What is a MELF Resistor? Introduction to Cylindrical Leadless Packaged Resistors
A resistor is one of the most common passive components, typically made of a resistive element with a specific resistance value and an outer packaging. It is primarily used to limit or adjust current and voltage, divide voltage, and protect circuits. The most common types of resistors on circuit boards are cylindrical through-hole resistors (Figure 1 left) and surface-mounted chip resistors (Figure 1 right).
However, due to their large space occupancy, through-hole resistors mounted on PCBs have been gradually decreasing in modern consumer electronics trends toward miniaturization, replaced by smaller, easier-to-solder chip resistors. Yet, chip resistors have some disadvantages such as smaller size leading to difficult heat dissipation, generally lower resistance values, and lower power tolerance. To address these issues, a new type of resistor combining the characteristics of the two mentioned resistors was developed: the MELF resistor.
(Extended Reading: What is a Chip Resistor?)
1. Structure and Principle of MELF Resistors
MELF resistors, also known as cylindrical surface-mount resistors, are a type of resistor that uses a Metal Electrode Leadless Face (MELF) package; they resemble through-hole resistors in appearance but have no leads for connection like chip resistors and are installed by surface adhesion (as shown in Figure 2).
As seen in the image, MELF resistors retain a cylindrical shape and structure but can also be directly soldered onto a PCB like chip resistors.
2. Advantages of MELF Resistors
The results show that under the same test conditions, ordinary chip resistors cannot withstand this pulse energy as well as MELF resistors. Moreover, due to their larger volume, MELF resistors also have a stronger heat dissipation capacity, especially when paired with fan cooling.
Image 4: Heat Dissipation Capabilities Comparison between MELF and Chip Resistors
Another advantage of MELF resistors is their sulfur resistance. Typical chip resistors with silver material on the electrode layer can produce silver sulfide corrosion when exposed to sulfur gas over time, causing changes in resistance values. MELF resistors, made with a nickel-chromium alloy film and without silver materials in the process, do not suffer from silver sulfide corrosion.
Furthermore, MELF resistors also exhibit mechanical characteristics such as resistance to vibration and deformation, making them widely used in products requiring high reliability.
Although MELF resistors have many advantages over chip resistors, they also have some drawbacks, such as higher cost and larger space occupancy. It is advisable to evaluate the application scenario in advance before choosing which type of resistor to use. If you have questions about the specifications and characteristics of various resistor products, please feel free to contact us.
3. Taiwan MELF Resistor Manufacturer - Firstohm
First Resistor & Condenser Co. Ltd. (Firstohm), a professional MELF resistor manufacturer in Taiwan, has been established since 1969 and has over 50 years of history. In addition to deep-rooted experience in the passive component industry, it actively pursues product development and market breakthroughs.
Firstohm offers various types of resistors, such as surge-resistant, high-voltage, precision resistors, and also provides custom-designed resistors based on customer needs, covering applications from energy and industrial control to automotive industries.
Horustech Electronics is an authorized distributor for Firstohm. If you have any related component needs, please contact us.
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Intro video of Firstohm MELF resistors
