and Effects Analysis (FMEA)
and Effects Analysis,
is a methodology for identifying the potential failure modes that a
product or process may encounter, assessing the risks associated with
these failure modes, prioritization of these failure modes according to
their urgency, and prevention of the more urgent failure modes, i.e.,
the ones that are most likely to cause serious harm to the company.
The output of
an FMEA cycle is the
FMEA Table, which documents how vulnerable a
product or process is to its potential failure modes. The FMEA
table also shows the level of risk attached to each potential failure
mode, and the corrective actions needed (or already completed) to make
the product or process more robust. The FMEA Table generally
consists of 16 to 17 columns, with each column corresponding to a piece
of information required by FMEA.
The FMEA is a
proactive analysis tool, allowing engineers to anticipate failure modes
even before they happen, or even before a new product or process is
released. It also helps the engineer to prevent the negative
effects of these failure modes from reaching the customer, primarily by
eliminating their causes and increasing the chances of detecting them
before they can do any damage. The actions generated by a good FMEA
cycle will also translate to better yield, quality, reliability, and of
course, greater customer satisfaction.
There are many types of FMEA,
but the most widely used are probably the following: 1) System
FMEA, which is used for global systems; 2) Design or Product FMEA, which is used
for components or subsystems; 3) Process FMEA, which is used for
manufacturing and assembly processes; 4) Service FMEA, which is used for
services; and 5) Software FMEA, which is used for software.
In the semiconductor industry, the Design or Product FMEA and the Process FMEA are
the most frequently-encountered FMEA versions.
Despite the existence of many
types of FMEA today, the basic structure and process for executing them remains
the same. Any FMEA process must include the following steps,
information details of
which are documented in the FMEA Table:
1) Assembly of the team;
2) Understanding of the
Product or Process to be subjected to FMEA;
3) Breaking down of the
product or process into its components or steps (components and steps
are also known as items);
4) Identification and
assessment of the following for every item listed: function(s),
potential failure mode(s), failure mode effect(s), failure mode cause(s),
and controls for detecting or preventing the failure mode(s);
5) Evaluation of the risks
associated with the failures modes and prioritizing them according to
6) Implementation of
corrective actions to minimize the occurrence of the more significant
7) Reassessment of the
product or process by another cycle of FMEA after the actions have been
8) Regular updating of the
Please refer to the
FMEA Procedural Guide
for more details on how FMEA is usually performed.
The most critical
information on the
FMEA Table is the
Risk Priority Number (RPN), which
is the numerical rating given to the level of risk associated with a
failure mode, and therefore denotes the urgency of addressing that
The RPN is actually the product of three (3) factors,
severity of the effect of the failure mode (SEV), the
probability of the occurrence of the cause of the failure mode (PF, for
probability factor), and the
effectiveness of the controls for detecting
and preventing the failure mode (DET). Thus, RPN = SEV x PF x DET.
The SEV, PF, and DET are also documented in the FMEA Table.
The FMEA Table is a living
document, constantly changing from the time of its first release when
the product or process is still being designed until its archiving after
the product or process has been obsoleted.
Critical times or
events that require an update to the FMEA Table include the following:
1) when a new product or process is being designed or introduced;
2) when a critical change in the operating conditions of the product or
3) when the product or process itself undergoes a change;
when a new regulation that affects the product or process is instituted;
when customer complaints about the product or process are received; and
error in the FMEA Table is discovered or new information that affects
its contents come to light.
Many published standards on
FMEA procedures and reporting formats now exist. Among them are
the SAE J1739, the AIAG FMEA-3, and the Mil-Std-1629A.
FMEA Process Guide; Failure
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