There are mainly two methods of metal etching based on the contact form between the workpiece and the solution: spray etching and immersion etching. The principles for selecting the etching method are as follows:

1. Production Volume: Spray etching offers high efficiency, speed, and precision, well-suited for mass production and easy to automate. However, it requires significant investment in equipment and is not suitable for etching of non-uniform or large workpieces. Immersion etching has lower equipment investment, is convenient, and has a wide range of applications, but is not suitable for large-scale production. It is slower than spray etching, has lower production yields, and is difficult to automate.

2. Workpiece Shape and Size: Due to equipment limitations, spray etching is difficult to perform on large workpieces, whereas immersion etching is not affected by the size of the workpiece. Complex shapes of workpieces can lead to uneven spraying during the spray etching process, impacting the normal etching procedure. However, immersion etching, by submerging the workpiece entirely in the etching solution, ensures that all parts of the irregular workpiece continuously replace old solution with new, thereby maintaining normal etching.

For small to medium-sized flat workpieces, spray etching is superior to immersion etching in terms of efficiency and precision. Therefore, spray etching should be prioritized for flat workpieces with large batches and moderate sizes.