The process of chemical metal etching begins with creating a design using CAD or Adobe Illustrator. However, this is not the only step that involves computer calculations. Once the design is complete, the thickness of the metal is determined, as well as the number of parts that can be placed on one sheet to reduce production costs. In addition, the tolerance of the parts depends on the size of the part, which also affects the thickness of the sheet.
Acid Etching , metals must be thoroughly cleaned before processing. Each piece of metal goes through a process of scrubbing, cleaning and purifying using water pressure and mild solvents. This process removes oil, impurities and tiny particles. This is to provide a smooth and clean surface when the photoresist film is applied to the metal surface to ensure a strong adhesion.
Lamination is the process of applying a photoresist film on a metal sheet. The metal sheet moves between rollers that coat and evenly apply the lamination. To avoid overexposure of the metal sheet, the process is carried out in a room illuminated with yellow light to prevent UV exposure. By punching holes on the edges of the metal sheet, proper alignment of the metal sheet is provided. Bubbles in the lamination coating are avoided by vacuum sealing the metal sheet, resulting in a flat laminate layer.
During the photoresist processing stage of photochemical metal etching, the image of the CAD or Adobe Illustrator design is transferred to the photoresist layer on the metal plate. This is done by clamping the design to the top and bottom sides of the metal plate. Once the image is applied to the metal plate, it is exposed to ultraviolet light to permanently fix the image.
During the UV exposure process, the transparent areas of the photoresist layer allow the UV light to pass through, causing the photoresist to harden and become solid. In contrast, the black areas of the photoresist layer remain soft and are not affected by the UV light. This process forms a pattern that will guide the etching process, where the hardened areas will remain and the soft areas will be etched away.
After the photoresist processing stage, the metal sheet is transferred to a developer machine, which uses an alkaline solution, usually sodium carbonate or potassium carbonate. This solution will wash away the soft photoresist film, exposing the part to be etched.
As a result, the soft photoresist is removed, while the hardened photoresist remains, corresponding to the areas that need to be etched. In the resulting pattern, the hardened areas appear in blue, while the soft areas appear in gray. The areas not protected by the hardened photoresist represent the exposed metal parts that will be removed during the etching process.
During the etching phase of photochemical etching, the developed metal sheet is placed on a conveyor and passed through a machine that injects an etchant onto the sheet. The etchant dissolves the exposed metal, leaving protected areas on the sheet.
In most photochemical processes, ferric chloride is used as the etchant because it is safe to use and recyclable. For copper and its alloys, cupric chloride is used as the etchant.
The etching process must be precisely timed and controlled depending on the type of metal being etched, as some metals require longer etching times than others. Accurate monitoring and control are essential to ensure the success of the photochemical etching process.
After the etching process is complete, the remaining adhesive film on the metal piece is removed by applying an adhesive film remover. This process removes any remaining adhesive film from the metal surface.
Once the stripping process is complete, the final metal part is revealed.
