PCB Terminals

Terminals for printed wiring are used as a more modern, technological, but at the same time - a more expensive alternative to direct soldering wires to the board.

Unlike terminal blocks used for other purposes , terminal blocks on a printed circuit board have a smaller size, no lower currents and voltages are calculated (except for barrier terminals), they have a special design of the clamping stand and lower operating costs.

The scientific literature does not propose a unified classification of terminal blocks. Nevertheless, a number of parameters can be distinguished by which it is logical to divide the studied products into groups:

By clamping method

• Screw terminal blocks. The wire is clamped with a screw, which is fixed in the stand with a screwdriver. This is a cheaper way.
• Screwless, push-in terminal blocks. They do not contain screws, a lever or spring-loaded semi-automatic clamp is used. Such terminal blocks are more convenient in operation, easier to connect, but have a higher price.

By clamp type

• Petal clamp

In this connection, the compression force is due to the tightening of the screw, however, the fluidity of the conductor material can lead to a weakening of the connection.

• Elevator clamp

The elevator clamp provides exceptionally high quality screw connections: large contact area, high clamping force, easy installation and no need for service

• TOP clamp

When using the TOR-clamp, the conductor is not fixed by the screw itself, but by the lever on which the screw presses. This guarantees a high clamping force and completely tight contact.

• Spring clamp
• Bolt clamp
• Crimp contact

By connection features

• Whole

Mounted on a board and are used for direct connection of conductors

• Detachable (bursting)

Pluggable terminal blocks consist of 2 parts. The first one is attached to the board, the second one, depending on the purpose of the device, can be mounted on a cable, on a DIN rail, on a panel. The reciprocal part is connected to the main, as a result of which a stable contact is formed.

How to protect wires

• Without protection

Standard Low Cost Terminal Blocks

• With embossed clip

Models of this group have an additional small plastic overlay around the hole for the wire. This is done to increase the distance between the conductors and reduce the likelihood of a short circuit.

• Circular conductor protection

In this case, the terminal clamp stand has been modified. It completely covers the wire. This increases the reliability of the connection and eliminates the possibility of disruption of the conductor. ^[2]

By current strength

• Ordinary
• Barrier

By row

• Single row
• Double row
• Multirow

The terminal blocks may contain several "floors" for ease of installation and denser placement on the printed circuit board.

The main technical characteristics of terminal blocks on a printed circuit board include:

Electrical and physical properties

• Amperage / voltage . The main electrical characteristics of the terminal blocks are defined as withstand current and allowable voltage.
• The temperature regime determines the maximum and minimum temperature threshold at which the stable operation of the terminal strip is garnished. Depends on the case material and the contact part. Standard: -40С to + 105С, with short-term tolerance up to + 220С

Manufacturing Materials

• Body material. As a rule, refractory dielectric plastic is used as the material for the body, usually polyamide: plastic based on linear synthetic high molecular weight compounds. At the same time, in the modern industry of terminal blocks, kapron (PA6) or more advanced nylon (PA66) is used. Also sometimes used is a liquid crystal polymer (LCP), which has enhanced heat resistance.
• Contact material. To create a stable connection, steel materials are used: tinned brass , copper and its alloys, phosphor bronze and other materials with low resistivity.
• Clamp Stand Material Stainless or galvanized steel , nickel-plated brass are used - materials that are protected from corrosion , chemical oxidation.

Wiring Specifications

• Pitch (distance between the contacts on the terminal block case, measured in mm)
• Cross section (maximum permissible thickness of the connected conductor, measured in mm2)
• Number of contacts (number of metal contacts for connection to the board)
• The angle of the connected conductor (for ease of installation and the possibility of tight placement of terminal blocks on the printed circuit board, some models of terminals are made at different angles, typical options: 0, 45, 90, 135)
• Case dimensions (main dimensions of the product, measured in mm in width, height, length)
• Tightening forces (the force required to tighten the screw to fix the conductor in the stand. Measured in Newton meters)

The manufacturing process for new terminal block models begins with the design and determination of the shapes and sizes of future products. The production of standard models - from the reception and rejection of raw materials (both for buildings and for contacts). Then, punching of the contacts and casting of the cases are started in parallel. When the main elements are ready, they go to the assembly workshop. At this stage, manual or automated labor is used. The final stage is a comprehensive check of terminal blocks for defects. It, in turn, passes in several steps: Measuring digital test, withstand voltage test, ROHS testing, temperature test, glow wire tests, visual control. At this stage, the identified rejects for processing, quality products go to the warehouse. ^[3]

Terminal blocks are actively used in industry, especially - electrical engineering , radio electronics , instrumentation, industrial control systems . Some examples of using terminal blocks on a printed circuit board:

• Switching network devices
• Server controllers
• Frequency converters
• Controllers
• Power supplies
• Control systems for rail vehicles
• Signal converters
• Drive controls

Mostly, terminal blocks are used in the following industries:

• Lighting
• Security systems
• Warning systems
• Industry automation
• Communication and switching.

Wave soldering (wave mounting) / double wave solder

The classic way to mount electronic components. The printed circuit board with the terminal blocks installed in the corresponding holes heats up and passes over the solder wave. Excess solder is cut off, or removed by a directed stream of hot air. ^[four]

End-to-end printed wiring by soldering reflow solder. (soldering THR)

The essence of the technology is that the soldering of THT components is carried out in a reflow oven. To do this, first, the required amount of solder paste is applied to the mounting holes of the THT components, then the components themselves are installed in the holes, and then reflow soldering takes place. ^[five]

SMT Surface Mount (SMD)

Main article: Surface Mount

The main difference between this method and the "traditional" technology - through-hole installation is that the components are mounted on the surface of the printed circuit board. The advantages of TMP are manifested due to a complex of features of the element base, design methods and technological techniques for the manufacture of printed units.

Pressing

Solderless connection obtained by pressing the connection between a specially profiled contact and a through metallized hole in the printed circuit board. Thus, there is no need to heat the board. This method is especially effective in the case of mounting on a multilayer (up to 36 layers) board ^[6]

Direct Join

A method of mounting terminal blocks on a board that does not imply the use of solder or press-in and without the use of a pin strip. The terminal block is connected directly to the corresponding contact posts on the edge of the printed circuit board, which are part of its circuit.

International Certificates

• The main certification authority for terminal products is the International Electrotechnical Commission (IEC). It sets the standards and rules for the production and operation of terminal blocks and carries out their certification. Moreover, the check concerns not only the products themselves, but also the equipment and raw materials from which it is made. The verification takes place in 3 stages, according to the results an IEC certificate of compliance is issued
• Certificate of the laboratory for standardization and certification in the field of safety engineering ( UL ), which in particular determines the fire resistance and heat resistance of the terminal block.
• Eurasian Compliance ( EAC ) - a certificate (mark of conformity), indicating that the product has passed all the assessment procedures established in the technical regulations of the EurAsEC Customs Union. This means that it meets the requirements of all technical regulations applicable to these products.
• Quality Management Certifications (ISO9001: 2008, 9001: 2004, OHSAS 18001)
• From 1.07.2016 Mandatory for all manufacturers is compliance with the ROHS directive (restriction of harmful substances in products)

Depending on the purpose of the application and the environment, explosion proof certificates ( EX ATEX), proof of dust and moisture protection (IP degree) may be required for terminal blocks

Local certificates

Depending on the country, additional technical regulations and quality standards may apply to the manufacturer. In Russia, until 2104, the GOST R certificate (Rostest certificate) was mandatory for terminal product suppliers, now it is mandatory to obtain a certificate of compliance with the technical regulations of the customs union for low-voltage equipment (TS TR NVO) ^[7]

European manufacturers:

European companies occupy a leading position in terms of production volumes and registered patents for terminal blocks.

Phoenix Contact

Main article: Phoenix Contact

The largest manufacturer of terminal blocks for connecting wires, Din rail and interface modules. The headquarters is located in Germany - the city of Blomberg. The flagship and leading innovator in the world of terminal products. The line of terminals on the printed circuit board is one of the main ones, called COMBICON, has more than 200 types of terminals and is constantly updated. The series are divided into groups depending on the purpose and scope of application (there are explosion-proof, moisture-proof rulers).

The Phoenix Contact Deutschland group of companies includes twelve enterprises. Nine company-owned manufacturing enterprises abroad. Almost 50 sales subsidiaries and more than 30 representative offices in different countries, including and in Russia

High price segment. ^[eight]

Weidmüller

A major manufacturer of automation systems and industrial connections. Initially, the company specialized in the production of textile goods. Nowadays, the company produces a wide range of industrial products, terminal blocks for printed circuit boards (OMNIMATE Signal series) are not the main line and has about 150 models, mainly screw terminals.

Weidmüller Group is an international holding represented by production sites, trading companies and representative offices in more than 80 countries. Wiemuller is widely known for the production of connectors and terminal blocks for din rail and related products: markings, components. In 2014, Weidmüller had sales of 673 million euros.

High price segment. ^[9]

WAGO Kontakttechnik

Main article: Wago

A major German manufacturer of terminal blocks, clamps, connectors, electronic components for industry. Headquartered in Minden, terminal blocks on a printed circuit board are presented. Gradually moves from the production of components - to the production of end modules for automation systems, controllers, transformers. Nevertheless, known worldwide for the invention of the “Cage Clamp” clamp. PCB terminal blocks are poorly presented and are not the main line. MCS series has about 50 types of terminals, mainly includes large industrial connectors with wire protection for surface mounting.

WAGO has 33 national offices and 7 major plants located in Germany, USA, India, China and other regions. Wago Brand Widespread Worldwide

High price segment.

Asian manufacturers:

Asian manufacturers of terminal blocks are characterized by the fact that they are less involved in development and R&D compared to their Western counterparts, and they mainly produce analogues. Two groups of manufacturing enterprises can be distinguished here: the first includes those that select several of the most popular series of terminal blocks of western terminal brands and begin to produce their analogues in the second or third lines (not the main stream). Such companies rarely have the necessary certificates of international commissions; product quality is often not satisfactory

On the other hand, in the 2nd group, Asian manufacturers who more thoroughly approached the issue of copying Western models. The release of terminal blocks on the board is one of - or the main type of production process. Such companies also make analogues of Western brands, but often have their own unique lines, carefully choose the raw materials and organize the production process, conduct activities in accordance with the requirements and technical regulations of international certification organizations. Some of the companies of the 2 group:

Degson Electronic

A major Chinese terminal block manufacturer for various applications. The headquarters is located in Qixi Province, in the southeast of China. One of the pioneers in the field of copying Western terminal brands. PCB terminal blocks are one of the main lines - about 300 models. The company also produces Din rail terminals and transformer terminals and accessories. It appeared in Russia at the beginning of 2000 and quickly captured a certain share of domestic consumers of terminal products due to low prices and reasonable quality. However, with the growth of the distribution network, Degson in Russia, prices for their terminal blocks began to rise, and delivery conditions became tougher. Nevertheless, today Degson Electronic is one of the leaders in the market share of terminals in the middle price segment. ^[ten]

Wanjie Electronic

Former Degson Electronic production unit, which left its structure in 1992 by a decision of the board of directors. At the moment, it conducts independent business activities, headquarters - Tsiksi Province, PRC A highly specialized enterprise. 96% of the assortment is occupied by terminal blocks on a printed circuit board; it also produces breadboards and accessories. The company entered the Russian market in 2012, offering quality analogs of Western and already Chinese terminal blocks on a printed circuit board at a lower price. Wanjie is not involved in the active development of the distribution network in Russia, it has only one official distributor, which provides some flexibility in work. Компания Расширяет ассортимент вглубь, адаптируя и кастомизируя свою продукцию под требования заказчиков из разных стран. На данный момент основная линейка насчитывает около 400 моделей клемм с различным шагом, сечением провода и количеством контактов. ^[eleven]

Низкий ценовой сегмент.