Dry film mask technology production process

cutting inner layer  → film laminating inner layer →  exposure inner layer → developing inner layer → etching inner layer → film stripping → inner layer black oxidation →   multilayer lamination → drilling  → PTH  → panel plating → outer layer dry film laminating → outer layer exposure (negative film)  → outer layer developing  →  outer layer etching (acid etching)→  outer layer film stripping  → silk screen solder mask printing → solder mask exposure → solder mask developing → post curing → HASL or ENIG  → legend printing  → testing → routing→ finish product cleaning → packing → finish products

Disadvantages: high requirements for the environmental of dry film laminating and exposure room (must cleaning environment), but short process, not need pattern plating, tin plating, Tin stripping.

Advantages: it has high manufacturing precision and neat edges, process easy to control. It is suitable for the production of PCB boards with high precision requirements, such as double-sided boards, multilayer boards and high-frequency PCB, HDI with dense circuit in small batches and varieties. Moreover, it uses less water and is easy to control, which is very conducive to environmental protection.

Summary: high circuit precision, fast production and environmental protection are required. Dry film mask process is we recommend. The product batch is large, and the requirements for line accuracy are not high.

Customer question:

In the process (Dry film mask technology method), Some holes, especially those whose sizes are larger than 2 mm, 4 mm or 5 mm, are open and not covered by the dry film. During the acid etching process, copper is removed from inside these holes and cause (open hole ).

Our engineers answers:

First,

The water in the holes should be dried completely after brushing. After brushing, make sure there is no water in the plate and hole before dry film laminating, which is very important.

Second,

Before dry film laminating, it is best to bake the board and then laminate the dry film. The board should be laminated at a certain temperature, it is better heat the board.

Third,

We should control the speed, temperature and pressure of dry film laminating. The film application speed should not be too fast. It should be about 0.8m per minute and the temperature should not be lower than 105 degrees.

Fourth,

Choose a better dry film, should not too thin. Use a thicker dry film.  Recommended to use HT115 dry film.

Fifth,

We should also control the exposure strength. If the exposure is not enough, it will be easy to open holes.  If we check with 21  exposure ruler, the exposure volume should higher than 8 level when covered the photosensitive film.