HDDG is a group for hardware designers, hackers, and enthusiast to discuss hardware-related topics. #11 (or 0xb) featured a presentation from SnapEDA CEO on Footprints and my presentation on Capacitors. Titled "They're JUST capacitors?" I used content from my time as a KEMET Field Application Engineer.

1. 1
They’re JUST capacitors?
James Lewis
Marketing Director
jameslewis@kemet.com
@baldengineer

2. 2
Different materials make different capacitors
Electrode Plates Dielectric
Basic Capacitor
C = ε0KA(n−1)
d

3. 3
Topic List
• Ceramics
– Why they lose capacitance
• Aluminum
– Why they don’t last forever
• Tantalum
– Why are they are safe to use
• Supercapacitors
– Why they are called super
We need a context…

4. 4
Capacitors should be
voltage derated 50%
True Or False
It Depends…

5. 5
Ceramics

6. 6
Multilayer Ceramic Capacitor (MLCC)
Typical Construction
Ceramic Dielectric
Electrode
(Ni for BME, Ag/Pd for PME)
Termination
(Cu for BME, Ag for PME)
Finish
(Plated Sn)
Barrier Layer
(Plated Ni)
+
-
Capacitances in parallel are additive
CT=C1+C2+C3+….Cn
C = ε0KA(n−1)
d
Max Capacitance is limited by “larger” layers

7. 7
Relative Capacitance vs. Temperature
Temperature Coefficients
C0G (NP0)
Temperature
‘K’Magnitude
X7R
X5R
Z5U
Y5V
‘Room’ Ambient
U2J

8. 8
Voltage Coefficient (Class II and III)
1210 vs 0805, X7R, 10uF, 6.3V
-60%
-50%
-40%
-30%
-20%
-10%
0%
10%
0 1 2 3 4 5 6
CapacitanceChange
Applied DC Bias (VDC)
Capacitance Change vs. DC Bias
Rated 6.3V
How much capacitance do you really get?
1206
0805

9. 9
K-SIM: ESR, Z, SPICE Model, VCC, and S-Parameters
ksim.kemet.com

10. 10
X7R Aging Rate
1.5% per Decade Hour (Limit)
-14
-12
-10
-8
-6
-4
-2
0
2
4
6
8
10
12
14
1 10 100 1,000 10,000 100,000
Time Post Heat
PercentageNominal
Reference
8,777Hr=1Yr
87,770Hr=10Yr
https://ec.kemet.com/aging-calculator-for-ceramics

11. 11
Aluminum Electrolytic

12. 12
Aluminum Electrolytic
Form Factors
Axial/Radial Screw Terminal Snap-In
Single Ended SMD Motor Start
Same construction different form factors

13. 13
Cathode
Plate
Electrolyte
Aluminum Untreated Surface Area
Anode
Plate
C1 C2
If C2 >> C1,
then Ct ~ C1
d
A
C r 0εε
=
0ε
( ) 932 =OAlrε

14. 14
d
A
C r 0εε
=
Electrolyte
Anode
Plate
Aluminum Acid-Etched Surface Area
C1 C2
C2 must remain >> C1
Cathode
Plate
0ε

15. 15
Anode Foil
Etched Surface

16. 16
Aluminum
Anode
VFormation > VRating > Vapplication
Wet
Electrolyte
Reformed dielectric region Dielectric
Depletion
O-2
O-2
Reform
Reforming / Self-Healing Wet Aluminum
Electrolyte
“Cathode”
Dielectric
Voltage contributes to operational lifetime

17. 17
Tantalum

18. 18
All Tantalums explode… or do they?
MnO2 MnO2 MnO2 MnO2 MnO2
Poly Poly Poly Poly Poly
2x Rated Voltage,
applied with reverse polarity and
>20 amps of current.
18
Every capacitor on this board failed as “short”

19. 19
• Stable C (No Temp or Bias Effects), DCL (t)
• Reliable (Decreasing FR)
• Long Life (Exceeds Expected Life of All Hardware)
• Most Volumetrically Efficient (CV/cc, E/cc)
Military
Space
Medical
Automotive
Computers
Telecom
Ta
Ta2O5
SEM of a Sintered Ta Anode
Ta
Why use Tantalum?
Ta Oxide Dielectric

20. 20
Polymer Electrolytic:
A “new” kind of capacitor

21. 22
Difference in Self-Healing
“Traditional”
MnO2
New
Polymer
Current through fault
generates enough heat
and oxygen for ignition.
Conductive polymer
consumes oxygen
preventing ignition.
Tantalum Crack
Impurity
Ta Polymer
Polymer
oxidized
Ta2O5
Crack
Impurity
Ta MnO2
Mn2O3
Ta2O5
If a polymer fails, it fails safely.

22. 23
Tantalum Voltage Derating
Depend on cathode material
• Typical derating guidelines:
• Tantalum MnO2: 50%
• Tantalum Polymer: 20%(>10V), 10% (≤10V)
• Aluminum Polymer: 0%!
35
12
4
0
126%
Ta-Poly KO
VR>10VDC
6,310
@100% VRated
FR(PPM)
1,700
@90% VRated
FR(PPM)
458
@80% VRated
FR(PPM)
9
@50% VRated
FR(PPM)
0
0
0
0
235%
8
2
1
0
197%68%
100 PPM FR
% VRated
Alum-Poly AO
Ta-Poly KO
VR≤10VDC
Ta-MnO2

23. 24
Supercapacitors

24. 25
What Is A “Super” Capacitor?
APowerCap
BestCap
BoostCap
CAP-XX
DLCAP
EneCapTen
EVerCAP
DynaCap
Faradcap
GreenCap
Goldcap
HY-CAP
Super capacitor
SuperCap
AS Capacitor
PowerStor
PseudoCap
Ultracapacitor
Electrostatic Double-Layer Capacitor (EDLC)

25. 26
(Electrical) Double Layers
1. IHP Inner Helmholtz Layer
2. OHP Outer Helmholtz Layer
3. Diffuse layer
4. Solvated ions
5. Specifically adsorptive ions
6. Solvent molecule

26. 27
Traditional and EDLC
Comparison
Aluminium Reference
+
+
+
+
+
+
+
-
-
-
-
-
-
-
AlAl2O3
Dielectric
Al
+
+
+
+
+
+
+
-
-
-
-
-
-
-
C =
Q
V
-
-
-
-
-
-
-
+
+
+
+
+
+
+
Battery
Electrode
Solvent
Molecule
(~0.3 to 2 nm)
C
Symmetric
“Supercapacitor”
+
+
+
+
+
+
+
-
-
-
-
-
-
-
C
Separator
+
+
+
+
+
+
+
-
-
-
-
-
-
-
Asymmetric
“Hybrid Capacitor”
C
Separator
C =
ε0KA
d
Surface area of carbon
Inner Helmholtz Layer

27. 28
Electrolytes
Acetonitrile
– CH3CN
– Common for SC
– Dielectric constant:
37
– Burns to HCN
– BP: ~80°C
Propylene
Carbonate (PC)
– C4H6O3
– Dielectric constant:
64
– Destructive effect
on graphite
– BP: ~240°C
Sulfuric Acid
– H2SO4
– Used in lead-acid
batteries
– Dielectric constant:
~100
– BP: 337°C

28. 29
Tools

29. 30
Mobile Catalog Apps
Access to over 350 catalogs and 4.8MM data
sheets
www.kemet.com/mobileapps

30. 31
ksim.kemet.com

31. 32
www.engineeringcenter.com

32. 33
james@baldengineer.com
email | www | twitter
www.baldengineer.com & www.addohms.com

33. 34
Capacitors should be
voltage derated 50%
True Or False
It Depends…

34. 35
Summary
• Ceramic
– More capacitance
• Aluminum Electrolytic
– Longer operational life
• Tantalum
– Power-On Reliability
• Supercapacitors
– Operational Life
Why do you voltage de-rate a capacitor?
Slides: www.baldengineer.com/hddg11

35. 36
Thank You!