The Basics of PCB Manufacturing
PCB manufacturing begins with the design blueprints in the industry standard Gerber Extended or ODB++ file format. These files are used by software to encode the design into a data package that is sent to the manufacturer.
The technician takes the layered PCB stack to a mechanical press and places it into a special type of punch machine that drills holes through the layers to align them. Then, the layers are bonded together with heat and pressure from a laminating press.
Substrate
A substrate is the base layer on which a process occurs. It may be a rock that serves as the foundation for a coral reef, or the wafers of silicon used to make computer chips. The word is also commonly used in chemistry to describe the chemical component that is actually acted on and changed by another chemical.
In PCB manufacturing, the substrate is made of a non-conductive material like fiberglass-reinforced epoxy. It is coated with copper foil, and manufacturers etch a pattern into the foil to create the circuitry for the board. The etched surface is then covered with solder mask to prevent components from shorting with the copper traces on the board.
The etching process also creates pads that allow connections to be made with component leads. These connections are important for transferring electronic signals between components and the circuit board. pcb manufacturing They can be either analog or digital, and the assembler places these leads onto the pads on the PCB using an automated robot that has been fed a file that has preprogrammed the X,Y coordinates of each and every component.
Copper Layer
The copper layer is the topmost layer in a PCB and serves several functions. It is one of the most important parts of the PCB because it allows electrical signals to pass through. In addition, it also provides insulation and protects the circuit board from damage.
During the PCB manufacturing process, there are many factors that can affect the thickness of the copper. One of these factors is the copper trace width. It is important to select the correct trace width to avoid shorting. In addition, the copper trace width should match the pad spacing of the components to prevent overheating.
Another factor that affects the thickness of the copper is the amount of overlap between the traces. Overlap between traces can lead to heat damage, which in turn can cause the board to warp or twist. This can be avoided by balancing the copper coverage in each layer of the PCB.
In step four, the manufacturer bonds a layer of copper foil to the substrate material of the PCB. This is known as fiberglass-copper clad laminate (CCL). Then, the bare copper is imaged with photoresist. Once the image is clear, it is etched to reveal the copper underneath. During this process, the manufacturer applies a coating of tin to help protect the copper during the etching process.
Layer Alignment
Layer alignment refers to how the inner and outer layers correspond with each other. Once the copper and solder mask are added to the laminate films, technicians use a machine known as the optical punch to align the inner and outer layers using registration holes. The precise correspondence ensures that the punch can accurately punch through all the layers. Once the punch is done, another machine performs an automated optical inspection (AOI) of the inner layer to confirm that there are no errors on the boards.
The AOI compares the inner layer with the extended Gerber design that the manufacturer received and ensures there are no errors in the boards. If there are no errors, the PCB moves on to the next step of manufacturing and production.
You can use the six alignment buttons in the top row of tools to align a selection to Artboards, to other layers within the same Artboard, or to a specific reference layer. Hovering over any of the options shows you a preview of how your selection will look with each option selected.
Optical Inspection
Optical inspection is one of the most vital tools that CMs use for PCB fabrication. This is because it allows the CM to ensure that the board has been constructed according to its design specifications, and that it will function as intended in real life.
It uses a combination of light sources and cameras to examine the quality of a completed circuit board. The camera captures images of the board that are then evaluated by the inspection system using image processing algorithms.
Compared to manual visual inspection, which is a time-consuming and labor-intensive process, automated optical inspection (AOI) is more reliable. This is because it allows the CM a higher throughput with the same number of inspectors, and it reduces the risk of human error. In addition, it is possible to detect defects that would otherwise be missed by manual inspection. These include misalignments that cause a circuit to perform sluggishly or not at all. AOI can also detect scratches, stains, open circuits and short circuits on the surface of the board. In some cases, CMs may use X-ray inspection to evaluate particularly complex or densely constructed boards.
Assembly
Once the bare PCB passes fabrication, it goes through a PCB Manufacturing Supplier final battery of tests to ensure quality. These normally involve continuity testing (checking for open or short circuits between the test points you specified in your design files). The boards that pass this stage are ready to move on to assembly.
In the assembly process, the bare board is coated with solder paste. This is then melted using a heating process to fasten all the components onto the board. Once the soldering is complete, the assembler will inspect the completed PCB for defects like component alignment and solder joint quality. These inspection steps are typically performed using automated optical inspection (AOI).
This is a powerful tool that uses high-resolution cameras to visually inspect the surface layers of the PCB. It can detect many assembly defects, such as misalignment between components, lifted components during cooling, and a variety of other errors. This is an essential step in ensuring that the assembled PCB performs as designed. If the assembler finds any problems, they can be corrected in a timely manner to keep production on schedule.