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What is reliability technology for ceramic capacitors?

What is reliability engineering?

What exactly is reliability engineering? Let us start here.
Reliability engineering is also called failure engineering. It is a branch of engineering that involves increasing reliability of products by assessing and analyzing how failure is caused in the product. In other words, it can be considered engineering that creates broken products.

*The difference between failure and defect
- Defective products are defective from the moment they are produced.
- Broken products were conforming products when they were produced, but became defective products over time.

Reliability engineering deals with the process during which a conforming product turns into a defective product.
There are three factors that cause failure:

1. Latent internal causes that existed in the product from the start (predispositions)
2. External stressors such as heat and humidity applied from the usage environment (external causes)
3. Degradation with time

image of factors that cause failure

What is failure?

In the preceding part, I said that, "Reliability engineering is also called failure engineering." There are actually different types of patterns of failure. The bathtub curve below is a graph that shows the correlation between failure rate and time.

Image of bathtub curve
Bathtub curve

During a product's lifetime, it goes through three successive periods (initial failure, chance failure, wear-out failure) that each has different causes of failure.

Initial failure

Failure occurs soon after starting to use the product, and the failure rate drops gradually over time. The main cause is thought to be latent defects. Improvement of the design and filtering process and screening of products are essential for preventing such products from being leaked to the market.

Chance failure

After the initial failure period eases, a period starts during which failure can occur by chance. These failures are usually caused by unpredictable events such as lightening and dropping the product. This means that such failure occurs at a nearly constant failure rate that is unrelated to how much time has passed. The goal is to reduce accidental defects in the production process and fluctuations in environmental stressors during use to approach a zero failure rate.

Wear-out failure

After the chance failure period has passed, the failure rate begins to rise gradually with the passage of time. This is mainly thought to be due to wear-and-tear of the product as the product reaches the end of its lifetime.

You can therefore see that there are different types of failures and that each has its own causes. For quality assurance, it is necessary to examine the factors in detail and select the best test method (reliability test).

What is a reliability test?

Next, I will explain reliability tests. Reliability tests are tests for predicting quality during the time a product will be used, from factory shipment to the end of mechanical lifetime in the market. The aim is to select stress factors that correlate strongly with the market environment, set the size of the stress and duration of application and accurately assess product reliability in as little time as possible.
Tests have various test items. Some tests go beyond looking at simple stressors and test the impact of multiple stressors acting simultaneously, and yet other tests have been developed to examine failure mechanisms.

The following chart shows some of the most common reliability tests used on electronic components.

Test itemsTest objectivePresumed environments
High-temperature tests
- High-temperature shelf test
- High-temperature load test
Assess the impact on components
in a high-temperature
Presumed use in devices such as
computers and vehicles that become
very hot inside during use.
High-temperature, high-humidity
- High-temperature, high-humidity
shelf test
- High-temperature, high-humidity
load test
Assess the impact on components
in a high-temperature,
high-humidity atmosphere.
Presume environments such as humid
areas in Southeast Asia, the rainy
season in Japan, bathrooms and
shower rooms.
Thermal shock testAssess the impact on components
when the surrounding
temperature changes suddenly.
Presumed use under changes in
ambient temperature when moving
from a cold room to a hot room or
in devices such as vehicles that
suddenly become very hot when
started up.
Drop testAssess the impact on components
when dropped during a process
or during use in the market.
Presume conditions in which products
are dropped.
When used in cell phones, tests are
conducted with a mock chassis.
Electrostatic tests
- MM, etc.
Assess the impact on products
when a charge from a human
body, metal instrument or
device is released.
HBM: Model for a charge released
from a human body when it touches
the electrode terminal.
MM: Model for a charge released from
a metal instrument when it touches
the electrode terminal.
Image of computers, cell phones and vehicles

These tests are performed so that only items that have been determined useable in market environments are brought to the market as a product.

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