high voltage ceramic capacitors - engineering center · 2020-04-23 · high voltage product...

© KEMET Electronics Corporation. All Rights Reserved.

High Voltage Ceramic Capacitors

June, 2019


Agenda

• What is High Voltage

• MLCC Design

• Creepage vs Clearance

• Arcing and KEMET’s ArcShieldTM

• KEMET HV Portfolio


What is High Voltage?

High Voltage Product Portfolio

10,000V1,000V100V10V1V1V

DC: >250Vdc

AC: ≥250VacCeramics


MLCCs

C = Design Capacitance

K = Dielectric Constant

A = Overlap Area

d = Ceramic Thickness

n = Number of Electrodes

C = e0KA(n-1)

d

Detailed Cross Section

Inner Electrode

End Termination

Barrier Layer

Termination Finish

Dielectric Material


What is MLCC Surface Arcing?

Electrical breakdown between the two MLCC terminations or

between one of the terminations and the internal electrodes of

the capacitor within the ceramic body.

Influences• Humidity

• Surface Contamination

• Creepage Distance


Creepage vs Clearance

Clearance

Creepage

Creepage – Spacing between conductive elements through an insulating surface

Clearance – Spacing between conductive elements through air



Clearance = Creepage


The Phenomenon of Surface Arcing

Opposing

Terminations

Alternating layers create opposing

electrodes



First Counter

Electrode

Ionization of AirElectric Field

High field concentration



Electric Arc

Inception voltage < Rate Voltage


Surface Arcing Between MLCC Termination and the Internal Electrode Structure


Surface Arcing Failure Modes

Carbon Traces

Voltage Breakdown Failures

Terminal-to-Terminal Arcing Terminal-to-Active Arcing


Solutions for MLCC Surface Arcing

• Reduce electric field strength

• Reduce ionization of air at MLCC surface

• Maximizes available capacitance in a MLCC package size

Surface Coatings Serial Electrode Designs ArcShield Designs

• MLCC Coating

– Added by MLCC supplier

– Additional process step

– Critical that there is no damage to

or air gap under the coating

• PCB Coating

– Added after PCB assembly

– Additional process step

– Added cost

– Cannot rework

• Reduce electric field strength

– Available capacitance in a MLCC package

size is lowered

– Allows for higher voltage capability

– Reduces the probability of MLCC failure due

to flex crack


The Benefits of Coating Technology

Ionization of Air

Creepage Distance


Issues With Coating Technologies

Damaged CoatingElectric Arc


Serial Electrode DesignReduction of Electric Field

1uF 1000V

0.22uF 5000V

Single MLCC

Five Series MLCCs

Single Monolithic Structure

(Serial Design)0.22uF 5000V

Electric Field Distributed Across Individual MLCCs

Electric Field Distributed Across Each Serial Design

1000V

1000V 1000V 1000V 1000V 1000V

1000V 1000V 1000V 1000V 1000V

1

𝐶𝑒𝑓𝑓=

1

𝐶𝑁


Serial Electrode Design

Also known as “Serial Electrode” or “Floating Electrode” designs

Capacitive

AreaCapacitive

Area

Separation Between

Series Elements


“Serial” to “Shield” Design Comparison

“Serial” Design • With capacitors (N) in series, the

acting voltage on each capacitor is

reduced by the reciprocal of the

number of capacitors (1/N).

• Effective Capacitance is reduced:

“Shield” Design • Larger electrode area overlap A so

higher capacitance while retaining

high voltage breakdown.

• Thickness d between opposing

electrodes increased:

V/2 V/2

C =ϵoKNA

d

1

𝐶𝑒𝑓𝑓=

1

𝐶𝑁


KEMET ArcShield Technology

Shield

Electrodes

Shield

Electrodes


Explanation of Shield DesignReduction of Electric Field

Terminal-to-Terminal Arcing

Standard Design

Opposite Field extends close to terminal of opposed polarity so low energy barrier

Terminal-to-Terminal Arcing

ArcShield Design

Opposite Field is longer distance from terminal of opposed polarity increasing size of energy barrier

+-

E

+-

E


Explanation of Shield DesignDesigned for Higher Voltage

Consider a Standard Design

• In a standard overlap X7R MLCC there are 3 ways of

failing high voltage:

1. Arcing between terminal and 1st electrode of

opposite polarity

2. Arcing between terminals

3. Internal breakdown

Shield designs solve these voltage breakdown

issues by:

a. Adding a shield to prevent 1.

b. The shield also creates a barrier to 2.

c. Thicker actives for higher breakdown 3.

1.

2.

3.

+- a.b.

c.


ArcShield Key Features and Benefits

Shield Electrode Technology

Built Inside the MLCC

Patented Electrode Design • Suppresses an arc-over event while increasing available capacitance

Permanent protection!

• Competitive versions often use a non-permanent surface coating

BME X7R Dielectric

500, 630 and 1,000Vdc

0603 - 2225 Case Sizes

1.0nF – 560nF

Flexible Termination Available

“The World’s Smallest

High Voltage MLCC’s”


High Voltage Product Portfolio

20,000V10,000V5,000V3,000V2,000V1,000V630V500V

SMD Comm & Auto

SMD Mil Screened

KPS SM Series

KPS

Radial Leaded

Goldmax

HS Series

VRR/VCR Series

Pulse discharge Discharge voltage

SMD Comm

Arc-Shield

KC-LINK


HIGH VOLTAGEC900 Safety Disc

Safety SMD

ER Safety Disc

Class and Voltage Ratings:

• X1 400 VAC / Y2 250 VAC

• X1 440 VAC / Y2 300 VAC

• X1 760 VAC / Y1 500 VAC

• X1 400 VAC / Y1 250 VAC

• X1 400 VAC / Y1 400 VAC

Class and Voltage Ratings

• X1 250 VAC / Y2 250 VAC

• X2 250 VAC

• Up to 5 kV Pulse Capable

• Industrial Grade

Case Sizes:

• 1808-2225

Lead Styles:

• Straight

• Outside

• Vertical

Class and Voltage Ratings:

• X1 440 VAC / Y2 250 VAC

• X1 440 VAC / Y2 300 VAC

• X1 760 VAC / Y1 500 VAC

Lead Styles:

• Straight

• Outside

• Vertical

AC, AS, AH ERO, ERK, ERP

KJ Safety DiscClass and Voltage Ratings:

• X1 440 VAC / Y1 400 VAC

• X1 400 VAC / Y1 250 VAC

Lead Styles:

• Straight

• Outside

• Vertical

KJN, KJY

COMING

SOON



Clearance

Creepage



Clearance

CreepageClearance

Creepage


More InformationComponent Edge

https://search.kemet.com/component-edge/#/

https://search.kemet.com/component-edge/#/


More InformationComponent Edge

https://search.kemet.com

https://search.kemet.com/


MAKING THE WORLD A BETTER, SAFER,

MORE CONNECTED PLACE TO LIVE.

KEMET100.COM #KEMET100

Thank you!

Mark Laps Technical Product Manager - Ceramics

KEMET Electronics

[email protected]

high voltage ceramic capacitors - engineering center · 2020-04-23 · high voltage product...

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