New capacitor products from Knowles, KEMET, and TDK

By Warren Miller, contributing writer

Capacitors
are one of the many electronic devices that don’t get as much respect as they
deserve. Without these workhorse devices, your design wouldn’t have power and be
able to withstand power-line noise or generate most analog signals. In
high-reliability applications, it can be critical to find capacitors with
stable and precise characteristics. This roundup looks at a few of the most
recent announcements of capacitors with high precision and stability.

The Novacap multilayer ceramic capacitors (MLCCs) from Knowles are RoHS-compliant, high-capacitance
BME MLC chip capacitors manufactured in stable Class II dielectrics X7R and
X5R. They have a capacitive range from 6.8 nF up to 100 μF with tolerances of
±10% and ±20%.

Because of the extremely low equivalent series resistance (ESR)
characteristics, the MLCCs can be used as replacements for tantalum and low-ESR
electrolytic capacitors without polarity concerns, according to the company.

These devices can be used as power supply bypass capacitors,
smoothing capacitors, input/output filters in DC/DC converters, and in digital
circuits and LCD modules. All parts are available with high-reliability
screening.

Nickel barrier termination options include tin, tin/lead, or
gold flash. The gold-flash option eliminates the tin “whiskering” issue, which has
become prevalent because pure tin-plated terminations, required to comply with the
RoHS directive to eliminate lead, “allow tin whiskers to grow from surfaces and
can cause electrical short-circuits and failures,” said the company. This type
of failure is of special concern in high-reliability applications such as
medical implantable devices and military equipment.

Novacap
MLCCs from Knowles. Image source: Knowles.

KEMET has expanded its X7R 250-V MLCC series to
include smaller case sizes and increased capacitance values. Saving PCB space
by using compact surface-mount technology footprints, the extended portfolio
now offers a capacitance range of 10 pF to 47 μF in case sizes as small
as 0603. These characteristics can be critical in achieving higher voltages in
automotive applications such as lighting, electric charging, sensors, and electromagnetic
interference (EMI) suppression. The 220-V power system and small case sizes make them well-suited for high-power, small-form-factor applications.

KEMET’s X7R
dielectric features a 125°C maximum operating temperature. “X7R exhibits a predictable
change in capacitance with respect to time and voltage, with a minimal change
in capacitance with reference to ambient temperature,” according to KEMET. “Capacitance
change is limited to ±15% from −55°C to 125°C.”

TDK Corp. claims the
industry’s first soft-termination
MLCCs with low ESR
.
The new CN series features terminal electrodes with a conductive resin layer
that provides high mechanical robustness to protect against board flexure. Specs
include capacitance values ranging from 2.2 µF to 22 µF and rated voltages from
16 V to 100 V. The MLCCs are available in commercial-grade and automotive-grade
X7R dielectric.

“Soft-termination
MLCCs, which can withstand the stress from board flexure, are an effective way
to prevent short circuits when used in battery lines,” said TDK. “Conventional
designs that coat the electrodes completely with resin, however, lead to higher
ESR and losses.”

TDK said that it “has
achieved the low terminal resistance values by applying the conductive resin
layer only where the terminal electrode contacts the PCB.” Target applications
include battery lines in automotive and industrial robot applications, “where
they help to improve system reliability”. Other applications include automotive
ECUs, advanced driver assistance systems (ADAS), and automated driving systems.