Printed circuit board production

Printed circuit boards are a big part of electronics production, and they are also the technologies that best represent the level of electronics enthusiasts. Printed circuit boards are referred to as printed boards for short, and factory production is very different from amateur production. The factory generally designs the printed board diagram according to the circuit schematic provided by the customer, and then makes the printed board through photolithography and other techniques, and then forms the finished product by soldering, printing, etc., and requires a series of equipment. In the traditional amateur production, printed boards can only be produced using a copper-plated and corrosive solution. In recent years, new types of technologies such as universal test boards and photosensitive circuit boards have been introduced to liberate vast numbers of electronics enthusiasts and electronic product developers. In addition to the popularity of PCs, designing circuits with CAD software and automatically generating PCBs (printed circuit boards) are not difficult.

It is even more convenient to print on the film directly with the photosensitive circuit board. First, design the printed circuit board diagram on the basis of the circuit schematic diagram on the paper, the correct connection among various components is important, but also pay attention to the size of the components, arrangement position, interference, etc.. After the design is completed, you must repeatedly proofread the schematic diagram , And find the physical location of components to their respective positions, in the adjustment of hole spacing, alignment and so on. Pay attention to the positive and negative, and sometimes accidentally design the opposite side. You can write the original image on carbon paper once. Then you have what you need on the back of the paper. The method for making a printed circuit board is to cut out the designed 1:1 drawings, attach the transparent adhesive to the copper surface of the single-faced copper-clad board, and then use the punch to knock on the place where the hole needs to be drilled to form a recessed part. Pit, so that drilling with a small electric drill will not slip. Then use the self-made small electric drill (recovery machine motor modification) to drill holes, tear off the drawings after all finished, and paint the lines directly with a brush. Since there is already a hole, it is not difficult to draw, just remember that several holes are It's all right together.

Generally uncomplicated circuits use this method to make the circuit board extremely fast. If the circuit is complex, a copy of carbon paper can be placed between the drawing and the copper-clad board, then the printed board can be traced again and the hole-drilled area can be traced deeper. Use a brush to paint the line. If there is no paint, trace lines can be traced with a better quality marker, or traced with a correction fluid, but the circuit board for correcting the fluid profile is not very beautiful, and the width of the circuit needs to be corrected after drying. Nail polish can also be used, dried faster and easier to use than correction fluid. During the tracing, pay attention to the distance between the lines, and surround the holes to form a circle to facilitate welding. It takes a long time for the paint to dry. After the paint is dry, it can be put into the corrosive solution. The corrosive solution is generally made of ferric chloride and water. The ferric chloride is a yellowish solid and it is easy to absorb the moisture in the air. So Should be sealed and stored. When ferric chloride solution is used, 40% of ferric chloride and 60% of water are generally used. Of course, more ferric chloride is used, or warm water (not hot water to prevent paint shedding) can make the reaction faster. . Note that ferric chloride has a certain degree of corrosivity. It is best not to get it on the skin or on clothes. The reaction vessel is made of cheap plastic pots, and the circuit board is good enough.

Corrosion starts from the edge. When the unpainted copper foil is corroded, the circuit board should be taken out in time to prevent the paint from eroding away the useful circuit. Rinse with clean water at this time, by the way to scrape off the paint with bamboo and other objects, if not easy to scrape, just use hot water to rinse it. Then wipe dry and polish it with sandpaper to reveal shiny copper foil. A printed circuit board is ready. In order to save the results, the polished circuit board is usually coated with rosin solution, which can both help the welding and prevent oxidation.