[Webinar Recap Part Two] High Voltage MLCCs in Comparison to Safety MLCCs

In a recent webinar, Division Manager Pierre Lohrber explained the comparison of MLCCs for high voltage and safety applications.

Pierre is responsible for the capacitor business unit worldwide for Wurth Electronics. He has a background of more than 25 years of experience in the electronics business, as well as supply chain management, and supply chain risk management experience. His expertise gives him an overview of the market as a whole, including knowledge for different technologies of capacitors.

We’re covering part two of our recap on Pierre’s webinar. We will go over safety and mechanical similarities and differences, and provide a glimpse on the actual market situation today.

X & Y Safety MLCCs

Let’s start with X & Y safety MLCCs.

Safety Caps X1 / Y2 & X2

• Capacitance range: 33pF to 2200pF

• Rated voltage AC: 250V

• Temperature: Max:125°C / Min: -55°C

• Ceramic: NP0 / X7R

• Size: 1808 / 1812 / 2211

Capacitance range is small, because of the currents you allow for the safety applications.

X-Capacitors applications:

• Filtering of symmetric interferences between Line/Line Line/Neutral

• Typical capacitance values between 0,1µF and 10,0µF (depending on the technology)

Y-Capacitors applications:

• Filtering of asymmetric interferences between Line and Ground (device)

• Small capacitance values to keep leakage current to Ground significantly lower to meet international standards for human safety (typically 4,7nF)

The X-capacitors are used for filtering of the symmetric interferences and to secure your application, while the Y-capacitors are used for filtering asymmetric interferences between Line and Ground.

X / Y Capacitors and Related Certificates

To meet international standards for human safety, the Y-capacitors are used for security reasons if there’s any defect inside the application. The current flow will go to earth and not through the human body.

Shown above, we see specifications for IEC 60384-14 standard. We have the different key voltages as well as the peak voltage.

Standards & Certificates

For X and Y-capacitors, there are certificates for which we we have to apply. Which certificates are necessary?

Safety Caps X1/Y2 – X2

• TUV >> European certificate

• cULus / cURus >> US / Canada market

• Certificate for compliance according to IEC 60384-14 & IEC 60950 by e.g. TUV or UL

Keep in mind, the industry standard is stricter than the IEC 60950 standard.

Industry IEC 60384-1 vs. Information Technology (e.g. Telecommunication / Video)

• IEC 60950 (& IEC 60065) – will be replaced by IEC 62368-1 in 2019

• UL certificate for 22xx size: WE - UL: E345659 is based on the standard IEC 60384-1

• UL certificate for 18xx size: WE - UL: E331896 is based on the standard IEC 60950-1

Why are there two different UL certificates? For higher voltages, you always have to keep in mind the distances of the creepage and clearance.

Creepage is the separation between two PC board solder eyes, as measured along the surface of the board. Clearance denotes the shortest distance between two conductive parts, as measured through the air.

With MLCCs, we have a limited distance between the two terminals of the MLCC of which to be aware. For all voltages back to 250V, we have to meet the clearance of 3mm without any pollution.

See the pollution table above and be sure to keep the IEC standards in mind.

Depending on required performance, different constructions are used for the MLCC.

Shown above are the three main mechanical construction of MLCCs within a standard, floating, or open mode pattern.

In the upper left is a standard item for a regular MLCC. Lower left is a floating pattern for mid- and high-voltage caps, with internal series connections. To lower the voltage per cap, you have a series of capacitors inside the layer construction, giving you a higher voltage frankness of the MLCC.

The upper right is the mechanical construction of an open model capacitor, giving you layer construction in case of problem with bending of the PCB, or possible mechanical cracking of the MLCC—all to avoid a shortage inside the MLCC. The lower right is another example of a floating pattern for higher voltages with some capacitance tuning inside.

Terminal Constructions

Besides different layering for mid- to high-voltage and safety caps, the terminals are also different.

Shown above, in the upper left, is the substandard terminal for regular terminal design with copper, nickel, and tin. On the lower right is a higher reliability safety part used for silver, nickel, and tin.

The thickness and the layer construction of terminals are different. It differs between the mid- and high-voltage and the safety caps.

See the differences between the safety caps, safety MLCCs, and mid- and high-voltage MLCCs.

The CSSA has sizes from 1808 to 2220. The voltage for the CSSA is 250 volts AC, meaning it’s absolutely mandatory to have a TUV, the VDE, and UL certificate for these safety caps.

The CSMH has sizes from 0603 to 1812, with working voltages from 200V to 4kV. The applications for CSMH are used for blocking and coupling. There is no certificate for mid- and high-voltage, and we use a standard and floating layer construction.

A Glimpse on the MLCC World Market

Shown above is a short overview of the MLCC market situation.

The demand for high capacitance MLCCs has raised over the last three years—especially for replacing tantalum caps. Tantalum is on the materials list of concerns. Tantalum mining in Africa, and in China, is under adverse conditions. The price volatility is very high for tantalum.

The market supply for raw material is forged, because of the high capacitance caps, which are mainly produced in Japan. Due to low-margin business in recent years, there was no major investment into MLCC business over nearly a decade. Raising the production capabilities in a very short time is not possible.

Due to the current situation with MLCC business, it’s really important to work closely with your supplier to give long-term outlook and forecast to secure any quantities.

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