Process of Assembling a Circuit Board

The process of assembled circuit board begins with the creation of the substrate, or core. This is made from fiberglass and acts as the PCB’s “skeleton.” A thin layer of copper is then added, either as foil or a full coating. The copper layer is essential because it provides the conductive pathways, or traces, needed to communicate electrical signals between different parts of the board.

Depending on the type of circuit board being built, additional layers of copper and substrate are added. A two-layer circuit board features a copper layer on both sides, while multi-layer boards feature internal layers that provide more routing options.

Once the substrate is ready, it is impregnated with an epoxy resin. This makes the surface of the board water-resistant and gives it some rigidity. After this is done, the copper layer is etched to create the circuitry that will be used on the board. This can be done through a variety of methods, and the design is checked for errors using a process called Design Rule Checking (DRC). The layout is also tested to ensure that the components will fit correctly on the circuit board.

After the copper is etched, the circuit board is plated. This process coats the copper with a layer of nickel-gold or silver. The plated layer protects the copper from oxidation and allows for more effective soldering. The circuit board is then drilled and plated with holes that will be used for connecting the individual components on the circuit board.

The Process of Assembling a Circuit Board

Assembling the PCB is done with a pick and place machine, or, in special cases, by hand. In either case, it is a very labor-intensive process. The assemblers have to be very precise and familiar with the layout of the circuit board in order to avoid mistakes. The assemblers are also required to use special tools for working with small surface-mount components, such as a fine tip soldering iron and tweezers. They must also wear an anti-static mat and wrist strap, as they are working with very tiny components that can easily be damaged by static electricity.

Once the pick and place process is complete, the circuit board is placed into a reflow oven. This is heated to 250 degrees Celsius, or 480 degrees Fahrenheit, which is hot enough to melt the solder paste that holds the surface-mount components in place. The reflow oven also speeds up the assembly process by heating the components and substrate simultaneously.

Once the reflow process is completed, the assemblers will place the remaining components on the circuit board. These are inserted either through the holes surrounded by conductive pads, or, in the case of surface-mount technology, placed onto the exposed copper surfaces of the circuit board. In the former case, the component leads line up with conductive pads or lands on the substrate, and are held in place by solder paste. In the latter case, the components are affixed to the pads with glue dots. Once the reflow and placement processes are complete, the assemblers will test the circuit board to ensure that it is functioning properly. If not, it is sent back for rework or scrapped.