Requirements for Power Conversion Devices for the Computer and Telecommunications Industries

IPC-9592A Derating Guidance

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Alessandro A. (Alex) CervoneTechnical Manager – Component Reliability & EngineeringGE Energy – Power Electronics601 Shiloh RoadPlano, Texas 75074

Applied Power Electronics Conference (APEC)Orlando, Florida – February 8, 2012

Derating Guidance

Proper derating can mitigate premature wear-out of electronic components in the power circuits.

Recommended standard derating factors outlined in IPC-9592B Section 4.3 and Appendix A.

Wear out and examples of life estimation for MLCC and aluminum electrolytic capacitors used in filter applications will be discussed

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Appendix A - What’s Changed?

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MLCC Voltage derating from 80% to 90% Allow sizes > 1210 if flexible terminations Life Estimation per Prokopowicz and

Vaskas (PV Equation)

Fixed Aluminum Electrolytic Add ripple current derating of 80%

Appendix A - What’s Changed?

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Power MOSFET Avalanche allowed for Vds rating below

200V Added dv/dt rating

Power Magnetics Derating according to temperature rise

MLCC Life EstimationStructure of MLCC

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Ceramic (BaTiO3) Electrodes

PME (Pd) BME (Ni)

MLCC Life EstimationCeramic – Perovskite Crystal

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Barium Titanate (BaTiO3) Provides highest possible

dielectric constant Easy to Manufacture Environmental friendly

MLCC Life EstimationMarket Demands for Higher Density

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Miniaturization and volumetric efficiency Thinner dielectric layers Higher layer count

Lower Cost Replace Pd with Ni electrodes

MLCC Life EstimationUnintended Consequences

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To avoid oxidation of Ni electrodes during firing, manufacturers must use inert atmosphere

Thinner dielectric suffers degradation of insulation resistance due to Voltage stress Temperature stress

MLCC Life EstimationOxygen Vacancy

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Oxygen atom may be removed from lattice during firing Results in an oxygen

vacancy

MLCC Life EstimationWear-out due to Oxygen Vacancy Migration

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Oxygen vacancies are positively charged and tend to migrate towards the cathode

Oxygen vacancy migration accelerates with increased voltage and temperature

Resultant reduction in insulation resistance (due to increased charge accumulation and temperature rise) will lead to a short circuit

MLCC Life EstimationP-V Equation1

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t1t2

V2V1

n

expEaK

1T1

1T2

Where:t1 = time to failure under test conditionV1 = voltage under test conditionN = voltage stress exponentialEa = activation energy of dielectric wear outk = Baltzmann’s constantT1 = absolute temperature for test condition

1 Prokopowicz and Vaskas

MLCC Life EstimationHALT Data

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In order to use the PV equation, we require some constants that are determined by accelerating the wear-out at high temperature and high voltage (HALT) which must be provided by device manufacturer.

MPN Type size cap BV Theta nTest

temp Test

Voltage

B1 Life (hrs)

Time to 1% fail at rated

T/V (yrs)nnnnnnnnnnnnnnnnnnn X5R 0805 22 6.3 6.6 4.1 150 13 0.8 1.6nnnnnnnnnnnnnnnnnnn X5R 1206 47 6.3 6.6 4.1 150 13 2.2 5nnnnnnnnnnnnnnnnnnn X5R 1210 100 6.3 8 5 150 12.6 14 14.3nnnnnnnnnnnnnnnnnnn X5R 0603 4.7 6.3 6.6 4.1 150 12.6 1.05 1.9

Aluminum Electrolytic Life Estimation

Lx L0 2

T0 Tx

10 2

T 0 T x

8V0Vx

n

Where:T0 = Max usage temperature Tx = Capacitor local ambient in use conditions∆T0 = Core temperature rise at T0 with max ripple current∆Tx = Core temperature rise at Tx with actual ripple currentL0 = Base lifetime of capacitors (hours)Lx = Capacitor life to be estimated (hours)V0 = Capacitor rated voltageVx = Actual operating voltage applied to capacitorn = 4.4 For snap-in typen = 2 for radial where ΦD≤10mm or L≤20mm

2From Samxon Aluminum Electrolytic Application Guidelines

Aluminum Electrolytic Life Estimation

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Core temperature is key to proper lifetime estimation

Have manufacture build a sample with thermo-couple buried inside core

Aluminum Electrolytic Life EstimationExample

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25C

Component Description Component Specifications Stress in ApplicationEstimated

Life

Ref Des Type Cap. (uF)

Rated Voltage V0 (V)

Case Size

ΦDxL

Temp. Rating T0 (°C)

△T0 (ºC)

Base Lifetime L0 (Hrs)

Actual operating voltage Vx (V)

Ambient

Temp

Tx(°C)

Temperature

rising. Tx △

(°C)

n Lx (Hrs)

Lx (Year

s)

C204 nnnnnnnnnnnn 220 450 25*30 105 5 2000 425 29.12 6.89 4.4 420098 48.0

40CC204 nnnnnnnnnnnn 220 450 25*30 105 5 2000 425 44.25 6.1 4.4 15762

3 18.0

50CC204 nnnnnnnnnnnn 220 450 25*30 105 5 2000 425 54.77 5.79 4.4 78091 8.9

Test conditions: 230Vac /52V /30.9A

                           

Conclusions

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Derating electronic components mitigates risk of premature wear out.

Lifetime estimation is recommended for MLCC’s, when used in filter applications (with high RMS current) - 20○C max due to self heating

Aluminum electrolytic capacitor core temperature is key to lifetime estimation

References

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[1] T. Prokopowicz and A. Vaskas, “Research and Development, Intrinsic Reliability, Subminiature Ceramic Capacitors,” Final Report, ECOM-9705-F, 1969 NTIS AD-864068

[2] Life Calculation of Aluminum Electrolytic Capacitor – Man Yue Electronics Co., LTD