Reasons in damage or penetration of dry film of pcb board and its improvement

The wiring of the PCB board is very precise, and many PCB manufacturers use the dry film process to transfer the circuit pattern. Below, I will explain in detail the reasons for the damage or penetration of the dry film of the pcb board and its improvement.

1. There is a hole in the dry film when the hole is masked

(1)Reduce the film temperature and pressure;

(2)Improve the roughness of the hole wall and the drape;

(3) Increase the exposure energy;

(4)Reduce the pressure of developing;

(5)Do not park for too long after the film is applied, so as not to cause the semi-fluid film to diffuse and thin at the corners;

(6)When sticking the film, the dry film we use should not be stretched too tightly.

2. Infiltration plating occurs during dry film electroplating, indicating that the dry film and copper foil are not firmly adhered, so that the electroplating solution enters. The occurrence of seepage plating is caused by the following bad reasons:

(1) The temperature of the film is too high or too low

If the temperature is too low, the resist film will not be fully softened and flowed, resulting in poor adhesion between the dry film and the surface of the copper-clad laminate; if the temperature is too high, the solvent in the resist will volatilize rapidly to generate bubbles, and the dry film will become It is brittle, and it forms lift-off and peeling during electroplating electric shock, resulting in bleed plating.

(2) The film pressure is too high or too low

If the pressure is too low, the surface of the film will be uneven or there will be a gap between the dry film and the copper plate, which will not meet the requirements of the bonding force; if the pressure is too high, the solvent of the resist layer will evaporate too much, causing the dry film to become brittle, and it will become brittle after electroplating. Will lift off.

(3) The exposure energy is too high or too low

When the exposure is insufficient, due to incomplete polymerization, the film swells and softens during the development process, resulting in unclear lines or even the film layer falling off; Infiltration plating.