Home made PCB by the method of screen printing

Home made PCB by the method of screen printing


Manufacturing printed circuits by the method of screen printing The technique used in printed circuits industry, is the screen, This way you can get good quality prints at very low cost. This printing system allows multiple copies of the same design, making it ideal for mass production. Although it is still a manual process is one of the most used, allowing quality and presentation work necessary for commercialization. The frame It is a rectangular wooden frame built with battens of 3 x 3 inches, which supports a fine silk, very warm and wrinkle free. We use a frame of 120 threads in which we all three arts are gonna be. The printed circuit board, solder mask and mask components. Applying the emulsion In a room where light does not come mix 9 parts emulsion to 1 part bichromate or developer to obtain a uniform mixture. The mixture is spread along the silk, using an emulsifier. It takes three or four layers of emulsion; The first layer is applied to the rear of the frame, excess emulsion is collected Apply the second coat on the front We apply the third coat And we apply the last layer, reversing the direction of the frame. The emulsion should be applied evenly on the silk, bearing in mind that no gaps or bubbles Uncoated. Then we dry the emulsion using a hair dryer to minimize drying time. Remember that the emulsion is light sensitive and will gradually harden. After drying the emulsion, place the rack on a table revealed We put on the back of the frame, acetates, with printed designs. Remember to place the overhead on the opposite side, which will see the finished PCB. Fixed with a transparent adhesive tape. Now we turn to the frame we placed a thin foam We put a glass silk covering the whole We put weight on top to avoid a separation of acetates, silk, and glass. Developing of the emulsion. Exposed to ultra violet light, the overhead for 13 minutes. Keeping the weight Remove the glass and foam and removed the acetates Immediately wash the frame on both sides with pressurized water. After a few seconds is observed as silk reveals the drawing of the PCB, as the emulsion drops in areas where the light did not come because of the coverage of acetate. The developer is the same, according to the design. After processing, silk, proceed to dry it with a hair dryer for 10 minutes. The silk is ready to print as many cards we want. Printing clues about Bakelite Place the rack on a table preferably glass, fixing it with a press hinge allows the frame to lift easily, without moving from his position. Bakelite placed just below the drawing of the circuit board and adjusted with an adhesive. We put some stops, so that the print does not run Bakelite site. We got the frame We use UV ink off the silk, making a path in the part before the drawing. Spread the ink, then draw with the spatula (squeegee or blade), printed circuit design on the surface of the card. Notice how it should be printing. It should be flawless, or spotting shifts that may impair the form. Oven-dried In the manufacture of printed inks are used that dry when exposed to ultraviolet rays. Bakelite should be left at least 10 minutes printed in the oven Revealed Card. Once dry the ink comes to bathe the card into ferric chloride. You can make a bowl, using a small pump, which keeps moving ferric chloride. The corrosive action of ferric chloride acts on surfaces that are not covered by the ink, thus obtaining the printed circuit. When excess copper has been removed, remove the card from ferric chloride, to prevent over correction. Wash the card, first with water, thereby removing ferric chloride. Then immersed in caustic soda dissolved in water for a minute and brush until all the paint has fallen. Subsequently washed again with water to remove the caustic soda. We dry well cards. Perforations Holes are drilled all of the card, using a drill or a mototool tree. It should have bits of different sizes, as the terminals of the components have different diameters. With a steel wool pad, we removed the residues to make the perforations. Then clean the card with a napkin. Printing the antisolder Antisolder mask is applied in the same way that the tracks. We place the caps do not run the bakelite We got the frame, We apply a generous amount of solder UV paint, Spread the paint on silk, And several times we draw strength to give a good protective coating. This painting protects the copper tracks, rust and possible short circuits, besides giving a good presentation. The solder paint is drying UV rays, so the card should bake for about 10 minutes. Mask printing components. To print the mask components, the card is placed on the opposite side of the tracks and adjust it with tape. Note that the holes must match the card, with drawings of the components. We put some stops, so that the print does not run the bakelite of your site. We got the frame, We apply the white UV ink by the party off the silk, Spread the ink, then draw with a spatula or standards. Notice how it should be printing. Must be perfect, as this face indicates the correct position of each component. The paint used in industry to make the mask component is also drying UV rays, so the card should bake for 10 minutes. On the side of the tracks, apply a mixture of rosin and thinner, which prevents oxidation of donuts, and also gives a brilliant finish to the board. Now we have the finished printed circuit board, ready to assemble. We hope that this tutorial is useful for everyone. success!

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