label: Printed circuit manufacturers,PCB production
Printed circuit manufacturers all want a good selection of dry performance to ensure PCB quality, stable production and improve efficiency. In recent years, with the rapid development of the electronics industry, the continuous improvement of the accuracy of the density PCB, PCB production to meet the needs of dry constantly launch new products, performance and quality has been greatly improved and enhanced.
The dry film, the dry film to start a polyethylene protective film peeled off, and then heated and pressurized under the conditions of the dry film resist is attached to the copper-clad board. The dry film resist layer was heated to soften, increased mobility, by means of pressure and the resist roller pressing the film adhesive to complete the action. Foil is usually completed in the film machine, film machine model range, but the basic structure is substantially the same, generally continuous film paste, can also be a single post.
Note when the continuous foil, the dry film to align the feed roller coat dry, generally the size of film to be slightly smaller than the plate surface, to prevent sticking to the resist roller pressing. Continuous film of high production efficiency, suitable for mass production. When the three elements of the film is good for use as pressure, temperature, transmission speed. Pressure: newly installed film machine, first of all to the upper and lower pressing rollers adjusted axially parallel, and then gradually increase the pressure to use the approach to pressure adjustment, adjusted according to the thickness of the printed circuit board so dry and easy to paste, paste prison , no wrinkles. General pressure can be adjusted after fixation, such as the production of circuit boards need to adjust the thickness difference is too large, the general line pressure of 0.5-0.6 kg / cm. Temperature: Depending on the type of dry film, performance, ambient temperature and humidity slightly different than the dry film coating if the ambient temperature and low humidity hours, the film temperature is higher, and vice versa may be lower, good stability in the darkroom environmental and equipment in good condition to ensure good foil.
If the film temperature is generally too high, then the image will become brittle dry, resulting in poor performance resistant coating, foil temperature is too low, dry copper surface adhesion is not strong in developing or electroplating process, the film easily warped or even fall off. Glass temperature is usually controlled at about 100 ℃. Transmission speed: the film temperature, high temperature, faster transmission speeds, low temperature will slow the transmission speed. Usually a transmission rate of 0.9 1.8 m / min.
In order to adapt the production of fine wire PCB, and the development of the wet film technology, this process is the use of a dedicated film machine before the formation of a water film on the paste dry copper surface, the role of the water film is: to improve the dry extermination scratches on the retention of bubbles, blisters, pits and other parts of the fabric recesses; Fluidity of the film during the heating and pressurizing the water from the light-resist thickening effect, which can greatly improve the dry film and the substrate adhesion, thereby increasing the production of fine wires pass rate, according to reports, the use of this technology can improve the fine line passing rate 1-9%.
Including the photosensitive film speed, exposure latitude and depth of the exposure time and the like. Is the speed of the photosensitive photoresist under UV irradiation, the photopolymerizable monomer to form a polymer having a polymerization reaction to produce a corrosion resistance required for the number of light energy. In the light from the light source intensity and fixed, the film speed performance of the length of time of exposure, the exposure time is short photographic speed, from the PCB to improve productivity and ensure the accuracy of considerations should be used in the photosensitive dry film speed .
Dry the exposure period of time, the developed photoresist layer have all or most of the polymerization, the formed image can be generally used, this time is called the minimum exposure time. The longer the exposure time to continue to make the photoresist more thoroughly the polymerization, and the resulting image size remains consistent with the original plate after developing the image size, this is referred to the maximum exposure time. Exposure time is usually the best choice dry in between the minimum and maximum exposure time exposure time. The maximum exposure time and exposure time than the minimum exposure time is called tolerance.
Dry exposure depth is very important. When the exposure light through the resist layer and the energy due to the scattering effect is reduced. If the light transmittance of the resist layer is not good, when the resist layer is thick, the upper exposure as appropriate, the reaction may not occur on the lower layer, the resist layer after development irregular edges, will affect the accuracy of the image and resolution of the resist layer prone to severe warped and off phenomenon. In order to lower energy aggregation, we must increase the exposure, the upper may be overexposed. Dry developability.
Developing refers dry dry film based on the best working conditions, exposure and image quality obtained after the development is good or bad, that the circuit image should be clear, unexposed parts should be clean and free of residue removal. Left on the plate after the exposure of the resist layer should be smooth and firm. Dry developing resistance to a dry film is the degree of resistance to over-exposure development, the extent to which the developing time can exceed the resistance of the developing tolerance is reflected in the development process. Dry film developing resistance and resistance to developing direct impact on the quality of the production of printed circuit board. Poor developing dry etching will bring difficulties in pattern plating process, the developer will produce poor or non-galvanized coating adhesion defects and poor. Poor development of resistance to dry, in the over-development, will produce dry off infiltration plating and electroplating and other illnesses. The defect will lead to serious PCB scrap.
The so-called resolution refers to the number of lines within a distance of 1mm, dry film resist or spacing that can be formed, the resolution can be absolute size or spacing with lines to indicate the size. The dry film thickness and the resolution of the resist film thickness on polyester. The thicker resist layer, the lower the resolution. When light through photographic negatives of the dry film and the polyester film exposure due to light scattering effect of the polyester film, so that the light emitting side, thus reducing the resolution of the dry film, a polyester film is thicker, the more severe side of the light emitted , the lower the resolution. Usually able to distinguish the minimum line width parallel, an index <0.1mm, two indicators ≤ 0.15mm.
The photopolymerizable layer of the dry film resist, etching solution should be resistant to ferric chloride, ammonium persulfate etching solution, an acid copper chloride etching solution, sulfuric acid - hydrogen peroxide etchant etching. In the etching solution, when the temperature is 50-55 ℃, the dry surface should be no scared, leakage, warped and off phenomenon.
In various copper plating, fluoborate ordinary tin-lead alloy, bright tin fluoborate and lead alloy plating above before plating processing solution at the surface of the membrane should be no scared resist layer after polymerization, seepage plating, warped and off phenomenon. After exposure to dry, after the etching and electroplating through, can be removed in the alkali solution, typically 3-5% sodium hydroxide solution was used, and heated to about 60 ℃, spraying or dipping to mechanically remove, to film The faster the more help to improve production efficiency. The best is to film in the form of flaky peeling, stripping down through the filter to remove debris, so conducive to film the life of the solution, you can also reduce nozzle clogging. Typically 3-5% (by weight) of sodium hydroxide solution, the liquid temperature of 60 soil 10 ℃, an indicator of film time 30-75 seconds to go, two indicators to film time 60-150 seconds, to film After no adhesive residue.
Dry film may become brittle due to volatilization of the solvent during storage may also be due to the influence of the ambient temperature and thermal polymerization, or by a partial flow of the resist to produce the so-called cold flow caused by an uneven thickness, which are seriously affected dry Use of the film. Therefore, stored in a dry environment is good very important. Should be stored in a cool, dry and clean room to prevent stored with chemicals and radioactive substances. Storage conditions: yellow zone, the temperature is below 27 ℃ (5-21 ℃ for the best), relative humidity of 50%. Storage period, counting from the date of delivery is not more than six months, those who pass the test over the storage period can still be used. During storage and transportation process should avoid moisture, heat, mechanical damage and affected by direct sunlight.
In the process of manufacturing operations in order to avoid leakage exposure and heavy exposure, dry film before and after exposure should be obvious color change, which is dry discoloration performance. When used in film as an etching mask apertures required dry film having sufficient flexibility to be able to withstand the developing process, an etching process fluid pressure impact without cracking, which is dry masking properties.
Source://www.seekic.com
