PCB designers will typically find they start to accumulate a lot of components over time. These can come from past prototyping or production runs, after which excess components might be shipped back to the designer from the assembly facility. These can also come from side projects, where a designer hand-assembled components onto a board. In either case, there will be some components left over that might be held for reuse in a later production run.
If you’re planning to hold onto your old components and reuse them in new projects, how should they be stored? Some components will be perfectly fine stored in a plastic bag, while others are sensitive to moisture and should be stored in a controlled environment or special packaging. This guide will provide an overview of acceptable environments for storing components, as well as some of the packaging materials that are acceptable for component storage.
Electronic Component Storage Conditions
Just like storage of most other items or chemicals in an industrial setting, there are three factors that need to be controlled in long-term component storage:
- Prevention of ESD
- Exposure to noxious substances
The last point is relatively simple to deal with as it requires storing components away from a production environment where chemicals may be present. The other points involve packaging and controlling the environment in the storage area. There are also standards on storage and handling of electronic components.
Storage and Handling Standards
Not surprisingly, the component industry has developed standards addressing safe handling and storage of electronic components, particularly those that may be sensitive to moisture exposure during or after reflow:
- JEDEC J-STD-033C - Standard for Handling, Packaging, Shipping, and Use of Moisture/Reflow Sensitive Surface-Mount Devices
- JEDEC J-STD-020C - Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices
These two standards are intended to address any factors that may impact solderability of a device after long term storage. Such factors could include exposure to any atmospheric contaminants, as well as maintaining consistent humidity and temperature in the storage environment.
Ideal Storage Environment
In terms of temperature and humidity, the ideal storage environment for moisture-sensitive components is no greater than 60% relative humidity at 30 °C. Typical lab conditions off the production floor, such as in an office building, are typically sufficient to protect components from extreme temperatures and humidity. In some regions, where humidity may be regularly higher than this level, the components should be kept in a dry box, or in vacuum-sealed packaging. There are also storage materials that can be used to protect components.
How to Protect Stored Components
If you have to store components long-term, they should generally not be left out on the shelf in open air, even if the humidity and temperature conditions are appropriate. If you’re unsure as to the required storage conditions for specific components, check your component datasheets for appropriate packaging and environmental conditions.
Plastic bags - These are appropriate for most passives and moisture/ESD insensitive components. The bags that are appropriate for these components are non-triboelectric, meaning they tend to not accumulate static charge that would lead to ESD.
Plastic bags for storing electronic components.
ESD protective bags - For ESD protection, there are conductive bags that can be used to store components. These bags can withstand a moderate ESD pulse that might otherwise harm a component. These bags can also be used to store or ship completed assemblies to customers.
ESD shielding bag for storing electronic components.
Desiccants - A simple silicone desiccant is a low-cost material that can be used to absorb moisture in the event humidity in the surrounding environment becomes high. Dessicants can be placed inside plastic bags or ESD bags to provide targeted protection from humidity.
Vacuum seal bags - A simple solution to prevent moisture ingress is to vacuum seal components, typically with desiccant placed in the storage packaging. There are vacuum-sealable ESD protective bags for ESD-sensitive components.
Finally, if you really want to make sure your components will be safe, use the same packaging materials that were supplied by the manufacturer. One common example is for BGA packages on organic substrates; if these are purchased directly from a manufacturer, they could be vacuum sealed in an ESD protective bag and packaged with desiccant. This type of packaging and storage at appropriate temperature will protect against the three main component degradation factors of ESD, moisture, and high temperature.
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