What is SMD Resistor : Working & Its Specifications

SMT or Surface mount technology gives various benefits in the production of electronic devices. Usually, electrical and electronic components include leads and the arrangement of these can be done through the hole on the PCB or printed circuit board. But, SMT replaces the leads of components with contacts. So that components can be placed directly over the PCB to allow easy soldering. There are different kinds of components are used from SMD like SMD capacitor, SMD resistor, etc. These components use surface mount technology to use in different electronic device manufacturing industries. So it allows a very fast & consistent design of electronic PCBs.

What is SMD Resistor?

Definition: The resistor which uses surface mount technology is known as SMD resistor. These resistors are used in huge quantities. In most of the manufacturing industries, this technology is used. This technology improves by allowing high levels of automation, manufacturing, improves reliability, high range of functionality in small size and decreases the cost drastically.

SMD resistors give low power dissipation, low stray capacitance, and low stray inductance. These components are accessible in different sizes with popular values like E3 to E192 but some of them are now tiny & not easy to handle physically. These resistors resist the electrical current flow, protect, operate, otherwise controls circuits. Each resistor will have permanent resistance value otherwise they may be changeable in a certain range. These components will reduce current or voltage signals. These are the basic building blocks in modern electronic devices.

SMD Resistor Construction

These resistors are available in a rectangular shape and also called chip resistors. One side of the resistor is metalized and they can be arranged on PCB through its pads. The construction of an SMD resistor is shown below.

The design of this resistor can be done using a ceramic/alumina substance. The resistance of the resistor can be calculated based on the thickness, length, and material used. These resistors are enclosed using a protective coat with successive layers. The layers of the protective coat avoid mechanical damage, however, it stops the ingress of wetness & other pollutants.

These resistors are manufactured using metal film or metal oxide. These are protected through the robust coating. So these are stable with good time tolerance as well as good temperature. The cross-section of this resistor will show the resistive element & other regions.

The termination of this resistor at each end will be the total act of the resistor. Here a nickel layer is used in the internal connection of the resistor element & terminations. The external layer of this uses a tin-based layer to give high-quality solderability for these components.

SMD Resistor Packages

The SMD resistor packages and their sizes are listed below. For different package styles, the dimensions in mm and in inches are given below.

• For 2512 package style, the sizes are 6.30 x 3.10 mm and 0.25 x 0.12 inches
• For 2010 package style, the sizes are 5.00 x 2.60 mm and 0.20 x 0.10 inches
• For 1812 package style, the sizes are 4.6 x 3.0 mm and 0.18 x 0.12 inches
• For 1210 package style, the sizes are 3.20 x 2.60 mm and 0.12 x 0.10 inches
• For 1206 package style, the sizes are 3.0 x 1.5 mm and 0. 0.12 x 0.06 inches
• For 0805 package style, the sizes are 2.0 x 1.3 mm and 0.08 x 0.05 inches
• For 0603 package style, the sizes are 1.5 x 0.08 mm and 0.06 x 0.03inches
• For 0402 package style, the sizes are 1 x 0.5 mm and 0.04 x 0.02 inches
• For 0201 package style, the sizes are 0.6 x 0.3 mm and 0.02 x 0.01inches

Specifications

These resistors are designed by different manufacturing companies based on the specifications. So it is mandatory to check the rating of manufacturers for this resistor. But it is achievable by making some generalizations of the ratings. SMD resistor specifications include the following.

• Power Rating
• Temperature coefficient
• Tolerance

Power Rating

While designing any component, the power rating requires careful consideration. In SMD resistors, the power levels which can be dissipated are lesser compare with the circuits which use wire ended components. Some of the power ratings of different sizes of SMD resistors are listed below. The power ratings will be changed based on the manufacture & its type.

• For the 2512 package style, the power rating is 0.50 (1/2) W
• For the 2010 package style, the power rating is 0.25 (1/4) W
• For the 1210 package style, the power rating is 0.25 (1/4) W
• For the 1206 package style, the power rating is 0.125 (1/8) W
• For the 0805 package style, the power rating is 0.1 (1/10) W
• For the 0603 package style, the power rating is 0.0625 (1/16) W
• For the 0402 package style, the power rating is 0.0625 to 0.031 (1/16 to 1/32) W
• For the 0201 package style, the power rating is 0.05 W

These are the typical power ratings for different package styles. Similar to all the components, the maximum rating of this must be 0.5 otherwise 0.6.

Temperature Coefficient

By using a metal oxide film, these resistors will give a good temperature coefficient. The technology used in this resistor is better when compared with lead resistors. Based on that, it will provide good temperature stability in different circuits.

Tolerance

The relative tolerance values of this resistor are 1%, 2%, and 5%. These are designed through the metal oxide film.

SMD Resistor Markings

SMD resistors are very small in size like 0201. When the resistors are frequently loaded within reels on the machine, it will place automatically, and then the reel is marked. Once the resistors are marked, then figures are used before the color codes utilized in leaded components. There are different kinds of coding systems are used which use three or four-digit numbers. These numbers are known as resistor codes. By using these codes, the resistance values of the resistor can be identified. These numbers include a multiplier and two important figures.

Advantages

SMD resistor advantages are

• Size
• The inductance will be reduced
• Tolerance
• Accuracy

Disadvantages

SMD resistor disadvantages are

• Rework
• Power rating

Thus, this is all about an overview of the SMD resistor. Every year, the production of these resistors is in billions. So these are available in each electronic and electrical circuit. These are very easy to design and used particularly when used in capacity at extremely low cost. The technology used in this resistor is SMD.