source:Other information release time:2022-12-10 Hits: Popular:PCB Assembly company
Movable type printing is one of the four great inventions in ancient China. Bi Sheng of the Northern Song Dynasty took the lead in developing clay movable type. As the core of modern electronic industry, printed circuit board is also named after "printing". What is the origin of the two inventions?
Bi Sheng thought that the wood and stone engraving printing was inconvenient at that time, so he considered making a mold for each character and movable type printing. Because clay movable type is as fragile as ceramics, its application and promotion are greatly limited. Then Mongolian cavalry spread China's four great inventions to Europe. Under this influence, Gutenberg, a German in the 15th century, invented type printing.
Soon, Germans found themselves faced with a problem: how to print pictures? Unlike the Chinese people's preference for boards and stones, the Germans chose copper plates. Engraving copper plate requires copper plate etching technology, which involves a series of fine chemical reactions. The first is to prepare polymer photoresist film. It is found that the colloid prepared by mixing water soluble polymer materials such as animal glue and resin with dichromate solution has such properties. The exposed part is soluble in water, while the unexposed part is insoluble in water. This is because dichromate is a photosensitive material. After strong light irradiation, hexavalent chromium ion precipitation will become trivalent chromium ion that is easily soluble in water. In this way, chromate precipitation generated by reaction with polymer materials will be soluble in water after exposure. Then, the photoresist is coated on the copper plate under low light conditions, dried, covered with the negative made of the original, and then printed in the sun. In this way, the copper plate surface is covered with a protective layer designed according to the original. Finally, the copper plate is immersed in ferric chloride solution in the dark place for corrosion. Based on the principle of oxidation-reduction reaction between copper metal and ferric ion solution, the part without protective layer on the copper plate after exposure is slowly corroded and "eaten" by ferric chloride solution. After a day or two, take out the copper plate, wash and dry it, and then you can get a printing master with fine strokes and nice convexity and concavity.
This corrosion engraving technology is so successful that modern printed circuit boards also use a similar corrosion technology, that is, the insulating substrate is coated with a metal coating, coated with photosensitive materials, printed according to the circuit diagram, corroded, coated with a layer of protective film, and finally punched on the circuit board for welding electronic components. The circuit board made in this way has fine structure, high reliability and is convenient for mass production. With the progress of technology, now the printed circuit board can usually achieve an eight layer structure, fully automatic drilling and welding. The holes between layers of multilayer structure play a role in connecting electronic circuits, so extremely complex circuits can be realized on a board with a small area.
Since wood and stone engraving printing was still popular in China until the end of the Qing Dynasty, although type printing and handwritten ink printing methods were introduced later, China soon jumped into the era of laser typesetting, so it did not accumulate enough experience in copperplate printing. Copperplate printing is the precursor of printed circuit board technology and even chip manufacturing technology. In the field of electronic industry, China should make great efforts.
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