Aluminum Electrolytic Capacitor Performance and Circuit Impacts

Aluminum electrolytic capacitors store massive amounts of energy in compact packages that are available at an attractive price.

Figure 1: The construction (right) and cross section (left) of an aluminum electrolytic capacitor.

 

­A growing number of applications, ranging from solar power converters all the way to miniature power supplies for highly complex processing cores, are starting to capitalize on the benefits of aluminum electrolytic capacitors. Aluminum electrolytics are also increasingly used to satisfy miniaturization demands in complex power tree applications like FPGAs powered by multiple voltages.

And while it’s true that aluminum electrolytics also come with disadvantages, several of the more well-known ones are no longer true, and other perceived disadvantages can be reduced or eliminated by selecting newer components engineered to overcome some of the technology’s traditional shortcomings.  

 

Technology Performance and Options

Electrolytics are named after their anode material, which can include aluminum, tantalum, tantalum polymer, and niobium oxide. Since aluminum electrolytics exhibit a relatively low dielectric permittivity compared to tantalum devises (about 9 vs. 30), it would be reasonable to assume that they have the worst capacitance density of all electrolytics. However, aluminum electrolytics have highly etched aluminum electrodes that significantly increase the surface area of the capacitor and more than offset their low dielectric permittivity.

Some newer aluminum electrolytics also leverage one of the most notable SMT advances in recent years: the vertical chip package. The construction of these devices is simple, consisting of a radial can electrolytic mounted to a back plate to become an SMT device, as illustrated by the cross section in Figure 1. Essentially, two deeply etched aluminum foil electrodes are separated by a paper and wound into a cylinder that is taped, placed in a sleeve, and inserted into a metal can with a rubber seal on the bottom. 

The simple structure of miniature, wound, wet SMT aluminum electrolytic capacitors tend to limit long-term reliability, high-frequency efficacy, and temperature stability. But component manufacturers have noted these shortcomings and, in recent years, developed several material systems engineered to improve their reliability and performance, including wet, polymer, and hybrid aluminum electrolytic capacitor technologies.

Figure 2: Modern miniature SMT aluminum electrolytic capacitors are available with wet, polymer, and hybrid electrolytic material systems

 

 

Aluminum Electrolytics

Traditional wet aluminum electrolytic capacitors use a liquid electrolyte to make electrical contact with the wound aluminum electrode foils. The electrolyte is sealed in an aluminum can with a rubber gasket that is tightly filled and then crimp-fit into place.

This material system has two primary limitations in addition to the standard limitations imposed by the simple structure of these miniature wound aluminum electrolytic capacitors. The chemical composition of the liquid electrolyte is a major contributor to capacitor performance as it relates to temperature, pressure, electrical stress, time, low-temperature capacitance, and ESR stability, and it can vary between suppliers. And a liquid electrolyte has the potential to leak or evaporate over time, which could cause the capacitors to fail.

However, users can employ several end user derating rules to increase capacitor reliability. For instance, derating the temperature by 10°C roughly doubles the component lifetime, and derating the applied voltage to rated voltage ratio also yields notable reliability improvements. 

So, on balance, wet aluminum electrolytics offer the broadest range of values and reasonable reliability at the lowest possible cost.

 

Conductive Polymer Electrolytics

The replacement of a wet electrolyte with a conductive polymer electrolyte eliminates the possibility of liquid electrolyte leakage between the seal case and leads along with long-term aging (evaporation) concerns. Conductive polymer electrolytics also exhibit nearly two times less ESR, two to three times greater RMS current capability, and about three times more stability with temperature, and they’re more reliable than wet electrolytics with a similar case size, value, and voltage rating. In addition, if temperature derating effects are taken into account, a 20°C derating of each technology shows that the life expectancy of a wet aluminum capacitor increases by a factor of four, while a conductive polymer aluminum capacitor increases by a factor of roughly 10.

Limitations of this material technology include increased DC leakage, a higher price point, and sensitivity to high shock and vibration environments. The DC leakage of these capacitors increases from about 0.01CV or 3µA for wet aluminum electrolytics to approximately 0.2CV or 300 to 500µA. But it’s a manageable increase early in the design process, and especially so considering that conductive polymer material systems more than double the reliability of wet electrolytics while simultaneously reducing ESR and increasing RMS current.

 

Hybrid Electrolytics

Hybrid electrolytics were developed to reduce the DC leakage effects of conductive polymer electrolytics and reduce the ESR of wet electrolytics, thereby improving on the reliability and performance characteristics of both materials. Hybrid electrolytics also perform exceptionally well in high humidity environments. As such, they also have a higher price point than wet and conductive polymer material systems. And while they do have some CV limitations, those challenges are actively being overcome with additional materials research and process efforts.

 

UF capacitors product lineup boasts an impressive range of SMD Aluminum Electrolytic Capacitors, each tailored to cater to unique requirements. Here's a glimpse of the series we offer:

TCS SMD Aluminum Electrolytic Capacitor 85°C

TCK SMD Aluminum Electrolytic Capacitor 105°C

TLZ SMD Aluminum Electrolytic Capacitor Low impedance

TKZ SMD Aluminum Electrolytic Capacitor Extremely Low Impedance

TFZ SMD Aluminum Electrolytic Capacitor Extremely Low Impedance Long life

TCP SMD Aluminum Electrolytic Capacitor High Voltage Long life 85°C  3000H

TCH SMD Aluminum Electrolytic Capacitor High Voltage Long Life 105°C 3000H

THU SMD Aluminum Electrolytic Capacitor High Voltage Long Life 105°C 5000H

TKH SMD Aluminum Electrolytic Capacitor High Temperature  125°C

TEL SMD Aluminum Electrolytic Capacitor Long life Assurance  3000H

TKL SMD Aluminum Electrolytic Capacitor Long life Assurance  5000H

TSC SMD Aluminum Electrolytic Capacitor Low Leakage Current

TCN SMD Aluminum Electrolytic Capacitor  Non Polarized 85°C

TKP SMD Aluminum Electrolytic Capacitor Non Polarized 105°C

Welcome to visit our website: https://www.ufcapacitors.com/

 

 

 

 

UF capacitors cross guide:

Photo	Description	UF Capacitors Series Code	Rubycon	Nichicon	Samwha	Panasonic
	TCS 85C V-Chip Aluminum Electrolytic	TCS Series	SEV Series	UWX Series	SC Series	EEE-X(A)S Series
	TCK 105C V-Chip Aluminum Electrolytic	TCK Series	SKV Series	UWT Series	RC Series	EEEHA Series
	TFZ 105C 2000-5000 long life with extra lower impedance Aluminum Electrolytic	TFZ Series	TZV Series TPV Series	UUD Series UUA Series NACZ Series UCD Series UWD Series	CM Series	EEE-FK Series EEE-FT Series EEV-FK Series
	TLZ 105C 1000-2000h lower impedance Aluminum Electrolytic	TLZ Series	SZV Series	UCL Series UCM Series	***	EEE-FC Series EEE-FT Series
	TMA 105C 2000h conductive polymer aluminum solid  Aluminum Electrolytic	TMA Series	PAV Series PHV Series	CV Series RFS Series	FA Series	SVPE Series SVP Series
	TMB Series 105C 2000h conductive polymer aluminum solid Aluminum Electrolytic	TMB Series	PAV Series PHV Series	CV Series RFS Series	FA Series	SVPC Series SVP Series