew point, inertness, cleanliness and atmospheric consistency.