Reason:
1 , did not pay attention to the fiber direction , caused by differences in substrate size Jingwei direction changes ; due to shear . Residual shear stress caused in the substrate , once released , shrinkage directly affects the size of the substrate .
Produce dimensional changes when stress relief . The copper foil surface of the circuit substrate is etched on the substrate change limit .
Resulting in compressive tensile stress cause substrate deformation. As a result of the pressure plate when the brush is too big .
Cause dimensional changes . The resin circuit board substrate is not completely cured.
Poor storage conditions , in particular multilayer circuit boards prior to lamination . The thin prepreg substrate or moisture , resulting in poor dimensional stability .
Caused by excessive flow of plastic deformation caused by glass cloth . Multilayer by pressing timely.
Solution:
2 , or by the manufacturer on the substrate to provide a character symbol processing ( generally vertical direction to the longitudinal direction of the character of the substrate ) ⑴ determine the variation of grain direction shrinkage compensated in accordance with the film ( do this before Gerber work ) while shearing press the fiber direction processing.
In the design of the circuit should be as uniform distribution of the entire board . If you can not also have to leave the space transition section ( does not affect the position of the main circuit ) which due to the differences in plate glass cloth structure using warp and weft density, resulting in latitude and longitude to the plate
Differences in intensity. Circuit board so that the process parameters in the best condition, should try to brush . Then just board. Thin circuit board substrate cleaning process when using chemical cleaning process or electrolysis process methods .
Temperature 120 ℃ 4 hours, take baking solutions. Especially before drilling baking . To ensure that the resin was cured , because of the cold reduced , resulting in deformation of the substrate size.
Circuit board must be baked to remove moisture. Deal of the substrate and placed in a vacuum oven , the inner substrate oxidation process. Avoid moisture again.
Adjusting the process parameters and then pressed . Also according to the characteristics of the prepreg , the need for process pressure test .
