polymer (tantalum) capacitors...polymer (tantalum) capacitors design, characteristics, and...

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Polymer (Tantalum) Capacitors

Design, Characteristics, and Manufacturing

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Not All Tantalum Capacitors Burn

• All of the Caps on this board have failed.

– They are measured as shorts

MnO2 MnO2 MnO2 MnO2 MnO2

Poly Poly Poly Poly Poly

Test card with capacitors subjected to 2x Rated Voltage, applied with reverse polarity and > 20 amperes current capability.

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Design

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Tantalum Construction

Interconnected

Tantalum

Particles

Carbon Ink

Silver

Paint

Counter Electrode Penetration into Pores

(Manganese Dioxide (MnO2) or Conductive Polymer)

Ta2O5 Dielectric

Ta Metal MnO2 or

Cond. Poly.

Tantalum

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• Stable C(T,V), DCL(t)

• Reliable

• Efficient(CV/cc, E/cc)

C = kA/d

k = 27

.01 < d < .1 um

Ta

Ta2O5

Wet/MnO2/PolymerMilitary

Space

Medical

Automotive

Computers

Telecom

Ta

Ta2O5

SEM Ta Anode

Ta

Structure

Why use Tantalum?

TEM Oxide Dielectric

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InterconnectedTantalumParticles

Tantalum

Wire

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Anode: Tantalum

• Pros

– Resistant to chemical attack

– High melting point (2996C)

– Relatively Dense

• Cons

– Relatively expensive

– Less conductive than Ni or Al

• Ta 7.61 x 104 S/cm

• Ni 1.43 x 105 S/cm

• Al 3.77 x 105 S/cm

• Critical Characteristics

– Specific surface area (CV/g)

• Chemical impurities

– Oxygen

– Carbon

– Metallic impurities

• Physical characteristics

– Powder flow

– Crush strength

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TantalumParticles

Die Cavity

Volume

Sintered Pellet - All tantalum in electrical contact

Tantalum Wire

Sintering Tantalum into Pellet

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0.91

Tantalum

Wire

Ta2O5

Dielectric

Layer

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Dielectric: Tantalum Pentoxide Ta205

• Critical Characteristics– Dielectric constant

• 27.7

– Dielectric breakdown • VBDV 470 volt/mm)

– Dielectric thickness:• 2.0 nm/volt

– Resistant to chemical attack

Dielectric Thickness (nm)

VR Ta MLCC

2 20.7 600

4 27.6 600

6 36.8 600

Tantalum particle

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3

1.51

1.06


0.91

Tantalum

Wire

Ta2O5

Dielectric

Layer

Conductive polymer penetrates into

channels and surrounds Ta2O5

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106

105

104

103

102

101

100

10-1

10-2

MnO2

ConductivePolymers

Cathode: PEDT or MnO2

Cathode forms the negative connection:

• PEDT is a conductive organic polymer• MnO2 is Manganese Dioxide

PEDT

MnO2

13*US Patent #7,563,290

Polymerization Techniques

Slurry Polymer Process

Initial Polymerization

Insitu Polymer Process

MnO2MnO2

Existing KOExisting KO

50 100 150 200

100

150

50

Formation Voltage, V

BD

V,

V

0

Slurry

Insitu

BDV Comparison

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3

1.51

1.06


0.91

Carbon

Silver

Tantalum

Wire

Ta2O5

Dielectric

Layer

Conductive polymer penetrates into

channels and surrounds Ta2O5

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K – Solder Fused

B – Gold

C – Hot Solder Dipped

T – 100% Tin

H – Solder Plated

Terminations

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Polymer / Ta2O5 / TaSilver Adhesive

Carbon

Silver PaintWasher

Tantalum WireWeld

Leadframe

(- Cathode) Leadframe

(+ Anode)

Tantalum Surface-Mount Capacitor

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Standard (T520/T521) Facedown (T528)

Facedown (T527) Substrate (T488/T529)

Substrate ConstructionPackage Designs

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Production FlowElectrical Conditioning

• IR Reflow

– Place parts under an unbiased heat profile to precondition parts to

surface mount conditions

– Time, temperature

• Aging

– Application of elevated temp. / voltage to improve DC leakage

– 100% application

– Temperature

– Voltage

– Resistance

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Production Flow Testing

• 100% Electrical screen

– 85ºC DC leakage

– 25ºC DC Leakage

– Capacitance @ 120Hz

– Df @ 120Hz

– ESR @ 100kHz

– *Surge capability available, 100% on KO CAP

• SMT (Surface Mount Testing)

– Tollgate sampling of every batch

– Simulates customer board-mount

– A/R 0/1

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Different Package Options to meet the

customer’s need.

Custom requests welcome!

Modules – Targeting medical market

T560/ BMC – Approx 1in cube.

MAT – Low ESR with multiple anodes in a single package

Stacks – Utilizing both cathode systems. 2, 3 and 2x2 configurations.

PHS– Polymer Herm Seal – polymer cathode system – low ESR, stable cap at temperature and frequency.

HVE– Facedown is volumetrically efficientwith low inductance

Packaging

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Characteristics

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Standard vs. Polymer TantalumESR vs. Freq. vs. Temp

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Tantalum RC-Ladder

Surface Silver

Termination

tc1 = C1 x R1

tc2 = C2 x (R1+R2)

tcn = Cn x (R1+R2...+Rn)

Tantalum

Wire

MnO2R1 R2 Rn

C1 C2 Cn

Tantalum RC-Ladder

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Standard vs. Polymer TantalumCapacitance vs. Freq. vs. Temp

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Difference in Self-Healing

MnO2 Polymer

Current through fault

generates enough heat

and oxygen for ignition.

Conductive polymer

consumes oxygen

preventing ignition.

Tantalum Crack

Nickel

Ta Polymer

Polymer oxidized

Ta2O5

Crack

Nickel

Ta MnO2

Mn2O3

Ta2O5

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Voltage Derating Guidelines

• Typical derating guidelines:

• Tantalum MnO2: 50%

• Tantalum Polymer: 20%(>10V), 10% (≤10V)

• Aluminum Polymer: 0%!

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12

4

0

126%

Ta-Poly KO

VR>10VDC

6,310@100% VRated

FR(PPM)

1,700@90% VRated

FR(PPM)

458@80% VRated

FR(PPM)

9@50% VRated

FR(PPM)

0

0

0

0

235%

8

2

1

0

197%68%100 PPM FR

% VRated

Alum-Poly AOTa-Poly KO

VR≤10VDCTa-MnO2

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Thank You!

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Manufacturing

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Product Flow

Anode Pressing

Powder, wire, and lubricant, to mitigate tool wear, are added to cavity

Die Fill Compaction Pressed Anode

Anode

ManufacturingEncapsulation

Testing and

Finishing

Electro-Chemical

Processing

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Product Flow

Lubricant Removal & Sintering

Lubricant removal• Removes lubricant from tantalum powder compact (anode)

• Temperature 100º-600ºC in vacuum or by water wash

• Lubricant boils off at selected temp.

Key post-operation properties:

Carbon & oxygen content

Sintering• Employed to bond particles at temp. < M.P.

• Typically 1300º-2000ºC in vacuum

Key post-operation properties:Increased inter-particle connection (“neck size”) & physical strength porosity /surface area

Anode

ManufacturingEncapsulation

Testing and

Finishing

Electro-Chemical

Processing

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Anode

Manufacturing

Electro-Chemical

Processing

Product Flow

Racking

Sintered anodes welded to an Al process carrier bar

Key post-operation properties:

Weld strength

Rack height

Tight tolerances guarantee subsequent

processing consistent for all anodes

EncapsulationTesting and

Finishing

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Anode

Manufacturing

Electro-Chemical

Processing

Product Flow

Dielectric Formation

Interconnected Tantalum Particles

Ta2O5

Dielectric

Layer

+ -

Electrolyte Solution

Tantalum particle

Ta2O5


Finishing

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Product Flow

MnO2 Impregnation / Polymerization

Sintered tantalum particles

Ta2O5

Dielectric

Layer

MnO2/Poly.

Key post-processing properties:Capacitance recovery (coverage of dielectric surface) Dissipation factor (continuity, conductivity of internal layer)Equivalent series resistance (continuity, conductivity of cathode)

Anode

Manufacturing

Electro-Chemical

ProcessingEncapsulation

Testing and

Finishing

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Product Flow

Carbon Ink

Carbon ink properties:

ConductiveIsolates silver from MnO2

Critical for low ESR

Sintered Ta Particles

Ta2O5

Dielectric

Moisture

Barrier

Silver paint properties:ConductiveMechanical strengthStable through IR passes

Anode

Manufacturing

Electro-Chemical

Processing

Moisture barrier properties:Moisture resistant layerInhibits ionic migration

MnO2

Carbon

Ink

Silver

Paint


Finishing

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Components

1) Silver Adhesive

2) Processed Anodes

3) Leadframe

Anode

Manufacturing

Electro-Chemical

Processing

Product Flow

Assembly


Finishing

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Components

1) Epoxy Pellets

2) Assembled Leadframe

Anode

Manufacturing

Electro-Chemical

Processing

Product Flow

Molding


Finishing

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Anode

Manufacturing

Electro-Chemical

Processing

Product Flow

Deflash / Print / Dejunk (DPD)

• Deflash

– Remove excess epoxy from leads

• Print/Laser Marking

– Laser-mark parts for identification

• Dejunk

– Singulate the negative side of the lead frame strip


Finishing

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Anode

Manufacturing

Electro-Chemical

Processing

Product Flow

Electrical Conditioning

• IR Reflow

– Place parts under an unbiased heat profile to precondition parts to surface mount conditions

• Time, temperature

• Aging

• Application of elevated temp. / voltage to improve DC leakage

• 100% application

– Temperature

– Voltage

– Resistance


Finishing

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Anode

Manufacturing

Electro-Chemical

Processing

Product Flow

Testing

• 100% Electrical screen

– 85ºC DC leakage

– 25ºC DC Leakage

– Capacitance @ 120Hz

– Df @ 120Hz

– ESR @ 100kHz

– *Surge capability available, 100% on KO CAP

• SMT (Surface Mount Testing)

– Tollgate sampling of every batch

– Simulates customer board-mount

– A/R 0/1


Finishing

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Anode

Manufacturing

Electro-Chemical

Processing

Product Flow

Lead Form and Tape

1st

Lead Form

2nd

Lead Form

3rd

Lead Form

Formed parts are placed in carrier tape for packaging and shipment


Finishing

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Thank You!

polymer (tantalum) capacitors...polymer (tantalum) capacitors design, characteristics, and...

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