Josee The metallurgical micro etchant you want to use on your microsection is 2% Nital 2ml of Nitric Acid in 98 ml of Ethanol or Methanol This should be swabbed on for no more than 3 seconds - you will have to experiment to get the time right depending on pressure and the mount surface. The Sn/Cu intermetallic will be the white layer next to the copper. Before using the Nital we like to microetch with 50/50 3% hydrogen peroxide/ammonium hydroxide to removed the smeared copper. Hope that helps. Susan Mansilla Robisan Lab --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------