Leaded resistors – find manufacturers and suppliers

In contrast to SMD resistors, leaded resistors have connecting wires (pins or leads) that are inserted into a circuit board through drilled holes and soldered from below (THT technology: through-hole technology).

Leaded resistors are often larger, more robust and mechanically more stable. They are easy to assemble manually or automatically and are used today primarily in areas where higher power is required, mechanical loads can occur or ease of repair is important.

Below you will find an overview of the functionality, structure and types, special designs, labeling and resistance values as well as the load capacity and tolerances of leaded resistors, plus an overview of their areas of application and their advantages and disadvantages:

Functionality of leaded resistors:

The basic function of a resistor always remains the same, regardless of whether it is wired or SMD: It opposes the electric current with a defined resistance.

The physical relationship is described by Ohm's law: U = R \ I where U is the voltage in volts, I is the current in amperes and R is the resistance in ohms.

The task of a resistor is therefore to limit current, divide voltage or specifically influence electrical signals.

Structure and types of leaded resistors:

Leaded resistors are available in various designs. The most important are:

1. Carbon film resistors:
   A carbon layer is applied to a ceramic carrier. Simple and cheap, but less common today.
2. Metal film resistors:
   A very thin metal layer is applied to ceramic and finely trimmed. More precise and temperature-stable.
3. Wire-wound resistors:
   A resistance wire, e.g. constantan, is wound around a ceramic core.
   This design allows higher power and voltages.
4. Metal oxide or metal film resistors:
   Variants with special temperature and load capacity.

The actual resistance value is precisely set by the material, geometry and manufacturing techniques.

Special designs of leaded resistors:

There are many special forms of leaded resistors:

1. Safety resistors (fusible resistors):
   These burn out in a controlled manner in the event of an overload.
2. Cemented power resistors:
   Resistors with high load capacity and robust insulation.
3. Low-inductance wirewound resistors:
   These are suitable for high-frequency applications.
4. High-voltage resistors:
   Resistors with large spacing and special coatings.

Labeling and resistance values of leaded resistors:

Leaded  resistors are usually coded with color rings. Each ring stands for a digit or a multiplier. This colour coding is standardized worldwide (e.g. according to IEC).

The color rings indicate the two (or three) digits of the value, the multiplier in a power of ten and optionally the tolerance, e.g. gold for ±5 %, brown for ±1 %.

Load capacity and tolerances of leaded resistors:

Leaded resistors are available in many power ratings:

1. Standard types such as 0.25 W, 0.5 W, 1 W.
2. Power resistors 5 W, 10 W or more.
3. Special types with heat sinks or ceramic sleeves for even higher loads.

The tolerance indicates how exactly the actual value corresponds to the nominal value:

1. Standard carbon film resistors: ±5 % tolerance.
2. Metal film resistors: often ±1 % or better.
3. Precision metal film resistors: ±0.1 % for high-quality analog technology.

Typical use of leaded resistors:

Wired resistors are preferred when their special properties are important:

1. Power resistors:
z.e.g. in power supply units, motor controls, load simulations.

2. Series resistors for lamps or heaters:
Due to their high load capacity.

3. Safety-critical applications:
Often specified types with robust behavior under overload.

4. Prototyping and training:
Perfect for plug-in boards and experimental boards due to easy handling.

5. High voltage applications:
Wire-wound types with wider spacing and insulation.

6. Impulse/overvoltage protection:
Wirewound or specially coated resistors withstand voltage spikes better.

Advantages of leaded resistors:

• Mechanical stability: very well fixed due to soldering in holes.
• Higher power consumption: They can often dissipate more heat, typically from 0.25 W to over 10 W.
• Easy handling: Good for prototyping and repairs.
• High dielectric strength: Wire-wound types can withstand high voltages and pulses.
• Wide range of values and types: Many designs for different applications.

Disadvantages of leaded resistors:

• Larger and heavier: Need more space on the circuit board.
• More difficult to automate: slower and more expensive to assemble than SMD.
• More expensive for large series: Due to space requirements and assembly effort.

Leaded resistors are universal passive components that are available in many variants. Their basic function is to limit the current flow or to divide voltages in a targeted manner. They are used in power electronics, in power supply units, for measuring purposes, in high-voltage applications and wherever reliability and load capacity are important.

Below is an overview of the most important points that should be considered when purchasing leaded resistors:

When buying leaded resistors, it is particularly important to be aware of the very different applications, e.g. in simple consumer devices through to safety-critical industrial devices, and to take these into account when purchasing.

• The most important point is, of course, the correct value. You have to make sure that the resistor value corresponds to the circuit diagram.
• But equally important is the tolerance of the resistor:
• For simple current limiting, ±5 % can often be sufficient.
• For measuring and precision applications, ±1 % or ±0.1 % is required.
• Purchasing should therefore always clarify how tight the tolerance must be and whether the manufacturer guarantees it.
• Wired resistors are popular precisely because they can dissipate higher power than SMD types.
• The rated power, e.g. 0.25 W, 0.5 W, 1 W, 5 W, 10 W or more, must match the application.
• A safety margin is important to ensure that the parts are not constantly operated at their power limit.
• The ambient temperature and cooling on the circuit board or in the device also play a role.
• A professional purchase therefore takes into account the entire heat balance - not just the wattage on the data sheet.
• Wired resistors are available in many sizes and shapes - from small carbon film resistors to large wirewound resistors with heat sinks.
• Mechanical fit to the PCB is important: hole pattern, pin spacing, height.
• In the case of power resistors, there must be enough space for heat dissipation.
• There may be variants with threads, cooling flanges or other mounting options for special installations.
• When purchasing, it must be clear which type of resistor is required:
• Carbon layer: Are inexpensive, for simple applications.
• Metal layer: Precise and temperature-stable.
• Wire wound: For high power, often inductive, robust.
• Metal oxide: For high load capacity and pulse resistance.
• Safety resistors: These are especially suitable for fire protection or short-circuit protection.
• The technology influences the price, temperature behavior, pulse resistance and service life.
• The TCR describes how much the resistance value changes with temperature.
• This is not critical for many applications, but is very important for measurement and precision technology.
• Purchasers must clarify and specify the required TCR value.
• Every resistor has a maximum operating voltage. This must not be exceeded, especially in high-voltage applications such as measuring chains and power supply units.
• Wired resistors are often more voltage-resistant than SMD types, but here too the value must be checked.
• Purchasers should coordinate this with the development engineers and check the data sheets.
• Many applications, e.g. motor controls or protective circuits, require resistors that can withstand short high voltage peaks or pulse currents.
• Wire-wound or metal oxide types are often much more robust.
• Impulse resistance must be clearly specified to prevent damage or failure.
• There are mandatory specifications for certain markets and applications:
• Automotive: AEC-Q200 qualification.
• Medical technology or aviation: Special standards and approvals.
• UL/IEC safety certifications for safety resistors.
• RoHS and REACH conformity: environmental requirements.
• The purchasing department must ensure that the selected components meet these requirements and that the supplier can provide corresponding proof.
• Professional purchasers pay attention to:
• Reliable manufacturers with quality assurance.
• Supplier certifications such as ISO 9001 or industry-specific.
• Long-term availability (no short-term discontinuation).
• Reduction of the risk of counterfeit components (purchase via reputable distributors).
• Resistors can be supplied on belts, in bags, in magazines or as bulk goods.
• Tape is often required for machine assembly.
• For large power types, individual packaging or special packaging to protect against damage is often useful.
• Packaging units and minimum order quantities must be suitable for production.
• Wired resistors are often inexpensive per unit, but:
• High-quality, certified types cost more.
• The assembly work (THT instead of SMT) is more expensive.
• Rework, quality assurance and warehousing must be taken into account.
• The cheapest goods can cause expensive failures in production.
• Professional purchasers therefore pay attention not only to the price per 1000 units, but also to the total costs over the life cycle.
• Traceability and batch control are important for many industries:
• Every batch must be identifiable.
• In the event of problems or recalls, it must be possible to trace which production is affected.
• Large manufacturers and distributors offer batch tracking and test reports.
• Professional purchasing departments plan alternatives by listing equivalent types from several manufacturers:
• Listing equivalent types from multiple manufacturers.
• Compatible specifications (dimensions, performance, values).
• Enabling a change of supplier without redesign.
• This reduces dependence on one supplier and secures production.

When purchasing leaded resistors, you should pay attention to the appropriate resistance value, tolerance, power consumption and design so that they are electrically and mechanically suitable for the application. Quality, conformity to standards and reliable sources of supply are also important in order to avoid failures and production problems. Only through systematic testing and coordination with development and production can purchasing ensure that the components are used reliably, in compliance with standards and economically.

Leaded resistors can be purchased from various suppliers. Comprehensive information about manufacturers and suppliers of Leaded resistors from all over the world can be found on Exportpages.