What is a Tantalum Capacitor – Differences and Its Applications

A high-performance tantalum capacitor offers designers a reliable and stable high-capacitance solution. With nearly 60 years of utilization, Tantalum capacitors are employed in developing various applications for industries like military and commercial avionics, industrial automation and control systems, critical and implantable medical electronics, smartphones, laptops, desktops, and notebook computers. Bell Laboratories, during the early 1950s, invented solid Tantalum capacitors as a highly advanced and greatly reliable low-voltage support capacitor. This article discusses an overview of the tantalum capacitor.

What is Tantalum Capacitor?

An electrolytic Tantalum capacitor comprises a tantalum metal – acting as an anode, hemmed in an anodic oxide layer of oxide – employed as a dielectric, which is further enclosed by either a liquid or solid electrolyte as a cathode. As manganese dioxide (MnO2) offers self-healing features to ensure long-term reliability, it is used as the cathode.

The Tantalum capacitors are extremely stable, smaller and lighter and have lower maximum working voltage and capacitance. These capacitors leak less current and have less inductance, hence, they are not suitable for high-frequency coupling circuits.

Polarity and Markings

The tantalum capacitor polarity and markings are discussed below.

• Tantalum capacitors are innately polarized capacitors with positive and negative lead and are appropriate with DC supplies. The polarity and markings on the capacitors make it easy to identify the anode and cathode.
• Two bands and a positive sign helps in identifying the value of capacitance and maximum working voltage.
• However, the top most value to the left reveals the capacitance value in microfarads (uF). For example, the value in the given below figure is 2.2 uF.
• The voltage below the capacitance value is the maximum working voltage of a capacitor, i.e., 25V.
• A positive (+) sign is noticed below the long band. The combination of a long band and a “+” sign indicates that this side has a positive lead/anode, while the other side indicates a negative lead/ cathode.
• The reverse voltage or wrong connection could damage the capacitor.
• Tantalum Electrolytic
• Tantalum Capacitor Failure

In Reverse Bias Behavior of Surface Mount Solid, Tantalum Capacitors explains that the Tantalum capacitors are designed to operate only in forward voltage biased conditions and fail if a reverse voltage is applied, which includes quick turn on from a low impedance circuit, or occurrence of a current spike during its operation.

Failure Mode of Capacitor

The paper published by ASM International clearly states that Tantalum capacitor failure mode is divided into three main categories

 High Leakage/Short

Applying reverse voltage may produce high leakage currents, which generally occurs during troubleshooting, malfunctions, and/or bench testing. Tantalum capacitors with crystallization cause short circuit failure because of the hotspots formed during crystallization heats the cathode.

 High Equivalent Series Resistance (ESR)

The ESR of a capacitor is strongly affected by the mechanical/thermomechanical if exposed to board mounting, pick-and-place, reflow, and application lifetime. Such type of stress is often compromised in external and/or internal connections, leading to high ESR.

Low Capacitance/Open

As the capacitance of a Tantalum capacitor does not change under normal operating conditions, the failure is uncommon. The lower capacitance of a Tantalum capacitor in any application can be an indication of a shorted capacitor, while Open failure can be a result of compromised damaged positive lead and wire connection.

SMD Sizes and Uses

Tantalum capacitor offers major features like extreme stability, reliability, and low current leakage. These features enable capacitors to be applied in –

• Sample and hold circuit to achieve long hold duration
• Power supply rail decoupling offering higher efficiency with lower ESR
• Extremely efficient packaging systems
• Applications related to military and aerospace industries
• Life-sustaining medical devices
• Space equipment for higher reliability

Motherboards for power supply filtering, and many more generally, the highest number of Tantalum capacitors are mass-produced as a tantalum chip capacitor in the form of SMD (surface mount device). It is designed with contact surfaces on both sides of a case. Following the EIA-5335-BAAC standards, Tantalum chip capacitors are designed and produced in different styles.

Differences Between Tantalum and Ceramic Capacitor

The tantalum & ceramic capacitor are discussed below.

In the field of electronics, Tantalum and ceramic capacitors are broadly accepted to design various suitable applications. Let’s see below the differences between both.

Advantages and Disadvantages

The list of the advantages and disadvantages of a solid tantalum capacitor include the following

The advantages are: Long life, high-temperature resistance, excellent performance, high accuracy, efficiency in filtering high-frequency harmonics.

The disadvantages are: Having a very thin oxide layer that is not robust, cannot withstand voltage above limits, low ripple current rating.

Applications of Tantalum Capacitor

Tantalum capacitors offer various benefits and therefore, utilized in various applications, particularly in modern electronics for higher stability to withstand a range of temperatures and frequencies, long-term reliability and record-high volumetric efficiency.

A tantalum capacitor is a demanding component for cardio implants to automatically sense the irregular heartbeats and give an electric countershock in few seconds. This capacitor finds its stance in the most demanding industry verticals like medical, telecommunications, aerospace, military, automotive, and computers.

FAQs

1). Name some applications of wet tantalum capacitors?

It is used in industries like telecom, avionics, space, medical, telecom, consumer applications.

2). What is surge voltage in terms of the tantalum capacitor?

A surge voltage is the highest voltage that can be applied to a capacitor for a shorter period in circuits that has minimum series resistance.

3). What is reverse voltage? What happens to the tantalum capacitor when a reverse voltage is applied?

Reverse voltage is where the anode electrode voltage is negative concerning cathode voltage. With a reverse voltage, a reverse leakage current flows in small micro-cracks or defects across the dielectric layer to the anode of the capacitor.

4). What are the various dielectrics used to manufacture the tantalum capacitor?

• Manganese dioxide electrolyte
• Tantalum pentoxide, Ta2O5
• Niobium Pentoxide, Nb2O5

5). Explain the polarity marking of a tantalum capacitor

The polarity and markings on the capacitors make it easy to identify the anode and cathode.

• Two bands and a positive sign helps in identifying the value of capacitance and maximum working voltage.
• However, the top most value to the left reveals the capacitance value in microfarads (uF). For example, the value in the given below figure is 2.2 uF.
• The voltage below the capacitance value is the maximum working voltage of a capacitor, i.e., 25V.
• A positive (+) sign is noticed below the long band. The combination of a long band and a “+” sign indicates that this site has a positive lead/anode, while the other side indicates a negative lead/ cathode.
• A reverse voltage or wrong connection could damage the capacitor.

6). Define impedance

Impedance is the total resistance in ohms of any network at a specific frequency, including angular parts of both the real and imaginary.

7). Give one difference between Tantalum and Ceramic capacitor.

In the Tantalum capacitor, capacitance instability is not exhibited concerning the applied voltage, whereas, ceramic capacitor exhibits capacitance changes concerning an applied voltage.

Nevertheless, Tantalum capacitors are trusted by designers as reliable components. It’s enhanced features such as lower weight, low current leakage, and high capacitance per volume allows capacitance to be used in a wide variety of applications. The tantalum capacitor should be connected appropriately to avoid any damage.

High leakage/ short, ESR, and Low capacitance/Open are the three main reasons for capacitor failure. Manufacturers and designers must ensure to provide protection against and long-term reliability. Offering outstanding traits makes Tantalum capacitors to be utilized in almost every industry to develop a suitable application.