Electronic Connectors

Chapter 1: What are Electronic Connectors?

Electronic connectors are crucial devices that link electronic circuits, playing a key role in assembling, installing, and powering electrical devices. They are integral to various electronic equipment, including industrial machinery, consumer electronics, communication systems, and home and commercial appliances. Although often overlooked, connectors are essential for the functionality and completeness of electronic products. While many connectors are designed to be temporary or removable, some serve as permanent electrical connections.

The two main components of an electrical connector are its contacts and housing, also referred to as its plug or receptacle. The housing holds the terminals and ensures the stability of their connections. It isolates the terminals from other electronic components and prevents short-circuiting. Plugs and receptacles protect the terminals from the elements and weather and are made from insulating materials such as molded plastics or ceramics.

Additional components may be integrated into a connector based on its intended use. Keyed connectors ensure proper insertion by allowing only a specific orientation. Locks can be added to connectors to prevent accidental disconnection, while sealed connectors are designed for use in underwater applications.

Connector terminals are the pins that provide a continuous path for the electrical current to flow between circuits. They are made from electrically conductive materials such as brass, phosphor bronze, beryllium copper, and high copper alloy.

Chapter 2: Terminologies Used in Electronic Connectors

The terms used to describe the properties and specifications of electronic connectors include:

Electronic Connector Terminology

Electronic Connector Gender

Electronic connectors typically come in pairs, with each half having a gender designation. The male part is referred to as the plug, while the female part is known as the jack or socket. The jack features recessed holes (socket holes) that house the terminals and connect to a wire, cable, or device. The terminals of the plug are inserted into these slots in the jack to establish the connection.

Keying

Most connectors can only be inserted in one orientation due to the polarity of electric charges. Keying is a design feature that prevents incorrect mating orientations. A keyway helps avoid mechanical and electrical damage by ensuring that the connector is not inserted at the wrong angle or into an incompatible socket. It also addresses issues with symmetrical connectors by guiding correct insertion.

Locking Mechanisms

A locking mechanism secures the connector during mating, preventing displacement from bumps or jolts. It ensures the connector remains coupled during operation, reducing the risk of damage to the electronic device. Various types of locking mechanisms are used in electronic connectors, including push-pull, bayonet couplings, and fine thread screw couplings.

Number of Contacts

The number of contacts indicates the count of conductive elements that establish an electrical connection.

Contact Pitch

Contact pitch, or simply pitch, denotes the center-to-center spacing between adjacent pins, typically measured in millimeters. In arrays, the pitch can vary between rows and columns. This measurement plays a critical role in determining connector compatibility.

A larger pitch results in fewer terminals within a given connector area, reducing the likelihood of electrical arcing. Electrical arcing occurs when current leaps between closely spaced pins, particularly if they are too near each other.

Pin Numbering

Each pin on an electrical connector is serialized with a unique number according to a sequence specified by standards. For integrated circuits, pin numbering typically follows an anti-clockwise direction.

Pin Sequence

Some electronic connectors are designed with a specific pin sequence, requiring a particular set of pins to be connected before others can be inserted. This ensures proper alignment and functionality.

Mating Cycles

Mating cycles indicate the number of times an electronic connector can be reliably connected and disconnected while maintaining its performance specifications. For instance, a USB connector may endure thousands of mating cycles, whereas FFC and FPC connectors typically support fewer cycles. Factors influencing mating cycles include the type of connector material, plating, thickness, resistance thresholds, and mating style.

Mount

Mounting refers to how an electronic connector is attached to an electrical device. Mounting types include board mount (such as through-hole mount, surface mount, and edge mount), panel mount, and cable mount.

Termination

Termination describes the method used to connect the terminals of an electronic connector. Various termination methods will be explored in subsequent chapters.

Strain Relief

Strain relief is a feature or component that alleviates forces acting on an electronic connector, preventing stress and damage, and ensuring mechanical stability.

Performance Parameters

Performance parameters define the operational conditions for which an electronic connector is designed to function reliably. These parameters encompass the current rating, voltage rating, and temperature ratings, including both minimum and maximum operating temperatures.

Features of Electronic Connectors

Certain electronic connectors are equipped with features tailored for specific applications. Examples of such specialized connectors include:

• Hermetically Sealed Connectors use highly engineered glass-to-metal sealing to create an airtight sealing. They are air and moisture resistant and can withstand extreme environments. They can operate safely when fully submerged in water and endure pressures up to a certain depth.
• Water-Resistant Connectors protect electronic connections from damage caused by exposure to water. Unlike hermetically sealed connectors, however, they are not designed to operate underwater.
• Moisture and Oil Resistant Connectors protect the electronic connections from damage caused by exposure to moisture and oil.
• EMI and/or RFI Filtering on connectors provides protection to electronic connectors from electromagnetic interference (EMI) and/or radio frequency interference (RFI).
• ESD Shielded Connectors protect the electronic connections from electrostatic discharge (ESD) damage.

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Chapter 3: What are the different types of electronic connectors?

Electronic connectors are classified according to their level of interconnection:

• Integrated circuit (IC) chip level
• IC-to-package level
• IC package-to-board level
• Board-to-board level
• Wire-to-board or subassembly-to-subassembly level
• Box-to-box level or connection between systems

Electronic Connector Types

Electronic connectors encompass a variety of types, including but not limited to the following:

Board-to-Board Connectors

Board-to-board connectors serve the purpose of linking two printed circuit boards (PCBs) directly, eliminating the need for cables. These connectors typically include both a male and a female part, and they can be mounted onto PCBs using either through-hole or surface mount techniques. The connection between PCBs can be made either perpendicular or parallel. For stacking configurations, a mezzanine connector is used, whereas an edge connector is designed to align with the edges of single-sided or double-sided PCBs.

Box Header Connectors

Board-to-board connectors can be classified based on their header style. In the case of box headers, the terminals are enclosed within the header. On the other hand, pin headers feature terminals that are visible and not enclosed.

Backplane Connectors

A backplane functions as a central framework that interconnects multiple PCBs, aligning the pins of one board with corresponding pins on others. This type of connector is commonly employed in computers and telecommunications equipment to facilitate data exchange between various components.

Power Connectors

Power connectors are connectors that allow electrical current to pass through them to provide power to a device. They carry either a direct current (DC) or an alternating current (AC). The common types of power connectors are the following:

Barrel Connectors

Barrel connectors, often referred to as coaxial power connectors, are used to link electronic devices to external power sources. They transfer low voltage DC power from a wall adapter to the device. These connectors are prevalent in consumer electronics and come in various standard sizes and lengths.

The barrel plug is composed of concentric metal cylinders separated by an insulating layer. The inner cylinder is designed to fit the pin of the barrel jack. The barrel jack can be mounted on a PCB, panel, or cable. Inside the jack, a cantilevered spring presses against the outer sleeve of the plug, ensuring that the inner sleeve makes contact with the pin.

Molex Connectors

Invented and patented by the Molex Connector Company in the late 1950s, Molex connectors are widely used for powering computer drives and other devices. These connectors feature cylindrical spring-metal pins that connect with matching cylindrical spring-metal sockets. A typical Molex connector can have between 2 and 24 contacts, arranged in either single or double rows, with keyed configurations to ensure correct alignment during connection. Both the pins and sockets are secured within a plastic housing.

IEC Connectors

IEC connector is a category of connectors that meet IEC standards. IEC 60320 is the standard specifying the components for connecting power supply cords to electrical equipment with a voltage rating of 250 V and a current rating of 16 A. There are different types of standardized IEC connectors that vary on the current rating, temperature rating, dimensions, and number of terminals.

IEC connectors are made up of paired components: a connector (male) and an inlet (female). Each IEC component is designated by a prefix “C” followed by a number. For instance, the C13 connector and C14 inlet each feature three conductors, support a current rating of 10 A, and have a maximum temperature rating of 700°C.

NEMA Connectors

NEMA connector is a category of power plugs and receptacles that are compliant with the standard set by the National Electrical Manufacturers Association (NEMA). NEMA standards are prevalent in North America, and some countries adapt to these standards.

NEMA connectors feature a distinctive coding system that describes their characteristics. The initial code identifies the locking mechanism: if it begins with the letter “L,” the connector has a twist-lock feature; if there’s no letter, the connector is non-locking. The second part of the code, a number before the hyphen, specifies the NEMA type, which denotes aspects such as the number of poles (current-carrying terminals), wire connections, voltage rating, and more. The number after the hyphen indicates the current rating in amperes, while the final letter designates the connector type: “P” for plugs and “R” for receptacles.

As mentioned earlier, NEMA connectors can be either non-locking or twist-locking. Non-locking NEMA connectors feature straight blades on their plugs, making them easy to connect and disconnect from their corresponding receptacles. In contrast, twist-locking NEMA connectors use curved blades that can be rotated and locked into place, preventing accidental disconnection. Twist-locking connectors are particularly suited for use in industrial and commercial settings.

Terminal Block

A terminal block is a modular, insulated device designed to connect or terminate multiple wires. It features a series of terminals aligned in a strip, with each terminal linked by a conductive metal strip inside the block. This metal strip facilitates electrical conduction between the connected terminals, while a clamping mechanism holds the wires securely in place. Terminal blocks can be oriented horizontally, vertically, or at a 45-degree angle, and they can be mounted on panels or DIN rails.

Terminal blocks can be categorized into the following types:

1. Based On The Structure

• Single feed terminal blocks are used in wire-to-wire connections. They have one input and one output contact.
• Multiple level terminal blocks have two or more levels of connection terminals. They reduce space and simplify wiring. DIN rail terminal block is an example of a multiple-level terminal block that is commonly found in power cabinets.

2. Based On The Application

• Ground Terminal Blocks
• Fused Connection Terminals
• Thermocouple Terminal Blocks
• I/O Blocks and Sensor Blocks
• Disconnect Terminal Blocks
• Power Distribution Terminal Blocks
• PCB Terminal Blocks

3. Based On The Clamping System

Screw Terminal Blocks

A screw within the terminal block presses the wire against the conductive strip, creating a secure connection. Screw terminal blocks are among the most widely used types and can handle a diverse range of wire sizes.

Spring-Clamp Terminal Blocks

In spring-clamp terminal blocks, a spring mechanism is employed to secure the wire to the conductive strip. These blocks are particularly effective for clamping smaller wires.

Push-In Terminal Blocks

Ferrules are fitted onto the ends of wires or conductors to facilitate their connection by simply inserting them into the terminal block. Ferrules can be either insulated or uninsulated.

Barrier Terminal Blocks

A spade or ring terminal is affixed to the end of a wire, and the connection is secured with a bolt and nut. Barrier terminal blocks are designed for use in environments with high vibration to prevent the loosening of wire connections.

USB Connectors

USB, or Universal Serial Bus, is a standard interface used for data transfer and power supply to electronic devices. Commonly found in smartphones, computers, and other consumer electronics, USB connectors facilitate these functions.

A USB connector comprises a male component that plugs into a female port. It typically features four or more shielded contacts enclosed in a plastic housing with a molded strain relief. The connector has an asymmetrical design (except for USB-C), which serves as a keying mechanism to ensure proper alignment.

There are several versions of USB: USB 1.0, USB 1.1, USB 2.0, USB 3.0, USB 3.1, and USB 3.2. Newer versions offer faster data transfer speeds, although many USB connectors are backward compatible with older versions.

USB connectors are also categorized by their receptacles and sizes, including USB-A, USB-B, USB Mini (Mini-A, Mini-B, and Mini-AB), USB Micro (Micro-A, Micro-B, and Micro-AB), and USB-C.

USB-A female connectors are commonly used as host ports in computers, hubs, or devices, allowing peripherals to be connected. Extension cables may feature a female A connector on one end and a male A connector on the other.

USB-A male connectors are typically found on devices like keyboards and mice and often come attached to a built-in cable. They are also used on USB memory sticks and are designed for board mounting.

USB-B female connectors are larger and are used in applications where size is less critical. They are known for their reliability and are often used in removable and through-hole board mount applications.

USB-B male connectors are usually located at the end of cables. Their affordability contributes to their widespread use.

USB Mini female connectors were common on older MP3 players, cell phones, and external hard drives as surface mount connectors. They are gradually being replaced by USB Micro connectors.

USB Micro connectors are smaller than their predecessors and include a fifth pin for low-speed signaling, making them suitable for USB-OTG (On-The-Go) applications.

Audio and Video Connectors Types

Audio and video connectors are a diverse category of electronic connectors designed to transmit audio and/or video signals. These connectors can handle both analog and digital signals and generally consist of a male (plug) component and a female (jack) component.

Audio connectors can support monophonic (single audio channel) or stereophonic (multiple audio channels) signal systems.

Some common types of audio and video connectors include:

Phone Connectors feature coaxial contacts: the tip (T), ring (R), and sleeve (S). These connectors often use a combination of 3 to 5 contacts. They are commonly found in phones, headphones, speakers, and various other audio devices.

DIN Connectors were originally standardized by the Deutsches Institut für Normung (DIN) and are used primarily for transmitting analog audio signals. They feature three or more metal pins arranged within a conductive ring and include a notch in both the plug and jack to ensure proper alignment during connection. The mini-DIN is a smaller variant of the standard DIN connector.

RCA Connectors are used for transmitting stereo audio and video signals. They feature an outer conductor and a central pin for the inner conductor. RCA connectors are commonly color-coded for easy identification: yellow for composite video, and red and white for stereo audio.

XLR Connectors are commonly used in professional audio, video, and lighting applications. These circular connectors typically feature three to seven pins and include a notch that acts as a keying mechanism to ensure proper connection.

HDMI Connectors, which stands for High-Definition Multimedia Interface, are used in contemporary home entertainment systems, projectors, computer monitors, and digital audio devices. They utilize transition-minimized differential signaling (TMDS) technology to handle high volumes of digital data. The standard HDMI connector types include Type A (standard), Type B (dual-link), Type C (mini), Type D (micro), and Type E (Automotive Connection System).

DisplayPort (DP) Connectors are designed to link audio and video sources to display devices. They are widely used for high-definition graphic displays and are commonly found in computer systems.

DVI Connectors, which stand for Digital Visual Interface, transmit both analog and digital video signals. Utilizing TMDS technology, DVI connectors quickly became a popular replacement for VGA connectors.

VGA Connectors feature 15 pins arranged in three rows within a trapezoidal housing and are used to transmit analog video signals. Developed by IBM in 1987, VGA connectors were widely adopted for video output in computers.

Chapter 4: What are electronic connector mounting and terminations?

Connector mounting refers to how a connector's leads are attached to or secured on a circuit board. The main types of mounting include surface mounting (SM), through-hole, hanging, cutout, and board-through methods. Although often used interchangeably, the terms "termination" and "mounting" have distinct meanings.

Mounting pertains to the overall method of installing connectors, including how they are interfaced, fastened, and attached. In contrast, termination focuses on the process of making the electrical connection, which can involve how the connector is attached at either end.

Mounting Types

The term "mount" can be somewhat ambiguous as it broadly describes how connectors are attached. Different types of connectors necessitate various mounting methods, which depend on the connector's lead configuration and type. Understanding the specific mounting requirements is crucial for proper installation and functionality.

• Pin Through Hole - Pin through hole mountings are used when the terminating leads are attached to a circuit board through holes placed in the board.

  

  
  
• Surface Mounting - Surface mounting attaches terminating leads using contact pads on the board.
• Panel Mounting - Panel mounting is a surface mounting where the connector is placed against a hole with connecting variations being threading or a nut to hold the connector in place.
• Hanging - With a hanging mounting, the connector is installed on the cable to which it is terminated.
• Cutout Mounting - Cutout mounting involves placing the connector at the edge of the board to take advantage of the edge placement. To provide for the mounting, the board has been cutout such that the connector can have a lower profile. The use of cutout mounting is due to the fact that there is no other space for placement.
• Through the Board Mounting - Through the board mounting is a combination of cutout mounting and panel mounting. Terminations mount through the board using holes in the board and solder on the same side as the connector’s mates as others are surface mounted to the side of the board the connectors mount from.

Termination Methods

Termination methods can differ based on personal preference, though some terminations may require specific types. The choice of termination method is primarily influenced by the specific needs of the application and the requirements of the project.

Through Hole Soldering

For board-to-board and wire-to-board connections, solder terminations can be applied to either through-hole or surface mount devices. In through-hole terminations, terminals are inserted into drilled holes and soldered onto contact pads on the opposite side of the board.

Surface Mount Termination

In surface mount termination, both the leads and mounting pads are located on the same side of the board. Components are positioned manually and then soldered using methods such as reflow or wave soldering. Terminals are attached to the contact pads on the same side of the board as the connector.

Crimping

A crimp connection involves compressing electrical wires and cables against a crimp termination or splice band. The compression reshapes the wire strands to create a low-resistance electrical connection, akin to a cold weld.

Crimping is crucial for reliable terminal connections. Improper crimping can result in electrical failures or even fires. Ensuring correct wire preparation, sizing, and using appropriate termination types, tools, and settings are vital for a dependable and permanent connection. The crimping process starts with evaluating and measuring the wire's cross-section.

The crimping tool is essential for proper crimping and can be either a ratchet or manual crimper. The jaws of the crimper must cover the entire surface area of the connector and are equipped with crimping dies designed to match the wire gauges. These dies may also be color-coded to indicate the correct placement of the wire.

The wire to be crimped should fit the connector’s barrel, typically 0.25 inches (0.64 cm) in diameter. Once the wire is placed in the crimper, the jaws are closed, and pressure is applied. This action compresses the wire, removing the insulation and exposing the conductors.

Ensuring a strong connection between the connector and wire is critical to prevent connection failure and potential damage. A final step in the crimping process involves twisting and tightening the exposed wire to ensure a secure fit.

The stripped wire should be inserted into the connector’s barrel until the insulation touches the barrel. Ensure that no exposed wire is visible at the barrel’s entrance or extending beyond the barrel into the terminal's tongue.

Place the connector and stripped wire into the crimper die horizontally, with the barrel side facing up and the flat side down. The die color should correspond to the wire’s insulation color, and it’s crucial that the die matches the wire’s gauge and size.

Position the crimper perpendicularly to the connector and wire, ensuring a firm grip. The crimper’s jaws should be closer to the connector’s tongue than to the wire’s insulation. Once properly positioned, close the crimper’s jaws with sufficient force to ensure that the wire is securely crimped and cannot be pulled out of the terminal.

To protect the crimped connection from environmental exposure, seal it with electrical tape or heat shrink tubing. Heat shrink tubing should be applied and heated until it shrinks to fit tightly around the connection.

Crimping eliminates the need for soldering, reducing the risk of brittle joints that can fail. Terminal manufacturers provide guidelines for the correct tools and materials needed to ensure a reliable connection, which should be followed to avoid wiring issues.

Ratchet crimp tools offer tactile feedback to confirm that the terminal crimp has been fully compressed and often feature color coding for selecting the appropriate die. Additionally, ratchet crimp tools will not release their jaws until the crimp is properly completed and secure.

Insulation Displacement Connectors

Insulation Displacement Connectors (IDCs) use sharp blades to strip the wire insulation as the wire or cable is inserted. When the wire is correctly positioned, the exposed wire area is cold-welded to the connector terminal, forming a secure and reliable connection. This insulation displacement method is frequently used in ribbon cable connectors as well as in telephone and network plugs.

Push In Termination

Push-in terminations are known for their reliability and durability, offering both permanent and easily releaseable connections. Wires are either stripped and pushed directly into the connector or secured using a lever to lock them in place. Besides the basic push-in and locking methods, there are various configurations of push-in terminations. While push-in terminations are commonly used with various connectors, they are best suited for applications where vibrations are minimal, as excessive vibration can disrupt the connection. Ensuring that the application meets the vibration rating requirements is essential for their effective use.

Conclusion

• Electronic connectors are devices that join electronic circuits. These devices are used in installing, assembling, and supplying power to electrical devices.
• The two main components of electronic connectors are the housing and the terminals.
• Electronic connectors have a male (plug) and a female (jack) component.
• Keying and locking mechanisms are important features of connectors that ensure correct and secure connections. A strain relief protects the connector assembly from mechanical stress.
• The number of contacts refers to the number of conductive elements which make an electrical connection. The contact pitch refers to the center-to-center distance of adjacent contacts or pins.
• Mounting refers to the manner of placing the connector to the electrical device.
• Termination refers to the method of fastening the terminals. The types of termination methods are soldering, crimping, and insulation displacement.
• Electronic connectors can be classified based on their level of interconnection.
• The electronic connectors discussed in this article are board-to-board connectors, power connectors, terminal blocks, USB connectors, and audio and video connectors.

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