Precautions for PCB CCL Selection

In PCB manufacturing, the choice of substrate material is particularly important, and the properties of different boards are also different, such as thermal expansion, heat resistance coefficient, flatness and other factors will affect the performance of the entire board. 

What factors should be paid attention to when choosing substrate materials?

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

For general electronic products, generally select FR-4. It is not a material name, but a material grade. It represents a material specification that the resin material must be able to self-extinguish after being burned. At present, there are many types of FR-4 grade materials used in circuit boards, but most of them are composites made of so-called Tera-Function epoxy resin, plus filler and glass fiber. 

The composites have 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 electrode to peel off and reduce the reliability. Therefore, you should try to choose a plate with a small degree of bending, and FR-4 is a good choice.

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

(1) Appropriately select substrates with a higher glass transition temperature (TG), and the TG should be higher than the circuit operating temperature.

(2) High heat resistance

It generally requires a heat resistance of 250°C/50S.

(3) Good flatness

In SMT, it is required to use PCB with a small degree of wrap and twist as much as possible, and the warping degree is required to be less than 0.0075mm/㎡.

(4) Low coefficient of thermal expansion (CTE)

Due to the inconsistency of the coefficient of thermal expansion in the X, Y direction and thickness, it is easy to cause PCB deformation. In severe cases, it will cause the plated through hole to break and cause damage to the components.

(5) Electrical performance

In high-frequency circuits, it requires selecting materials with high dielectric constant and low dielectric loss. The insulation resistance, voltage strength, and arc resistance must meet the product requirements.

After knowing about the above-mentioned elements of substrate selection, We believe that it will save a lot of effort when selecting PCB substrate materials.