An Overview Of PCB And PCB Fabrication

Printed Circuit Board, or PCB, is a board consisting of afiberglass or phenolic base that supports and holds electronic components together. It connects them electrically by laminating onto it etched copper outlines or diagrams created by a particular designer. In recent times, PCB fabrication is widespread and they are used in just about every electronic product and appliance ever invented.

The most common PCB orientations are single sided laminate, double sided laminate, and multi-layer. These classifications pertain to the number of copper layers in a single board. A single sided laminate is a PCB with a copper layer on only one side. It is the simplest and most common orientation that is even used by hobbyists who experiment with different board designs.

PCB FabricationDouble sided has two copper layers on both sides of the board that are connected via holes.This orientation allows for a more versatile circuit design. It also streamlines cross-linking of parts which are highly useful for more complex circuits. Multi-layered, as the name implies, has more than two copper layers sandwiched in between the board’s material. The extra layers are utilized for ultra complicated circuit designs that could not be accommodated by either single or double sided types.

A more modern orientation is recently introduced and it is called High Density Interconnect or HDI. This is an upgrade from the multi-layered type and ismainly used to make circuit boards smaller and lighter. These types of boards are commonly applied on smartphones and tablets.

When it comes to PCB fabrication, there are two methods of attaching electronic parts and they are called through-hole technology and surface-mount technology. Through-hole was the first method used in mounting electronic elements to the board. It was used from the advent of PCBs until the late 1980s when the surface-mount technology was introduced. Virtually all electronic devices used through-hole conventions in their PCBs until then.

Electronic parts such as diodes, resistors, transistors, capacitors, and integrated circuits have lead “legs” that are slotted in through holes and soldered on the other side. This scheme is actually more expensive to apply as it needs a lot of holes to be drilled perfectly, and areas of utilization are reduced when it comes to multi-layered boards because the holes needed to pass through all the layers for the components to be usable.

The second method and the more modern of the two is the surface-mount technology. This method worked out the limitations inherent to the through-hole technology. In using this scheme, re-designed electronic pieces with shorter legs are soldered straight on top of the circuit board. Surface-mount technology became popular in the 1990s as it can accommodate smaller elements and is flexible enough to apply it on both sides of the PCB without having to drill holes. It was groundbreaking as designers were able to create smaller patterns that have more complex functionality.

PCB fabrication may seem complicated for laymen but the procedure is quite simple. The basic process of PCB fabrication includes:

• Drawing and designing the PCB layout either manually or through a computer-aided system (CAS).

• Illustrating the fabrication and assembly scheme complete with diagrams, legends, and special instructions that will help the manufacturer.

• Etching the circuit pattern on the PCB base by either subtractive, additive, or semi-additive processes.

• Laminating the resulting etched PCB product.

• Drilling of holes based on the design.

• Plating and coating of the PCB.

• Applying solder resist to cover areas that should not be soldered.

• Printing of legends on both sides of the PCB.

• Applying bare-board test to ensure quality and correctness before actual assembly.

• Assembly of the PCB and its different electronic components.

• Packaging completed products for delivery.