Tantalum Capacitor Marking Codes

Tantalum capacitors are marked with codes that provide information about their capacitance value, tolerance, voltage rating, and other characteristics. The marking codes follow industry standards, making it easier for engineers and technicians to identify and select the appropriate capacitor for their needs.

EIA Standard Marking Code

The Electronic Industries Alliance (EIA) has established a standard marking code for tantalum capacitors. This code consists of three or four characters, indicating the capacitance value, tolerance, and voltage rating.

Capacitance Value

The first two characters of the EIA code represent the capacitance value in picofarads (pF). The characters are derived from a lookup table that assigns letters to specific capacitance values. For example:

Code	Capacitance (pF)
A	10
B	11
C	12
D	13
…	…
Z	35

If the capacitance value exceeds 35 pF, the code starts with a capital letter followed by a lowercase letter. For example, “Re” represents a capacitance value of 470 pF.

Tolerance

The third character in the EIA code indicates the capacitance tolerance. The tolerance is represented by a letter code as follows:

Code	Tolerance
F	±1%
G	±2%
J	±5%
K	±10%
M	±20%

Voltage Rating

The fourth character in the EIA code represents the voltage rating of the tantalum capacitor. The voltage rating is indicated by a letter code as follows:

Code	Voltage Rating (V)
A	4
B	6.3
C	10
D	16
E	20
…	…

Metric Marking Code

In addition to the EIA standard marking code, some tantalum capacitors use a metric marking code. The metric code consists of three numbers followed by a letter, representing the capacitance value, tolerance, and voltage rating.

Capacitance Value

In the metric code, the first two numbers indicate the capacitance value in picofarads (pF). If the capacitance value is less than 100 pF, the first number represents the first significant digit, and the second number represents the second significant digit. For capacitance values of 100 pF or greater, the first two numbers represent the first two significant digits.

The third number in the metric code represents the multiplier, which is the number of zeros following the first two digits. For example:

Code	Capacitance (pF)
100	10
120	12
101	100
121	1200
102	1000

Tolerance and Voltage Rating

The letter following the three numbers in the metric code indicates both the capacitance tolerance and the voltage rating. The letter code is as follows:

Code	Tolerance	Voltage Rating (V)
A	±20%	4
B	±10%	6.3
C	±5%	10
D	±2.5%	16
E	±20%	6.3
…	…	…

Types of Tantalum Capacitors

Tantalum capacitors come in various types, each with specific characteristics and applications. Understanding the different types of tantalum capacitors helps in selecting the most suitable one for a given circuit design.

Solid Tantalum Capacitors

Solid tantalum capacitors are the most common type of tantalum capacitor. They are constructed using a tantalum metal anode, a solid manganese dioxide (MnO2) electrolyte, and a cathode layer. The solid construction provides excellent stability and reliability.

Key features of solid tantalum capacitors:
– High capacitance density
– Low leakage current
– Wide operating temperature range
– Suitable for high-frequency applications

Tantalum Polymer Capacitors

Tantalum polymer capacitors use a conductive polymer as the electrolyte instead of the traditional MnO2. The polymer electrolyte offers several advantages over solid tantalum capacitors, including lower equivalent series resistance (ESR) and improved high-frequency performance.

Key features of tantalum polymer capacitors:
– Lower ESR compared to solid tantalum capacitors
– Higher ripple current capability
– Improved high-frequency performance
– Suitable for power supply decoupling and filtering applications

Wet Tantalum Capacitors

Wet tantalum capacitors, also known as liquid electrolytic tantalum capacitors, use a liquid electrolyte instead of a solid electrolyte. The liquid electrolyte provides higher capacitance and better high-temperature performance compared to solid tantalum capacitors.

Key features of wet tantalum capacitors:
– Higher capacitance values than solid tantalum capacitors
– Better high-temperature performance
– Suitable for high-reliability applications, such as aerospace and military equipment

Tantalum Foil Capacitors

Tantalum foil capacitors are constructed using a tantalum foil anode and a liquid electrolyte. They offer high capacitance values and are suitable for high-voltage applications.

Key features of tantalum foil capacitors:
– High capacitance values
– Suitable for high-voltage applications
– Good stability and reliability

FAQ

1. What are the advantages of tantalum capacitors over other types of capacitors?
   Tantalum capacitors offer several advantages, including high capacitance density, low leakage current, wide operating temperature range, and excellent frequency characteristics. They are also known for their stability and reliability.

2. How do I determine the capacitance value and voltage rating of a tantalum capacitor based on its marking code?
   The capacitance value and voltage rating can be determined by decoding the marking code on the tantalum capacitor. The EIA standard marking code uses letters to represent specific values, while the metric code uses numbers and a letter. Refer to the tables provided in the article to interpret the codes accurately.

3. Can tantalum capacitors be used in high-frequency applications?
   Yes, tantalum capacitors, particularly solid tantalum and tantalum polymer capacitors, are suitable for high-frequency applications. They offer low ESR and good high-frequency performance, making them a good choice for power supply decoupling and filtering applications.

4. Are there any precautions to take when using tantalum capacitors?
   Yes, there are a few precautions to keep in mind when using tantalum capacitors. Tantalum capacitors are sensitive to voltage spikes and reverse voltage, so it is essential to ensure that the applied voltage does not exceed the capacitor’s rated voltage. Additionally, tantalum capacitors can be prone to ignition under certain conditions, such as excessive current or voltage, so proper circuit design and protection measures are crucial.

5. How do I select the appropriate tantalum capacitor for my application?
   When selecting a tantalum capacitor, consider factors such as the required capacitance value, voltage rating, tolerance, ESR, and operating temperature range. Determine the specific requirements of your application and choose a tantalum capacitor type that meets those needs. Consult the manufacturer’s datasheets and application notes for detailed specifications and guidelines.

By understanding the fundamentals of tantalum capacitor marking and the various types of tantalum capacitors available, engineers and technicians can make informed decisions when selecting and using these components in their designs. Proper selection and application of tantalum capacitors ensure optimal performance, reliability, and longevity in electronic circuits.