1Introduction

Printed Circuit Boards (PCBs) are used in almost all electronic applications. From mobile phones to aircrafts, going through medical devices or industrial machinery, all of the electronic products used daily are supported by PCBs.

A printed circuit board: PCB, is a non-conductive substrate plate that is used for the assembly and interconnection of electronic components through routes or tracks of a material conductor recorded on the substrate.

The PCBs are most commonly made out of fiberglass, composite epoxy, or another composite material. Different electronic products have different requirements on the PCB base material.

Most PCBs for simple electronics are simple and composed of only a single layer. However, more sophisticated electronic circuits such as computer graphics cards or motherboards use to have multiple layers, sometimes up to sixteen or more, called “Multilayer” PCBs.

Typical PCB substrates are made from a composite of:

- Some kind of Reinforcement Material or core providing the "skeletal" support for the laminate.

This part of the PCB gives strength and dimensional stability. Teflon fiber or Quartz cloths are used as reinforcement materials. The FR-4 composite material is a good example of core material for PCBs.

The FR-4 is a composite material composed of woven fiberglass cloth with an epoxy resin binder that is flame resistant used as common reinforcement material for PCBs fabrication.

- Resin Binder System:

It provides the "glue" to bind the laminate together. Some examples of this kind of binder materials are thermoplastics, thermoplastics or general purpose resins.

- Conductive or Catalytic Surface Coating :

It provides the basis for creating the circuit pattern.

Once the PCB is manufactured, the components assembled and the PCB verified two types of products are usually applied to the same PCB. First, some kind of cleaner or flux solvent is applied to the PCB. Then a protective coating is applied covering the circuit. This final protective coating avoids the copper to oxidize and gives a greater durability to the plates.

Main advantages of the use of PCB’s in electronic circuits are the following [1-2]:

- The size of component assembly is reduced as well as the weight.
- Quantity production can be achieved at lower unit cost and the wiring and assembly can be automated.
- They ensure a high level of repeatability and offer uniformity of electrical characteristics from assembly to assembly.
- The location of parts is fixed, which simplifies identification and maintenance of electronic equipment and systems. Moreover, Inspection time is reduced because printed circuitry eliminates the probability of errors.
- Printed wiring personnel require minimal technical skills and training. In addition, chances of short-circuited wiring are minimized.
- Circuit characteristics can be maintained without introducing variation in inter-circuit capacitance and parasitic effects.

Fig. 1. Example of PCB.