In printed circuit board manufacturing, printed circuit boards made with Multiwire board and Additive Process technology do not have to be etched. The printed circuit boards made by subtraction process need etching process to form conductive graphics. Under the protection of the graphic mask, the etching removes the copper that is not needed on the copper-clad substrate by chemical reaction to form the required circuit pattern. As the mask of the graphic part of the circuit, it uses graphic transfer or screen printing to make the photoresist of the organic compound system or the surface of a metal anticorrosion layer to cover the circuit pattern to form an anticorrosion layer. Therefore etching process is an indispensable step in the manufacture of printed circuit boards. With the rapid development of microelectronic technology and the wide application of large scale integrated circuits and large scale integrated circuits, the width and distance of wire on printed circuit board are becoming smaller and smaller, and the density and precision of wiring are higher and higher. The precision and tolerance of etch are higher and more strict, and the quality of etching is better. The bad is directly related to the quality of the printed board. Therefore, to fully understand and master the corrosion mechanism of copper in various types of etchant, the choice of better etching solutions, methods and equipment is the necessary condition to meet the requirements of etching. In particular, the function and etching method of etching solution is the key to ensure the size accuracy of circuit graphics.
There are two kinds of resist layer on the circuit diagram, one is the organic film anticorrosion layer, the other is the metal coating anticorrosion layer. When choosing the etching solution, it is necessary to consider the anticorrosion protective layer suitable for the type of etchant. The etching speed is fast and can be easily controlled, the etching coefficient is large and the side corrosion is small; the etching solution can run continuously and regenerate, the amount of copper dissolving is large, the solution life is long, and the stability is good: the wide range of working conditions and the better washability: It should also consider the good working environment, easy recovery and reuse of copper, and easy treatment of sewage.
In the initial stage of printed circuit board manufacturing, the anticorrosion layer used on a single panel is a liquid photoinduced anticorrosion layer (bone glue, polyvinyl alcohol, etc.) with ink as an anticorrosion layer, and the etchant used is acid trichloride and other acid etchant. When making printed circuit boards with metallized holes, gold, tin, lead, tin and other metal resist layers are used. The type of etching solution suitable for metal resist is different from that of resist metal. Gold coating is used as an anticorrosive coating. It can be used as an etching solution or an alkaline etching solution. Tin lead alloy and tin coating are suitable for alkaline etching solution. At present, the corrosion resistant layers of tin lead alloy and tin are widely used as etchant of ammonia alkaline copper chloride, and the organic etch etching can be used in a series of hydrogen sulphate and nitric acid etchant. In general, etching rate can be continuously etched. The regeneration of the solution can be carried out automatically, and the etched copper can be recycled.
In the early etching process, the etching is carried out by immersion and agitation sputtering. The production efficiency is low and the etched product has poor precision. Later, the equipment of the horizontal jet is developed, which can be etched continuously, speed up, production efficiency and the precision of circuit graphics are greatly improved.