There are three family groups of aluminum electrolytic capacitors: non-solid, solid manganese dioxide, and solid polymer capacitors. From I/O decoupling in AC power supplies, to switched-mode power supplies in DC/DC converters, to DC-link capacitors in AC/AC converters for variable frequency drive and frequency changers, aluminum capacitors have many uses. They are also ideal for uninterruptible power supplies; power-factor correction; energy storage; motor start and for bipolar capacitors used in audio signal coupling.
The anode of the capacitors is made up of pure aluminum foil with an etched surface. It is also covered with aluminum oxide as the dielectric. Aluminum capacitors have the largest capacitance values per volume when compared with ceramic and plastic-film capacitors. They also have low impedance values even at lower frequencies. Aluminum capacitors can only be operated using DC voltage, as AC voltage will short circuit the component. The only exception to this is in the bipolar variety, which can be used in AC applications.
The non-solid variety of aluminum capacitors are the least expensive and offer the widest range of sizes, capacitance and voltage values. A liquid electrolyte delivers oxygen necessary for the re-forming or self-healing of the oxide layer. The downside is that this liquid electrolyte may evaporate during a drying-out process, causing drift and limiting life.
Figure 1: Aluminum electrolytic capacitors are available in a number of styles, sizes and series. (Source: Wikipedia)
Styles of aluminum capacitors include: SMDs for surface mounting on PCBs or substrates, radial lead terminals for vertical mount on PCBs, axial lead terminals for horizontal THT mounting, snap-in radial pin terminals and large screw terminals, both used in power applications.
The Vishay 30D106G050CB2A aluminum capacitor provides dependable performance in high-temperature industrial and electronic equipment with transistor or modified electron-tube circuits. Terminal connections are welded to eliminate open or intermittent contacts in pressure joints of conventional capacitors. The capacitors are metal encased and have a clear plastic outer insulating sleeve. They feature an axial termination style, capacitance of 10 uF, and tolerance of -10 percent to 75 percent. The case diameter is 8 mm with a length of 17.5 mm.
United ChemiCon’s APS350ELL330MJC5S conductive polymer aluminum solid capacitors feature super low ESR and high temperature resistance. They also have large capacitance and improved high ripple current capability. The rated voltage rage is 2.5 to 35 Vdc and their endurance is 2,000 hours at 105° C. Lead diameter is 0.6 mm and capacitance is 33000000 pF. The through-hole mounted device features an ESR of 0.03 Ohm and lead spacing of 5 mm.
Figure 2: United ChemiCon’s APS340ELL330MJC5S aluminum solid capacitors are suitable for use in DC-DC converters, voltage regulators and decoupling applications for computer motherboards. (Source: Chip1Stop)
The industrial-grade WBR60500 aluminum capacitor by Cornell Dubilier is suitable for a variety of industrial applications, as these capacitors feature high capacitance and extended life. Their rugged construction provides high vibration resistance necessary in industrial settings. They have a capacitance range of 1.0 to 5,000 μF and a voltage range of 16 to 450 Vdc. The capacitance tolerance is 16 to 50 Vdc between negative 10 and 150 percent, 75 to 350 Vdc between negative 10 and 100 percent, 450 Vdc between negative 10 and 50 percent, and the temperature range is between – 40º C and 85º C.