The difference between aluminum capacitor and tantalum capacitor

The capacitor we use for the high frequency bypass is MLCC capacitor, which is multi-layer ceramic capacitor. Mainly because of its high frequency characteristics, SIPCAP software can be used to determine the band-limited frequency of its capacitor.

The comparison between tantalum capacitor and aluminum capacitor is as follows:

Electrolytic capacitors are traditionally classified by anode material, such as aluminum or tantalum. Therefore, electrolytic capacitors are divided into the following types according to the anode:

1. Aluminum electrolytic capacitor. Whether they are SMT or in-line, as long as they have an aluminum anode, they are called aluminum electrolytic capacitors. There is no direct relationship between the packaging method of capacitor and the quality of capacitor itself, the performance of capacitor only depends on the specific model.

2. Tantalum electrolytic capacitor. The anode is made of tantalum. Currently, many tantalum electrolytic capacitors are installed in a patch type, and their shells are generally packaged with resin (the same packaging may also be aluminum electrolytic capacitors). However, the cathode of tantalum capacitor is also an electrolyte.

The traditional view is that the performance of tantalum capacitor is better than that of aluminum capacitor, because the dielectric of tantalum capacitor is tantalum penoxide generated by anodic oxidation, and its dielectric capacity (usually expressed by) is higher than that of aluminum capacitor. Therefore, for the same capacity, the volume of tantalum capacitor can be made smaller than that of aluminum capacitor. (the capacitance of the electrolytic capacitor depends on the dielectric capacity and volume of the medium. In the case of a certain capacity, the higher the dielectric capacity is, the smaller the volume can be; otherwise, the larger the volume needs to be.)

But this method of judging the capacitance by the anode is out of date. The key to determining the performance of electrolytic capacitors is not the anode, but the electrolyte, or cathode. Because different cathodes and different anodes can be combined into different kinds of electrolytic capacitors, their performance is also very different. Due to the different electrolytes, the performance of the capacitor with the same anode can vary greatly. In short, the influence of the anode on the capacitance is much less than that of the cathode.

The cathode material is the capacitor's other plate, the cathode is the capacitor's electrolyte. At present, the cathode of capacitor basically has the following:

1. Electrolyte. The most traditional electrolyte is the electrolyte, which is obtained by heating gamma-butyllactone organic solvent with a weak acid capacitor. The cathode of an aluminum electrolytic capacitor in the ordinary sense that we see is this electrolyte. Using electrolyte as cathode has many advantages. First lies in the liquid and the medium of the contact area is larger, which is helpful to enhance the capacitance. The second is the electrolytic capacitor made with electrolyte, which can withstand up to 260 degrees of high temperature, so that it can pass the wave soldering (wave soldering is an important process for SMT patch installation), and the pressure resistance is also relatively strong. In addition, the electrolytic capacitor using electrolyte as the cathode can self-heal as long as the breakdown current does not continue after the breakdown of the medium. But electrolytes also have their drawbacks. First of all, it is easy to volatilize and leak in the high temperature environment, which has a great impact on the life and stability. Under high temperature and high pressure, the electrolyte may vaporize instantly, and the increase of volume will cause the explosion (which is often referred to as the explosion). Secondly, the ionic conductivity method adopted by the electrolyte has a very low conductivity, only 0.01S (conductivity, the reciprocal of ohm) /CM, which causes the ESR value of the capacitor (equivalent series resistance) to be extremely high.

2. Traditionally, it is believed that the performance of tantalum capacitor is better than that of aluminum capacitor, mainly due to the fact that tantalum capacitor is obviously better than the performance of aluminum electrolyte capacitor after tantalum plus manganese dioxide cathode boost. If the cathode of aluminum electrolyte capacitor is replaced with manganese dioxide, its performance can actually improve a lot.

Manganese dioxide. Manganese dioxide is the cathode material used in tantalum capacitors. Manganese dioxide is a solid and conducts electrons in a conductive manner. The conductivity is ten times higher than that of electrolyte ions (0.1s /CM), so ESR is lower than that of electrolyte. As a result, tantalum capacitors have traditionally been considered much better than aluminum, with no risk of leakage of solid electrolytes. In addition, the high temperature characteristics of manganese dioxide is also better, can withstand the instantaneous temperature in 500 degrees. The disadvantage of manganese dioxide is that in the case of polarity inversion, it is easy to produce high temperature and release oxygen in the high temperature environment. At the same time, the dielectric layer of tantalum penitucide changes in crystal quality, resulting in brittleness and fracture. Along the fracture, oxygen and tantalum powder mix and explode. In addition, the price of this kind of cathode material is also more expensive. (how many people notice that aluminum electrolytic capacitors, while all exploding, work on a different principle?)