How Are Electronics Boards Assembled?
Electronics Boards Assembled
The printed circuit assembly (PCA) process brings together components to create a working electronics board. It is a complicated step, and the quality of this part of the manufacturing process will significantly affect the performance and reliability of the final product.
Before the PCA is assembled, a number of different checks must be performed. First, the boards must be inspected for surface mount and through hole components. This involves conforming to a number of rules, such as ensuring the correct polarity and orientation of components, and is carried out using an automatic tool called a pick-and-place machine. In addition, electrical tests are also run to check that the components are functioning correctly and that traces are properly routed.
Once the design has been checked and finalized, the output data files are sent to a fabrication facility to start building the electronics board. The facility will start by etching the various layers of copper, creating the different planes and traces that will make up the final board. During this process, a number of different chemicals and gases are used to clean the copper, making it ready for the next step.
How Are Electronics Boards Assembled?
A photo resist mask is then applied to the copper, protecting it from a number of different chemicals and gases. Then, the panel is exposed to UV light to harden the photo resist. Once this is done, it is sprayed with an alkaline developer, which removes the unhardened photo resist mask and exposes the copper for a second time. After etching, the panels are bathed in a series of different chemical solutions to clean them and protect the copper from corrosion and oxidation.
At this point, the layers of a PCB are ready to be laminated and fused together. A laminator takes the layers and puts them into a press, where high temperatures are applied to bond the layers together. Afterwards, technicians will add a solder mask to the top of the panels. This is an extra layer of protection, preventing the copper from oxidizing and helping it to stay functional.
The bare copper on the panels are then plated with metals, including gold and silver. These metals help the connections between the traces and component parts to conduct electricity effectively. They also provide the additional strength that is necessary to support components. After the plated copper is dried, technicians will apply a finish to the panels. This is to prevent them from getting scratched and damaged in the final assembly process.
Once the panels are finished, they are sent to a specialized soldering facility. This will either use a wave soldering or manual soldering process to attach the through-hole (through-thickness) components to the circuit board. If there are any sensitive through-hole components in the design, they should be highlighted to ensure that a specific soldering process is used to avoid damaging them. In addition, the through-holes should be filled with no-clean flux, which reduces the risk of them contaminating the rest of the board.