PCB layer deviation phenomenon main influencing factors
With the development of high-level and high-precision PCB boards, the accuracy of the alignment between layers has become more stringent, and the PCB board skew problem has become more serious. There are many reasons for the PCB layer bias. Now we share with you the main influencing factors of the layer deviation phenomenon.
Definition of PCB layer bias:
Tier bias refers to the difference in concentricity between layers of PCB board that originally requires alignment. The scope of requirements is regulated according to the design requirements of different PCB types. The smaller the hole-to-copper spacing, the stricter the control is to ensure its ability to conduct and over-current.
Commonly methods for detecting layer deviations in the production process:
The current method commonly used in the industry is to add a group of concentric circles at each corner of the production board, and set the spacing between concentric circles according to the requirements of the production board, and pass the X-Ray inspection machine or X-Ray tools in the production process. The target checks the degree of concentricity to confirm its bias.
According to the level of layer deviation and the process of layer deviation, the layer deviation can be mainly divided into inner layer deviation and pressure layer deviation ( the following table attached ); PCB layer deviation classification:
PCB board bias:
Analysis of PCB layer deviation causes:
1. The inner layer
The inner layer is mainly the process of transferring the graphics from the film to the inner core board, so the layer bias will only be generated during the process of the graphics transfer production. The main reasons for the layer bias are: the inner film is inconsistent and the exposure mechanism is uneven Misalignment, improper handling of personnel during the exposure process, and other factors.
2. PCB board pressure layer bias reason
The main reasons for layer compression are: inconsistency in the rise and shrinkage of the core plates in each layer, poor positioning of the punching holes, misalignment of the welding positions, misalignment of the rivets, and sliding of the press plate during the press-fitting process.