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 fast and easily.
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 1000Ω, 1MΩ equals to 100000Ω.
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 10000Ω, 391 means 390Ω, 473 means 47000Ω.
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, 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 unit μF, nF, pF. 1μF equals to 1000nF, 1nF equals to 1000pF.
There are two methods to indicate the capacitance value on the SMD capacitors' appearance.
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:
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 then sintered. On SMD capacitors, 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.
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.
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 1000mH, and 1mH equals to 1000μH.
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, 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, inductors on an extremely small semiconductor then packaged. 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 from 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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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 of SMD components or PCBs, welcome to contact PCB-HERO by email or from the online chat window on the right of our website pages.