PCB substrate material selection considerations decomposition

In PCB manufacturing, the selection of substrate material is particularly important. Different boards have different properties, such as thermal expansion degree, heat resistance coefficient, flatness and other factors will affect the performance of the whole board. What factors should we pay attention to in the selection of substrate materials?

For general electronic goods, generally choose FR4 plate, it is not a material name, but a material grade, which means that the resin material after burning state, must be able to self-extinguish a material specification. There are many types of FR-4 grade materials used in general circuit boards, but most of them are composite materials made of so-called Tera-FuncTIon epoxy resin with Filler and glass fiber, which have the characteristics of high temperature resistance, flame retardant and insulation. In addition, the substrate will be heated after bending, board expansion and contraction will affect the components, will cause electrode stripping, reduce the reliability, so should try to choose a small degree of bending plate, and FR4 substrate material is a good choice.

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

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

(2) high heat resistance, general requirements can have 250℃ / 50S heat resistance.

(3) good flatness, SMT requirements as far as possible to use a small degree of bending plate, warping requirements "0.0075mm/mm.

(4) Low coefficient of thermal expansion (CTE), due to X, Y and thickness direction of the thermal expansion coefficient is not consistent, easy to cause PCB deformation, serious will cause metallized hole fracture, resulting in damage to components.

(5) Electrical performance, high frequency circuit requirements to select high dielectric constant, dielectric loss of small material, insulation resistance, voltage resistance, arc resistance performance must meet the product requirements.