The viscosity of liquid photosensitive solder mask ink is mainly controlled by the ratio of hardener to main agent and the amount of diluent added. If the amount of hardener added is not enough, it may cause an imbalance in ink characteristics. After the hardener is mixed, it will react at room temperature, and its viscosity changes as follows.

　　Within 30 minutes: The main ink agent and hardener have not yet fully integrated, resulting in insufficient fluidity and clogging of the screen during printing.

　　30 minutes to 10 hours: The ink main agent and hardener have been fully integrated, and the fluidity is appropriate.

　　After 10 hours, the reactions between the various materials of the ink itself continue to take place proactively, resulting in increased fluidity and difficulty in printing. The longer the hardener is mixed, the more complete the reaction between the resin and hardener, and as a result, the gloss of the ink also improves. To ensure even ink gloss and good printability, it is best to leave the hardener mixed for 30 minutes before starting printing.

　　If too much diluent is added, it will affect the heat resistance and hardening of the ink. In short, the viscosity adjustment of liquid photosensitive solder mask ink is very important: viscosity is too thick, making screen printing difficult. Easy to stick mesh on the screen; The viscosity is too thin, and there is a high amount of volatile solvent in the ink, which makes it difficult to pre cure.

　　The viscosity of ink is measured using a rotary viscometer. In production, it is necessary to adjust the optimal viscosity according to different inks and solvents.