Introduction and analysis of PCB materials and properties

As one of the important components of electronic equipment, PCB is responsible for connecting various electronic components. Its performance directly affects the quality and stability of electronic equipment. The material selection of the PCB board is one of the key factors affecting the performance of the PCB board.

This article will conduct a comparative analysis of common PCB materials in order to select suitable materials for different circuit board designs. At present, the common PCB board materials are mainly divided into the following categories:

PCB board material classification

1、CEM-1,CEM-3

The cost of composite fiberboard is lower than that of glass fiberboard, which solves the problems of insufficient hardness of cardboard and difficulty in punching fiberboard.

Disadvantages: Although the electrical performance is close to the glass fiber board, it still cannot completely replace the FR-4 material. Only some circuit boards with low requirements can use this material instead of FR-4.

2、FR-4

FR-4 material is one of the most common PCB board materials and is widely used.

1) Good temperature tolerance: Large operating temperature range (50°C to 115°C); high Tg value (about 180°C);

2) Good mechanical properties to maintain the integrity of the circuit board structure

3) Good insulation performance, thermal stability and other characteristics, and low price.

4) Low hygroscopicity: FR4 material has a low moisture absorption rate of 0.10% after soaking in water for 24 hours

Disadvantages: large dielectric constant drift, insufficient flame retardancy, etc.

3、Metal material

The metal material is aluminum, copper, iron, etc. Here mainly focuses on aluminum and copper substrates.

1) Thermal expansion

The metal substrate can effectively solve the problem of heat dissipation, so that the thermal expansion and contraction of different materials on the circuit board can be alleviated, and the durability and reliability of electronic equipment can be improved.

2) Heat dissipation

According to the circuit board factory, at present, many double-sided boards and multi-layer boards have high density and high power, so it is difficult to dissipate heat; and metal-based printed boards can solve this heat dissipation problem.

3) Dimensional stability

Metal substrates are much more dimensionally stable than sheets of insulating material.

4) Wide range of applications

Aluminum substrates are used in a wide range of fields, such as audio equipment input and output amplifiers, balanced amplifiers; computer CPU board floppy disk drives, power supply units; automotive electronic regulators, igniters, power controllers; LED lights for lamps and lanterns.

Disadvantages: The cost of materials is high, and it is easy to generate electromagnetic fields, which requires shielding treatment.

4、Ceramic materials

Ceramic material is a new type of PCB board material,

1) Large carrying capacity, 100A current continuously passes through a 1mm 0.3mm thick copper body, and the temperature rise is about 17°C; 100A current continuously passes through a 2mm 0.3mm thick copper body, and the temperature rise is only about 5°C;

2) Better heat dissipation performance, low thermal expansion coefficient, stable shape, not easy to deform and warp.

3) Good insulation, high withstand voltage, guarantee personal safety and equipment.

4) Strong bonding force, using bonding technology, the copper foil will not fall off.

5) High reliability, stable performance in high temperature and high humidity environment

Applications: high-power power electronic modules, solar panel components, etc; High-frequency switching power supply, solid state relay; Automotive electronics, aerospace, military electronics, high-power LED lighting products

Disadvantage: It is fragile and can only make small-area circuit boards; it is expensive, and ceramic circuit boards are mainly used in some relatively high-end products.

5、 Polytetrafluoroethylene (Teflon, etc) material

1) High-temperature resistance - the working temperature can reach 250°C.

2) Weather resistance - it has the best aging life among plastics.

3) High lubrication - the lowest coefficient of friction among solid materials.

4) Low-temperature resistance - it has good mechanical toughness; even if the temperature drops to -196°C, it can maintain an elongation of 5%.

5) Corrosion resistance - it is inert to most chemicals and solvents, resistant to strong acids and alkalis, water, and various organic solvents.

6) Good electrical properties - PTFE has a low dielectric constant and dielectric loss in a wide frequency range, and has high breakdown voltage, volume resistivity, and arc resistance.

Applied to high-speed transmission and microwave circuits

Disadvantages: Difficult to process and high cost.

PCB board material performance comparison

1. Dielectric constant

The dielectric constant is one of the important indicators that affect the conductivity of the PCB board. Different PCB board materials have different dielectric constants. Generally speaking, the smaller the dielectric constant, the smaller the attenuation of the electrical signal during transmission, and the faster the transmission speed. Among the common PCB board materials currently on the market, the dielectric constant of FR-4 material is about 4.5-5.5, while the dielectric constant of polytetrafluoroethylene material is only 2.1, and the material with the smallest dielectric constant is fluorinated Polyurethane material with a dielectric constant of only 1.8. For high-speed circuit board design, choosing materials with a smaller dielectric constant can improve transmission speed and transmission distance.

2. Mechanical strength

The PCB board needs to withstand various mechanical stresses during use, so it needs to have a certain mechanical strength. Mechanical strength mainly includes bending strength, tensile strength, hardness, and other indicators. Silicon carbide material has high hardness, good bending resistance, and tensile strength, and is suitable for high-temperature and high-strength environments. The mechanical strength of FR-4 material is also relatively good, but it is prone to deformation and cracking in high temperature and high humidity environments, so reinforcement treatment is required. PTFE material has poor mechanical strength and generally needs to be compounded with other materials.

3. Thermal stability

The PCB board needs to withstand certain thermal stress during use, so thermal stability is also one of the key indicators. Silicon carbide materials and FR-4 materials have high thermal stability, can work stably in high-temperature environments, and can withstand repeated heat and cold cycles. PTFE material also has good high-temperature resistance and can work in high-temperature environments.

4. Flame retardant performance

The PCB board needs to have a certain flame retardant performance during use to prevent safety accidents such as fire on the circuit board. Silicon carbide materials have relatively good flame retardancy, high heat resistance, and fire resistance. The flame retardancy of FR-4 material is also good, but in some special high-temperature and high-humidity environments, the flame retardancy will decrease, and it needs to be treated. The flame retardancy of polytetrafluoroethylene material is poor, so it needs to be treated with fire prevention.

Based on the above analysis, the material is suitable for circuit board design in high-temperature and high-strength environments, FR-4 material is suitable for general circuit board design, and PTFE material is suitable for high-speed transmission and microwave circuit board design. Choosing the right PCB material can effectively improve the conductivity, mechanical strength, thermal stability, and flame retardancy of the circuit board, improve the quality and stability of the circuit board, and is suitable for different electronic equipment applications.