Assambly of printed circuit boards
Assambly of printed circuit boards is the assembly of individual elements and components on 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 installation methods:
1. Superficial. When components are installed directly on the surface of the circuit.
2. Through. When the elements are mounted in the holes of the PP. This method is also called TNT technology.
It is the assembly that plays a huge role in the quality and reliable operation of various devices, the basis of which are software.
This is a method that allows you to solder wired electronic parts or connectors after manual or automatic installation on the board.
To do this, the entire module from the solder side is first coated with a flux, then preheated, and then held over one or two waves of solder and covered. If lead-free solder is used, the soldering temperature is approximately 260 ° C. After the entire assembly is cooled to reduce the temperature load on the circuit.
- greater process efficiency due to fast and economical technology, especially components connected by wires;
- independent of the size and density of the elements;
- minimal thermal stress on components: the module is usually soldered only on one side.
Wave soldering is mainly used for processing components for through mounting, however, it can also be used to mount parts for surface mounting on the bottom of the circuit.
If you need to solder exclusively end-to-end components that are designed for high mechanical loads, this method is used.
Often two waves are used (chip-wave and lambda-wave or Wörthmann wave), which follow one after another and ensure reliable connection of THT parts to the upper side of the printed circuit board and SMT - with its lower part in one operation.
Important technological parameters, in addition to temperature, are the immersion depth of the circuit, the pull angle, the duration and type of solder wave.
Through hole reflow soldering (THR)
The method of reflow soldering through a through hole combines the special mechanical stability of the bonds with a significant level of automation of surface mounting processes.
- high quality of the procedure;
- providing significant mechanical stability of the connecting components;
- the ability to process THR and SMD components in one procedure.
- When mounting according to the THR method, a solder paste consisting of flux and solder is laid under pressure through a template in the drilled holes on the PP where the parts need to be installed. After that, the parts are mounted, pressed into filled with solder paste.
Parts for surface mounting are soldered by contact parts directly to the upper or lower surface. Since such components do not require connecting wires that pass through the holes and are soldered. The surface mounting method makes it possible to very tightly pick and use both sides of the PCB.
- quality of processes with the ability to reproduce due to the high level of automation;
- layout density: the ability to use printed circuit boards on both sides due to surface mounting;
- process efficiency due to the ability to process THR and SMD components in a single procedure.
- Before installing parts for surface mounting on a suitably coated metal plate, solder paste is applied under pressure. 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. Components of the SMD type on the bottom surface are often glued and brazed by wave soldering.
Compared to the components for through mounting, the parts for the surface - have a low strength of connection with the printed circuit board, therefore, the soldering spots on the circuit are usually not designed for significant mechanical loads.
In cases where mechanical loads are comparable to those of through-hole components, so-called THR solder anchors are used.
This installation method is simple and high mounting strength. It is done without soldering.
- there is no thermal effect on the connecting components;
- greater joint strength;
- efficient layout.
The pressing method is used primarily when the PP and its parts cannot be exposed to temperature stress.
Bonding without soldering is done 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.
Direct insert technology