What problems must be paid attention to in the etching process？

What problems must be paid attention to in the etching process？

1. Improve the uniformity of the etch rate across the board surface

The etching uniformity of the upper and lower sides of the board and each part of the board is determined by the uniformity of the etchant flow on the board surface. During the etching process, the etching rates of the upper and lower plate surfaces are often inconsistent. Generally speaking, the etching rate of the lower surface is higher than that of the upper surface. Because of the accumulation of solution on the upper plate surface, the progress of the etching reaction is weakened. The uneven etching of the upper and lower plates can be solved by adjusting the spray pressure of the upper and lower nozzles. A common problem with etched printed boards is that it is difficult to etch the entire board at the same time. The edges of the board are etched faster than the center of the board. Using a spray system and oscillating the nozzle is an effective measure. A further improvement can be achieved by making the spray pressure at the center of the board and the edge of the board different, and intermittent etching of the front edge of the board and the back end of the board to achieve the uniformity of etching on the entire board surface.

2. Reduce side erosion and protruding edge, improve etching coefficient

Side erosion produces sharp edges. Usually the longer the printed board is in the etching solution, (or use the old-fashioned swing etching machine) the more serious the side etching. Side etching seriously affects the accuracy of printed wires, and severe side etching will make it impossible to make fine wires. When the side etching and protrusion are reduced, the etching coefficient increases. A high etching coefficient indicates the ability to maintain thin wires, so that the etched wires are close to the original size. Whether it is a tin-lead alloy, tin, tin-nickel alloy or nickel, the excessive protrusion of the etch resist will cause a short circuit of the wire. Because the ledge breaks easily, an electrical bridge is formed between the two points of the wire.

3. Improve board-to-board etch rate consistency

In continuous board etching, the more consistent the etching rate, the more uniformly etched boards can be obtained. To achieve this requirement, it is necessary to ensure that the etching solution is always kept in the best etching state during the whole etching process. This requires the selection of an etching solution that is easy to regenerate and compensate, and the etching rate is easy to control. Select processes and equipment that provide constant operating conditions and automatic control of various solution parameters. It is realized by controlling the amount of dissolved copper, PH value, solution concentration, temperature, uniformity of solution flow (spraying system or nozzle and nozzle swing).