Aluminum electrolytic capacitors are made of two aluminum foils and a paper soaked in electrolyte. The anode aluminum foil is anodized to form a very thin oxide layer on one side and the unanodized aluminum acts as cathode; the anode and cathode are separated by paper soaked in electrolyte, as shown in Fig. 8.10A and B.
Electrolytic capacitors are available in several types as aluminum, tantalum, and niobium versions (Ho et al., 2010). The internal structure of an aluminum electrolytic capacitor consists of two aluminum foils, which are separated by a porous material such as paper which is impregnated with an electrolyte as shown in Fig. 6.11.
This guide covers the application of polar, non-solid aluminum electrolytic capacitors, which are those aluminum electrolytic capacitors featuring a wet, aqueous electrolyte with separator membranes such as cellulosic papers between two aluminum foils.
Other types of aluminum electrolytic capacitors not cov-ered include the obsolete wet types without separator mem-branes, “hybrid” aluminum electrolytic capacitors containing both polymer and liquid electrolyte components and sol-id-polymer electrolytic capacitors.
Aluminum electrolytic capacitors with non-solid electrolytes have an exceptional position among electronic components because they work with an electrolyte as liquid ingredient. The liquid electrolyte determines the time-dependent behavior of electrolytic capacitors. They age over time as the electrolyte evaporates.
Until the wound construction of aluminum foil capacitors, this type of capacitor was bulky and heavy. There are different sizes of capacitor ranging from 3 mm in diameter for 5 mm in height up to 90 mm for 210 mm .