Page 49 - PEN Ebook May 2021

DESIGN Design

This article will help readers better understand severity. The most commonly referenced stresses

how their mission profiles connect to the vari- are related to temperature/voltage and thermo-
ous electronics reliability tests that are applied mechanical stress. Temperature/voltage stress
to each automotive-grade component during its is understood as the main aging effect for the
qualification. This article will explore several fre- silicon that is used within an IC. This aging effect
quently asked questions: impacts the material properties such that the IC
will see a performance degradation over time.
▶ What types of stresses might an electronic Thermomechanical stress refers to the mechan-
component see during its lifetime? ical forces that occur while a part expands and
contracts from temperature variation.

▶ Who is responsible for determining the reliabil-
ity capability of chosen ICs in a given design? The goal is to understand whether the specified
component’s performance can be guaranteed
▶ How can I apply the reliability testing “accel- at the end of the application’s targeted life. In
eration model” to confirm that a given IC has other words, will the application’s target life be
been tested up to and beyond my mission reached into the wear-out period of the typical
profile? semiconductor’s reliability bathtub curve? Due

to the inherent lifetime of semiconductors, the
In most industries, it is common to estimate the failure rate starts to increase rapidly due to wear.
Automotive Electronics electronics reliability of an application versus The harder the stress is over time, the earlier the

inherent life time is reached, and wear-out fail-
its target lifetime. In other words, will the appli-
Reliability Testing Starts cation be able to withstand the overall lifetime ures become more likely (see Figure 1).
stress? To make a reasona-
ble judgment, it is necessary
and Ends with the to understand what sorts of

stress the application will be
Mission Profile subjected to during its field

life. Subsequently, this antici-
pated field life stress must be
By Thomas Eikenberg, QA Manager, EMEA, Monolithic Power Systems compared to the stress that
all electronic components in
Automakers must design vehicles to thrive in a Meanwhile, integrated circuits (ICs) used for ve- the application were originally
broad spectrum of environments, from snowy hicle components are usually qualified based on qualified for. From there, one

tundra to scorching deserts. Unlike most consumer the Automotive Electronics Council’s AEC-Q100 can determine if the anticipat-
Figure 1: Bathtub Curve.
applications, where the expected lifespan can be standard. Products designed with these speci- ed field life stress would over-
months, automotive electronics are often expected fications in mind — such as MPS’s MPQ8875A- stress any device in the application, potentially Semiconductor manufacturers must qualify a
to last 15 years or more. When specifying a vehi- AEC1, a 40W digital buck-boost converter that leading to premature failures. This is particularly new product before it is released to production
cle component, it is common for OEMs and their can deliver 30W in a small 4mmx5mm QFN important for automotive applications, due to the and the market. During this qualification process,
suppliers to develop an automotive mission profile, package — are ideal for ADAS sensor fusion and industry’s stringent safety measures. the ICs are subjected to a number of stress tests
which is essentially a summary of all the expected digital cockpit systems. to provoke certain fail mechanisms. When con-
environmental and functional conditions that the Mission profiles are designed to mimic a par- sidering the aforementioned stresses, there are
component will face during its service life. ticular type of field stress, as well as its related two particularly useful tests.

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