PCB dry film hole puncture when used to improve the way problems
With the rapid development of the electronics industry, PCB layout more and more sophisticated, most PCB manufacturers use dry film to complete the transfer of graphics, the use of dry film is also more and more popular, but I am in the process of after-sales service, still encountered a lot Customers use dry film when there are many errors, are summed up in order to learn.
First, dry film hole hole appears broken
Many customers believe that the emergence of holes, the film should be increased temperature and pressure to enhance its binding force, in fact, this view is not correct, because the temperature and pressure is too high, the solvent resist excessive evaporation, so dry Film become brittle and thinner, easy to be punched when developing, we always have to maintain the toughness of the dry film, so after the hole breaks, we can make improvements from the following points:
1, reduce foil temperature and pressure
2, improve drilling holes
3, improve exposure energy
4, reduce development pressure
5, post-filming time can not be too long, so as to avoid the corner of the semi-fluid-like film diffusion under the action of the pressure thinning
6, filming process dry film do not get too tight
Second, dry plating occurs when plating
The reason why the infiltration plating, indicating that the dry film and the copper clad plate bond is not strong, so that the bath in-depth, resulting in “negative phase” part of the coating thickening, the majority of PCB manufacturers occur infiltration are caused by the following:
1, high or low exposure energy
Under ultraviolet light, the photoinitiator that absorbs the light energy is decomposed into radical-initiated monomers for photopolymerization to form a body-type molecule that is insoluble in a dilute alkali solution. Exposure is not enough, due to incomplete polymerization, in the development process, the film swelling becomes soft, resulting in lines are not clear or even the film off, resulting in poor film and copper bonding; if the exposure will cause difficult to develop, but also in the plating process In the resulting Alice peeling, the formation of infiltration. So controlling the exposure energy is very important.
2, foil temperature is high or low
If the film temperature is too low, the resist film is not fully softened and properly flowed, leading to poor adhesion of the dry film to the surface of the copper clad laminate; if the temperature is too high due to the solvent and other volatility in the resist Rapid volatilization of substances and the formation of bubbles, and dry film becomes brittle, forming electrosurgical peel Alice peeling, resulting in infiltration.
3, foil pressure is high or low
Foil pressure is too low, it may result in uneven film surface or dry film and the gap between the copper plate to meet the requirements of the bonding force; foil pressure is too high, the resist layer of volatile solvents and volatile too much material, resulting in Dry film brittle, electroplated shock will peel off.