The printed circuit board consists of an insulating substrate, the circuit board itself, and printed wires or copper traces that provide the medium through which electricity flows through the circuit. The substrate material is also used as PCB insulation to provide electrical insulation between conductive parts. A multilayer board will have more than one substrate that separates the layers. What is a typical PCB substrate made of?

PCB substrate material

The PCB substrate material must be made of a non-conductive material because this interferes with the current path through the printed circuit. In fact, the substrate material is the PCB insulator, which acts as a layer piezoelectric insulator for the board circuit. When connecting wires on opposite layers, each layer of the circuit is connected through holes plated on the board.

Materials that can be used as effective substrates include fiberglass, teflon, ceramics and some polymers. The most popular substrate today is probably FR-4. Fr-4 is a fiberglass epoxy laminate that is inexpensive, provides a good electrical insulator and has higher flame retardancy than fiberglass alone.

PCB substrate type

You will find five main PCB substrate types on printed circuit boards. Which substrate type will be used for the exact printed circuit board depends on your PCB manufacturer and the nature of the application. PCB substrate types are as follows:

Fr-2: FR-2 is probably the lowest grade of substrate you will use, despite its flame retardant properties, as indicated by the FR name. It’s made from a material called phenolic, an impregnated paper impregnated with glass fibers. Cheap consumer electronics tend to use printed circuit boards with FR-2 substrates.

Fr-4: One of the most common PCB substrates is a fiberglass braided substrate containing a flame retardant material. However, it is stronger than the FR-2 and does not crack or break easily, which is why it is used in high-end products. To drill holes in or process glass fibers, PCB manufacturers use tungsten carbide tools depending on the nature of the material.

RF: RF or RF substrate for printed circuit boards intended for use in high power RF applications. The substrate material is composed of low dielectric plastics. This material gives you very strong electrical properties, but very weak mechanical properties, so it is important to customize the RF board for the right type of application.

Flexibility: Although FR boards and other types of substrates tend to be very rigid, some applications may require the use of flexible boards. These flexible circuits use thin, flexible plastic or film as the substrate. Although flexible plates are complex to manufacture, they have particular advantages. For example, you can bend a flexible board to fit a space that a regular board cannot.

Metal: When your application involves power electronics, it must have good thermal conductivity.This means that substrates with low thermal resistance (such as ceramics) or metals that can handle high currents on power electronic printed circuit boards can be used.