Etching process of PCB external circuit

- Apr 13, 2017-

In the process of printed circuit processing, ammonia etching is a delicate and complex chemical reaction process. As long as the process to achieve a pass, can carry out continuous production, but the key is the boot after must maintain continuous working state, not suitable for intermittent production.

The etching process is very dependent on the state of the equipment, so it is necessary to keep the equipment in good condition at all times.

At present, no matter what the etching liquid, must use the high-pressure spray, and in order to get a neat side line and high quality etching effect, structure and methods on the selection of spray nozzle must be more stringent.

The way of making excellent side effect, research theory, design methods and equipment structure outside have different, and these theories are often different people. However, one of the most basic principles has been recognized and confirmed by chemical mechanism analysis, that is, as soon as possible to make the surface of the metal constantly exposed to fresh etching solution.

In ammonia etching, assuming that all parameters are constant, the rate of etching will be determined primarily by ammonia (NH3) in the etching solution. Therefore, the main purpose of the interaction between the fresh solution and the etching surface is two: to remove the newly produced copper ions and the ammonia (NH3) needed for the reaction.

In the traditional knowledge of the printed circuit industry, especially the suppliers of printed circuit materials are recognized, and the experience has confirmed that the ammonia etching solution in the price of copper ion content is lower, the faster the reaction speed.

A large number of quality issues related to the etching facets are concentrated on the etched portions of the upper plate, and these problems are attributed to the effect of the etchant. It is very important to understand this, because the gel is deposited on the surface of the copper, on the one hand, it will affect the jet force, on the other hand, it will hinder the addition of fresh etching liquid, so that the etching rate is reduced. Because of the formation and accumulation of colloidal hardening material, the etching degree substrate following graph is different, first enter the substrate due to the accumulation has not yet formed, etching speed, it is easy to be completely etched or caused by corrosion, and then into the substrate has been formed due to the accumulation, and slow down the etching speed.

In the continuous plate etching, the higher the etching rate is, the more uniform the plate can be obtained. To achieve this requirement, it is necessary to ensure that the etching solution remains in the best etching state throughout the etching process. It is necessary to choose easy regeneration and compensation, and the etching rate and easy to control the etching solution, and selection can provide constant operating conditions and can process and equipment automatic control of solution parameters, by controlling the amount of dissolved copper, pH, concentration, temperature and flow rate of solution to achieve uniformity of etching rate consistency.

A common problem with etching is that it is difficult to make all surfaces etched at the same time. Because the edge position of the substrate is etched faster than the central part, it is difficult to make all the etching clean at the same time. It is an effective measure to use spray system and spray nozzle. To further improve, through the different pressure on the center of the plate and the edge of the spray, as well as the front plate and the back end of the plate using intermittent etching method to achieve the entire plate etching uniformity.

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