Construction and Test Results for Automotive Conductive Polymer Capacitors

© KEMET Electronics 2015

Conductive Polymer Based Tantalum

Capacitor for Automotive Application

Name: Jane Ye

Date: 2015-10-26


Conductive Polymer Based Tantalum

Capacitor for Automotive Application

• Introduction of KO-CAP®

• Development Roadmap and Target

• Technical Challenges

• Solutions and Results

• Path Forward

KO-CAP is a registered trademark of KEMET Electronics Corporation.

KEMET Organic Polymer Electrolytic Capacitors


KO-CAP Basic Construction


KO-CAP Process

• More than 200 steps


Automotive Initiative Roadmap

2013 2014 2015 2016…

T591 Series• 125ºC/105ºC/85ºC

• SMD

• Low ESR

• High ripple current capability

• Benign failure mode

• 85ºC/85%RH 500 Hours

T598 Series• 125ºC

• SMD

• Low ESR

• High ripple current capability

• Benign failure mode

• 85ºC/85%RH 1000Hours

• Full AEC-Q200

T599 Series

•150ºC capability

•SMD

• 85ºC/85%RH 1000Hours

• Full AEC-Q200

Cap

ab

ilit

y

Develo

pem

en

t

FOCUS

NOW


Development Target

• 3000 to 5000 Capacitors per vehicle

Communication / Navigation

Entertainment Systems

Driver Convenience

Power Train

Vehicle Lighting

Safety Systems

T591

T591

T591

T598/T599

T598/T599

T598/T599


Challenges to Meet AEC-Q200

Stress Test Name ConditionsAEC -

Q200

KO

Commercial

High Temp Exposure (Storage) 125° C, Unbiased, 1000 Hrs depends

Temperature Cycling -55° C to 125° C, 1000 Cycles

Biased Humidity 85° C, 85% RH, Biased, 1000 Hrs

Operational Life 125° C, Biased, 1000 Hrs depends

Resistance to Solvents Mil-Std-202, Meth. 215

Mechanical Shock Mil-Std-202, Meth. 213, Cond F

VibrationMil-Std-202, Meth. 208, 5G’s-

20min

Resistance to Soldering Heat Mil-Std-202, Meth. 210, Cond D

ESD AEC-Q200- 002 or ISO/DIS 10605

Solderability J-STD-002

Terminal Strength AEC Q200-006

Ref. 11 Jayson Young and Javaid Qazi, Polymer Tantalum Capacitors for Automotive Applications CARTS International 2014


ESR Concern under 85° C, 85% RH, Biased

• Example of KOCAP EIA 7343-28 33uF 25V

• Greater ESR shift than that under 60° C, 90% RH, Biased

ESR Shift

521D336M025 E060


Failure Analysis of High ESR

85° C, 85% RH, Biased

• Typical Example EIA 7343-28 33uF 25V ESR0.06Ω

• Post test ESR reading > 0.1Ω at 100kHz

• Delamination and crack were detected

Delamination Tantalum

PEDOT

Carbon

Silver

Crack

EpoxyEpoxy

Negative

(-)Positive

(+)1 2

12


Failure Analysis of High ESR85° C, 85% RH, Biased

• Typical Example of EIA 7343-28 33uF 25V ESR 0.06Ω

• Post test ESR reading > 0.1Ω at 100kHz

• Delamination confirmed with ion milling cross section SEM by

NEC-Tokin lab

• Good connection of good ESR or improved samples

X 40 X10,000

Ion milling

Mechanical polishing

X10,000

Improved

SamplesESR

Failures

Delamination and cracks of cathode material is responsible for

higher ESR parts


DC Leakage ConcernKO-CAP 85° C, 85% RH, Biased

• KOCAP 7343-28 33uF 25V 0.06ESR

• Leakage tailed up to 0.5CV

• Short circuit occurred in extreme cases

1000010001001010.10.010.001

99.9

99

95

90

80

7060504030

20

10

5

1

0.1

Leakage Current in µAmps

Pe

rce

nt

82 412

0HR AMB LKG

250HR AMB LKG

500HR AMB LKG

1000HR AMB LKG

Variable

DC leakage performance post 85°C 85%RH @ 0V521D336M025/025 E060

High

Leakage


Cu & S

Cu & S

S

S

Cu & S

S

Leadframe, Ta wire

and top of anode

Epoxy fractured off

of areas shown at left

Failure Analysis of High Leakage/Short 85°C, 85% RH, Biased

The Cu found in the Ta wire imprint appeared typical of a

migration pattern usually found as a result of moisture

penetration in a biased part

Leadframe

Anode

Ta

wire


Simulation of Copper Migration PCT 121C° C 85%RH 1.7 Atmosphere for 42Hrs

• EIA 7343-28 33uF 25V ESR 0.06Ω– 64 pieces

• Assembled with copper alloy based leadframe before encapsulation

• A low concentration of ferric tosylatesolution was applied to the strips and dried to simulate the chemical residuals from polymerization of PEDOT

• Pre-treated strips were placed into a chamber of 121 C 85% RH with a pressure of 1.7 atmosphere for 42Hrs. 0.67Vr applied

• Electrically and Physically Inspected Cu

Good

42% Short-circuited

Leadframe corrosion and copper migration was observed


Mechanism Summary

Swelling of

layer

Moisture

AdsorptionCrack

/ GAP

De-

depoing

with DC

ESR

Failures

Ion

dissolution

(Cl, Ferric)

Anodic of

Copper with

DC

Copper ion

move to

cathode

Copper ion

reduction

to metal

Dendrites

growth

Short

Circuit

Conductor

bridge

(Path)

CTE/CME Stress

Moisture


Design Actions Implemented

• Factor 1: Moisture

– 1) Use lower moisture permeability mold compound

– 2) Optimize the application of moisture barrier to polymer capacitors

• Factor 2: Ionic Contaminations

– 3) Further optimize wash process

– 4) Reduce ionic species in molding

• Factor 3: Leadframe Substrate

– 5) Use alloy with less copper content, more resistant to corrosion

• Factor 4: Distance between conductors

– 6) Improve the wire laser clean technology


Improvement Results 85° C, 85% RH Biased, 1000 Hours

• Example of EIA7343-28 100uF 16V ESR 0.05Ω

403020100-10

99.9

99

95

90

80

7060504030

20

10

5

1

0.1

% of Delta Cap

Pe

rce

nt

-5 35

250HR DCAP

500HR DCAP

1000HR DCAP

DCAP

598D107M016/016 E050

Delta Cap performance post 85°C/85% RH @ 1 Vr

20151050

99.9

99

95

90

80

70

60

50

40

30

20

10

5

1

0.1

% DF

Pe

rce

nt

10

0HR DF

250HR DF

500HR DF

1000HR DF

DF

DF performance post 85°C/85% RH @ 1 Vr598D107M016/016 E050

0.200.150.100.050.00

99.9

99

95

90

80

70

60

50

40

30

20

10

5

1

0.1

ESR in Ohms

Pe

rce

nt

0.05 0.1

0HR ESR

250HR ESR

500HR ESR

1000HR ESR

Variable

ESR performance post 85°C/85% RH @ 1 Vr598D107M016/016 E050

1000010001001010.10.010.001

99.9

99

95

90

80

70

60

50

40

30

20

10

5

1

0.1

DC Leakage Current in µAmps

Pe

rce

nt

160

0HR LKG

250HR LKG

500HR LKG

1000HR LKG

DCL

DC leakage performance post 85°C/85% RH @ 1 Vr598D107M016/016 E050

Within initial

Specification


Improvement Results 125°C 0.67Vr 1000 Hours

• Example of EIA7343-28 100uF 16V ESR 0.05Ω

151050-5-10-15-20-25

99.9

99

95

90

80

7060504030

20

10

5

1

0.1

% of Delta Cap

Pe

rce

nt

-20 10

-1.890 0.1939 100 0.420 0.320

-2.491 0.2088 100 0.330 0.510

-3.396 0.2767 100 0.815 0.034

Mean StDev N AD P

250HR DCAP

500HR DCAP

1000HR DCAP

DCAP

Delta Cap performance post 125°C @ 0.67Vr598D107M016/016 E050

20151050

99.9

99

95

90

80

70

60

50

40

30

20

10

5

1

0.1

% DF

Pe

rce

nt

10

0HR DF

250HR DF

500HR DF

1000HR DF

DF

DF performance post 125°C @ 0.67Vr598D107M016/016 E050

0.200.150.100.050.00

99.9

99

95

90

80

70

60

50

40

30

20

10

5

1

0.1

ESR in Ohms

Pe

rce

nt

0.05 0.1

0HR ESR

250HR ESR

500HR ESR

1000HR ESR

2000HR ESR

Variable

ESR performance post 125°C @ 0.67Vr598D107M016/016 E050

1000010001001010.10.010.001

99.9

99

95

90

80

7060504030

20

10

5

1

0.1

DC Leakage Current in µAmps

Pe

rce

nt

160 320

0HR AMB LKG

250HR AMB LKG

500HR AMB LKG

1000HR AMB LKG

LKG

598D107M016/016 E050

DC leakage performance post 125°C @ 0.67Vr


Path Forward

• Expand the T598 product line with additional part

numbers

• Develop a new series (T599) that has 150 C 1000 hour

life in addition to the specification of T598 in the near future

• Enlarge the application of tantalum polymer capacitor in

the automotive and other market where harsh operating

environment is of concern


Thank You!

TeamJane Ye, Manager of KO-CAP NPD (Suzhou)

Chris Stolarski, Director of Spec. Platform and

Ta Powder Development (USA)

Mel Yuan, Chief Development Engineer (Suzhou)

Cristina MotaCaetano, Director of Ta Technical

Marketing (USA)


For more information visit:

https://ec.kemet.com/wp1017

https://ec.kemet.com/wp1017

Engineering

Construction and Test Results for Automotive Conductive Polymer Capacitors