Choosing the appropriate substrate is a crucial step in the PCBA SMT process. The choice of substrate directly affects the performance, reliability, and manufacturing cost of PCB boards. The following will discuss in detail how to choose the appropriate substrate from several key aspects.
1、 Understand usage conditions and performance requirements
Firstly, it is necessary to clarify the usage conditions and required mechanical and electrical performance of PCBA. For example, if the product needs to work in high temperature or humid environments, the heat resistance and moisture resistance of the substrate are particularly important. Meanwhile, electrical properties such as dielectric constant and insulation strength are also factors that need to be considered when selecting substrates.
2、 Determine the number of copper foil faces
According to the design requirements of PCBA, determine the number of copper-clad foil surfaces for the substrate. Single panel is suitable for simple circuits, while double-sided or multi-layer boards are suitable for more complex circuit designs. Multilayer boards can provide higher wiring density and better electrical performance, but their manufacturing costs are also relatively high.
3、 Consider the thickness and size of the substrate
The thickness and size of the substrate are also important factors to consider when selecting. The selection of thickness should be based on the size of the PCB, the quality of the load-bearing components, and the required mechanical strength. A thinner substrate is beneficial for reducing product volume and weight, but may sacrifice some mechanical strength; A thicker substrate can provide better mechanical support, but it may increase the overall thickness and weight of the product.
4、 Evaluate electrical performance and other characteristics
When selecting substrates, it is also necessary to consider their electrical properties, such as dielectric constant, dielectric loss, etc. These performances will directly affect the transmission quality of signals and the efficiency of circuits. In addition, attention should also be paid to factors such as the glass transition temperature (Tg), coefficient of thermal expansion (CTE), surface smoothness, and metalization ability of the pores of the substrate to ensure the stability and reliability of the PCB during high-temperature welding, assembly, and use.
5、 Common types of substrates and their characteristicsFR4: This is a common glass fiber epoxy resin substrate with high mechanical strength and electrical properties, suitable for most electronic products.
CEM-1: This substrate has good heat resistance and processability, making it suitable for applications in high-temperature environments.
Aluminum substrate: Aluminum substrate has excellent heat dissipation performance, especially suitable for products with high power density.
6、 The trade-off between cost and performance
When selecting substrates, it is also necessary to balance the relationship between cost and performance. High performance substrates often have higher prices, while low-cost substrates may have limitations in certain performance aspects. Therefore, when choosing, reasonable decisions should be made based on the actual needs and budget of the product.
Choosing the appropriate substrate is a crucial step in the PCBA processing. By gaining a deep understanding of usage conditions and performance requirements, determining the number of copper-clad foil faces, considering thickness and size, evaluating electrical performance and other characteristics, and balancing cost and performance, we can select the most suitable substrate type for a specific PCBA project.
