What is Dry Etching?

Etching is a technique that removes a material using a chemical reaction or physical impact. Etching techniques can be divided into two categories: wet etching and dry etching.

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Usually referred to as photochemical etching (photochemical etching), refers to

Exposure method: According to the graphics, the project will prepare the size of the material-material preparation-material cleaning-drying film or coating drying exposure development drying-etching film removal OK

Screen printing method: open the material clean the plate (stainless steel and other metal materials) screen printing etching stripping OK

Reduces side etch and bumps, improves etch coefficient

Lateral eclipses create burrs. Generally, the longer the printed board stays in the etchant, the more serious the side etch (or use of the old left-right swing etching machine). Undercutting seriously affects the accuracy of the printed wiring. Serious undercutting will make it impossible to make fine wires. When the side etch and the edge decrease, the etch coefficient increases. A high etch coefficient indicates the ability to maintain thin wires, making the etched wires close to the original size. Whether it is tin-lead alloy, tin, tin-nickel alloy or nickel, the excessive etching of the plating etching resist will cause the short circuit of the wire. Because the brim easily breaks down, an electrical bridge is formed between the two points of the wire.

Improve the consistency of etch rate from board to board

In continuous board etching, the more uniform the etching rate, the more uniformly etched the board can be obtained. To meet this requirement, it is necessary to ensure that the etching solution is always maintained in an optimal etching state throughout the entire etching process. This requires the selection of an etching solution that is easy to regenerate and compensate, and has an easy to control etching rate. Processes and equipment that provide constant operating conditions and automatic control of various solution parameters are selected. By controlling the amount of dissolved copper, pH value, solution concentration, temperature, uniformity of solution flow (spraying system or nozzle and nozzle swing) and so on.

Improve uniformity of etch rate across the entire board surface

The etching uniformity of the upper and lower surfaces of the board and the various parts of the board surface is determined by the uniformity of the surface of the board subjected to the etchant flow.

During the etching process, the etching rates of the upper and lower plate surfaces are often inconsistent. Generally, the etching rate of the lower plate surface is higher than that of the upper plate surface. Because the solution accumulates on the upper plate surface, the progress of the etching reaction is weakened. The phenomenon of uneven etching on the upper and lower plates can be solved by adjusting the spraying pressure of the upper and lower nozzles. A common problem of etching printed boards is that it is difficult to etch all the board surfaces clean at the same time. The edge of the board is faster than the center of the board. Using a spray system and swinging the nozzle is an effective measure. Further improvement can be achieved by making the spray pressure at the center of the board and the edge of the board different, and intermittently etching at the front and back of the board to achieve uniform etching of the entire board.

Improved ability to safely handle and etch thin copper foils and laminates

When etching a thin laminate such as the inner layer of a multi-layer board, the board is easily wound on rollers and conveyors, resulting in waste. Therefore, the equipment for etching the inner layer board must ensure that the thin laminate board can be processed smoothly and reliably. Many equipment manufacturers add gears or rollers to the etching machine to prevent this from happening. A better approach is to use additional PTFE-coated wire that swings left and right as a support for the transport of thin laminates. For the etching of thin copper foil (such as 1/2 or 1/4 ounce), it must be guaranteed not to be scratched or scratched. Thin copper foil can not withstand the mechanical disadvantages when etching 1 ounce copper foil, and sometimes more severe vibration may scratch the copper foil.

Reduce pollution

Copper pollution to water is a common problem in printed circuit production, and the use of ammonia-alkali etching solution exacerbates this problem. Because copper is complexed with ammonia, it cannot be easily removed by ion exchange or alkali precipitation. Therefore, the method of the second spraying operation was used to rinse the board with a copper-free additive solution, which greatly reduced the amount of copper discharged. Then, use an air knife to remove the excess solution on the surface of the board before water rinsing, thereby reducing the rinsing burden of copper on copper and etched salts by water.