(1) Pre drying

　　The purpose of pre drying is to evaporate the solvent contained in the ink and make the solder mask non stick. The pre drying temperature and time vary depending on the type of ink. Excessive pre drying temperature or prolonged drying time can lead to poor development and reduced resolution; If the pre drying time is too short or the temperature is too low, the film will adhere during exposure. During development, the solder mask film will be corroded by sodium carbonate solution, causing the surface to lose luster or the solder mask film to expand and fall off.

　　(2) Exposure

　　Exposure is the key to the entire process. For positive images, when overexposed, due to light scattering, the solder mask at the edges of the pattern or line reacts with light (mainly the photosensitive polymers contained in the solder mask react with light), generating residual film and reducing the resolution, resulting in a smaller developed pattern and thinner lines; If exposed

　　When insufficient, the result is opposite to the above situation, where the developed shape becomes larger and the lines become thicker. This situation can be reflected through testing: for long exposure times, the measured linewidth has a negative tolerance; For short exposure times, the measured linewidth is within a positive tolerance. In the actual process, a "light energy integrator" can be used to determine the optimal exposure time.