What Is a PCB?
PCB is essential components for electrical engineering.
It is possible to fabricate electronic circuits by placing transistors, resistors, and other components on a mainly copper wiring pattern on the surface of an insulator (plastic) and soldering them together. PCB is used in almost all electronic devices (TVs, PCs, smartphones, home appliances), and the electronic circuits built into devices are operated by PCB.
Japan was the first country in the world to obtain a patent for PCB around 1936, and the development of the technology has been progressing. As a result, Japan was the world’s largest producer in terms of production value around 1990. In recent years, production of electronic devices has shifted to China and Asia, and large quantities are produced in China and Asia.
Uses of PCBs
PCBs are used as wiring boards for PCs, televisions, and electrical equipment as well as for electronic construction.
The PCBs for these particularly precise electrical devices already have the necessary circuit patterns formed on the board itself, and electronic circuits are completed simply by placing components on them. For even higher density, there are also multilayer boards with multiple layers of circuits on a single board, which are used in electronic equipment such as PCs and smartphones.
There are also many types of materials and hundreds of varieties, depending on the application. Generally, rigid materials are the main materials used, but in recent years, flexible materials (films) are increasingly being used for smartphones and other mobile applications, with many soft flexible substrates being used.
Printed Circuit Board Manufacturing Methods
PCBs are made by drilling small holes in an insulating board and plating the holes with copper or other materials. (called through holes or via holes). By soldering electronic components and wires to the small holes, a circuit can be built by allowing electricity to flow through them. In the case of a multilayer board, signals in the board are connected to other layers through holes and via holes.
PCBs can be single-sided, double-sided, or multilayered. The more layers there are, the more circuits can be built, which saves space.
Materials Used
For home appliances (refrigerators, washing machines), paper phenol substrates made of paper impregnated with phenol resin are the main materials used as substrates for PCBs. For PCs, smart phones, automobiles, measuring equipment, etc., where reliability is required, glass epoxy substrates (glass cloth impregnated with epoxy resin) are used.
Aluminum substrates with good heat dissipation are sometimes used where heat dissipation is required. Recently, demand for these substrates has been increasing due to the trend toward EVs, which require higher current.
Flexible substrates made of thin polyimide or polyester film have also emerged. While flexible substrates have low mechanical strength, they are flexible and can be bent. The materials used for these substrates are required to be flame-retardant (i.e., they do not burn easily even if set on fire). For this reason, halogen-based substances are used, and some customers require halogen-free materials for environmental reasons.
In recent years, circuit patterning methods have become more automated, and products are being developed to accommodate smaller size and higher density.
Structure of PCBs
There are several types of PCBs, each with a different structure, material, etc., depending on the purpose.
Single-sided substrate
A substrate with copper foil only on the patterned side. Only relatively simple patterns can be realized. It is the cheapest type of printed circuit board to manufacture and is the most commonly used type for self-made PCBs.
Double-sided PCBs
PCBs with copper foil on both the front and back sides. Patterns can be drawn on the front and back sides, and more complex patterns can be realized than on a single-sided board. Although it is a bit more advanced, it is also possible to make it yourself. Be careful of pattern misalignment between the front and back sides. Solid ground pattern boards also require through holes.
Multilayer Substrate
Used for complex patterns that cannot be realized with double-sided boards (computer boards, etc.) or when patterns need to be stacked due to board size restrictions (cellular phones, portable audio equipment, etc.). Multilayer substrates with up to 8 layers are used. For boards that require mass production, it is necessary to combine equipment costing hundreds of millions of yen per unit to manufacture several hundred thousand boards per month, making it an equipment industry.
Materials of PCBs
There are several types of printed circuit board materials, each with different properties. Select the one that matches your purpose.
Paper Phenol Substrate
Paper is used as the base material, and the adhesive resin is phenolic resin. Also called “Bake substrate” or “Bakelite.” It has been used for a long time. It is inexpensive and easy to process, but the substrate easily warps and has poor heat resistance and moisture absorption. It also has poor insulation resistance and high-frequency characteristics, and through-holes cannot be formed.
Paper Epoxy Substrate
This substrate uses paper as the base material and epoxy resin as the adhesive resin. It has characteristics intermediate between paper phenol substrate and glass epoxy substrate. It is made as a single-sided substrate. It has superior heat resistance, moisture absorption, and electrical characteristics compared to paper phenol substrates, but is inferior to glass epoxy substrates.
Glass Epoxy Substrate
This is a printed circuit board manufactured by glass fiber containing epoxy resin. Currently, the most widely used type, most multilayer boards are glass epoxy boards, which are used in a wide range of applications, from thin boards as thin as 0.2 mm to boards up to 2.4 mm in thickness for power equipment, motherboards, etc. They have low dimensional change and excellent durability. It also has good electrical and mechanical properties. However, workability is poor, and special tools are required. Although the cost is higher, functionality is improved.
As described above, there are various types of PCBs, and various materials are used. Design rules differ greatly depending on the type of printed circuit board, so please contact a specialized manufacturer if you have any problems.