Copper(i) Monitor for Etching Solutions
Original Publication Date: 1988-Apr-01
Included in the Prior Art Database: 2005-Feb-15
Cupric chloride etches are frequently used to etch copper from circuit boards, often in the presence of a resist acting to mask those areas not to be etched. The copper is etched according to the following mechanism: Cu0 + Cu2+ T 2Cu+ where Cu0 is the solid metal to be etched and Cu2+ and Cu+ are species in solution. Cu+ normally is an unstable species. However, in the presence of large amounts of chloride, as in these etching solutions, it is relatively stable. Thus, the concentration of Cu+ will build up during the etching process. Furthermore, the buildup of Cu+ concentration in the etching solution will decrease the activity of the etch. Generally, this situation is dealt with by periodically adding an oxidizing agent such as H2O2 to the solution to oxidize the Cu+ back to Cu2+ .