2014 NEPP Tasks Update for Ceramic and Tantalum Capacitors
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
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
https://ntrs.nasa.gov/search.jsp?R=20150000205 2018-06-08T07:33:26+00:00Z
List of Acronyms and Symbols
2Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
AF acceleration factor MLCC multilayer ceramic capacitorBME base metal electrode MSL Moisture sensitivity level
C capacitance PME precious metal electrodeDCL direct current leakage PV Prokopowicz-VaskasDF dissipation factor S&Q screening and qualification
DWV dielectric withstanding voltage STD Standard deviationESR Equivalent series resistance T temperatureHALT highly accelerated life testing THB temperature, humidity, biasHSSL humidity steady state low voltage TSD terminal solder dip
HT High temperature TTF time to failureHV high voltage VBR breakdown voltageIM Infant mortality VBR75 third quartile of VBR distribution
IR insulation resistance VO++ charged oxygen vacancy
LV low voltage VR rated voltage
Outline
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Update on tantalum capacitors. MnO2 chip capacitors. Advanced wet capacitors. Polymer capacitors. Future work.
Update on ceramic capacitors. Low-voltage failures in MLCCs. IR degradation of BME capacitors caused by oxygen
vacancies. The significance of breakdown voltages for quality
assurance of BME capacitors. Effect of soldering. Future work.
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
New Technology Tantalum Capacitors
MnO2
KEMET F-process
AVX Q-process
Low ESL, multianode, stacked, …
microchips
embedded
Wet
SuperTan, TWA
Hybrid
Supercapacitors
Polymer
LV molded chips
HV molded chips
Hermeticallysealed
Specifications:military, SCD,
medical, automotive
Diversity is due to the variety of cathode systems.A general trend: reduction of size and ESR, increase in C, VR, and Toper.New technologies appear with increasing speed.Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
4
Diversity of Tantalum CapacitorsTechnologies similar to Ta:
Nb/Nb2O5 and NbO/Nb2O5
Updates on MnO2 Tantalum Capacitors
5
Projects problems with capacitors appear with ~constant rate. Deficiencies in M55365 and new screening processes are in line with
NEPP recommendations.KEMET F-technology – importance of VBR.AVX Q- technology – Weibull grading, HT DCL, reflow…
Pop-corning and MSL.
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
15 uF 50 V
0
50
100
150
200
250
0 10 20 30time, min
tem
pera
ture
, oC
-1001020304050607080
defo
rmat
ion,
um
cycle 1 Tcycle 2 Tcycle 1 dcycle 2 d
0
0.3
0.6
0.9
1.2
1.5
init 1 c 3 c 10 c 30 cES
R, O
hm
CWR09 22uF 20V
Baking to avoid pop-corning.Multiple soldering cycles might degrade ESR and DCL.Recent projects’ failures (linear regulator oscillated due to increased ESR, first turn-on failures)
Updates on Wet Tantalum Capacitors
6
Reverse bias effects are similar to solid tantalum capacitors but might cause more dramatic consequences.
Ripple current testing and requirements for rating and derating for applications in vacuum.
Vibration testing of various types of capacitors is work in progress.
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
0102030405060708090
100
0 200 400 600 800 1000
tem
pera
ture
rise
, dee
g.C
time, sec
DWG93026 120uF 25V T1
120Hz 0.47A
120Hz 0.57A
120Hz 0.68A
Irm at 0.12 kHz =0.75A
Failure in vacuum chamber
Guidelines for S&Q have been updated to include ripple current requirements.Requirements for vibration testing should be specified.
Thermal run-away in vacuum happened at currents below Irm.
Updates on Polymer Capacitors
7
Characteristics of various types of chip and hermetic polymer tantalum capacitors are monitored since 2009.
Substantial progress in performance and quality, especially for HV capacitors.
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
50
70
90
110
130
-150-125-100-75 -50 -25 0 25 50 75 100 125 150
capa
cita
nce,
uF
temperature, deg.C
120 Hz
1 kHz
10 kHz
40 kHz
0.01
0.1
1
-150-125-100 -75 -50 -25 0 25 50 75 100 125 150
ES
R, O
hm
temperature, deg.C
120 Hz 1 kHz10 kHz 40 kHz100 kHz 400 kHz
Chip capacitors are still not ready for space applications. Hermetically sealed capacitors are good candidates for
space, especially for low-temperature applications. High-temperature performance still remains a problem.
10uF 35V
DCL_1000sec, A
cumu
lative
prob
abilit
y, %
1.E-9 1.E-51.E-8 1.E-7 1.E-61.E-1
5.E-11
510
50
100
1.E-1
Eng. samples 2009
DC0927
DC1008
DC1120
DC1336
Future Work on Tantalum Capacitors
8Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
MnO2 chip capacitors. Leakage currents and requirements for HT DCL. MSL issues and requirements for manual soldering.
Requirements for DCL and conditioning for soldering. High volumetric efficiency wet capacitors.
Leakage currents, gas generation, and requirements for wet. Analysis of requirements for vibration testing. Effect of HT storage.
Requirements for DCL and vibration testing. Polymer capacitors:
Evaluation of automotive industry parts. Hermetically sealed capacitors.
Assessment of performance at high temperatures.
High CV parts require improved S&Q procedures.
New Technology low-voltage MLCCs
PME
Thin dielectric
BME
“large size”(0603 and above)
“small size”(below 0402)
Embedded Flex termination
New Technology MLCCs
9Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
The electrode system in MLCCs is limited to two materials. Diversity is due to variety of ceramic compositions and processes. Two major issues with MLCC:
Cracking-related low-voltage failures; Oxygen-vacancies-related IR degradation.
Specifications:MED, AUTO, MIL(?)
BME is a mature technology in commercial world
Low-Voltage Failures
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HSSLV testing of various types of PME and BME capacitors showed that all PME capacitors with cracks failed, compared to16% for BME.
Failed BME capacitors had much greater IR. Cracks in BME can be revealed by THB testing at V >> 1.3V.Manual soldering have a detrimental effect on MLCCs with defects.
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
Probability of failures for PME is greater than for BME capacitors. The difference is due to the specifics of electro-chemical behavior of Ni and Ag/Pd and formed products.HSSLV testing is not effective for BME.
BME
PME
IR Degradation
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
11
It is assumed that reliability of BMEs is limited by VO++.
The wear-out problem is still there, but it has been moved out of application conditions by using new materials and processes.(Life testing (1000 hr, 2VR, 125 °C) is equivalent to thousands of years at 65 °C and 0.5 VR).
Intrinsic wear-out failures due to VO++ do not affect applications.
Failures in the systems are caused by manufacturing or assembly-introduced defects.
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
2 4 6 8 10
time,
yea
rs
voltage acceleration constant, n
Time at 65C, 0.5VR that is equivalent to 1khr life testing
0.7eV 0.9eV1.1eV 1.3eV1.5eV 1.7eV1.9eV
−×
=
211
2 11expTTk
EVVAF a
n
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
0.33uF 50V at 175C 200V
BME_CBME_APME_VPME_C
BME and PME capacitors at HALT
Detection of Defects
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Local defects do not change C, DF and IR, but affect VBR. Majority of MLCCs with defects can pass DWV test.
defect
High values of VBR (similar to IR) provide assurance that the parts have no gross defects that might cause failures.The consistency of VBR distributions indicates stability of the
manufacturing process and quality of the product.
VBR intrinsic VBR intrinsic
VBR defect
VBRi < VBRd
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
Example of intrinsic breakdowns
Distributions of VBR
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In most cases distributions of VBR for BME capacitors are bimodal. The HV mode has tight distributions (STD/Mean ~4%) indicating
intrinsic breakdown. The presence of LV subgroup is due to defects.
0.1uF 25V and 50V BME MLCCs
breakdown voltage, V
cumu
lative
prob
abilit
y, %
0 2500500 1000 1500 20001
5
10
50
99
0805 15um 25V M
0805 13um 25V A
0603 8um 50V C
1210 26um 50V C
BME capacitors with bimodal distributions
breakdown voltage, V
cumu
lative
prob
abilit
y, %
200 2200600 1000 1400 18001
5
10
50
99
1812 1uF 50V
0805 0.1uF 25V
0805 0.12uF 50V
1210 0.1uF 50V12 um, floating electrode
15 um
13 um
14 um
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
The interception point indicates proportion of defects. The spread of VBR towards low voltages indicates the
significance of defects. Lot acceptance criterion: VBRmin/VBR75 > 0.5.
Reliability of MLCCs with Defects
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Assumptions: intrinsic degradation for a defect-free part results in failures at TTF0 and the voltage AF follows PV equation with n ~ 3 for PME and nfrom 4 to 9 for BME capacitors.
n
i
dVBR
VBRTTFTTF
×= 0
VBR intrinsic VBR
defectV0
++
TTFs were calculated based on VBR assuming for PME TTF0=50 khr, and for BME TTF0=10 khr.
0805 0.1uF 25V, life test simulation
time, hrcu
mulat
ive pr
obab
ility,
%1.E-1 1.E+51 10 100 1000 100001
5
10
50
90
99
BME, n = 9
BME, n = 3PME, n = 3
β=0.3
β=0.9
PME
β=3 to 9
BME
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
Wear-out degradation in BME capacitors with defects results in IM failures.
The greater the voltage acceleration constant n and the lower VBR/VBR75, the more probable IM failures are.
Effect of Soldering Stresses on VBR
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BME 0805 0.12uF 50V Mfr.A
breakdown voltage, V
cumu
lative
pro
babil
ity, %
500 1500700 900 1100 13001
5
10
50
99
initialafter TSD_350
BME 0805 0.47uF 16V Mfr.Pa
breakdown voltage, V
cumu
lative
pro
babil
ity, %
500 800560 620 680 7401
5
10
50
99
initial
after TSD_350
BME 1825 0.47uF 50V, Mfr.A
breakdown voltage, V
cumu
lative
prob
abilit
y, %
0 2500500 1000 1500 20001
5
10
50
99
manual soldering
TSD_350Cvirgin
intrinsicbreakdown
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
Some lots are sensitive to TSD stress.Stresses related to manual soldering
can degrade VBR.VBR can be used as one of tests to
qualify MLCCs for manual soldering.
Effect of Soldering
16
It is often assumed that large size MLCCs are more vulnerable to cracking.
Out of 40 samples of 0603 size MLCCs soldered with a soldering iron set to 315°C, 10 samples had intermittent or no contact.
Failures were due to cracks along the terminations. No failures when parts were soldered onto a board preheated to 150°C.
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
Manual soldering can cause cracking of small size capacitors. Preheating of the board is critical to reduce the probability of
failures.
crack
Effect of Soldering, Cont’d
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.
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Solder
Board
Capacitor
Board
Capacitor
crackTensile stress
Board
CapacitorSolder
∆L
Project failure case.0402, 1000pF 50V X7R.
Post-soldering touch-up to improve the attachment might result in tensile stresses.
Tensile stresses can cause cracking.
To decrease the probability of fracturing during soldering, both, the reduction of the level of stress and selection of robust capacitors are necessary.
Future Work on Ceramic Capacitors
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Defect-related mechanism of failures at HT. Requirements for screening.
Effect of manual soldering conditions on reliability. Requirements for qualification testing.
Comparative analysis of performance and reliability of PME and BME capacitors: Leakage currents. Breakdown voltages. Mechanical characteristics and the probability of fracturing. Recommendations for application.
Reliability issues related to assembly of small size MLCCs (0402 and less). Screening and qualification requirements.
Deliverable to NASA Electronic Parts and Packaging (NEPP) Program to be published on nepp.nasa.gov originally presented by Alexander Teverovsky at the NASA Electronic Parts and Packaging (NEPP) Electronics Technology Workshop, Greenbelt, MD, June 17-19, 2014.