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.
- 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.
- 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.
Of course, you could find other ways to identify SMT resistor.
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.
- Directly denote the capacitance and working voltage on the capacitors, for example, 10μF/16V.
- 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 × 107pF (= 100μF), 225 means 22 × 105pF (=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.