What are printed circuit boards made of?

As PCB technology evolves, so does the answer to this question. Industry leaders, such as Allegro Services, are constantly reinventing the way printed circuitry is produced. Telescoping strategies and increasing environmental considerations, make PCB engineering one of the most exciting arenas in technology today.

Let’s start with a quick PCB 101.  Printed circuit boards are electrical devices used in a variety of applications.  From cell phones to ovens, if you own any semi-sophisticated electronic, chances are it has a PCB. Printed Circuit boards work by using electricity’s natural movement from high voltage components to low voltage components in a predetermined path “printed” onto the surface. When you place the desired object in between two opposing voltage points, the electrical current passes through the object causing it to “fire”.  There are additional objects you can insert to further manipulate the process and several layer options, but for now, let’s just keep it simple.  Printed circuit boards have four main layers, each of which are made from different materials. To keep the answer clear, we are going to address each layer separately.  

Substrate

The substrate is the thickest layer of the PCB.  It is the foundation on which everything rests. This cured layer is typically made of Fiberglass; however, a high temperature plastic is becoming more popular for products needing increased flexibility. The fiberglass variety most commonly used is called FR4.  This is where the electrical components are soldered. Historically, the process of soldering circuit boards required the use of lead, but again innovation has created a safer and nontoxic process to replace the antiquated standard.

Conducting Material

For the electricity to flow, it must have a conductor.  Copper is used for this process. This is either done by laminating or etching.  Once adhered, this predetermined foil copper pattern acts as the conduit material for the electrons to flow through. Simpler devices may only require the use of one layer, though devices using as many as sixteen layers is not uncommon. This is also where you will find soldered accessories such as transistors, LEDs, and capacitors.

Solder Mask

Solder masks have a variety of applications.  First and foremost, it protects the copper from oxidation and general damage from the elements. It also helps to hold everything perfectly in place perfectly without shifting or unintended electrical contacts.  This finishing layer is usually comprised of a lead, tin, and silver or gold mixture. The substance is blanketed over the entire board except in places requiring external solder work.

Silk Screen

The silkscreen is basically the key to your circuit board map.  It is printed information on the surface of the board to indicate where key components are. Originally done with silk, the substance currently used for this printing is a synthetic mesh, usually polyester.

As I mentioned earlier, there are several varieties of printed circuit boards that require different methods to create.  In creating some of these variances, additional materials and chemicals are often used.  Having said that, the above information is what one would typically find in the most common printed circuit boards.