Failure mode

Overview

A failure mode is the way in which a part, circuit or function fails as seen from outside, such as an open connection, a short, an output stuck high or low, a value drifting out of limits or a complete loss of function. Listing failure modes is the starting point of failure modes and effects analysis (FMEA) and of hardware safety analysis. A failure mode describes what is observed, not the physics that caused it.

How it works

Engineers list failure modes by asking, for each element of a design or process, how it could fail to do its job. For a chip that might mean a pin open or shorted, an output stuck at one value, a flipped memory bit, a missing clock, excessive leakage, or a function that works only some of the time.

Each mode is then linked to three things. Its effect is what happens at the next level up and for the end user, which sets its severity. Its causes are the defects or conditions that can produce it, such as a design error, a process defect, handling damage or a physical mechanism such as corrosion or fatigue. Its detection is how test, monitoring or a safety mechanism would catch it. FMEA ranks modes on severity, likelihood and detection so that the riskiest are acted on first; the joint AIAG and VDA handbook replaced the older risk priority number with an action priority scheme.

In functional safety work, each hardware part's failure rate is shared out across its failure modes, and each mode is classed by whether a safety mechanism detects it. A failure modes, effects and diagnostic analysis (FMEDA) builds the hardware safety metrics from these figures.

Examples

• A general-purpose output pin stuck low, listed in a microcontroller FMEA with its effect on the system and the test that would catch it.
• Excessive standby current, a parametric failure mode that can come from a gate oxide defect or a short between metal lines.
• A single bit flipped in an SRAM, a failure mode that error-correcting code is designed to detect and correct.
• Loss of output from a voltage regulator in an automotive power management chip, rated severe because the whole module stops.

Why it matters

Reliability, functional safety and quality engineers and failure analysts all use failure modes: to choose tests, design safety mechanisms, judge customer risk, or classify what was found on a returned part. A failure mode left off the list is a blind spot that no later analysis can fix.

In the chip lifecycle, failure modes are identified at architecture and design through design FMEA and safety analysis, and in process development through process FMEA. They shape qualification and production test plans, and they return in failure analysis of field returns, where the observed mode is the first clue to the cause.

It matters most to: Automotive Quality Engineer (IATF 16949), Failure Analysis Engineer, Functional Safety Engineer, Reliability Engineer, Safety Analysis Engineer

Common confusions

Not the same as failure mechanism

A failure mechanism is the physical, chemical or electrical process behind a failure, such as electromigration or corrosion. The failure mode is the observable result, such as an open circuit.

Not the same as failure effect

The effect is the consequence at higher levels, such as a lost function in a vehicle. The same failure mode can have very different effects depending on where the part is used.

Not the same as fault model

In manufacturing test, a fault model such as stuck-at is an abstraction used to generate patterns. It is related to failure modes but chosen to make test generation practical rather than to list how parts really fail.

Related standards

• IEC 60812 (failure modes and effects analysis, FMEA and FMECA)

Sources

1. IEC 60812:2018 Failure modes and effects analysis (FMEA and FMECA) (opens in a new tab), IEC, 2026-10-22
2. AIAG & VDA FMEA Handbook (opens in a new tab), AIAG, 2026-10-22
3. ISO 26262, Functional safety (Knowledge Center) (opens in a new tab), Semiconductor Engineering, 2026-10-22
4. Failure mode and effects analysis (Wikipedia) (opens in a new tab), Wikimedia Foundation, 2026-10-22

Related terms

• FMEA
• Failure mechanism
• FMEDA

Where it appears on the Hub

Used on 14 pages of the Hub. In each group, the pages that mention it most come first.