With the rapid development of the electronics industry, PCB wiring is becoming more and more precise. Most PCB manufacturers use dry film to complete graphic transfer, and the use of dry film is also becoming increasingly popular. However, many customers still encounter many misunderstandings when using dry film. This is a summary for reference.
1、 Dry film mask with perforation
Many customers believe that after a hole is broken, the film temperature and pressure should be increased to enhance its adhesion. However, this view is incorrect because when the temperature and pressure are too high, the solvent in the corrosion resistant layer evaporates excessively, making the dry film brittle and thin. During development, the hole is easily broken, and we always need to maintain the toughness of the dry film. Therefore, after a hole is broken, we can improve it from the following points:
1. Reduce film temperature and pressure
2. Improve the drilling front
3. Increase exposure energy
4. Reduce development pressure
5. The parking time after applying the film should not be too long to avoid causing the semi fluid like drug film at the corner to diffuse and thin under pressure
6. Do not tension the dry film too tightly during the film application process
2、 Penetration occurs during dry film electroplating
The reason for infiltration plating is that the dry film and copper clad foil are not firmly bonded, causing the plating solution to penetrate deeply and causing the "negative phase" part of the coating to become thicker. Most PCB manufacturers experience infiltration plating due to the following reasons:
1. Exposure energy is too high or too low
Under ultraviolet light irradiation, the photoinitiator that absorbs light energy decomposes into free radicals to initiate monomer photopolymerization reactions, forming body shaped molecules that are insoluble in dilute alkali solutions. When the exposure is insufficient, due to incomplete polymerization, the adhesive film swells and softens during the development process, resulting in unclear lines and even detachment of the film layer, resulting in poor adhesion between the film and copper; If the exposure is excessive, it will cause difficulty in development and also cause warping and peeling during the electroplating process, forming infiltration plating. So controlling the exposure energy is very important.
2. The film temperature is too high or too low
If the film temperature is too low, due to insufficient softening and proper flow of the anti-corrosion film, the adhesion between the dry film and the surface of the copper clad laminate is poor; If the temperature is too high, bubbles will be generated due to the rapid evaporation of solvents and other volatile substances in the corrosion inhibitor, and the dry film will become brittle, forming warping and peeling during electroplating electric shock, resulting in infiltration plating.
3. The film pressure is too high or too low
When the film pressure is too low, it may cause uneven film surface or gaps between the dry film and the copper plate, which may not meet the requirements of adhesion; If the film pressure is too high, the solvent and volatile components in the anti-corrosion layer will evaporate too much, causing the dry film to become brittle, and it will warp and peel off after electroplating electric shock.