15 things that improve accuracy when making screen

 

1. Mesh

 

We are talking about the type of mesh we use, mesh count, fineness of mesh diameter, size of the opening area, expansion and contraction rate, weaving method, and color.

 

2. Screen frame

 

They are material, size and strength.

 

3. Tension

 

4. Angle of mesh

 

5. Bonding method between screen frame and mesh

 

6. Preprocessing for screen

 

7. Squeegee

 

For squeegee, material, width, hardness, scraping angle, blade, screen spacing and scraping pressure are all important. Polyester rubber should be used to make squeegees.

 

The hardness of most squeegees  is within Shore A60-80. The scraping angle is 20-30 degrees. The blade must always be kept flat and sharp. The screen spacing is generally 2-4mm, and the screen is parallel to the table.

 

8. Photosensitive materials

 

We are talking about the sensitivity, resolution, adhesion of photosensitive materials, expansion and contraction rate of photosensitive films, thickness and hardness of photosensitive films, water resistance, solvent resistance, friction resistance and printing resistance.

 

9. The mixing time of photosensitive agent and storage time after mixing

 

10. Drying methods and conditions, drying temperature, humidity and drying time

 

11. light source for making screen, the length of exposure time, the distance of the light source, etc.

 

12. Density of the film

 

13. Development method and development conditions

 

14. Drying temperature and time after development

 

15. Secondary exposure time and retouching

 

Failures & reasons of making screen

 

1. The photosensitive film is lost during development.

 

(a) Insufficient exposure

(b) Insufficient or ineffective dose of photosensitive agent, resulting in reduced sensitivity.

 

2. The pattern has a light gray cast.

 

(a) The workplace for the photosensitive liquid coating and drying process is too bright.

(b) The exposure time is insufficient, and the development is insufficient.

(c) Part of the photosensitive liquid is overheated during coating and drying.

(d) The exposure time is too long.

 

3. The fine part of the pattern is not developed.

 

(a) The exposure time is too long.

(b) The positive film is reversed. The positive film and the photosensitive film are not well matched.

(c) The screen pre-treatment is not sufficient.

(d) The photosensitive film is too thick, and the type of photosensitive adhesive is not selected properly, or the photosensitive adhesive is ineffective.

 

4. So many bubbles on screen after coating

 

(a) The screen is not degreased enough.

(b) The screen is cleaned before coating the photosensitive adhesive.

(c) The temperature difference between screen drying and the photosensitive adhesive is large during coating.

(d) The storage temperature of photosensitive adhesive is too high.

(e) The photosensitive adhesive and coating layer are too thin.

(f) The coating speed is uneven.

 

5. Too many pinholes on the screen.

 

(a) Dust.

(b) Bubbles in photosensitive liquid.

(c) When squeegee is moving, if it is too fast, bubbles and pinholes will happen.

(d) Adding too much photosensitive agent will also cause pinholes.

(e) The coating surface is easy to fall on dust, so the workplace must be kept clean.

(f) A small amount of octanol can be added to the photosensitive liquid as a defoaming agent.

 

6. Obvious pores on the screen after development.

 

(a) drying at high temperature after development.

(b) Photosensitive agent with a long shelf life.

(c) Dust in photosensitive resin.

(d) The exposure time is not appropriate.