By Craig Armenti, PCB Marketing Engineer, Mentor Graphics
Reducing PCB Failure Rates Due
to Vibration and Acceleration
With proper design practices, engineers can avoid premature product failure caused by intense vibrations and constant acceleration.
Many of today’s products are required to operate under significant environmental stress for hundreds of hours. Deriving the physical
constraints and fatigue issues for a design prior to
manufacturing is essential to reducing board failure and
thereby improving product quality. The need to design
a reliable product is not a new concept, however, it has
begun to receive greater attention in recent years. The
days of depending on a product’s “made in” label as an
indicator of reliability are long gone. Customers have
come to expect reliability across the industry spectrum
no matter where actual production occurs. Companies
that are known to produce reliable products are
rewarded in the marketplace with increased purchases
as compared to their non-reliable counterparts. Reliable
products have less risk of failure, less field returns, and
less warranty claims, all of which contribute to higher
profitability. It is a given that every product is expected
to fail at some point, but premature failures can be
mitigated through proper design with attention to
potential issues due to vibration and acceleration.
Common Methods of Validation
Industry statistics indicate field failure rates of up to
15 to 20 percent in the first year of newly launched
electronic products. In harsh environments, fatigue can
be responsible for up to 20 percent of those failures.
Most design teams rely on physical testing to determine
reliability issues. Physical vibration and acceleration
testing, also known as Highly Accelerated Lifecycle
Testing (HALT), provides a clear mechanism to ensure
reliability of a product and identify potential failures
due to environmental factors. This is accomplished
by applying a much higher fatigue than the actual
product will undergo, thereby forcing failures and
identifying weak spots. However, the process is costly
and destructive, potentially taking months per design to
complete. Furthermore, results can vary between testing
chambers, possibly concealing accuracy and functional
limitations on components that could then fail in the
field. With the high cost and increased time-to-market,
only a few prototype designs actually go through physical
vibration and acceleration testing.
The aforementioned cost and time issues associated
with physical testing have resulted in many design
teams adding a mechanical analysis step to the product
development process in order to better validate
reliability. While this added step improves the process, it
still has limitations, including:
• Extensive library/model development.
• Lengthy setup and simulation cycles.
• Simulation results that are not tuned to the specific
printed circuit board.
All of this means that, even with a specialist, mechanical
analysis is still unable to achieve 100 percent test coverage.
Improving Validation by Simulating During Design
To optimize the process and minimize time between
finding and correcting issues, simulation of vibration
and acceleration should be added into the design
stage. To be clear, this does not eliminate the need
for physical HALT, but by eliminating early failures
through simulation in the layout domain, design teams
can reduce HALT expenses and ensure that reliability
specialists have more time to focus on hidden issues.