What are the main materials on PCB board

PCB boards are a bit like layer cakes or lasagna - alternating layers of different materials that are laminated with heat and adhesive, resulting in a single object.


FR4 substrate

 

The substrate is usually glass fiber. Historically, the most common symbol of this fiberglass is "FR4." This solid core makes PCB boards rigid and thick. There are also flexible PCB boards built on flexible hot plastic.

pcb board material

Cheaper PCB boards and perforated boards (shown above) will be made of other materials, such as epoxy or phenolic resins, which lack FR4 durability but are much cheaper. When you solder it, you will know that you are using this type of PCB - they have a very bad smell. These types of substrates are also commonly found in low-end consumer electronics. Phenolic resins have a lower thermal decomposition temperature, which causes them to layer, smoke, and burn when the irons stay too long on the plate.


copper

 

The next layer is thin copper foil, laminated to the plate with heat and adhesive. On a common double-sided PCB, copper is applied to both sides of the substrate. In lower-cost electronic devices, PCB boards may have copper on only one side. When we talk about double-sided or double-layer circuit boards, we're talking about the number of copper layers in the lasagna. This can be one layer or up to 16 or more.

pcb printed circuit board

Copper thickness can vary and is measured in oz/square foot by weight. Most PCBS have 1 oz of copper in one square foot, but some PCB boards that handle very high power may use 2 or 3 oz of copper. Each square oz translates into about 35 microns or 1.4 thousandths of an inch thick copper.

 

Resistance welding

 

The top layer of copper foil is called the solder mask. This layer makes the PCB appear green (or, SparkFun, red). It covers the copper layer and insulates the copper trace wire from accidental contact with other metals, solders, or conductive positions. This layer helps the user to weld to the correct position and prevents solder jumpers.

 

In the example below, the green welding mask is applied to most of the PCB board, covering small trace lines but leaving the silver ring and SMD pads exposed so that they can be welded to.

PCB pad

The most common solder mask is green, but almost any color is possible.

 

silkscreen 

 

Apply the white silkscreen layer to the top of the welding mask layer. silkscreen adds letters, Numbers and symbols to PCB boards to facilitate assembly and instruct humans to better understand the boards. We often use silkscreen labels to indicate the function of each pin or LED.

 

Silkscreen is most commonly white, but can use any ink color. Black, gray, red, and even yellow color are widely available; However, it is not common to see multiple colors on a single board.

 

The above materials are generally composed of PCB circuit boards, many circuit boards are expensive on the process, there is also the choice of materials.