Selection (and precautions for use) of Aluminum Electrolytic Capacitors in LED Lighting Applications Page 1 of 25 Technical Support Live Chat Help www.NICcomp.com Questions relating to the following information - or - requests to schedule technical seminars on this information should be directed to: Jim Wight, VP Technology [email protected] 631-396-7500 Page 2 of 25 Electrolytic Capacitor in LED Driver App 5 Watt LED Driver Circuit Junction Temperature ~+95 C Diffusion Temperature ~+70 C PCB Ambient Temperature +50 C ~+65 C 100uF / 25VDC x 2 220uF / 25VDC x 1 INPUT CAPACITANCE The total capacitance should be at least 200µF With 20VD (of higher VDC rating) Electrolytic Capacitor with a 220µF/25VDC rating for low cost Page 3 of 25 Capacitor Requirements Establish life time (hours) goal for application Example: 80,000 hours (9+ years @ 24/7 application) Establish ambient operating temperature Example: Multiple end-use applications • PCB operation over range of +50 C ~ +65 C Capacitance value needed? Example: 220uF Voltage rating needed? Example: 25VDC (minimum) Selection of capacitor Capacitor Requirement CV: 220uF @ 25VDC Life: 80,000 Hrs @ +65 C Page 4 of 25 Component Specification Review Load Life Rated at maximum rated temperature (i.e. +105°C) and WVDC Load Life Rating by Component Diameter ( Ø mm ) Based upon endurance test results performed by component manufacturer Load Life Test Limits NOTE: Possible variation in test limits between component manufacturers Example: ±30% instead of ±20% limit for Δ Capacitance Page 5 of 25 Aluminium Electrolytic Capacitor Construction X-Ray Image Aluminum Can End Seal Safety Vent Capacitor Element Mechanical Seal Lead Wire Electrolyte dissipation follows the Arrhenius Rate Page 6 of 25 Capacitor Life Time vs. Temperature Aluminum electrolytic capacitor life time is reduced at higher operating temperatures Temperature Period 24 / 7 8 Hours/Day +105°C 5000 hours 0.6 years 1.7 years +85°C 20,000 hours 2.3 years 6.8 years +65°C 80,000 hours 9.1 years 27.4 years Page 7 of 25 Aluminium Electrolytic Capacitor Life Time 1200uF @ 10VDC, 10x20mm Size: 4000 Hour Load Life Rating @ +105 C @ WVDC Performance Characteristic Change over Time @ Rated Temperature 10,000 hours @ +105 C @ 10VDC Capacitance Change (%) Test Time (1000 hours) Capacitance = 1200uF 1056uF 948uF Dissipation of the liquid electrolyte from the capacitor reduces the cathode connection, resulting in Capacitance decrease & Dissipation Factor (ESR) increase The rate of dissipation follows the Arrhenius equation for chemical reactions Reaction rate will double for each 10 C increase in temperature Î Capacitor life time expectation doubles for 10 C decrease in operating temperature Page 8 of 25 Aluminium Electrolytic Capacitor Life Time 1200uF @ 10VDC, 10x20mm Size: 4000 Hour Load Life Rating @ +105 C @ WVDC Performance Characteristic Change over Time @ Rated Temperature 10,000 hours @ +105 C @ 10VDC DF Loss Tangent (%) Test Time (1000 hours) Tan δ = 0.19 0.38 120Hz ESR = 0.26 ohm 0.66 ohm Increasing resistive losses over time Capacitor becomes less efficient over time of operation ESR (series resistance) increases over time Page 9 of 25 Aluminium Electrolytic Capacitor Life Time Î Capacitor Life time Expectation doubles for 10°C decrease in operating temperature Í +45°C +55°C +65°C +75°C +85°C +95°C +105°C 64,000 32,000 16,000 8,000 4,000 2,000 1,000 128,000 64,000 32,000 16,000 8,000 4,000 2,000 >15 Yrs 96,000 48,000 24,000 12,000 6,000 3,000 >15 Yrs 128,000 64,000 32,000 16,000 8,000 4,000 >15 Yrs >15 Yrs 80,000 40,000 20,000 10,000 5,000 Capacitor Requirement CV: 220uF @ 25VDC 5000 Hrs @ +105°C Life: 80,000 Hrs @ +65°C Page 10 of 25 Component Selection Capacitor Requirement CV: 220uF @ 25VDC Life: 80,000 Hrs @ +65 C Rating of 5000 Hrs @ +105 C SMT V-Chip Type: 5000 hours @ +105°C 220uF 25VDC (or greater) » » Radial Leaded Type: 5000 hours @ +105 C » 220uF » 25VDC (or greater) PN: NAZT221M25V8X10.5 220 µF, 25VDC, 8X10.5mm -40C ~ +105 C 5000 hrs @ +105 C 20,000 hrs @ +85 C 80,000 hrs @ +65 C 2 Times Reflow 80 Sec >+200 C 40 Sec >+230 C Peak = + 260 C PN: NREHL221M25V8x11.5 220 µF 25VDC, 8x11.5mm 3.5mm LS -40C ~ +105C 7000 hrs @ +105 C 28,000 hrs @ +85 C 112,000 hrs @ +65 C Page 11 of 25 Component Selection DOUBLE LIFETIME » » Capacitor Requirement CV: 220uF @ 25VDC Life: 80,000 Hrs @ +75°C Rating of 10,000 Hrs @ +105°C SMT V-Chip Type: 10,000 hours @ +105°C » 220uF » 25VDC (or greater) » » Radial Leaded Type: 10,000 hours @ +105°C » 220uF » 25VDC (or greater) 2 Times Reflow 60 Sec >+200°C 20 Sec >+230°C Peak = + 250°C PN: NAZV NAZV221M25V8X10.5LBF 220 µF, 35VDC, 10X10.5mm -40C ~ +105C 10,000 hrs @ +105°C 40,000 hrs @ +85°C 80,000 hrs @ +75°C > 15 years @ +65°C PN: NRSH221M50V10x16F 220 µF, 50VDC, 10x16mm 5mm LS -40C ~ +105C 10,000 hrs @ +105°C 40,000 hrs @ +85°C 80,000 hrs @ +75°C > 15 years @ +65°C Page 12 of 25 Component Selection Capacitor Requirement CV: 220uF @ 25VDC Life: >80,000 Hrs @ +75°C FURTHER EXTENDED LIFETIME » SMT V-Chip Type: PN: NSPE-T271M25V10X10.8NBYF 270uF, 25VDC in 10X10.8mm 2 Times Reflow 80 Sec >+217°C 40 Sec >+230°C Peak = + 260°C 12,000Hrs @ 105°C 48,000Hrs @ +85°C 96,000Hrs @ +75°C (11 Yrs ) PN: NSPE-Y271M25V10X10.8NBYF 270uF, 25VDC in 10X10.8mm 2000Hrs @ 135°C 16,000Hrs @ 105°C 64,000Hrs @ +85°C (7.3 Yrs ) 128,000Hrs @ +75°C (14.6 Yrs ) Page 13 of 25 Component Selection Capacitor Requirement CV: 200uF @ 25VDC Life: 80,000 Hrs @ +75°C Rating of 10,000 Hrs @ +105°C » Radial Leaded Type: » 10,000 hours @ +105°C » 2 X 100uF » 25VDC PN: NRGB101M25V6.3X11F 100 µF, 25VDC, 6.3x11mm 2.5mm LS -40C ~+105C 10,000 hrs @ +105°C 40,000 hrs @ +85°C 80,000 hrs @ +75°C 160,000 hrs @ +65°C Low Cost & Smallest Size Solution Page 14 of 25 Component Selection For higher voltage requirements (>16VDC) look to aluminium electrolytic capacitors Lowest cost solution • Aluminium E-cap : – 100uF @ 25VDC ≈ $0.08 each – 220uF @ 25VDC ≈ $0.12 each • Tantalum E-cap: – 100uF @ 25VDC = >$0.80 each Wide range of offerings CVs – sizes: SMT & LDD Voltages to 450VDC Transient resistant: – Ability to handle transient events – Excellent inrush current characteristics – Reverse bias tolerant Stable characteristic under voltage bias Open mode wear-out (safe) Page 15 of 25 Solid Aluminium Electrolytic Capacitors 10,000 hours @ +105°C @ 6.3VDC Capacitance Change Stable Over Time (%) Test Time (hours) Î Solid Aluminum (polymer electrolyte) has stable characteristics (no wear-out) Î Solid aluminum construction limited to ≤16VDC maximum rating Page 16 of 25 Aluminium Electrolytic Capacitors – Failure Modes Product Type: Aluminum Electrolytic Capacitors – Liquid Electrolyte Construction Failure Modes: Parametric Change Open Intermittent Short Causes: Wear-out Electrical Thermal Mechanical Corrosion Altitude Page 17 of 25 Aluminium Electrolytic Capacitors – Failure Modes Product Type: Aluminum Electrolytic Capacitors – Liquid Electrolyte Construction Potential Failure Mode - Causes: » Electrical Over-stress failures ... rapid failure >> case opening - case rupture >> or accelerated wear-out, joule heating, decreased cap, increased DF & ESR >> open circuit (Short circuit, Arcing; under extreme overstress conditions) Causes: Reverse Bias Over-voltage or Over-current Rapid charge - discharge Remedies - Fixes: + Anode - Cathode Assure polarity Use within specification limits Use alternate types: Low ESR & High RCR, Strobe–Photoflash or Solid technology Page 18 of 25 Aluminium Electrolytic Capacitors – Failure Modes Product Type: Aluminum Electrolytic Capacitors – Liquid Electrolyte Construction Potential Failure Mode - Causes: » Thermal Stress failures ... end-seal compromised >> accelerated wear-out >> open circuit Causes: Can Bulge - Deform Excessive soldering (reflow) heat Remedies - Fixes: Use higher reflow rated component Revise reflow conditions Revert to radial LDD & wave soldering Terminal Lift, Base-plate Warp Page 19 of 25 Aluminium Electrolytic Capacitors – Failure Modes Thermal Stress Page 20 of 25 Aluminium Electrolytic Capacitors – Failure Modes Product Type: Aluminum Electrolytic Capacitors – Liquid Electrolyte Construction Potential Failure Mode - Causes: » Corrosion failures ... Parametric changes, increased leakage current >> joule heating >> leading to short or disconnection; open circuit Causes: Halogenated fluxes and cleaning solvents Harsh end use environments Remedies - Fixes: Eliminate use of halogenated fluxes & solvents Sealer – coatings to protect components Page 21 of 25 Aluminium Electrolytic Capacitors – Failure Modes Product Type: Aluminum Electrolytic Capacitors – Liquid Electrolyte Construction Potential Failure Mode - Causes: » Mechanical stress failures ... stress to leads >> end-seal compromised >> accelerated wear-out >> open circuit Causes: Lead wire trimming Stress to component after mounting to PCB Lifting PCB by component case Remedies - Fixes: Review lead trimming Review PCB handling practices Page 22 of 25 Aluminium Electrolytic Capacitors – Failure Modes Product Type: Aluminum Electrolytic Capacitors – Liquid Electrolyte Construction Potential Failure Mode - Causes: » Mechanical stress failures ... stress to case >> dielectric compromised >> increased leakage current or short circuit Causes: Mishandling Stacking PCBs Improper Bulk Storage Remedies - Fixes: Review handling & storage practices Page 23 of 25 Aluminium Electrolytic Capacitors – Failure Modes Product Type: Aluminum Electrolytic Capacitors – Liquid Electrolyte Construction Potential Failure Mode - Causes: » Altitude (reduced pressure) failures ... accelerated wear-out decreased cap, increased DF & ESR>> open circuit Causes: Differential between internal pressure to outside pressure Exposure to high altitude or aviation Altitude (m) Air Pressure (hPa) 0 1013.3 2,000 795.0 4,000 616.4 Minimal Impact 6,000 471.8 Will Impact Lifetime 8,000 356.0 10,000 264.4 20,000 54.7 Remedies - Fixes: Use of alternate construction (solid) Page 24 of 25 Aluminium Electrolytic Capacitors – Failure Modes Wear-Out Accelerators Electrical Overstress Over-voltage Rapid charge–discharge Reverse operation Mechanical & Thermal Stress Corrosive Agents Cleaning solvents & fluxes Environment Reduced Pressure High altitude [ >20,000 Feet = >6100 Meters ] Page 25 of 25