Graphics transfer mask

Colloids with dichromate as a sensitizer

Masks with dichromate as the sensitizer were all shellac, bone glue, gelatin and polyvinyl alcohol as colloids. After the dichromate is added to the colloid, it becomes photosensitive adhesive (coated on the surface of the board to form a mask), and is coated, dried, exposed, and developed to produce a pattern. Dichromate reacts chemically in colloids upon exposure to ultraviolet light. The photosensitive part forms Cr3+ and forms a water-insoluble part of the colloidal protein with hexavalent chromium as the photosensitive colloid. After development, it is washed away by water and contains six parts in the waste water. Chromium contaminates water sources and the environment. After entering the 1980s, this process was gradually eliminated.

Anti-corrosion ink

This mask has been continuously improved over a long period of time, and its use performance and corrosion resistance have greatly improved. Initially, this type of ink was prepared by the user himself, because of the different sources of materials and the imperfect equipment, and the quality was not very stable. Later, with the production of anti-corrosion inks by professional manufacturers, the quality has changed. However, large amounts of solvents are required during production, which not only increases costs but also causes air pollution. The use of UV-cured or heat-cured ink with a weak base to remove the film is more convenient, but it is printed on the surface of the plate through the screen, limiting its resolution. It is difficult to operate when the line width and line size are below 0.2mm. In other words, it can only be used for thick lines and general lines in graphics. The operator's technical requirements are high during manual operation and the repeatability is not good.

Dry film resist

Dry film resist, commonly known as dry film, entered China in the early 1970s and is the most widely used mask for circuit board manufacturing. The application of dry film has created a new chapter for the graphic transfer process of China's circuit boards, which has accelerated the development of circuit board industry. Dry film manufacturing technology has certain difficulties, and equipment and testing equipment investment is relatively large, only a few domestic manufacturers, the quality can only meet the needs of general products. Dry film accounts for a considerable proportion of circuit board manufacturing costs. Most domestic dry film needs to be imported, and the imported brands, thicknesses, and specifications continue to increase. At present, the price of the circuit board has dropped again and again, and many manufacturers have to explore other ways to reduce costs. The dry film needs special equipment. If it is not the system production or automatic production, the side materials will be more and waste. The waste generated during production needs to be processed. These are manufacturers' considerations. Therefore, there is a need to seek a new type of photosensitive mask material instead of a dry film.

Reprinted from: "China Chemical News"