What are the common related parameters of PCB multilayer wiring board quality assessment?

The design of qualified PCB boards has very large requirements for the quality of PCBA processing.

 So, what are the common parameters of PCB multilayer circuit board quality assessment?

To evaluate the quality of PCB board, T g, CTE, T d, heat resistance to heating, electric property and PCB water absorption are commonly used. Below, 

let us explain for you the glass transition temperature and thermal expansion coefficient:

I. Glass transition temperature (Tg value)

Under a certain temperature, the substrate is hard and brittle, called glass: above this temperature, 

the base softens, and the mechanical strength becomes significantly lower. 

This critical temperature that determines the properties of a material is called vitrification transition temperature.

Tg temperature is too low, high temperature will make the PCB deformation, damage components.

II. Coefficient of Thermal Expansion (CTE)

CTE quantitatively describes the extent to which a material expands when heated. 

CTE refers to the length of the unit length of the material for every 1C increase in ambient temperature. 

Due to the high welding temperature, the PCB board is required to have a lower thermal expansion coefficient. 

Especially for multilayer PCB circuit board, the CTE in Z direction has a great influence on the layer bonding resistance of the holes. 

Especially when welding or refurbishing more than once, after many expansions and contractions, it will cause the metalized pore to break.