Technical guide

What happens when a component in your BOM goes obsolete?

A product that has shipped for six years suddenly cannot be built, because one part on the board has reached end-of-life and the last reels are gone. It is one of the most common reasons a working design has to be touched again — and how much it costs depends almost entirely on decisions made long before the part disappeared.

Reviewed by Tom You (8 years’ experience) and Hai Huang (7 years’ experience)

Called “obsolete”5 different states
Genuinely a problem1 of them
When to find outBefore you need to
What to trackLifecycle status

The short answer: “obsolete” covers at least five different situations, and only the last one is genuinely a problem. What you can still do depends on which one you are in — and the time to find out is before you need to, by tracking the lifecycle status of your critical parts the way you already track their price and lead time. The one move to avoid is treating broker stock as the solution: it is the fastest answer, and it is the one that comes back.

An overhead view of the SMT floor at Hongrong's Shenzhen factory, with feeder-loaded lines and production dashboards on the screens — **The reel on the feeder is either traceable or it is not**Component sourcing is invisible in a finished board and decisive in whether that board can be built again — or defended to a customer, an auditor or a regulator two years from now.

Six lifecycle statuses, and what each one still allows

The status is written on the distributor's page. The action is yours, and it is different in each row.

Component lifecycle status in practice
What the distributor says	What it actually means	What you can still do
Active	In production, no restriction.	Nothing to do. Keep watching it.
NRND (not recommended for new designs)	Still made, still fully available, but the manufacturer is steering new designs away from it. No end date is given.	This is the cheapest moment you will ever get. Qualify an alternative now, while the current part is still available to build with.
Last-time buy (LTB)	The manufacturer has announced the final date on which an order can be placed.	Place your final order, sized to the number of years you actually need. This is the only moment at which it can be done.
End-of-life (EOL)	The last-time-buy date has passed. Distributor stock is whatever is left in the channel.	Buy only what is genuinely available from authorised channels, and start the replacement process immediately.
On allocation	Still in production, but supply is deliberately restricted and quantities are assigned by the manufacturer.	Do not redesign for this. Allocation is temporary; obsolescence is not. Reserve what you can and buffer your schedule.
Obsolete / discontinued	No longer manufactured by anyone. What exists is what is in the world, plus whatever has been imitated.	Three options only: a drop-in equivalent, a functional equivalent with a design change, or a redesign. See below.

Words that all get called “obsolete”

The distinction matters because the response is different in each case.

Two of those statuses are commonly called obsolescence and are not. Allocation is a supply problem — the part is still being made and will be again; redesigning around it is an expensive overreaction to a temporary shortage. NRND is a warning rather than a failure: nothing has been discontinued, and treating it as an emergency wastes the one advantage it gives you, which is time. A part is not obsolete when it disappears. It is obsolete the day the manufacturer stops recommending it for new designs — and that is the day the clock starts.

The last-time-buy decision

When an LTB window opens, the instinct is to buy for the lifetime of the product. That is sometimes right and often not, because a component in storage is not the same thing as a component in stock. Most surface-mount parts have a moisture sensitivity level, and their floor life — the time they can spend exposed to ambient air before reflow — is measured in days. Parts that sit for years need baking before use, and their solderability degrades rather than holding steady.

So the LTB order should be sized to a defined horizon, stored under the manufacturer's conditions, sealed with desiccant, and recorded with date codes as it is consumed. And it is a bridge, not a strategy: if the part carries firmware, an LTB stock that outlasts the ability to recompile for its replacement has bought time you cannot spend.

Why broker stock is the answer people regret

It solves the schedule problem and creates a worse one.

The open market for electronic components is made up largely of excess inventory: parts a large manufacturer over-ordered, or stock left over when another customer cancelled a build. Nothing about that is inherently dishonest. What is missing is the manufacturer's warranty and the traceability chain — so the part cannot be verified as what it claims to be, and if it fails there is no lot to trace back to.

That matters because counterfeits are not only non-working parts. The more dangerous ones are refurbished units sold as new, re-marked components of an inferior grade, parts from a failing production lot, or a faster-rated part sold at a slower part's price. Incoming inspection can catch a percentage of these — X-ray, decapsulation and electrical test each catch something — and none of them catches everything, and each of them costs money and time on every lot.

The administrative cost is just as real. An untraceable part breaks the traceability chain your quality system depends on, which is a problem rather than a preference once you build for medical or automotive customers: under ISO 13485 and IATF 16949, traceability is a requirement, and a brokered part can make an otherwise-compliant build non-compliant. The rule that keeps this simple is to ask for the manufacturer's certificate of conformance. Authorised surplus stock has paperwork. If the answer is that there is none, the discount is being paid for with risk you are carrying.

The three real options once a part is gone

In ascending order of cost, and of how much of the original design survives.

1. A drop-in replacement

Same footprint, pinout, voltage range and timing — usually a successor part from the same manufacturer, or a second source that genuinely matches. This is the cheapest outcome and the one to look for first. The trap is the phrase “pin-compatible”, which describes the footprint and not the behaviour. Electrical, thermal and timing differences that do not show up in the pinout have a habit of showing up on the board, so a drop-in candidate is verified against the datasheet and then verified again on an assembled unit before the whole order is built.

2. A functional equivalent, with a change

The part does the same job but not identically: a different register map, a different peripheral configuration, sometimes a different package on the same die family. The board may not change at all while the firmware does. This is the expensive middle path, and it is easy to underestimate: the physical build is unchanged, so it looks like a small piece of work, but it carries a full engineering change order, a new validation cycle and a new set of test limits.

3. A redesign

New silicon family, new layout, and for medical devices a regulatory submission attached. It is almost always the most expensive option in the first year and frequently the cheapest over five, because it ends the cycle instead of deferring it — which is worth remembering when the second part on the same board reaches end-of-life eighteen months later.

What a contract manufacturer can actually do about it

Less than a distributor, more than nothing — and the difference is whether it happens before you need it.

Flag it at the quote stage. We review your BOM when we quote the order, so a part with a lifecycle problem surfaces before the build rather than during it. This is also when an alternative is cheapest to consider.
Cross-reference it. Identify a candidate drop-in from the same manufacturer's successor line where one exists, and say plainly when the honest answer is that there is no drop-in and the board has to change.
Source the replacement. Our component sourcing covers well-known suppliers including Sharp, Toshiba, STMicroelectronics, Samsung, Infineon, JRC and NEC, and we source replacement solutions for obsolete and discontinued parts — including parts that have to be qualified rather than simply substituted.
Catch the wrong part at assembly. In-line and offline AOI and 3D X-ray on the finished board will not verify a counterfeit, but they do catch a misplaced, wrong-orientation or damaged part before it reaches your customer.
Say when it cannot be done. If a part cannot be obtained through a channel we can trace, we will tell you rather than quietly fill the gap. You should expect that answer from any supplier, and be suspicious of one that never gives it.

What to put in your BOM now, so this hurts less later

The manufacturer part number and the manufacturer — not a description. Substitutability is impossible to judge without them.
A criticality flag on each part: whether production stopping is unacceptable, or whether a delay could be absorbed.
An approved alternate, with a status you have verified yourself rather than copied from a comparison site.
The date code and lot of the last build. It is the shortest path to diagnosing a change you did not ask for.
A lifecycle review once a year, and again immediately before any last-time-buy window closes. Most of the cost in this guide is the cost of finding out late.

Common questions

Is a component obsolete as soon as it disappears from the distributor?

No. There are six lifecycle statuses and only the last one means the part is gone: active, NRND, last-time buy, end-of-life, on allocation, and obsolete. Two of them are commonly called obsolescence and are not. Allocation is a supply problem — the part is still being made and will be again. NRND is still fully available, and the manufacturer is only steering new designs away from it. A part is not obsolete when it disappears; it is obsolete the day the manufacturer stops recommending it for new designs.

Can you source a part that is already obsolete?

Within what a contract manufacturer can actually do. We review the BOM when we quote, so a lifecycle problem surfaces before the build rather than during it; we cross-reference a drop-in from the same manufacturer’s successor line where one exists, and say plainly when the honest answer is that there is no drop-in and the board has to change; and we source replacement solutions for obsolete and discontinued parts, including parts that have to be qualified rather than simply substituted. If a part cannot be obtained through a channel we can trace, we say so rather than quietly filling the gap.

Why not just buy the missing part from a broker?

Because it solves the schedule problem and creates a worse one. Broker stock is usually excess inventory without the manufacturer’s warranty or the traceability chain, so the part cannot be verified as what it claims to be and a failure has no lot to trace back to. Under ISO 13485 and IATF 16949 traceability is a requirement, so a brokered part can make an otherwise-compliant build non-compliant. The rule that keeps this simple is to ask for the manufacturer’s certificate of conformance: authorised surplus stock has paperwork.