A zero ohm resistor, also called a zero ohm jumper or link, is a resistor with a designed resistance of, or very close to, zero ohms. Despite having negligible resistance, these devices serve important functions in circuit boards. This article covers the characteristics, symbol, typical applications, PCB layout considerations, and substitutes for zero ohm resistors.
Zero Ohm Resistor Characteristics
A zero ohm resistor looks identical to a standard through-hole or SMD resistor. However, it is constructed to provide the lowest possible resistance, ideally 0 ohms. Key characteristics include:
- Resistance range from 0.0Ω to 0.1Ω typically
- Rated for various power levels per size
- Through-hole, SMD and chip package types
- Act as short circuits or jumpers when soldered
- Provides connection without copper trace
- Lets PCB layout be adjusted post-production
Zero ohm resistors are extremely useful for flexibly bridging connections during prototyping, reworking boards, or adjusting circuit layouts as needed.
Zero Ohm Resistor Symbol
Zero ohm resistors are represented on circuit schematics using a standard resistor symbol with the resistance value labeled as 0Ω:
This indicates any location a zero ohm resistor is used to short two points together in the actual circuit.
On PCB layouts, zero ohm resistors are denoted using unique layer silkscreen identifiers defined in the legend. Common identifiers include:
- Component overlay: 0Ω
- Top silkscreen: JMP
- Bottom silkscreen: BRIDGE
This allows PCB assembly operators to clearly identify which components act as intentional shorts.
Why Use Zero Ohm Resistors?
Zero ohm resistors provide several advantages versus just connecting points with traces:
Adjust Layout Post-Fabrication
- Can solder or omit zero ohm resistors to alter connections
- Facilitates field upgrades, prototyping, and reworking boards
- Avoids crossing complex traces on dense boards
- Jumps between layers can be made post-production
- Fine pitch ICs have space for resistors but not traces
- Simplifies via placement
Maintain Part Count
- Act as resettable fuses when sized properly
- Can act as temperature sensitive resistors
Zero ohm resistors empower more flexible PCB layouts and post-production adjustments.
Common Applications of Zero Ohm Resistors
Typical use cases for zero ohm resistors include:
- Shorting points like unused IC pins
- Providing test points to isolate sections
- Paralleling supply rails
- Enabling/disabling options post-production
- Converting oscillator types
- Selecting different gain settings
- Avoiding dense routing blockages
- Jumping between layers as needed
- Connecting ground planes
- Anchor points for wires or connectors
- Securing points needing strain relief
- Spacing heavy components
Zero ohm resistors empower designers to optimize PCB layouts while retaining flexibility.
PCB Layout Considerations for Zero Ohm Resistors
To leverage zero ohm resistors most effectively, keep these PCB design guidelines in mind:
- Clarify purpose using silkscreen identifiers like 0Ω or JMP
- Place at locations requiring post-production shorts
- Substitute for jumpers to keep BOM clean
- Use to simplify routing without crossing traces
- Avoid shorts from solder, especially on dense boards
- Include some extras for rework flexibility
- Follow datasheet guidelines for power ratings
- Review if any can be replaced by direct traces
Carefully planning locations for zero ohm resistors during layout facilitates optimizing the design iteratively even after fabrication.
SMT Zero Ohm Resistor Types
Several different SMT zero ohm resistor package styles exist:
- Length 3.2mm x Width 1.6mm
- Rectangular, double terminals
- Rated up to 1W
- Length 1mm x Width 0.5mm
- Tiny surface mount device (SMD)
- Rated roughly 0.1W
- Length 1.6mm x Width 0.8mm
- Very small SMD package
- Rated around 0.25W
- Length 2mm x Width 1.25mm
- Popular mid-size SMD
- Rated up to 0.5W
- Length 3.2mm x Width 1.6mm
- Larger SMD, similar to 2512
- Rated up to 0.5W
Larger or higher power ratings are physically more robust. But smaller SMD footprints save valuable space.
Through-Hole Zero Ohm Resistor Types
Common through-hole zero ohm resistor packages include:
- Cylindrical body with wire leads
- Often 5% tolerance flameproof types
- Rated up to 3W typically
- Discoidal ceramic body with bent leads
- Available up to 5W power rating
- Commonly with 5% tolerance
- Cylindrical coated metal film structure
- Very low resistance material (<10mΩ)
- Lower power, around 0.5W
- Wirewound or metal strip construction
- Designed to burn out if overloaded
- Used like resettable fuses up to 35W
Through-hole zero ohm resistors support higher current connections.
Alternatives to Zero Ohm Resistors
In some situations, alternatives to zero ohm resistors may be preferable:
- Simplest direct board shorts
- Limit adjustments post-production
- Lowest resistance via thick copper
- Easily modified or replaced
- Allows off-board connections
- No PCB space required
- Facilitates voltage probing
- Isolates sections of circuit
- Extra components not needed
- Direct solder shorts for quick mods
- Can reconnect blown fuses
- Risks accidental connections
- Accepts replaceable fuses
- Resets protection after failure
- More robust than zero ohm links
Each approach has trade-offs to evaluate for the particular application.
Summary of Zero Ohm Resistor Characteristics
To summarize, the key characteristics of zero ohm resistors:
- They are standard resistors made with very low (<0.1Ω) resistance.
- On schematics they are shown as standard resistors labeled with 0Ω value.
- They act as short circuit connections when soldered on PCBs.
- They enable flexible post-production adjustments of connections.
- SMD and through-hole packages support sizes up to several watts.
- Alternatives like traces or wire jumpers have advantages in some applications.
Zero ohm resistors empower modification, rework and simplified routing of PCB layouts. Understanding their applications helps designers optimize prototyping and production.
Frequently Asked Questions
What are some good rules of thumb for using zero ohm resistors versus traces or jumpers on a PCB?
General guidelines on when to use zero ohm resistors versus alternatives:
- Use traces for simple point-to-point shorts and ground connections
- Use jumpers for temporary prototypes or off-board connections
- Use zero ohms when post-fab adjustments may be needed
- Use zero ohms when complex trace routing is difficult
- Use zero ohms to keep BOM cleaner over jumpers
- Use traces when shorts are unlikely to require changes
Evaluate trade-offs on a case-by-case basis for each connection.
What power rating should you choose for a zero ohm resistor?
Select a zero ohm resistor power rating according to:
- Expected continuous current through the connection
- Peak pulsed or inrush current if applicable
- Desired safety margin or headroom
- Physical space available on PCB
- Thermal environment and airflow
A good practice is choosing a rating 2-3x the expected current to provide robustness.
What are common causes of failure for zero ohm resistors?
Zero ohm resistors most often fail due to:
- Overcurrent exceeding power rating
- Accumulated pulse heating degrading connections
- Thermal stresses fracturing solder joints
- Mechanical stresses from vibration/shock
- Nearby short circuits passing excessive current
- Faults in connected circuitry
Proper sizing, layout and assembly mitigate these failure modes for reliable operation.
12 Functions of Zero Ohm (Ω) Resistance
We often see 0 ohm resistors in the circuit. For newcomers, it is often confusing: since it is a 0 ohm resistor, it is a wire. Why should it be installed? Is there such a resistor sold in the market? In fact, the resistance of 0 ohms is quite useful.
Zero ohm resistor, also known as jumper resistor, is a special purpose resistor. The 0 ohm resistor is not really zero resistance (that is the superconductor dry thing), just because of the resistance, it is also a regular paste. The chip resistor has the same error accuracy as this indicator.
The following summarizes a series of usages of zero ohm resistors:
1. There is no function in the circuit, just for the convenience of debugging or compatible design on the PCB.
2. Can be used for jumpers, if a certain line is not used, you can directly not attach the resistor (does not affect the appearance)
3. When the matching circuit parameters are uncertain, replace it with 0 ohms. When the actual debugging is performed, determine the parameters and replace them with specific numerical components.
4. When you want to measure the current consumption of a certain part of the circuit, you can remove the 0ohm resistor and connect the ammeter to facilitate the current consumption.
5. In the wiring, if the actual cloth can not pass, you can also add a 0 ohm resistor
6. Act as an inductor or capacitor under high frequency signals. (related to external circuit characteristics) Inductive use, mainly to solve EMC problems. Such as ground and ground, power and IC Pin.
7. Single point grounding (refers to protective grounding, working grounding, and DC grounding are separated from each other on the equipment, and each becomes an independent system.)
8. Fuse action.
9. Ground and digital ground single point grounding.
As long as it is ground, it will eventually be received together and then into the earth. If they are not connected together, they are “floating”, there is a pressure difference, and it is easy to accumulate electric charges and cause static electricity. The ground is referenced to 0 potential, all voltages are derived from reference ground, the ground standards are the same, so the various grounds should be shorted together.
It is believed that the earth can absorb all the electric charges and always maintain stability, which is the ultimate ground reference point. Although some boards are not connected to the earth, the power plant is connected to the earth, and the power supply on the board will eventually return to the power plant. If the analog ground and the digital ground are directly connected to each other, it will cause mutual interference. It is not short-circuited and not appropriate. There are four ways to solve this problem as above:
(1) Connected by magnetic beads;
(2) Connected by a capacitor;
(3) Connected by an inductor;
(4) Connect with a 0 ohm resistor.
The equivalent circuit of the magnetic bead is equivalent to the band-stopper, which only significantly suppresses the noise of a certain frequency point. When using it, it is necessary to estimate the noise frequency in advance so that the appropriate model can be selected. For cases where the frequency is uncertain or unpredictable, the beads do not fit.
The capacitor is connected straight to the ground, causing floating.
The inductor is bulky, has many stray parameters, and is unstable.
The 0 ohm resistor is equivalent to a very narrow current path, which effectively limits the loop current and suppresses noise. The resistor has an attenuation in all frequency bands (0 ohm resistor also has impedance), which is stronger than the magnetic beads.
The following two figures are a circuit, just because the electronic components are not labeled the same. R7 (R33) is a single-point link end for analog ground and digital ground.
10. For current circuit when bridging
When the ground plane is divided, the shortest return path of the signal is broken. At this time, the signal loop has to be detoured to form a large loop area, and the influence of the electric field and the magnetic field becomes stronger, which is easy to interfere/interfere. By connecting a 0 ohm resistor across the partition, a shorter return path can be provided to reduce interference.
11. Configuration circuit
Generally, there should be no jumpers or dip switches on the product. Sometimes the user will tamper with the settings, which may cause misunderstanding. In order to reduce the maintenance cost, the 0 ohm resistor is used instead of the jumper to solder on the board.
12. Other uses
Overlay when wiring;
Temporarily replace other patch devices;
As a temperature compensation device;
More often than not, it is due to EMC countermeasures. In addition, the 0 ohm resistor is less than the parasitic inductance of the via, and the via also affects the ground plane (because the hole is to be dug).
There is also a different size 0 ohm resistor to allow different currents, generally 0603 1A, 0805 2A, so different currents will choose different sizes, there are reserved positions for magnetic beads, inductors, etc., according to magnetic beads, inductors The size is also packaged, so 0603, 0805 and other different sizes are available.