Hardware Developers Didactic Galactic 0xb: Capacitors
1 like12,452 views
The document discusses various types of capacitors including ceramics, aluminum electrolytic, tantalum, and supercapacitors, explaining their characteristics and applications. Key points include the performance issues of ceramics, the operational life of aluminum electrolytics, and the reliability of tantalum. The document emphasizes voltage derating in capacitors, providing guidelines based on materials and their suitability for different conditions.
Hardware Developers Didactic Galactic 0xb: Capacitors
- 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
- 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
- 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
- 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
- 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!