PCB board etching process, which uses traditional chemical etching processes to corrode unprotected areas. Kind of like digging a trench, a viable but inefficient method.
In the etching process, it is also divided into a positive film process and a negative film process. The positive film process uses a fixed tin to protect the circuit, and the negative film process uses a dry film or a wet film to protect the circuit. The edges of lines or pads are misshapen with traditional etching methods. Every time the line is increased by 0.0254mm, the edge will be inclined to a certain extent. To ensure adequate spacing, the wire gap is always measured at the closest point of each pre-set wire.
It takes more time to etch the ounce of copper in order to create a larger gap in the void of the wire. This is called the etch factor, and without the manufacturer providing a clear list of minimum gaps per ounce of copper, learn the manufacturer’s etch factor. It is very important to calculate the minimum capacity per ounce of copper. The etch factor also affects the manufacturer’s ring hole. The traditional ring hole size is 0.0762mm imaging + 0.0762mm drilling + 0.0762 stacking, for a total of 0.2286. Etch, or etch factor, is one of the four main terms that specify a process grade.
In order to prevent the protective layer from falling off and meet the process spacing requirements of chemical etching, traditional etching stipulates that the minimum spacing between wires should not be less than 0.127mm. Considering the phenomenon of internal corrosion and undercut during the etching process, the width of the wire should be increased. This value is determined by the thickness of the same layer. The thicker the copper layer, the longer it takes to etch the copper between the wires and under the protective coating. Above, there are two data that must be considered for chemical etching: the etch factor – the number of copper etched per ounce; and the minimum gap or pitch width per ounce of copper.