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- October 31, 2022
- PCB knowledge
- (0)
- 05 mins
PCB substrate – guidelines and manufacturing
What is PCB substrate?
Circuit boards are made from a wide range of materials that have different performance characteristics, prices and certifications. One of the most important factors in determining the performance of your board is its substrate material. The material from which it’s made determines how well it will conduct electricity and heat away from electronic devices on your circuit board.
The PCB substrate is the base material that all components are mounted to. The most common PCB substrate include FR4 (flexible fiberglass), FR5 (fiberglass with carbon fibers), and paper-based materials like Kapton® or Mylar®.
Why PCB substrate matters?
The substrate is an important factor in the performance of your board. PCB substrate is what holds everything together and makes it possible for you to connect things together with wires, cables or solder points.
It’s important to choose one that meets your needs and budget. The performance of your circuit board depends on many factors, including the substrate material used and its thickness. The thicknesses vary based on their function, location on the board, and manufacturer capabilities but generally all chipsets will have at least one layer so it can be molded into shape before assembly onto larger components such as connectors/pots/switches etc.
Technical characteristics of PCB substrate
Some technical properties of PCB substrate are the following:
★ Adhesion
The adhesion of a substrate to its intended surface is an important factor in determining the strength and durability of your PCB. Some substrates are better than others at adhering to their surfaces, so look for those that have excellent adhesion properties.
★ Moisture absorption
The moisture absorption rate of the substrate is mainly related to the water content of the material. The water content ratio can be calculated by using K = S/A, where S is the surface area and A is the total area. In general, when there are large amounts of moisture in a product substrate, it will have a higher rate and vice versa.
★ Processing performance
A PCB substrate is a semi-conductive material used to form the base of a printed circuit board. PCB substrate can be used to make high-frequency circuits, but it’s not suitable for high-temperature or high voltage circuits.
★ Mechanical performance
The mechanical performance of PCB substrate is good. It is not easy to break.
Materials used for PCB substrate production
There are a lot of PCB substrate materials, depending on what sort of circuit you’re building. Some of them include:
FR4 (Flexible Reusable High Density Glass Epoxy)- This is a rigid plastic that’s used in applications like Arduino boards and Raspberry Pi computers. It’s also commonly used as an interconnecting layer between other types of FR4 PCB.
Copper-clad laminate (CuCl2)- This type of copper surface is covered by two layers; one with adhesive, which sticks well to glass or plastics but not metal; and another with solder paste or fluxes that help hold together the components during assembly onto a printed circuit board.
Other materials include polyimide, ceramic, and bismaleimide-triazine.
Bismaleimide-triazine, also known as B1, is a high performance engineering thermoplastic. It has been used in the aerospace industry for many years, but is now becoming more popular with electronic manufacturers.
How to produce PCB substrate?
The general process of PCB substrate production process is as follows:
● Pre-punching
● Drilling
● Paint checking, and exposure
Each step is done in a certain order and by different machines.
● The first step to produce the PCB substrate is pre-punching, which is used to remove the waste resin in the entire material.
● The next step is drilling. Laser drill machine, NC drill machine or CNC drilling machine are used in this step. After finishing, the PCB substrate should be inspected by AOl (Automated Optical Inspection) to find whether there are any problems with the drilling steps. Drilling is used to create holes in the substrate and pads on both sides of the board (especially for surface mount parts).
● Before being sent to exposure, the substrate needs to go through paint checking. In this way, we can ensure that we get good results after exposure. Paint checking is done by AOI. Paint checking is used to check the quality of the paint layer on your PCB.
● It’s time for exposure now! There are different types of exposure equipment for different sizes of plates (ultraviolet exposure machine or direct exposure machine).
● After exposure, there’s a process called coating for copper foil protection. This process is done in a dark room using vacuum coating machine. Qualified copper coil can be provided by top 10 PCB copper foil suppliers in China.
● We do the coating because if the copper surface is exposed to air or even a little water vapor during the etching process, it will react with air and oxidize rapidly, making the copper foil uneven and affecting the quality of subsequent processing. So coating can effectively prevent oxidation and reduce environmental pollution as well.
The above process is the general process of PCB substrate production and it is generally used for large-scale production. There are many other processes such as screen printing, hot stamping, inkjet printing, and so on.
How to select the proper PCB substrate?
While selecting PCB substrate, you must have to keep the following points in your mind:
What kind of material do you want? For example, if you want something cheap and easy to print (like plastic), then may be go with that instead of metal-backed boards made from copper or aluminum sheets. Metal-backed boards cost more than plastic ones because they require extra steps during assembly.
Some people may prefer using materials such as stainless steel due to their higher resistance levels against corrosion after prolonged exposure times without maintenance treatments.
◆ Base material:
The base material should be rigid enough to withstand the stresses of the PC8, such as bending and stress. It should also be able to withstand temperature changes. Finally, it must also be able to withstand chemicals used in manufacturing as well as impact from tools like drills or SMT soldering iron tips.
◆ Core material:
The core material is the conductive layer of your PCB. This can be made from any metal, but it must have an electrical conductivity at or above 20%. Copper has been used for years and remains one of the most popular choices for most applications.
Conclusion
A PCB substrate is a key component for your project. PCB substrate determines the performance of your PCB and helps protect it from being damaged by static electricity. So, it’s important to choose one that will last long enough for your project but also be flexible enough so that you have options when upgrading your equipment in the future.
