Answer: 1. The circuit board surface includes a foil coated substrate and a pre copper plated substrate after hole metallization. To ensure a firm adhesion between the dry film and the substrate surface, it is required that the substrate surface be free of oxide layers, oil stains, fingerprints, and other dirt, drilling burrs, and rough coatings. To increase the contact area between the dry film and the substrate surface, it is also required that the substrate have a micro rough surface. To meet the above two requirements, the substrate must be carefully treated before applying the film. The treatment methods can be summarized into two categories: mechanical cleaning and chemical cleaning.

　　2. The same principle applies to resistance welding. Before resistance welding, grinding the plate is to remove some oxidation layers, oil stains, fingerprints, and other dirt from the plate surface. In order to increase the contact area between the resistance welding ink and the plate surface and make it more secure, it is also required that the plate surface have a micro rough surface (just like repairing a car's tire, the tire must be ground to a rough surface to better bond with the adhesive). If grinding is not carried out before the circuit or solder mask, and there are some oxide layers, oil stains, etc. on the surface of the board to be coated or printed for solder mask, it will directly separate the solder mask and the circuit mask from the board surface, forming an isolation. In the subsequent process, the film in this area will fall off and peel off