Assembly of printed circuit boards

17 Nov, 2021

By hqt

Assembly of printed circuit boards is the assembly of individual elements and components onto a previously prepared surface. The versatility of the process makes it possible to use different base materials and other elements, which contributes to reliability and durability.

There are two mounting methods:

1. Superficial. When components are mounted directly to the surface of the circuit.

2. Through. When the elements are mounted in the holes of the PCB. This method is also called TNT technology.

It is the assembly that plays a huge role in the high-quality and reliable operation of various devices, which are based on PCBs.

Assembly of printed circuit boards

Wave soldering

This is a method that allows you to solder wired electronic parts or connectors after manual or automatic installation on aboard.

To do this, the entire module from the soldering side is first covered with flux, then preheated, and then passed over one or two waves of solder and covered. If lead-free solder is used, the soldering temperature is approximately 260 ° C. After that, the entire unit is cooled to reduce the thermal load on the circuit.


  • more efficient processes thanks to fast and economical technology, especially with wired components;
  • does not depend on the size and density of the elements;
  • minimum thermal stress on components: the module is usually soldered on one side only.

Wave soldering is used primarily for through-hole components, but it can also be used to mount SMD components on the bottom of a circuit.

If you need to solder only through-hole components, which by their design are designed for high mechanical loads, use this method.

Often two waves (chip wave and lambda wave or Wjortmann wave ) are used, which follow one another and ensure a reliable connection of THT parts to the top side of the PCB and SMT to its bottom in one working step.

Important technological parameters, in addition to temperature, are the immersion depth of the circuit, the angle of pulling, the duration and type of the solder wave.

Assembly of printed circuit boards

Through-hole reflow soldering (THR)

Through -hole reflow soldering combines the special mechanical stability of fasteners with a significant level of automation in SMD processes.


  • high quality of the procedure;
  • ensuring significant mechanical stability of the connecting components;
  • the ability to process THR and SMD components in one procedure.

When installing according to the THR method , solder paste consisting of flux and solder is placed under pressure through the template into the drilled holes on the PCB where the spare parts are to be installed . After that, the parts are mounted, pressed into the filled with solder paste.

SMT installation

Surface mount parts are soldered with contact parts directly to the top or bottom surface. Since such components do not require connecting wires that go through the holes and are soldered. The surface mount method allows very tight picking and use of both sides of the PCB.


  • quality of processes with the ability to reproduce due to a high level of automation;
  • Layout density: the ability to use printed circuit boards on both sides due to surface mounting;
  • process efficiency thanks to the ability to process THR and SMD components in a single procedure.

Solder paste is applied under pressure before mounting SMD parts to suitably plated PCBs. After that, the board is completed with parts and the entire module is soldered. Reflow soldering is used for the top surface of the board. SMD components on the bottom surface are often glued and wave soldered.

Compared to through-hole components, SMD components have a low connection strength to the PCB, so the soldering points on the circuit are usually not designed for significant mechanical stress.

In cases where mechanical loads are comparable to those on push-through components, so-called THR solder anchors are used.

Assembly of printed circuit boards

Press-in technology

This installation method is characterized by simplicity and high fastening strength. Done without soldering.


  • there is no thermal effect on the connecting components;
  • high joint strength;
  • efficient layout.

The press-in method is used primarily when the PCB and its parts cannot be subjected to thermal stress.

Fastening without soldering is performed by pressing in the pins. In the case of automated picking, pneumatic presses are used.

Due to the special shape of the outer edges of the pins, they deepen during pressing into the metal coating and provide a gas-tight electrical contact.

Assembly of printed circuit boards

Direct insert technology

The direct mechanical attachment in a modular manner guarantees flexibility and compactness.


  • no thermal stress on the connecting components due to solder-free mounting;
  • direct mounting: connecting components to terminal blocks;
  • flexible and cost-effective wire-to-board and board-to-board solutions.

SKEDD direct insertion technology

SKEDD is an innovative wiring technology for connecting through-hole connectors to a PCB. Installation is carried out without tools and without an additional corresponding part. Side connector tabs provide a secure and vibration-resistant attachment.


  • adaptive PCB layout: expand functions without additional component and storage costs;
  • direct mounting: easy manual connection, vibration proof;
  • intuitive actuation thanks to the colored pressure element.

SKEDD insertion method combines the advantages of two recognized types of installation - tech pressing and pasting. Due to the high mounting force, when using a press-fit, a tight connection is formed between the contacts and the printed circuit board.

Assembly of printed circuit boards

In turn, direct inserts require bumpers on both sides of the circuit, so this method is only suitable for splicing board to board or wire to board at the edges. The innovative SKEDD insertion technology allows for collapsible and stable couplings to be created with ease while providing absolute PCB layout flexibility


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