An effective electronic system consists of a well-organized interconnection network that enables reliable communication between different electronic devices.

Power distribution and signal transmission require various types of interconnections to ensure proper functioning of your electronic devices. There are three classifications of electrical connectors based on their termination ends: wire-to-wire connectors, board-to-board connectors, and wire-to-board connectors.

In general, electrical connectors can be categorized into five levels of interconnection.

  • Level 0 involves connecting the basic circuit to its lead, such as the connection between the lead frame and a semiconductor chip.
  • Level 1 refers to the connection of a printed circuit board to an equipment lead, as seen in switches, dual inline package sockets, and chip carrier sockets.
  • Level 2 involves the interconnection of two or more PCBs. A common example is the connection between a motherboard and a daughterboard.
  • Level 3 occurs when two subassemblies are connected, such as a power supply to an associated subassembly.
  • Level 4 is the connection of a major subassembly to the input/output (I/O) port of the entire system.
  • Level 5 involves connecting physically separated systems, such as linking a computer to a printer or other components of a local network or other types of peripheral equipment.

Board-to-Board Connectors

Board-to-board connectors are commonly used to connect PCBs without the need for cables, allowing for space-saving advantages. These connectors are particularly suitable for systems with limited space.

The connectors are used to join PCBs in either a perpendicular or parallel configuration. A mezzanine connector is a type of connector used for stacking two PCBs on top of each other, although the term is also used to describe side-by-side or perpendicular PCB arrangements.

This type of configuration is often found in motherboard-daughterboard setups, which typically involve a parallel arrangement.

When selecting a mezzanine connector, several specifications need to be considered. These include the type of mounting, any constraints such as brackets, standoffs, or chassis slots and frames, mechanical requirements like stack height and tolerances, as well as separability.

The separability of the connector depends on factors such as the number of mating cycles required over its lifetime, whether the connector is permanent or separable, and the minimum and maximum insertion force required. Operating temperature and humidity are also important considerations. The standard for mezzanine connectors is EIA 700AAAB.

A backplane is an assembly of electrical connectors arranged in parallel, where each pin of every connector is connected to the corresponding pin of all the other connectors, forming a connector bus.

Backplane systems are widely used in telecommunication and computer systems due to their reliability and flexibility. These systems allow for the connection of multiple plug-in cards using a single backbone, creating a complete backplane system.

In such systems, a signal generated by a transmitter travels through several connectors before reaching the receiver. High-speed applications require backplane systems with strong signal integrity. For gigabit backplanes, the relevant parameters are the pin field and the backplane itself.

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As the data rate increases, there is a potential for the backplane channels to impede the transmitted signal. This can result in issues such as crosstalk, reflection, and inter-symbol interference (ISI) within the channels.

Reflection and crosstalk can degrade the signal edge rate, reduce signal amplitude, and introduce noise, ultimately impacting channel jitter performance. Signal integrity can deteriorate, particularly over long distances and at high data rates between channels.

The ideal connectors for backplane systems are those that provide excellent shielding and impedance matching. These connectors should also be able to withstand multiple insertions and removals of circuit boards.

Wire-to-Wire Connectors

Wire-to-wire connectors, as the name implies, are used to connect two wires. One end of the connector forms a permanent connection with the wire, while the other end creates a separate interface.

The permanent connection can be established using insulation displacement contact (IDC) or crimping methods. In IDC, the insulated wire is inserted into a sharp metal beam, which pierces the insulation and creates a secure metal-to-metal connection between the beam and the wire.

Crimping is typically used for discrete wire connections, while IDC is commonly used for terminating multiconductor cable conductors. IDC offers advantages in terms of mass termination and wire handling.

Wire-to-wire connectors come in a variety of housing geometries, including circular and rectangular designs with polymer housings made from different types of polymers. There are also metal shells available, primarily used in military applications.

Wire-to-Board Connectors

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A wire-to-board connector establishes a connection between a PCB and a wire. The wire connections are similar to those used for board connections and wire-to-wire connections.

Soldered or press-in two-piece connectors are commonly used, although card-edge versions are still in use. In separable connections, the mating interface may be the same as that of a wire-to-wire connector in similar products.

While there are many applications that use wire-to-board connectors, cable-to-board connectors appear to be more popular. This is because IDC offers advantages for cable assemblies.

How To Choose the Appropriate Electrical Connectors

It is important that you must choose the proper electrical connector that matches the design of your equipment. With the right wire connectors, you can take advantage of enhanced field maintenance and manufacturability as well as the reduction of space usage.

Current Rating

This refers to the amount of current that is passed on to the connected terminal. It is important to ensure that the current rating of the connector matches the capabilities of the terminals to which it is being connected. It is assumed that all circuits are carrying the maximum current.

Additionally, it is also assumed that the maximum wire gauge is being used.

Connector Size

The size of electrical connectors is greatly influenced by the trend of reducing equipment footprint while maintaining the same current capacity.

When selecting connectors and electrical terminals, it is important to consider the space requirements. In many cases, connections in trucks, vehicles, and mobile equipment are located in small compartments where space is limited.

Circuit Density

This refers to the number of circuits present in an electrical connector. Using a high circuit density connector eliminates the need for multiple connectors, maximizing efficiency and space.

However, there may be situations where using a 2- or 3-circuit connector is preferred for ease of recognition and simplicity. It is important to note that high circuit density connectors come with a compromise. There may be a potential decrease in the current rating due to the increased heat generated by multiple terminals within the housing.

For your RF and microwave product needs, you can contact SEI RF Microwave Components at (408) 374-1031. We offer a wide range of connectors, cable assemblies, antennas, adapters, isolators, and more.