PCB assembly

This term covers the whole process of various components assembly, soldering etc. The result is complete printed circuit board with all component which is a heart of all electronic devices.

The PCB assembling is completely automatic process performed on automated production line. Single machines are integrated within the system. Single steps of the whole process are design to result in functional electronic device.

Printed circuit board assembly process begins with placement of PCB on the conveyor.

In the first stage the soldering paste is added according to the metal matrix and optical control system checks on the right amount of paste and proper deposition.

Second part of the process is component picking and placement. The mounting machine loaded with reels of components picks the components from the reels or other dispensers and places them onto the correct position on the board with added solder paste. Proper placement of the components is controlled by laser and optical inspection.

Third stage of the PCB assembly process is soldering. PCB is placed in the brazing furnace with nitrogen atmosphere where the soldering process is performed in accordance with computer-controlled temperatures profiles.

In the case when only SMD components are scheduled to be used, the assembling process is complete and PCB is ready for inspection.
Automatic optical inspection is performed using optical tester with synthetic color image processing. The main goal of the inspection is to check placement and positioning of all components. If the BGA type of the SMD component is used, the PCB is inspected also by X-ray Focal Spot Verifier with flexible sample holder and specialized software.

In case of mounting of THD components, the PCB continues from brazing furnace in third stage to specialized workplace where the THD components are manually mounted. Based on number of components and THT through-hole pins density is decided whether hollow wave soldering is the right choice or it is more usefull to use selective soldering machine. If hollow wave is to be used, the whole PCB with all the components passes through the wave. In case of selective soldering only individual components are soldered using soldering jet.

The SMD components can be mounted on both sides of the PCB. In this case the PCB goes from the  brazing furnace back to first stage. The adhesive is placed on the PCB instead of soldering paste. A mounting machine places all the SMD components and the PCB continues to a soldering furnace. The adhesive is now cured to withstand the high temperatures when the PCB is being hollow wave soldered. After THD components placement the whole PCB is ready for hollow wave soldering. The inspections are to be done when the whole process is completed.