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Frequently Asked Questions about Long Term Storage of Semiconductors, IC wafer and die product


At Force Technologies, we have recently invested heavily in storage facilities. As part of this move, we want to help you understand everything there is to know about the cabinets and the type of product that can be stored in them. Storing these high-value components for extended periods is a complex issue due to the relatively short history of semiconductor technology and the ongoing advancements in materials and manufacturing processes. Over the past 50-60 years, industry guidelines have emerged based on research and practical experience, suggesting that semiconductors can be reliably stored for 15 to 20 years under optimal conditions.

These guidelines typically recommend sealing products in moisture barrier bags and storing them in stable, low-humidity environments, often purged with inert gases like nitrogen. Despite these best practices, continuous research and periodic testing are crucial to ensure the integrity and functionality of stored products. Here, we address some of the most common questions about the long-term storage of these critical components.

How long can you actually store product?

This is a very complicated question because semiconductors have only been around for 50-60 years and in very high volume for less than that. Over that time-period certain industry guidelines have appeared backed by studies and research on how long microelectronics in their various forms can survive, be it plastic encapsulated, hermetic ceramic or even raw wafer form.

Unfortunately, there is no hard and fast definitive answer as semiconductor materials are constantly changing especially due to the very high-volume productions we see today. On top of this there has not been enough time elapsed to gather sufficient data on all package/material types. That said with the data we have so far, 15 to 20 years is a very stable amount of time a product can be stored for without any degradation.

Most guidelines call for product to be sealed in a moisture barrier bag (MBB) or similar and then kept in a clean, low humidity, stable temperature cabinet ideally purged with a inert gas such as nitrogen. This prevents any intermetallic growths, corrosion etc on any areas of concern be that the die itself or any metalised areas externally/internally on the assembled package.
Research is constantly evolving as time passes but at the moment these are certainly safe conditions for at least 15 to 20 years.

Do we take the product out and sample it periodically?

Yes, we regularly take products out and ensure it is both visually compliant and electrically functional. Time frame is a major factor in how often you decide to set periodic sampling as is the criticality of the system the parts are going into. For example if you are building product out from the stock every 6 months the inline qualification and monitoring will confirm the product is suitable for use for a low criticality system.

If it is a 10-year time frame for instance before your next build and the application is critical it is very wise to be doing regular periodic monitoring. This can involve functional electrical testing, detailed visual inspection and even DPA (Destructive physical analysis) to confirm the internals of the component have not suffered during the storage period. All characteristics are confirmed against datasheet specifications to ensure product is identical to when entered storage.

How normal is it for the characteristics of the wafer/devices to change?

This is somewhat dependant on the quality the OEM builds out to. If the OEM in question has rigorous and stringent QA monitoring through their processing, the resulting product should have no meaningful deviation over 15-20 years. With the high quality of production these days it rarely happens however if die has been stored incorrectly it is a risk and should be reviewed before use in production. We traditionally agree on a programme of testing with clients that might include for 10 – 15 year storage, testing every 2-5 years for example but each project/part is different and must be assessed in isolation.

What backup data do you have on your storage?

As part of our AS9100 we have all the reports and logs from every day that the product has been in storage. This ensures the product has remained within industry guidelines and can be proved out to our customer base.

What type of chips can we store?

In terms of packaged chips we can store literally everything. It is generally more cost effective to store product in die form as a last time buy however in many cases this can be impractical or give rise to further complexities. Both Plastic and Ceramic Hermetic packages can be stored in long term storage and have separate considerations.

It is even helpful to store build materials in the world of obsolescence including packages, lids, lead frames, adhesives as any changes/substitutions in the aerospace/defence world can trigger expensive requalification.

What are the main product lines you see being stored?

The main product lines we see include manufacturers like TI, Xilinx and Analog devices. Last time buys of more modern ASIC or even AI chips are also common including high count BGAs, TQFPs etc.

How do you get Plastic items ready for storage?

With plastic items, we bake them beforehand to remove any moisture that might be remaining in the package. They are then sealed in a MBB (Moisture barrier bag) with a moisture indicator and desiccant material inside. Per Industry guidelines if they are stored below the 5% RH limit they can be considered to have an indefinite shelf life. This means they will not need to go through a re bake prior to production use and can simply be mounted directly into application.

Do you hold plastic components in a different cabinet?

This is an interesting question as a lot of the current data supports not storing die at extremely low humidity. Extreme low humidity can have adverse effects on raw die including static buildup and most guidelines suggest between 7-30%. With plastic devices, you want to store them in a very low humidity (ideally sub 5%) because as mentioned earlier it gives the product an indefinite shelf life per MSL guidelines. This reduces the possibility of corrosion and removes the need to bake out prior to being assembled because they are already at the required MSL level.

If you have any other questions about long-term storage please get in touch with the team here at Force Technologies.