How to dry screen and steel plate in screen printing?

Screen printing 1, direct plate making method

(1) photographic paste direct plate making method

Methods: A certain thickness of photosensitive paste (usually diazonium salt photosensitive paste) was coated on the stretched screen, and then dried. Then, stick the plate-making negative on it and expose it in the printing machine. After developing, washing and drying, it becomes a screen printing screen.

Process flow: preparation of stretched mesh with photosensitive adhesive-degreasing-drying-coating-drying-exposure-development-drying-correction-final exposure-sealing.

Methods and functions of each part

Degreasing: Degreasing agent is used to remove the grease on the screen printing, so that the photosensitive adhesive and the screen printing are completely bonded together, and it is not easy to peel off the film.

Drying: dry the water to avoid the tension change of the mesh fabric due to excessive temperature, and the temperature should be controlled at 40 ~ 45℃.

Preparation of photosensitive paste: the photosensitizer is mixed with purified water, added into the photosensitive paste, stirred evenly, and used after standing for 8 hours.

Film coating: evenly coat the photosensitive adhesive on the screen by scraping the groove. According to the coating method, it can be divided into automatic coating machine and manual coating, and the coating times can be determined according to the actual situation.

When coating film, the surface of scraper should be coated first to fill the gap between screen yarns and avoid bubbles, and then the printing surface (the surface in contact with PCB) should be coated. At present, the automatic coating machine can increase the film thickness by about 3um each time, so the coating methods of solder mask are: coating the surface of scraper twice-drying-coating the printing surface three times-drying-coating the printing surface three times-drying.

Correct and incorrect explanation of coating method;

A. The correct coating scraper surface and printing surface thickness are appropriate and meet the requirements.

B. Thin coating (printed surface) Disadvantages: poor durability.

C. The coating on the scraper surface is too thick. Disadvantages: Because the photosensitive paste on the scraper surface is too thick, the photosensitive is uneven. After washing with water during development, the ink with rough surface is poured into the film layer, which makes the film layer fall off, resulting in a shorter screen life.

D. The coating on the scraper surface is too thin. Disadvantages: poor durability.

Drying: make the photosensitive paste dry evenly, and avoid the photosensitive paste from being dry outside and wet inside. If the temperature is too high, the service life of the screen will be shortened. The temperature should be kept at 40~45℃ for about 10 minute, and the drying time should be appropriately adjusted according to different film thicknesses.

Exposure: Proper exposure can make the photosensitive paste photosensitive polymerization, and a clear image can be developed through the master.

Factors affecting screen quality:

A. correct exposure energy

B. Exposure and vacuumizing

C. Clean the glass of the exposure machine

Generally, the exposure energy is adjusted by exposure time. In production, the exposure measuring film should be used to determine the correct exposure time of various screens according to the mesh number and film thickness.

How to use measuring parts:

(1) The exposure time estimated in advance is doubled, and then it is developed normally. After development, choose the most effective, that is, the clearest image range, and then multiply the actual exposure time by the marking coefficient on the selected image, which is the better exposure time.

There are five coefficients on the measuring chip, which are 1.0, 0.7, 0.5, 0.33 and 0.25, and each coefficient corresponds to a circular target pattern and point respectively.

(2) If the coefficient of 1.0 seems to be the best coefficient, double the exposure time just now and conduct the exposure test again.

(3) If the coefficient of 0.25 seems to be the best coefficient, the exposure time just now should be reduced by half and the exposure test should be repeated.

(4) If several continuous coefficients are satisfied, the coefficient with smaller upper limit is adopted when drying the dot pattern, that is, the exposure time is shorter, and the coefficient with larger lower limit is adopted when drying the thick line, that is, the exposure time is longer.

⑤ If several continuous coefficients are satisfied, according to the screen type to be dried, the best coefficient is selected by comparing the clearness of the thinnest line or point of the circular target.

In addition, the close adhesion of the negative film, the cleanliness and vacuum of the glass of the exposure machine all have important effects on the quality of the printed matter.

Development: using the water-soluble characteristics of the photosensitive adhesive, the unexposed photosensitive adhesive is washed off with water. The development method has great influence on fine screen printing. Before developing, water must be sprayed to make the photosensitive paste absorb water and swell, and let it stand for 1~2 minutes, and then develop it back and forth in a fan shape with a high-pressure water gun until the image is completely clear.

Note: Don't wash with high-pressure water too close to the screen, generally 0.8~ 1m, otherwise the line will be serrated if the pressure is too high, and some points will be washed away in severe cases.

Drying: dry the water on the screen, the temperature should not be too high, otherwise the screen tension will change, generally 40~45℃.

Modification and inspection: repair and inspect pinholes and some NPTH holes.

Final exposure: further improve the adhesion between photosensitive adhesive and mesh, and increase the service life.

Screen sealing: Fill the excess part of the screen with screen sealing paste to avoid ink leakage during printing.

⑵ photosensitive diaphragm direct plate making method

Process flow: stretching mesh-degreasing-wetting-sticking film-drying-reinforcement-exposure-development-drying-revision-sealing mesh.

way

Photosensitive film, commonly known as water film, is based on a transparent plastic film with a thickness of 0. 1mm, and a layer of photosensitive emulsion with a certain thickness is coated on one side. When in use, the screen is completely soaked, and then the film is attached to the screen, and the film is adsorbed on the screen by capillary action. After drying, tear off the plastic substrate for exposure and development, and finally get the required pattern.

Wetting: Wetting is used to promote the formation of a uniform water film on the screen surface and make the photosensitive film transfer smoothly.

Sticking film: stick the photosensitive film on the surface of the wet screen scraper according to the screen type, and scrape off excess water with the scraper after sticking.

Drying: Generally, it should be dried below 40℃. After drying, tear off the plastic base and let it dry for a few minutes.

Reinforcement: If it is necessary to increase the number of printing plates, a layer of photosensitive paste can be coated on the surface of the scraper after the diaphragm is dried, and then it needs to be dried.

The operation of other parts is consistent with the plate-making method of photosensitive paste.

2. Direct and indirect plate-making methods

way

The methods of direct plate making and indirect plate making are as follows: firstly, when plate making, the photosensitive film coated with photosensitive materials is laid flat on the workbench, and the stretched wrist net frame is laid flat on the film base; Then putting the photosensitive paste into a net frame and applying pressure with a soft scraper; After being fully dried, the plastic film base is removed, and the wrist screen with photosensitive film can be used for printing; And drying to obtain a screen printing plate.

Process flow:

Stretching the net-degreasing-drying-stripping the base-exposure-development-drying-correction-sealing the net.

3. Indirect plate making method

way

The method of indirect plate making is to expose the indirect film, harden it with 1.2% H2O2, develop it in warm water, and dry it to make a strippable graphic negative. In plate making, the film surface of graphic negative is attached to the stretched screen, and the film is attached to the wet screen by extrusion, and then the film base is removed and air-dried to make the screen.

Process flow:

1. Stretching net-degreasing-drying

2. Indirect film exposure hardening development

1 and 2- bonding-blow-drying-revision-screen sealing

1, direct plate making method

(1) photographic paste direct plate making method

Methods: A certain thickness of photosensitive paste (usually diazonium salt photosensitive paste) was coated on the stretched screen, and then dried. Then, stick the plate-making negative on it and expose it in the printing machine. After developing, washing and drying, it becomes a screen printing screen.

Process flow: preparation of stretched mesh with photosensitive adhesive-degreasing-drying-coating-drying-exposure-development-drying-correction-final exposure-sealing.

Methods and functions of each part

Degreasing: Degreasing agent is used to remove the grease on the screen printing, so that the photosensitive adhesive and the screen printing are completely bonded together, and it is not easy to peel off the film.

Drying: dry the water to avoid the tension change of the mesh fabric due to excessive temperature, and the temperature should be controlled at 40 ~ 45℃.

Preparation of photosensitive paste: the photosensitizer is mixed with purified water, added into the photosensitive paste, stirred evenly, and used after standing for 8 hours.

Film coating: evenly coat the photosensitive adhesive on the screen by scraping the groove. According to the coating method, it can be divided into automatic coating machine and manual coating, and the coating times can be determined according to the actual situation.

When coating film, the surface of scraper should be coated first to fill the gap between screen yarns and avoid bubbles, and then the printing surface (the surface in contact with PCB) should be coated. At present, the automatic coating machine can increase the film thickness by about 3um each time, so the coating methods of solder mask are: coating the surface of scraper twice-drying-coating the printing surface three times-drying-coating the printing surface three times-drying.

Correct and incorrect explanation of coating method;

A. The correct coating scraper surface and printing surface thickness are appropriate and meet the requirements.

B. Thin coating (printed surface) Disadvantages: poor durability.

C. The coating on the scraper surface is too thick. Disadvantages: Because the photosensitive paste on the scraper surface is too thick, the photosensitive is uneven. After washing with water during development, the ink with rough surface is poured into the film layer, which makes the film layer fall off, resulting in a shorter screen life.

D. The coating on the scraper surface is too thin. Disadvantages: poor durability.

Drying: make the photosensitive paste dry evenly, and avoid the photosensitive paste from being dry outside and wet inside. If the temperature is too high, the service life of the screen will be shortened. The temperature should be kept at 40~45℃ for about 10 minute, and the drying time should be appropriately adjusted according to different film thicknesses.

Exposure: Appropriate exposure can make the photosensitive paste photosensitive polymerization, and a clear image can be developed through the master.

Factors affecting screen quality:

A. correct exposure energy

B. Exposure and vacuumizing

C. Clean the glass of the exposure machine

Generally, the exposure energy is adjusted by exposure time. In production, the exposure measuring film should be used to determine the correct exposure time of various screens according to the mesh number and film thickness.

How to use measuring parts:

(1) The exposure time estimated in advance is doubled, and then it is developed normally. After development, choose the most effective, that is, the clearest image range, and then multiply the actual exposure time by the marking coefficient on the selected image, which is the better exposure time.

There are five coefficients on the measuring chip, which are 1.0, 0.7, 0.5, 0.33 and 0.25, and each coefficient corresponds to a circular target pattern and point respectively.

(2) If the coefficient of 1.0 seems to be the best coefficient, double the exposure time just now and conduct the exposure test again.

(3) If the coefficient of 0.25 seems to be the best coefficient, the exposure time just now should be reduced by half and the exposure test should be repeated.

(4) If several continuous coefficients are satisfied, the coefficient with smaller upper limit is adopted when drying the dot pattern, that is, the exposure time is shorter, and the coefficient with larger lower limit is adopted when drying the thick line, that is, the exposure time is longer.

⑤ If several continuous coefficients are satisfied, according to the screen type to be dried, the best coefficient is selected by comparing the clearness of the thinnest line or point of the circular target.

In addition, the close adhesion of the negative film, the cleanliness and vacuum of the glass of the exposure machine all have important effects on the quality of the printed matter.

Development: using the water-soluble characteristics of the photosensitive adhesive, the unexposed photosensitive adhesive is washed off with water. The development method has great influence on fine screen printing. Before developing, water must be sprayed to make the photosensitive paste absorb water and swell, and let it stand for 1~2 minutes, and then develop it back and forth in a fan shape with a high-pressure water gun until the image is completely clear.

Note: Don't wash with high-pressure water too close to the screen, generally 0.8~ 1m, otherwise the line will be serrated if the pressure is too high, and some points will be washed away in severe cases.

Drying: dry the water on the screen, the temperature should not be too high, otherwise the screen tension will change, generally 40~45℃.

Modification and inspection: repair and inspect pinholes and some NPTH holes.

Final exposure: further improve the adhesion between photosensitive adhesive and mesh, and increase the service life.

Screen sealing: Fill the excess part of the screen with screen sealing paste to avoid ink leakage during printing.

⑵ photosensitive diaphragm direct plate making method

Process flow: stretching mesh-degreasing-wetting-sticking film-drying-reinforcement-exposure-development-drying-revision-sealing mesh.

way

Photosensitive film, commonly known as water film, is based on a transparent plastic film with a thickness of 0. 1mm, and a layer of photosensitive emulsion with a certain thickness is coated on one side. When in use, the screen is completely soaked, and then the film is attached to the screen, and the film is adsorbed on the screen by capillary action. After drying, tear off the plastic substrate for exposure and development, and finally get the required pattern.

Wetting: Wetting is used to promote the formation of a uniform water film on the screen surface and make the photosensitive film transfer smoothly.

Sticking film: stick the photosensitive film on the surface of the wet screen scraper according to the screen type, and scrape off excess water with the scraper after sticking.

Drying: Generally, it should be dried below 40℃. After drying, tear off the plastic base and let it dry for a few minutes.

Reinforcement: If it is necessary to increase the number of printing plates, a layer of photosensitive paste can be coated on the surface of the scraper after the diaphragm is dried, and then it needs to be dried.

The operation of other parts is consistent with the plate-making method of photosensitive paste.

2. Direct and indirect plate-making methods

way

The methods of direct plate making and indirect plate making are as follows: firstly, when plate making, the photosensitive film coated with photosensitive materials is laid flat on the workbench, and the stretched wrist net frame is laid flat on the film base; Then putting the photosensitive paste into a net frame and applying pressure with a soft scraper; After being fully dried, the plastic film base is removed, and the wrist screen with photosensitive film can be used for printing; And drying to obtain a screen printing plate.

Process flow:

Stretching the net-degreasing-drying-stripping the base-exposure-development-drying-correction-sealing the net.

3. Indirect plate making method

way

The method of indirect plate making is to expose the indirect film, harden it with 1.2% H2O2, develop it in warm water, and dry it to make a strippable graphic negative. In plate making, the film surface of graphic negative is attached to the stretched screen, and the film is attached to the wet screen by extrusion, and then the film base is removed and air-dried to make the screen.

Process flow:

1. Stretching net-degreasing-drying

2. Indirect film exposure hardening development

1 and 2- bonding-blow-drying-revision-screen sealing