Classification by structure

Classification of resistors

There are various resistors depending on the combination of function, shape, resistive material, and application.

Categorized by function, there are three types of resistors; fixed resistors, used in a electric circuit; trimmer potentiometer to adjust a circuit; variable resistor, used as a radio volume by changing the resistance.

Fixed resistors are divided into leaded type (with lead wire) and surface mount type (without lead wire). Surface mount type includes rectangular type and cylinder type. In addition, division goes further depending on the sealing material: resin mold type and ceramic case type.

As for the material of resistive element, followings are available: carbon film, metal film consist mainly of nichrome, metal oxide film, metal glaze composites consist of metal oxide and glass; ones with metal plate, metal wire or metal foil; solid type consist of metal oxide ceramics.

Regarding the characteristics of resistors, there are those with highly accurate resistance tolerance and temperature characteristics, those withstand high voltage and surge, those with large fluctuations in resistance value depending on temperature, and those that also have a fuse function.
It is important to select an optimal combination out of available options according to the purpose of the application when selecting a resistor.

image of categories of fixed resistor

image of categories of trimmer potentiometers

image of categories of potentiometers

Characteristics of fixed resistors

Chip type fixed resistors

Resistors with terminals that have been treated for soldering or bonding and do not have terminal wires (lead wires). They can be divided into rectangular type and cylindrical type. Five types depending on the resistive material are shown below.

  • Rectangular type…1. Metal glaze film type, 2. Metal film type, 3. Metal plate type
  • Cylindrical type...4. Carbon film type, 5. Metal film type

Among them, the metal glaze film type accounts for the majority of the market in terms of cost, downsizing, and ease of mounting. Some statistics show that more than 90% of chip fixed resistors are metal glaze film type.

The trend of downsizing is remarkable in the chip type, and the demands has been increasing for 1005 size (1.0 mm x 0.5 mm) and 0603 size (0.6 mm x 0.3 mm) for the rectangular type. The adoption of 0402 size (0.4 mm x 0.2 mm) has been advancing for mobile communication devices such as mobile phones and smartphones.

Rectangular type chip fixed resistors
This type can be roughly divided into thick film metal glaze type and thin film metal type. Mass production is mainly on thick film type. The thick film type features excellent mountability and environmental resistance, whereas the thin film type features small resistance tolerance, small T.C.R. and low current noise. In particular, the T.C.R. of the thick film type is around 25×10-6/K, while that of the thin film type is as small as around 5×10-6/K, making its resistance value stable over time.

The size of rectangular type resistor has been standardized in 0402, 0603, 1005, 1608, 2012, 3216 (mm code). The demand for 0403 size in particular is rapidly increasing among mobile communication devices. 0603, 1005 and 1608 size are widely used for applications in consumer products, industrial equipment and automotive. High power type has 3216, 3225, 5025 and 6331 size in the lineup. Recently, wide terminal types that provide higher rated power compared to chip resistors of the same size, have been developed in 0510, 0816, 1220, 1632, 2550, and 3163 size.

Cylindrical chip fixed resistors
Commonly known as MELF (Metal Electrode Leadless Face), a type of chip resistor with a structure of a general type axial lead resistor without the lead wire but with the metal plated cap attached to the electrodes at both ends. Its cylindrical shape and metal cap eliminate the concept of front and back, give excellent electrode and mechanical strength, and have precise structural dimension that achieves high precision in supplying and mounting of resistors. In addition, the metal film type is excellent in the resistance accuracy, T.C.R., and suppressing current noise.

Network resistors (Resistor networks)

Resistor network in which two or more resistive elements are integrated and combined on an insulating substrate to form a single electronic component. Each element can be connected as necessary. An array is simply a continuous integration of resistors with two electrodes, while a network is a integration of formed circuit. The main applications are pull-up and pull-down resistors for digital circuits.

Depending on the shape, they can be classified into SIP (Single Inline Package) type, DIP (Dual Inline Package) type, flat package type, and chip carrier type.

In the 1980s, when the production of carbon film resistors was the mainstay, the production volume of SIP type drastically increased to support high-density mounting. However, in the 1990s as mounting technology took a change to surface mounting, chip network resistors began to be used. In the past, network resistors were often used around logic ICs and parallel ports for I/O, but since the processing by microcomputers and use of serial buses for I/O have progressed, the demand of network resistors has been declining significantly.

Leaded type fixed resistors

Carbon film fixed resistors

Fixed resistors with excellent pulse resistance that use a carbon film as a resistive element, and have long been the most popular resistor.
In terms of electric power, 1/4 W and 1/2 W types are mainly in the marketplace. Small types such as 1/4W type of 3.2 mm x 1.9 mm size and 1/2 W type of 6.3 mm x 2.85 mm size are mainstream and widely used as general-purpose products.

Metal film fixed resistors

Fixed resistor with a metal film as a resistive element, which provides small resistance tolerance, T.C.R., less aging variation, high accuracy, excellent stability and low current noise. The main applications include industrial equipment such as telecommunication and measuring equipment, as well as automobiles and sensor modules, which require the high precision for circuits to handle minute signals.

Metal oxide film fixed resistors

Fixed resistor with a metal oxide film as a resistive element, which provides high power rating in small size (the smallest volume per rated power among all the resistors), and an excellent heat resistance. Low T.C.R. is achievable at a lower cost compared to power type metal film resistors. Main application includes power supply circuit..

Wire-wound fixed resistors

Fixed resistor with a metal resistive wire as a resistive element. It has excellent pulse resistance and heat resistance. It's low T.C.R. achieves the low current noise. On the other hand, it is difficult to obtain a high resistance value, and the winding structure makes it unsuitable for high-frequency circuits.
It is mainly used as a precharge resistor in power supply circuits. Ones with low resistance are used for current sensing.

・Almanac of Electronic Components 2019(publicated by Chunichi-sha)
・Statistical data by "Ministry of Economy, Trade and Industry" in Japan