An Overview of Electronic
Cornell B.S. E.E. ‘99
Cornell M.Eng E.E. ‘00
• In order to release an electronic
component into the market, a series of
evaluations exerting electrical and
environmental stress must be performed in
order to prove out component reliability.
To carry out these evaluations without
gating product release, elevated stress
conditions are used in shorter durations
and compared against lifetime usage of
• Quality vs Reliability
• Bathtub Curve
• Common Failure Mechanisms
• Survey of Common Reliability Evaluations
• Usage Models
Quality vs Reliability
• Quality is a measure of overall product
health at the time of release (i.e.
percentage of products that are functional
• Reliability is a measure of overall product
health over the expected lifetime of the
The Bathtub Curve
• Infant Mortality
– Decreasing failure rate due to early life fails that were
not caught at production test.
• Normal Life
– Constant failure rate since early life fails have been
weeded out. These are random failures.
– This is the end of life for electronic components. The
failure rate increases because operation is beyond
what the component was designed to do.
Common Failure Mechanisms
– Gate oxide pinhole
– Metal-to-metal short
– Cu-line migration
• Silicon-Package interaction
– Die cracking
• What is burn-in?
– Burn-in is a method to stress silicon to emulate the
type of stress it would undergo in its normal life in a
• Why do burn-in?
– For any product, an assessment of the reliability over
the intended lifetime of product is necessary to
protect the customer.
• How is burn-in done?
– Utilizing the built-in logic test functionality, the silicon
operates at a higher voltage and temperature than
normal to induce a faster degradation
• One common way to
understand how time-to-
fail varies with
temperature is the t f Ae kT
Arrhenius equation. It
takes the form:
• The acceleration factor Ea 1 1
between operation at two k T1 T2
different temperatures is:
• Voltage acceleration
can also follow an C (Vstress Vuse )
• Typically, voltage
acceleration is much
more effective at
Temperature/Voltage Stress Use
• Temperature and voltage stress
accelerate different failure mechanisms in
varying ways depending on the process
technology. Each technology will be
affected differently depending on:
– Susceptibility to different types of failure
– Design rules for the process technology
• Burn-in is one of the main tools for
assessing product reliability. It requires
equipment to run the evaluation:
– Burn-in socket: holds the product and
connects it to the burn-in board.
– Burn-in board: board which holds an array of
sockets and routes signals to each socket.
– Burn-in oven: provides the vector patterns to
stress logic in the device and regulates
• With the increasing complexity of devices, there
are an increasing number of failure mechanisms
and evaluations to assess them. Here are some
of the common ones:
• Life stress test (burn-in)
• Electrostatic Discharge (ESD)
• Temperature Cycling
• Highly Accelerated Stress Test (HAST)
• Electrostatic discharge occurs when charge
flows from one place to another and an
equilibrium is reached.
– Two objects with different potentials come into
contact and current flows between them.
– This potential difference can be in the 1000s of volts
and cause amps of current to flow in nanoseconds.
– Unprotected CMOS devices will be blown-out with
less than 100V of potential difference.
• Thus, electronic components require ESD circuit
protection to handle these potentials on the
• Sources of ESD can come from anywhere:
– Human touch
– Manufacturing process
• Thus, different ESD tests are done to
cover different sources:
– Human body model (HBM)
– Machine model (MM)
– Charged device model (CDM)
• Temperature cycling swings a packaged
component from sub-zero to high temperatures
to stress the package.
• The temperature cycling evaluation typically
takes a sample of functionally good components
and cycles them. These parts are then tested
afterwards to check for functionality.
• Typical failures:
– Package delamination
– Die cracking
• HAST exposes a packaged component to
thermal and humidity stress.
• The components sit in a chamber which creates
conditions of high temperature and a high
• Sometimes a biased HAST is done to exert
voltage stress on the package metal traces.
• Typical failure modes:
– Metal line migration (biased)
• Many evaluations exist for different applications
and different types.
• Each of the aforementioned evaluations (ESD,
HAST, Temperature Cycling) has different
versions to fit different usage models.
• Therefore, for a given electronic component, a
usage model must be developed to figure out
what stresses should be used to emulate a true
Usage Models continued
• Usage models vary greatly from component to
component. Here are some cases:
– Desktop computer
• Not mobile, operates inside.
– Notebook computer
• Mobile, operates in a variety of temperature, humid conditions.
Might get dropped.
• Mobile, operates in a variety of temperature, humid conditions. Will
• In addition, each of these devices has a different
expected usage life.
• Thus, understanding the usage of the electronic
component is essential to ensuring proper reliability for
• Quality and reliability are major concerns
for any electronic component used today.
• Through reliability stress, we can
understand what makes our products
weak and address those issues before
they affect customers.
• In order to properly stress electronic
components, we must first understand
how they are used.