Etching is the process of material being removed from material’s surface. The etching process sometimes involves using liquid chemicals to take off the substrate material before they are used in fabrication. Alternative methods include plasma etching and laser etching.
The etching process is one of the major steps in the final processing of printed circuit boards (PCBs). This process removes excess copper so as to reveal the desired circuit patterns. In the PCB etching process, all copper is removed except the circuitry that is protected by the tin plating that was applied during the previous treatment in PCB manufacturing. The tin is then stripped and the copper is cleaned and the newly prepared circuit is ready to move on to the next step in manufacturing.
Take a closer look at the 3 different processes for PCB etching below.
Chemical Etching for PCB Manufacturing
Chemical etching is used mostly on metals and is a manufacturing method that is a subtractive process that utilizes chemical baths. During the process, metal is removed in order to produce metal parts in desired shape and thickness.
The process was said to have developed during the Renaissance as an alternative to engraving on metal. This method involves bathing the material in a corrosive chemical that reacts with the area that needs to be cut. The chemical reaction causes the solid material to be dissolved.
Laser Etching for PCB Manufacturing
This process enables the use of precise, computer-controlled hardware to craft high quality PCBs. The laser etching process uses a high power laser to carve the trace lines on a PCB substrate. The computer can carve the design on the PCB by doing away with the unwanted copper traces. Etching a PCB in this way minimizes the number of steps and it also eliminates the use of inks, acids or toxic chemicals.
During the process, the energy contained in the laser beam changes the makeup of the material, thereby releasing it from the PCB either by evaporation or by flaking off. Laser etching of PCBs may lower production costs because of the reduction in number of products needed to complete the process as well as less overall production time.
Plasma Etching for PCB Manufacturing
Plasma etching was introduced to circuit manufacturing around the mid 1960s and more widely in the early 1970s. The process was created as a way to help reduce liquid waste disposal in manufacturing and achieve selectivities that were difficult to obtain with wet chemistry.
Plasma etching, the selective etching of material by reaction with chemically active radicals, involves a high-speed stream of glow discharge (plasma) of an appropriate gas mixture being pointed at a material. Plasma etching is dry and clean, and offers process simplification and improved dimensional tolerances compared to existing wet, chemical etching processes.
Plasma etching is capable of controlled and precise etching at very small scales. This particular process also lessens the occurances of contaminated vias and solvent absorption.