KEMET has been manufacturing conductive polymer based surface mount tantalum capacitors (KO-CAP[registered trademark]) since 1999. Capabilities have been successfully introduced into the market, such as low equivalent series resistance (ESR) series for decoupling, high voltage series for DC-DC converters and power management, and high-energy series for enterprise solid state drives (SSD) applications. A recent application trend of conductive polymer based tantalum capacitors requires high performance in harsh environments. One example is the application in the automotive industry which requires AEC-Q200 qualification. Amongst all of the AEC-Q200 requirements, the most challenging one for polymer tantalum capacitors with traditional technology is the highly accelerated test under 85 [degree]C / 85% relative humidity (RH) with DC bias up to rated voltage for 1000 hours. Other industries such as telecommunication are also starting to request 85 [degree]C / 85% RH qualification. A possible reason is an extrapolation based on data from other components that any device passing the 85 °C / 85% RH condition for 1000 hours could have field use life for 5 to 10 years under the real-life environmental conditions. In this paper, the basic construction and manufacturing process of polymer Ta capacitors is first described. The challenges for polymer Ta capacitors under unbiased and biased high temperature and high humidity conditions will be discussed. This will be followed by possible technical solutions and the performance of our current Polymer Electrolytic T598 series of products.

1. © KEMET Electronics 2015
Conductive Polymer Based Tantalum
Capacitor for Automotive Application
Name: Jane Ye
Date: 2015-10-26

2. © KEMET Electronics 2015
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

3. © KEMET Electronics 2015
KO-CAP Basic Construction

4. © KEMET Electronics 2015
KO-CAP Process
• More than 200 steps

5. © KEMET Electronics 2015
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
Capability
Developement
FOCUS
NOW

6. © KEMET Electronics 2015
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

7. © KEMET Electronics 2015
Challenges to Meet AEC-Q200
Stress Test Name Conditions
AEC -
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 ✓ ✓
Vibration
Mil-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

8. © KEMET Electronics 2015
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

9. © KEMET Electronics 2015
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
Epoxy
Epoxy
Negative
(-)
Positive
(+)
1 2
1
2

10. © KEMET Electronics 2015
Failure Analysis of High ESR
85° 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
Samples
ESR
Failures
Delamination and cracks of cathode material is responsible for
higher ESR parts

11. © KEMET Electronics 2015
DC Leakage Concern
KO-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
70
60
50
40
30
20
10
5
1
0.1
Leakage Current in µAmps
Percent
82 412
0HR AMB LKG
250HR AMB LKG
500HR AMB LKG
1000HR AMB LKG
Variable
DC leakage performance post 85°C 85%RH @ 0V
521D336M025/025 E060
High
Leakage

12. © KEMET Electronics 2015
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

13. © KEMET Electronics 2015
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 tosylate
solution 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

14. © KEMET Electronics 2015
Mechanism Summary
Swelling of
layer
Moisture
Adsorption
Crack
/ 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

15. © KEMET Electronics 2015
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

16. © KEMET Electronics 2015
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
70
60
50
40
30
20
10
5
1
0.1
% of Delta Cap
Percent
-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
Percent
10
0HR DF
250HR DF
500HR DF
1000HR DF
DF
DF performance post 85°C/85% RH @ 1 Vr
598D107M016/016 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
Percent
0.05 0.1
0HR ESR
250HR ESR
500HR ESR
1000HR ESR
Variable
ESR performance post 85°C/85% RH @ 1 Vr
598D107M016/016 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
Percent
160
0HR LKG
250HR LKG
500HR LKG
1000HR LKG
DCL
DC leakage performance post 85°C/85% RH @ 1 Vr
598D107M016/016 E050
Within initial
Specification

17. © KEMET Electronics 2015
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
70
60
50
40
30
20
10
5
1
0.1
% of Delta Cap
Percent
-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 @ 0.67Vr
598D107M016/016 E050
20151050
99.9
99
95
90
80
70
60
50
40
30
20
10
5
1
0.1
% DF
Percent
10
0HR DF
250HR DF
500HR DF
1000HR DF
DF
DF performance post 125°C @ 0.67Vr
598D107M016/016 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
Percent
0.05 0.1
0HR ESR
250HR ESR
500HR ESR
1000HR ESR
2000HR ESR
Variable
ESR performance post 125°C @ 0.67Vr
598D107M016/016 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
Percent
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

18. © KEMET Electronics 2015
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

19. © KEMET Electronics 2015
Thank You!
Team
Jane 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)

20. © KEMET Electronics 2015
For more information visit:
https://ec.kemet.com/wp1017