Membrane switch is an electronic component, which is a part of instrumentation. It is a product that integrates functionality and decoration realized by screen printing process. It is widely used in machinery, automation, instrumentation, medical instruments, etc. industry. Screen printing is a kind of printing method. It uses screen technology to print text, patterns or backgrounds on the surface of the substrate. Screen printing is a key link in the manufacture of membrane switches.
Screen printing refers to the use of screen as the plate base, and the method of photosensitive plate making to make a screen printing plate with graphics. Screen printing consists of five elements: screen printing plate, squeegee, ink, Printing tables and substrates. Printing is carried out by using the basic principle that the mesh of the screen printing plate can pass through the ink, and the mesh of the non-graphic part cannot pass through the ink. When printing, pour ink on one end of the screen printing plate, apply a certain pressure to the ink part on the screen printing plate with a scraper, and at the same time move towards the other end of the screen printing plate at a constant speed, the ink is scraped during the movement process. Extruded from the mesh in the graphic section onto the substrate.
The application range of screen printing technology is very wide, in addition to water and air (including other liquids and gases), any kind of object can be used as a substrate. So it is one of the basic methods of special printing technology.
Photosensitive plate-making method has the advantages of high speed, high precision and high printing endurance, and has become the most widely used silk-screen plate-making method at present. Choose the screen frame of the appropriate size of the printed matter, there are two kinds of wood and aluminum alloy. The wood screen frame is suitable for manual stretching. You must first nail the edge of the screen with a net gun, and then use the net pliers to stretch the opposite side. One side of the screen, until the four sides are stretched, the aluminum alloy is suitable for the stretching machine to stretch the net, use the stretcher to stretch and then brush the stretch glue, the glue can dry, brush the photosensitive glue, and choose oil-based photosensitive glue for ink printing. Water-based photosensitive glue is selected for pulp printing. Photosensitive glue generally has photosensitizer. After adding it according to the proportion, stir it with a wooden stick and let it stand until there are no bubbles. After brushing and drying, the direct method is to directly coat the photosensitive adhesive on the screen, and then print the plate to make a plate. Preparing the screen is the first and most important step in the screen printing process. If the screen plate is not selected properly, good printing effect cannot be made. Screen printing workers must choose the correct screen system and equipment to reproduce the original color of the manuscript. Screen printing is widely used and can meet different quality requirements. Modern stencil systems can produce a variety of different artwork, but the right choice must be made.
1. Process flow before screen printing:
1.1. Screen printing pretreatment: The purpose of screen printing pretreatment is to ensure the bonding fastness of the screen and the photosensitive film, mainly for degreasing. Before gluing, it is necessary to clean the wire mesh with a net cleaning agent. The net cleaning agent is alkaline. The commonly used NaOH solution is 20%, and neutral or weak washing powder can also be used. . Allow the solution to fully react with the soil, then rinse thoroughly with water.
1.2. Coating photosensitive adhesive: Coating photosensitive adhesive requires uniform coating, consistent thickness and smooth surface. There are two methods of coating: machine coating method and manual coating method. The machine coating method is to use a glue coating machine for coating. Yes, manual coating generally uses a squeegee mode for coating.
1.3. Drying: The glue coating is carried out in a liquid state. Generally, the sensitivity of photosensitive glue is relatively low in the liquid stage, and the sensitivity increases with the drying of the coated film. The exposure hardening of most photoresist needs to be done in the solid state, so as to have the best strength, so drying is essential. Drying strives to be fast, sufficient, clean and does not change the properties of the photoresist. Insufficient drying, the plate film has poor water and solvent resistance; if the drying temperature is too high, the photosensitive film will be thermally hardened. Therefore, the ideal drying method is to dry with constant temperature hot air, and the temperature is controlled at 40 plus or minus 5 degrees Celsius. The glue coating and drying should be carried out under a yellow light.
1.4. Printing: If the photosensitive film is not completely dry, it should be printed as soon as possible. The negative of the printing should be a positive image. When printing, the film surface of the negative should be closely exposed to the printing surface of the screen. The exposure time depends on the properties of the photosensitive solution, the light source, the lamp distance and other factors.
1.5. Development: After exposure, the film on the photosensitive film that is not visible to light is completely dissolved, and a screen printing plate is immediately made. The exposed printing plate is immersed in water and rinsed with a water gun to form a picture. After the text, it is dried and then exposed again to increase the fastness of the film and improve the printing resistance.
1.6. Drying: After the development is completed, the plate film should be dried immediately with cold or hot air (greater than 45 degrees Celsius), or it can be dried in a drying box.
1.7. Trimming: The quality of the screen printing plate after drying should be checked. If the screen printing plate is defective, it should be repaired.
2. The production process of screen printing screen
2.1. During plate making, the photosensitive emulsion and photosensitive liquid are poured into the glue solution according to the amount of 10:1, and then slowly stirred to mix the two liquids, and then evenly coated on the mesh cloth.
2.2. After the photosensitive emulsion is adjusted, slightly tilt the photosensitive emulsion to flow onto the mesh cloth, scrape it up and hang it all the way to the top of the mesh cloth, apply it evenly on the mesh cloth, and apply the photosensitive emulsion in the same way. The emulsion is applied once on each side of the frame and then blown dry with hot air from a hair dryer.
2.3. After the screen plate is dried, press immediately for photosensitive printing to avoid all exposure. The lighting can be 200W indoor lighting, or two 20W fluorescent lamps. Place the screen flat under the light, and then put the photosensitive film upwards. Put it on the screen, and then press the two iron clips on the glass cover on the left and right sides. The distance from the light to the screen is 20 cm to 30 cm, and the photosensitive time is about 8-10 minutes.
2.4. For the screen printing screen after photosensitive, rinse with water or wipe with a sponge. When flushing, the water pressure should be moderate and not too high. Be careful not to break the mesh. The black part of the original positive film on the screen should be washed with water. , while the white transparent part forms a hard film and sticks to the mesh until the pattern stops clearly.
2.5. After the screen printing screen is washed out with water, use a dry cloth to cover the upper and lower sides of the screen to absorb the water, and let the screen dry naturally or dry it with a hair dryer.
2.6. After the screen printing screen is done, place the object to be printed flat under the screen, align the position, and then pour the ink on the inner frame of the screen, hold the rubber scraper in the right hand, and use a temperature of 50 degrees Celsius to 70 degrees Celsius. Slope, scrape it down hard, pay attention to the uniform force, and the pattern will be clearly printed on what you need.
Through the above content, you will have a general understanding of the screen printing process and production process of membrane switches. Shenzhen pinban Technology Co., Ltd. adheres to: "Small products, big stage, based on local, tailor-made" and "Let quality become a The business philosophy of "a kind of mark", strictly implement production management in accordance with ISO9001, and strictly control product quality. Efforts to build the first brand of membrane switch panels, to provide users with the most satisfactory products and the most thoughtful service.
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