⑴ Differences in longitude and latitude directions cause changes in substrate size; Due to the lack of attention to fiber direction during shearing, shear stress remains in the substrate, and once released, it directly affects the shrinkage of the substrate size.

The copper foil on the surface of the substrate is etched off, which limits the variation of the substrate and results in dimensional changes when stress is relieved.

When brushing the board, excessive pressure is used, resulting in compressive and tensile stresses that cause deformation of the substrate.

The resin in the substrate is not completely cured, resulting in size changes.

Especially for multi-layer boards, poor storage conditions before lamination can cause moisture absorption on thin substrates or semi cured sheets, resulting in poor dimensional stability.

When the multi-layer board is pressed, excessive glue flow causes deformation of the glass cloth.

Solution:

⑴ Determine the variation pattern of longitude and latitude direction and compensate on the film according to the shrinkage rate (this work is carried out before photogrammetry). When cutting at the same time, process according to the fiber direction, or process according to the character markings provided by the manufacturer on the substrate (usually the vertical direction of the characters is the vertical direction of the substrate).

When designing the circuit, efforts should be made to evenly distribute the entire board surface. If it is not possible, it is necessary to leave a transition section in the space (without affecting the circuit position). This is due to the difference in warp and weft yarn density in the glass cloth structure of the board, resulting in differences in the warp and weft strength of the board.

⑶ Trial brushing should be used to ensure that the process parameters are in the optimal state, and then the rigid plate should be carried out. For thin substrates, chemical cleaning or electrolysis processes should be used for cleaning treatment.