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PCB Connectors: A Comprehensive Guide to Types, Selection, and Applications

In the complex realm of electronic components and modules, the ideal integration of various components and modules is of the utmost significance. Ensuring these are PCB connectors. They are components that are hardly noticed but are actually needed in the transmission of signals, power supply, and data from one circuit board to another. This comprehensive guideline by FS Technology will provide you with in-depth information regarding the different aspects of PCB connectors.
 
Although FS Technology is a leading PCBA service provider, our years of turnkey project experience have given us deep component expertise, including dedicated procurement services. If you need support, contact us.

What is a PCB Connector?

A PCB connector, also known as a header connector, socket connector, and terminal block connector, can be described as a basic electromechanical device used to provide a reversible connection point on a PCB. The basic job of this connector is to provide an electrical connection without needing to solder each wire and component permanently.
 
The main functions of a PCB connector are:
  • Modularity: They facilitate easy assembling and disassembling of the system and its components (such as the integrated circuits, sensor module and power supply).
  • Serviceability: Defective modules can be readily disconnected and replaced.
  • Signal Integrity: A properly designed connector will assure reliable and low-loss transmission of the electrical signals from point A to point B.
  • Power Distribution: They form a secure and durable power delivery path from one part of the system to another.
  • Design Flexibility: Connectors allow complex designs to be subdivided so that smaller PCBs can be combined in three-dimensional space.
 
A standard connector has two basic components. The first component is the housing made of an insulating material (such as nylon, PBT, and LCP). The second component comprises the contacts made of a conductive material (phosphor bronze plated with gold or tin). The housing provides electrical isolation between the contacts. The contacts are designed to offer a secure and gastight connection when mated together.

Detailed Types of PCB Connectors

PCB connectors can be classified in various ways. A list of their classifications according to the type of termination method and the type of connection object follows:

By Termination Method (How Wires are Attached)

Screw-in PCB Connector

screw-in PCB connector
Screw type connectors, also known as screw terminals and terminal caps, form a popular and widely used group of wire connectors. Ranging from wire size to wire thickness, various standards of the connectors are P1, P2, P3, P4, P5, and P6. Made of a sturdy combination of insulators and metal conductors along with screws, the terminals provide a reliable method of wire mounting. They are widely used due to versatility and the ability to support various wire gauge sizes. They can be mounted at power points and used in control panels. They also support easy replacement due to their simple mounting procedure.
 
The choice of a screw type PCB connector involves careful consideration of the crucial factors mentioned above. The operational procedure of the PCB connector can be concisely described as follows:
 
  1. Carefully pass the wire through the lower aperture of the connector so that the end of the wire makes strong contact with the underlying metal conductor.
  2. In case there’s a need to connect another wire, do so and guide it through the predetermined slot in the connector.
  3. To secure the wire precisely, one should tighten the swivel cap mounted on the connector deftly so that the screw inside the cap creates a strong and unyielding hold on the metal wire conductor.

Spring PCB Connector

Spring PCB Connector
Also known as push-in terminals and spring-clamp terminals. The spring-loaded terminals diverge considerably from the rotary terminals used in rotary connectors in the sense that spring-loaded terminals utilize the mechanical force of the spring to secure the connection. This type of terminal encompasses a wide array of models that include board-to-board terminals, target connections, and terminal blocks.
 
The installation process takes only a short time and doesn’t require any tools. They are ideal when mounted at high volumes because the wiring of the connector takes less time. They are also known to be resistant to vibration. The procedure involved can be described in the following brief summary:
 
  1. Start by identifying the possible markings found in the connectors represented by “+” and “-” signs, ensuring correct positioning of the positive and negative terminals.
  2. Use the screwdriver to push the spring-loaded tab down carefully. This will provide a receptive opening to insert the wire. As the tab is opened, the natural spring effect holds the wire in its position firmly.
  3. If the connector has screw holes or mounting points, it should be secured using screws or a screwdriver.

Plug-in PCB Connector

Plug-in PCB Connector
Plug-in connectors allow the establishment of connections through the simple plug-and-unplug procedure. They also often comprise pin and socket arrangements. Some of the typical plug & play type of connector arrangements include the pin header (male connector parts) and the socket header (female connector parts). This list also encompasses the USB connector, the HDMI connector, as well as the D-Sub connector. The physically connectible type of plug-in connector can be readily purchased. The wires will be attached to the male connector part of the plug-in connectors. This will in turn allow the effortless connection and disconnection of wires through the engagement of the male connector part to the corresponding female connector part of the terminal blocks. The plug-in connector has utmost significance when used in applications involving constant disconnections and connections of the components.

IDC Connector

An “Insulation Displacement Connector” can be regarded as a specialized type of connector that falls under the category of PCB Connectors. This type of connector allows direct insertion of the connector itself through the concept of “insulation displacement” without the requirement of removing the insulation of the wire. This novel method of interconnection has been known to greatly improve the efficiency of interconnections along with the speed of interconnections, especially when the task involves numerous wire interconnections of the type found in autonomous vehicles.
 
Usage Instructions: The IDC Connectors provide the facility to connect a wire to the sharp-forked connector that slices the wire’s insulation. The connector allows quick connection of the wires of the ribbon cable simultaneously without pre-stripping the wires.

By Connection Object (What is Being Connected)

Board-to-Board Connector

Board-to-Board PCB Connectors
As its name suggests, the board-to-board connector plays a crucial role in bridging two or more electronic circuit boards side by side or at an angle. Essentially, this type of connector bypasses the constraints of the spatial limitations caused by cable connections. In fact, cable connections can be perceived as restrictive when considering high-density packaging. This type of connector allows the development of a complex system involving numerous circuit boards in a single device.
 
Common setups are:
  • Mezzanine Connectors: used to interconnect two parallel PCBs.
  • Motherboard-Daughterboard Connectors: A vertical header on one board connects to a socket on another (for example, the Raspberry Pi HATs).
  • Stacking Connectors: Comparable to mezzanine, but might be of a particular height to create spacing between the boards.
  • Backplane Connectors: A high-pin-count connector system whereby several daughter cards can be connected to a single “backplane” motherboard.
 
Board-to-board PCB connectors also work efficiently in the following applications:
  • Multi-Board Systems: Using multiple boards in complex layouts, board-to-board connectors provide efficient data and signal transfer from one board to another.
  • Modular Design: Modular designs optimize the production procedure through the development of specialized modules that can be manufactured and tested separately before being linked together using board-to-board connectors.
  • Signal Expansion: A practical example can be observed in high-performance graphics cards that require the connection of their output signals to the motherboard to support expansive display screens.

Wire-to-Board Connector

Wire-to-Board PCB Connector
Wire-to-Board Connectors form the vital link for the interconnection of discrete wires and a cable harness to the PCB. They form the basic point of entry of power and signals from the outer environment to the electronic system. The requirement of the wire-to-wire connector has been incorporated at the wire connection end of the wire-to-board connector. The board connection end utilizes the concept of press-fit connectors or two-piece soldering connectors. In applications requiring additional security levels, wire-to-board connectors containing locking levers and latches shall be used.
 
The internal wire-termination technique used in the above-mentioned connector can be adjusted according to the wire type and the number of point contacts. The connector used in the higher power end makes use of compression contact points to provide a tight and secure wire-to-contact point interface without the production of excessive heat. When it comes to large terminals involving the accommodation of at least 20 wires, the possibility of customized automated soldering can be explored.
 
Just as the footprint of many electronic interconnects has diminished in size, the wire-to-board connector has also been affected in the same manner. This trend has paved the way for the widespread adoption of ultra-compact wire-to-board connectors that feature a footprint of less than 1.5 millimeters. These connectors seamlessly align with SMT assembly processes, particularly in mass production settings. Integration of the gold-plated contact and stress-relief functionality has served to add strength to the miniature connector’s performance.

I/O Connector

The I/O Connectors are a specialized type of connector that serves as the interface of the device from the outside world. They can be described in terms of their protocol or functionality – there’s USB which serves as the data connector, HDMI used as the video connector, and RJ45 used as the Ethernet connector. Though technically wire-to-board connectors, they do come in a standardized form to allow interconnectivity of devices.

PCB Connector Mounting Techniques & Process

Depending on the requirements of the context, PCBA manufacturers use various methods of interconnections like SMT, THT, and pin connections.
 

Through-Hole Technology (THT) Connectors

The mounting of THT connectors involves inserting their long leads through the holes drilled in the PCB and soldering them on the other side. This provides a remarkably strong mechanical joint and makes them suitable for applications that are subjected to physical stress (such as power connectors and certain types of header applications). The procedure is less suited to automated high-density assemblies.
  1. Component Placement: The connector pins are to be placed inside the plated-through holes of the PCB.
  2. Soldering: The board moves across the wave soldering apparatus, which coats the pins of the bottom side of the board with solder.
  3. Cleaning & Inspection: Cleaning of the flux residue takes place together with the inspection of the soldered joints.
 

Surface Mount Technology (SMT) Connectors

SMT Connectors are directly soldered to the surface of the PCB, preferably using the reflow oven method. SMT Connectors represent the standard of today’s electronic manufacturing because they enable the production of smaller PCBs at higher speeds. SMT Connectors provide excellent electrical performance but are less durable than through-hole connectors from a mechanical point of view because they can be affected by mechanical stresses.
  1. Solder Paste Printing: Stenciling the solder paste onto the solder pads of the PCB.
  2. Component placement: The Pick & Place Machine accurately positions the SMT connector onto the paste.
  3. Reflow Soldering: The board passes through a reflow oven where the solder paste melts to form a permanent connection.
  4. Inspection: Automated Optical Inspection (AOI). This involves the inspection of placement accuracy and solder quality.
 

Press-Fit Connectors

These types of connectors are mounted through the plated through holes of the PCB. The pins will slightly deform when they are mounted through the holes to create a cold weld that will be gas-tight without the need to solder the connector. This method of connector mounting has been widely used due to its efficiency and effectiveness in the case of high-pin-count backplane connectors.
  1. Alignment: The press-fit connector is aligned to the target plated-through holes of the PCB.
  2. Pressing: A specific force is applied (manually using a press tool or through an automated press) to push the connector home until it’s seated.
  3. Verification: The connection can be verified through the measurement of the insertion depth and the retention force.

How to Select PCB Board Connectors?

As an engineer, the proper selection of the PCB connector plays a crucial role. The information presented below will outline the important factors of selection, along with helpful tips so you can select the right one.

Electrical Requirements

  • Current Rating: The most important spec. Make sure the connector can support the highest current without overheating. The margin of safety should be at least 1.5 times.
  • Voltage Rating: Needs to be above the system’s maximum operating voltage.
  • Contact Resistance: Lower numbers (e.g., <20mΩ) are desirable to reduce power losses due to voltage drop.
  • Insulation Resistance: It should be high (>100 MΩ). This is to resist the passage of signals.

Mechanical Requirements

  • Pin Count/Pitch: Decide the number of signals and then choose the connector that has enough pins. The pitch (distance from each pin – examples of which are “2.54mm,” “1.27mm,” and “0.5mm”) will depend upon the PCB layout density.
  • Mating cycles: The number of connected/disconnected cycles the connector can withstand. The consumer product may require 100s of cycles, while the test equipment may require 1000s.
  • Insertion/Extraction Force: The level of force needed to connect or disconnect the connector. This can impact ease of access and the requirement for locking mechanisms.
  • Locking System: In the case of vibration and shock loading, the necessity of the connector’s locks, latches, and screws cannot be underestimated.

Environmental Conditions

  • Operating Temperature: Automotive: -40°C to +125°C; Industrial: -25°C to +85°C; Consumer: 0°C to +70°C.
  • Ingress Protection (IP Rating): In case of an outdoor environment, the chosen connector must be of a suitable Ingress Protection rating (such as the IP67 rating).
  • Chemical/Radiation Resistance: A desirable requirement when considering medical or aeronautical usage.

Materials and Manufacturing

  • Contacts: Phosphor bronze is common. Gold plating has superior anti-corrosion properties and low contact resistance. Tin is less expensive than gold.
  • Housing: PA66 nylon has general-purpose applications. PBT has better resistance to high temperatures. LCP has superior performance in high-temperature reflow soldering.
  • Process Compatibility: Make sure the connector’s thermal profile matches the soldering process you employ (SMT reflow soldering or THT wave soldering).

Manufacturing Materials for PCB Connectors

The next section will give information regarding the materials used to manufacture the connectors:
 
  • Thermoset EP: This type of plastic has high physical stability and flame resistance, though perhaps a lack of toughness.
  • Thermoplastic polycarbonate PC: Known for its geometric stability, integral strength, and marked resistance to heat, it also provides improved insulating capability. However, it should be remembered that fractures or cracks appear when exposed to excessive stress.
  • Thermoplastic polyester PBT: Mainly used in high-temperature applications. Provides high levels of flame retardancy when used together with FR-4 PCBs.
  • PA-F: This type of glass fiber-reinforced nylon has low water absorption and provides high rigidity. This material has particular applications in high-voltage protection.

How to Ensure the Reliability of PCB Connectors?

In order to PCB connectors are integral to the formation and dissolution of wire connections in a circuit. As a result of their convenience and ease of use, they see many applications in control panels, circuit grounds, motor connection points, and many others. Apart from their convenient usage, terminal blocks also increase the safety level of the electrical circuiting system in their own right. This has been achieved through the principles of isolation, grounding, and protection of the rest of the electrical circuiting system. The terminals also provide a secure method of connection of live terminals and can be used as test points to check the voltage or other electrical characteristics of a circuit in a secure manner. This has many benefits because it increases the safety of the electrical circuiting system when diagnosing problems.
 
  • Contact Integrity: The first point of failure will often be the contacting point itself. Oxidation, contaminants, or wear of the plated layers can contribute to increased resistance. The right type of plating materiel and the proper “wipping” action are critical.
  • Mechanical durability: The housing has to be able to withstand insertion forces, shock, and vibration. Simulation of stresses and durability tests are essential.
  • Thermal Performance: The connector must be able to withstand the self-heating caused due to the flow of current and the existing ambient temperature. The CTI materials are used to eliminate electrical tracking.
  • Testing and Certification: Ensure you are considering only those connectors which are industry-standard compliant (UL and/or IEC) and tested regarding the number of mating cycles, current cycling, and environmental stress.

Conclusion

Although at times small in size, PCB connectors can be considered giants when it comes to their role in the functionality, dependability, and modularity of modern electronic circuits. Ranging from the rugged screw terminals of the control panel used in industry to the compact spring-loaded connectors of consumer electronic equipment, the proper usage of the connector makes the difference.
 
FS Technology can utilize our many years of turnkey PCBA solution experience in assembling not only your PCBA but also in identifying the right components to be used – even the connector parts. As you know, the strength of a chain is no stronger than its weakest link. A faulty link can bring down the whole chain. That’s the reason why you will be able to traverse this complex landscape without a hitch when you work with an experienced company.
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FAQs about PCB Connnectors

It is strongly discouraged. While connectors may appear physically similar and have the same pin count and spacing, subtle differences in tolerances, plating materials, and contact design can lead to poor mating, increased resistance, intermittent connections, or even physical damage. Always use mated pairs from the same manufacturer and product series.

  • Material Selection: Specify gold-plated contacts for high-reliability applications as gold is highly resistant to oxidation.

  • Storage: Keep connectors in their original sealed, anti-static bags until use. Store them in a climate-controlled, low-humidity environment.

  • Handling: Avoid touching the contacts with bare hands, as oils and moisture can accelerate corrosion.

  • Design: For tin-plated connectors, use a design that provides sufficient normal force to break through the thin oxide layer that can form (a process known as “wiping”).

Not necessarily. A higher mating cycle rating (e.g., 10,000 cycles vs. 50 cycles) indicates a more durable connector designed for frequent connection and disconnection. This comes at a higher cost. For a device that is assembled once and never disconnected (like a smart home appliance), a standard-cycle connector is more cost-effective. Reserve high-cycle connectors for applications like test ports, USB interfaces, or modular components that will be regularly swapped.

This is typically caused by the connector’s material not being suitable for the high temperatures of reflow or wave soldering. Standard plastics like Nylon (PA6T) have lower melting points. For SMT processes, ensure you select connectors with high-temperature thermoplastic housings, such as Liquid Crystal Polymer (LCP) or Polybutylene Terephthalate (PBT). Always consult the manufacturer’s datasheet for the connector’s maximum soldering temperature profile.

IP (Ingress Protection) rating defines a connector’s protection against solid objects (first number) and liquids (second number). For instance, a connector rated IP67 is dust-tight (6) and can withstand temporary immersion in water (7). This is essential for outdoor, automotive, or industrial equipment exposed to dust, moisture, or cleaning processes.

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