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Film Capacitors

Design and Characteristics


Design


Metallization Layer or Metal Foil Free Margin

Film Dielectric (µm)

C = e0KA(n-1)

d

+

-

CT=C1+C2+C3+….Cn

Film &Metal Foil

MetallizedFilm

Metallized Film and Film/Foil Capacitors


Characteristics


Film-Foil and Metallized Film Technology



Feature Film-Foil Metallized

Resistance Low High

dV/dt High Restriction

Self-Healing No Good

Electrode

PlatesThick Thin

Moisture

AbsorptionHigh Low

Winding

TechnologyWound Wound & Stacked



Feature Film-Foil Metallized AdvantagesApplication

Advantages

Resistance Low HighHigh

RMS

Snubber, Pulse

Switching

dV/dt High RestrictionHigh

Surge

Snubber, Pulse

Switching

Self-Healing No GoodHigh

Reliability

EMI Suppressors

General

Electrode

PlatesThick Thin High C Density

Miniaturization

High CV

Moisture

AbsorptionHigh Low

High

Reliability

Harsh

Environment

Winding

TechnologyWound

Wound &

Stacked

Broader CV

Solutions

High CV

Low Cost


Winding Constructions I

Single Design

Single Layer

Film Foil

Dual Section

Single Layer

(Series)

Single Design

Multi-Layer

•Standard•General Purposes•Self-Healing

•High Current•No Self-Healing

•Higher Voltage•Self-Healing

•High Breakdown Voltage•Self-Healing


Single Design

Double Metallized, Single Layer

Triple Section


(Series)

Dual Section


(Series)

Dual Section

Foil & Metallized, Multi-Layer

(Series)

• High Current• Self-Healing

• High Current• High Voltage• Self-Healing

• High Current• High Voltage• Self-Healing

• High Current• High Voltage• Self-Healing (poor)

Winding Constructions II


• Constant resistance

• AC: Zinc with variable

share of Aluminum

• DC: Aluminum

• Stable and low resistive

contact

• Pulse/Snubber applications

• High dv/dt performance

• Aluminum, Zinc, HE Zinc

• Low electrical losses & high

breakdown voltage

optimization

• Customized resistance

profile

• DC application

• Aluminum, Zinc, HE Zinc

• AC & DC

• Linear Ω

• Customized profiles,

breakdown voltage, self-

healing & tan δ

optimization

• AC: Zinc

• DC: Aluminum

Metallization Methods and Profiles

FLAT HEAVY EDGE WIDE HEAVY EDGE SOFT SLOPE


Wound and Stacked Technology


• Great performances for peak voltage

withstanding

• Can be used with all film dielectrics

• Can use the lowest film thickness

• 1.0 µm PET; 2.4 µm PP

• Max. Voltage: 2,000 Vdc

• Cost effectiveness

• High number of capacitors produced per a

single frame

• Used mostly on small radial and SMD

• High capacitance volume efficiency

• High intrinsic peak current withstanding (dV/dt)

• Limited maximum voltage vs. wound

Wound and Stacked Technology


Soft Wound Technology


Soft Winding TechnologyManufacturing Process

1. Soft Winding and Pre-Flattening

2. Frame Assembling

3. Frame Pressing

4. Spraying

5. Thermal Treatment

6. Frame Disassembling

7. Elements Clearing-Testing

8. Elements and Bus-Bar Assembling

9. Case Assembling

10. Loading

11. Pre-Heating

12. 1st Resin Filling (Vacuum)

13. Resin Curing

14. 2nd Resin Filling

15. Resin Curing

16. Unloading

17. Post Curing

18. Final Testing

19. Packing


Winding


Film Dielectrics


Film Dielectric Technologies

Polyethylene

TerephthalatePET

Polyethylene

NaphthalatePEN

Polypropylene

MetallizedPP

Polyphenylene

SulphidePPS

Dielectric Constant (@1 KHz) 3.3

Minimum Commercial Thickness

(μm) 0.9

DF (% @ 1 KHz) 0.5

TCC (DC/C), -55 °C to +125 °C ±5.0%

Minimum Temperature (°C) -55

Maximum Temperature Typical

(°C)125

Maximum Temperature Extended

(°C) 150

Dielectric Breakdown (V/μm) 280

Melting Temperature CC) 254

Reflow & Multiple Reflows

Tmax (°C) - for SMD245

Self-Healing Medium




(μm) 1.4

DF (% @ 1 KHz) 0.4

TCC (DC/C), -55 °C to +125 °C ±5.0%



(°C)125


(°C) 170




Tmax (°C) - for SMD245 - 255

Self-Healing Medium-Low


Polyethylene

TerephthalatePET

Polyethylene

NaphthalatePEN

Polypropylene

MetallizedPP

Polyphenylene

SulphidePPS




(μm) 2.2 1.9

DF (% @ 1 KHz) 0.02

TCC (DC/C), -55 °C to +125 °C ±2.5%



(°C)105


(°C) 125




Tmax (°C) - for SMDNO

Self-Healing Excellent


Polyethylene

TerephthalatePET

Polyethylene

NaphthalatePEN

Polypropylene

MetallizedPP

Polyphenylene

SulphidePPS




(μm) 1.2

DF (% @ 1 KHz) 0.05

TCC (DC/C), -55 °C to +125 °C ±5.0%



(°C)125


(°C) 170




Tmax (°C) - for SMD260

Self-Healing Low


Polyethylene

TerephthalatePET

Polyethylene

NaphthalatePEN

Polypropylene

MetallizedPP

Polyphenylene

SulphidePPS



Polyethylene

TerephthalatePET

Polyethylene

NaphthalatePEN

Polypropylene

MetallizedPP

Polyphenylene

SulphidePPS

-60 -10 40 90

-4

-3

-2

-1

0

1

2

3

4

Tamb (°C)

ΔC

/C (

%)

PET PP PPS PEN

𝑓 = 1𝑘𝐻𝑧

-3

-2.5

-2

-1.5

-1

-0.5

0

0.5

1

0.1 1 10 100

ΔC

/C (

%)

f(kHz)

PP PPS PEN PET



Property PP PET PEN PPS

Key

Advantage

High Current

and Voltage

Stability over

Temperature

and Frequency

High C Density

High Working

Temperature

High C Density

High Working

Temperature

Very Stable

Tight tolerance

High Working

Temperature

Key

Limitation

Not Suitable

for High

Temperatures

Not Suitable

for High

Frequency

Not Suitable

for High

Frequency

High Cost

Limited Availability

Typical

Use

DC & AC High

Power, Pulse

DC Link

X & Y EMI

Suppressors

DC & AC Low Power

Bypassing, Blocking

Coupling &

Decoupling

Timing & Filters

DC Low Power

Bypassing, Blocking

Coupling &

Decoupling

Timing & Filters

DC Low Power

High Temperature

Timing, Filters

and Oscillating

Circuits


Self-Healing Property Metallized Film [Clearing Sequence]

Electrode with focused heat melts

Electrode heat causes film to melt

Liquid electrode disperses into melted film, short

opens

Electrode particles and film congeal

Short

Melted

Metallization

Metallization


Self-Healing in Metallized Film Dielectric Performance

• Low ratio between the number of Carbon (C) and Hydrogen + Oxygen

(H+O) atoms = Low Conductive Carbon Residues after Self-Healing

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6C/(H+O)

PPS PEN PET PP


EMI X2 Safety Capacitor Harsh Environment [PP vs. PET]

Polypropylene Polyester

• Very good performance in X2 safety (good

self-healing)

• Low dissipation factor

• Good capacitance stability

• Series and parallel connections are

feasible

• C/V is more efficient

• No impregnation is required

• Impregnation process is needed for

stability in series (only) construction

• High capacitance stability for impregnated

version

• Thick metallization

• High dissipation factor

• Larger ‘minimum’ size, due to lower BDV


Film Capacitor Market Demand TrendLong Life with High Stability & Reliability

IEC 60384-14 Am.1 Ed.4Fixed capacitors for use in Electronic Equipment

I.2 Humidity

Robustness Grades

Test Damp Heat,

Steady State at Rated

Voltage

Grade Test Condition A Test Condition B

I 40 °C / 93 % RH 21 days 85 °C / 85 % RH 168 h

II 40 °C / 93 % RH 56 days 85 °C / 85 % RH 500 h

III 60 °C / 93 % RH 56 days 85 °C / 85 % RH 1,000 h

Measurement Requirement

Capacitance |ΔC| ≤10 %

Dissipation Factor0,024 for CN ≤ 1 μF

0,015 for CN > 1 μF

Insulation Resistance >50 % of the applicable limits


Self-Healing Oxidation ErosionElectrochemical

Corrosion

Film Capacitance Degradation High Temperature, Humidity, and Voltage Bias (THB)

Capacitance Loss During Accelerated Life Test

𝑪𝒂𝒑𝒂𝒄𝒊𝒕𝒂𝒏𝒄𝒆𝑽𝒂𝒓𝒊𝒂𝒕𝒊𝒐𝒏(%

)

1,000 hours

Best

Performance

Fast

Degradation


Capacitance Decreasing MechanismsSelf-Healing & Corona (with Transient)

Key Parameters Self-Healing

• Polyproplylene dielectric (best)

• Metallization profile, material and thickness

• Exclusion of air and humidity during

manufacturing

Lost

Metal

Metal


Capacitance Decreasing MechanismsOxidation

Zn° ⇌ Zn2+ + 2 e- 2 Zn°+ O2 ⇌ ZnO

• Process active with or without presence of applied AC voltage

• Capacitance decrease is due to the metal oxidation

• Capacitors encapsulation in plastic box reduces significantly the

magnitude of this phenomenon


Capacitance Decreasing MechanismsErosion & Partial Discharges

• Active at low temperature

• Requires inception voltage

• Localized mostly where electric field is higher (metallization edge)

• It can be controlled with film thickness, moisture barrier, and special production process

No Metal

Metal

100% 60% 20%

No Metal


Capacitance Decreasing MechanismsElectrochemical Corrosion

Electrochemical Cell

Applied

AC Voltage

Air Gap

Induced

VoltageZn° → Zn2+ + 2 e-

2 H2O + 2 e- → H2 + 2 OH-

No Metal

Metal

• Reactions in the electrochemical cell

are driven by applied voltage.

• Corrosion rate is directly proportional

to temperature, humidity, and voltage

bias.

• Phenomena is controlled by

selecting special materials and

setting up a special production

process.


Film Capacitors For Harsh Environment Conditions

Special Film Material

Exclusive KEMET Resin Formulation

Optimized Case Sizes

Special Manufacturing Equipment

Special Controlled Compaction & Thermal Process

85 °C

85% R.H.

THB Test

F862 X2 F863 X2 C4AF AC Filter

(ΔC/C): ≤ 10%

1,000 hours

240 VAC

ΔTg < 5*10−3

@ 1 kHz

(ΔC/C): ≤ 10%

500 hours

240 VAC

ΔTg < 5*10−3

@ 1 kHz

ΔC/C | < 10%

500 hours

Vn

ΔTg < 3*10−3

@ 1 kHz


Film Capacitors For Harsh EnvironmentΔTlim vs. Ambient Temperature

• KEMET defines

maximum ripple

current, based on Hot-

Spot/Ambient self-

heating temperature.

• ΔT is reduced linearly

with increasing ambient

temperature, down to

0°C at 105°C

-5

0

5

10

15

20

25

0 10 20 30 40 50 60 70 80 90 100

ΔT

lim[°

C]

Ambient Temperature[°C]

F862 X2 Series

F862 X2 Series


Film Capacitors For Harsh EnvironmentEnvironmental Condition Reference

Three Defined Areas• Dry

• Harsh Environment

• Test

110

100

90

80

70

60

50

40

30

20

10

0

Tem

pera

ture

[°C

]

Dry

Condition

Harsh Environment

Condition

Test

Condition

0 10 20 30 40 50 60 70 80 90 100

Relative Humidity [%]


Permissible Current CapabilityDry vs. Harsh Environment

Harsh EnvironmentDry


Life Expectancy of Film TechnologyF862 – Life vs. Temperature and Voltage


Manufacturing Process


Plastic

Raw Roll

Metallization

Slitting

Film Preparation [Wound & Stacked]

• Thermal Stability

• Thickness

• Granulation

• Electrical and Mechanical

Specifications

Film Thickness (µm)

• PP ≥ 2.4

• PET ≥ 1.2

• PEN ≥ 1.4

• PPS ≥ 1.2


Dielectric Film Preparation

Plastic

Raw Roll

Metallization

Slitting

• Vacuum Chamber [Resistive Evaporation]

• Zinc, Aluminum, or Zinc Alloys

• Special Profiles and Treatments


• High Precision

• Cutting Widths Profiles

• Film Rewinding and Storage

Dielectric Film Preparation

Plastic

Raw Roll

Metallization

Slitting


• Single and Multi-Winding Systems

• Fast, Slow; Hot, Cold Flattening + Heat

• Taping Protects the Sides of the Elements

• Gas Flame or Electric Arc [Thick Metal Contact]

Wound TechnologyWinding to End Spraying

Winding

Flattening

& Heat Treatment

Protective

Taping

End

Spraying

Brushing


• Mother Winding [Frame]

• Frame Pressing

• Contact Metal Sprayed on Both Sides

• Multi-Cut System or One Element at a Time

Stacked Technology Winding to Element Cutting

Winding

Framing Flattening

SprayingBrushing

Heat Treatment& ElementCutting


• Automation with Combined Tasks

• Clearing Allow Potential Self-Healing

• 100% Tested for Critical Parameters

Welding to PackagingStacked and Wound

Welding &

Clearing

Encapsulation & Resin Filling

Measuring

Quality

Marking

Packaging


Thank You!

film capacitors - ec.kemet.com€¦ · resistance low high dv/dt high restriction self-healing no...

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