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PCB connectors (also known as PCB board connectors or PCB electrical connectors) are designed to establish a secure and stable interface between a PCB and another PCB, cable, or external device. These tiny interfaces are the “joints” and “blood vessels” of electronic devices, responsible for transmitting signals, data and power.
This article is your ultimate guide, discussing the materials used to create PCB connectors, types and applications of connectors, how to choose a connector, design considerations, and common failure modes of connectors.
What is a PCB Connector?
A PCB connector is an electromechanical interface that enables current and data signals to pass between two circuit boards, or between a PCB and another device. Unlike soldering, it is not permanent and offers plug-and-play flexibility.
The primary functions of circuit board connectors are threefold:
- Electrical connection: Signals and power are reliably transmitted, ensuring no data loss and sufficient power.
- Mechanical connection: Physically secures components in place, resisting vibration and impact while avoiding inadvertent disengagement.
Types of PCB Connectors
Standard PCB connectors have contact pads or pins covered by an insulating case, depending on the configuration. Some have polarization keys, locks, and shielding. Also, each connector has its mating housing, and each housing has its crimps with knowledge of the wire’s AWG.
There are many types of connectors on the market, based on application, layout, electrical needs, or mechanical configurations.
The most commonly used classification method is classification by connection object, which includes:
Board-to-Board Connectors
These which also called PCB-to-PCB connectors are used to connect two boards directly without cables. They can be vertical, parallel (stacked), or coplanar, with height and spacing being key parameters.
Wire-to-Board Connectors
This connector joins wires or cable assemblies to a PCB. In general, it’s perfect for applications that do not change in connector impedance, to avoid reflections or any attenuation. They are primarily used for power connections, signaling, automotive, medical, and industrial control.
Wire-to-Wire Connectors
Wire harnesses can be extended or combined by connecting two wires. Although they are not directly connected to the PCB, they are closely related to the entire system.
Classified by interface characteristics:
Pin Headers and Socket Headers
Pin headers (male connectors) are soldered onto the PCB and paired with socket headers (female connectors), commonly used in development boards, module connections, and internal interfaces.
High-Speed Connectors
Such as PCIe and SATA interfaces, specifically designed for transmitting high-speed data streams. They place a strong emphasis on impedance matching and shielding to maintain signal integrity.
Coaxial Connectors (RF)
Coaxial connectors are generally used for radio-frequency (RF) systems, antennas, and communication devices. It offers signal quality and reduces noise, making it very suitable for high frequencies.
Edge Connectors
Edge connectors connect directly to the conductive traces on the edge of a printed circuit board. Edge connectors do not have pins; rather, the male portion is the edge of the PCB itself that slots into a receiving piece with spring-loaded contacts.
Edge connectors exist in computers where high interconnection exists, like RAM chips, expansion cards, PCI/PCIe connectors, or any device requiring a lot of connections in a small, stable array. Edge connectors are best when pin density is proper, long-term insertion is required, relative ease of assembly is helpful (no wires needed), and quick modularity/replacement/upgrade options are needed.
Structure and Materials of PCB Connectors
A reliable PCB connector depends on three key parts:
- Contacts (Pins): Usually made of copper alloys with surface plating such as gold or tin to ensure conductivity and prevent corrosion.
- Insulator (Housing): Typically made of high-performance plastics such as PBT, PA6T, or LCP, providing heat resistance and electrical insulation.
- Locking mechanism: Clips, latches, or screws are added to ensure mechanical stability and avoid accidental disconnection.
Conductor Materials Used for PCB Connectors Manufacturing
Copper | Brass | Phosphor Bronze | Beryllium Copper | Gold Plating | |
(Cu) | (Cu + Zn Alloy) | (Cu + Sn + P) | (BeCu) | Plated over Nickel | |
Conductivity | Very Good | Good | Good, Less than Brass | Very Good | Excellent |
Corrosion Resistance | Very Poor, high oxidation | Fair, better than copper, but still oxidizes and increases contact resistance | Good, better resistive properties than brass; not typically crack due to stress corrosion | Excellent, won’t oxidize or crack due to stress | Excellent, stable conductivity, low resistance |
Temperature Tolerance | Up to ~200 °C. | Up to ~200 °C. | Up to ~250 °C. | ~300 °C, higher than any other alloy of connectors | Up to ~200 °C. |
Applications | Used as a base metal for essentially all connectors. | Very common for connector pins, sockets, and mechanical housings where physical strength is a benefit. | Ideal for spring contacts, sockets, and high-cycle connectors. | high-performance connectors like military devices, or medical devices. | Any connector needing signals, e.g., USB, audio, RF, aerospace, and telecom. |
Notes | Must be plated (tin-nickel-gold) to comply with the rest of the reliability requirements in the field. | It has strength and cost advantages over phosphor bronze and beryllium copper (BeCu), | Excellent elasticity and fatigue resistance enable reliable contact when frequently mated. | Provides the best spring-like elasticity and incredible strength; this is the material of choice for precision contacts. BeCu is expensive because of beryllium. | Thin gold plating reduces costs slightly, yet overall high cost; it’s used where reliability and low noise due to low contact resistance are critical. |
How to Choose a PCB Connector
Selecting a suitable PCB connector is very important to ensure the expected electrical and mechanical performance. The following points must be considered during the selection process:
Current & Voltage Ratings
If you are using a power connector for your system, you must be sure about the maximum applied voltage that the plastic casing can insulate and the maximum allowable current that the connector pins can carry without failure.
Pin Count & Pitch
It matters depending on your layout; high-density designs require small pitch connectors to make placement and routing easier. On the other hand, if the cable is assembled manually, this will be challenging in small pitch wires because wires will also be smaller in diameter, making manual crimping very hard and not durable.
Mounting Style
Through-hole connectors are good for high-rated connectors. They are also prominent in high-vibration environments. Surface mounts are suitable for high-density designs.
Edge mount connectors are common in the case of using memories or control modules, as each is useful based on application requirements.
Signal Integrity
For applications requiring high-speed signaling, look for differential pair routing, impedance matching, and shielding. Using a standard connector like USB provides a guaranteed 90-ohm differential impedance.
Design and Assembly Considerations
To maximize connector reliability:
- Proper footprint considerations are important. If there’s no room for a connector, you’ll have an issue later when all the connector housings are positioned. For power connectors, for instance, make through holes and traces as short as possible and large for high current connectors.
- It’s recommended to keep traces short and wide to minimize resistance and dissipated power.
- Moreover, connectors that will be supplying analog signals should be located far away from the high-speed or noisy high-frequency connectors.
- In addition, if the connector is large in footprint, provide mechanical support features such as mounting holes to protect the PCB traces if the connector is broken.
- For reliability, through-hole connectors should include solder pads with thermal reliefs for better quality and reliability of solder joints.
- Lastly, pads for edge connector applications should be plated with a harder contact material, such as gold, to minimize wear over time due to repeated plugging.
Common Connector Failures & Solutions in PCB
Environmental factors, mechanical issues, or design flaws can be the major challenge of PCB connector failure. Understanding these common problems would allow us to prevent damage and maintain reliable performance.
Contact Corrosion or Oxidation
This challenge occurs due to the connectors exposed to the elements from outdoor applications, high humidity, and corrosive environments. Oxidation creates a layer, increasing contact resistance, which causes voltage drop and power waste.
- This is solved with corrosion-resistant platings like gold over nickel.
Improper Mating or Misalignment
When connectors are misaligned during fitting, resulting in bent or recessed pins, this causes improper mating. Always try to ensure that used housing is mating with a connector, not just pitched with, and the number of pins.
- You can solve this using the supplier mating products section while selecting.
Signal Integrity Degradation
High-speed or sensitive signal paths may suffer from impedance mismatches, excessive insertion loss, or crosstalk due to poor PCB connector footprint design.
- Proper differential pair routing, impedance-controlled pad geometries, and periodic inspection or replacement of high-frequency connectors are recommended.
Lack of Polarization or Keying
Without mechanical polarization, connectors can be inserted incorrectly. If connectors are misaligned, reverse polarity can occur, shorting the system and potentially damaging all components.
- Order connectors with non-symmetrical housings, polarized slots, or shrouded headers to prevent this type of mismatching.
Conclusion
Much more than simple plugs, PCB connectors are precision components that combine electrical, mechanical and materials science. When selecting a circuit board connector, engineers should carefully evaluate electrical, mechanical, and environmental requirements to ensure long-term performance.
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FAQ
A1: Plating a contact with gold or nickel reduces wear, increases resistance to oxidation, and results in low contact resistance for multiple connect/disconnect cycles. The harder the plating and mill thickness, the more longevity the edge connector will have.
A2: It can be possible if the variations have the same pin pitch, mounting hole placement, and mechanical keying.
A3:
- Identify the Damage: Check if it’s a broken pin, cracked housing, or loose connection.
- Gather Tools: You’ll need a soldering iron, replacement connector, multimeter, and epoxy/glue (for cracks).
- Power Off: Ensure the device is disconnected.
- Remove Old Connector: Desolder the broken connector and clean the PCB.
- Fix Minor Damage: Straighten bent pins or replace broken ones.
- Solder New Connector: Align and solder the new connector to the PCB.
- Test: Check with a multimeter for continuity and secure connection.
- Reassemble: Once tested, reassemble and power up.
A4: PCB connector lifespan depends on cycles, environment, and quality. Good ones last thousands of insertions, but heat, corrosion, or wear can shorten their life. Choosing the right type ensures longer reliability.
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