Change in substrate size during PCB manufacturing

- Oct 20, 2018-

The reason:

Variation of substrate size due to difference of longitude and latitude directions;Because the fiber direction was not paid attention during shear, the shear stress remained in the substrate. Once released, the size of the substrate was directly affected.

The copper foil on the surface of the metal base plate is etched away.

Due to excessive pressure applied to the roller brush plate, compressive tensile stress is produced, resulting in substrate deformation.

Is in the base plate resin not fully solidified, resulting in size changes.

Poor storage conditions, especially for multilayer plates before lamination, make thin substrate or semi-solidified sheet hygroscopic, resulting in poor dimensional stability.

The excessive glue flow caused the deformation of glass cloth.

Solution:

D. Determine the change of longitude and latitude in accordance with the shrinkage rate on the film compensation (before light painting to do this work).At the same time shear according to the fiber direction processing, or according to the manufacturer on the substrate provided character mark processing (generally the vertical direction of the characters for the substrate).

In the design of the circuit should be as far as possible to make the entire board uniform distribution.If not possible, you must leave an itd in space (not affecting the position of the circuit).This is due to the density of the weft in the glass fabric structure of the plate caused by the latitude and longitude of the difference in strength.

Steel should be used to test brush, so that process parameters in the best state, and then plate.For thin base material, chemical cleaning process or electrolytic process should be adopted when cleaning.

Bake.Especially before drilling for baking, the temperature is 120 ℃ for 4 hours, to ensure that the resin curing, reduce because of the effect of heat and cold, lead to deformation of the substrate size.

The inner layer of the oxidized substrate must be baked to remove moisture.The prepared substrate is stored in a vacuum drying box to prevent moisture absorption.

In order to perform the process pressure test, adjust the process parameters and then press.At the same time, the appropriate amount of glue can be selected according to the characteristics of the semi-cured tablets.