Printed circuit manufacturers all hope to choose good performance of dry film, to ensure the quality of printed board, stable production, improve efficiency. In recent years, with the rapid development of electronic industry, the precision density of printed board has been improved. In order to meet the needs of printed board production, new dry film products have been introduced continuously, and the performance and quality have been greatly improved and improved. Dry film film, first peeled from the dry film polyethylene protective film, and then under the condition of heating and pressurizing dry film corrosion inhibitor pasted on the copper clad foil board. The resist layer in the dry film becomes soft after being heated, and the fluidity increases. The film is finished by means of the pressure of the hot press roll and the action of the binder in the resist. The film is usually completed on the film machine, the film model is various, but the basic structure is roughly the same, the general film can be continuous paste, can also be single paste.

When continuous film coating, pay attention to the alignment of dry film on the upper and lower dry film feeding roller. Generally, the size of the film should be slightly smaller than the surface of the plate to prevent corrosion inhibitor sticking to the hot pressing roller. Continuous film production efficiency is high, suitable for mass production. When the film should master the three elements of pressure, temperature, transmission speed. Pressure: the newly installed film laminating machine, first of all, the upper and lower hot pressing roller to the axial parallel, and then to use the method of gradually increasing pressure pressure adjustment, according to the printed board thickness adjustment to make the dry film easy to stick, stick firmly, not wrinkle. General pressure adjustment can be fixed after use, such as the production of circuit board thickness difference is too large to adjust, the general line pressure is 0.5-0.6kg/cm. Temperature: according to the type of dry film, performance, environmental temperature and humidity are slightly different, if the film coating is dry and the environmental temperature is low humidity, the film temperature is higher, on the contrary, it can be lower, the good stable environment in the darkroom and intact equipment is a good guarantee of the film.

Generally, if the film temperature is too high, the dry film image will become brittle, resulting in poor plating resistance, the film temperature is too low, the dry film and copper surface adhesion is not strong, in the development or plating process, the film is easy to become warped or even fall off. Usually control the film temperature at about 100℃. Transmission speed: related to the film temperature, high temperature, transmission speed can be faster, low temperature will be slow transmission speed. The usual transmission speed is 0.9-1.8 m/min.

In order to adapt to the production of printed boards with fine wires, a wet film laminating process is developed. This process uses a special film laminating machine to form a layer of water film on the surface of copper foil before sticking dry film. The function of the water film is to improve the fluidity of dry film; Remove residual bubbles on scratches, sand holes, pits and fabric pits; In the process of heating and pressure coating, water can increase the adhesion of photoresist, which can greatly improve the adhesion between dry film and substrate, and thus improve the qualified rate of fine wires. It is reported that the qualified rate of fine wires can be increased by 1-9% using this process.

Photosensitivity includes photosensitivity speed, exposure time tolerance and depth exposure. Photosensitive speed refers to the amount of light energy required by photopolymerization monomer to form polymer with certain corrosion resistance under uv irradiation. In the case of fixed light source intensity and lamp distance, photosensitive speed is represented by the length of exposure time, short exposure time means fast photosensitive speed. In order to improve production efficiency and ensure the precision of printed board, dry film with fast photosensitive speed should be selected.

Dry film exposure after a period of time, after development, the photoresist layer has all or most of the polymerization, generally speaking, the formation of the image can be used, the time is called the minimum exposure time. The exposure time continues to be extended to make the polymerization of photoresist more thoroughly, and the size of the image obtained after development is still consistent with the size of the background image, this time is called Max exposure time. Usually a very good exposure time for dry film is between the minimum exposure time and the Max exposure time. The ratio of Max exposure time to minimum exposure time is called exposure time tolerance.

The depth exposure of dry film is important. During exposure, light energy is reduced by passing through the resist layer and scattering effects. If the transmittance of the resist layer to light is not good, when the resist layer is thick, if the exposure of the upper layer is appropriate, the lower layer may not react, and the edge of the resist layer is not neat after development, which will affect the accuracy and resolution of the image. In serious cases, the resist layer is prone to warp and fall off. In order for the lower layer to converge, the exposure must be increased, and the upper layer may be overexposed. Printing ink dry film manufacturer

Dry film development refers to the dry film according to the best working state of film, exposure and development obtained after the image effect is good or bad, that is, the circuit image should be clear, unexposed part should be removed clean no residual glue. The anticorrosion layer left on the board after exposure should be smooth and firm. The developing resistance of dry film refers to the degree of developing resistance of exposed dry film, that is, the developing time can be exceeded. The developing resistance reflects the tolerance of developing process. The developability and developability of dry film directly affect the quality of printed board. Poor dry film development will bring difficulties to etching, in graphic electroplating process, poor development will produce defects such as not plating or poor adhesion of coating. Dry film development resistance is poor, in excessive development, dry film will fall off and plating infiltration and other problems. These serious defects can lead to the abandonment of the printed board.

The so-called resolution refers to the number of lines or distances formed by dry film resist within the distance of 1mm. The resolution can also be expressed by the size of lines or distances JUE. The resolution of dry film depends on the thickness of resist film and polyester film. The thicker the resist film, the lower the resolution. Light through the photographic substrate and polyester film to dry film exposure, due to the scattering of polyester film on the light, so that the light side, thus reducing the resolution of the dry film, polyester film thicker, the more serious the light side, the lower the resolution. Usually can distinguish the smallest parallel line width, primary index < 0.1mm, secondary index ≤ 0.15mm.

The dry film corrosion resistant layer after photopolymerization should be able to withstand the etching of ferric chloride, ammonium persulfate, acid copper chloride, sulfuric acid - hydrogen peroxide etching solution. In the etching solution, when the temperature is 50-55 ℃, the dry film surface should not hair, leakage, warping and shedding phenomenon.

In acid bright copper plating, fluoroborate common tin-lead alloy, fluoroborate bright tin-lead alloy and various plating pretreatment solutions mentioned above, the polymerized film resist layer should have no surface hair, infiltration, warping and peeling phenomenon. The dry film after exposure, after etching and electroplating, can be removed in a strong alkali solution, generally using 3-5 % sodium hydroxide solution, heating to 60℃ or so, by mechanical spray or immersion removal, the faster the film removal rate is conducive to improving production efficiency. The form of film removal is flake stripping, and the stripped fragments are removed by the filter, which is not only conducive to the service life of the film removal solution, but also can reduce the blockage of the nozzle. Usually in 3-5 % (weight ratio) sodium hydroxide solution, liquid temperature 60 soil 10℃, the first index is film removal time 30-75 seconds, the second index is film removal time 60-150 seconds, no residual glue after film removal.

Dry film may become brittle due to the volatilization of solvent in the storage process, may also produce thermal polymerization due to the influence of ambient temperature, or due to the local flow of corrosion inhibitor resulting in uneven thickness, namely the so-called cold flow, which seriously affect the use of dry film. Therefore, it is important to store dry film in a good environment. Dry film should be stored in a cool and clean room to prevent storage with chemicals and radioactive substances. Storage conditions: yellow light area, temperature below 27℃ (5-21 ℃ is suitable), relative humidity about 50%. The storage period shall be no more than six months from the date of leaving the factory. Those who pass the inspection after the storage period can still be used. Avoid moisture, heat, mechanical damage and direct sunlight during storage and transportation.

In order to avoid missing exposure and reexposure during production operations, the color of the dry film should change significantly before and after exposure, which is the color change performance of the dry film. When the film is used as a mask etching, the dry film is required to be flexible enough to withstand the impact of liquid pressure in the developing process and etching process without rupture, which is the masking performance of the dry film.