Surface Mount Resistors

4.7kΩ SMD Resistor

Surface Mount Resistors or SMD Resistors, are very small rectangular shaped metal oxide film resistor. They have a ceramic substrate body onto which is deposited a thick layer of metal oxide resistance. The resistive value of the resistor is controlled by increasing the desired thickness, length or type of deposited film being used and highly accurate low tolerance resistors, down to 0.1% can be produced. They also have metal terminals or caps at either end of the body which allows them to be soldered directly onto printed circuit boards.

Surface Mount Resistors are printed with either a 3 or 4-digit numerical code which is similar to that used on the more common axial type resistors to denote their resistive value. Standard SMD resistors are marked with a three-digit code, in which the first two digits represent the first two numbers of the resistance value with the third digit being the multiplier, either x1, x10, x100 etc. For example:

"103" = 10 × 1,000 ohms = 10 kiloΩ´s

"392" = 39 × 100 ohms = 3.9 kiloΩ´s

"563" = 56 × 1,000 ohms = 56 kiloΩ´s

"105" = 10 × 100,000 ohms = 1 MegaΩ

Surface mount resistors that have a value of less than 100Ω's are usually written as: "390", "470", "560" with the final zero representing a 10 x^o multiplier, which is equivalent to 1. For example:

"390" = 39 × 1Ω = 39Ω´s or 39RΩ

"470" = 47 × 1Ω = 47Ω´s or 47RΩ

Resistance values below ten have a letter "R" to denote the position of the decimal point as seen previously in the BS1852 form, so that 4R7 = 4.7Ω.

Surface mount resistors that have a "000" or "0000" markings are zero-Ohm (0Ω) resistors or in other words shorting links, since these components have zero resistance.

In the next tutorial about Resistors, we will look at connecting resistors together in a series chain and prove that the total resistance is the sum of all the resistors added together and that the current is common to a series circuit.