Radial capacitors have two leads which stick out from the bottom of the capacitor. They are a different configuration to axial capacitors in that sense because axial have one lead that sticks out from either end.

They are valuable in relatively high-current and low frequency electrical circuits. Electrolytic capacitors can have a very high capacitance, allowing filters made with them to have very low corner frequencies. Here we are proud to say that our company will provide you with the best quality of Electrolytic Capacitor that will fulfill your requirement. The Electrolytic Capacitors offered by us are highly resistible to extreme heat conditions and corrosion. Customers are also eased with the availability of the Electrolytic Capacitors in varied sizes and dimensions.

Radial Electrolytic capacitors have polarity and therefore it is important to solder them in with the correct polarity. Failure to do so and they vent (bulge at the top) after some minutes of operation. Positions for capacitors are marked with a circle that has one part shaded white. This marks the negative lead position. The capacitors also all have a stripe down one side. This marks the negative lead. So you need to line up those marks.

Not all PCBs follow this rule though. ASUS actually uses the white shaded part to indicate the positive lead on their PCBs, which is quite confusing. Occasionally there may be an error in the marking of the PCB also. So the best thing to do when replacing capacitors is to trust the way the original capacitors were positioned on the board and not the PCB.

Polymer capacitors are distinctive because at reasonably high capacitance values (say 300uf and above) they do not have vents whilst their wet electrolytic counterparts do. Their tops are completely flat. Due to the lack of liquid electrolyte they will never make gas when they fail and therefore do not require the vents for the gas to escape. It is important though not to confuse low capacitance value wet electrolytics (below 330uf) with polymers because they also do not have vents.

Still there are a few rare exceptions to the rule, Nichicon HD are not polymers but do not have visible vents. Fujitsu FPCAPs which are the yellow sleeved ones often seen on motherboards and graphics cards are a type of polymer cap but do have K vents.

The above capacitor is not a polymer capacitor, its just a normal wet electrolytic without a sleeve. Although there are not vents on the top of them, so you must learn how to identify it before you want to buy or use a polymer capacitor .

If we take a look at the above 6600gt graphics card we can see three types of polymer capacitors there. Two of them are chip type, namely the Chemicon PSA series and the Sanyo OSCON SVP series (of which there are two groups). The last polymer capacitor on the card is a Skywell SEL series which is a radial capacitor.

The chip type capacitors are soldered on top of the board. This is why they are called SMT components or surface mount technology. They have two legs, one on either of opposite sides which stick out horizontally and are soldered to two pads on the board.

A ceramic capacitor is a two-terminal, non-polar device. The classical ceramic capacitor is the "disc capacitor". This device pre-dates the transistor and was used extensively in vacuum-tube equipment (e.g., radio receivers) from c.a 1930 through the 1950s, and in discrete transistor equipment from the 1950s through the 1980s. As of 2007, ceramic disc capacitors are in widespread use in electronic equipment, providing high capacity & small size at low price compared to other low value capacitor types.

Ceramic Capacitors offer a broad range of size vs. performance tradeoffs and are easily the most popular in numbers sold. Ceramic capacitors are available from < 1 pF to 1000s of uF.

Ceramic Capacitors Pros: The main virtue of ceramic capacitors are their relatively high dielectric constants. This can vary from C0G with a K of up to 60, which has excellent electrical properties but is relatively large and expensive, to ceramics with Ks in the tens of thousands but with very poor electrical properties. Large- value ceramics can replace electrolytic capacitors in high-frequency applications like switch-mode power supplies because of their lower ESR. Ceramic capacitors are especially suitable for surface mounting due to their heat resistance, mechanical integrity, and the ability to make them in very small packages at low cost, for portable equipment. This has greatly added to their usage. To some extent ceramics are slowly displacing other types of capacitors.

Ceramic Capacitors Cons: Low breakdown voltage means that the low-K ceramics (Class 1), the ones with the good electrical properties, have poor volumetric efficiency, and are usually found only in small values. High-K ceramics (Class 2 and higher) have poor electrical properties, which are highly dependent on temperature, voltage, and frequency, plus a significant aging rate. Unlike many other capacitors, ceramics have no self-healing mechanism. This means that manufacturers must maintain a high level of quality control over the dielectric. Ceramics are most cost affective in small sizes at present. Very large ceramics are a bit of a challenge, especially in SMD.

Ceramic capacitors are available now in three main types although other styles are available:

• leaded disc ceramic capacitors for through hole mounting which are resin coated
• multilayer surface mount chip ceramic capacitors
• Specialist microwave bare leadless disc ceramic capacitors that are designed to sit in a slot in the PCB and are soldered in place