What is Etch factor?

1.Introduction about Etch factor
PCB etching is the process of selectively removing unwanted copper from a PCB’s copper-clad substrates. The two primary methods of removing the copper cladding are mechanical etching and chemical etching. Mechanical etching uses a CNC machining tool with a special cutting tool to remove narrow strips of copper from the boundary of each pad and trace in order to electrically isolate them from the rest of the copper foil. Chemical etching uses a corrosive solution to dissolve away unwanted copper. A protective layer is cut to match the PCB’s Gerber design files and then blocks the applied chemicals maintaining the pads and traces that need to remain intact. We at Hopetimepcb use chemical etching as a normal method due to its precision and efficiency.

2.What is etch factor?
To produce the copper layer features designed by our client, we use a corrosive solution to remove the unwanted copper area, thus leaving behind the desired pattern. But when etching, the corrosive solution will not only etch the unwanted copper, but also etch the walls of the copper features of the design (this means undercut). Figure 4 (below) illustratesthe result. The ratio “D/C” is equal to the etching factor.

Thus, the depth to which the etching occurs is proportional to copper layer thickness (i.e. thicker copper has deeper etching).This occurs because thicker copper requires more time exposed to the chemicals in order to be fully removed;thus, the corrosive chemicals have more time to etch the walls before being washed away.The etch factor for PCBs manufactured by Hopetimepcb depends on whether the layer is inside the board or outside. Etch Factor for outer layers is 1.4, and the Etch Factor for inner layers is 2.5.

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