A comprehensive introduction to PCB connectors

With the advent of technology, complex electronic systems are now being introduced demanding highly compact and precise PCBA components on them. In order to connect two wires of a complex system special connectors are used. There can be many reasons to make a connection, for example, to distribute power signals or data signals. Using Terminal Blocks connectors makes complex harness routing more professional.

What is a PCBA connector or terminal block

PCBA connectors, also known as electronic blocks, mounting terminals or terminal blocks, are mounted on the PCB board by the SMT assembly technology or through-hole technology of the PCB assembly company. These are modular and insulated devices that are mounted on PCBs and are generally used to make a secure connection between more than one wire. Terminal blocks are not only used to join two or more wires in a single electronic system but also they reduce the need for solder iron, soldering wire, and insulating tapes. Connections made through terminal blocks are safer, easier, quicker, and more reliable than any other connection technique. 

In order to separate electrically adjacent blocks of terminal blocks, they are made up of a solid body of some insulating material especially plastic or ceramic. The Internal part of the terminal block plays part in conducting the signal through the terminal, so it is made up of some conducting material especially copper along with corrosion-resistant material. Generally, the current-carrying element, typically a terminal bar or metal strip, is housed within the insulating body of a terminal block. Terminal blocks are typically modular in design, and their mounting arrangement allows them to easily mount or unmount on any PCB. 

Types of PCBA Connectors

Following are different types based on wiring methods and uses of PCB connectors.

Classification based on wire connection methods:

  • Screw-In Terminal Block

Screw-in terminals are also called screw terminals or terminal caps, according to the size and thickness of the wiring, they are divided into P1/P2/P3/P4/P6, etc. This type of connector is the most commonly found in electrical systems, consisting of the insulated body with screws that are used to hold the wires.  

Usage: 1. Insert the wire from the bottom of the sleeve and connect the wire to the bottom of the metal conductor. 2. Pass the other wire through the wire groove and tighten the rotating cap so that the head of the metal conductor pierces the wire and connects.

Screw-in PCB terminal block

  • Spring Caged Terminal blocks

The main difference between the spiral cage terminal block and the screw-in terminal block is only the difference in the method to connect the wire. A small screwdriver is typically used to push down a tab with springs, which makes space for wire to be pushed in, and after releasing the tab spring push back to hold the wire in place. 

Spring Cage PCB Connectors

  • Terminal Strips PCB connector

As the name implies, it refers to an insulating part that can carry more groups of mutually insulated connecting components and provide support and fixation. Screws are used to secure wires in terminal strips. The actual body is what distinguishes these from screw-in terminal blocks. Terminal strips are typically used in applications that do not require din rail. Mostly these terminal blocks are used where small-sized blocks are required for example cable repair.  

PCBA terminal block

  • Pluggable Terminal Block

In this type of terminal block male and female pluggable connectors are available. Normally, the wires are connected to the male side. After that, both male and female parts can be connected or disconnected the wires by inserting the male side into the female side of the terminal block. They are mostly used in such applications which require frequent component connection and disconnection.

Pluggable Terminal Block

  • Push-In Terminal Blocks

As the process of miniaturization of electronic devices accelerates, more users are using push-in blocks. This connector is a variation of a mechanical connector, usually self-locking. They have one or more ports that can only use one wire per port, to disconnect simply twist and pull the wire. Their greatest feature is that they can be reused with solid wire of the same size or smaller.

Push-in terminal blocks are similar to Spring Caged Terminal blocks in appearance. Only the difference with other types is these have a point that needs to be pushed. You can sometimes secure the wires with your finger, but it is recommended to use a screwdriver. 

Push-In PCBA Terminal Blocks

  • IDC Terminal Block

The Insulation Displacement Connector, or IDC, was first used in the telecommunications industry. It is one of the subdivisions of the connection device category. The most common application is the wiring of computer motherboards, and as this technology is updated, more and more autonomous vehicles use it in wiring harnesses.

Usage: Before insertion, there is no need to remove the wire insulation. Inside the terminal block, two sharp blades will remove insulation to make the desired connection of wire. 

IDC Terminal Block

Classification according to the use of the connector:

  • Ground Terminal Block

Terminals connected to grounded electronic equipment are called ground terminals, and these are mostly screw-in terminal blocks, which are generally used to connect the wire to the ground.

Due to the need to contact the ground, the material of this PCB connector is almost all copper, but there are also some copper-aluminum transition terminals. Because this kind of terminal is made of more expensive materials and has anti-corrosion ability, its price is higher, and it is widely used in advanced fields such as petrochemical industry and high-speed tram tracks.

PCBA Ground Terminal Connector

  • Fused Terminal Block Terminal

This type of terminal block omits the use of an external current protection circuit as they have a fuse inside. This fuse is in series with incoming and outgoing wires. Some of these have fuse failure indicator LED which aids in a visual indication of the inside fuse. 

PCBA Fused Terminal Block Terminal

  • Thermocouple Terminal Block

A thermocouple block accepts thermocouple lead to making a connection. A typical terminal block cannot be used to connect thermocouples leads, this i because an undesired junction results whenever a thermocouple lead connects to any conducting material.

PCB Thermocouple Terminal Block

Are PCB Connector Terminals Safe?

Terminal blocks are usually made up of plastic which means these are electrically safe to touch by limiting the access to live terminals that may have some voltages. Terminal blocks also improve the safety of electrical systems. They can accomplish this by isolating, grounding, and protecting other electrical system components. Terminal block connector also provides safer access to live terminals and can be used as testing points to measure voltages or other electrical parameters in an electrically protected way. In this way terminal blocks also make testing easier and safer while troubleshooting electrical systems. The following is an introduction to the manufacturing materials of the connector:

  • Thermosetting Plastic EP

Provides excellent physical stability along with high flame resistance. The main disadvantage of using this material is that it provides poor toughness. 

  • Thermoplastic polycarbonate PC

Provides highly insulating properties. Geometrical stability, good toughness, and good thermal resistance are some advantages that this material provides, but due to high toughness, more stress beyond certain limits may cause breakage and cracks. 

  • Thermoplastic Polyester PBT

Main advantage of using this material is that it provides high flame resistance, geometrical stability, and excellent electrical properties. 

  • Glass fiber reinforced nylon PA-F

This material offers low water absorption and high rigidity, and is suitable for use in high-voltage protection.

Application of PCBA Terminal Block

Main application of terminal blocks is generally electrical panels and electrical systems to connect wires to specific points on a circuit in an easy and safe manner. They make electrical system wiring simple by allowing wires to be easily connected and disconnected. They can typically be found in: 

  • Electrical panels 
  • Electrical devices 
  • Electrical grounding 
  • Components that require frequent connection and disconnection 
  • On components that fail or must be replaced
  • Motor termination points
Conclusion

When designing a complex electrical system, bus bars and PCBA terminals prove to be valuable tools. There are various types of terminal blocks available in the market. PCB terminals make connection easier and more convenient, as well as allow for more connections in a small area in a more professional way.

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