How to Identify SMD Components from Appearances

SMD components, or surface mount components, are electronic components to be mounted on printed circuit boards to function. How to identify SMD components from their appearances? This article will guide you to identify surface mount components quickly and easily.

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Part 1: Identify SMD Resistors

SMD resistors are basic surface mount components that limit the current passing through them. "R" stands for resistance, and the unit of resistance is Ohm (Ω). 1KΩ equals to Ω, 1MΩ equals to Ω.

There are two methods to indicate the resistance value on the SMD resistors' appearance.

1. In Arabic numbers: the first two numbers indicate the absolute numbers of the resistance value, and the last number means the power of 10.

For example, 103 means Ω, 391 means 390Ω, and 473 means Ω.

2. In a combination of Arabic numbers and R: the Arabic numbers before the R stand for the whole part of the resistance value, and those after the R stand for the fractional part of the resistance value.

For example, R100 means 0.100Ω, 5R60 means 5.60Ω, 30R9 means 30.9Ω.

Classification of SMD resistors: according to the use differences, there are normal resistors, precision resistors, power resistors, high voltage resistors, high-resistance resistors, and high-frequency resistors.

Part 2: Identify SMD Capacitors

SMD capacitors are PCB parts consisting of two metal pieces separated by an insulator and mainly used to store energy. " C" stands for capacitance, and the unit of capacitance is Farad (F).

The unit F is too big for SMDs' capacitance, and we usually use the smaller units μF, nF, and pF. 1μF equals to nF, 1nF equals to pF.

There are two methods to indicate the capacitance value on the SMD capacitors' surface.

1. Directly denote the capacitance and working voltage on the capacitors, for example, 10μF/16V.

2. In a combination of Arabic numbers and working voltage: the first two numbers indicate the absolute numbers of the capacitance value, and the last number means the power of 10.

For example, 107 means 10 × 10^7pF (= 100μF), 225 means 22 × 10^5pF (=2.2μF)

Besides, on SMD capacitors, the capacitance is denoted by a combination of numbers and a letter.

The letter stands for capacitance tolerance. Here is a chart:

Letter

F

G

J

K

L

M

Tolerance

±1%

±2%

±5%

±10%

±15%

±20%

For example, 104J means 10 × 104pF (= 0.1μF), and the capacitance tolerance is ±5%.

Classification of SMD Capacitors

Ceramic capacitors: made up of a ceramic insulator with two terminals sprayed with silver and then sintered. On SMD capacitors' surface, C.CAP stands for ceramic capacitors.

Aluminum electrolytic capacitors: made up of an aluminum cylinder filled with liquid electrolyte (together as the negative electrode) and a curly aluminum strip (as the positive electrode) covered with an oxide film (as the insulator) plugged in it.

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Additional reading:
Surface Mount Technology Ltd vs Traditional PCB Assembly: Key Differences

Tantalum electrolytic capacitors: made up of tantalum or niobium (as the positive electrode) and dilute sulfuric acid (as the negative electrode), the oxide film covered on tantalum or niobium as the insulator. TAN.CAP or TC stands for tantalum capacitors.

Note

All electrolytic capacitors are polar capacitors. The positive and negative electrodes of polar components can't be reversed during PCB assembly . On tantalum capacitors, the terminal printed with lines is the positive electrode. The sizes of tantalum capacitors from minimum or maximum are denoted by A, B, C, D ... J.

Part 3: Identify SMD Inductors

SMD inductors are basic electronic components that convert electrical energy into magnetic energy and store it. Inductors are made up of an enameled wire winding around an insulator. "L" stands for inductance, and the unit of inductance is Henry (H). 1H equals to mH, and 1mH equals to μH.

The method to indicate the inductance value on the SMD inductors' appearance is below.

In Arabic numbers: the first two numbers indicate the absolute numbers of the inductance value, and the last number means the power of 10.

For example, 470 means 47H, 101 means 100H, and 100 means 10H.

Part 4: Identify SMD Diodes and SMD Triodes

SMD diodes are unidirectional conductive electronic components. Diodes are also polar components, and the positive and negative electrodes can't be reversed. When currents flow from the positive electrode, the diode's resistance is extremely small. Vice versa, the resistance is extremely large. CR or D stands for diodes.

On SMD diodes, the terminal printed with lines is the negative electrode.

SMD triodes are control components that amplify currents. Q stands for triodes.

Part 5: Identify SMD ICs

SMD ICs are surface-mounted integrated circuits that integrate components such as diodes, resistors, capacitors, and inductors on an extremely small semiconductor and then package them. According to the packaging differences, the integrated circuits include PLCC, PPGA, PQFP, QFP, BGA, CSP, SSOP, etc.

Part 6: Identify SMD Crystal Oscillators

An SMD crystal is a quartz piece with two terminals polished and sprayed with a silver film. When an IC is packaged with the quartz piece to form the oscillation circuit, it is an SMD oscillator. Y stands for crystal oscillators.

SMD crystal oscillators provide basic clock signals for the system.

On a component, if you see a combination of numbers and HZ or Z, that is a crystal oscillator.

You can see crystal oscillators in the below image. DIP crystal oscillators have two long pins, and the rest are SMD crystal oscillators. SMD crystal oscillators have two or four pins.

Part 7: Identify SMD Connectors

SMD connectors provide temporary or permanent electrical connections for circuits, and they are usually used in pairs.

Part 8: Identify SMD Button Switches

SMD button switches are surface mount switches that use a button to connect or separate the two contacts to realize the circuit switch.

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Conclusion

This article gives a brief introduction to common SMD components, displays their images, and provides tips to identify components from their appearances. If you have any concerns or needs for SMD components or PCBs, welcome to contact PCBONLINE by or from the online chat window on the right of our website pages.

SMD resistors are tidy and are commonly marked with three- or four-digit codes called SMD Resistor Codes that indicate their resistance values.

For a three-digit SMD Resistor Code,

• the first two numbers indicates the significant digits for the resistance, e.g. &#;22&#; indicates 22 ohms
• the third number will be a multiplier that must be multiplier by the first two numbers, or will indicate how many zeros should be added to the first two numbers. For example, &#;223&#; indicates 22 ohms multipled by 10 three times, or with three zeros, for a or 22k-ohm part.
• you may see the letter &#;R&#;, which calls out a decimal point. For example 1.1 ohms = 1R1 ohm.
• resistance values below 10 ohms do not have a multiplier.

Here are more examples for three-digit SMD Resistor Codes.

Identify Yageo ACFR-071K21L Chip Resistor Marking

Resistors

When you have an AC series chip resistor from Yageo, you can follow along with the method below to identify its resistance value. For example, ACFR-071K21L is marked 09B. &#;09B&#; is a resistance code which includes the first significant digits of the resistance value followed by the number of zeros. Using the EIA-96 Making Standard, you can identify the number of zeros from the third letter. Note that &#;09&#; is not, itself, the resistance code - this is important! It&#;s instead used to find t&#;

To read the four-digit code, use the same method as the three-digit code. The only difference is the number of significant digits. There are three significant numbers, rather than two, with the last still indicating the multiplier or how many zeros to add to the first three numbers.

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