The reason for the plating, it shows that the dry film and copper foil plate bonding is not strong, so that the plating solution deep, resulting in the “negative phase” part of the coating thickening, most PCB manufacturers are caused by the following reasons:
1. High or low exposure energy
Under ultraviolet light, the photoinitiator, which absorbs the light energy, breaks down into free radicals to initiate the photopolymerization of monomers, forming body molecules insoluble in dilute alkali solution.
Under exposure, due to incomplete polymerization, during the development process, the film swelling and softening, resulting in unclear lines and even film layer off, resulting in poor combination of film and copper;
If the exposure is too much, it will cause development difficulties, but also in the electroplating process will produce warped peel, the formation of plating.
So it’s important to control the exposure energy.
2. High or low film pressure
When the film pressure is too low, the film surface may be uneven or the gap between the dry film and the copper plate may not meet the requirements of the binding force;
If the film pressure is too high, the solvent and volatile components of the corrosion resistance layer too much volatile, resulting in the dry film become brittle, electroplating shock will become the peeling.
3. High or low film temperature
If the film temperature is too low, because the corrosion resistance film can not be fully softened and appropriate flow, resulting in the dry film and copper-clad laminate surface adhesion is poor;
If the temperature is too high due to the rapid evaporation of solvent and other volatile substances in the corrosion resistance bubble, and the dry film becomes brittle, in the electroplating shock formation of warping peel, resulting in percolation.