NEPP ETW 2018: Can Chip Polymer Tantalum Capacitors ......Workshop, Greenbelt, MD, June 2018 AC...

Can Chip Polymer Tantalum Capacitors Manufactured to AEC-Q200 Requirements

be used for Space Applications?

Alexander TeverovskyAS&D, Inc.

Work performed for Parts, Packaging, and Assembly Technologies Office,

NASA GSFC, Code [email protected]

NASA Electronic Parts and Packaging (NEPP) Program

List of Acronyms

To be presented by A.Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 2018

AC alternative current HTS high temperature storage

AEC automotive electronic council MC molding compound

C capacitance NT new technology

COTS commercial off the shelf OCM original component manufacturer

CPTC chip polymer tantalum capacitors QA quality assurance

DF dissipation factor RT room temperature

ESR equivalent series resistance S&Q screening and qualification

FPGA field-programmable gate array SCD source control drawing

HALT highly accelerated life testing WGT Weibull grading test

2

Abstract


3

This presentation analyses quality assuranceapproaches used by automotive industry and usingpolymer tantalum capacitors as an example, reviewspossible ways of COTS insertion in space systems.Specifics of polymer tantalum capacitors in comparisonwith traditionally used MnO2 tantalum capacitors arediscussed.

Outline

Significance of COTS and automotive industry components for space applications.

What are polymer tantalum capacitors? Specifics of CPTCs as compared to MnO2 capacitors.

How to assure reliability for parts with degrading parameters? (ESR degradation in CPTCs)

Anomalies in behavior of CPTCs. How to mitigate risks of using CPTCs for space?


4

Processes of AEC-Q Parts Insertion


5

Are automotive parts COTS components? COTS = non-MIL? or COTS = non-SCD? Automotive parts = parts compliant with AEC-Q?

Two approaches for COTS insertion:1. Reliability of COTS is inferior to MIL parts, and to qualify for space

extensive testing per the existing requirements are necessary.• The major concern is cost and time of qualification rather than

technical issues.2. COTS are NT devices.

• New mechanisms might require new testing techniques.• Existing procedures for S&Q have to be evaluated and adjusted.

“COTS as NT” approach requires understanding of new degradation mechanisms, specific reliability issues, and development of adequate S&Q procedures.

The consistency of COTS quality still remains a problem.

Components for Space are Coming from the COTS World


6

Future cars will be sensors and computers on wheels.

The cost of cars will be mostly dueto electronics.

Automotive components is the fastest growing market, ~10%/year.(→ Current shortage of components; OCMs are running at full capacity.)

Requirements for automotive components are comparable to MIL and these parts are the first choice for selection for space.

Temp from -40 ºC to +165 ºC Vibration 0-2000Hz Acceleration up to 50g Life time 10-15 years (mostly non-operational);

self-driving cars: 1-2 years intensive operation

A. Aal, Volkswagen, IRPS’17

http://green-electronic-tutorial.blogspot.com/2018/04/.html

What Components are Used in Cars?


7

B. Knoell, AEC chair: there is a need to use an appropriate mixture of qualification methodologies:

●Stress Test per AEC-Q Specs. ●Step-stress testing. ● Application-Specific tests.●Physics-of-Failure approaches. ●Sequential Stress Tests. ●Board Level Reliability.

A. Aal, Volkswagen: reliability issues should be resolved by working together with components’ manufacturers. AEC-Q is only one aspect of the total quality management system. Detailed analysis of QA of manufacturing process. 30-50% of failures were due to material/process changes (notification process). Multi-mode stresses, rather than operation hours kill lifetime. Assembly affects parameters of thin dielectric ICs.

Using AEC-Q Components for Space


8

Automotive industry does not use AEC-Q parts without substantial additional testing and analysis working with OCMs.

Car manufacturers have significant leverage, but require high reliability for low price.

Space community might not have a similar leverage, but we do not have cost as a priority.

We can benefit from AEC-Q by using compliant part as a baseline and developing a knowledge-based system for parts’ selection, S&Q.

Why CPTCs?


9

Major benefits: Better volumetric efficiency (smaller case sizes); Higher operating voltages (up to 125V); Lower ESR (milliohm range); A relatively safe failure mode (no ignition). CPTCs are less likely to fail short circuit and are more likely to pass life testing

per MIL-PRF-55365 compared to MnO2 COTS capacitors.

Major drawbacks: Effect of environments: both, excessive and insufficient amount of moisture

might be detrimental; vacuum can be a benefit or a hazard. The core element of S&Q for MnO2 capacitors, WGT, is not applicable. ESR might degrade with time at high temperatures (HTS testing for QA). New phenomena: anomalous transients.

Substantial efforts have been made to demonstrate compliance of CPTCs with AEC-Q200. Currently: Tstorage up to 150ºC and 85ºC/85% RH/1000hr biased.

Breakdown in MnO2

capacitors

What are CPTCs?


10 No significant differences in design except for cathode materials.

Lead frame

MnO2

MnO2

Ta

Lead frame

carbon

PEDOT:PSS

Ag paint

polymer

Ta2O5

Nardes et.al 2008

Specific of CPTCs: ESR Degradation


11

Contrary to MnO2, CPTCs might degrade substantially during HTS. Can compliance to AEC-Q200 guarantee end-of-life ESR values?

0

50

100

150

200

250

300

0 200 400 600 800 1000

ESR

, mO

hm

time, hr

HTS 150C CWR29FC686KBGA, DC0703, ESR_max=275 mohm

1.E+1

1.E+2

1.E+3

1.E+4

0 4000 8000 12000

ESR,

moh

m

time, hr

HTS125

CPTC-1

CPTC-2

1.E+1

1.E+2

1.E+3

1.E+4

0 4000 8000 12000

ESR,

moh

m

time, hr

HTS100

CPTC-1

CPTC-2

MnO2 polymer

0

20

40

60

80

100

120

0 200 400 600 800 1000

ESR

, moh

m

time, hr

220uF 10V Mfr.B at 85C 85%RH

0

20

40

60

80

100

120

140

0 200 400 600 800 1000

ESR,

moh

m

time, hr

85C 85% RH

CPTC-G2

CPTC-G3

Mfr.

m

argi

nde

sign

er

mar

gin

Modeling of ESR Degradation

12

Simulations allow for the end-of-life predictions. More complex models might be necessary for lots having

different degradation inception times.

Approximations: ( )τtESRESR exp0 ×=

−−=

β

ηττ exp1)(P

Polymer Ta 10uF 25V at HTS

tau, hr

cumula

tive p

robab

ility, %

10 1000000100 1000 10000 1000001

5

10

50

90

99

use level55C

100C125C

150C175C

5000hr

990hr

300hr

150hr

1.E+1

1.E+2

1.E+3

1.E+4

1.E+5

0 1000 2000 3000 4000 5000

ESR

, moh

m

time, hr

Polymer Ta 10uF 25V at HTS100C125C150C175C

τ =


Ea = 0.72eV

𝜏𝜏 = 𝜏𝜏0 × 𝑒𝑒𝑒𝑒𝑒𝑒 �𝐸𝐸𝑎𝑎𝑘𝑘𝑘𝑘

Mechanism of ESR Degradation


13

ESR degradation is due to thermo-oxidative processes in conductive polymers → better stability in vacuum.Contrary to MnO2 capacitors, cracks in CPTCs are more likely to

cause ESR failures. Quality of packaging is critical for reduction of ESR degradation. Parts manufactured to AEC-Q200 have a better packaging control.

CPTCs after HTSDiscoloration of MC indicates the pass

of O2 causing decomposition.Oxygen penetrates along the lead

frame-MC interface.Parts with less decomposition around

Ta slug have less degradation.Cracks accelerate ESR degradation.

crack

Decomposition of MC

Specific of CPTCs: Life Testing


14

Reliability of CPTCs during life testing is comparable or better than for MnO2 parts.

Contrary to MnO2 caps that might fail short circuit, CPTCs are more likely to cause current spiking (not addressed by the existing S&Q).

1.E-07

1.E-06

1.E-05

1.E-04

1.E-2 1.E-1 1.E+0 1.E+1 1.E+2

curre

nt, A

time, hr

220uF 16V HALT at 165C, VR

1.E-07

1.E-06

1.E-05

1.E-04

0.01 0.1 1 10 100

curre

nt, A

time, hr


1.E-07

1.E-06

1.E-05

1.E-04

0.01 0.1 1 10 100

curre

nt, A

time, hr


No short circuit failures during step stress life test up to 165 ºC

0.E+0

1.E-6

2.E-6

3.E-6

4.E-6

5.E-6

0 50 100 150 200

curre

nt, A

time, hr

33uF 35V at 85C 35V

1.E-7

1.E-6

1.E-5

0 200 400 600 800 1000

curre

nt, A

time, hr

100uF 20V at 125C 20V

0.0E+0

5.0E-7

1.0E-6

1.5E-6

2.0E-6

0 20 40 60 80 100

curr

ent,

A

time, hr

68uF 10V at 85C, 10V

Spiking of the current that might cause noise generation

Specifics of CPTCs: Anomalous Transients


15

0

5

10

15

20

25

30

35

0

0.5

1

1.5

2

2.5

3

0 0.2 0.4 0.6 0.8 1cu

rren

t, A

curr

ent,

A

time, msec

100uF 10V

HUMBAKE SN2BAKE SN3

1.E-8

1.E-7

1.E-6

1.E-5

1.E-4

10 100 1000cu

rren

t, A

time, sec

33uF 35V CPTC-1

240hr 125C240hr 85-85virg

1.E-9

1.E-8

1.E-7

1.E-6

1.E-5

1.E-4

1.E-3

1.E-2

-80 -60 -40 -20 0 20 40 60 80 100 120 140

curr

ent@

1000

s, A

temperature, deg.C

22uF 25V

HUM

virgin

BAKE

0.3eV

1.E-9

1.E-8

1.E-7

1.E-6

1.E-5

1.E-4

1.E-3

0.0025 0.003 0.0035 0.004 0.0045 0.005

curr

ent,

A

1/T, 1/K

CPTC 10uF 35V

1wk 125C1wk 85-85virgin

Preconditioning affects transient currents from milliseconds to hours. Behavior of CPTCs with moisture is similar to MnO2 caps. At RT dry CPTCs might have currents >103 times greater than humidified caps. Contrary to MnO2 capacitors, leakage currents at low

temperatures in dry CPTCs might increase up to 106 times.

Effect of Vacuum


16

0.0001

0.001

0.01

0.1

1

-55 -25 5 35 65 95 125

curre

nt, A

temperature, deg.C

22uF 35V

10 msec

1 sec

1.E-4

1.E-3

1.E-2

1.E-1

1.E+0

0.001 0.01 0.1 1 10

curre

nt, A

time, sec

33uF 25V -55C -45C-35C -25C-15C -5C+5C +20C+35C +45C+55C +65C+85C +105C+125C

1.E-5

1.E-4

1.E-3

1.E-2

1.E-1

1.E+0

0.01 0.1 1 10 100

curre

nt, m

A

time, min

33uF 25V

+20C, init100hr at 20C350hr 20C, 260hr 85C400hr 20C, 700hr 85C

1.E-5

1.E-4

1.E-3

1.E-2

1.E-1

1.E+0

0.01 0.1 1 10 100

curre

nt, m

A

time, min

150uF 10V in vacuum

init100hr at 20C350hr 20C, 260hr 85C400hr 20C, 700hr 85C

1.E-4

1.E-3

1.E-2

1.E-1

1.E+0

0.01 0.1 1 10 100

curr

ent,

mA

time, min

150uF 10V, 2000hr in vac

-50C -35C-20C 0C 20C 35C 50C 85C

Anomalous transients appear with time in vacuum. Inverse temperature dependence of leakage currents.

Short- and long-term transients might have different mechanisms.

Anomalies in AC Characteristics


17

25

30

35

40

45

50

0 5 10 15 20 25 30 35 40

capa

cita

nce@

1kHz

, uF

voltage, V

CPTC-1 33uF 35V

240hr 125C

240hr 85-85

0

0.5

1

1.5

2

2.5

0 5 10 15 20 25 30 35 40

ESR@

1kHz

, oh

mvoltage, V

CPTC-1 33uF 35V

240hr 125C

240hr 85-85

0.1

1

10

100

1 10 100 1000

DF, %

time, sec

CPTCs after vacuum storage

33uF 25V330uF 6.3V220uF 16V

y = 58.031x-0.62

0.1

1

10

100

1 10 100 1000

DF, %

time, sec

10uF 35V after bake

CPTC-9, 0VCPTC-9, 35VCPTC-4, 35VCPTC-4, 0V

Similar to MnO2 caps, wet CPTCs have stable AC characteristics.C, ESR, and DF are increasing with voltage in dry CPTCs. DF in CPTCs after drying can increase well above 10% and then decrease gradually with time.

Anomalous Transients: Effect of Part Type


18

00.5

11.5

22.5

33.5

44.5

5

0 0.2 0.4 0.6 0.8 1

curre

nt, A

time, msec

CPTC after 2000hr in vacuum

220uF 16V 33uF 25V330uF 6.3V 10uF 35V22uF 35V

0.2eV

1.E-9

1.E-8

1.E-7

1.E-6

1.E-5

1.E-4

0.0025 0.003 0.0035 0.004 0.0045

curre

nt, A

1/T, 1/K

10uF 35V after 150hr at 125C

modified

standard

Different part types have substantially different levels of transient currents.

Currently, no specific tests evaluate the level of transients. Modification of polymers can practically eliminate anomalies in

behavior of CPTCs.

Conclusions and Future Work

19To be presented by A.Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 2018

To use CPTCs that are compliant with AEC-Q200 for space:Designers should be aware of possible degradation and

anomalies in the parts and determine acceptable levels.The level of degradation, current spiking and anomalous

transients is limited by adequate S&Q procedures.Voltage derating should be 50% instead of 80% suggested by

manufacturers. Future work on CPTCs: Kinetics of moisture sorption and desorption at different temperatures; Modeling of ESR degradation; Effect of long-term exposure to vacuum and HTS on current spiking and

anomalous transients; Radiation hardness. Guidelines for applications and parts’ selection.

NEPP ETW 2018: Can Chip Polymer Tantalum Capacitors ......Workshop, Greenbelt, MD, June 2018 AC...

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