I have noticed numerous posting on the best microsection etchant to use. There are merits and disadvantages in the etchants mentioned to date. I specifically would like to discuss the sodium dichromate and the ammonium hydroxide & hydrogen peroxide. The ammonium hydorxide & hydrogen peroxide is 1 of the more unstable copper etchants that does an excellent job of microetching. The most attractive attribute of this etchant is in the hands of a less skilled or naive person, the etchant will not overetch the surface to the severity of a chromate etchant. (Not say that only less skilled people use this etchant) I define 'instability' as variable etch quality over a short period of time (hours). At Merix, we make enough etchant to microetch the work at hand and discard the remainder. The soduim dichromate etchant is a stable etchant (last for months) that is more agressive than the ammonium hydroxide & hydrogen peroxide etchant. The aggressive nature of this etchant requires greater skill by the user to prevent the surface from being overetched which hides cracks and separations. I used the sodium dichromate etchant at my prior employer for 15 years and was able to detect separations and cracks. While I worked at this employer, we published papers on our ability to detect separations and our concerns that separation was being shipped. This leads me to believe the type of etchant is not so important as the user of the etchant. One of my favorite BC cartoons is a caption that "If you don't know what it does; don't screw with it". The skill and knowledge of the user is as impotant as the etchant itself. IPC-MS-810 lists the types of etchants that are recommended for etching of microsections. Whatever etchant is chosen for use, the key is to create the desired etch quality of the surface to make wise decisions on quality. The primary qualities are a faint definition of the electroless line, strike platre line (as applicable), and the copper grain boundaries. When these boundaries become wide and/or dark in appearance, sensitivity is lost for detecting separation and cracks. Lastly, the primary reason that the sodium dicromate etchant popularity declined is the the chrome content and EPA rulings on chrome. The issue over chrome was a key reason that the etchant was dropped from the test methods and military use. Happy microsectioning, Randy Reed Merix Corporation *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************