Decomposition of PCB Substrate Material Selection Considerations

Decomposition of PCB Substrate Material Selection Considerations

In PCB manufacturing, the choice of substrate material is particularly important. Different boards have different properties, such as thermal expansion, heat resistance coefficient, flatness and other factors, which will affect the performance of the entire board. What factors should be paid attention to when choosing substrate materials?

First of all, everyone has to figure out where the materials they need are used for, and what characteristics they want these plates to have, so that they can buy the materials they really need.

For general electronic products, FR4 sheet is generally used. It is not a material name, but a material grade, which means a material specification that must be able to extinguish itself after the resin material is in a burning state. At present, there are many types of FR-4 grade materials used in general circuit boards, but most of them are composites made of so-called four-function (Tera-FuncTIon) epoxy resin, filler (Filler) and glass fiber. material, which has the characteristics of high temperature resistance, flame retardant, insulation and so on. In addition, the substrate will bend after being heated, and the expansion and contraction of the board will affect the components, which will cause the electrodes to peel off and reduce the reliability. Therefore, you should try to choose a plate with a small degree of bending, and the FR4 substrate material is a good choice.

The following factors should be considered when selecting PCB substrate materials:

(1) Select an appropriate substrate with a higher glass transition temperature (Tg), and the Tg should be higher than the circuit operating temperature.

(2) High heat resistance, generally required to have heat resistance of 250℃/50S.

(3) The flatness is good. In SMT, it is required to use a plate with a small degree of bending as much as possible, and the warpage degree is required to be <0.0075mm/mm.

(4) The coefficient of thermal expansion (CTE) is low. Due to the inconsistent thermal expansion coefficients in the X, Y and thickness directions, it is easy to cause PCB deformation, and in severe cases, the metallized holes will be broken, resulting in damage to components.

(5) Electrical properties, high-frequency circuits require the selection of materials with high dielectric constant and low dielectric loss, and insulation resistance, withstand voltage strength, and arc resistance must meet product requirements.

After understanding the above factors of substrate selection, I believe that it will save a lot of effort when choosing substrate materials.