When Entire Assemblies Go Into Storage Instead of Components
When a critical component is discontinued, it is rarely just about a part number. An unavailable component can trigger a redesign, require new approvals or limit the repairability of an assembly. A missing microcontroller quickly turns into a circuit board that can no longer be manufactured, then into a control unit that can no longer be repaired — and, in the field, into a problem for the entire product.
One answer is end-of-life production: while all components are still available, circuit boards or complete control units are built in advance and stored. As with last-time stocking of individual components, the required quantity has to be calculated carefully. The difference shows up in storage: what sits there is no longer a single component but a finished assembly — with its own requirements.
Long-term storage does not replace product development or sourcing strategy. It does, however, keep an option open: pre-built assemblies remain available instead of a redesign or phase-out being decided under time pressure.
Storage Duration Is Not a Standard Question
A production buffer for the next twelve months needs a different concept from a control unit that must remain repairable for many years. The appropriate storage horizon follows from the product lifecycle, spare-parts or service commitment, demand profile, component technology and assembly criticality.
The right question therefore is not “How much warehouse space do we need?” It is: Which commitment must this inventory still fulfil — and how do we make sure it is actually ready for use when that point comes?
What Puts Assemblies at Risk in Storage
The risks are usually not visible. Humidity can affect solderability. Electrostatic discharge can cause latent defects. Packaging ages. Assemblies add another layer: control units combine many sensitive components in a small space. They therefore need protection not only against electrostatic discharge but also against dust. And electrolytic capacitors can lose functionality over time even when the housing remains externally unchanged.
That is why a protection concept means more than a climate-controlled storage location. Depending on the assembly and the intended storage period, it combines ESD and moisture protection, controlled storage conditions, nitrogen atmosphere, vacuum sealing and documented repacking cycles. At btv technologies, inventory is also stored under FM Global fire protection. For assemblies, powering and functional testing can be agreed as well.
The protection tiers for individual components are covered in our article on long-term storage for electronic components.
Preserving Function: Powering and Test Cycles
Control units illustrate the difference between passive and actively managed storage. A device can look brand-new while individual components inside it no longer retain the required functional reserve.
The critical point is often the electrolytic capacitors. Without regular powering, they can lose their insulating capacity — up to total failure of the assembly.
With a coordinated power-on concept, control units and modules are therefore powered on fixed, agreed cycles. This reforms the capacitors and restores their insulation capacity and voltage resistance. Leakage-current measurement confirms the result. At the same time, powering reveals potential problems early: while still in storage, not on reinstallation.
Whether and in what form this is useful depends on the assembly, the component technology and the planned storage horizon. The point is not to treat every item in the same way, but to select measures that fit the actual risk.
Why Every Assembly Needs Its Own Powering Concept
How often and for how long an assembly is powered cannot be read off a table. It depends on which components are fitted, how the assembly is built and how long it is meant to stay in storage. A fixed interval for all inventory would be easy to manage, but it does not automatically fit every assembly.
At btv technologies, the powering concept is therefore defined individually for each assembly — on request together with independent test houses. The concept sets out the cycles in which the assembly is powered and how the result is checked.
What Has to Be Documented Years Later
When an organisation needs a stored assembly years later, it needs more than the statement that it was stored professionally. What matters is what can be demonstrated throughout the period: identity, quantity, storage movements, protection cycles, checks and deliveries — and, for assemblies, the powering cycles and their test results.
What this looks like in practice is shown by a Tier-1 supplier that had to secure spare-parts supply for a control unit for 15 years. The approach combined end-of-life production, storage under nitrogen atmosphere, scheduled repacking and a power-cycling concept. No field failures were documented over the entire supply period.
Why independent evidence matters more than testing by the storage provider itself is explained in our article on value retention for electronic components.
An Assembly's Value Is Not Its Weight
A protection concept does not end with temperature, humidity and documentation. It also has to answer what happens in the event of a loss. Many warehouses are liable under the German General Freight Forwarder Terms and Conditions (ADSp) based on the weight of the goods — often at only a few euros per kilogram and up to a maximum total claim of EUR 35,000 per incident. For pre-built control units that secure a spare-parts obligation for years, that cap can quickly fall short of the inventory's economic value.
At btv technologies, stored inventory is insured based on its actual value, not its weight — from Standard Storage onward. How this differs from a general freight-forwarding warehouse is explained in our article on value retention for electronic components.
