PCB Technical - What materials are mainly assembled for PCB ?

PCB boards are a bit like layer cakes or lasagna-there are alternating layers of different materials, which are laminated together with heat and adhesive to make the result a single object.

FR4 substrate

"The base material or base material is usually glass fiber." Historically, the most common symbol of this glass fiber is "FR4". This sturdy core gives the PCB circuit board rigidity and thickness. There are also flexible PCB boards built on flexible high-temperature plastics.

Cheaper PCB circuit boards and perforated boards (as shown above) will be made of other materials, such as epoxy or phenolic resin, which lack the durability of FR4 but are much cheaper. When you solder it, you will know that you are using this type of PCB board-they have a very unpleasant smell. These types of substrates are usually also found in low-end consumer electronics products. Phenolic resins have a low thermal decomposition temperature. When the soldering iron is kept on the board too long, it will cause them to delaminate, smoke and scorch.

PCB copper

The next layer is a thin copper foil, laminated to the board with heat and adhesive. On ordinary double-sided PCB circuit boards, copper is applied to both sides of the substrate. In lower cost electronic devices, the PCB circuit board may have copper on only one side. When we refer to double-sided or double-layer circuit boards, we are referring to the number of copper layers in the lasagna. This can be 1 layer or up to 16 or more layers.

PCB board exposed copper, no solder mask or screen printing.

The thickness of copper can vary, and it is measured in units of ounces per square foot. Most PCBs have 1 ounce of copper per square foot, but some PCBs that handle very high power may use 2 or 3 ounces of copper. Each square ounce converts to about 35 microns or 1.4 thousandths of an inch thick copper.

PCB solder mask

The layer on top of the copper foil is called the solder mask. This layer makes the PCB circuit board green (or, in SparkFun, red). It covers the copper layer and insulates the copper traces from accidental contact with other metals, solder or conductive bits. This layer helps the user to solder to the correct location and prevents solder jumpers.

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

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

silk screen

Apply a white screen layer on top of the solder mask layer. Screen printing adds letters, numbers and symbols to the PCB circuit board to facilitate assembly and instruct humans to better understand the circuit board. We often use silk screen labels to indicate the function of each pin or LED.

The most common screen printing is white, but any ink color can be used. Black, gray, red, and even yellow screen printing colors are widely available; however, it is not common to see multiple colors on a single board.

The general composition of the above several PCB circuit boards, many circuit boards are expensive in the PCB process, and the choice of materials.