Because the exposure machines used in various manufacturers used in the membrane are different, that is, the power and lights of the light source, the power and light distance of the lights, it is difficult for dry membrane manufacturers to recommend a fixed exposure time. Companies that produce dry membranes abroad have their own or recommended light density ruler. When the dry membrane is exported to the factory, the recommended imaging levels are marked. my country's dry film manufacturers do not have their own light density. Like ISTON) level 17 or Stouffer (Stouffer) level 21 light density ruler.

The light density of the 17 -level light density of Ryston is 0.5, and then the light density AD is increased by 0.05 per level, and the light density of level 17 is 1.30. The light density of the 2L -level light density of Steci 2L is 0.05. In the future, the density difference △ D is increased by 0.15 per level. When exposing the light density ruler, the light density (that is, the more transparent) level, the ultraviolet light energy received by the dry membrane is more energy, the aggregation is complete, and the level of light density (that is, the poor degree of transparency), dry dry, dry The energy received by the membrane is less energy, and there is no incomplete aggregation or polymerization. It is manifested or left only part of the time. In this way, different times can be used for exposure to get different imaging levels.

Introduction to the use of Ryston's 17 -level light density ruler as follows:

a. Pharmacular membrane down when exposed;

b. Put 15 minutes after the film on the copper foil plate and expose it;

c. Place for 30 minutes after exposure. Any selection time is used as the reference exposure time. It is expressed by TN. The number left after the development is called the reference level. The recommended use level is compared with the reference level, and the calculation is calculated according to the following coefficient table.