Views:25 Author:Site Editor Publish Time: 2020-08-03 Origin:Site
PCB generally consists of four layers, which are heat laminated together into a single layer. The material used in PCB from top to bottom includes Silkscreen, Soldermask, Copper and Substrate.
The massively-used copper clad laminate (CCL) can be classified into different categories according to different classification standards including reinforcing material, used resin adhesive, flammability, CCL performance. The brief classification of CCL is shown in the following table.
Table: Classification of CCL
Paper base class
PF resin (XPC, FR1, FR2)
Epoxy resin (FE-3)
Glass fiber cloth base class
Epoxy resin (FR4, FR5)
Composite epoxy material (CEM)
Lamination multilayer base class
Special material base class
BT, PI, PPO, MS
CCL with ordinary performance
CCL with low dielectric constant
CCL with high heat resistance
CCL with low coefficient of thermal expansion
Above the green solder-mask is the silkscreen layer, which adds letters and numerical indicators that make a PCB readable to tech programmers. This, in turn, makes it easier for electronics assemblers to place each PCB in the proper place and in the right direction on each component. The silkscreen layer is usually white, though colors such as red, yellow, gray and black are also sometimes used.