PCB News - PCB dry film appear hole, infiltration plating how to do

With the rapid development of the electronics industry, PCB wiring is becoming more and more precise. Most PCB manufacturers use dry film to complete the graphic transfer, and the use of dry film is becoming more and more popular. However, many customers still make mistakes when using dry film.

First, dry film mask holes appear

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, reduce the film temperature and pressure

2, improve drilling drape front

3, improve exposure energy

4, reduce developing pressure

5, the parking time after the film can not be too long, so as not to lead to the corner part of the semi-fluid film under the action of pressure diffusion thinning

6, do not stretch the dry film too tight in the film process

Two, dry film plating occurs infiltration

The reason for infiltration plating is that the dry film and copper-clad foil are not firmly bonded, which deepens the plating solution and thickens the "negative phase" part of the coating. Infiltration plating occurs in most PCB manufacturers due to the following reasons:

1, High or low exposure energy

Under ultraviolet light, the photoinitiator that absorbs the light energy is decomposed into free radical to initiate the monomer to photopolymerization reaction, forming the body molecule insoluble in dilute alkali solution. When the exposure is insufficient, due to incomplete polymerization, in the developing process, the film swelling becomes soft, resulting in unclear lines and even the film layer falls off, resulting in poor combination of the film and copper; If the exposure is excessive, it will cause difficulty in developing, and it will also produce warping and stripping in the plating process, forming infiltration plating. So it's important to control the exposure energy.

2, the film temperature is high or low

If the film temperature is too low, due to the corrosion resistance film can not get sufficient softening and appropriate flow, resulting in poor adhesion between dry film and copper clad laminate surface; If the temperature is too high due to the rapid volatilization of solvent and other volatile substances in the resist and bubbles, and the dry film becomes brittle, forming warping peel when electroplating electric shock, resulting in infiltration plating.

3, the film pressure is high or low

When the film pressure is too low, it may cause uneven film surface or gap between dry film and copper plate and not meet the requirements of binding force; If the film pressure is too high, the solvent and volatile components of the anticorrosive layer are too volatile, resulting in brittle dry film, which will become warped after electroplating shock.