Construction of Aluminum Electrolytic Capacitors: Pros and Cons

In our last blog post, we offered an introduction to the two main types of aluminum electrolytic capacitors: electrolytic and polymer.

In this post, we will take a closer look at the traditional construction of aluminum electrolytic capacitors, including their advantages and disadvantages.

Construction of Aluminum Electrolytic Capacitors

The general construction of an aluminum electrolytic capacitor consists of three materials:

  • Anode aluminum foil
  • Cathode aluminum foil
  • Certain paper separators in between

While all aluminum electrolytic capacitors will contain these three elements, there are special constructions we can use to increase the performance and lifetime of a capacitor. Click the image for more details on how these capacitors can be structured.

Basically, the capacitor has the aluminum foil (both anode and cathode), which is only a few µm thick and wound with certain number of separator papers. Then, everything is impregnated with a wet electrolyte; the paper roughness will mainly distinguish the leakage current.

There are a few different types of aluminum electrolytic capacitors: SMD (V-chip, H-chip), THD (radial, axial), snap-in, and screw. About 57% are radial and 15% are V-chip. Almost all (99%) of these are polarized types, but non-polar types are available if you need that for your application.

Roughness of Aluminum Foil

As we mentioned, the most important factor in distinguishing the performance of the capacitor is the thickness and roughness of the aluminum foil. The type of foil makes a significant difference in the etching and forming processes of the capacitor.

For instance, the anode foil of capacitors for caps with low-rated voltage is not very rough, while those with high-rated voltage is much rougher. This is because the etching process takes much more production time and control, especially considering how thin the foil must be (the maximum thickness might be less than 1 µm).

Types and Polarization

To give you an idea of what these capacitors look like, this image shows a breakdown of the different polarization designators of the radial leaded, SMT V-chip, and snap-in capacitors.

Without a solid understanding of these mechanical signs, you could end up with the wrong polarity, and your part will be completely destroyed.

Pros and Cons of Aluminum Electrolytic Capacitors

So what are the advantages and disadvantages of using aluminum electrolytic capacitors? Here are the key pros and cons.

Pros:

  • Very good availability of raw material
  • Highly automated manufacturing process
  • Very high capacitance values and voltage ranges available
  • Different construction and connection types available

Cons:

  • Possibility of explosion if wrong polarity
  • Necessary forming of high C-values
  • Large tolerances (e.g. C +/- 20%)
  • Dependency of aging (e.g. dry-out)
  • Tendency to self-heat for types with high ESR (thus increasing the process of dry-out)

Along with the obvious danger of explosion, the main disadvantage to using aluminum electrolytic capacitors is the likelihood of dry-out.

Essentially, when the capacitor is not in use, it will start to decrease the dielectric on the anode foil. The bigger the capacitor and the higher the voltage, the faster this process will occur — and this process will continue as long as the capacitor is not being used. That means that after a certain amount of time, the capacitor will need to be re-formed or replaced.

Learn More about Aluminum Electrolytic Capacitors

Eager to learn more about aluminum electrolytic capacitors vs. polymer electrolytic capacitors? Stay tuned to our blog, or check out our ABC of Capacitors design guide!

Ready to see the capacitors in action? View our product pages for aluminum electrolytic capacitors and aluminum polymer capacitors online!

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