Best Practices for Long-Term Storage of Electronic Parts

Whether you manage inventory for high-volume production runs, or you’re just saving small batches of components for a rainy day, components should be packed and stored correctly. The goal in component storage is simple: prevent environmental contamination so that the parts can be used in assembly at a later date. If packaged correctly, even the most sensitive components can be kept in storage for significant amounts of time. In this article, we’ll look at some of the best practices for keeping components in storage.

Before going further, note that there are two standards outlining handling, packaging, and long-term storage requirements for electronic components:

• JEDEC J-STD-020C - Moisture/Reflow Sensitivity Classification for Nonhermetic Solid State Surface Mount Devices
• JEDEC J-STD-033C - Standard for Handling, Packaging, Shipping, and Use of Moisture/Reflow Sensitive Surface-Mount Devices

These standards address handling and storage of any electronic components that could become damaged from moisture during or after reflow.

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Start With Packaging Materials

To ensure safe storage and longevity of components, the components should be packaged correctly. There is a short list of packaging materials that is needed:

• Plastic bags
• Antistatic bags to protect against ESD
• Silicone desiccant pouches
• Moisture indicator strips
• ESD warning stickers
• Antistatic tape roll
• Antistatic bubble wrap

Antistatic ESD-safe bags are probably the most common packaging material used to ship and store electronics, especially integrated circuits. If a component is sensitive to ESD, then it should be shipped and stored in a sealed antistatic bag. Antistatic bags have varying levels of moisture resistance, and they may admit moisture even when properly sealed. These bags, as well as other packing materials, can be purchased online from industrial/commercial suppliers.

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How Should Storage Materials Be Packed?

Simpler components that are not ESD or moisture sensitive can typically be placed in plastic bags or in general-purpose antistatic bags. Other components could have particular sensitivity to moisture, corrosive substances, or moderate temperature excursions. Materials should be packed properly while considering these environmental factors. If you’re not sure about a particular component, the datasheet will typically provide guidance on long-term storage.

Discrete semiconductors and integrated circuits are typically stored in antistatic bags. These come in different varieties, with different ESD/voltage ratings and sealing capabilities. Some antistatic bags are moisture-safe and vacuum-sealable, and many components are shipped from semiconductor manufacturers or distributors in vacuum-sealed ESD/moisture-safe packaging. These packages might also include a desiccant pouch and a moisture indicator.

If you receive leftover components from a production run, or you’re holding inventory for an upcoming board spin, your best bet is to package components just as they were packaged when shipped from the vendor. For example, many integrated circuits will be placed on a tray, enclosed in a vacuum-sealable bag, and with a moisture indicator and desiccant present in the packaging. This type of packaging is safe for both shipping and long-term storage.

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This final point should be obvious, but it can be easy to overlook. Make sure your packed components are clearly labeled with part numbers and the date they were packed for storage. In cases where components are kitted for a particular assembly, include some other identifier on the kit, such as an assembly number and the most recent revision. If a part is inadvertently stored longer than its rated useful lifetime, proper labeling will ensure the part is flagged before being placed in an assembly.

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Storage Environment

What is a typical storage environment for components? The ideal environment for electronic component storage should protect components from the following environmental factors:

• High humidity
• Extreme temperatures
• Aerosols
• Oxidizing gasses
• Outgassing from solvents

Typically, a safe storage environment for properly packaged components is an air-conditioned office environment. It is not a good idea to store components near outgassing solvents or sources of oxidizing gasses, even if the components are packed and sealed.

The ideal environment for storing moisture-sensitive components is less than 60% relative humidity at room temperature. These are the types of conditions that would be found in an office or lab environment. If there is excess humidity, or storage on the production floor is essential, then components should be kept in vacuum-sealed packaging or in an environmentally-controlled chamber.

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Inspection Before Assembly

Once shipped components are received or pulled from internal storage, it’s important to inspect them before use in a new assembly. Inspection does not need to rise to the level of chemical testing or X-ray inspection; typically visual inspection for corrosion or physical damage is sufficient. This is one reason indicator strips are so useful for ensuring components have been packaged and stored properly.

Components that have experienced some level of environmental contamination may require cleaning or baking before use placement in an assembly. Baking should be performed carefully, especially when working with ICs packaged in plastic casing on organic substrates; these components are hygroscopic and will retain excessive moisture. Typical reflow profiles can cause these components to exhibit the “popcorn effect,” where the substrate starts bubbling and delaminating.

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