Solution to the problem of perforation/infiltration during PCB dry film operation

- Nov 03, 2018-

With the rapid development of the electronics industry, PCB wiring is becoming more and more sophisticated. Most PCB manufacturers use dry film for graphic transfer, and the use of dry film is becoming more and more popular.

1. The dry film mask is broken

Many clients think, after a broken hole, should increase film temperature and pressure, and to enhance their binding force, actually this kind of view is incorrect, because after high temperature and pressure, corrosion resistant layer of excessive solvent volatilization, make the dry film brittle thin and vulnerable to break through the hole when developing, we always want to keep dry film toughness, so, after a broken hole, we can do it from the following points to improve:

1. Lower film temperature and pressure

2. Improve the bore front

3. Increase the exposure energy

4. Reduce developing pressure

5. Stop for a long time after the film is applied, so as not to cause the semiliquid drug film at the corner to diffuse and thin under pressure

6. Do not stretch the dry film too tightly during the film patch

2. Percolation occurred during dry film plating

The reason for the percolation plating is that the poor bond between the dry film and the coated copper foil plate makes the plating solution deep and causes the "negative phase" part of the plating layer to become thick. Most PCB manufacturers are caused by the following factors:

1. High or low exposure energy

Under the irradiation of ultraviolet light, the photoinitiator which absorbs the light energy is decomposed into free radicals and monomers are induced to conduct the photopolymerization reaction to form the body molecule which is insoluble in dilute alkali solution.In the case of insufficient exposure, due to incomplete polymerization, the film will swell and become soft during development, resulting in unclear lines and even peeling of the film, resulting in poor bonding between the film and copper.If the exposure is excessive, it will be difficult to develop, and will also be produced in the electroplating process of the warp peel, forming a percolation.So it's important to control your exposure energy.

2. The film temperature is high or low

If the film temperature is too low, the surface adhesion between the dry film and the copper foil laminate is poor due to insufficient softening and proper flow of the anti-corrosion film.If the temperature is too high, air bubbles will be generated due to the rapid volatilization of solvent and other volatile substances in the corrosion inhibitor, and the dry film will become brittle and become warped and detached when electroplating, resulting in the percolation.

3. High or low film pressure

If 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 requirement of binding force.If the film pressure is too high, the anti-corrosion layer of the solvent and volatile components are too much volatilization, resulting in a brittle dry film, electroplating after the shock will be up.