Last Updated on October 22, 2023 by Kevin Chen
Surface-mount technology (SMT)-based components such as resistors, capacitors, and other electronic components are utilized in large quantities. SMT is a PCB design technique that differs from through-hole (TH). SMT (surface mount technology) is a method of directly attaching electrical components to a PCB (printed circuit board). SMD refers to the method of mounting a component in this manner (surface-mount device).
Most industries, including consumer electronics, are currently utilizing this technology since it enhances reliability, manufacturing, high levels of functionality, and reduces cost and space. We can improve the efficiency of printed circuit boards without sacrificing quality or reliability by employing this technology. Surface mount devices (SMDs) replace bulkier, bigger, and heavier elements in a through-hole PCB design. This page aims to provide an understanding of SMD resistors, how they work, and how they might be used.
What is an SMD Resistor?
The term Surface Mounted Device is abbreviated as SMD. Surface Mount Technology allows an electronic component to be directly affixed to a PCB circuit board (SMT). These resistors can be found on professionally constructed PCBs, although for most homebrew designs, through-hole technology resistors would do. This is because through-hole resistors are simple to install and do not require the use of specialized equipment as SMD resistors do.
Surface mount technology was created to minimize the number of components and the time it takes to build a circuit. The SMT enhances manufacturing by allowing for a high level of automation while also increasing dependability. It also provides greater capability to be achieved in a smaller space, dramatically lowering costs.
In terms of quantity used, surface mount resistors are the preferred form for practically all electronic equipment. Surface-mount resistors also have the same capability as typical axially leaded resistors but with less heat dissipation. They are frequently used to reduce stray capacitance and inductance. The device comes in all common values, from E3 to E192, and in various sizes, some of which are too small to be handled manually.
Surface Mount Technology
Surface-mount resistors are one type of electrical component that leverages this technology. Because it allows for considerably faster and more reliable assembly of electronic PCB, this type of component technology has become standard in manufacturing electronic equipment.
Surface mount components were originally designed to make it easier and more reliable to utilize automatic pick and place machines. Surface mount technology, namely SMD resistors, allows electronic circuit fabrication much quicker and the completed product much more reliable nowadays.
The surface mount technique allows components to be directly soldered to the PCB. This eliminates the requirement for leads to connect the element body to the board and the need for leads to pass through the board, which has traditionally been problematic in automated manufacturing.
SMD Resistor Construction
The rectangular shape of the SMD resistor can be used in its manufacture. A metalized area is available on any of the resistor’s faces, allowing soldering to connect the component to the PCB.
One of the parts of this resistor that can have a metal oxide coating placed on it is the ceramic substrate. The length and thickness of the actual film can be used to determine the resistance of this resistor.
The metal oxide is essential in SMD resistors because it allows the resistor to remain stable by keeping the tolerance level high. This resistor’s ceramic substrate element comprises high alumina ceramic, which provides solid insulation on the base of the resistive metal oxide element on which the SMD resistor is placed.
The contact between this resistor and a chip resistive element must be reliable and provide extremely high degrees of solderability. The nickel-based layer can be used to construct an internal link to obtain these high levels. Furthermore, the exterior coating, built on the tin, can be used to make the external connection, resulting in extremely high levels of solderability.
SMD Resistor Packages
When referring to an electrical component’s size, shape, or lead configuration, we use the phrase “package.” The resistor package designators indicate the length and width of SMD resistors. Both millimeters and inches can be used to measure SMD packages. Examining the manufacturer’s paperwork is crucial for this reason. Most manufacturers use the JEDEC standards and have standardized the size and shape of surface mount resistors. An alphanumeric identifier, like 0603, is used to identify the size of SMD resistors. This code specifies the width and length of the package.
When compared to other components, resistors have a relatively high failure rate. However, this rate will increase under high temperatures and pressures; therefore, in some cases, we must carefully evaluate the resistor’s life. The following factors can influence the life of a resistor.
- If the temperature is too high, the resistor can be damaged.
- The alkalinity and acidity of the environment corrode the resistance and harm it.
- The resistance will shatter when the outside force surpasses a predetermined limit.
To solve these problems, the resistor’s life must be extended by ensuring adequate power dissipation, keeping a dry environment free of toxins, and avoiding external stresses. A resistor with a high resistance value has a long-life expectancy.
SMD resistor requirements vary due to the various manufacturers. As a result, when selecting an SMD resistor, it’s critical to check the manufacturer’s rating. However, some typical specifications must be understood to have a thorough grasp of SMD resistors, such as temperature coefficient, power rating tolerance, etc.
In comparison to wire-ended components-based circuit designs, the power rating of SMD resistors-based circuit designs employs much lower levels. This resistor’s power rating is mainly determined by its size. The power ratings of various sizes of SMD resistors can be simplified. The chart below shows a typical power rating for some of the most commonly used SMD resistor sizes. Please remember that this is only a guideline; actual results may differ depending on the manufacturer.
|TYPICAL SMD RESISTOR POWER RATINGS|
|PACKAGE STYLE||TYPICAL POWER RATING (W)|
|0402||0.0625 – 0.031 (1/16 – 1/32)|
Despite the fact that most manufacturers claim that their SMD resistors power levels are high than the once outlined above; as a result, it is always preferable to de-rate components rather than run them at their maximum ratings. The reliability will be improved by lowering the rating to 0.5 or 0.6.
SMD resistors have a good temperature coefficient thanks to the metal oxide film. They come in a variety of ppm / 0c levels, including 25, 50, and 100 ppm / 0c. The technology utilized in SMT resistors is far superior to that used in ordinary resistors. The circuits have substantially improved temperature stability with this new technology.
Metal oxide film resistors require relatively tight tolerance values when being manufactured. The numbers accessible are 5%, 2%, and 1%, with 0.5 percent and 0.1 percent values possible in select specialty applications. Even though close tolerance resistors aren’t always necessary, their use will improve repeatability from one module or circuit to the next. The number of high-tolerance components in the circuit is reduced as a result. The 2 percent resistors are more costly than the 5 percent resistors. Still, they are more extensively used, and using 0.5 percent and 0.1 percent tolerance SMT resistors is rarely required unless in extreme cases. They will very certainly be more expensive than the 2% electronic components.
Advantages and Disadvantages of SMD Resistors
The following are some of the advantages of SMD resistors in various applications:
● Surface-mount resistors are, by definition, significantly smaller than traditional resistors.
● These resistors’ size and construction reduce inductance, which means they have significantly lower amounts of stray capacitance and inductance.
● This is why they are utilized for procedures with a considerably higher frequency.
● SMT resistors can be made with very tight tolerances.
● They have long-term resistance stability and a high resistance temperature coefficient.
Despite the benefits of SMT resistors, there are still certain restrictions. In their many uses, SMT resistors have the following drawbacks:
- Surface-mount resistors have a lower power rating than standard resistors.
- They’re used in applications with lower circuit levels.
- Extreme caution and focus are essential to guarantee that power ratings are not exceeded.
- Surface-mount resistors frequently need to be reworked.
- To fix them, you’ll need a different kind of technology.
- The part is really little.
Last but Not Least
Surface mount technology (SMT) was employed to fabricate the SMD resistors, which provided significant benefits in terms of space savings and automated printed circuit board manufacturing. Surface-mount resistors are widely used, and almost all industrial and professional electronics today use them. These resistors are often much smaller than standard resistors and are engineered to be surface mounted. As a result, they occupy less space on a circuit board.
Surface-mount resistors (SMD resistors) utilize surface mount technology (SMT) to provide significant benefits in terms of space savings and automated printed circuit board manufacturing. Surface Mount Technology allows an electronic component to be placed directly on a Printed circuit board (SMT). This concludes the discussion of SMD resistors’ definition, applications, construction, packaging, specifications, and marks in this article.
For more details on SMD resistors, contact us at ICRFQ. We manufacture the best electrical components in China.
If you want to find more Electronic Components Distributors, please check out the following articles:
- The Art of Sourcing: How We Identify and Partner with Top IC Manufacturers - November 24, 2023
- Essential Electronics Test Equipment You Should Know About - November 24, 2023
- How To Finish PCBA Design Process Quickly? - November 24, 2023