Semec offer Dipped Tantalum and Chip Tantalum capacitor. Both type are with excellent temperature stability and suitable for small electronic devices application.
Capacitance up to 470uF and voltage ranges up to 50V.
For Chip Tantalum, Case S, A, B, C, D and E are available.
For Dipped Tantalum, both bulk and Ammo pack are available for automatic machine.
|Feature||Chip Tantalum Capacitor||Dipped Tantalum capacitor|
|Capacitance range||0.1uF to 470uF||0.047uF to 330uF|
|Rated Voltage||DC 4V, 6.3V, 10V, 16V,20V, 25V, 35V, 50V||DC 6.3V, 10V, 16V,20V, 25V, 35V, 50V|
|Capacitance Tolerance||±10%, ±20%||±10%, ±20%|
|Operating Temperature||-55℃ to +125℃||-55℃ to +125℃|
Tantalum capacitors are used in smaller electronic devices, including portable telephones, pagers, personal computers (PCs), and automotive electronics. They differ in terms of form factor, technology, and capacitance type. Leaded tantalum capacitors have leads for connections to circuits. Surface mount or chip tantalum capacitors do not. For both types of products, technology choices include single layer, multilayer, and wound. Single layer tantalum capacitors use a monolithic dielectric. Multilayer products are small in size and made of many layers. They provide good frequency characteristics as well as excellent temperature stability. Wound tantalum capacitors are built by winding foils, sometimes by hand. In terms of capacitance type, there are two choices: fixed and variable. Fixed tantalum capacitors have a nonadjustable capacitance value. Variable tantalum capacitors can be set with a potentiometer or other adjustment mechanism.
Selecting tantalum capacitors requires an analysis of performance specifications such as capacitance range, capacitance tolerance, DC rated voltage range (WVDC), equivalent series resistance (ESR), leakage current, dissipation factor and operating temperature. Capacitance measures the ability to store energy, given as C = K A/D, where A is the area of the electrodes, D is their separation, and K is a function of the dielectric between the electrodes. Normally, capacitance tolerance is measured as a percentage of capacitance. DC rated voltage range (WVDC) is the maximum continuous DC voltage that may be continuously applied to a tantalum capacitor at any temperature between the lower category temperature and the rated temperature. Equivalent series resistance (ESR) represents the extent to which tantalum capacitors act like resistors when charging and discharging. Dissipation factor (DF) is the ratio between the resistive and the reactive part of the impedance submitted to a sinusoidal voltage of specified frequency.
There are three main packaging specifications for tantalum capacitors: lead or termination type, mounting style, and packing method. Choices for lead type include surface mount technology (SMT), axial, radial, flying, tab, screw, gull wing, and J-leads. Mounting styles include SMT as well as through-hole technology (THT), bolt mounts, bracket mounts, and pole mounts. There are three main packing methods for tantalum capacitors: tape reel, tray or rail, and shipping tube or stick magazine. Polarized, non-polarized, and self-healing products are also commonly available.
The tantalum capacitor is a high reliability form of electrolytic capacitor in which the dielectric is formed from a very thin anodized layer of tantalum pentoxide.
Tantalum Capacitors Types and Construction
In military grade tantalum capacitors, the anode consists of a small cylindrical billet of tantalum metal held inside a sterling silver can, which forms the cathode, by teflon spacers. A tantalum lead exits the can via a teflon and silicone rubber gasket at one end. This tantalum lead is spot welded to a copper lead outside the can. An electrically conductive jelly fills the space between the inside wall of the silver can and the surface of the tantalum billet, which is covered by the steel blue layer of oxide which is the dielectric barrier.
A cheaper form consists of a similar sintered tantalum billet, coated in manganese IV oxide and an electro-deposited layer of silver, this being soldered inside a tin plated brass can with an enameled glass seal at one end.
The cheapest form consists of a mixture of tantalum powder and manganese IV oxide pressed into a solid chalky mass around a tantalum wire, this is coated with silver and dipped into coloured epoxy resin resulting in a small coloured bead with two leads.
Tantalum Capacitors Advantages and disadvantages
Tantalum capacitors possess very low electrical leakage, (high leakage resistance), and will retain a charge for a long duration, they are also more tolerant of harsh, hot operating environments unlike standard aluminium electrolytic capacitors. Tantalum capacitors are relatively expensive, particularly the military grades, they are not particularly tolerant of heavy charge and discharge currents, particularly of a repetitive nature and their effective series resistance, ESR, is quite high when compared to aluminium electrolytics. As with all electrolytic capacitors, correct polarity must be observed otherwise the capacitor will depolarize and the dielectric oxide layer will be reduced back to the metal, reducing the resistance of the device and causing it to become very hot and possibly explode. Tantalum capacitors are less prone to "drying out", causing a decrease in capacitance as is often the case with aluminium electrolytic capacitors particularly when used in hot environments. They maintain their designed capacitance under such conditions over long periods of time, (decades).
Tantalum Capacitors Uses
The low leakage and high capacity of tantalum capacitors favors their use in sample and hold circuits, (long hold duration), and some long duration timing circuits where precise timing is not critical. They are also often used for power supply rail decoupling in parallel with film or ceramic capacitors with low ESR and reactance at high frequency. Sometimes tantalum capacitors can replace aluminium electrolytic capacitors in situations where external environment or dense component packing results in sustained hot internal environment and high reliability is important.
Due to their higher cost, tantalum capacitors were rarely ever seen in consumer electronics, although the cheapest epoxy dipped types were sometimes used. Requirements for high quality and reliability, such as in medical electronics sees the use of many tantalum capacitors in this type of equipment.
Low-voltage tantalum capacitors are nowadays commonly used in large numbers for power supply filtering on computer motherboards and in peripherals due to their small size and long-term reliability.
A capacitor stores a charge and then supplies the charge required for the operation of a device, such as a semiconductor device. As the integration of the semiconductor devices increases, the size of the cells becomes smaller, and the capacitance required for the operation of the devices increases. A tantalum capacitor, a typical capacitor which has small size, low ESR, and high capacitance, has rapidly become popular as a component in cellular phones and personal computers. Tantalum capacitors are valued because of their ability to supply a high capacitance value within a limited volumetric space. Tantalum is currently used extensively in the electronics industry which employs tantalum in the manufacture of highly effective electronic capacitors. This is mainly attributed to the strong and stable dielectric properties of the oxide film on the anodized metal. The capacitance of a tantalum capacitor is effectively increased by increasing the surface area of fine metallic powder which is employed. Typical wet tantalum capacitors have porous anodes which are housed in a tantalum case and hermetically sealed. Such capacitors are well suited for use in military and industrial circuits that demand quality and reliability in filtering, bypass, coupling, storage and timing applications. A tantalum solid-state electrolytic capacitor is constituted of a sintered body obtained through sintering of tantalum powder, a tantalum oxide layer formed on the surface of the sintered body, a solid-state electrolyte on the tantalum oxide layer, and a conductive layer. The capacitor is polarized, in which a metal tantalum generally becomes an anode side electrode and the conductive layer on the solid-state electrolyte becomes a cathode side electrode. Anodes or electrodes for electrolytic tantalum capacitors are manufactured by compacting or compressing a precise quantity of capacitor-grade tantalum powder.