How to choose materials for pcb: a comprehensive guide

In the design and manufacturing process of electronic equipment, PCB (printed circuit board) as the connecting hub between electronic components, the choice of its material and thickness is particularly critical. In this article we will introduce the material of pcb and how to correctly select the material of pcb to help you more quickly select the pcb suitable for their products.

 

 

 

PCB material selection

PCB circuit boards are made of a wide variety of materials, each of which has its own unique performance characteristics and adapts to different application scenarios. Next, we will explore several common PCB materials in depth.

1.FR-4 Material

FR-4, a glass fiber cloth and epoxy resin composite material, showing excellent mechanical strength, insulation properties and heat resistance. Its dielectric constant is approximately 5-5, making it suitable for most electronic devices. In addition, FR-4 is flame retardant, effectively curbing the spread of fire. As a result, this material is widely used in a variety of fields such as consumer electronics, computers, communication equipment, and automotive electronics.

2. Metal Substrates

Metal substrates are made of metals such as aluminum or copper, covered with an insulating layer and then attached with copper foil, which gives them excellent heat dissipation and vibration resistance. At the same time, the metal substrate also has good electrical conductivity, which improves the conduction ability of the PCB board. It is particularly suitable for applications requiring high thermal performance, such as LED lighting, automotive electronics and power modules. In addition, the metal substrate also excels in withstanding large mechanical stress.

3. Ceramic Substrate

Ceramic substrates stand out for their high thermal conductivity, low coefficient of thermal expansion and superior insulation. Despite its brittleness and relatively high cost, its low dielectric constant facilitates high-speed signal transmission. As a result, ceramic substrates are commonly used in high-frequency circuits, power devices, and LED lights that require heat dissipation. At the same time, its excellent insulation and high temperature characteristics also make it ideal for aerospace and military and other extreme environments.

4.Flexible Substrates

Performance Characteristics: Flexible substrates, with their use of flexible materials such as polyimide (PI) or polyethylene terephthalate (PET) as the base material, show excellent flexibility and bending resistance. Such substrates can be easily bent, folded or even twisted, thus perfectly adapting to compact spaces or applications requiring special bending shapes.
Application Scenario: Flexible substrates are very common in flexible displays, cell phones, and wearable devices and other electronic products that require folding or bending functions. With the increasing popularity of the Internet of Things and wearable devices, the demand for flexible substrates is growing rapidly.

Reason for choosing: Flexible substrates meet the needs of miniaturization, lightweight and complex form design, providing more possibilities for innovative design of electronic products.

5. High frequency materials (such as PTFE)

Performance characteristics: PTFE and other high-frequency materials are known for their low loss factor and excellent insulating properties, and are able to maintain stable electrical characteristics in high-frequency environments. However, it should be noted that the mechanical strength of this type of material is relatively weak and the processing difficulty is high.

Application Scenario: High-frequency materials are particularly suitable for areas requiring high-frequency, high-speed signal transmission, such as 5G communications and satellite communications. They are also often used in measuring instruments and medical devices that require high precision and stability.

Reason for selection: High-frequency materials ensure high quality and high speed signal transmission, making them ideal for applications in environments with stringent requirements for signal integrity.

 

Factors to consider when choosing PCB materials

These are some of the factors that must be considered before selecting materials for printed circuit boards:.

1. Material type and properties

The choice of PCB material can significantly affect its functionality and reliability. It is important to understand the material properties such as dielectric constant (Dk), loss angle tangent (Df) and coefficient of thermal expansion (CTE).

2. Heat Management

If heat is involved, then thermal properties are very important, especially for high power applications. The main thermal properties to be studied are as follows.

Glass Transition Temperature (Tg): At this temperature, the material becomes more flexible from a rigid state. Therefore, materials with higher Tg are more suitable for use at high temperatures.

Decomposition Temperature (Td): This is the temperature at which the material begins to decompose. In very difficult conditions, better indication appears in higher Td.

3. Manufacturing process compatibility

The material chosen should also be compatible with the manufacturing method employed, i.e. through-hole or surface mount technology (SMT). For example, SMT relies on FR-4 for good drillability, while flexible PCBs require materials such as polyimide that do not break during bending.

4. Environmental Factors

Always evaluate the PCB’s operating conditions, as humidity, rising and falling temperatures, and exposure to chemicals can all affect the material selection process. Ensure that the selected material can withstand these conditions without degradation.

5. Frequency Range

In situations involving high frequency signals, it is critical to select materials with low dielectric loss. In this case, high speed PCBs may require special materials.

 

Summarize

PCB material selection needs to take into account a variety of factors, including product performance requirements (such as high-speed signal transmission to choose a low dielectric constant, low loss factor materials), operating frequency and signal integrity (high-frequency and high-speed applications to choose the right material to reduce signal attenuation, distortion), environmental adaptability (such as resistance to high temperatures, humidity, chemical corrosion and other characteristics of the different environments), the cost budget (balancing performance and cost), as well as the Manufacturing process (considering material processability, solderability, etc.) to ensure stable and reliable operation of PCBs in specific applications.